JP2000275273A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of being manufactured at low cost with a small facility investment, easily allowing design changes, and capable of maintaining reliability without being necessarily sealed. SOLUTION: This acceleration sensor is provided with a planar electrode provided on the surface of a case, an elastic electrode 1 fixed with its outer edge to the case and facing the lower face of the planar electrode at a fine gap, and a weight 2 fixed to the upper face of the elastic electrode 1. The acceleration applied to the weight 2 is converted into the change quantity of the electrostatic capacity between the planar electrode and the elastic electrode 1. Pawls 10a, 10b, 10c, 10d pinching the weight 2 and holding the weight 2 on the elastic electrode 1 are provided on the upper face of the elastic electrode 1. The layout and shape of the pawls 10a, 10b, 10c, 10d are selected so that the weight 2 is fitted between the pawls 10a, 10b, 10c, 10d while pushing the pawls 10a, 10b, 10c, 10d outwards against the elastic force of the pawls 10a, 10b, 10c, 10d when the weight 2 is moved vertically to the upper face between the pawls 10a, 10b, 10c, 10d from the upper face side of the elastic electrode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of fixing one of two electrodes facing each other in parallel with a small gap therebetween to a flexible elastic body, fixing a weight to the elastic electrode, and reducing the acceleration applied to the weight. The present invention relates to a capacitance-type acceleration sensor that detects the acceleration by utilizing a change in capacitance between two electrodes in response to the change.

[0002]

2. Description of the Related Art An acceleration sensor is mounted on an airbag device to detect whether or not acceleration required to inflate an airbag of a vehicle is applied to the vehicle, or the content of a game and movement of a person are integrated. 2. Description of the Related Art A game device to be converted into a computer has been mass-produced for various uses, for example, mounted on a helmet of a person who operates the game device in order to detect the movement of a human head. The acceleration sensor has X
There are a type that detects all three axes of the axis, the Y axis, and the Z axis, a type that detects two axes of the X axis and the Y axis, and a type that detects only one axis, the Z axis.

In mass-produced acceleration sensors for the above-mentioned applications, silicon acceleration sensors are becoming mainstream with the aim of reducing the unit price and improving reliability. The silicon acceleration sensor is manufactured by a semiconductor process using three silicon wafers: a mass wafer serving as a weight (a pendulum), a diaphragm wafer serving as an elastic electrode, and a base wafer serving as a plane electrode. Since the technology of the semiconductor process has already been established, it can be said that the semiconductor process is excellent in reliability, mass productivity, and inexpensive unit price.

[0004]

However, the manufacture of a silicon acceleration sensor requires a great deal of expense for introducing and maintaining manufacturing equipment for applying a semiconductor process and for designing a mask. Therefore, silicon accelerometers can reduce the unit price to the price required by the customer when producing a large number of tens of thousands to millions of the same specifications, but when the production quantity is not large, the expected price can be reduced. It is not possible to reduce the manufacturing unit price. In general, the number of manufactured airbags and game machines, which are popular products, is easily influenced by the times, and it is not easy to predict the final demand. Under such circumstances, capital investment for manufacturing the silicon acceleration sensor involves a great deal of risk.

Although the silicon acceleration sensor is suitable for mass production, changing the specifications involves great difficulty. For example, once manufacturing of a two-axis acceleration sensor having two axes for detecting acceleration is started, manufacturing equipment is changed to manufacture a three-axis acceleration sensor for detecting three-axis acceleration. It is necessary to make a design change retroactively, which requires a great deal of cost.

In order to reduce the unit price of the silicon acceleration sensor, it is necessary to increase the number of sensor chips per wafer as much as possible. For that purpose, it is necessary to make the silicon acceleration sensor ultra-high-precision and ultra-compact, for example, to make the movable range of the weight (pendulum) several microns (μm). With such a small size, the silicon acceleration sensor is enclosed in a sealed package, and strictly prevents the invasion of moisture, and the reliability cannot be ensured unless dew condensation is prevented. The necessity of such a sealed package also hinders a reduction in the unit price of the silicon acceleration sensor.

An object of the present invention is to provide an acceleration sensor which can be manufactured at a low cost with a small capital investment, can be easily changed in design, and can maintain reliability without necessarily sealing.

