JPH1010150A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an acceleration not only in one axial direction, but in three axial directions orthogonal to each other, by dividing an electrode opposite to a charge-holding face along orthogonal axes crossing at a projected position of a center of gravity of a weight orthogonally. SOLUTION: A weight 4 of metal is schematically a rectangular parallelepiped having a center of gravity. A mounting part 41 projects from one face of the weight 4. The weight 4 is mounted on a movable electrode 2 partly at the mounting face 41a, not at the entire one face. The weight 4 is set at the opposite side of a fixed electrode 1 so as to shift the movable electrode 2 when an acceleration is applied. Moreover, the mounting part 41 is located at a projected position of the center of gravity to the movable electrode 2. The fixed electrode 1 faces a chargeholding face 31 of an electret film 3 and is divided into four along orthogonal axes crossing orthogonally at a nearly central position of a circle thereof which coincides with the projeeted position of the center of gravity of the weight 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures a change in capacitance between a fixed electrode and a movable electrode facing each other,
The present invention relates to an acceleration sensor that detects acceleration.

[0002]

2. Description of the Related Art Conventionally, there is an acceleration sensor of this type having a configuration shown in FIG. This device has a fixed first electrode A and a first electrode A having both ends fixed to each other via air.
A second electrode B facing the electrodes, a first electrode A and a second electrode B
And an electret film C facing the second electrode B with a charge holding surface C1 holding a charge at a predetermined interval C2, and a second electrode for applying a displacement to the electret film C when acceleration is applied. Weight D provided on the opposite side of B
And However, this is the charge holding surface C1
Is not divided.

[0003] More specifically, the electret film C is
The charge holding surface C1 is formed of an electretized polymer film, and the charge holding surface C1 is formed at a predetermined interval C
2 is provided to face the plate-shaped second electrode B via air having a constant relative dielectric constant. In addition, a conductive thin film is formed on the surface opposite to the charge holding surface C1, and is electrically connected to the first electrode A.

Here, when an acceleration in a direction orthogonal to the charge holding surface C1 of the electret film C is applied, the electret film C is displaced by the inertia force of its own weight of the weight D, and the electret film C and the charge holding surface C1 are displaced. The distance from the two electrodes B fluctuates. With the change, the capacitance between the electret film C and the second electrode B changes, and the acceleration is detected by measuring the voltage generated during the change.

[0005]

In the above-described conventional acceleration sensor, when an acceleration in a direction perpendicular to the charge holding surface C1 is applied, the electret film C is displaced, and the electret film C and the second electrode B are displaced. The acceleration can be detected by measuring the change in capacitance between the two.

However, the direction of acceleration that can be quantitatively detected is limited to the direction orthogonal to the charge holding surface C1 of the electret film C, that is, limited to the detection in only one axial direction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an acceleration sensor capable of detecting acceleration not only in one axis but also in three axes perpendicular to each other. .

[0008]

According to a first aspect of the present invention, there is provided a fuel cell system comprising: a fixed electrode having fixed ends; a fixed interval having both ends fixed; A movable electrode facing the fixed electrode, and an electret film in which the charge holding surface fixed to one of the fixed electrode and the movable electrode and holding the charge faces the other electrode,
An acceleration sensor comprising a weight provided on the opposite side of the fixed electrode so as to apply a displacement to the movable electrode when applying acceleration, and detecting an acceleration by measuring a change in capacitance between the fixed electrode and the movable electrode. The other electrode facing the charge holding surface is configured to be divided along orthogonal axes that are orthogonal to each other, with the projected position of the center of gravity of the weight as an intersection.

According to a second aspect, in the first aspect, the electret film is fixed to the movable electrode.

According to a third aspect of the present invention, in the first aspect, the weight is configured such that a mounting portion, which is partially coupled to the movable electrode and is mounted, projects a center of gravity of the weight onto the movable electrode. It is configured to protrude.

According to a fourth aspect, in the first aspect, the electret film is fixed to the fixed electrode, and the weight applies a displacement to the movable electrode via a displacement film. It has a configuration.

[0012]

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

Reference numeral 1 denotes a fixed electrode, which is formed of a metal and has a substantially circular thin plate shape and is made of an insulating material 1 made of resin or ceramic.
1, a notch 1 provided along orthogonal axes that are orthogonal to each other with a substantially central position of a circle as an intersection.
The two divided electrodes 1a, 1b, 1c, and 1d are formed, and both ends are fixed to a base (not shown) together with the insulator 11. This will be described later in detail.

