TW201423051A - Capacitive displacement sensor - Google Patents

Abstract

A capacitive displacement sensor comprises: a columnar member formed from an insulating material; a metal cylindrical member into which a prescribed region of the columnar member is inserted and that moves in association with displacement of a spool; a pair of stationary electrodes formed into a thin film on the outer surface of the columnar member; compensation electrodes formed into a thin film on the outer surface of the columnar member; an electrostatic shield that is grounded, and, in a state of being insulated from the stationary electrodes, cylindrical member, and the compensation electrodes, covers the electrodes; and stationary electrode terminals and compensation electrode terminals that are formed into a thin film on the outer surface of the columnar member, and that extend in a state of being insulated from the electrostatic shield, in the lengthwise direction, to the exterior of the electrostatic shield contacting the each electrodes.

Description

Electrostatic displacement sensor Field of invention

The present invention relates to a capacitance type displacement sensor including a pair of fixed electrodes and a movable electrode opposed to the pair of fixed electrodes.

Background of the invention

Heretofore, in such a displacement sensor, one of the pair of semi-cylindrical fixed electrodes is disposed outside the cylindrical movable electrode, and the displacement of the valve body connected to the movable electrode is measured ( For example, refer to Patent Document 1). In the displacement sensor described in Patent Document 1, the electrostatic capacitance between the pair of fixed electrodes is changed by the movable electrode moving in the axial direction, and the change of the valve body is measured from the change in the electrostatic capacitance. Bit.

Further, in the displacement sensor described in Patent Document 1, a dielectric fluid is introduced between the movable electrode and the fixed electrode, and a pair of compensation electrodes are opposed to each other and disposed at a portion where the dielectric fluid flows. Then, the electrostatic capacitance between the pair of compensation electrodes is measured to compensate for the measurement error of the displacement due to the change in the dielectric constant of the dielectric fluid.

Further, in the displacement sensor described in Patent Document 1, the movable electrode is covered with a metal electrostatic shield in a state of being electrically insulated. And fixing the electrode, and electrically grounding the electrostatic shield. Therefore, even if the user touches the body of the sensor (including the valve device body of the sensor), it is possible to suppress the electrostatic capacitance between the pair of fixed electrodes from becoming unstable.

Prior technical literature Patent literature

[Patent Document 1] WO2012/090583A1

Summary of invention

In the displacement sensor described in Patent Document 1, it is necessary to arrange a pair of semi-cylindrical fixed electrodes on the outside of the cylindrical movable electrode. However, it is not an easy matter to arrange the pair of semi-cylindrical fixed electrodes in a correct position at a predetermined interval.

Further, in the displacement sensor described in Patent Document 1, the movable electrode and the fixed electrode are covered with an electrostatic shield in a state of being electrically insulated. Therefore, the fixed electrode or the compensation electrode must be pulled out to the outside of the electrostatic shield by wiring or a pin or the like. Therefore, it is unavoidable that the structure in which the fixed electrode or the compensation electrode is pulled out becomes complicated.

The present invention has been made in view of the above circumstances, and its main object is to enable a pair of fixed electrodes to be accurately arranged at predetermined intervals in an electrostatic capacity type displacement sensor having electrostatic shielding, and to make the electrodes easy. Pull out to the outside of the electrostatic shield.

In order to solve the above problems, the present invention employs the following mechanism.

The first mechanism is an electrostatic capacitance type displacement sensor, comprising: a rod-shaped member having an outer surface portion formed of an insulating material; and a cylindrical member from one end of the longitudinal direction of the rod-shaped member The predetermined range is inserted into the inside, and moves in the longitudinal direction as the measurement target is displaced. The pair of fixed electrodes are formed in a film shape on the outer surface portion of the rod-shaped member, and are opposed to each other with the rod-shaped member interposed therebetween. a movable electrode that is connected to the fixed electrode and the measurement object is provided in the cylindrical member and faces the pair of fixed electrodes; and the compensation electrode is on the outer surface of the rod-shaped member The portion is formed in a film shape and does not face the movable electrode; the electrostatic shield covers the electrodes in a state insulated from the fixed electrode, the movable electrode, and the compensation electrode, and is grounded; and the fixed electrode terminal is in the shape of a rod The outer surface portion of the member is formed in a film shape, and is connected to each of the fixed electrodes to the outside of the electrostatic shield to a state in which the electric shielding insulation extends in the longitudinal direction; and a compensation electrode terminal formed in a film shape on the outer surface portion of the rod-shaped member, and connected to the compensation electrode to the outside of the electrostatic shield to be electrostatically shielded from the electrostatic shielding The insulated state extends toward the aforementioned long direction.

According to the above configuration, the movable electrode that is connected to the pair of fixed electrodes in a state of being insulated from the fixed electrode and the measurement target is provided in the tubular member. Therefore, capacitors are formed between the fixed electrodes and the opposing movable electrodes, and the capacitors are connected in series by a plurality of movable electrodes to form a combined capacitor. Moreover, when the cylindrical member moves toward the longitudinal direction of the rod member as the measurement object is displaced, it is fixed The area of the portion where the electrode faces the movable electrode changes, so the electrostatic capacity of the composite capacitor changes. Therefore, the displacement of the measuring object can be measured in accordance with the change in the electrostatic capacity of the synthetic capacitor, that is, the change in the electrostatic capacitance between the pair of fixed electrodes.

Further, in addition to the pair of fixed electrodes, the compensation electrode that does not face the movable electrode is formed in a film shape on the outer surface portion of the rod-shaped member. Therefore, the capacitance of the compensation capacitor in which the compensation electrode is formed as one electrode is measured, whereby the measurement error of the displacement due to the change in the dielectric constant between the fixed electrode and the movable electrode can be compensated.

Here, the pair of fixed electrodes facing each other with the rod-shaped member interposed therebetween are formed in a film shape on the outer surface portion of the rod-shaped member formed of an insulating material. Therefore, it is not necessary to arrange a pair of fixed electrodes which are formed as different members from each other, and a pair of fixed electrodes can be formed as a film-like pattern on the outer surface portion of one of the rod-shaped members. Therefore, the interval between the pair of fixed electrodes is defined by the size of the rod-shaped member, and a pair of fixed electrodes can be correctly arranged at predetermined intervals.

Further, the fixed electrode, the movable electrode, and the compensation electrode are covered by an electrostatic shield that is insulated from the electrodes. Since the electrostatic shield is grounded, even if the user touches the body of the sensor (the apparatus body including the sensor), the electrostatic capacitance between the pair of fixed electrodes can be suppressed from becoming unstable.

Here, the fixed electrode terminal and the compensation electrode terminal which are connected to the fixed electrode and the compensation electrode to the outside of the electrostatic shield and which are insulated from the electrostatic shield in the longitudinal direction of the rod-shaped member are respectively outside the rod-shaped member. The surface portion is formed into a film shape. Therefore, as long as it is fixed with the electrode The compensation electrode together forms the fixed electrode terminal and the compensation electrode terminal into a film-like pattern, and the fixed electrode and the compensation electrode can be pulled out toward the outside of the electrostatic shield. Therefore, it is easy to pull the electrode toward the outside of the electrostatic shield.