[0008]

In order to solve the above-mentioned problems, the present invention provides the following means. A flat electrode provided on the surface of the housing, an elastic electrode having an outer edge fixed to the housing and facing the flat electrode on one plate surface with a small gap therebetween, and the other plate surface of the elastic electrode A weight fixed to the acceleration sensor that converts the acceleration received by the weight into a change in capacitance between the plane electrode and the elastic electrode. And a plurality of claws for holding the weight and holding the weight on the elastic electrode. When approaching the weight between the plurality of claws perpendicular to the other plate surface from the other plate surface side of the elastic electrode,
The arrangement and shape of the claws are selected such that the weight is fitted between the plurality of claws while pushing the plurality of claws outward against the elasticity of the plurality of claws. The acceleration sensor as described above. The elastic electrode is a metal plate such as phosphor bronze,
The acceleration according to claim 1 or 2, wherein the claw is provided with a notch in the plate, and a tongue-shaped portion of the plate desired in the notch is bent and raised toward the other plate surface. Sensor. The tongue-shaped portion is a partial region on the other plate surface, and is separated from a portion slightly apart from the center O of a region where the surface of the weight on the side located on the flat electrode side contacts by a fixed distance. The acceleration sensor according to the above, wherein the acceleration sensor extends radially.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described.
The present invention will be described in more detail.

FIG. 1 is a perspective view showing a coupling structure of an elastic electrode 1 and a weight 2 in a capacitance type acceleration sensor according to a first embodiment of the present invention. FIG. 2 is a plan view (A) showing the elastic electrode 1 of FIG. 1, and a cross-sectional view (B) and a cross-sectional view (C) of FIG. FIG. 3 is a process chart conceptually showing a process of assembling the capacitance type acceleration sensor according to the first embodiment of the present invention. FIG.
FIG. 4 is a longitudinal sectional view conceptually showing the capacitance type acceleration sensor assembled in the process shown in the process diagram of FIG. FIG. 6 shows a two-axis detecting plane electrode 4 and leads 51 to 54 in a capacitance type acceleration sensor (FIG. 4) according to the first embodiment of the present invention.
It is a perspective view which shows notionally.

In these figures, 1 is an elastic electrode, 1a, 1b,
1c, 1d are hinges (fulcrum of pendulum), 2 is weight, 3 is housing,
4 is a plane electrode for two-axis detection, 5 is a lead, 6 is a cover, 9
Is a structure in which the elastic electrode 1 and the weight 2 are connected, 10a, 10b, 10c,
10d is the weight holding claw, 10e, 10f, 10g, 10h is the weight mounting disk 13
Notch provided on the outer electrode of the elastic electrode 1;
Is an inner ring of the elastic electrode 1, 13 is a weight mounting disk of the elastic electrode 1, 14 and 15 are slits, 31 is an annular groove into which the projection 63 of the cover 6 is fitted, 32 is a bottom surface of the housing 3, and 41 is X-axis electrode (+), 42 is X-axis electrode (-), 43 is Y-axis electrode (+), 44
Is a Y-axis electrode (-), 51, 52, 53, 54 are leads, 61 is the weight of the cover 6, the ceiling surface of the accommodation space, and 62 is the weight 2
It is a side wall of the accommodation space.

In the capacitive acceleration sensor according to the first embodiment of the present invention, as shown in FIG. 1, an elastic electrode 1 includes an outer ring 11, an inner ring 12, a weight mounting disk 13, a hinge
(Support point of pendulum) 1a, 1b, 1c, 1d and weight holding claws 10a, 10b, 1
It is composed of 0c and 10d. The elastic electrode 1 is made of phosphor bronze. The outer ring 11 and the inner ring 12 are separated by a slit 14 and connected by hinges 1a and 1b. The inner ring 12 and the weight mounting disk 13 are separated by a slit 15 and connected by hinges 1c and 1d.

The claws 10a, 10b, 10c, 10d are provided with notches 10e, 10f, 10g, 10h on the weight mounting disk 13, and the notches 10e, 10f, 10g, 1
The tongue-shaped portion of the weight mounting disk 13 desired at 0h is bent and raised toward the weight 2 (the other plate surface). The weight 2 is made of phosphor bronze and is mounted at the center of the weight mounting disk 13 and has claws 10a, 10b,
It is sandwiched between 10c and 10d.

This capacitance type acceleration sensor is assembled in the process shown in FIG. The casing 3 in FIG. 3 is made of plastic, has a circular planar shape, has a stepped recess at the upper center, and has a tapered recess at the center of the bottom surface 32. A fitting groove 31 is formed in an upper portion on the outside of the housing 3.

