JP3306965B2 - Vibration type 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 a vibration type angular velocity sensor suitable for detecting a turning direction and a posture of a vehicle or the like.

[0002]

2. Description of the Related Art In general, as a vibration type angular velocity sensor used for detecting a turning direction of a vehicle or the like, a sensor using a high-speed rotating body or a sensor using an optical fiber is well known. It has become expensive.

For this reason, recently, using a piezoelectric material or the like,
2. Description of the Related Art A vibration type angular velocity sensor that detects an output proportional to an angular velocity using a Coriolis force is increasingly used.

For example, US Pat. No. 4,699,00
A torsional vibration type angular velocity sensor using a semiconductor process technology as shown in the specification of Japanese Patent Application Laid-Open Publication No. 6-106 is proposed.

This torsional vibration type angular velocity sensor excites a vibrating piece supported on a substrate via a support beam in the Y-axis direction 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 around the X-axis by the Coriolis force. Then, the angular velocity is detected by detecting a separation dimension (displacement of the detection piece) between the detection piece and the fixed electrode.

[0006]

In the angular velocity sensor according to the prior art described above, the center of rotation of the detecting 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 detecting 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 reed is horizontal with respect to the substrate, when the detection is performed in a gas, the vibrating reed can be rotated at a constant period due to the viscous resistance of air. Disappears. As a result, the Coriolis force acting on the detection piece fluctuates, so that 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, and the present invention provides a vibration type angular velocity sensor capable of detecting angular velocity with high accuracy by vibrating a vibrating piece without viscous resistance of air. It is intended to provide.

[0009]

In order to solve the above-mentioned problems, the structure adopted by the invention of claim 1 is a structure which is straight in a horizontal direction.
A substrate having an intersecting X-axis and a Y-axis, a plurality of vibrating bar fixing portions provided on the surface of the substrate, a plurality of support beams having a base end fixed to each of the vibrating bar fixing portions; A vibrating reed supported between the plurality of vibrating reed fixing portions via a beam in a state separated from the substrate; and a positive and negative center of rotation about a central axis (Z axis) of the vibrating reed perpendicular to the substrate . an excitation means for rotating vibration by electrostatic attraction in the reverse direction, the water to the substrate
Angular velocity acts around the flat X axis, turning the Y axis
Vertical direction of the vibrating reed when rotating about the center (Z axis
And a displacement amount detecting means for detecting the displacement amount in the direction (1) . The invention according to claim 2 is characterized in that
A substrate having an intersecting X-axis and a Y-axis; first and second vibrating bar fixing portions provided on the surface of the substrate; and a base end fixed to the first and second vibrating bar fixing portions. A first and a second support beam, a vibrator element supported between the first and second vibrator element fixing portions via the first and second support beams while being separated from the substrate, and the substrate An exciting means for rotating and vibrating by electrostatic attraction in forward and reverse directions about a center axis (Z axis) of the vibrating reed perpendicular to the substrate;
The angular velocity acts on the horizontal X axis,
And a displacement detecting means for detecting a displacement of the vibrating reed in a vertical direction (Z-axis direction) when the vibrating piece rotates about an axis .

Further, the invention according to claim 3 is orthogonal to the horizontal direction.
A substrate having an X-axis and a Y-axis, a plurality of vibrating bar fixing portions provided on the surface of the substrate, a plurality of arc-shaped support beams having a base end fixed to each of the vibrating bar fixing portions, A vibrating reed supported between the plurality of vibrating reed fixing portions via the respective support beams while being separated from the substrate; and a central axis (Z axis) of the vibrating reed perpendicular to the substrate. positive as the pivot center, and excitation means for rotating vibrate in opposite directions, horizontal to the substrate
Angular velocity acts around the X axis, and the Y axis rotates around
Vertical direction of the vibrating reed when rotating (Z axis direction
And the displacement amount detecting means for detecting the displacement amount in the direction (1) . The invention according to claim 4 is characterized in that X
A substrate having an axis and a Y-axis; first and second vibrating bar fixing portions provided on the surface of the substrate; and an arc-shaped base end fixed to the first and second vibrating bar fixing portions. first and second support beams, and supported resonator element via the first and second support beams state spaced from the substrate between the first and second vibrating bars fixed portion, wherein Perpendicular to substrate
A positive central axis of the vibrating piece (Z-axis) as a rotation center, and exciting means for rotating vibrate in opposite directions, horizontal to the substrate
And a displacement amount detecting means for detecting a displacement amount of the vibrating piece in the vertical direction (Z-axis direction) when the vibrating piece rotates about the Y axis . Furthermore, the invention of claim 5 resides in that the substrate, the resonator element and the support beam are formed of silicon.

