JP3240390B2 - Displacement detection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a vibration sensor,
The present invention relates to a displacement sensor applied to a pressure sensor, a seismic sensor, and the like.

[0002]

2. Description of the Related Art Conventionally, as this kind of displacement detection sensor,
For example, as shown in Japanese Patent Application Laid-Open No. 2-95263, a slit is formed in a plate-shaped piezoelectric element, and a portion surrounded by the slit is a cantilever-type vibrator. Is fixedly supported by a fixing member.

Another conventional example is disclosed in, for example,
As disclosed in Japanese Patent Application Laid-Open No. 4-18063, a displaceable weight formed at the center of a semiconductor substrate is supported by a substrate via a cantilever, and a strain gauge is attached to the cantilever. A configuration is known in which a displacement such as an acceleration is detected from a change in the resistance value of the strain gauge.

[0004]

The above displacement sensors are:
Because the movable part that detects displacement is a structure supported by a cantilever, the sensitivity to minute external stress is insufficient, and the displacement direction is not constant for displacement due to large stress. Unless a correction circuit is provided, accurate detection cannot be performed. Therefore, the displacement detection range is limited to a narrow range, and the versatility is poor. In addition, the cost of the piezoelectric or semiconductor type is high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a simple structure and low cost, and can perform displacement detection with high sensitivity over a wide range from small stress to large stress. An object of the present invention is to provide a displacement detection sensor that can always obtain a stable detection output.

Another object of the present invention is to provide a displacement detection sensor which can be applied to a displacement detection sensor, a fluid pressure sensor, a seismic sensor and the like with low cost and high detection accuracy.

[0007]

In order to achieve the above object, a displacement detecting sensor according to a first aspect of the present invention has a movable portion displaced by external stress, with respect to a support frame disposed around the movable portion. The movable portion is displaceably held through a plurality of spring portions formed in a meandering arm piece on the same plane as the movable portion. The displacement detecting means is provided with the movable spring as one electrode, a weight is attached to the center of the movable portion of the electrode, and the center of displacement is located above the movable portion. The other electrode having a fulcrum for regulating the vertical displacement of the electrode is disposed at a position facing the movable portion, and only displacement in all horizontal directions is detected as a change in capacitance between the two electrodes. Like Characterized in that it was.

[0008]

According to the first aspect of the present invention, when an external stress is applied, the movable portion is displaced via a plurality of spring portions arranged axially or line-symmetrically with respect to the center axis. However, at this time, since each spring portion is formed in a meandering arm piece shape, it is possible to displace with good response to a small stress while having a small occupation area, and it is possible to take a large displacement amount for a large stress. The detection sensitivity can be improved and the detection range can be expanded. Further, since the movable portion is always displaced in parallel along the direction in which the stress acts, a stable output can be obtained without adding a complicated correction circuit or the like. As a result, the applicability of the movable spring to various sensors, that is, the versatility is enhanced, and the structure of the sensor using the movable spring can be simplified and the cost can be reduced. Furthermore, it is possible to configure a displacement sensor with high detection accuracy while reducing the number of parts, simplifying the structure, and reducing the cost.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a basic structure of a movable spring for a displacement detection sensor according to the present invention. In FIG. 1, reference numeral 1 denotes a substantially square plate, and the plate 1 is formed by an external stress such as vibration acceleration or pressure. The movable part 2 displaced in the direction perpendicular to the plane is a fixed support frame arranged in an annular rectangular shape so as to surround the periphery of the movable part 1, and the four sides of the movable part 1 and the four Between the side and the movable part 1
The movable portion 1 is displaceably held by the fixed support portion 2 via four spring portions 3 arranged axially symmetrically with respect to the central axis of the movable member 1. Each of the spring portions 3 has a substantially U-shaped portion 3 a on the same plane as the movable portion 1.
And mounting piece portions 3b, 3 extending integrally from both ends of the open side of the U-shaped portion 3a in a direction perpendicular to each other.
and b.