In the second mechanism, the electrostatic shield has a protruding portion that protrudes toward a position toward the compensation electrode.

According to the above configuration, since the protruding portion of the electrostatic shield is close to the compensation electrode, the compensation capacitor having a relatively large electrostatic capacitance can be formed by the compensation electrode and the protruding portion. Therefore, the electrostatic shield can be utilized as an electrode of one of the compensation capacitors, and the accuracy of the compensation capacitor can be improved. In addition, a compensation capacitor can be formed in a narrow space.

The third mechanism includes a sensor body in which a fluid chamber is formed, and the fluid chamber can store a dielectric fluid that is in contact with the fixed electrode, the movable electrode, the compensation electrode, and the protruding portion, and the electrostatic The shield is formed with a communication hole, and a space between the compensation electrode and the protruding portion communicates with a space outside the electrostatic shield in the fluid chamber on both sides of the compensation electrode in the longitudinal direction.

According to the above configuration, a fluid chamber that stores the dielectric fluid is formed inside the sensor body, and the dielectric fluid comes into contact with the fixed electrode, the movable electrode, the compensation electrode, and the protruding portion of the electrostatic shield. Therefore, the capacitance of the capacitor formed by the fixed electrode and the movable electrode and the compensation capacitor formed by the compensation electrode and the protruding portion can be increased.

Here, the space between the electrode and the protrusion is compensated by the communication hole formed in the electrostatic shield, and the electrode is compensated in the longitudinal direction of the rod member. On both sides, it will communicate with the space outside the electrostatic shield in the fluid chamber. Therefore, the flow of the dielectric fluid in the space between the compensation electrode and the protrusion which are close to each other can be promoted, and the state of the dielectric fluid in the space between the compensation electrode and the protrusion can be made close to the dielectric in other parts of the fluid chamber. The state of the fluid. Therefore, changes in the dielectric constant caused by changes in the state of the dielectric fluid, such as temperature changes or changes in liquid quality, can be sharply reflected in the change in the electrostatic capacity of the compensation capacitor, and the measurement error of the compensation displacement can be improved. Precision.

In the fourth mechanism, the end portion of the rod-shaped member opposite to the predetermined range in the longitudinal direction is sealed in an annular shape along the outer circumference of the outer surface portion.

When the dielectric fluid contacts the fixed electrode and the compensation electrode, it is necessary to seal so that the dielectric fluid does not leak to the outside, and the fixed electrode and the compensation electrode can be pulled out toward the outside of the electrostatic shield.

In this regard, according to the above configuration, the end portion of the rod-shaped member opposite to the predetermined range in the longitudinal direction of the rod-shaped member is annularly sealed by the insulating material along the outer circumference of the outer surface portion. Further, as described above, the fixed electrode terminal and the compensation electrode terminal which are respectively connected to the fixed electrode and the compensation electrode are formed in a film shape on the outer surface portion of the rod-shaped member. Therefore, the thickness of the fixed electrode terminal and the compensation electrode terminal can be almost ignored, and the outer surface portion of the rod-shaped member can be easily sealed along the outer circumference.

In the fifth mechanism, the electrostatic shield extends in the longitudinal direction and is exposed to an opening of the sensor body, and an end portion of the rod-shaped member opposite to the predetermined range in the longitudinal direction, And before Between the electrostatic shields, they are sealed by the aforementioned insulating material.

According to the above configuration, since the electrostatic shield extends in the longitudinal direction of the rod-shaped member and is exposed to the opening of the sensor body, the protruding portion of the electrostatic shield forming the electrode of one of the compensation capacitors can be easily externally Circuit connection. Further, the end portion of the rod-shaped member opposite to the predetermined range in the longitudinal direction of the rod-shaped member and the electrostatic shield are sealed by an insulating material. Therefore, insulation between the fixed electrode terminal and the compensation electrode terminal and the electrostatic shield can be ensured, and the dielectric fluid can be sealed without leaking to the outside.

In the sixth mechanism, the entire rod-shaped member is formed of an insulating material.

According to the above configuration, since the entire rod-shaped member is formed of an insulating material, the outer surface portion of the rod-shaped member can be easily made an insulating material, and the rod-shaped member can be easily manufactured.

In the seventh mechanism, the entire cylindrical member is formed of a conductive material.

According to the above configuration, since the entire tubular member is formed of a conductive material, the tubular member itself can function as a movable electrode, and the movable electrodes can be easily connected in one piece. As a result, the manufacture of the movable electrode can be facilitated.

In the eighth mechanism, the fixed electrode terminal and the compensation electrode terminal are disposed to extend in the longitudinal direction and are close to each other, and the fixed electrode and the compensation electrode extend in the circumferential direction of the outer surface portion.

According to the above configuration, the fixed electrode terminal and the compensation electrode terminal are arranged to extend in the longitudinal direction of the rod-shaped member and to be close to each other. Therefore, the electrode terminals can be concentrated, and the electrode terminals can be easily connected to an external circuit.

Further, the fixed electrode and the compensation electrode extend in the circumferential direction of the outer surface portion of the rod-shaped member. Therefore, the electrode terminals can be concentrated, and the electrodes can be disposed efficiently, and the area of the electrodes can be ensured. Therefore, the accuracy of measuring the displacement of the measuring object can be improved.

In the ninth mechanism, the end portion on the predetermined range side of the rod-shaped member in the longitudinal direction is provided with an exposed portion in which the outer surface portion is exposed.

When the tubular member moves toward the longitudinal direction of the rod-shaped member as the measurement object is displaced, when the cylindrical member is inclined with respect to the rod-shaped member, the fixed electrode facing each other comes into contact with the movable electrode. At this time, particularly at the end portion of the rod-shaped member and the end portion of the cylindrical member, the fixed electrode and the movable electrode are likely to be in contact with each other first.

In this regard, according to the above configuration, the exposed portion of the outer surface portion formed of the insulating material is provided at the end portion on the predetermined range side of the rod-shaped member in the longitudinal direction of the rod-shaped member. Therefore, even if the end portion of the rod-shaped member comes into contact with the cylindrical member, the contact between the fixed electrode and the movable electrode can be suppressed.

Further, since the fixed electrode is formed in a film shape on the outer surface portion of the rod-shaped member, the pattern is such that the fixed electrode is not formed at the end portion of the rod-shaped member, or after the pattern of the fixed electrode is formed to the end portion of the rod-shaped member The pattern of the end portion is then removed, whereby the exposed portion can be easily formed.