[0011]

According to the above construction, in the first aspect of the present invention, the vibrating reed is prevented from being displaced in the vertical direction by the plurality of support beams, and an electrostatic attraction is applied by the excitation means to apply a force to the substrate.
The vibrating reed is rotated about the center axis (Z axis) of the vibrating reed perpendicular to the revolving piece. In this state, the water to the substrate throughout the sensor
When an angular velocity is applied about the flat X axis , Coriolis force acts on the vibrating piece, and the Y axis, which is horizontal to the substrate, is
As a result, the resonator element rotates and is displaced in the vertical direction (Z-axis direction) . The angular velocity applied to the entire sensor can be detected by detecting the amount of displacement of the vibrating reed by the displacement amount detecting means. Further, in the invention of claim 2, first, while preventing the resonator element is displaced with respect to the vertical direction by the second supporting beams, by the action of electrostatic attraction by the excitation means, group
The vibrating reed is rotated about the center axis (Z axis) of the vibrating reed perpendicular to the plate . In this state, the X axis horizontal to the substrate
When the angular velocity is applied as the center, the horizontal Y axis
The resonator element rotates around the center of rotation, and displaces in the vertical direction.
You. Therefore, the angular velocity applied to the entire sensor can be detected by detecting the amount of displacement of the resonator element in the vertical direction (Z-axis direction) by the displacement amount detecting means.

According to the third aspect of the invention, while the vibrating reed is prevented from being displaced in the vertical direction by the plurality of arcuate supporting beams, the center axis (Z-axis) of the vibrating reed is perpendicular to the substrate by the excitation means. ) Is rotated about the center of rotation. In this state, when <br/> angular velocity is applied around the horizontal X-axis with respect to the substrate throughout the sensor, Coriolis force acts on the vibrating element, group
Resonator element as the pivot about a horizontal axis Y plate rotated
Then, it is displaced in the vertical direction (Z-axis direction) . Then, by detecting the displacement amount of the vibrating reed by the displacement amount detecting means,
The angular velocity applied to the entire sensor can be detected. In the invention according to claim 4, the vibrating reed is prevented from being displaced in the vertical direction by the arcuate first and second support beams, and the central axis of the vibrating reed is perpendicular to the substrate by the excitation means. (Z axis) is rotated about the rotation center. Based in this state
When an angular velocity is applied around the X axis that is horizontal to the plate,
The vibrating bar rotates around the Y axis that is horizontal to the substrate
Then, it is displaced in the vertical direction (Z-axis direction). Therefore, the angular velocity applied to the entire sensor can be detected by detecting the vertical displacement of the resonator element by the displacement detector. According to the fifth aspect of the present invention, since the vibrating reed and the supporting beam are formed of silicon, a semiconductor processing technique such as an etching technique can be used, and the vibrating reed and the supporting beam can be easily formed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a substrate made of a single-crystal silicon material.
8 are provided, and the vibrating bar fixing portions 5 and 5, the rotating electrodes 6 and 6, the vibrating bar 3 and the like are provided via the oxide film 2 serving as an insulating layer. For convenience, the left and right directions of the paper with respect to the rotation center O shown in FIG. 1 are the X axis, the upper and lower directions are the Y axis, and the upper and lower directions of the paper shown in FIG. 2 are the Z axis. .