The flat electrode 4 is exposed and fixed to the bottom surface of the upper central recess of the housing 3. The lead 5 for connecting the plane electrode 4 to the outside of the housing 3 is partially molded in the housing 3, and the outer portion of the housing 3 is bent downward along the outside of the housing 3 to form a housing. It is bent horizontally on the surface of the bottom surface 32 of the body 3. In FIG. 6, the leads 51 to 54 are schematically represented, and are drawn straight.

As shown in the process diagram of FIG. 3, in this capacitance type acceleration sensor, the elastic electrode 1 is first fitted in the direction of arrow a from above the housing 3 on which the plane electrode 4 and the lead 5 are formed. Can be The elastic electrode 1 is placed on the bottom surface of the recess at the upper center of the housing 3, and the outer peripheral edge of the elastic electrode 1 is pressed into close contact with the outer peripheral wall of the upper step in the recess at the upper center of the housing 3. 3 securely fixed.

Next, the cylindrical weight 2 is pushed between the claws 10a, 10b, 10c and 10d of the elastic electrode 1 in the direction of arrow b. When the weight 2 is brought closer between the claws 10a, 10b, 10c, and 10d from the direction of the arrow b, the weight 2 removes the claws 10a, 10b, 10c, and 10d against the elasticity of the claws 10a, 10b, 10c, and 10d. Claw 10a, 10b, 10c, 10 so that
The arrangement and shape of d are selected.

Finally, the cover 6 is covered from the direction of arrow c, and the projection 63 of the cover 6 is fitted into the fitting groove 31 of the housing 3. The weight 2 moves when acceleration is applied to the gap between the ceiling surface 61 of the weight 2 housing space in the cover 6 and the upper surface of the weight 2 and the gap between the side wall 62 of the weight 2 housing space and the side surface of the weight 2. Is set to 50 μm.
The movable range of the weight 2 can be arbitrarily designed.
It is selected to be about 100 μm. By providing a gap of 10 μm to 100 μm between the weight 2 and the cover 6, malfunction due to dew condensation does not usually occur.

The cover 6 protects the elastic electrode 1 and the weight 2 from the outside and limits the movable range of the weight 2, so that the elastic electrode 1 and the weight 2 are greatly displaced by excessive input, and the elastic electrode 1 It also functions to prevent deformation beyond the elastic limit and breakage.

The above-described process shown in FIG. 3 is almost the same as the process of assembling the small button switch. In the assembling process of the small button switch, the housing is first fixed, each component is sequentially pushed onto the housing from above, and the whole is unified by repeating simple operations. The technology for assembling such a small button switch has already been completed. If this existing manufacturing equipment is applied to the acceleration sensor of the present invention, the acceleration sensor of the present invention can be manufactured with only slight adjustment of the existing equipment. As a result, the manufacturing cost of the acceleration sensor can be reduced.

FIG. 4 is a longitudinal sectional view conceptually showing the acceleration sensor manufactured in the process of FIG. This acceleration sensor takes out the acceleration received by the weight 2 to the lead 5 as a change in the capacitance between the elastic electrode 1 and the plane electrode 4. FIG.
FIG. 3 is a perspective view conceptually showing the structure of the planar electrode 4 and the lead 5. The elastic electrode 1 acts as a ground electrode facing the flat electrode 4 and a lead for extracting a ground potential to the outside is also connected to the elastic electrode 1, but the lead of the elastic electrode 1 is not shown in FIG.

As shown in FIG. 6, the two-axis detecting plane electrode 4 includes an X-axis electrode (+) 41, an X-axis electrode (-) 42, and a Y-axis electrode (+).
43, and a Y-axis electrode (-) 44. X-axis electrode (+) 41 and X
The axis electrode (-) 42 detects the acceleration in the X-axis direction, and the Y-axis electrode (+) 43 and the Y-axis electrode (-) 44 detect the acceleration in the Y-axis direction.

When there is an acceleration component in the X-axis direction, the hinges 1c and 1d of the elastic electrode 1 bend and extend in the direction perpendicular to the plate surface of the elastic electrode 1, that is, in the direction perpendicular to the plane of FIG. The plate 13 is tilted about the hinges 1a and 1b.
At this time, the capacity between one of the X-axis electrode (+) 41 and the X-axis electrode (-) 42 and the elastic electrode 1 increases, and the capacity between the other electrode and the elastic electrode 1 decreases. .