In the tenth mechanism, the compensation electrode is a first compensation electrode, The compensation electrode terminal is a first compensation electrode terminal, and the capacitance displacement sensor includes a second compensation electrode formed in a film shape on the outer surface portion of the rod-shaped member and is larger than the first compensation The electrode is large and does not face the movable electrode; the second compensation electrode terminal is formed in a film shape on the outer surface portion of the rod-shaped member, and is connected to the second compensation electrode to the outside of the electrostatic shield. The state in which the electrostatic shield is insulated is extended in the longitudinal direction; the measuring circuit measures the capacitance between the two electrodes; and the switching circuit switches to a state in which the first compensation electrode terminal and the electrostatic shield are connected to the measuring circuit. a first state, a second state in which the second compensation electrode terminal and the electrostatic shield are connected to the measurement circuit, and a third state in which the fixed electrode terminal connected to each of the fixed electrodes is connected to the measurement circuit; The calculation unit measures the first static state by the measurement circuit in the first state, the second state, and the third state The measurement, the second electrostatic capacitance, and the third electrostatic capacitance are calculated based on the difference between the first electrostatic capacitance and the second electrostatic capacitance, and the difference between the first electrostatic capacitance and the third electrostatic capacitance. Displacement.

According to the above configuration, the second compensation electrode is formed larger than the first compensation electrode on the outer surface portion of the rod-shaped member. Further, the second compensation electrode is pulled out to the outside of the electrostatic shield by the second compensation electrode terminal.

By switching the circuit, switching between the first state in which the first compensation electrode terminal and the electrostatic shield are connected to the measurement circuit, the second state in which the second compensation electrode terminal and the electrostatic shield are connected to the measurement circuit, and the connection to each of the fixed electrodes The third electrode of the fixed electrode terminal is connected to the measurement circuit. then, The first electrostatic capacitance, the second electrostatic capacitance, and the third electrostatic capacitance are measured by the measurement circuit in the first state, the second state, and the third state by the measurement circuit.

Here, since the second compensation electrode is formed larger than the first compensation electrode, the opposing area between the second compensation electrode and the electrostatic shield is larger than the opposing area between the first compensation electrode and the electrostatic shield. In other words, the first compensation capacitor formed by the first compensation electrode and the electrostatic shield corresponds to a state in which the opposing area between the pair of fixed electrodes and the movable electrode is small (a state in which the displacement of the measurement target is small). In addition, the second compensation capacitor formed by the second compensation electrode and the electrostatic shield corresponds to a state in which the opposing area between the pair of fixed electrodes and the movable electrode is large (a state in which the displacement of the measurement target is large). Therefore, the displacement of the measurement target when the composite capacitor formed by the pair of fixed electrodes and the movable electrode corresponds to the first compensation capacitor and the case where the combined capacitor corresponds to the second compensation capacitor are obtained by experiments or the like in advance. The displacement of the measurement target can be used to calculate the displacement of the measurement target based on the difference between the first electrostatic capacitance and the second electrostatic capacitance and the difference between the first electrostatic capacitance and the third electrostatic capacitance.

Further, even if the dielectric constant between the pair of fixed electrodes and the movable electrode changes, the dielectric constants of the first compensation capacitor and the second compensation capacitor also change. Therefore, the displacement of the measurement target when the combined capacitor corresponds to the first compensation capacitor and the displacement of the measurement target when the combined capacitor corresponds to the second compensation capacitor do not change. Moreover, even if the electrostatic capacitance of the adjustment capacitor or the like used for measuring the electrostatic capacitance changes, the electrostatic capacitance of the first compensation capacitor and the second compensation capacitor is changed. The change in the electrostatic capacitance of the first compensation capacitor and the second compensation capacitor also has a similar tendency. Therefore, the displacement of the measurement target is calculated based on the difference between the first electrostatic capacitance and the second electrostatic capacitance and the difference between the first electrostatic capacitance and the third electrostatic capacitance, thereby eliminating the electrostatic capacitance of the adjustment capacitor or the like. The impact of changes. Therefore, even if the dielectric constant between the pair of fixed electrodes and the movable electrode changes, or the capacitance of the first compensation capacitor and the second compensation capacitor changes due to a change in electrostatic capacitance of the adjustment capacitor or the like, the capacitance can be accurately calculated. The displacement of the measurement object.

In the eleventh mechanism, each of the first compensation electrode and the second compensation electrode has a plurality of branching portions extending in a circumferential direction of the outer surface portion, and the branching portion of the first compensation electrode and the second compensation electrode The aforementioned branching portions are alternately arranged in the longitudinal direction.

When a temperature difference occurs between the first compensation electrode and the second compensation electrode, the capacitor formed by the first compensation electrode and the capacitor formed by the second compensation electrode may have a difference in dielectric constant. As a result, when the displacement of the measurement target is calculated based on the difference between the first electrostatic capacitance and the second electrostatic capacitance and the difference between the first electrostatic capacitance and the third electrostatic capacitance, the calculation accuracy of the displacement is deteriorated. Hey.

In this regard, according to the above configuration, each of the first compensation electrode and the second compensation electrode has a plurality of branching portions extending in the circumferential direction of the outer surface portion of the rod-shaped member. Further, since the branching portion of the first compensation electrode and the branching portion of the second compensation electrode are alternately arranged in the longitudinal direction of the rod-shaped member, it is possible to suppress a temperature difference between the first compensation electrode and the second compensation electrode. Therefore, it is possible to suppress the accuracy of calculating the displacement of the measurement target from deteriorating.

10‧‧‧ valve device

11‧‧‧1st ontology

11a‧‧‧Inlet

11b‧‧‧Export

12‧‧‧2nd ontology

12a‧‧‧ openings

13‧‧‧ Fluid Room

14‧‧‧Retaining components

20‧‧‧ spool valve

21‧‧‧Sleeve

21a, 21b‧‧‧Connected holes

22‧‧‧ spool (measurement object)

22a‧‧‧ditch

22b‧‧‧through hole

22c‧‧‧End

30‧‧‧Electrostatic displacement sensor

31‧‧‧ Columnar members (rod members)

31a‧‧‧End

31b‧‧‧Exposed Department

33‧‧‧Cylinder member (movable electrode)

33a‧‧‧ bottom

33b‧‧‧through hole

33c‧‧‧Connected holes

35‧‧‧Connecting components

37‧‧‧Electrostatic shielding

37a‧‧‧End

37b‧‧‧Protruding

37e‧‧‧ recess

37c, 37d‧‧‧Connected holes

40A, 40B‧‧‧ fixed electrode

41‧‧‧Compensation electrode (1st compensation electrode)

42‧‧‧Compensation electrode (2nd compensation electrode)

43‧‧‧Connecting electrode

51‧‧‧Low-melting glass (insulation material)

52‧‧‧Low-melting glass (insulation material)

61‧‧‧Capacity measurement circuit (measurement circuit)

62‧‧‧Switch circuit (switching circuit)

64‧‧‧Microcomputer (MC) (calculation department)

112‧‧‧2nd ontology

112a‧‧‧ openings

133‧‧‧Cylinder members

133a‧‧‧electrode (movable electrode)

137‧‧‧Electrostatic shielding

137a‧‧‧End

141‧‧‧Compensation electrode (1st compensation electrode)