Reference numeral 2 denotes a movable electrode, which is formed in a substantially circular thin plate of metal and has both ends fixed to a base, facing the fixed electrode 1 with a predetermined space therebetween through air.

Reference numeral 3 denotes an electret film, which is formed in a substantially circular thin plate shape by a polymer film, and a charge holding surface 31 which is formed into an electret and holds charges is formed on one surface. The charge holding surface 31 is fixed to the movable electrode 2 in a state where the charge holding surface 31 faces the fixed electrode 1.

Reference numeral 4 denotes a weight, which is made of a metal and has a substantially rectangular parallelepiped shape having a center of gravity, and an attachment portion 41 protruding from one surface is provided.
The movable electrode 2 is partially provided on the mounting surface 41a, not on the entire surface.
And is provided on the opposite side of the fixed electrode 1 so as to apply a displacement to the movable electrode 2 when an acceleration is applied. Also,
The attachment portion 41 is provided so as to be located at a position where the center of gravity is projected onto the movable electrode 2.

Here, the fixed electrode 1 faces the charge holding surface 31 of the electret film 3 so that the projected position of the center of gravity of the weight 4 and the substantially center position of the circle are the same, It is divided into four along an orthogonal axis that is orthogonal.

The operation of this will be described. Charge holding surface 3
1. Uniaxial acceleration a in two axial directions orthogonal to each other at 1.
1, when the force F1 is applied to the weight 4 as shown in FIG.
And the weight 4 moves around the center of gravity with the inertia of its own weight. When the weight 4 moves, the movable electrode 2 is displaced, and the electret film 3 fixed to the movable electrode 2 is moved.
Are displaced toward the fixed electrode 1 and the opposite side, respectively, about the projected position of the center of gravity of the weight 4. When displaced, the capacitance between the movable electrodes 2 and 1b and 1d among the divided electrodes 1a, 1b, 1c and 1d of the fixed electrode 1 increases, while the capacitance between the divided electrodes 1a and 1c and the movable electrode 2 increases. Of the divided electrodes 1a, 1b, 1c, 1d
Capacitance changes occur independently from each other, and an output voltage is obtained from each.

Assuming that the output voltages measured from the divided electrodes 1a, 1b, 1c, 1d are Va, Vb, Vc, Vd, respectively, Vb-Va and Vd-Vc are obtained, and the acceleration is detected. The same applies to the accelerations of the other axes in the two axis directions orthogonal to each other, and the acceleration is detected by obtaining Va-Vc and Vb-Vd, respectively.

Also, the weight 4 is a mounting surface 4 having a small mounting area.
1a, the electret film 3 is displaced by being coupled to the movable electrode 2, so that both sides of the electret film 3 are largely displaced toward the fixed electrode 1 and the opposite side, respectively, around the projected position of the center of gravity of the weight 4, that is, the displacement And the rate of change of the capacitance increases.

When an acceleration a2 in a direction perpendicular to the charge holding surface 31, that is, in a direction perpendicular to the above-described two axial directions is applied, a force F2 acts on the weight 4 as shown in FIG. It moves in the direction of acceleration with inertia. The electret film 3 fixed to the movable electrode 2
Both sides of the weight 4 are displaced toward the fixed electrode 1 with respect to the projection position of the center of gravity. When displaced, each split electrode 1
The capacitance between a, 1b, 1c, 1d and the movable electrode 2 increases, causing a change in capacitance, and an output voltage is obtained.

In the acceleration sensor according to the first embodiment, as described above, the fixed electrode 1 facing the charge holding surface 31 of the fixed electrode 1 or the movable electrode 2 extends along orthogonal axes orthogonal to each other. Divided and the intersection of each orthogonal axis is weight 4
When the weight 4 moves about the center of gravity when acceleration is applied in two axial directions orthogonal to each other, both sides of the movable electrode 2 center on the projection position of the center of gravity of the weight 4. The fixed electrode 1 and the movable electrode 2 are respectively displaced toward the fixed electrode 1 side and the opposite side thereof.
And the capacitance between the two changes independently, so that the accelerations in two axial directions orthogonal to each other can be quantitatively measured. When an acceleration in a direction orthogonal to the biaxial direction is applied, the movable electrode 2 is displaced to the fixed electrode 1 side or the opposite side, and the acceleration in this direction is also detected, that is, in the triaxial direction. Acceleration can be measured quantitatively.

