JPH06241816A - Vibration type angular velocity sensor - Google Patents

Abstract

PURPOSE:To detect angular velocity accurately by eliminating air viscosity resistance which is operated on the vibration piece of a vibration-type angular velocity sensor. CONSTITUTION:A vibration piece 3 is fixed to a vibration piece fixing part 5 via a support beam 4 on a circular arc on a substrate 1 consisting of silicon material. An electrode 6 for rotation for rotating and vibrating in reference to the center axis of the vibration piece 3 is provided in X axis of the vibration piece 3. Further, a fixed electrode 8 for detecting the separation dimension between the vibration piece 3 and the substrate 1 is formed at the lower side of the vibration piece 3, thus achieving rotation in reference to the Y axis with the coriolis force operated on the vibration piece 3 when an angular force rotating in reference to the X axis is applied to the entire sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type angular velocity sensor suitable for use in detecting the turning direction, posture, etc. of a vehicle or the like.

[0002]

2. Description of the Related Art Generally, as a vibrating angular velocity sensor used for detecting the turning direction of a vehicle or the like, those utilizing a high-speed rotating body and those utilizing an optical fiber are well known. It has become expensive.

Therefore, recently, using a piezoelectric material or the like,
A vibration-type angular velocity sensor that detects an output proportional to the angular velocity using the Coriolis force has come into wide use.

For example, US Pat. No. 4,699,00
There has been proposed a torsional vibration type angular velocity sensor using a semiconductor process technology as shown in the specification of No. 6.

This torsional vibration type angular velocity sensor excites a vibrating element supported on a substrate in the Y-axis direction through a support beam so as to rotate about the Y-axis as a rotation axis, and the angular velocity in the Z-axis direction. Is applied, the detection piece supported in the vibrating piece in the X-axis direction via the support beam rotates about the X-axis by the Coriolis force. Then, the angular velocity is detected by detecting the distance (displacement of the detection piece) between the detection piece and the fixed electrode.

[0006]

By the way, in the above-mentioned conventional angular velocity sensor, the center of rotation of the detection piece and the vibrating piece in the direction of rotation is the X axis and the Y axis, and the center of rotation is relative to the substrate. It is horizontal. This allows
The detection piece and the vibrating piece are displaced in the Z-axis direction (vertical direction) with respect to the substrate, and there is a problem that the structure of the electrode arrangement becomes very complicated.

Further, since the rotation axis of the vibrating piece is horizontal with respect to the substrate, when performing detection in a gas, the vibrating piece can be rotated in a constant cycle by viscous resistance of air. Disappear. This causes a problem that the Coriolis force acting on the detection piece fluctuates, the displacement of the detection piece cannot be accurately detected, and the angular velocity cannot be detected with high accuracy.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention provides a vibrating angular velocity sensor capable of performing highly accurate detection of angular velocity by vibrating the vibrating piece without viscous resistance of air. It is intended to be provided.

[0009]

In order to solve the above-mentioned problems, the structure adopted by the present invention is a vibrating piece supported on a substrate through a supporting beam, and a center axis of the vibrating piece is a center of rotation. As a result, it is composed of an exciting means for rotating and vibrating in the forward and reverse directions and a displacement amount detecting means for detecting the displacement amount of the vibrating piece in the vertical direction.

Further, it is desirable that the substrate, the resonator element and the support beam are made of silicon.

[0011]

With the above structure, when angular velocity is applied to the entire sensor in a state where the vibrating element is rotated about the central axis of the vibrating element by the excitation means, Coriolis force acts on the vibrating element and the vibrating element vertically moves. Displace in the direction. Then, the displacement amount detecting means detects the displacement amount of the vibrating piece to detect the angular velocity applied to the entire sensor.

Further, by forming the vibrating piece and the supporting beam with silicon, semiconductor processing technology such as etching technology can be utilized, and the vibrating piece and the supporting beam can be easily formed.

[0013]

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

In the figure, reference numeral 1 denotes a substrate made of a single crystal silicon material, on which a fixed electrode for detection 8, which will be described later,
8 is formed, and the resonator element fixing portions 5 and 5, the rotating electrodes 6 and 6, the resonator element 3 and the like are provided via the oxide film 2 serving as an insulating layer. Note that, for convenience, the left and right directions of the paper surface with respect to the rotation center O shown in FIG. 1 are the X axes, the up and down directions are the Y axes, and the up and down directions of the paper surface shown in FIG. 2 are the Z axes. .

Reference numeral 3 denotes a vibrating piece provided apart from the substrate 1. The vibrating piece 3 is formed of polysilicon into a disk shape, and its center serves as a rotation center O. As shown in FIG. Support arm portions 3A and 3B are formed so as to project upward and downward (Y-axis direction).