141a‧‧ 岐 Division

142‧‧‧Compensation electrode (2nd compensation electrode)

142a‧‧‧ Division

237‧‧‧Electrostatic shielding

SW1, SW2, SW3‧‧‧ switch

C1‧‧‧Compensation capacitor (1st compensation capacitor)

C2‧‧‧Compensation capacitor (2nd compensation capacitor)

Ca‧‧‧ capacitor

Cab‧‧‧Synthetic capacitor

Cas‧‧ capacitor

Cb‧‧‧ capacitor

Cc‧‧‧ capacitor

Cms‧‧‧ capacitor

Ct‧‧‧Adjusting capacitor

Cin+‧‧‧ input terminal

Cin-‧‧‧ input terminal

T1‧‧‧Compensation electrode terminal (1st compensation electrode terminal)

T2‧‧‧Compensation electrode terminal (2nd compensation electrode terminal)

T3‧‧‧Connecting electrode terminal

Ta, Tb‧‧‧ fixed electrode terminal

Ts‧‧‧Electrostatic shield terminal

C, Cn, C1(ε), C2(ε), Cab(ε), C1(ε a), C2(ε a), Cab(ε a), C1(ε b), C2(ε b), Cab (ε b), C1m (ε a), C2m (ε a) ‧‧‧ electrostatic capacity

ε, ε a, ε b‧‧‧ dielectric constant

x, x1, x2‧‧‧ displacement

S‧‧‧electrode area

d‧‧‧Interelectrode distance

1 is a partial cross-sectional view showing a portion of an electrostatic capacitance type displacement sensor and a spool valve.

Figure 2 is a side elevational view of the displacement sensor of Figure 1.

Fig. 3 is a front view showing a columnar member and an electrode.

Fig. 4 is a developed view showing the electrode of Fig. 3 in an expanded manner.

Fig. 5 is a schematic view schematically showing a capacitor formed in each portion of the displacement sensor of Fig. 1.

Figure 6 is a circuit diagram showing the equivalent circuit of Figure 5.

Figure 7 is a block diagram showing the electrical configuration of the displacement sensor of Figure 1.

Fig. 8 is a view showing the relationship between the displacement of the bobbin and the electrostatic capacity.

Fig. 9 is a partial cross-sectional view showing a modified example of the tubular member and the movable electrode.

Fig. 10 is a partial cross-sectional view showing a modified example of the electrostatic shield.

Fig. 11 is a partial cross-sectional view showing another modification of the electrostatic shield.

Fig. 12 is a front elevational view showing a modified example of the compensation electrode.

Fig. 13 is a partial cross-sectional view showing a modified example of the tubular member.

Fig. 14 is a front elevational view showing a modified example of the fixed electrode.

Fig. 15 is a developed view showing the electrode of Fig. 14 in an expanded manner.

Fig. 16 is a front elevational view showing a modified example of the fixed electrode.

Fig. 17 is a developed view showing the electrode of Fig. 16 developed.

Fig. 18 is a partial cross-sectional view showing the configuration of a displacement sensor using the fixed electrode shown in Fig. 16.

Form for implementing the invention

Hereinafter, an embodiment will be described with reference to the drawings. This embodiment is a valve device that controls the flow of a fluid such as a chemical liquid in a semiconductor manufacturing apparatus or the like.

1 is a partial cross-sectional view showing a portion of the electrostatic capacitance type displacement sensor 30 and the bobbin valve 20. As shown in the figure, the valve device 10 includes a first body 11, a second body 12, a spool valve 20, a capacitance type displacement sensor 30, and the like. The first body 11 and the second body 12 are formed into a rectangular tubular shape (cylindrical shape) having a cylindrical space inside by a metal such as stainless steel. The second body 12 is attached to the end portion of the first body 11 so that the central axes thereof coincide with each other, and the first body 11 and the second body 12 are sealed by a sealing member. The wired shaft valve 20 and the displacement sensor 30 are housed inside the first body 11 and the second body 12. The spool valve 20 and the displacement sensor 30 are arranged side by side in the direction of the central axis (long direction) of the first body 11. In the first body 11, a fluid inflow port 11a and an outflow port 11b are formed.

The bobbin valve 20 is provided with a sleeve 21, a bobbin 22, an actuator (not shown), and the like. The sleeve 21 and the bobbin 22 are formed of a metal such as stainless steel. The sleeve 21 is formed into a cylindrical shape (cylindrical shape), and the bobbin 22 is formed into a cylindrical shape (columnar shape). The sleeve 21 and the bobbin 22 are formed in a corresponding sectional shape, and the bobbin 22 is slidably inserted into the inside of the sleeve 21. A through hole 22b extending in the center axis direction (long direction) is formed inside the bobbin 22.

In the sleeve 21, communication holes 21a and 21b are formed at positions corresponding to the inflow port 11a and the outlet port 11b of the first body 11 described above. The communication holes 21a, 21b extend in the circumferential direction of the sleeve 21 to make the inside of the sleeve 21 Connected to the outside. The bobbin 22 is formed with an annular groove 22a extending in the circumferential direction at a width corresponding to the interval between the communication holes 21a and 21b of the sleeve 21. The bobbin 22 (measurement target) is coupled to an actuator such as an electromagnetic actuator, and is moved back and forth in the central axis direction (long direction) by the actuator. Thereby, it is possible to control the state in which the communication hole 21a of the sleeve 21 communicates with the communication hole 21b by the outer circumferential surface of the bobbin 22, and the communication hole 21a and the communication hole 21b by the groove 22a of the bobbin 22. Connected state.

The displacement sensor 30 is housed inside the first body 11 and the second body 12. The displacement sensor 30 includes a columnar member 31, a tubular member 33, a coupling member 35, an electrostatic shield 37, and the like.

The tubular member 33 (movable electrode) is formed in a cylindrical shape (connected into a single shape) having a bottom portion 33a by a metal (conductive material) such as stainless steel. The connecting member 35 is formed in a cylindrical shape by an insulating material such as ceramic or resin. The bottom portion 33a of the tubular member 33 is coupled to the end portion 22c of the bobbin 22 via the connecting member 35. That is, the bobbin 22 and the tubular member 33 are electrically insulated by the connecting member 35.

A through hole 33b that extends in the central axis direction (long direction) of the tubular member 33 is formed in the bottom portion 33a of the tubular member 33. The through hole 22b of the bobbin 22 and the through hole 33b of the bottom portion 33a communicate with each other through the cylindrical connecting member 35. That is, the inside of the bobbin 22 is in communication with the inside of the cylindrical member 33.

