JP2002055117A - Capacitance type acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a capacitance type acceleration sensor by providing a means for absorbing and damping the excessive displacement of the movable part of a flexible member. SOLUTION: This capacitance type acceleration sensor comprises a base member 1 having a housing hole 11 for movably housing a weight 3 displaceable according to the force generated by acceleration; the flexible member 2 having the movable electrode 21 formed on one of two opposed electrodes for accumulating charges in the movable part for suspending and supporting the weight, which is placed on the opening end surface of the housing hole; and a wiring plate member 5 having the other fixed electrode 51 of the two opposed electrodes for accumulating the charge, which is placed on the flexible member with a prescribed space. Damper means 7, 8 and 9 for absorbing and damping the excessive displacement of the movable part of the flexible member area provided between the housing hole and the weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type acceleration sensor for detecting acceleration by converting a displacement of a weight into a change in capacitance, and more particularly to an improvement in the structure of the capacitance type acceleration sensor. .

[0002]

2. Description of the Related Art An outline of a conventional capacitance type acceleration sensor will be described with reference to FIGS. FIG. 6 is a side sectional view of a conventional capacitance type acceleration sensor. FIG.
FIG. 7 is a sectional view taken along line aa in FIG. FIG. 8 is a configuration diagram of the signal processing circuit.

In FIGS. 6 and 7, a base 1 is provided with a bottomed cylindrical receiving hole 11 having one end opened, and a frame portion of the diaphragm 2 is placed on an opening end surface of the receiving hole 11. You. A movable portion that closes the opening of the housing hole 11 is formed continuously with the frame of the diaphragm 2.

The movable portion of the diaphragm 2 is
Although the center is located on the center axis of 1 and has an outer periphery slightly smaller than the inner diameter of the housing hole 11, the movable electrode 21 is provided on the upper surface, and the weight 3 hanging in the housing hole 11 is supported at the center position. . Thereby, the weight 2 can be displaced in the accommodation hole 11 according to the force generated by the acceleration.

[0005] Then, on the frame of the diaphragm 3,
The wiring board 5 is placed via the spacer 4 having a predetermined thickness.
On the lower surface of the wiring board 5, four fan-shaped fixed electrodes (S _A , S
_B , S _C , S _D ) 51 are arranged at 90 ° intervals.
In the illustrated example, when the center positions of the four fixed electrodes 51 are aligned with the origin of the XY coordinates (located on the center axis of the accommodation hole 11 of the base 1), the four fixed electrodes 51 are fixed to the-(minus) side of the X axis. electrode S _a, the fixed electrode S _B to the + (plus) side is arranged, fixed electrodes in the + direction of the Y axis S _C, - is a fixed electrode S _D side are respectively disposed.

The movable electrode 31 has the same shape and size as the four fixed electrodes 51, and is formed so as to have the same center position. That is, the four movable electrodes 21 and the four fixed electrodes 51 are opposed to each other with a gap corresponding to the thickness of the spacer 4. As a result, a capacitance type acceleration sensor in which two opposing electrodes are formed in the X-axis direction and two in the Y-axis direction to accumulate electric charges is obtained. In FIG.
The capacitances in the X-axis direction are illustrated as C _A and C _B.

[0007] A signal processing circuit shown in FIG. 8 is mounted on the wiring board 4. The signal processing circuit detects a change in the capacitance (C _A , C _{B in the} illustrated example) of the four opposing electrodes and converts the change into a voltage signal, and a noise component from the voltage signal. And a low-pass filter 82 for removing and outputting.

Although not shown, the diaphragm 2
The spacer 4 and the wiring board 5 are collectively screwed and fixed on the open end face of the base 1.

In the above configuration, when the weight 3 is displaced by a force due to acceleration, the movable electrode 21 of the diaphragm 2
Is displaced, the distance between the opposing electrodes changes, and the corresponding capacitance changes. In the signal processing circuit, in the C / V conversion circuit 81, the capacitance change (ΔC ₌ C A _-C B)
, An acceleration is detected, a voltage signal indicating the acceleration is generated, and the low-pass filter 82 generates a voltage signal.
One digital signal is converted into an analog signal, and a signal having a response frequency or higher is cut off and output.