Reference numeral 3 denotes a vibrating reed provided apart from the substrate 1, and the vibrating reed 3 is formed in a disc shape by polysilicon, and its center is a rotation center O. As shown in FIG. The support arms 3A and 3B are formed 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, and the base end side is fixed to the vibrating bar fixing portions 5 and 5, and the distal end side is the supporting arm of the vibrating bar 3. Parts 3A, 3B
Respectively. Each of the support beams 4 is shown in FIG.
As shown in the figure, the supporting arm 3A of the vibrating reed 3 located on the upper side with respect to the Y axis is located on the lower vibrating reed fixing part 5, and the supporting arm 3B of the vibrating reed 3 located on the lower side is located on the upper side. Each is fixed to one piece fixing portion 5. The vibrating reed 3, each supporting beam 4, and each vibrating reed fixing portion 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 disposed on both sides of the vibrating piece 3 in the X-axis direction. The surface facing the vibrating reed 3 is formed in an arc shape. A sine wave (or pulse wave) having a predetermined excitation frequency is input from the oscillation circuit 7 between each of the rotating electrodes 6 and the vibrating bar fixing portion 5. Note that the predetermined excitation frequency substantially matches the resonance frequency of the vibrating reed 3 set by the elastic modulus obtained from the length, width, and thickness of each of the support beams 4.

Reference numerals 8, 8 denote fixed electrodes for detection as displacement detecting means formed by diffusing phosphorus into the substrate 1. Each of the fixed electrodes for detection 8 has a semicircular shape as shown in FIG. , 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 probe and the resonator element 3 are detected as capacitances C1 and C2. Each of the detecting portions 8A, 8A is formed at a position corresponding to the vibrating piece 3, and the combined size of the respective detecting portions 8A is formed so as to be substantially the same size as the circle of the vibrating piece 3. I have.

The vibration type angular velocity sensor according to the present embodiment is constructed as described above. Next, a method of manufacturing the same will be described with reference to FIGS.

First, in the step of forming the oxide film 2 shown in FIG. 6, each fixed electrode 8 for detection is patterned on the substrate 1 made of a single crystal silicon material, and phosphorus is diffused to form each fixed electrode 8 for detection as a diffusion layer. Is formed, an oxide film 2 is formed on the upper surface side of the substrate 1 by using, for example, a thermal oxidation method.

Next, in the step of forming the sacrifice layer 9 shown in FIG. 7, the sacrifice 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, each supporting beam 4, each vibrating piece fixing portion 5 and each rotating electrode 6 shown in FIG.
Patterning is performed using IE (Reactive Ion Etching). At this time, in order to improve conductivity, impurities such as phosphorus or boron are diffused in the polysilicon.

Finally, in the step of removing the sacrifice layer 9 shown in FIG. 9, the sacrifice layer 9 and the oxide film 2 at that portion are etched with an HF aqueous solution or the like, so that the resonator element 3 and each support beam 4 and the substrate 1 are removed.
And form a space.

Next, the detection operation of the vibration type angular velocity sensor according to the present 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 bar fixing portions 5 and 5, the rotating electrodes 6 and the supporting beams 4 During this period, an electrostatic attraction is generated according to a predetermined excitation frequency, and each of the support beams 4 is sequentially pulled as shown by arrow B on the rotating electrodes 6 and 6. Thereby, the support arms 3A, 3B of the vibrating reed 3
Are repeated in the forward and reverse directions in the direction of arrow A, and the vibrating reed 3 performs rotational vibration about the rotational center O. At this time, it is assumed that the rotation center O does not move not only in the X and Y axis directions but also in the Z axis direction.

Here, as shown in FIG. 2, when an angular velocity C about the X axis as the rotation center is applied to the entire sensor, the force on the Y axis as shown by arrow D in FIG. The force acts on the resonator element 3 as a force . As a result, the distances d1 and d2 between the detecting portion 8A of each fixed electrode 8 for detection and the vibrating reed 3 are displaced.
And the capacitance C between the detection portion 8A of each fixed electrode 8 for detection
1 and C2 also change. Then, the capacitances C1, C2
Is detected from the extraction portion 8C of each detection fixed electrode 8 and the vibrating bar fixing portion 5 and subjected to signal processing by a differential circuit or the like (not shown) connected to the outside, so that the angular velocity applied in the direction of arrow C is reduced. A corresponding output can be obtained.

