JP2000346866A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of an acceleration sensor for detecting acceleration based on the variation of electrostatic capacity. SOLUTION: A movable electrode 14 has a fixing portion 142 at its center, a movable portion 143 around the fixing portion 142, three circular arc groove holes 144 having groove hole portion 144a between the fixing portion 142 and the movable portion 143, and groove holes 145 adjacently extending arc-like, in parallel, in the movable portion 143, from adjacent ends 144b of the adjacent groove holes 144 of three circular arc groove holes 144.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting an acceleration based on a change in capacitance.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor for detecting an acceleration caused by the movement of a car or a robot has been widely used for interpolation calculation in a section where radio waves cannot reach in a car navigation system, and for controlling the position and attitude of various robots. Used.

A conventional acceleration sensor includes two fixed electrode plates facing each other with a slight gap therebetween, and a movable electrode plate disposed in a gap between the fixed electrode plates. Since the plate approaches one fixed electrode plate, a method of monitoring the difference in capacitance between each fixed electrode plate and the movable electrode plate and detecting acceleration based on the change is generally used. (For example, Japanese Unexamined Patent Publication
No. 32774).

[0004]

The movable electrode plate provided in the above-described acceleration sensor has a spring portion provided with a plurality of arc-shaped slits formed so as to surround a central portion. Due to the elastic deformation of the spring portion, a portion outside the spring portion approaches one of the two fixed electrode plates in accordance with the acceleration in a direction penetrating the two fixed electrode plates. Even if the acceleration sensor equipped with such a movable electrode plate is a non-defective product at the time of product shipment, the movable electrode plate may be damaged due to vibration during transportation or careless handling by the user, such as dropping to the floor. There is a possibility that the spring part of the movable electrode plate will plastically deform and protrude beyond the end faces of the two fixed electrode plates, easily becoming a defective product. If the operation is found to be defective after the incorporation, a large loss may be caused.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a highly reliable acceleration sensor that has greatly reduced the possibility of defective products due to a large external force.

[0006]

The first acceleration sensor of the acceleration sensor according to the present invention which achieves the above object has a fixed electrode and a fixed electrode which extend in parallel with each other in a direction in which the fixed electrode contacts and separates from the fixed electrode in accordance with the acceleration. In an acceleration sensor comprising a movable movable electrode and detecting acceleration by detecting a change in capacitance between the fixed electrode and the movable electrode, the movable electrode has a predetermined interval between the fixed electrode and the movable electrode. It has a fixed portion fixed at a center in a separated state, and has a movable portion around the fixed portion, which moves in a direction approaching and separating from the fixed electrode with respect to the fixed portion in accordance with acceleration. And
Further, between the fixed portion and the movable portion, has a plurality of arc-shaped groove holes surrounding the fixed portion as a whole,
The slots are characterized in that they have a slot portion that is once radially displaced from the arc forming the slots and then returns to the arcs.

In the first acceleration sensor according to the present invention, since the movable electrode has the slot portion between the fixed portion and the movable portion, the movable electrode can be roughly handled to some extent during transportation or on the user side. Even if a large rotational acceleration is applied in the circumferential direction of the electrode, the movable portion may come into contact with the fixed portion via the slot portion, and the movable portion may be greatly twisted relative to the fixed portion beyond the groove width. Is prevented. Therefore, plastic deformation of the movable electrode is prevented, and a highly reliable acceleration sensor is realized.

A second acceleration sensor of the acceleration sensor according to the present invention for achieving the above object is a fixed electrode and a movable electrode which extends in parallel with each other and moves in a direction to contact / separate from the fixed electrode in accordance with acceleration. In an acceleration sensor that detects acceleration by detecting a change in capacitance between the fixed electrode and the movable electrode, the movable electrode includes:
A fixed portion fixed at a predetermined distance from the fixed electrode is provided at the center, and around the fixed portion, in response to acceleration, relative to the fixed portion, relative to the fixed electrode. A plurality of arc-shaped grooves having a movable portion that moves in the direction of contact and separation, and a plurality of arc-shaped grooves surrounding the fixed portion as a whole between the fixed portion and the movable portion; It is characterized in that there is a slot which extends parallel to each other in an arcuate manner in the movable part in close proximity to each other from the mutually adjacent ends of the mutually adjacent slots among the holes.