[0010]

However, since the vibration of the diaphragm (movable part) has a resonance frequency,
Problems such as malfunction (FIGS. 9 and 10) and component collision (FIG. 11) occur. Therefore, it can be said that the conventional capacitance-type acceleration sensor includes a factor that lowers the reliability. Hereinafter, a specific description will be given.

FIG. 9 is an explanatory diagram showing the relationship between the vibration frequency and the output amplitude. FIG. 10 is a frequency-output characteristic diagram. As shown in FIGS. 9B and 9C, the same acceleration (1
G), the vibration frequency is 1 away from the resonance frequency.
The sensor output amplitude value V2 when the vibration frequency is 100 Hz closer to the resonance frequency side becomes larger than the sensor output amplitude value V1 when it is 0 Hz. As a result,
Even with the same acceleration, the detected acceleration may differ depending on the vibration frequency.

Specifically, as shown in FIG. 10, the sensor output amplitude is determined by the vibration frequency of the diaphragm being equal to the resonance frequency f.
In the case of a low frequency far below c, the frequency is constant irrespective of the vibration frequency. However, when the vibration frequency of the diaphragm increases and approaches the resonance frequency (resonance point) fc, it rapidly increases, and the resonance frequency (resonance frequency) At point). The increase in the output amplitude near the resonance point is too large to be suppressed by the low-pass filter.

That is, when the sensor output amplitude is constant irrespective of the vibration frequency of the diaphragm, since the capacitance changes linearly with respect to the displacement of the weight, the acceleration can be correctly detected. However, when the vibration frequency of the diaphragm is near the resonance frequency, the movable part is rapidly displaced, so that the capacitance changes nonlinearly with respect to the displacement of the weight, and the acceleration cannot be detected correctly and malfunctions. become.

Further, since the vibration amplitude increases as the vibration frequency of the diaphragm approaches the resonance frequency fc, when the movable portion of the diaphragm is displaced by more than the rating, FIG.
As shown in FIG. 1, the weight 3 collides with the receiving hole 11 of the base 1 or the opposing electrodes collide with each other, thereby damaging the components.

The present invention has been made to solve the conventional problem, and has as its object the provision of a means for absorbing and attenuating an excessive displacement of a movable portion of a diaphragm, thereby improving reliability. An object of the present invention is to provide a capacitance type acceleration sensor.

[0016]

In order to achieve the above object, a capacitive acceleration sensor according to the present invention has the following means and configuration.

According to a first aspect of the present invention, there is provided a capacitance type acceleration sensor, wherein a base member having a receiving hole for movably receiving a weight displaced in response to a force generated by acceleration is provided on an opening end face of the receiving hole. A flexible member on which one movable electrode of two opposing electrodes is formed to accumulate electric charges in a movable portion where the weight is suspended and supported, and a predetermined interval is placed thereon, In a capacitance type acceleration sensor in which a wiring board member on which the other fixed electrode of the two electrodes facing each other is stored is mounted, a flexible member is movable between the accommodation hole and the weight. A damper means for absorbing and attenuating excessive displacement of the portion is provided.

According to the first aspect of the invention, when the movable portion of the flexible member attempts to perform an excessive displacement near the resonance frequency, the displacement is absorbed and attenuated by the damper means. Therefore, it is possible to eliminate a malfunction or a collision between components caused by an excessive displacement of the movable portion, and it is possible to improve the reliability of the sensor.

According to a second aspect of the present invention, in the capacitive acceleration sensor according to the first aspect, the damper is provided at a central position of a bottom of the housing hole. A recess, a boss protruding from a surface of the weight facing the bottom of the receiving hole and having a tip extending into the recess, and a low-hardness filler filled in the recess and interfering with the tip of the boss. And a curing agent.