This change in capacitance is taken out to the outside through the leads 51 and 52 as a plus component and a minus component, and is converted into an electric signal by a signal processing circuit described in, for example, JP-A-5-346357. You. The change in the capacitance of the plus component and the minus component expressed by the electric signal is given to the differential amplifier, and the difference between the plus component and the minus component is amplified and extracted. This difference represents the acceleration detected by the acceleration sensor according to the present embodiment. Thus, the acceleration sensor according to the present embodiment has the weight 2
Can be detected.

When there is an acceleration component in the Y-axis direction, the hinges 1a and 1b of the elastic electrode 1 bend and extend in a direction perpendicular to the plate surface of the elastic electrode 1, that is, in a direction perpendicular to the plane of FIG. The plate 13 tilts with the hinges 1c and 1d as axes.
At this time, the capacitance between one of the Y-axis electrode (+) 43 and the Y-axis electrode (-) 44 and the elastic electrode 1 increases, and the capacitance between the other electrode and the elastic electrode 1 decreases. . This capacitance change is taken out to the outside via the leads 53 and 54 as a plus component and a minus component, and is converted into an electric signal representing acceleration in the same manner as the capacitance change in the X-axis direction.

FIG. 5 is a longitudinal sectional view conceptually showing a typical example of the above-described capacitance type acceleration sensor according to the first embodiment of the present invention. In this type, an elastic electrode pressing ring 8 is provided to more reliably fix the elastic electrode 1 to the housing 3. In the manufacturing process of the capacitance type acceleration sensor shown in FIG. 5, the elastic electrode pressing ring 8 is pressed into the upper concave portion of the housing 3 before attaching the cover 6 in the process drawing of FIG. The elastic electrode pressing ring 8 is made of plastic, and firmly fixes the elastic electrode 1 to the upper step in the concave portion on the upper part of the housing 3.

FIG. 7 shows a first embodiment of the present invention in place of the two-axis detection plane electrode 4 and the leads 51 to 54 shown in FIG. 6 for detecting accelerations in three axes directions of X, Y and Z. FIG. 5 is a perspective view conceptually showing a three-axis detection plane electrode 7 and leads 51 to 55 applicable to the embodiment (FIG. 4). The three-axis detection plane electrode 7 includes a Z-axis electrode 75 in addition to the X-axis and Y-axis acceleration detection electrodes 71 to 74 similar to those of the two-axis detection plane electrode 4. The Z-axis direction is a direction orthogonal to the plane of the plane electrode 7. The acceleration component in the Z-axis direction is Z
It appears as a change in capacitance between the shaft electrode 75 and the elastic electrode 1, and this change in capacitance appears between the lead 55 and the lead of the elastic electrode 1, and is taken out through these leads to the signal processing circuit described above. Is converted into an electric signal. The acceleration component in the Z-axis direction is detected only as an increase or decrease in capacity.

In the acceleration detection method in the X-axis and Y-axis directions described above with reference to FIG. 6, an increase component and a decrease component of the capacitance are detected at the same time, and the increase component and the decrease component of the capacitance are differentially amplified. And the noise component was removed. However, since the acceleration component in the Z-axis direction is detected only as an increase or decrease in capacitance, the noise component cannot be removed from the acceleration component in the Z-axis direction by the differential amplifier.

FIG. 8 shows a first embodiment of the present invention in place of the two-axis detection plane electrode 4 and the leads 51 to 54 shown in FIG. 6 for detecting acceleration only in the Z-axis direction. (FIG. 4) Z-axis detecting flat electrode 76 and lead 56 applicable to FIG.
It is a perspective view which shows notionally. When the Z-axis detection plane electrode 76 of FIG. 8 is provided in the acceleration sensor of FIG. 4 instead of the two-axis detection plane electrode 4 of FIG. 6, only acceleration in one axis direction can be detected. Since the capacitance per axis and the change amount thereof increase, the detection sensitivity can be improved.

In the present invention, even if one of the planar electrodes shown in FIG. 6, FIG. 7 or FIG. 8 is changed to another, only the planar electrode 4 provided on the housing 3 needs to be changed. Cost is low. Therefore, it is possible to select and manufacture an arbitrary plane electrode according to the number of detection directions and the detection sensitivity by changing existing manufacturing equipment with a small cost.