In a second acceleration sensor according to the present invention, the movable electrode includes a plurality of arc-shaped slots surrounding the fixed portion between the fixed portion and the movable portion, and an arc-shaped groove inside the movable portion. For having a slot extending in parallel, even if the movable electrode receives a large acceleration in the diametrical direction, for example, being handled somewhat violently during transportation or on the user side, through a plurality of arc-shaped slots surrounding the fixed portion. The movable portion abuts on the fixed portion, and the movable portion is prevented from being largely displaced from the fixed portion beyond the groove width. Also, the portions of the movable portion abut each other via groove holes extending in an arc shape parallel to each other in the movable portion, and a portion of the movable portion greatly deviates from another adjacent portion beyond its groove width. Is also prevented. Therefore, plastic deformation of the movable electrode is prevented, and a highly reliable acceleration sensor is realized.

[0010]

Embodiments of the present invention will be described below.

FIG. 1 is an exploded perspective view of a sensor module in a first embodiment of the acceleration sensor according to the present invention.

One electrode substrate 11 is disposed in the center, and the first and second fixed electrodes 111_1 and 111_2 extending in parallel to each other are formed on the front and back surfaces of the electrode substrate 11.
(Only the second fixed electrode 111_2 is shown in FIG. 1). On both sides of the electrode substrate 11, conductive spacers 12 and 13 for sandwiching the electrode substrate 11 and for adjusting capacitance are arranged. Further, the first and second movable electrodes 1 are provided on both sides of the spacers 12 and 13.
4, 15 are arranged. These first and second movable electrodes 14 and 15 are respectively arranged at positions equidistant from each of the front and back surfaces of the electrode substrate 11.

On both sides of the first and second movable electrodes 14 and 15, conductive spacers 16 and 17 for adjusting the amount of vibration attenuation of the first and second movable electrodes 14 and 15 are arranged. Have been. Further, the spacers 16, 17
The first and second plates 18 and 19 for suppressing vibration of the first and second movable electrodes 14 and 15 are disposed on both sides of the first and second movable electrodes 14 and 15. These electrode substrate 11 and four spacers 1
2, 13, 16, 17, two movable electrodes 14, 15, 2
A hole for fixing is formed in the center of each of the plates 18 and 19, and these parts are fixed by a fixing tool including a washer 20 and a bolt member 21 and a disc spring 22 and a nut 23. Fixed.

FIG. 2 is a diagram showing the front and back surfaces of the electrode substrate shown in FIG.

FIG. 2A is a front view of the electrode substrate 11, and FIG. 2B is a rear view of the electrode substrate 11. The electrode substrate 11 has a hole 112 formed at the center thereof for inserting the bolt member 21. In addition, as shown in FIG. 2A, a conductive land 114_1 for establishing conduction with the first movable electrode 14 is formed around the hole 112 on the surface 113_1 of the electrode substrate 11, and furthermore, The first fixed electrode 111_1 extends away from the conductive land 114_1. Also, the first fixed electrode 111
_1 are formed. Further, as shown in FIG. 2B, the conductive land 11 around the hole 112 is formed on the back surface 113_2 of the electrode substrate 11.
4_2 is formed, and the conductive land 114_2 is further formed.
Away from the second fixed electrode 111_2. Further, a wiring 115_2 electrically connected to the second fixed electrode 111_2 is also formed.

A land 114_1 formed on the front surface 113_1 of the electrode substrate 11 and a back surface 113_2 of the electrode substrate 11
Land 114_2 formed in the through hole 118
Are electrically connected to each other.

The electrode substrate 11 shown in FIG. 2 has a shape shown in FIG. 2 after a conductive pattern made of silver palladium is formed on a ceramic substrate having a much larger area than the electrode substrate 11 and fired. With such a manufacturing method, a large number of electrode substrates can be manufactured at low cost. Also, one electrode substrate 1
Since the first and second fixed electrodes 111_1 and 111_2 are formed on the front surface 113_1 and the rear surface 113_2 of the first device, respectively, the first and second fixed electrodes 111_1 and 111_2 are formed on separate electrode substrates, respectively. Compared with this, the cost can be reduced.

FIG. 3 is a plan view of the movable electrode shown in FIG.

The two movable electrodes 14 and 15 shown in FIG.
The movable electrodes 14 have exactly the same shape and structure. Therefore, only the movable electrode 14 of the two movable electrodes 14 and 15 will be described here.

