JP2001133268A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor enabling detecting Coriolis force caused by an angular velocity with no need for enlarging the structure and no influence of external acceleration. SOLUTION: A mass part 20 having a dead weight part 22 drive-vibrating to a X direction, is linked to a base 10 through a detecting joist 25 and can be vibrated to a Y direction of an operating direction of Coriolis force by this the detecting joist 25 when applying an angular velocity Ω. A detecting part 30, which comprises an electrode deadweight 31 and detecting electrode 32 placed so as to be faced with a space between a comb-teeth electrode 24 and the electrode 32 itself, is linked to the base 10 through an electrode joist 35. The mass part 20 and detecting part 30 having a same resonance frequency, can be similarly displaced to in the Y direction in the case of external acceleration applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass section provided with a weight section capable of driving and oscillating in a predetermined direction, and a detection section disposed opposite to the mass section at an interval so that an angular velocity is generated. The present invention relates to an angular velocity sensor that changes an interval between opposing portions of a mass unit and a detection unit by Coriolis force acting on the mass unit, and detects an angular velocity based on a change amount of the interval.

[0002]

2. Description of the Related Art An angular velocity sensor of this type is generally shown in FIG. This is the frame J1
And a mass portion J5 having a weight portion (vibrator) J3 connected to the frame portion J1 via two first beams J2 and a comb electrode J4 formed on the outer periphery of the frame portion J1. And a comb-shaped detection electrode J7 as a detection unit protruding from the base J6 and opposed to the comb electrode J4. Also, the mass part J5 has two second beams J at the base J6.
8 are connected. Such a sensor can be generally manufactured by processing an SOI substrate by a known micromachine technology.

In FIG. 2, first, a weight J3 having a mass m
An excitation mechanism (not shown) using electrostatic force or electromagnetic force
Then, the first beam J2 is driven and vibrated at a speed v in the X direction by the spring force of the first beam J2. When the angular velocity Ω is applied to the entire sensor under the vibration of the velocity v, the weight J3 has Fc = 2
A force of mvΩ, that is, a Coriolis force Fc acts in the Y direction (a direction orthogonal to the drive vibration). And this Coriolis force Fc
Accordingly, the balance of the spring constant of the second beam J8 and the force of the Coriolis force causes the entire mass J5 to be displaced in the Y direction by an amount proportional to the Coriolis force. The amount of this displacement is calculated using the electrodes J4 and J4.
Angular velocity can be detected by detecting the change amount of the interval of 7, that is, the change in capacitance between both electrodes.

[0004]

In FIG. 2, when an acceleration having a component in the Y direction or an external acceleration (referred to as an external acceleration) is applied, the weight J3 is not applied with an angular velocity. Instead, the weight J3 is displaced in the Y direction, the capacitance between the electrodes J4 and J7 changes, and a signal is output as if an angular velocity was applied. Thus, an error occurs in the sensor output due to the influence of the external acceleration.

In order to prevent this phenomenon, conventionally, as shown in FIG. 3, a mass J5 having a weight (vibrator) J3 is provided.
A method is generally employed in which two weights J3 are driven and oscillated (speed v in FIG. 3) at the same frequency and in opposite phases to each other, and the external acceleration components applied to the weights J3 are canceled using a differential circuit. Has been taken.

However, when the method shown in FIG. 3 is adopted, two weights (vibrators) and two driving means (excitation mechanisms) for driving the weights are required.
In order to vibrate at the same frequency at all times, a coupled beam J9 is provided and the weights J3
Need to be connected. For this reason, there is a problem that the sensor employing this method has a complicated structure, and the number of components increases, so that the physical size (chip size) of the sensor increases.

In view of the above problems, it is an object of the present invention to provide an angular velocity sensor capable of detecting a Coriolis force caused by an angular velocity without increasing the physique and without being affected by external acceleration. .

[0008]

According to the present invention, in the conventional angular velocity sensor as shown in FIGS. 2 and 3, since the detecting portion has a structure fixed to an external force, external acceleration is applied. This is done by paying attention to the fact that the influence of the external acceleration (displacement due to the external acceleration) occurs only on the mass part which is the movable structure.