The columnar member 31 (rod-shaped member) is formed in a cylindrical shape by an insulating material such as alumina. That is, the outer surface portion of the columnar member 31 is formed of an insulating material. On the outer surface portion of the columnar member 31, a pair of fixed electricity The poles 40A and 40B, the compensation electrode 41 (first compensation electrode), and the compensation electrode 42 (second compensation electrode) are formed in a film shape. A predetermined range from the one end in the central axis direction (long direction) of the columnar member 31, in detail, a portion corresponding to the fixed electrodes 40A and 40B, is inserted into the inside of the cylindrical member 33. The columnar member 31 and the cylindrical member 33 are aligned with each other in the center axis. A predetermined clearance (gap) is formed between the fixed electrodes 40A and 40B (the columnar member 31) and the tubular member 33. That is, the fixed electrodes 40A and 40B and the tubular member 33 are opposed to each other in a state of being electrically insulated.

On the outer circumference of the columnar member 31 and the cylindrical member 33, an electrostatic shield 37 covering the fixed electrodes 40A and 40B, the compensation electrodes 41 and 42 and the tubular member 33 is provided. The electrostatic shield 37 is formed in a cylindrical shape (cylindrical shape) by a metal (conductive material) such as stainless steel. The electrostatic shield 37 is electrically insulated from the fixed electrodes 40A and 40B, the compensation electrodes 41 and 42 and the tubular member 33.

Between the outer peripheral surface of the end portion 37a of the electrostatic shield 37 and the inner peripheral surface of the second body 12, the low-melting glass 51 (insulating material) is hermetically sealed (sealed) in the circumferential direction (refer to the figure). 2). Thereby, the electrostatic shield 37 is attached to the second body 12 in a state of being electrically insulated from the second body 12. The end portion 31a of the columnar member 31 is exposed to the outside of the electrostatic shield 37, that is, the opening portion 12a of the second body 12. The inner peripheral surface of the end portion 37a of the electrostatic shield 37 and the outer peripheral surface of the end portion 31a of the columnar member 31 are annularly sealed in the circumferential direction by the low-melting glass 52 (insulating material) (refer to the figure). 2). Thereby, the columnar member 31 is mounted on the electrostatic shield 37.

The central axis of the electrostatic shield 37 coincides with the central axis of the columnar member 31. The electrostatic shield 37 extends toward the central axis direction (long direction), and its end portion The 37a is exposed to the opening 12a of the second body 12. A wiring (not shown) is connected to the end portion 37a of the electrostatic shield 37, and the electrostatic shield 37 is grounded by the wiring.

Inside the first body 11 and the second body 12, a fluid chamber 13 for storing a fluid is formed. The fluid chamber 13 is defined by the first body 11, the second body 12, the sleeve 21, the bobbin 22, the electrostatic shield 37, and the columnar member 31. The fluid that is controlled to flow by the spool valve 20 flows into the fluid chamber 13 from a clearance (gap) between the inner circumferential surface of the sleeve 21 and the outer circumferential surface of the bobbin 22. Then, the inside of the fluid chamber 13 is filled with fluid. Therefore, the electrodes 40A, 40B, 41, 42, the cylindrical member 33, and the electrostatic shield 37 are in contact with the fluid. The fluid composed of the chemical liquid is a dielectric body and functions as a dielectric fluid. Further, the first body 11 and the second body 12 constitute a sensor body of the displacement sensor 30.

In a portion of the electrostatic shield 37 that faces the compensation electrodes 41 and 42, a protruding portion 37b that protrudes toward the compensation electrodes 41 and 42 is formed. The protruding portion 37b protrudes in an annular shape to a position close to the compensation electrodes 41, 42. The compensation electrodes 41, 42 do not face the cylindrical member 33.

In the electrostatic shield 37, communication holes 37c and 37d that communicate the inside and the outside of the electrostatic shield 37 in the fluid chamber 13 are formed. The communication holes 37c and 37d are formed on both sides of the compensation electrodes 41 and 42 in the central axis direction (long direction) of the columnar member 31. Specifically, the communication holes 37c and 37d are formed at both ends of the range including the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 in the central axis direction of the columnar member 31.

Next, a pair of fixed electrodes 40A, 40B, and The configuration of the compensation electrodes 41, 42. 3 is a front view showing the columnar member 31, the fixed electrodes 40A and 40B, and the compensation electrodes 41 and 42. FIG. 4 is a developed view showing the electrodes 40A, 40B, 41, and 42 of FIG.

As shown in the figure, the pair of fixed electrodes 40A, 40B are formed in a predetermined range from one end in the central axis direction (long direction) of the columnar member 31. The fixed electrodes 40A and 40B extend in the circumferential direction of the outer surface portion of the columnar member 31. Further, the fixed electrodes 40A and 40B are formed in a semi-cylindrical shape on the outer surface portion of the columnar member 31. Therefore, the pair of fixed electrodes 40A, 40B are opposed to each other with the columnar member 31 interposed therebetween. In the columnar member 31, an exposed portion 31b in which the outer surface portion is exposed is formed at an end portion on the side where the fixed electrodes 40A and 40B are formed in the longitudinal direction. That is, the fixed electrodes 40A and 40B are not formed in the exposed portion 31b.

Fixed electrode terminals Ta and Tb are connected to portions adjacent to the fixed electrode 40A and the fixed electrode 40B. The fixed electrode terminals Ta and Tb extend in the longitudinal direction of the columnar member 31 to the end portion 31a. Further, the fixed electrode terminals Ta and Tb extend to the end faces of the end portions 31a (refer to FIG. 2). Therefore, the fixed electrode terminals Ta and Tb are exposed to the outside of the electrostatic shield 37, that is, the opening 12a of the second body 12 (see FIG. 1). The fixed electrode terminals Ta and Tb are arranged in parallel to each other and in parallel (parallel).

The compensation electrode 42 is formed in the range of the center axis direction (long direction) of the columnar member 31 and the range in which the fixed electrodes 40A and 40B are formed. The compensation electrode 42 extends in the circumferential direction of the outer surface portion of the columnar member 31. Further, the compensation electrode 42 is formed in a cylindrical shape on the outer surface portion of the columnar member 31.

a portion of the compensation electrode 42 that is close to the fixed electrode terminal Ta The compensation electrode terminal T2 is connected to the minute. The compensation electrode terminal T2 (second compensation electrode terminal) extends in the longitudinal direction of the columnar member 31 to the end portion 31a. Further, the compensation electrode terminal T2 extends to the end surface of the end portion 31a (refer to FIG. 2). Therefore, the compensation electrode terminal T2 is exposed to the outside of the electrostatic shield 37, that is, the opening 12a of the second body 12 (see FIG. 1). The compensation electrode terminal T2 is disposed in parallel (parallel) to the fixed electrode terminal Ta.

The compensation electrode 41 is formed in a range in the central axis direction (long direction) of the columnar member 31, and is adjacent to the range in which the compensation electrode 42 is formed. The compensation electrode 41 extends in the circumferential direction of the outer surface portion of the columnar member 31. The compensation electrode 41 is formed in a cylindrical shape on the outer surface portion of the columnar member 31. Here, in the longitudinal direction of the columnar member 31, the length of the compensation electrode 42 is set longer than the length of the compensation electrode 41. That is, the area of the compensation electrode 42 is set to be larger than the area of the compensation electrode 41.