The movable electrode 14 has a fixing hole 141 formed at the center thereof. In addition, the movable electrode 14
Has a fixed portion 142 fixed at a predetermined distance from the first fixed electrode 111_1 at the center, and has a fixed portion 142 around the fixed portion 142 in accordance with acceleration in response to acceleration. Relatively, the first fixed electrode 111_
1 has a movable part 143 that moves in the direction of coming and going. Further, between the fixed portion 142 and the movable portion 143, the fixed portion 14
A plurality of arc-shaped slots 14 surrounding a circle as a whole
4 (three slots 144 are shown in FIG. 3). Each of the three slots 144 has a slot portion 144a having a shape that temporarily shifts in a radial direction from an arc forming the slots 144 and then returns to the arc. The protrusions 142 of the fixing portion 142 are provided on the inner and outer circumferences of the slot portion 144a.
a, and the concave portion 143a of the movable portion 143 corresponds to this. Because of having such a slot portion 144a, even if the movable electrode 14 receives a large acceleration in the AA direction (circumferential direction) shown in FIG. 3, the convex portion 142a of the fixed portion 142 becomes the concave portion 143a of the movable portion 143. And the movable portion 143 is prevented from being greatly twisted with respect to the fixed portion 142 beyond the groove width. Therefore, plastic deformation of the movable electrode 14 is prevented.

The movable electrode 14 is formed in the adjacent ones of the plurality of arc-shaped grooves 144.
The slots 1 extending from the mutually adjacent ends 144b in parallel with each other in an arc shape in the movable portion 143 in close proximity to each other.
45. Due to the elastic deformation of the leaf springs formed by the slots 144 and 145, the movable portion 143 moves relative to the fixed portion 142 in accordance with the vertical acceleration in FIG.
Of the fixed electrode 111_1. Even if the movable electrode 14 receives a large acceleration in the BB direction (diameter direction) shown in FIG.
Of the movable portion 143 abuts on the outer peripheral portion thereof.
The movable portion 143 is prevented from being largely displaced from the fixed portion 142 beyond the groove width. Furthermore, slot 1
Since the portions of the movable portion 143 abut against each other via 45, it is possible to prevent a portion of the movable portion 143 from being largely displaced from another adjacent portion beyond the groove width. Therefore, plastic deformation of the movable electrode 14 is also prevented.

FIG. 4 is a plan view and a sectional view of the plate shown in FIG.

The two plates 18 and 19 shown in FIG.
Since they have exactly the same shape and structure, only the plate 18 will be described here.

The plate 18 is a circular metal plate having a fixing hole 181 formed in the center thereof. By shortening the distance between the plate 18 and the movable part 143 of the movable electrode 14, the movable part 14 of the movable electrode
3 is suppressed (attenuated). Therefore, an output signal having a desired response frequency characteristic can be obtained by adjusting the distance.

FIG. 5 is a diagram showing a state where the sensor module shown in FIG. 1 is mounted on a circuit board.

The bolt member 21 constituting the sensor module shown in FIG. 1 is inserted into a bolt insertion hole (not shown) of the circuit board 51 and is fixed with a washer 52 and a nut 53 with the circuit board 51 interposed therebetween. Also, this circuit board 51
Oscillator 61 (FIG. 6)
The movable electrode 14, 15 is electrically connected to the wiring pattern from the oscillator 61 via the bolt member 21.

When acceleration acts in the left-right direction in FIG. 5, the movable electrodes 14, 15 are displaced in a direction perpendicular to the electrode substrate 11 (left-right direction in FIG. 5), whereby the movable electrode 14 and the fixed electrode are displaced. The capacitance between the movable electrode 15 and the fixed electrode 111_2 changes, and the acceleration is detected based on the change in the capacitance.

FIG. 6 is a block diagram showing an acceleration detection circuit for detecting an acceleration applied to a sensor module mounted on a circuit board.

A signal from an oscillator 61 oscillating at a predetermined frequency is input to the movable electrodes 14 and 15 shown in FIG. The signals input to the movable electrodes 14 and 15 change according to the acceleration. The capacitance of the capacitor C1 formed by the movable electrode 14 and the fixed electrode 111_1 and the capacitance formed by the movable electrode 15 and the fixed electrode 111_2. A voltage signal OUT corresponding to the acceleration is output via the differential amplifier 62 based on the capacitance of C2. Here, even if the movable electrodes 14 and 15 receive a large acceleration in the diameter direction or a large rotation acceleration in the circumferential direction, the voltage signal O
There is no large disturbance in the UT, and the vibration characteristics are improved.

