JPH05180612A - Displacement sensor - Google Patents

Abstract

PURPOSE:To obtain a displacement sensor which shows no hysteresis and no deterioration of the detecting accuracy even when it is used in a relatively wide range of temperatures for a long time, having high durability. CONSTITUTION:This sensor is composed of two electrode plates 1a, 1c arranged in parallel to each other and an intermediate electrode plate 1b. One end of a capacitance member 2 is used as a fixed part, 3, and the other end is a movable part 4. Both ends of each of the electrode plates 1, 1 are hinged at 5 so as to move the movable part 4 in parallel to the fixed part 3. Moreover, an additional capacitance is provided by means of an insulating plate (b) so as to improve the linearity of the detecting output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND 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, contact type and non-contact type displacement gauges have been known.

As shown in FIG. 8, the contact type has a structure in which a brush 61 attached to the tip of a pendulum 60 is brought into sliding contact with a resistor 62 to which a constant voltage is applied, and the voltage is divided by the brush 61. The inclination angle is detected by taking out the voltage as the detection output.

On the other hand, in the non-contact type, as shown in FIG. 9, a magnet 71 attached to the tip of a pendulum 70 is used as a magnetoresistive element 72, 7.
3 to be rocked in a non-contact manner so that the magnetoresistive elements 72, 7
The tilt angle is differentially detected from the change in the resistance value of No. 3.

[0005]

In the above contact type displacement meter, the occurrence of hysteresis is unavoidable, and the resistance element and the brush sliding on the resistance element are worn out for many years. There was a problem with detection accuracy and durability.

Further, in the non-contact type displacement meter, such a problem does not occur, but deterioration of magnetic characteristics due to aging of the magnet is apt to occur, there is a problem in detection accuracy and durability, and the magnetoresistive element is a semiconductor. Therefore, the temperature characteristics were poor, and some kind of temperature compensation had to be taken into consideration for use in a wide temperature range.

In view of such a problem, the present invention does not cause hysteresis and does not deteriorate the displacement amount detection accuracy even if it is used for many years or in an environment of a relatively wide temperature range.
It is an object of the present invention to provide a displacement sensor having high durability.

[0008]

In order to achieve the above object, the present invention provides a pair of electrode members arranged to face each other,
At least one of the distance between the pair of electrode members or the facing area is measured by providing a constant capacitance additional capacitance means provided between the pair of electrode members and a signal source for applying an AC voltage to one of the pair of electrode members. It is characterized in that it is attached to the measuring object so as to change non-linearly according to the displacement to be made, and the displacement detection result is output as the other potential of the pair of electrode members.

Here, one end of each of the pair of electrode members is coupled to the object to be measured by a first hinge movable in the displacement direction to be measured, and an atmosphere is formed between the other ends of each of the pair of electrode members. In contrast, the additional capacitance means is formed by interposing a material having a high dielectric constant, and the constituent portion of the additional capacitance means is connected to the intermediate portion of the pair of electrode members by the second hinge movable in the displacement direction. Preferably.

Further, according to the present invention, the first and second electrode members are arranged so as to face each other, and the third electrode member is arranged between the first and second electrode members so as to face them. And between the first and third electrode members, and between the second and third electrode members
A constant capacitance additional capacitance means provided between the electrode members of
A signal source for applying an AC voltage between the first and second electrode members, and at least one of the distance or the facing area between the first and third electrode members and between the second and third electrode members is measured. It is characterized in that it is attached to the object to be measured so as to change non-linearly according to the displacement to be made, and the displacement detection result is output as the potential of the third electrode member.

In this case, one end of each of the first, second and third electrode members is connected to the object to be measured by the first hinge movable in the displacement direction to be measured, and the first and second electrodes are connected. It is preferable that the first hinge connection position of the member and the third electrode member are different in the displacement direction. On the other hand, the first,
The additional capacitance means is configured by interposing a material having a higher dielectric constant than the atmosphere between the other ends of the second and third electrode members, and the constituent portion of the additional capacitance means is movable in the displacement direction. It is also preferred that it is connected to the intermediate parts of the first, second and third electrode members by means of two hinges.

[0012]

By the displacement to be measured, for example, the electrode members arranged in parallel are tilted while maintaining the parallel state with each other, and accordingly, the distance between the electrode members and the facing area are changed. as a result,
Since the capacitance between the electrode members changes, if an AC voltage is applied to a certain electrode member, the displacement amount can be detected by the potential of another electrode member. That is, if the capacitance type sensor is composed of 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 direction with respect to the hinges of the electrode members on both sides thereof, the displacement is Due to the tilting of these electrode members, one of the facing distance of the electrode member on the one side and the facing distance of the electrode member on the other side with respect to the intermediate electrode member decreases when one decreases.