Further, since the electret film 3 is fixed to the movable electrode 2, the fixed electrode 1 in which the divided electrode is not movable
Notch 1 along orthogonal axes orthogonal to each other
2, the fixed electrode 1 can be easily divided.

Further, since the mounting portion 41 is provided on the weight 4 at a position where the center of gravity of the weight 4 is projected on the movable electrode 2, the weight 4
The movable electrode 2 is partially but not entirely provided through the mounting portion 41.
And the mounting area is reduced,
When the acceleration in the axial direction is applied, both sides of the movable electrode 2 are largely displaced toward the fixed electrode 1 side and the opposite side around the projected position of the center of gravity of the weight 4.
The rate of change of the capacitance between the movable electrode 2 and the movable electrode 2 is increased, and acceleration in two axial directions can be detected with high sensitivity.

In the first embodiment, the charge holding surface 31
Although the fixed electrode 1 facing is divided into four parts, as shown in FIG. 5, the projection may be divided into three parts along orthogonal axes perpendicular to each other with the projection position of the center of gravity of the weight 4 as an intersection.

In the first embodiment, acceleration in one direction is detected in three axes orthogonal to each other. However, not only one direction but also acceleration in the other direction is periodically applied. May be detected without any limitation.

A second embodiment of the present invention will be described below with reference to FIGS. In the second embodiment, functions different from those in the first embodiment will be described, and members having substantially the same functions as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

The electret film 3 is fixed between the fixed electrode 1 and the movable electrode 2 with the charge holding surface 31 facing the movable electrode 2. Here, the movable electrode 2 has the same projected position of the center of gravity of the weight 4 and the substantially center position of the circle, and is divided into four parts along orthogonal axes which are orthogonal to each other with the position as an intersection. 2a, 2b, 2c and 2d are formed.

The displacement film 5 is formed in a substantially circular thin plate shape from a polymer film, is located between the weight 4 and the movable electrode 2, and is fixed to the movable electrode 2. The weight 4 is partially attached to the displacement film 5 on the attachment surface 41a, not the entire surface, and is attached to the displacement film 5 so that the movable electrode 2 is displaced via the displacement film 5 when acceleration is applied. It is provided to the side.

The operation of the above will be described. When uniaxial acceleration a1 is applied in two axial directions orthogonal to each other,
The force F1 acts on the weight 4, and the weight 4 moves around the center of gravity with its own inertia. Then, the weight 4 becomes the displacement film 5
The movable electrode 2 is displaced through the movable electrode 2, and both sides of the movable electrode 2 around the projected position of the center of gravity of the weight 4 are fixed electrode 1.
Side and the opposite side. Of the other divided electrodes 2a, 2b, 2c, 2d provided on the movable electrode 2, 2
While the capacitance between the fixed electrodes 1 and 2b and 2d increases, the capacitance between the fixed electrodes 1 and 2a and 2c decreases, and the separate electrodes 2a, 2b, 2
Capacitance change occurs independently between c and 2d, and an output voltage is obtained.

The output voltages measured from the other divided electrodes 2a, 2b, 2c, 2d are respectively represented by Va, Vb, Vc, V
Assuming d, acceleration is detected by obtaining Vb-Va and Vd-Vc, respectively. The same applies to the accelerations of the other axes in the two axis directions orthogonal to each other.
The acceleration is detected by obtaining c and Vb-Vd, respectively.

In the direction orthogonal to the electret film 3,
That is, when an acceleration a2 in a direction orthogonal to the two axial directions is applied, the force F2 acts on the weight 4, and the weight 4 moves in the acceleration direction with its own inertia. The movable electrodes 2 on both sides are respectively displaced toward the fixed electrode 1 around the projection position of the center of gravity of the weight 4. The capacitance between each of the separate electrodes 2a, 2b, 2c, 2d provided on the movable electrode 2 and the fixed electrode 1 independently increases to cause a capacitance change, and an output voltage is obtained.