FIG. 7 is an exploded perspective view of a sensor module of a second embodiment of the acceleration sensor according to the present invention.
It should be noted that the same components as those of the sensor module shown in FIG.

In the sensor module shown in FIG. 7, fixed electrode plates 31 and 32 sandwich both movable electrodes 14 and 15 therebetween, and are opposed to movable electrodes 14 and 15 respectively. They are arranged at equal intervals from each other. In addition, the movable electrodes 14 and 1
A plate 18 that suppresses vibration of both the movable electrodes 14 and 15 is disposed at a position between the movable electrodes 5 and 5. First,
The fixed electrode plates 31, 32 will be described.

FIG. 8 is a diagram showing the front and back surfaces of the fixed electrode plate shown in FIG.

The two fixed electrode plates 31, 32 shown in FIG.
Have exactly the same shape and structure, only the fixed electrode plate 31 will be described.

FIG. 8A is a surface view of the fixed electrode plate 31.
FIG. 8B shows a back view of the fixed electrode plate 31. The fixed electrode plate 31 has a bolt member 2 at its center.
A hole 312 into which the hole 1 is inserted is formed. FIG.
As shown in (a), the surface 313 of the fixed electrode plate 31
In the vicinity of the hole 312, a conductive land 314 for establishing conduction with the movable electrode 14 is formed, and the fixed electrode 311 is spread apart from the conductive land 314. Further, as shown in FIG. 8B, on the back surface 315 of the fixed electrode plate 31, a conductive land 316 is formed around the hole 312, and furthermore, a wiring that is electrically connected to the fixed electrode 311 spreading on the front surface 313. 317 are formed.

The lands 314 formed on the front surface 313 of the fixed electrode plate 31 and the lands 316 formed on the back surface 315 of the fixed electrode plate 31 are electrically connected to each other by through holes 318.

The wiring 317 formed on the back surface 315 of the fixed electrode plate 31 extends from the fixed electrode 311 extending on the surface 313 of the fixed electrode plate 31 along the surface 313 of the fixed electrode plate 31, and This is a part of the wiring extending to the back surface 315 of the fixed electrode plate 31 via a portion of the end face in which the through hole is divided in half.

The fixed electrode plate 31 shown in FIG. 8 is obtained by forming a conductive pattern on a ceramic substrate provided with necessary holes and having a much larger area than the fixed electrode plate 31 and firing it. It is divided so as to have the shape shown, and by such a manufacturing method, a large number of fixed electrode plates (including fixed electrodes and the like) can be manufactured at low cost.

FIG. 9 is a diagram showing a state where the sensor module shown in FIG. 7 is mounted on a circuit board.

The bolt member 21 constituting the sensor module shown in FIG. 7 is inserted into a bolt insertion hole (not shown) of the circuit board 51 and is fixed with a disc spring 52 and a nut 53 with the circuit board 51 interposed therebetween.

As described above, the fixed electrode plates 31 and 32 having the fixed electrodes 311 and 321 are arranged at positions equidistant from each other with the movable electrodes 14 and 15 interposed therebetween. The movable electrodes 14 and 15 and the plate 18
Is provided so as to suppress the vibration of both, so that an output signal having a desired response frequency characteristic can be obtained.

FIG. 10 is an exploded perspective view of a sensor module according to a third embodiment of the acceleration sensor of the present invention.
1 is a diagram showing a state where the sensor module shown in FIG. 10 is mounted on a circuit board.

The sensor module shown in FIG. 10 is different from the sensor module shown in FIG. 7 in that the plate 18 for suppressing the vibration of both the movable electrodes 14 and 15 is omitted. In this manner, the plate 18 may be omitted to reduce the cost and reduce the thickness (see FIG. 11).

FIG. 12 is a plan view (a) and a side view (b) of a sensor module according to a fourth embodiment of the acceleration sensor of the present invention.

The sensor module shown in FIG.
This is the same as the sensor module shown in FIG. 5 described above, and this sensor module is attached to a base 74 by a bracket 71. The movable electrodes 14 and 15 are connected to a terminal 72 via a bracket 71, and the fixed electrodes 111_1 and 111_2 are connected to the terminal 72 via a lead wire 73. These terminals 72 are soldered to a circuit board (not shown) and connected to an acceleration detection circuit (see FIG. 6). As described above, the sensor module may be mounted vertically on the circuit board, and the acceleration acting on the circuit board in the horizontal direction may be detected.