A compensation electrode terminal T1 is connected to a portion of the compensation electrode 41 that is close to the fixed electrode terminal Tb. The compensation electrode terminal T1 (first compensation electrode terminal) extends in the longitudinal direction of the columnar member 31 to the end portion 31a. Further, the compensation electrode terminal T1 extends to the end surface of the end portion 31a (refer to FIG. 2). Therefore, the compensation electrode terminal T1 is exposed to the outside of the electrostatic shield 37, that is, the opening 12a of the second body 12 (see FIG. 1). Further, the compensation electrode terminal T1 is disposed in parallel (parallel) to the fixed electrode terminal Tb.

The electrodes 40A, 40B, 41, and 42 and the terminals Ta, Tb, T1, and T2 are formed into a film shape by screen printing and baking a paste containing a conductive material such as silver. That is, the electrodes 40A, 40B, 41, 42 and the terminals Ta, Tb, T1, T2 are made of a mesh cover formed with an electrode pattern, and the conductive material is used. Printed by this.

The terminals Ta, Tb, T1, and T2 are collectively arranged at one position in the circumferential direction of the outer surface portion of the columnar member 31. In the electrostatic shield 37, a concave portion 37e (see FIG. 2) is formed in a portion facing the terminals Ta, Tb, T1, and T2. The recess 37e extends in the direction of the central axis (long direction) of the columnar member 31 along the terminals Ta, Tb, T1, and T2. The depth of the concave portion 37e is set to be deeper than the thickness of the film-shaped terminals Ta, Tb, T1, and T2. Thereby, the distance between the terminals Ta, Tb, T1, T2 and the electrostatic shield 37 can be ensured, and the terminals Ta, Tb, T1, T2 can be insulated from the electrostatic shield 37. The low-melting glass 52 is also introduced into the inside of the recess 37e, and the columnar member 31 and the electrostatic shield 37 are sealed. That is, sealing is performed so that fluid does not leak from the fluid chamber 13, and the electrodes 40A, 40B, 41, 42 can be pulled out toward the outside of the electrostatic shield 37.

Next, a capacitor in which the capacitance is measured and a capacitor formed in another portion in the capacitance displacement sensor 30 will be described. FIG. 5 is a schematic view schematically showing a capacitor formed in each portion of the displacement sensor 30 of FIG. 1. Figure 6 is a circuit diagram showing the equivalent circuit of Figure 5.

As shown in the figure, the capacitor Ca is formed by the fixed electrode 40A and the cylindrical member 33, and the capacitor Cb is formed by fixing the electrode 40B and the cylindrical member 33. Since the tubular members 33 are connected in a single shape, the capacitor Ca and the capacitor Cb are connected in series by the tubular member 33. Further, the composite capacitor Cab is formed by the capacitors Ca and Cb.

Here, in the bobbin valve 20, when the bobbin 22 is moved by the driving of the actuator, the tubular member 33 coupled to the bobbin valve 20 is moved in the central axis direction (long direction). Thereby, the fixed electrodes 40A, 40B and the barrel The area of the opposing portion of the member 33 changes, and the electrostatic capacitance C of the composite capacitor Cab changes. That is, the relationship of C = ε × S / d will hold. C is the electrostatic capacity of the capacitor, ε is the dielectric constant, S is the electrode area, and d is the distance between the electrodes. Further, the inter-electrode distance d is a known constant value, and the electrode area S changes in accordance with the displacement of the bobbin 22. Therefore, by measuring the electrostatic capacitance between the fixed electrode terminal Ta and the fixed electrode terminal Tb, the displacement of the bobbin 22 can be measured in accordance with the change in electrostatic capacitance.

When the tubular member 33 moves toward the central axis direction (long direction) of the columnar member 31 as the bobbin 22 is displaced, when the cylindrical member 33 is inclined with respect to the columnar member 31, the fixed electrodes facing each other are opposed to each other. 40A, 40B will come into contact with the tubular member 33. At this time, particularly in the end portion of the columnar member 31 and the end portion of the cylindrical member 33, the fixed electrodes 40A and 40B and the tubular member 33 are easily brought into contact with each other first.

In this regard, the exposed portion 31b where the fixed electrodes 40A and 40B are not formed is provided at the end portion of the columnar member 31 in the longitudinal direction of the columnar member 31. Therefore, even if the exposed portion 31b comes into contact with the tubular member 33, the fixed electrodes 40A and 40B can be prevented from coming into contact with the tubular member 33.

Further, the compensation electrode C1 (first compensation capacitor) is formed by the compensation electrode 41 and the protruding portion 37b of the electrostatic shield 37, and the compensation electrode C2 (second compensation capacitor) is formed by compensating the electrode 42 and the protruding portion 37b. As described above, between the fixed electrodes 40A and 40B and the tubular member 33, and between the compensation electrodes 41 and 42 and the protruding portion 37b of the electrostatic shield 37, the fluid composed of the dielectric body is filled.

Here, when the state of the fluid (temperature or liquid quality) changes, the fluid The dielectric constant ε changes, and the electrostatic capacity of the composite capacitor Cab also changes. At this time, the electrostatic capacitance of the compensation capacitors C1 and C2 also changes due to the change in the dielectric constant ε of the fluid. The inter-electrode distance d and the electrode area S of the compensation capacitors C1 and C2 can be obtained in advance by design values or actual measurements. Therefore, by measuring the electrostatic capacitance C between the compensation electrode terminal T1 (T2) and the electrostatic shield terminal Ts, the dielectric constant ε of the fluid can be calculated from the relationship of C = ε × S / d. Then, the electrostatic capacity of the composite capacitor Cab is measured using the calculated dielectric constant ε, whereby the displacement measurement error of the bobbin 22 due to the change in the dielectric constant of the fluid can be compensated.

Further, in the electrostatic shield 37, communication holes 37c and 37d are formed. Therefore, the space between the compensation electrodes 41, 42 and the protruding portion 37b of the electrostatic shield 37 compensates both sides of the electrodes 41, 42 in the longitudinal direction of the columnar member 31, and communicates with the outside of the electrostatic shield 37. Specifically, the communication holes 37c and 37d are formed at both ends of the range including the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 in the longitudinal direction of the columnar member 31. Therefore, even if the compensation electrodes 41 and 42 are close to the protruding portion 37b, the fluid can flow between the compensation electrodes 41 and 42 and the protruding portion 37b. As a result, the state of the fluid between the compensating electrodes 41, 42 and the protruding portion 37b can be brought close to the state of the fluid of the other portions of the fluid chamber 13, and the accuracy of compensating for the displacement measurement error of the bobbin 22 can be improved.

The electrodes 40A, 40B, 41, 42 are covered by an electrostatic shield 37, and the electrostatic shield 37 is grounded. Therefore, even if the charge state or the electrostatic capacitance Cn of the bodies 11 and 12 is changed by the user contacting the bodies 11, 12 and the like, the influence on the electrodes 40A, 40B, 41, 42 can be suppressed.