FIG. 9 is a conceptual diagram showing that weights of various shapes can be mounted on the acceleration sensor of the present invention having a weight holding claw on the elastic electrode. FIG. 9A shows a step of fitting the cylindrical weight 2 to the elastic electrode 1 to form the elastic electrode weight structure 9 (same as the above-described step of FIG. 3), and FIG. 9B shows a groove. A step of forming a resilient electrode weight structure 901 by fitting a weight 201 made of a cylindrical column to the elastic electrode 101, and fitting a weight 202 made of a sphere to the resilient electrode 102 in FIG.
The steps of configuring the elastic electrode weight structure 902 are shown respectively. Note that FIG. 9A is drawn in FIG. 3 for comparison with the steps of FIGS. 9B and 9C. Thus, the present invention can be applied to acceleration sensors having weights of various shapes.

FIG. 10 shows that the elastic electrode is made of a metal plate such as phosphor bronze, and the weight holding claw is provided with a notch in the plate, and The tongue is bent and raised to the weight side, and the tongue is a part of the surface of the elastic electrode on the side where the weight contacts, and the surface of the weight located on the side of the flat electrode is Center O of contact area
An acceleration sensor extending radially from portions slightly apart from each other by a fixed distance.
FIG. 9 is a diagram showing a specific example of (corresponding to). This specific example is the second embodiment of the present invention.

In the embodiment shown in FIG. 10, only the weight mounting disk 130 among the elastic electrodes is shown. The basic structure in the embodiment of FIG. 10 is the same as that shown in FIGS. 1 to 4, and is different from that shown in FIGS. 1 to 4 only in the weight mounting disk and the weight ( The weight holding claw and the notch formed in the weight mounting disk are also different). 10, 130a, 130b, 130, 130d are weight holding claws provided on the weight mounting disk 130, and 130e, 130f, 130g, 130h are weight mounting disks 1
It is a notch provided in 30. Weight holding claws 130a, 130b,
130 and 130d correspond to the tongue. The center O is a part of the surface of the elastic electrode on the side where the weight 202 contacts, and the center O of the area where the surface of the weight 202 on the side of the flat electrode (the lower surface of the weight 202 in FIG. 10) contacts. The center.

In the embodiment of the present invention described with reference to FIGS. 1 to 10, as means for fixing the weight to the elastic electrode, weight holding claws 10a, 10b, 10c, 10d or 130a, 130b, 13
0,130d. These claws clamp the weight to fix the weight to the elastic electrode. In such a weight fixing structure, heat distortion occurs in the weight due to heat fluctuation, and when the weight expands and contracts, between the nail and the weight, and the weight mounting surface of the elastic electrode (for example, the weight mounting disk 13 in FIG. 2). Slight sliding occurs between the (center area) and the weight, and the expansion and contraction of the weight does not deform the elastic electrode. That is, the present invention employs a structure in which the weight and the elastic electrode expand and contract independently of each other, and the elastic electrode is less likely to be distorted.

If an adhesive is used as a means for fixing the weight and the elastic electrode, the thermal distortion of the weight deforms the elastic electrode and the distortion of the elastic electrode fluctuates the capacitance. The temperature characteristic greatly depends on the environmental temperature, and the temperature characteristic of the acceleration sensor is significantly deteriorated. Also, if an adhesive is used as a means for fixing the weight and the elastic electrode, after the step of attaching the adhesive to the elastic electrode and placing the weight on the adhesive is completed, the next step is performed until the adhesive is dried. Therefore, it takes time for the production and the production cost is increased.

In the acceleration sensor having the structure shown in FIG.
Is fixed at one point of the elastic electrode, the influence of the thermal distortion of the weight 202 is alleviated more than in the structures of FIGS. 9A, 9B and 9C.

Although the present invention has been described in detail with reference to the embodiments, it goes without saying that the present invention is not limited to these embodiments. For example, weight 2
Is phosphor bronze, but the material of the weight 2 is only required to be a material having a large specific gravity such as a metal, and it is not essential to use phosphor bronze.

[0038]

According to the present invention, as described in detail in the above embodiments, it can be manufactured at a low cost with a small capital investment, the design can be easily changed, and the reliability can be improved without necessarily sealing. Can be provided, and the fluctuation of the measurement accuracy due to the fluctuation of the environmental temperature is small.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a coupling structure between an elastic electrode 1 and a weight 2 in a capacitive acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view (A) showing the elastic electrode 1 of FIG. 1, and a sectional view taken along the line AA (B) and a sectional view taken along the line BB (C) thereof.
It is.