According to the second aspect of the present invention, the movable portion of the flexible member is excessively displaced near the resonance frequency due to the characteristics of the low-hardness hardener and the interference between the hardener and the boss. Is absorbed and attenuated. At this time,
The interference between the hardener having low hardness and the boss does not prevent the movable portion of the flexible member from vibrating in a required response frequency range.

According to a third aspect of the present invention, in the capacitive acceleration sensor according to the second aspect, the curing agent is a silicone gel.

According to the third aspect of the present invention, an easily available silicone gel can be used as a curing agent.

According to a fourth aspect of the present invention, there is provided a capacitance type acceleration sensor according to the first aspect, wherein the damper is filled between the accommodation hole and the weight. Characterized in that it is a viscous liquid having a low kinematic viscosity.

According to the fourth aspect of the present invention, the movable portion of the flexible member has a resonance frequency due to the kinematic viscosity and the filling amount of the low kinematic viscosity liquid filled between the accommodation hole and the weight. Attempts to effect excessive displacement in the vicinity are absorbed and attenuated. At this time, the viscous liquid filled between the accommodation hole and the weight does not prevent the movable portion of the flexible member from vibrating in a required response frequency range.

According to a fifth aspect of the present invention, in the capacitive acceleration sensor according to the fourth aspect, the viscous liquid is silicon oil.
It is characterized by the following.

According to the fifth aspect of the present invention, easily available silicone oil can be used as the viscous liquid.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of a capacitance type acceleration sensor according to a first embodiment of the present invention. The first embodiment corresponds to claims 1 to 3. 1, the same components as those of the conventional example (FIG. 6) are denoted by the same reference numerals and names. Hereinafter, the portion according to the first embodiment will be mainly described.

In FIG. 1, in the first embodiment, the damper means provided between the accommodation hole 11 and the weight 3
A boss 8 protruding from a surface of the weight 3 facing the bottom of the receiving hole 11 and having a tip portion extending into the recess 7; It is composed of a silicon gel 9 which is a low-hardness hardener that interferes with the tip of the boss 8. The recess 7 has a circular opening large enough to allow the weight 3 to be displaced within a specified range.

The relationship between the above configuration and the claims is as follows. The base 1 corresponds to the base member.
The accommodation hole 11 corresponds to the accommodation hole. Weight 3
Corresponds. The diaphragm 2 corresponds to the flexible member. The wiring board 5 corresponds to the wiring board member. The movable electrode 21 corresponds to the movable electrode. The fixed electrode 51 corresponds to the fixed electrode. The entirety of the concave portion 7, the boss 8, and the silicon gel 9 corresponds to the damper means.

Next, the operation of the first embodiment will be described with reference to FIGS. FIG. 2 is an assembly procedure diagram of the capacitive acceleration sensor according to the first embodiment. FIG.
FIG. 4 is an explanatory diagram showing a relationship between a vibration frequency and an output amplitude obtained by the capacitance type acceleration sensor of the embodiment. FIG. 4 is a frequency-output characteristic diagram of the capacitance type acceleration sensor according to the embodiment.

First, an assembling procedure will be described. In FIG. 2A, a silicon gel 9 is injected into the concave portion 7 at the bottom of the accommodation hole 11, and then, on the opening end surface of the base 1, the diaphragm 2, the weight 3 of which is suspended, the spacer 4, and the wiring board 5 are placed in this order. Place. Then, as shown in FIG. 2B, when the silicon gel 9 is hardened, the capacitance type acceleration sensor of the first embodiment is completed.

In the capacitive acceleration sensor according to the first embodiment, as shown in FIG. 2B, the boss 8 on the bottom surface of the weight 3 enters the recess 7 and the cured silicon gel 9 and the boss 8
Are in a state of interference.

In this state, if the movable part of the diaphragm 2 tries to vibrate excessively near the resonance frequency, the vibration is suppressed and transmitted to the silicon gel 9 by the interference between the boss 8 and the silicon gel 9. 9 and is attenuated.

Thus, mainly the silicon gel 9
It acts as a damper for absorbing and attenuating excessive vibrations near the resonance frequency of the movable part of the diaphragm 2, thereby suppressing an increase in the sensor output amplitude.

