JP3022671B2 - Displacement sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, an inclination angle of an object,
The present invention relates to a capacitance type displacement sensor used for detecting displacement such as acceleration and position.

[0002]

2. Description of the Related Art Conventionally, a contact type and a non-contact type are known as displacement meters for inclination angles.

The contact type has a structure in which a brush 61 attached to the tip of a pendulum 60 is slidably contacted with a resistor 62 to which a constant voltage is applied as shown in FIG. The inclination angle is detected by extracting the voltage as a detection output.

On the other hand, in a non-contact type, as shown in FIG.
3 and are oscillated in a non-contact manner along the magnetoresistive elements 72 and 7.
The inclination angle is differentially detected from the change in the resistance value of No. 3.

[0005]

In the above-mentioned contact type displacement meter, the occurrence of hysteresis is inevitable, and the resistor and the brush which is in sliding contact with the resistor are worn due to long-term use. There were problems in detection accuracy and durability.

In the non-contact type displacement meter, such a problem does not occur, but the magnetic characteristics are easily deteriorated due to aging of the magnet, and there are problems in detection accuracy and durability. Therefore, the temperature characteristics are poor, and some temperature compensation must be considered for use in a wide temperature range.

[0007] In view of the above problems, the present invention does not cause hysteresis and does not deteriorate the displacement detection accuracy even when used for a long time and in an environment in a relatively wide temperature range.
It is an object of the present invention to provide a highly durable displacement sensor.

[0008]

In order to achieve the above object, the present invention comprises a pair of electrode members arranged opposite to each other,
An additional capacitance means having a constant capacitance provided between the pair of electrode members, and a signal source for applying an AC voltage to one of the pair of electrode members, wherein the pair of electrode members have a distance between them and a facing area. One end side is tiltably held and attached to the object to be measured so that at least one of them changes nonlinearly according to the displacement to be measured, and the detection result of the displacement is output as the other potential of the pair of electrode members. It is characterized by.

Here, one end of each of the pair of electrode members is connected to the object to be measured by a first hinge movable in the direction of displacement of the inclination angle to be measured, and between the other end of each of the pair of electrode members. The additional capacitance means is constituted by interposing a material having a higher dielectric constant than the atmosphere, and the constituent part of the additional capacitance means is connected to the intermediate part of the pair of electrode members by the second hinge movable in the displacement direction. Is preferred.

The present invention is also directed to a first and a second electrode member disposed opposite each other, and a third electrode member disposed between the first and second electrode members so as to face the first and second electrode members. And between the first and third electrode members and between the second and third electrode members.
An additional capacitance means having a constant capacitance provided between the electrode members of
A signal source for applying an AC voltage between the first and second electrode members, wherein the first, second, and third electrode members have a first
One end is held so as to be tiltable so that at least one of the distance between the third electrode member and the distance between the second and third electrode members and the opposing area changes non-linearly in accordance with the displacement to be measured. It is attached to an object, and a detection result of the displacement is output as a potential of the third electrode member.

In this case, one end of each of the first, second and third electrode members on the same side is connected to the object to be measured by a first hinge movable in a direction of displacement of the inclination angle to be measured, It is preferable that the first and second electrode members and the third first hinge connection position are different in the displacement direction. On the other hand, the additional capacitance means is configured by interposing a material having a higher dielectric constant than the atmosphere between the other end portions of the first, second, and third electrode members, and the constituent parts of the additional capacitance means It is also preferable that the first, second and third electrode members are connected to an intermediate portion by a second hinge movable in the displacement direction.

[0012]

According to the displacement to be measured, for example, the electrode members arranged in parallel tilt while keeping the parallel state, and the distance between the electrode members and the facing area change accordingly. as a result,
Since the capacitance between the electrode members changes, if an AC voltage is applied to a certain electrode member, the amount of displacement is detected by the potential of another electrode member. In other words, if the capacitance type sensor is composed of three electrode members, and the hinge of the intermediate electrode member is displaced in the direction orthogonal to the displacement direction with respect to the hinges of the electrode members on both sides, the displacement is increased. Due to the tilting of these electrode members, the facing distance of the electrode member on one side with respect to the intermediate electrode member and the facing distance of the electrode member on the other side decrease and increase the other.