However, according to the present embodiment, the vibrating piece 3 does not displace in the Z-axis direction when the vibrating piece 3 is rotated and vibrated. It can be performed at a constant cycle. Thus, the Coriolis force acting on the vibrating reed 3 in the direction indicated by the arrow D about the Y axis as the rotation center with respect to the angular velocity C applied to the X axis as the rotation center is eliminated, and the angular velocity C is detected with high accuracy. be able to.

Further, since the structure is simple, and it can be formed by using a semiconductor processing technique such as silicon etching in the manufacturing process, a large number of vibration angular velocity sensors can be manufactured at the same time. Inexpensive vibration type angular velocity sensor can be manufactured.

In the above-described embodiment, the vibrating reed 3 is formed in a disk shape. However, the shape is not limited to a circle, but may be a quadrangle, a pentagon, or the like. The shape of the detecting portion 8A of the fixed electrode 8 for detection
It is not necessary to have the same shape as that described above, and what is necessary is just to detect the distance between the resonator element 3 and the substrate 1. Further, since this separation dimension also detects the separation distance of the vibrating reed 3 that rotates about the Y axis as the rotation center, only one of the separation dimensions may be detected.

Further, the exciting means is provided with the rotating electrodes 6 and 6 so as to generate an electrostatic attraction between the vibrating piece 3 and each of the rotating electrodes 6 so as to rotate and vibrate. The present invention is not limited to this, and a piezoelectric element or a resistor may be used for the support beam, and the vibrating piece 3 may be rotated and vibrated using the thermal expansion effect of the support beam.

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

[0032]

As described above in detail, according to the first aspect of the present invention, the vibrating reed supported on the substrate via the plurality of supporting beams is moved by the central axis (Z axis) by the electrostatic attraction of the exciting means. ) positive as a rotation center, in the opposite direction by rotating vibration, and about the X axis
And the angular velocity acts to rotate about the Y axis as the center of rotation.
Because it was configured to detect the displacement amount detecting means for displacement in the vertical direction (Z axis direction) of the Kino resonator element, while preventing displacement with respect to the vertical direction by a plurality of support beams, rotating vibration excitation of the vibrating element be able to. For this reason, the vibrating reed can be rotated and vibrated at a constant period without the influence of the viscous resistance of the gas, and the angular velocity applied to the entire sensor can be detected with high accuracy as the displacement of the vibrating reed. Claim 2
According to the invention, since the resonator element is supported at the center of the first and second resonator element fixing portions via the first and second support beams, the displacement in the vertical direction is achieved by the first and second support beams. In addition, the vibration of the vibrating piece can be rotated and vibrated at the center of the first and second vibrating piece fixing portions by the electrostatic attraction of the exciting means while preventing the influence of the viscous resistance of the gas.

According to the third aspect of the present invention, the vibrating piece supported on the substrate via the plurality of arc-shaped support beams is forwardly and reversely rotated about the center axis (Z axis) by the excitation means. In the direction of rotation , the angular velocity acts around the X axis
The vertical direction of the vibrating bar when rotating around the Y axis
Since the displacement amount in the (Z-axis direction) is detected by the displacement amount detecting means, the vibration of the resonator element can be rotated and vibrated while the displacement in the vertical direction is prevented by the plurality of support beams. For this reason, the vibrating reed can be rotated and vibrated at a constant period without the influence of the viscous resistance of the gas, and the angular velocity applied to the entire sensor can be detected with high accuracy as the displacement of the vibrating reed. According to the fourth aspect of the present invention, since the vibrating piece is supported at the center of the first and second vibrating piece fixing portions via the first and second arc-shaped support beams, the first and second vibrating pieces are supported. The first and second support beams prevent displacement in the vertical direction.
Excitation of the vibrating reed can be rotationally vibrated at the center of the second vibrating reed fixing portion, and the influence of the viscous resistance of the gas can be eliminated. Furthermore, according to the fifth aspect of the present invention, since the substrate, the supporting beam and the vibrating piece are formed of silicon, the vibration type angular velocity sensor can be manufactured in a simple process by a silicon etching technique or the like, and the productivity is improved. And cost reduction.