Further, the capacitor Cas is formed by the fixed electrode 40A and the electrostatic shield 37. Otherwise, the capacitor Cc is formed by a portion where the fixed electrode 40A is close to the fixed electrode 40B, and the capacitor Cms is formed by the cylindrical member 33 and the electrostatic shield 37. The electrostatic capacitances of the capacitors Cas, Cc, and Cms are smaller than those of the capacitors Ca, Cb, Cab, C1, and C2.

Next, an electrical configuration of the displacement sensor 30 of Fig. 1 will be described with reference to Fig. 7 . The displacement sensor 30 includes a capacity measuring circuit 61 and a switching circuit 62.

The capacity measuring circuit 61 is a conventional circuit that measures the electrostatic capacitance between two points connected to the input terminals Cin+ and Cin-.

The switch circuit 62 (switching circuit) includes a microcomputer 64 (hereinafter referred to as "MC64") and switches SW1, SW2, and SW3. The switches SW1, SW2, and SW3 are analog switches of CMOS or the like, and can be switched to ON and OFF at a high speed by the MC64. Further, the capacity measuring circuit 61 is provided with an adjustment capacitor Ct for adjusting the capacitance measurement. The electrostatic capacity of the adjustment capacitor Ct is independent of the dielectric constant of the fluid, but varies depending on other changes in the ambient temperature.

Then, by switching the switch SW1 to ON and switching the switches SW2 and SW3 to OFF, the compensation electrode terminal T1 and the electrostatic shield terminal Ts are connected to the first state of the capacity measuring circuit 61. By switching the switch SW2 to ON and switching the switches SW1 and SW3 to OFF, the compensation electrode terminal T2 and the electrostatic shield terminal Ts are connected to the second state of the capacity measuring circuit 61. By switching the switch SW3 to ON and switching the switches SW1 and SW2 to OFF, the fixed electrode terminals Ta and Tb are connected to the third state of the capacity measuring circuit 61.

In the first state, the capacitance measuring circuit 61 measures the first capacitance which is the capacitance C1 (ε) of the compensation capacitor C1. In the second state, the capacitance measuring circuit 61 measures the second capacitance as the capacitance C2 (?) of the compensation capacitor C2. In the third state, the capacity measuring circuit 61 measures the third capacitance as the capacitance Cap (ab) of the combined capacitor Cab. The measured electrostatic capacitances C1 (ε), C2 (ε), and Cab (ε) are transmitted from the capacity measuring circuit 61 to the MC 64 of the switch circuit 62.

The relationship between the displacement of the bobbin 22 and the electrostatic capacitance Cab(?) of the combined capacitor Cab is shown in FIG. As shown in the figure, the electrostatic capacity Cab(?) is proportional to the displacement of the bobbin 22. In other words, the electrostatic capacitance Cab (ε) is proportional to the area of the portion facing the fixed electrode 40A, 40B and the cylindrical member 33. In addition, FIG. 1 shows a state in which the displacement of the bobbin 22 is the largest, that is, a state in which the area of the opposing portion between the fixed electrodes 40A, 40B and the cylindrical member 33 is the largest.

Here, when the dielectric constant of the fluid is ε a , as shown by the solid line, when the displacement of the bobbin 22 is x1, the electrostatic capacity Cab (ε a) of the composite capacitor Cab is equal to the electrostatic capacity of the compensating capacitor C1. C1 (ε a). Further, when the linear axis 22 is displaced by x2, the electrostatic capacitance Cab (ε a) of the composite capacitor Cab is equal to the electrostatic capacitance C2 (ε a) of the compensation capacitor C2.

That is, the compensation capacitors C1 and C2 are set such that the compensation capacitor C1 corresponds to the displacement x1 of the composite capacitor Cab, and the compensation capacitor C2 corresponds to the displacement x2 of the composite capacitor Cab. These displacements x1 and x2 can be obtained by experiments or the like in advance. Then, the electrostatic capacitances C1 (ε a), C2 (ε a), and Cab (ε a) are measured, and the electrostatic capacity Cab (ε a) is substituted for the static electricity. A straight line x of the bobbin 22 can be measured by a straight line of the capacitance C1 (ε a) and the electrostatic capacitance C2 (ε a).

In the case where the dielectric constant of the fluid changes to ε b , as shown by the broken line, when the displacement of the bobbin 22 is x1, the electrostatic capacitance Cab( ε b ) of the composite capacitor Cab is equal to the electrostatic capacitance C1 of the compensation capacitor C1 (ε). b). Further, when the linear axis 22 is displaced by x2, the electrostatic capacitance Cab(?b) of the composite capacitor Cab is equal to the electrostatic capacitance C2(?b) of the compensation capacitor C2. At this time, in the combined capacitor Cab and the compensation capacitors C1 and C2, since the dielectric constant of the fluid changes in the same manner as ε b , the combined capacitor Cab corresponds to the displacement x1 of the bobbin 22 in the case of compensating the capacitor C1, and is synthesized. The displacement of the bobbin 22 in the case where the capacitor Cab corresponds to the compensation capacitor C2 does not change.

Further, as described above, the capacitance of the adjustment capacitor Ct of the capacity measuring circuit 61 is changed depending on the dielectric constant of the fluid, and the like due to changes in the environmental temperature. Therefore, when the dielectric constant of the fluid is ε a , for example, when the capacitance of the adjustment capacitor Ct increases, the capacitances C1 ( ε a ) and C 2 ( ε a ) of the compensation capacitors C1 and C2 are respectively Increased to electrostatic capacitance C1m (ε a), C2m (ε a). As a result, as shown by the one-dot chain line, the relationship between the displacement of the bobbin 22 and the electrostatic capacitance Cab (ε a) of the combined capacitor Cab is shifted from the relationship shown by the solid line. Therefore, the accuracy of the displacement of the measuring bobbin 22 is deteriorated because of the change in the electrostatic capacity of the adjusting capacitor Ct.

In this regard, in the present embodiment, the MC64 (calculation unit) differs from the capacitance C1 (ε) of the compensation capacitor C1 and the capacitance C2 (ε) of the compensation capacitor C2, and the capacitance C1 (ε) and Synthetic capacitor The displacement of the bobbin 22 is calculated by the difference between the electrostatic capacitances Cab (ε) of the Cab. That is, the difference between the electrostatic capacitance C1 (ε) and the electrostatic capacitance C2 (ε) is calculated in accordance with the change from the displacement x1 to the displacement x2, and the electrostatic capacitance C1 (ε) and the electrostatic capacitance Cab (ε) are calculated. The difference between the corresponding displacements x.