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

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A displacement gauge 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 arranged in parallel with each other to form a capacitance member 2.
Is configured. Both ends of both electrode plates 1 and 1 are laminated and fixed by an adhesive or the like while sandwiching the insulating plate 6. Then, one end of the capacitance member 2 is used as the fixed portion 3 and the other end is used as the movable portion 4, and the hinges 5 and 5 are provided at both ends of each electrode plate 1 so that the movable portion 4 can move in parallel to the fixed portion 3. 5 are provided. The hinges 5 are provided so as to contact the lower surface of the fixed portion 3 and the upper surface of the movable portion 4, respectively, whereby a so-called parallel link mechanism is formed on both electrodes 1, 1. Further, electrode terminals 7, 7 connected to the electrode plates 1, 1 are provided on the upper surface of the fixed portion 3,
One is a power supply terminal and the other is an output terminal.

In the above structure, the hinges 5 at both ends are
The distance between the two electrode plates 1 and 1 and the effective facing area between the electrodes 5 are L ₁ and S _1, and the electrode plate distances outside the hinges 5 and 5, that is, in the fixed portion 3 and the movable portion 4 of the capacitance member 2 and When 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 the dielectric constant of vacuum, and ε _S is the relative dielectric constant of the insulating plate 6. Here, when the movable part 4 is displaced with respect to the fixed part 3 and the electrode plates 1, 1 are tilted by an angle ψ, the electrode plate interval L ₁ after displacement is L ₀ cos ψ,
The electrostatic capacitance corresponds to the displacement angle ψ and changes according to the above equation.

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

Hereinafter, the case where the present invention is applied to the inclinometer according to the second embodiment will be described with reference to FIGS. 2 and 3.

In this embodiment, three electrode plates 1a, 1
b, 1c are arranged parallel to each other, and these electrodes 1a, 1c
Both ends of b and 1c are respectively insulated by the insulating plate 6 as in the above embodiment.
The electrostatic capacitance member 2 substantially composed of two capacitors is formed by laminating and fixing the two in a sandwiched state with an adhesive or the like. The electrostatic capacitance member 2 has a fixed portion 3 at its upper end and a movable portion 4 at its lower end. As shown in FIG. 2, the electrostatic capacitance member 2 is vertically hung on the fixed portion 3 to be measured. The bracket 8 is attached to the movable portion 4, while the weight 9 is attached to the movable portion 4.

Further, hinges 5 are provided at both ends of each electrode plate so that the electrode plates 1a, 1b, 1c constitute a parallel link mechanism for moving the movable portion 4 in parallel with the fixed portion 3. ing. In this case, the position of the hinge 5 of the intermediate electrode plate 1b is provided so as to be vertically displaced by a predetermined amount h from the positions of the hinges 5 of the left and right electrode plates 1a and 1c. Thereby, one of the electrode plates 1 associated with the tilting
Regarding the distance between a and 1b and the distance between the other electrode plates 1b and 1c, if one increases, the other decreases, and if one decreases, the other increases (see FIG. 3).

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

On the other hand, each electrode plate 1a, 1b, 1 is attached to the fixed portion 3.
Electrode terminals 7a, 7b, 7c connected to c are provided, the electrode plates 1a, 1c on both the left and right sides are connected to an AC power source 10, and the AC output from the intermediate electrode plate 1b is amplified by an amplifier 11 as shown in FIG.
Amplification is performed by and the detection output of the DC level is taken out through the rectifier 12.

In the above structure, the object to be measured is tilted and the electrode plates 1a, 1b, 1c are caused to function by the weight 9 so that, for example, as shown in FIG.
When tilted to the right 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,
The distance L ₁ between the intermediate electrode plate 1b and the left electrode plate 1a is L ₁ = (L ₀ −h · tan ψ) cos ψ, while the distance L ₂ between the intermediate electrode plate 1b and the right electrode plate 1c. Becomes L ₂ = (L ₀ + h · tan ψ) cos ψ. In this way, the electrode plate 1b having an intermediate h · tan ψ
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
The capacitance between a and the capacitance between the electrode plate 1b and the electrode plate 1c are differentially changed, and the influences on the temperature change and the dielectric constant change are canceled out, and the tilt angle is changed according to the inclination angle. The accurate detection output can be obtained.

By the way, when the hinge 5 is composed of the 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 are caused by the elastic force acting on the hinge 5.
Although the inclination angle ψ of c does not match, assuming that 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, ψ = sin ⁻ The relational expression of ¹ (M / K · L _V · sin θ) is established, and θ can be obtained from the detection output corresponding to ψ.

FIG. 5 shows the change characteristics of the detection output with respect to the tilting angle ψ of the three electrode plates 1a, 1b, 1c. The capacitance between the electrode plates is the outer end side of the hinge 5, that is, the fixed portion 3. When the insulating capacitance (stray capacitance) obtained by the insulating plate 6 of the movable part 4 is not added, the characteristic changes nonlinearly like the line A, but between the electrode plates between the hinges 5 at both ends. By adding a predetermined stray capacitance to the electrostatic capacitance, B
The change characteristic is almost linear like a line.