[Brief description of the 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 a direction indicated by arrows III-III in FIG.

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

FIG. 5 is a cross-sectional view as seen from a direction indicated by arrows VV in FIG. 4;

FIG. 6 is a cross-sectional view showing a process for 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 reed, a support beam, a vibrating reed fixing portion, and a rotating electrode.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Oxide film 3 Vibrating piece 4 Support beam 6 Rotating electrode 7 Oscillation circuit 8 Detection fixed electrode O Rotation center

Claims (5)

(57) [Claims] A substrate having an X axis and a Y axis orthogonal to a horizontal direction, a plurality of vibrating bar fixing portions provided on the surface of the substrate, and a base end side of each of the vibrating bar fixing portions. a fixed plurality of support beams, and supported resonator element in a state of being separated from the substrate between the plurality of vibrating piece fixing portion through a respective support beam, said
Exciting means for rotating and vibrating in the forward and reverse directions by electrostatic attraction about a center axis (Z axis) of the resonator element perpendicular to the substrate as a rotation center, and about an X axis horizontal to the substrate.
When angular velocity acts and turns around the Y axis,
And a displacement amount detecting means for detecting a displacement amount of the vibrating piece in a vertical direction (Z-axis direction) . 2. A substrate having an X axis and a Y axis orthogonal to a horizontal direction, first and second vibrating piece fixing portions provided on a surface of the substrate, and the first and second vibrating piece fixing portions. A first and a second support beam, the base ends of which are fixed to the vibrating bar fixing portion, and the substrate between the first and second vibrating bar fixing portions via the first and second supporting beams. A vibrating piece supported in a spaced state, and a center axis (Z axis) of the vibrating piece perpendicular to the substrate
Excitation means for rotating and vibrating in the forward and reverse directions by electrostatic attraction about a rotation center, and an X-axis which is horizontal to the substrate.
Angular velocity acts as a center, and the Y axis rotates around the center of rotation.
A vibration type angular velocity sensor comprising: a displacement amount detecting means for detecting a displacement amount of the vibrating piece in a vertical direction (Z-axis direction) when moving . 3. A substrate having an X axis and a Y axis orthogonal to a horizontal direction, a plurality of vibrating bar fixing portions provided on a surface of the substrate, and a base end side of each of the vibrating bar fixing portions. A plurality of fixed arc-shaped support beams, a vibrating piece supported in a state separated from the substrate between the plurality of vibrating piece fixing portions via the respective support beams, and a plurality of the vibrating pieces perpendicular to the substrate. The center axis of the resonator element (Z
( Excitation means ) for rotating and vibrating in the forward and reverse directions about a rotation center, and an angular velocity about the X axis which is horizontal to the substrate.
And a displacement amount detecting means for detecting a displacement amount of the vibrating piece in a vertical direction (Z-axis direction) when the vibrating piece rotates about the Y axis. Type angular velocity sensor. 4. A substrate having an X axis and a Y axis orthogonal to a horizontal direction, first and second vibrating piece fixing portions provided on a surface of the substrate, and the first and second vibrating piece fixing portions. First and second arc-shaped support beams whose base ends are fixed to the vibrating piece fixing portion of
The first and second support beams are provided via the first and second support beams.
A vibrating reed supported between the vibrating reed fixing portions of the vibrating reed in a state separated from the substrate, and pivoting in the forward and reverse directions about a central axis (Z axis) of the resonating reed perpendicular to the substrate. Exciting means for vibrating, and centering on the X axis horizontal to the substrate
Angular velocity acts to rotate around the Y axis
And a displacement amount detecting means for detecting a displacement amount of the vibrating piece in a vertical direction (Z-axis direction) . 5. The vibration type angular velocity sensor according to claim 1, wherein the substrate, the resonator element and the support beam are formed of silicon.