First, according to the first aspect of the present invention, the mass section (20) having the weight section (22) capable of driving vibration in a predetermined direction.
And a detection unit (3) opposed to the mass unit at an interval.
0), and when an angular velocity is generated during the driving vibration of the weight portion, the interval between the facing portion between the mass portion and the detecting portion is changed by Coriolis force acting on the mass portion, and this change is caused. An angular velocity sensor that detects an angular velocity based on an amount is characterized in that when an external acceleration is applied, the detection unit can be displaced in the direction of action of the Coriolis force similarly to the mass unit.

Thus, even if an external acceleration is applied, the detecting section (30) is displaced in the direction in which the Coriolis force acts, similarly to the mass section (20). Does not add the influence of external acceleration. Therefore, there is no need to form a coupled vibration system with two mass parts as in the related art. Therefore, according to the present invention, it is possible to provide an angular velocity sensor capable of detecting a Coriolis force due to an angular velocity without increasing the physique and without being affected by external acceleration.

In the invention according to claim 2, the base (1
0), a mass part (20) having a weight part (22) that can be driven and oscillated in a predetermined direction, and a detection part (30) arranged opposite to the mass part with an interval connected to each other. In the angular velocity sensor that detects the angular velocity based on the amount of change in the facing distance between the mass part and the detection part that changes due to the Coriolis force when the angular velocity occurs, the mass part and the detection part are elastically moved in the direction of action of the Coriolis force, respectively. First stretchable
And a vibration system composed of a mass part and a first beam part and a vibration system composed of a detection part and a second beam part. And
It is characterized in that the resonance frequencies in the direction in which the Coriolis force acts are the same.

Thus, similar to the first aspect of the present invention,
When an external acceleration is applied, the detection unit (30) is displaced in the direction in which the Coriolis force acts in the same manner as the mass unit (20). No effect is added. Therefore, there is no need to form a coupled vibration system with two mass parts as in the related art. Therefore, according to the present invention, it is also possible to provide an angular velocity sensor having the same effects as the first aspect of the present invention.

Here, in the angular velocity sensor according to the second aspect, the mass of the detecting section (30) is m1, the spring constant of the second beam section (35) is k1, the mass section is the mass section. Assuming that the mass of (20) is m2 and the spring constant of the first beam portion (25) is k2, the relationship between these parameters is k1
= K2 · m1 / m2.

The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a gyro sensor, for example.
It is a top view showing one embodiment of an angular velocity sensor 100 of the present invention applied to an application which detects angular velocity. The angular velocity sensor 100 forms a groove by performing an etching process or the like on a semiconductor substrate such as a silicon substrate, and is roughly a rectangular frame-shaped base 1 located at a peripheral portion of the substrate.
0 and a mass 20 located in the frame of the base 10
And the detection unit 30.

The angular velocity sensor 100 uses, for example, an SOI (silicon-on-insulator) substrate in which both silicon substrates are bonded together via an oxide film, and one of the two silicon substrates is used as a support substrate, and the other silicon substrate and the oxidized silicon substrate are used together. By applying well-known micromachining technology such as trench etching and sacrificial layer etching to the film,
The respective parts 10 to 30 are formed on the other silicon substrate.

The mass part 20 is a rectangular frame part 21.
And a rectangular weight portion 22 located in the frame portion 21
And two rectangular frame-shaped vibrating beams 23 connecting the frame portion 21 and the weight portion 22. The vibrating beam 23 has an elastic function capable of expanding and contracting in the X direction shown in the drawing.
1 can be vibrated (driving vibration) in the X direction. Further, a comb-shaped comb-shaped electrode (mass part electrode) 24 protruding from the frame part 21 is formed on a side of the outer periphery of the frame part 21 facing in the X direction.

The frame portion 21 is connected to the base 10 via a rectangular frame-shaped detection beam (a first beam portion in the present invention) 25 on the outer periphery of the side opposed in the Y direction. The detection beam 25 has an elastic function capable of expanding and contracting in the Y direction shown in the drawing. The detection beam 25 causes the weight portion 22 and the frame portion 21, that is, the mass portion 20 to vibrate in the Y direction (detection vibration). It is possible.

Two detection units 30 are provided on both sides of the mass unit 20 in the X direction (left and right directions in the figure). Each detection unit 30 has a rectangular electrode weight 31 as a mass part in the detection unit, and a comb-shaped detection electrode 32 protruding from the electrode weight 31 on the outer periphery of the electrode weight 31. Here, the detection electrode 32 of the detection unit 30 and the comb-tooth electrode 24 are opposed to each other with an interval in the Y direction so as to mesh with each other in a gap between the comb teeth.