Reference numerals 4 and 4 denote support beams. Each of the support beams 4 is formed in a semicircular arc shape, the base end side is fixed to the vibrating piece fixing portions 5 and 5, and the tip side is the supporting arm of the vibrating piece 3. Parts 3A, 3B
It is fixed to each. Further, each of the support beams 4 is shown in FIG.
As shown in FIG. 7, the supporting arm portion 3A of the vibrating piece 3 located on the upper side with respect to the Y axis is on the lower vibrating piece fixing portion 5, and the supporting arm portion 3B of the lower vibrating piece 3 is on the upper side vibration. They are fixed to the one-side fixing portions 5, respectively. The vibrating piece 3, the supporting beams 4, and the vibrating piece fixing portions 5 are integrally formed of polysilicon.

Reference numerals 6 and 6 denote a pair of rotating electrodes as excitation means formed on the substrate 1. The rotating electrodes 6 are arranged on both sides of the vibrating piece 3 in the X-axis direction. A surface facing the vibrating piece 3 is formed in an arc shape. A sine wave (or a pulse wave) having a predetermined excitation frequency is input from the oscillation circuit 7 between each of the rotating electrodes 6 and the vibrating piece fixing portion 5. The predetermined excitation frequency is substantially the same as the resonance frequency of the vibrating piece 3 set by the elastic modulus obtained from the length, width, and thickness of each support beam 4.

Reference numerals 8 and 8 denote fixed electrodes for detection as displacement amount detecting means formed by diffusing phosphorus on the substrate 1. Each fixed electrode for detection 8 has a semicircular shape as shown in FIG. Detection unit 8A, a pattern 8B for deriving a detection signal from the detection unit 8A, and an extraction unit 8C for deriving a detection signal from the pattern 8B to the outside.
The distances d1 and d2 (see FIG. 3) between the vibrating element 3 and the vibrating element 3 are detected as capacitances C1 and C2. Further, the respective detecting portions 8A, 8A are formed at positions corresponding to the vibrating piece 3, and the combined size of the respective detecting portions 8A is formed to be substantially the same as the circular shape of the vibrating piece 3. There is.

The vibration type angular velocity sensor according to the present embodiment is constructed as described above. Next, a method for manufacturing the same will be described with reference to FIGS. 6 to 9 by taking the case of using single crystal silicon as an example.

First, in the step of forming the oxide film 2 shown in FIG. 6, the fixed electrodes 8 for detection are patterned on the substrate 1 made of a single crystal silicon material, and phosphorus is diffused to form fixed electrodes 8 for detection as diffusion layers. After forming, the oxide film 2 is formed on the upper surface side of the substrate 1 by using a means such as a thermal oxidation method.

Next, in the step of forming the sacrificial layer 9 shown in FIG. 7, the sacrificial layer 9 made of phosphorus glass having a thickness d1 (d1 = d2) is formed by the CVD method.

Further, in the step of forming the vibrating piece 3, the supporting beams 4, the vibrating piece fixing portions 5 and the rotating electrodes 6 shown in FIG. 8, after forming polysilicon by the CVD method, R
Patterning is performed using IE (reactive ion etching). At this time, in order to improve the conductivity, impurities such as phosphorus or boron are diffused in the polysilicon.

Finally, in the step of removing the sacrificial layer 9 shown in FIG. 9, the sacrificial layer 9 and the oxide film 2 on the sacrificial layer 9 are etched with an HF aqueous solution or the like to form the vibrating piece 3 and each supporting beam 4 and the substrate 1.
Form a space with.

Next, the detection operation of the vibration type angular velocity sensor according to this embodiment will be described.

First, when a sine wave having a predetermined excitation frequency is input from the oscillation circuit 7 between the rotating electrodes 6 and 6 and the vibrating piece fixing portions 5 and 5, the rotating electrodes 6 and the supporting beams 4 are connected to each other. During this period, an electrostatic attractive force is generated according to a predetermined excitation frequency, and each of the support beams 4 is sequentially pulled by the rotating electrodes 6 and 6 as shown by arrow B. Thereby, the support arms 3A and 3B of the vibrating piece 3 are
Is repeatedly rotated forward and backward in the direction of arrow A, and the vibrating reed 3 vibrates about the center of rotation O. At this time, the rotation center O does not move not only in the X and Y axis directions but also in the Z axis direction.