This is equivalent to an increase or decrease in the capacitance between the intermediate electrode member and the one-side electrode member and the capacitance between the intermediate electrode member and the other-side electrode member. In other words, by connecting the electrode members on both sides to an AC power source and taking out the detection output from the intermediate electrode member, these changes can be detected differentially, and an accurate temperature-compensated detection output can be obtained. In this case, since the change in the capacitance is non-linear (for example, sinusoidal) with respect to the displacement to be measured, a linear output voltage can be detected by providing the additional capacitance.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A displacement meter according to a first embodiment of the present invention will be described with reference to FIG. Two electrode plates 1 and 1 made of a conductive material are disposed in parallel with each other to form a capacitance member 2.
Is configured. Both ends of the two electrode plates 1 and 1 are laminated and fixed with an adhesive or the like with the insulating plate 6 interposed therebetween. One end of the capacitance member 2 is a fixed part 3, and the other end is a movable part 4, and hinges 5 are provided at both ends of each electrode plate 1 so that the movable part 4 can move parallel to the fixed part 3. 5 are provided. Each hinge 5 is provided so as to be in contact with the lower surface of the fixed portion 3 and the upper surface of the movable portion 4, thereby forming a so-called parallel link mechanism between the electrodes 1 and 1. Further, electrode terminals 7, 7 connected to the electrode plates 1, 1 are provided on the upper surface of the fixing portion 3,
One is a power terminal and the other is an output terminal.

In the above configuration, the hinges 5 at both ends are provided.
5, the distance between the two electrode plates 1 and 1 and the effective facing area are defined as L ₁ and S _1. Assuming that the effective facing area is L ₀ and S ₀ , the capacitance C of the capacitance member 2 is represented by C = ε ₀ (S ₁ / L ₁ + ε _S · S ₀ / L ₀ ). Here, ε ₀ is a dielectric constant in a vacuum, and ε _S is a relative dielectric constant of the insulating plate 6. Here, when the movable portion 4 is displaced with respect to the fixed portion 3 and the electrode plates 1 and 1 are tilted by the angle ψ, the electrode plate interval L ₁ after the displacement becomes L ₀ cosψ,
The capacitance changes according to the above equation according to the displacement angle ψ.

Therefore, the movable portion 4 is provided with a pin (not shown).
If the object is displaced in accordance with the displacement of the object to be measured, the displacement of the object can be measured by a change in the capacitance C. Also, by attaching the weight 9 to the movable part 4,
The inclination angle of the fixed part 3 with respect to the direction of gravity can also be measured. Further, an additional stray capacitance C ₀ = ε ₀ · ε _s · S formed by the interposition of the insulating plate 6 having a relative permittivity ε _s.
0 / L ₀ serves to improve the non-linearity of the output voltage and provide a linear output. Such an effect is particularly remarkable in a second embodiment described later.

Hereinafter, a case where the present invention is applied to an inclinometer according to a second embodiment will be described with reference to FIGS.

In this embodiment, three electrode plates 1a, 1
b, 1c are arranged in parallel with each other, and these electrodes 1a, 1c
b, 1c at both ends in the same manner as in the above embodiment.
Are sandwiched and laminated by an adhesive or the like, thereby forming a capacitance member 2 substantially composed of two capacitors. This capacitance member 2 is configured such that its upper end is a fixed part 3 and its lower end is a movable part 4, and as shown in FIG. Bracket 8 is attached, while a weight 9 is attached to the movable part 4.

Hinges 5 are provided at both ends of each of the electrode plates 1a, 1b and 1c so that a parallel link mechanism for moving the movable portion 4 in parallel with the fixed portion 3 is constituted by these electrode plates 1a, 1b and 1c. ing. In this case, the position of the hinge 5 of the intermediate electrode plate 1b is shifted vertically by a predetermined amount h from the position of the hinge 5 of the left and right electrode plates 1a, 1c. Thereby, one electrode plate 1 accompanying the tilting
The distance between a and 1b and the distance between the other electrode plates 1b and 1c are such that if one increases, the other decreases, and if one decreases, the other increases (see FIG. 3).

Each hinge 5 is constituted by an elastic and bendable bent portion integrally formed with the electrode plates 1a, 1b, 1c. The bent portion may be formed by processing a part of the member like a long hole shown in FIG. 2 or a thin portion shown in FIG. You may comprise a bending part.