FIG. 3 is a process chart conceptually showing a process of assembling the capacitive acceleration sensor according to the first embodiment of the present invention.

FIG. 4 is a longitudinal sectional view conceptually showing the capacitance type acceleration sensor assembled in the process shown in the process diagram of FIG.

FIG. 5 is a longitudinal sectional view conceptually showing a typical example of a capacitance type acceleration sensor according to the first embodiment of the present invention.

FIG. 6 is a perspective view conceptually showing a two-axis detection plane electrode 4 and leads 51 to 54 in the capacitance type acceleration sensor (FIG. 4) according to the first embodiment of the present invention.

7 shows a two-axis detection plane electrode 4 and a lead 51 shown in FIG. 6 for detecting accelerations in three axes directions of X, Y and Z.
FIG. 5 is a perspective view conceptually showing a three-axis detection plane electrode 7 and leads 51 to 55 applicable to the first embodiment (FIG. 4) of the present invention instead of FIGS.

FIG. 8 is a diagram showing a configuration of FIG. 6 for detecting acceleration only in the Z-axis direction.
A Z-axis detection plane electrode 76 and a lead 56 that can be applied to the first embodiment of the present invention (FIG. 4) are conceptually shown in place of the two-axis detection plane electrode 4 and the leads 51 to 54 shown in FIG. It is a perspective view.

FIG. 9 is a diagram conceptually showing an example of various weights applicable to the capacitance type acceleration sensor of the present invention and a structure for attaching the weights to the elastic electrodes.

FIG. 10A is a cross-sectional view showing a coupling structure between the weight mounting disk 130 and the weight 202 in the capacitive acceleration sensor according to the second embodiment of the present invention, and the weight mounting disk 130.
3B is a plan view and FIG. 3C is a cross-sectional view taken along CC.

[Explanation of symbols]

1, 101, 102, 103 ... Elastic electrode 1a, 1b, 1c, 1d ... Hinge (fulcrum of pendulum) 2, 201, 202 ... Weight 3 ... Housing 4 ... ·····························································································・ Elastic electrode weight coupling structure 10a, 10b, 10c, 10d ・ ・ ・ ・ Claws for holding weights 10e, 10f, 10g, 10h ・ ・ ・ ・ Notches 11 provided on weight mounting disk 13 ・ ・ ・ ・· Outer ring of elastic electrode 1 ····· Inner ring of elastic electrode 1 ····························· Slit 31 ··· An annular groove 32 into which the projection 63 is fitted 32..., The bottom surface of the housing 3 41,71... X-axis electrode (+) 42,72. , 73 ... Y-axis electrode (+) 44,74 ... Y-axis electrode (-) 51,5 2, 53, 54, 55, 56 ······················································································································· ····· Z-axis electrodes 130a, 130b, 130, 130d ··· Weight holding claws 130e, 130f, 130g, 130h provided on the weight mounting disk 130 ··· Provided on the weight mounting disk 130 Cutout

Claims (4)

[Claims] 1. A flat electrode provided on a surface of a housing, an elastic electrode having an outer edge fixed to the housing, and facing the flat electrode on one plate surface with a minute gap therebetween; A weight fixed to the other plate surface of the elastic electrode, the acceleration sensor converts the acceleration received by the weight into a change in capacitance between the planar electrode and the elastic electrode; An acceleration sensor, wherein a plurality of claws for holding the weight and holding the weight on the elastic electrode are provided on a plate surface of the acceleration sensor. 2. The method according to claim 1, wherein when the weight is made to approach the plurality of claws perpendicularly to the other plate surface from the other plate surface side of the elastic electrode, the weight resists the elasticity of the plurality of claws. 2. The acceleration sensor according to claim 1, wherein the positions and shapes of the claws are selected such that the claws are fitted between the claws while pushing the claws outward. 3. The elastic electrode is formed of a metal plate such as phosphor bronze, and the claw is provided with a notch in the plate, and a tongue of the plate desired in the notch is provided. The acceleration sensor according to claim 1, wherein the acceleration sensor is bent and raised toward the other plate surface. 4. The tongue-shaped portion is a partial area on the other plate surface, and is slightly apart from a center O of an area where the surface of the weight on the side located on the flat electrode side contacts with a predetermined distance. The acceleration sensor according to claim 3, wherein the acceleration sensor radially extends from the distant portions.