The movable portion 1, the fixed support frame 2 and the four meandering arm-shaped spring portions 3 may be separately formed and connected to each other. It is advantageous from the viewpoint of mass productivity that a series of integrated production is performed by injection molding, etching of a metal material such as stainless steel, pressing, or etching of a semiconductor crystal plate of silicon or the like.

Although the above-mentioned spring portions 3 are formed on the four sides of the movable portion 1 and the fixed support frame 2, respectively, the number of the spring portions 3 is eight, that is, two on each side. The operation can be made more stable.

According to the movable spring for a displacement detection sensor having the above configuration, when an external force F is applied to the movable portion 1, the movable portion 1 is displaced via the four spring portions 3.
At this time, since each of the spring portions 3 is formed in a meandering arm piece shape, the movable portion 1 is displaced with good response to a small stress while having a small occupied area, and sufficient for a large stress. A large displacement can be obtained.
Further, the movable portion 1 is stably displaced in a direction perpendicular to the plate surface.

Further, the material of the spring portion 3 is not particularly limited. However, when any material is used within the proportional limit of the material, there is no change in the spring characteristics, and the performance of various sensors can be improved. Stabilization can be achieved.

FIG. 2 shows the structure of the spring portion 3 in the direction of arrow A in FIG. 1. When an external force F is applied to the movable portion 1, aa-a
A cantilever having a span of (1/2) is formed between 1, 1, b-b1, and b1-c. Here, since the external force applied to one side of the movable spring is (F / 4), a force of (F / 4) is applied to the cantilever. Therefore, the spring constant and the like of the spring portion 3 can be determined by designing the basic cantilever.

FIG. 3 is an exploded perspective view of a capacitance type two-dimensional displacement detecting sensor constituted by using the movable spring 4, and FIG. 4 is an explanatory view of the operation of the sensor. In this capacitance type two-dimensional displacement detection sensor, the movable spring 4 is used as one electrode, and a weight 52 is attached to the center of the movable part 1 of the electrode 4 so that the center of gravity g of the displacement is set in the movable part. 1. A fulcrum 56 made of an insulating material for regulating the vertical displacement of the electrode 4 is provided at a central portion of the fulcrum 56 so that the fulcrum 56 is located at a center thereof. The electrodes 57 for detecting the capacitance in the horizontal two-dimensional directions x and y are provided so that the movable electrodes 1 having the weights 52 are displaced in the horizontal two-dimensional directions x and y.
In this case, a displacement amount such as vibration is detected by a change in capacitance between the two-dimensional displacement detection sensors.
Is represented by the following equation: C = ε0 · (s / α) where ε0: dielectric constant, s: electrode area, and α: gap dimension. The electrode 57 used in this embodiment may be one in which a pattern is formed on the surface of the PWB with a conductive paint or the like.

FIGS. 5 to 8 show examples of a circuit for detecting vibration by the above-mentioned capacitance type displacement detection sensor.
Is used as the capacitance of the CR oscillating unit 10 and the periods T, T ⁻ , T ⁺ of the oscillation output fout waveform that change between the stationary state and the occurrence of the vibration, as shown in FIG. , And the arithmetic unit 12 calculates the differences Δt ⁻ and Δt ⁺ between the measured periods T, T ⁻ and T ⁺ ,
Vibration acceleration is obtained and detected as a capacitance that changes with vibration. FIG. 6 shows a case where a plurality of semiconductor switches 14a and 14a are used as capacitances of a switch capacitor circuit 13 (hereinafter, referred to as an SC circuit).
b, the change in capacitance output in response to the switching timing clocks Φ1 and Φ2 output from the timing generation circuit 14 composed of b is converted into a voltage change by the FV converter 15, thereby obtaining the vibration acceleration Vout. A
After being converted to a digital value through the / D converter 16,
The signal processing operation section 17 performs waveform processing to obtain a predetermined output.