In the above-described embodiment, an example will be described in which two fixed electrodes and two movable electrodes respectively corresponding to the two fixed electrodes and located on opposite sides from the corresponding fixed electrodes are provided. However, the present invention may include one fixed electrode and one movable electrode, or may include two fixed electrodes and one movable electrode disposed in a gap between the fixed electrodes, In short, what is necessary is just to have the fixed electrode and the movable electrode which move in the direction which approaches and separates from the fixed electrode according to the acceleration which spread in parallel with each other.

[0046]

As described above, according to the acceleration sensor of the present invention, plastic deformation of the movable electrode is prevented, and the reliability of the acceleration sensor is greatly improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a sensor module of an acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a front surface and a back surface of the electrode substrate shown in FIG.

FIG. 3 is a plan view of the movable electrode shown in FIG.

FIG. 4 is a plan view and a sectional view of the plate shown in FIG. 1;

FIG. 5 is a view showing a state where the sensor module shown in FIG. 1 is mounted on a circuit board.

FIG. 6 is a block diagram showing an acceleration detection circuit for detecting acceleration applied to a sensor module mounted on a circuit board.

FIG. 7 is an exploded perspective view of a sensor module according to a second embodiment of the acceleration sensor of the present invention.

8 is a diagram showing a front surface and a back surface of the fixed electrode plate shown in FIG.

9 is a diagram showing a state where the sensor module shown in FIG. 7 is mounted on a circuit board.

FIG. 10 is an exploded perspective view of a sensor module according to a third embodiment of the acceleration sensor of the present invention.

11 is a diagram showing a state where the sensor module shown in FIG. 10 is mounted on a circuit board.

FIG. 12 is a plan view (a) and a side view (b) of a sensor module according to a fourth embodiment of the acceleration sensor of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Electrode board 12, 13, 16, 17 Spacer 14, 15 Movable electrode 18, 19 Plate 20 Washer 21 Bolt member 22, 52 Disc spring 23, 53 Nut 31, 32 Fixed electrode plate 51 Circuit board 61 Oscillator 62 Differential amplifier 71 Bracket 72 Terminal 73 Lead wire 74 Base 111_1, 111_2, 311, 321 Fixed electrode 112, 141, 181, 312 Hole 113_1, 313 Front surface 113_2, 315 Back surface 114_1, 114_2, 314, 316 Conductive land 115_1, 115_2, 317 Wiring 118 , 318 through hole 142 fixed part 142a convex part 143 movable part 143a concave part 144, 145 slot 144a slot part 144b end

Claims (2)

[Claims] A fixed electrode and a movable electrode, which extend in parallel with each other and move in a direction approaching and separating from the fixed electrode according to acceleration, detect a change in capacitance between the fixed electrode and the movable electrode. In the acceleration sensor for detecting acceleration, the movable electrode has, at the center, a fixed portion fixed at a predetermined distance from the fixed electrode, and around the fixed portion, the acceleration In response to the fixed portion, the movable portion has a movable portion that moves in a direction of coming into contact with and separating from the fixed electrode, and further surrounds the fixed portion as a whole between the fixed portion and the movable portion. An acceleration sensor having a plurality of arc-shaped slots, wherein the slots have a shape in which the slots once return in the radial direction from the arcs constituting the slots and then return to the arcs. . 2. A method according to claim 1, further comprising: a fixed electrode and a movable electrode that moves in a direction of coming into contact with and separating from the fixed electrode according to acceleration, and detects a change in capacitance between the fixed electrode and the movable electrode. In the acceleration sensor for detecting acceleration, the movable electrode has, at the center, a fixed portion fixed at a predetermined distance from the fixed electrode, and around the fixed portion, the acceleration In response to the fixed portion, the movable portion has a movable portion that moves in a direction of coming into contact with and separating from the fixed electrode, and further surrounds the fixed portion as a whole between the fixed portion and the movable portion. A plurality of arc-shaped slots,
An acceleration sensor further comprising, adjacent to each other, mutually adjacent ends of the adjacent ones of the plurality of arc-shaped slots further extending in an arcuate manner in the movable portion in an adjacent manner. .