On the other hand, each electrode plate 1a, 1b, 1
c, electrode terminals 7a, 7b, 7c are provided, and the left and right electrode plates 1a, 1c are connected to an AC power source 10 as shown in FIG.
And a DC level detection output is taken out via the rectifier 12.

In the above configuration, the object to be measured is inclined and the electrode plates 1a, 1b, 1c are operated by the weight 9 so that, for example, FIG.
Is tilted rightward by an angle ψ as shown by the imaginary line, due to the displacement amount h of the position of the hinge 5 of the intermediate electrode plate 1b,
Distance L ₁ between the intermediate electrode plate 1b and the left electrode plate 1a _{is, L 1 = (L 0 -h} · tanψ) cosψ . On the other hand, the distance between the intermediate electrode plate 1b and the right side of the electrode plate 1c L ₂ Is L ₂ = (L ₀ + h · tan {) cos}. Thus, h · tan ・ is an intermediate electrode plate 1b
To become a sign reversed between the distance L ₂ of the distance L ₁ and the right electrode plate 1c of the left electrode plate 1a with respect to the electrode plate 1b and the electrode plate 1
a and the capacitance between the electrode plate 1b and the electrode plate 1c change differentially, and the influence on the temperature change and the change in the dielectric constant is canceled out. Thus, an accurate detection output can be obtained.

When the hinge 5 is constituted by a bent portion which can be elastically bent as described above, the inclination angle θ of the object to be measured and the electrode plates 1a, 1b, 1
Although the inclination angle の of c does not coincide, the spring constant of the hinge 5 is K, the distance between the hinges at both ends is L _V , and the weight of the weight 9 is M, and between ψ and θ, ψ = sin ^{− 1} relation is satisfied for _{(M / K · L V ·} sinθ), can be obtained θ from the detection output corresponding to [psi.

FIG. 5 shows a change characteristic of the detection output with respect to the tilt angle の of the three electrode plates 1a, 1b, 1c. When the insulating capacitance (floating capacitance) obtained by the insulating plate 6 of the movable part 4 is not added, the characteristic changes nonlinearly like the A line, but between the electrode plates between the hinges 5 at both ends. By adding a predetermined stray capacitance to the capacitance, B
It has a substantially linear change characteristic like a line.

6 and 7 show measured values of the change characteristics. In each case, the capacitance at zero point excluding the additional capacitance as the stray capacitance is 42.5 pF. The spring coefficient of the hinge was 0.6 in the example of FIG. 6 and 0.8 in the example of FIG. 7, and was obtained as a tilt angle sensor of ± 65 deg.

FIG. 6A shows an output; ΔC ₁ / (C ₁ +
C ₂ )｝ shows the angle (deg) dependency, and FIG. 2B shows the linearity [% FS]. In the figure, the curve A is when the additional stray capacitance is 50 pF, the curve B is when there is no additional stray capacitance, and the curves E and F are respectively when the additional stray capacitance is 90 pF.
F, 110 pF. It can be understood that by adding the stray capacitance, the nonlinear change can be made closer to linear.

The same applies to FIGS. 7 (a) and 7 (b). Curve A is obtained by using a polyimide film (ε _S = 3.5), and when the additional floating capacitance is 50 pF, the curve B
Shows a case where a stray capacitance of 30 pF is added by using a Teflon film (ε _S = 2.2). Curve C shows the case where the stray capacitance is 15 pF, and curve D shows the case where there is no additional stray capacitance. Also in this case, it can be seen that the detection characteristic can be made linear.

Further, by applying an elastic force to the hinge 5, the electrode plate can be tilted at an angle corresponding to the force acting on the movable portion by acceleration, and the displacement meter of the present invention can be used as an acceleration sensor. it can. Also, by attaching the movable part to the object that moves relatively to the fixed part,
It can also be used as a linear displacement sensor.