Therefore, as shown in FIGS. 3B and 3C, the sensor output amplitude value V1 when the vibration frequency is 10 Hz away from the resonance frequency for the same acceleration (1 G).
And the sensor output amplitude value V2 when the vibration frequency is 100 Hz which is closer to the resonance frequency side.

The silicon gel 9 has a low hardness,
Since the amount of interference with the boss 8 is small, the displacement of the boss 8 is not hindered within the necessary response frequency range in a frequency band much lower than the resonance frequency, and the load of the displacement of the movable portion of the diaphragm 2 Therefore, the sensor output amplitude value does not decrease.

Therefore, by the combination of the silicon gel damper and the low-pass filter 82 of the signal processing circuit (FIG. 8), the output amplitude of the sensor becomes as shown in FIG.
Within the required response frequency range, it can be kept constant irrespective of the vibration frequency of the movable part of the diaphragm 2, and the output above the response frequency range can be cut.

By changing the hardness of the silicon gel 9, the shape of the boss 8, the amount of interference between the boss 8 and the silicon gel 9, etc., the water reduction rate and the response frequency range of the damper can be arbitrarily changed.

FIG. 5 is a side sectional view of a capacitance type acceleration sensor according to a second embodiment of the present invention. Book second
The embodiment corresponds to claims 1, 4, and 5. In FIG.
The same components as those in the conventional example (FIG. 6) are denoted by the same reference numerals and names. Hereinafter, the portion according to the second embodiment will be mainly described.

In FIG. 5, in the second embodiment, as the damper means provided between the accommodation hole 11 and the weight 3, the silicone oil 10 which is a viscous liquid is filled between the accommodation hole 11 and the weight 3. .

Explaining the relationship between the above configuration and the claims, the silicon oil 10 corresponds to the damper means.

The assembly of the capacitance type acceleration sensor according to the second embodiment is performed in the same procedure as that described with reference to FIG. That is, an appropriate amount of silicone oil 10 is injected into the housing hole 11, and then the diaphragm 2, the weight 3 of which is suspended, the spacer 4, and the wiring board 5 are placed on the opening end face of the base 1 in this order. Then, as shown in FIG. 5, the periphery of the weight 3 is filled with the silicon oil 10.

Since the silicone oil 10 has a low kinematic viscosity (for example, about 1000 St), it acts as a damper for absorbing and attenuating excessive vibration near the resonance frequency of the movable part of the diaphragm 2 as in the first embodiment. Thus, an increase in the sensor output amplitude is suppressed.

Accordingly, as shown in FIGS. 3B and 3C, the sensor output amplitude value V1 when the vibration frequency is 10 Hz away from the resonance frequency for the same acceleration (1 G).
And the sensor output amplitude value V2 when the vibration frequency is 100 Hz which is closer to the resonance frequency side.

Further, since the silicon 10 has a low kinematic viscosity (for example, about 1000 St), the displacement of the weight 3 is not hindered within a required response frequency range in a frequency band much lower than the resonance frequency. It does not load the displacement of the movable part of the diaphragm 2, and the sensor output amplitude value does not decrease.

Therefore, as in the first embodiment, the combination of the silicon oil damper and the low-pass filter 82 of the signal processing circuit (FIG. 8) causes the output amplitude of the sensor to have a required response as shown in FIG. Within the frequency range, the output can be kept constant irrespective of the vibration frequency of the movable part of the diaphragm 2 and the output over the response frequency range can be cut.

By changing the kinematic viscosity and the filling amount of the silicon 10, the water reduction rate and the response frequency range of the damper can be arbitrarily changed.

[0049]

As described above, according to the first aspect of the present invention, excessive displacement of the movable portion of the flexible member near the resonance frequency is absorbed and attenuated by the damper means. Therefore, it is possible to eliminate a malfunction or a collision between components caused by an excessive displacement of the movable portion, and it is possible to improve the reliability of the sensor.