As shown in FIG. 2, when the angular velocity C about the X axis is applied to the entire sensor, the Coriolis force twists the force on the Y axis as shown by the arrow D in FIG. Acts on the vibrating piece 3. As a result, the distances d1 and d2 between the detection portion 8A of each detection fixed electrode 8 and the vibrating piece 3 are displaced, and accordingly the vibration piece 3 and the detection portion 8A of each detection fixed electrode 8 are separated. Capacitance between C1 and C2
Also changes. Then, the changes in the electrostatic capacitances C1 and C2 are detected from the extraction portion 8C of each detection fixed electrode 8 and the vibrating piece fixing portion 5, and signal processing is performed by a differential circuit or the like (not shown) connected to the outside, An output corresponding to the angular velocity applied in the arrow C direction can be obtained.

However, according to this embodiment, when the vibrating reed 3 is in the rotational vibration state, the vibrating reed 3 is not displaced in the Z-axis direction. It can be performed at regular intervals. This eliminates the fluctuation of the Coriolis force acting in the direction of the arrow D with the Y axis of the vibrating piece 3 as the rotation center relative to the angular velocity C applied with the X axis as the rotation center, and the angular velocity C is detected with high accuracy. be able to.

Further, since the structure is simple and can be formed by utilizing a semiconductor processing technique such as etching of silicon in the manufacturing process, a large number of vibration type angular velocity sensors can be manufactured at the same time, which is small and manufacturing cost. It is possible to manufacture an inexpensive vibration type angular velocity sensor.

In the above embodiment, the vibrating piece 3 is formed in a disc shape, but the shape is not limited to a circular shape, but may be a quadrangle, a pentagon, or the like, and is formed on the substrate 1 so as to face the vibrating piece 3. The shape of the detection portion 8A of the fixed detection electrode 8 is also the vibrating piece 3
It is not necessary to use the same shape as the above, but the point is to detect the distance between the vibrating element 3 and the substrate 1. Further, this separation dimension also detects the separation distance of the vibrating piece 3 that rotates about the Y axis, so that only one separation dimension may be detected.

Further, the exciting means is provided with the rotating electrodes 6 and 6, and an electrostatic attractive force is generated between the vibrating piece 3 and each of the rotating electrodes 6 to rotate and vibrate. Not limited to this, a piezoelectric element or a resistor may be used for the support beam, and the vibrating piece 3 may be rotationally vibrated by using the thermal expansion effect of the support beam.

Further, in the displacement amount detecting means of the vibrating piece 3, the distance between the substrate 1 and the vibrating piece 3 is also detected as a change in the electrostatic capacitance between the fixed electrodes 8 for detection and the vibrating piece 3. , Support beams 4 and 4 or support arms 3A and 3B of the vibrating piece 3
The twist of the vibrating piece 3 may be detected by providing a piezoresistive element, a piezoelectric element, or the like.

[0032]

As described above in detail, according to the present invention, the vibrating element supported on the substrate via the supporting beam is rotated in the forward and reverse directions about the central axis of the vibrating element by the exciting means. Since the displacement amount detecting means detects the amount of vertical displacement of the vibrating piece by vibrating, the vibration of the vibrating piece is set to rotational vibration to eliminate the effect of viscous resistance of gas and vibrate at a constant cycle. The piece can be rotationally vibrated, and the angular velocity applied to the entire sensor can be detected as the displacement of the vibrating piece with high accuracy.

Further, by forming the substrate, the support beam and the vibrating piece from silicon, the vibrating angular velocity sensor can be manufactured in a simple process by a silicon etching technique or the like, which improves productivity and reduces cost. Can be achieved.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view as seen from the direction of arrows II-II in FIG.

FIG. 3 is a cross-sectional view as seen from the direction of arrows III-III in FIG.

4 is a front view of the substrate showing a state in which the resonator element and the like in FIG. 1 are removed.

5 is a cross-sectional view as seen from the direction of arrows VV in FIG.

FIG. 6 is a cross-sectional view showing a process of forming a fixed electrode for detection and an oxide film.

FIG. 7 is a cross-sectional view showing a step of forming a sacrificial layer.

FIG. 8 is a cross-sectional view showing a process of forming a vibrating piece, a supporting beam, a vibrating piece fixing portion, and a rotating electrode.

FIG. 9 is a cross-sectional view showing a sacrifice layer removing step.

[Explanation of symbols]

 1 substrate 2 oxide film 3 vibrating piece 4 support beam 6 rotation electrode 7 oscillation circuit 8 fixed electrode for detection O rotation center

Claims (2)

[Claims] 1. A vibrating piece supported on a substrate via a support beam, an exciting means for rotationally vibrating the vibrating piece in forward and reverse directions about a central axis of the vibrating piece, and a vertical direction of the vibrating piece. A vibration type angular velocity sensor including a displacement amount detecting means for detecting the displacement amount of the. 2. The vibration type angular velocity sensor according to claim 1, wherein the substrate, the vibrating element and the supporting beam are made of silicon.