The electrode weight 31 is connected to the base 10 via a rectangular frame-shaped electrode beam (second beam portion) 35 on the outer periphery of the side facing in the Y direction. The electrode beam 35 has an elastic function capable of expanding and contracting in the Y direction shown in the drawing.
(Detection unit 30) is capable of vibrating in the Y direction.

Further, the angular velocity sensor 100 has an excitation mechanism (not shown) using an electrostatic force, an electromagnetic force or the like as a driving means for driving and vibrating the weight portion 22 in the X direction. The angular velocity is detected in a state where the weight 22 is driven and vibrated by the excitation mechanism. When the weight portion 22 of the mass portion 20 is driven and vibrated in the X direction by the elastic force (spring force) of the vibrating beam 23 and the driving force of the excitation mechanism, the angular velocity Ω about the vertical axis in FIG. When it occurs,
Coriolis force acts on the weight portion 22 in the Y direction.

The balance of the Coriolis force and the spring force of the detection beam 25 causes the entire mass portion 20 to be displaced in the Y direction, and the distance between the opposing portions of the comb-teeth electrode 24 and the detection electrode 32 facing in the Y direction. Changes. Base 1
By detecting the change in capacitance between the electrodes 24 and 32 via a wiring portion (not shown) formed at 0,
The angular velocity Ω is detected.

As described above, in the angular velocity sensor 100, the mass section 20 and the detection section 30 are each provided with the detection beam 2
5. The vibration function in the Y direction is enabled by the spring function of the electrode beam 35. In this embodiment, the vibration system (mass vibration system) including the mass unit 20 and the detection beam 25 and the detection unit When an acceleration (external acceleration) having a component in the Y direction or in the Y direction is applied to a vibration system (detection unit vibration system) including the electrode beam 30 and the electrode beam 35, the mass unit 20 and the detection unit 30 It is also displaced in the Y direction.

As a result, even if an external acceleration is applied, the detecting section 30 is displaced in the Y direction in which the Coriolis force acts in the same manner as the mass section 20. The influence of the external acceleration is not added to the amount of change in the interval at the portion facing the detection electrode 32. Therefore, unlike the conventional case, there is no need to form a coupled vibration system with the two mass parts, and without increasing the size of the sensor,
It is possible to detect only the Coriolis force substantially caused by the angular velocity without being affected by the external acceleration.

Next, specific means for a mass vibration system and a detection vibration system for similarly displacing the mass unit 20 and the detection unit 30 in the Y direction when an external acceleration is applied will be described. First, when considering displacement caused by external acceleration in the mass unit 20 and the detection unit 30 in the same manner, the following is obtained.

The mass of the electrode weight 31 is m1, the spring constant of the electrode beam (second beam portion) 35 is k1, the mass of the weight portion 22 and the frame portion 21 is m2, and the mass of the detection beam (first beam portion) 25 is m1. Let the spring constant be k2. Since the mass of the detection electrode 32 and the mass of the comb electrode 24 are substantially negligible with respect to the mass m1 and the mass m2, respectively, the mass m1 and the mass m
2 corresponds to the mass of the detection part in the present invention and the mass of the mass part in the present invention, respectively. In this case, when the external acceleration G is applied, the force F1 applied to the mass m1
The force F2 applied to m2 is represented by the following equation (1).

[0027]

F1 = G1 · m1 F2 = G2 · m2 Assuming that the displacement of the electrode weight 31 due to the forces F1 and F2 is A1, and the displacement of the weight 22 and the frame 21 is A2, these displacements A1 and A2 Are shown as in the following Expression 2, respectively.

[0028]

A1 = F1 / k1 A2 = F2 / k2 Since it is necessary to determine k1 and k2 so that these displacement amounts become the same by the force due to the external acceleration, A1 =
If A2 is set, the relationship shown in the following Expression 3 is derived.

[0029]

## EQU3 ## k1 = k2.multidot.m1 / m2 (this is referred to as relational expression 1) By determining the spring constant of each of the beams 25 and 35 as in the above relational expression 1, when the external acceleration is applied, the mass 2
0 and the detection unit 30 can be similarly displaced in the Y direction, and the external acceleration can be canceled.