According to the second aspect of the present invention, it is absorbed that the movable portion of the flexible member attempts to displace excessively near the resonance frequency due to the characteristics of the hardener having low hardness and interference with the boss. Attenuated. At this time, interference between the low-hardness hardener and the boss can be prevented from hindering the movable portion of the flexible member from vibrating in a required response frequency range. Also,
The response frequency range can be changed and set to a desired range by a combination of the characteristics of the low-hardness hardener and the interference with the boss.

According to the third aspect of the present invention, an easily available silicone gel can be used as a hardening agent, and it can be constructed at a low cost.

According to the fourth aspect of the present invention, the movable portion of the flexible member has a resonance frequency near the resonance frequency due to the kinematic viscosity and the filling amount of the low kinematic viscosity liquid filled between the accommodation hole and the weight. Attempts to cause excessive displacement are absorbed and attenuated. At this time, the viscous liquid filled between the accommodation hole and the weight is
The movable portion of the flexible member can be prevented from vibrating in the required response frequency range. Further, the response frequency range can be changed and set to a desired range by a combination of the kinematic viscosity of the viscous liquid and the filling amount.

According to the fifth aspect of the present invention, easily obtainable silicone oil can be used as the viscous liquid, and it can be constructed at a low cost.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a capacitance type acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is an assembly procedure diagram of the capacitive acceleration sensor according to the first embodiment. (A) is an explanatory view of a procedure for assembling the mounted components after injecting the silicon gel. (B) is an explanatory view in which the silicone gel is cured and completed after assembly.

FIG. 3 is a frequency-output characteristic diagram of the capacitance type acceleration sensor according to the embodiment;

FIG. 4 is an explanatory diagram showing a relationship between a vibration frequency and an output amplitude obtained by the capacitance type acceleration sensor of the embodiment.

FIG. 5 is a side sectional view of a capacitance type acceleration sensor according to a second embodiment of the present invention.

FIG. 6 is a side sectional view of a conventional capacitance type acceleration sensor.

FIG. 7 is a sectional view (fixed electrode shape view) taken along the line aa in FIG.

FIG. 8 is a configuration diagram of a signal processing circuit.

FIG. 9 is a diagram illustrating a relationship between a vibration frequency and an output amplitude obtained by a conventional capacitance type acceleration sensor.

FIG. 10 is a frequency-output characteristic diagram of a conventional capacitive acceleration sensor.

FIG. 11 is an explanatory diagram of a collision between components due to resonance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Diaphragm 3 Weight 4 Spacer 5 Wiring board 7 Depression 8 Boss 9 Silicon gel 10 Silicon oil 11 Housing hole 21 Movable electrode 51 Fixed electrode

Claims (5)

[Claims] An electric charge accumulates in a movable portion of a base member having a receiving hole for movably receiving a weight displaced in response to a force generated by an acceleration, at the opening end surface of the receiving hole, the weight being suspended and supported. For this purpose, a flexible member on which one movable electrode of the two electrodes facing each other is formed is placed, and at a predetermined interval, the other fixed electrode of the two electrodes facing each other to accumulate electric charge is placed on the flexible member. In a capacitive acceleration sensor having a wiring board member provided thereon, damper means for absorbing and attenuating excessive displacement of a movable portion of a flexible member is provided between the accommodation hole and the weight. A capacitance type acceleration sensor characterized by the above-mentioned. 2. The capacitance type acceleration sensor according to claim 1, wherein the damper means faces a concave portion provided at a central position of a bottom of the receiving hole and a bottom of the receiving hole of the weight. A boss protruding from the surface and having a tip portion extending into the recess;
A low-hardness hardener that fills the recess and interferes with the tip of the boss. 3. The capacitive acceleration sensor according to claim 2, wherein the curing agent is a silicone gel. 4. The capacitance type acceleration sensor according to claim 1, wherein the damper means is a viscous liquid having a low kinematic viscosity filled between the accommodation hole and the weight. Capacitive acceleration sensor. 5. The capacitive acceleration sensor according to claim 4, wherein the viscous liquid is silicon oil.