In the acceleration sensor according to the second embodiment, as described above, if the electret film 3 is fixed to the fixed electrode 1, the divided electrode is the charge holding surface 31 of the electret film 3. As the movable electrode 2 facing, the weight 4 is not directly connected to the movable electrode 2 and the displacement film 5
The movable electrode 2 is displaced through the movable electrode 2, so that the movable electrode 2 can be formed on one surface of the displacement film 5 and easily divided along orthogonal axes orthogonal to each other.

[0034]

According to the first aspect of the present invention, the other of the fixed electrode and the movable electrode facing the charge holding surface is divided along orthogonal axes orthogonal to each other, and the intersection of each orthogonal axis has a weight. Since it is located at the projection position of the center of gravity, when acceleration is applied in two axial directions orthogonal to each other and the weight moves about the center of gravity, both sides of the movable electrode center on the projection position of the center of gravity of the weight and the fixed electrode side and Displaced to the opposite sides, the capacitance between the other divided electrode and one of the divided electrodes changes independently of each other, and the accelerations in two orthogonal directions orthogonal to each other can be quantitatively measured. Also, 2
When acceleration in a direction perpendicular to the axial direction is applied,
The movable electrode is displaced to the fixed electrode side or the opposite side, and acceleration in this direction is also detected, that is, acceleration in three axial directions can be quantitatively measured.

According to the second aspect, in addition to the effect of the first aspect, since the electret film is fixed to the movable electrode, the divided electrodes become non-movable fixed electrodes, and are formed on orthogonal axes orthogonal to each other. Can be easily divided along.

According to the third aspect, in addition to the effect of the first aspect, since the mounting portion is provided on the weight at a position where the center of gravity of the weight is projected on the movable electrode, the weight is connected via the mounting portion. When the mounting area is reduced by being partially coupled to the movable electrode instead of the entire surface, and acceleration in two orthogonal directions is applied, both sides of the movable electrode center on the projected position of the center of gravity of the weight and the fixed electrode side. The displacements are greatly displaced to the opposite sides, and the rate of change of the capacitance between the other electrode and the one electrode is increased, so that the acceleration in the two axial directions can be detected with high sensitivity.

According to the fourth aspect, in addition to the effect of the first aspect, if the electret film is fixed to the fixed electrode, the divided electrode is a movable electrode whose charge holding surface faces the movable electrode. Therefore, since the weight applies displacement to the movable electrode via the displacement film without being directly connected to the movable electrode, the movable electrode is formed on one surface of the displacement film and easily divided along orthogonal axes perpendicular to each other. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a plan view of the fixed electrode according to the first embodiment.

FIG. 3 is a cross-sectional view in a state where acceleration is applied in two axial directions orthogonal to each other on the charge holding surface according to the first embodiment.

FIG. 4 is a cross-sectional view in a state where an acceleration is applied in a direction perpendicular to the charge holding surface of the above.

FIG. 5 is a plan view when the fixed electrode is divided into three parts.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a perspective view of a weight and a displacement film according to the third embodiment.

FIG. 8 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed electrode 2 Movable electrode 3 Electret film 31 Charge holding surface 4 Weight 41 Mounting part 5 Displacement film

Claims (4)

[Claims] 1. A fixed electrode, a movable electrode fixed at both ends and provided at a predetermined interval and facing the fixed electrode via air,
A charge holding surface that is fixed to one of the fixed electrode and the movable electrode and holds the charge is provided on the opposite side of the electret film facing the other electrode and the fixed electrode so that the movable electrode is displaced when acceleration is applied. Equipped with weights,
An acceleration sensor for measuring a change in capacitance between a fixed electrode and a movable electrode to detect acceleration, wherein the other electrodes facing the charge holding surface intersect with a projected position of a center of gravity of the weight as an intersection. An acceleration sensor, wherein the acceleration sensor is divided along an orthogonal axis that is orthogonal to the acceleration sensor. 2. The acceleration sensor according to claim 1, wherein the electret film is fixed to the movable electrode. 3. The weight according to claim 1, wherein an attachment portion partially attached to and attached to the movable electrode is provided so as to protrude from a position where the center of gravity of the weight is projected onto the movable electrode. The acceleration sensor according to any one of the preceding claims. 4. The acceleration sensor according to claim 1, wherein the electret film is fixed to the fixed electrode, and the weight applies a displacement to the movable electrode via a displacement film.