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

FIG. 6A shows the output; {C ₁ / (C ₁ +
The angle (deg) dependence of C ₂ )} is shown, and the same figure (b) shows its linearity [% FS]. In the figure, curve A has an additional stray capacitance of 50 pF, curve B has no additional stray capacitance, and curves E and F each have an additional stray capacitance of 90 pF.
F, 110 pF. It can be understood that the addition of the stray capacitance can make the nonlinear change close to linear.

The same applies to FIGS. 7 (a) and 7 (b). The curve A is a curve B when the added stray capacitance is 50 pF by using a polyimide film (ε _S = 3.5).
Indicates the case where a stray capacitance of 30 pF was added by using a Teflon film (ε _S = 2.2). Curve C is the case where the stray capacitance is assumed to be 15 pF, and curve D is 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 due to acceleration, and the displacement gauge of the present invention can be used as an acceleration sensor. it can. Also, by attaching the movable part to an object that moves relative to the fixed part,
It can also be used as a linear position 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 are tilted while maintaining the parallel state with each other. Since the capacitance of the electrode changes, if an AC voltage is applied to a certain electrode member, the displacement amount can be detected by the potential of another electrode member. Further, if the capacitance member is composed of three electrode members and the hinge of the intermediate electrode member is 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, these will not be accompanied by the displacement. Due to the tilting of the electrode member, the electrostatic capacitance between the intermediate electrode member and the electrode member on one side and the electrostatic capacitance between the electrode member on the other side and the electrode member on the other side increase or decrease, and Connect the electrode member to the AC power supply,
By extracting the detection output from the intermediate electrode member, these changes can be differentially detected, and an accurate detection output temperature-compensated can be obtained. In this case, since the change in capacitance is non-linear (for example, sinusoidal) with respect to the displacement to be measured, the linear output voltage can be detected by disposing the additional capacitance.

Further, since the displacement is detected by the change in the capacitance caused by the change in the distance between the electrode members and the facing area,
Unlike the contact type, there is no hysterine generation, there is no deterioration in durability and detection accuracy due to wear, and since it does not use semiconductors such as magnets and magnetoresistive elements like the conventional non-contact type displacement gauge, detection by change over time There is no deterioration in accuracy and there is an effect that it can be used in a wide temperature range.

[Brief description of 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 side view of cutting when the hinge is changed in the embodiment of FIG.

FIG. 4 is a circuit diagram showing a detection circuit applied to the embodiments of FIGS.

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

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

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

FIG. 8 is a structural diagram showing a conventional contact type displacement meter.

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

[Explanation of symbols]

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

Claims (5)

[Claims] 1. A pair of electrode members arranged to face each other, an additional capacitance means having a constant capacitance provided between the pair of electrode members, and a signal for applying an AC voltage to one of the pair of electrode members. And a source, the distance between the pair of electrode members, or at least one of the facing areas is attached to a measurement object so as to change non-linearly according to the displacement to be measured, and the detection result of the displacement is the pair of electrode members. The displacement sensor is characterized in that it is output as the other potential of the displacement sensor. 2. One end of each of the pair of electrode members is coupled to the measurement object by a first hinge movable in a displacement direction to be measured, and the other end of each of the pair of electrode members is connected. The additional capacitance means is formed by interposing a material having a higher dielectric constant than that of the atmosphere, and the constituent portion of the additional capacitance means is formed by a second hinge movable in the displacement direction and an intermediate portion of the pair of electrode members. The displacement sensor according to claim 1, which is coupled. 3. A first electrode member and a second electrode member which are arranged to face each other, a third electrode member which is arranged between the first electrode member and the second electrode member so as to face them, and A signal source for applying an AC voltage between the first and second electrode members and a constant capacitance additional capacitance means provided between the first and third electrode members and between the second and third electrode members. And a distance between the first and third electrode members and between the second and third electrode members, or at least one of the facing areas, changes non-linearly according to the displacement to be measured. A displacement sensor that is attached and outputs the displacement detection result as the potential of the third electrode member. 4. One end of each of the first, second and third electrode members is connected to the measurement object by a first hinge movable in a displacement direction to be measured, and the first and second electrodes are connected. 4. The displacement sensor according to claim 3, wherein the first hinge connection position of the third electrode member and the third electrode member differ in the displacement direction. 5. The additional capacitance means is configured by interposing a material having a higher dielectric constant than the atmosphere between the other ends of the first, second and third electrode members, and the additional capacitance is formed. 5. Displacement sensor according to claim 4, wherein the component parts of the means are connected to the intermediate parts of the first, second and third electrode members by means of a second hinge movable in the displacement direction.