Further, the mass part vibration system and the detection part vibration system
By making the resonance frequency the same in the Y direction (the direction of action of the Coriolis force), the mass unit 20 and the detection unit 30 can be similarly displaced in the Y direction when an external acceleration is applied, and the external acceleration is canceled. it can.

In view of matching the resonance frequencies, the configuration of the two vibration systems can be embodied as follows. Hereinafter, the mass m1 of the electrode weight 31, the spring constant k1 of the electrode beam 35, and the mass m of the weight 22 and the frame 21 will be described.
2. The spring constant k2 of the detection beam 25 is the same as described above.

Here, ω1 is the resonance frequency of the electrode weight 31 (corresponding to the resonance frequency of the detection unit vibration system), and ω2 is the weight 22
And the resonance frequency of the frame section 21 (corresponding to the resonance frequency of the mass section vibration system), the respective resonance frequencies ω1 and ω2 are expressed by the following Equation 4, respectively.

[0033]

Ω1 = (k1 / m1) ^1/2 ω2 = (k2 / m2) ^1/2 Here, in order to make the two resonance frequencies ω1 and ω2 coincide,
Assuming that ω1 = ω2, the same relation as the above relational expression 1 is obtained as shown in the following Expression 5.

[0034]

K1 = k2 · m1 / m2 As described above, the base 10, the mass portion 20 having the weight portion 22 and the comb-shaped electrode (mass portion electrode) 24, and the comb-shaped electrode 24 face each other with a space therebetween. A detection electrode 32 disposed therein, and when an angular velocity occurs during driving vibration of the weight portion 22, the mass portion 2
0, the two electrodes 24, 32
In the angular velocity sensor that changes the facing distance of the sensor and detects the angular velocity based on the amount of change, an electrode weight 31 as a mass part is integrated with the detection electrode 32, and the electrode weight 31 is connected to the base 10 by an electrode beam 35. Further, by setting the masses m1 and m2 and the spring constants k1 and k2 to be in the relation as in the above-described relational expression 1, it is possible to provide an angular velocity sensor that achieves the object of the present invention.

(Other Embodiments) The shapes of the mass electrode and the detection electrode for detecting a change in capacitance based on a change in the facing distance are not limited to the above-mentioned comb-like shape. Further, in the above embodiment, when the external acceleration is applied by using the beams 25 and 35, the detection unit 30 and the mass unit 20 are displaced similarly to each other. A spring member having a spring function may be used.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing a conventional angular velocity sensor.

FIG. 3 is a plan view showing a conventional angular velocity sensor employing a coupled vibration system.

[Explanation of symbols]

Reference numeral 10: base portion, 20: mass portion, 22: weight portion, 25: detection beam, 30: detection portion, 35: electrode beam.

Claims (3)

[Claims] A weight portion (22) capable of driving vibration in a predetermined direction.
A mass part (20) having: and a detection part (30) arranged to face the mass part with an interval therebetween, and when an angular velocity is generated during driving vibration of the weight part, the mass part (20) In the angular velocity sensor that changes the distance between the facing portion of the mass portion and the detection portion by Coriolis force acting on the mass portion and detects the angular velocity based on the amount of change, when an external acceleration is applied, An angular velocity sensor, wherein the detection unit is displaceable in the direction of the action of the Coriolis force similarly to the mass unit. 2. A mass (20) connected to the base and having a weight (22) that can be driven and oscillated in a predetermined direction, and a mass connected to the base and having an interval between the mass. And a detection unit (30) disposed opposite to the weight unit. When an angular velocity occurs during driving vibration of the weight unit, the mass unit and the detection unit are caused to move by the Coriolis force acting on the mass unit. In an angular velocity sensor that changes an interval between opposed portions and detects the angular velocity based on the amount of change, the mass section includes a first beam section that is elastically expandable and contractable in a direction in which the Coriolis force acts. 25), and the detection unit is connected to the base by a second beam (35) that can elastically expand and contract in the direction of action of the Coriolis force. Vibration composed of one beam An angular velocity sensor, wherein the by the detection unit and vibrating system constituted by the second beam portion, the resonant frequency of the direction of action of the Coriolis force is made identical to each other and. 3. The mass of the detection section (30) is m1, the spring constant of the second beam section (35) is k1, and the mass section (2) is
The angular velocity sensor according to claim 2, wherein, when the mass of 0) is m2 and the spring constant of the first beam portion (25) is k2, the following relationship holds: k1 = k2 · m1 / m2.