[0029]

As is apparent from the above description, according to the present invention, due to the displacement to be measured, the electrode members arranged in parallel tilt while maintaining the parallel state with each other. Since the capacitance of the electrode member changes, if an AC voltage is applied to a certain electrode member, the displacement amount is detected based on the potential of another electrode member. Further, if the capacitance member is constituted by three electrode members, and the hinges of the intermediate electrode members are provided so as to be displaced in the direction orthogonal to the displacement with respect to the hinges of the electrode members on both sides thereof, it is possible to reduce the displacement due to the displacement. Due to the tilting of the electrode members, the capacitance between the intermediate electrode member and the electrode member on one side and the capacitance between the intermediate electrode member and the electrode member on the other side increase or decrease. Connect the electrode members to an AC power supply,
By extracting the detection output from the intermediate electrode member, these changes can be detected differentially, and an accurate temperature-compensated detection output can be obtained. In this case, since the change in the capacitance is non-linear (for example, sinusoidal) with respect to the displacement to be measured, a linear output voltage can be detected by providing the additional capacitance.

Further, in order to detect a displacement based on a change in capacitance due to a change in the distance between the electrode members and a facing area,
Unlike contact type, there is no occurrence of hysteresis, there is no deterioration of durability and detection accuracy due to abrasion, and since it does not use semiconductors such as magnets and magnetoresistive elements unlike conventional non-contact type displacement gauges, detection by aging changes There is no deterioration in accuracy and there is an effect that it can be used in a wide temperature range.

[Brief description of the drawings]

FIG. 1 is a side view of a displacement meter according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a displacement meter according to a second embodiment of the present invention.

FIG. 3 is a cut-away side view when the hinge is changed in the embodiment of FIG. 2;

FIG. 4 is a circuit diagram showing a detection circuit applied to the embodiment of FIGS. 2 and 3;

FIG. 5 is a change characteristic diagram of a detection output.

FIG. 6 is an actual measurement diagram showing the angle dependence of a detection output.

FIG. 7 is an actual measurement diagram showing linearity of a detection output.

FIG. 8 is a structural view showing a conventional contact displacement meter.

FIG. 9 is a structural diagram showing a conventional non-contact displacement meter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode plate, 2 ... Capacitance member, 3 ... Fixed part, 4 ... Movable part, 5 ... Hinge, 9 ... Weight

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-145901 (JP, A) JP-A-1-165920 (JP, A) JP-A 3-122319 (JP, U) JP-A 62-145 193536 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B ^7/ 00-7/34

Claims (5)

(57) [Claims] 1. A pair of electrode members arranged to face each other, an additional capacitance means having a constant capacity provided between the pair of electrode members, and a signal for applying an AC voltage to one of the pair of electrode members. A pair of electrode members, at least one of a distance between them and an opposing area is non-linearly changed in accordance with a displacement to be measured, and one end side is held to be tiltable and attached to a measurement target. A displacement sensor, wherein the detection result of the displacement is output as the other potential of the pair of electrode members. 2. One end of each of the pair of electrode members is coupled to the object to be measured by a first hinge movable in a displacement direction of a tilt angle to be measured, and the other end of each of the pair of electrode members is provided. The additional capacitance means is constituted by interposing a material having a higher dielectric constant than the atmosphere between the portions, and the constituent part of the additional capacitance means is formed by a second hinge movable in the displacement direction. 2. The displacement sensor according to claim 1, wherein the displacement sensor is connected to an intermediate part. A first and a second electrode member disposed opposite to each other; a third electrode member disposed between the first and second electrode members so as to face the first and second electrode members; Between the first and third electrode members and the second and third electrode members;
And a signal source for applying an AC voltage between the first and second electrode members, wherein the first, second and third electrode members are provided. One end can be tilted so that at least one of the distance and the facing area between the first and third electrode members and between the second and third electrode members changes non-linearly according to the displacement to be measured. A displacement sensor that is held and attached to an object to be measured, and the detection result of the displacement is output as a potential of the third electrode member. 4. One end of each of the first, second, and third electrode members is coupled to the object by a first hinge movable in a displacement direction of a tilt angle to be measured, and
4. The displacement sensor according to claim 3, wherein the second electrode member and the third first hinge coupling position are different in the displacement direction. 5. 5. The additional capacitance means is constituted by interposing a material having a higher dielectric constant than the atmosphere between the other end of each of the first, second and third electrode members. 5. The displacement sensor according to claim 4, wherein a component part of the means is connected to an intermediate portion between the first, second and third electrode members by a second hinge movable in the displacement direction.