FIG. 7 shows the CR oscillation section 10 shown in FIG.
And an FV converter 15, and the output V0 of the FV converter 15 is passed through a low-pass filter 18 as necessary, then A / D converted by an A / D converter 16, and is subjected to signal processing calculation. The waveform is processed by the unit 17 to obtain a predetermined output.
The oscillation output fou is used as the capacitance of the oscillation circuit 19.
t is obtained through a circuit having the same configuration as that shown in FIG. 5A or FIG. 7A, and in any case, a low-cost sensor with a simple structure is provided. Can be realized.

[0018]

As described above, according to the present invention, the spring portion displaced by external stress is formed in a meandering arm piece shape, and this spring portion is axially symmetric or line symmetric with respect to the center axis of the movable portion. By setting the length, thickness and width of the beam constituted by each spring part arbitrarily, the movable spring as a whole is simple in structure and low cost, while responding to minute stress. The displacement can be sufficiently increased, and the displacement for a large stress can be made sufficiently large, so that the detection sensitivity can be improved and the detection range can be expanded for a small occupied area. In addition, since the movable part is always displaced in parallel along the direction in which the stress is applied, a stable output can be obtained without adding a complicated correction circuit, etc., and therefore, applicability to various sensors, that is, versatility Can be remarkably increased, and the structure of a sensor using the sensor can be simplified and the cost can be reduced.
In addition, there is no need for a complicated correction circuit to correct for linear displacement, and the number of parts is reduced, simplifying the structure and lowering the cost. Can be detected very accurately.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a structure applied to a movable spring for a displacement detection sensor according to the present invention.

FIG. 2 is an enlarged view of a main part for describing a structure of a spring portion in a direction A in FIG. 1;

FIG. 3 is an exploded perspective view of a capacitance type two-dimensional displacement detection sensor configured using the movable spring.

FIG. 4 is an explanatory diagram of an operation of the sensor.

FIG. 5 is a diagram illustrating an example of a vibration detection circuit using a capacitance type displacement detection sensor, which is used as a capacitance of a CR oscillation unit.

FIG. 6 is a diagram illustrating one example of a vibration detection circuit using a capacitance type displacement detection sensor, which is used as a capacitance of an SC circuit.

FIG. 7 is a diagram illustrating an example of a vibration detection circuit using a capacitance type displacement detection sensor, in which a CR oscillation unit and an FV converter are used in combination.

FIG. 8 is a diagram illustrating an example of a vibration detection circuit using a capacitance type displacement detection sensor, which is used as a capacitance of an LC oscillation circuit.

[Explanation of symbols]

 Reference Signs List 1 movable part 2 support frame 3 spring part 4 movable spring 52 weight 56 fulcrum 57 electrode

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-32777 (JP, A) JP-A-54-150156 (JP, A) JP-A-2-151770 (JP, A) JP-A 61- 231424 (JP, A) JP-A-59-99356 (JP, A) JP-A-4-19568 (JP, A) JP-A-1-201103 (JP, A) Japanese Utility Model Publication No. 57-638 (JP, U) JP-A 1-127263 (JP, U) JP 3-122367 (JP, U) JP 30-18495 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 1/00-1/22 G01P 15/00-15/125

Claims (1)

(57) [Claims] 1. A movable part displaced by an external stress is arranged axially symmetrically or line-symmetrically with respect to a center axis of the movable part with respect to a support frame arranged around the movable part, and each of the planes is the same as the movable part. A plurality of spring portions formed in a meandering arm piece above are held so as to be displaceable, and a means for detecting the displacement is provided. The displacement detection means uses the movable spring as one electrode, and A weight is attached to the center of the movable part to position the center of gravity of the displacement above the movable part, and has a fulcrum for regulating the vertical displacement of the electrode at a position facing the movable part. A displacement detection sensor, wherein only the displacement in all horizontal directions is detected as a change in capacitance between the two electrodes.