Here, even if the electrostatic capacitances of the compensation capacitors C1 and C2 change, the capacitances C1 (ε) and C2 (ε) of the compensation capacitors C1 and C2 change, and the capacitances C1 (ε) and C2 (ε) change. Will show the same tendency. For example, a straight line passing through the one-point chain line of the electrostatic capacitances C1m (ε a) and C2m (ε a) is a straight line in which the straight lines passing through the solid lines of the electrostatic capacitances C1 (ε a) and C2 (ε a) are moved in parallel. Therefore, the displacement x of the bobbin 22 is calculated based on the difference between the electrostatic capacitance C1 (ε) and the electrostatic capacitance C2 (ε) and the difference between the electrostatic capacitance C1 (ε) and the electrostatic capacitance Cab (ε). The influence on the electrostatic capacitances C1 (ε) and C2 (ε) due to the change in the electrostatic capacitance of the adjustment capacitor Ct can be eliminated.

The present embodiment described in detail above has the following advantages.

‧ In addition to the pair of fixed electrodes 40A and 40B, the compensation electrodes 41 and 42 that do not face the cylindrical member 33 are formed in a film shape on the outer surface portion of the columnar member 31. Therefore, the capacitances of the compensation capacitors C1 and C2 in which the compensation electrodes 41 and 42 are formed as one electrode are measured, whereby the dielectric constant ε variation between the fixed electrodes 40A and 40B and the cylindrical member 33 can be compensated for. The resulting measurement error of the displacement x.

The pair of fixed electrodes 40A and 40B that face each other with the columnar member 31 interposed therebetween are formed in a film shape on the outer surface portion of the columnar member 31 formed of an insulating material. Therefore, it is not necessary to configure each other to form a different structure. A pair of fixed electrodes of the member may be formed as a film-like pattern on the outer surface portion of the one columnar member 31 to form a pair of fixed electrodes 40A and 40B. Therefore, the interval between the pair of fixed electrodes 40A and 40B is defined by the size of the columnar member 31, and the pair of fixed electrodes 40A and 40B can be accurately arranged at predetermined intervals.

The fixed electrodes 40A and 40B, the tubular member 33, and the compensation electrodes 41 and 42 are covered by an electrostatic shield 37 insulated from the electrodes. Since the electrostatic shield 37 is grounded, even if the user touches the main body 11 or 12 of the sensor or the body of the spool valve 20, the electrostatic capacitance between the pair of fixed electrodes 40A and 40B can be prevented from becoming unstable.

The fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 are connected to the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42, respectively. The fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 extend to the outside of the electrostatic shield 37 in the longitudinal direction of the columnar member 31 in a state insulated from the electrostatic shield 37. The fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 are formed in a film shape on the outer surface portion of the columnar member 31, respectively. Therefore, as long as the fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 are formed in a film-like pattern together with the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42, the fixed electrodes 40A and 40B and the compensation electrode 41 can be 42 is pulled out toward the outside of the electrostatic shield 37, respectively. Therefore, it is easy to pull the electrodes 40A, 40B, 41, 42 toward the outside of the electrostatic shield 37.

‧ Since the protruding portion 37b of the electrostatic shield 37 is close to the compensation electrodes 41 and 42, the compensation capacitors C1 and C2 having a larger electrostatic capacitance can be formed by the compensation electrodes 41 and 42 and the protruding portion 37b. Therefore, The electrostatic shield 37 is utilized as an electrode for compensating one of the capacitors C1, C2, and the accuracy of the compensation capacitors C1, C2 can be improved. Further, the compensation capacitors C1, C2 can be formed in a narrow space.

‧ A fluid chamber 13 for storing a dielectric fluid is formed inside the bodies 11 and 12, and the dielectric fluid contacts the fixed electrodes 40A and 40B, the tubular member 33, the compensation electrodes 41 and 42 and the protruding portion 37b of the electrostatic shield 37. Therefore, the capacitance of the composite capacitor Cab formed by the fixed electrodes 40A, 40B and the cylindrical member 33, and the compensation capacitors C1, C2 formed by the compensation electrodes 41, 42 and the protruding portion 37b can be increased. Further, the fluid that is controlled to flow through the spool valve 20 can be utilized as a dielectric.

‧ By the communication holes 37c, 37d formed in the electrostatic shield 37, the space between the electrodes 41, 42 and the protruding portion 37b is compensated, and both sides of the electrodes 41, 42 are compensated in the longitudinal direction of the columnar member 31, and the fluid The space outside the electrostatic shield 37 in the chamber 13 communicates. Therefore, the flow of the dielectric fluid in the space between the compensation electrodes 41, 42 and the protruding portion 37b which are close to each other can be promoted, and the state of the dielectric fluid in the space between the compensation electrodes 41, 42 and the protruding portion 37b can be compensated ( Temperature or liquid quality), near the state of the dielectric fluid in other portions of the fluid chamber 13. Therefore, the change in the dielectric constant ε due to the change in the state of the dielectric fluid can be sharply reflected in the changes in the electrostatic capacitances C1 (ε) and C2 (ε) of the compensation capacitors C1 and C2, and the compensation displacement can be improved. The accuracy of the measurement error of x.

‧ The communication holes 37c and 37d are formed at both ends of the range including the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 in the longitudinal direction of the columnar member 31. Therefore, between the fixed electrodes 40A, 40B and the cylindrical member 33 can be made The state of the dielectric fluid is similar to the state of the dielectric fluid between the compensation electrodes 41, 42 and the projection 37b. Therefore, the measurement error of the displacement x of the bobbin 22 due to the change in the dielectric fluid state (dielectric constant) can be compensated with higher precision.

‧ The end portion 31a of the columnar member 31 is annularly sealed by an insulating material along the outer periphery of the outer surface portion. Further, as described above, the fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 connected to the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 are formed in a film shape on the outer surface portion of the columnar member 31. . Therefore, the thickness of the fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 can be almost ignored, and the outer surface portion of the columnar member 31 can be easily sealed along the outer circumference.

‧ Since the electrostatic shield 37 extends in the longitudinal direction of the columnar member 31 and is exposed to the opening 12a of the second body 12, the protruding portion 37b of the electrostatic shield 37 that compensates for one of the capacitors C1 and C2 can be formed. Easily connect to external circuits. Further, the end portion 31a of the columnar member 31 and the electrostatic shield 37 are sealed by an insulating material. Therefore, insulation between the fixed electrode terminals Ta, Tb and the compensation electrode terminals T1, T2 and the electrostatic shield 37 can be ensured, and sealing can be performed so that the dielectric fluid does not leak to the outside.

‧ In the electrostatic shield 37, a recess 37e is formed in a portion facing the terminals Ta, Tb, T1, and T2. The concave portion 37e extends in the longitudinal direction of the columnar member 31 along the terminals Ta, Tb, T1, and T2. Thereby, the distance between the terminals Ta, Tb, T1, T2 and the electrostatic shield 37 can be ensured, and the terminals Ta, Tb, T1, T2 can be more reliably insulated from the electrostatic shield 37.

‧Because the entire columnar member 31 is formed of an insulating material, The outer surface portion of the columnar member 31 can be easily made of an insulating material, and the manufacture of the columnar member 31 can be facilitated.

‧ Since the entire tubular member 33 is formed of a conductive material, the tubular member 33 itself can function as a movable electrode, and the movable electrodes can be easily connected in a single state. As a result, the manufacture of the movable electrode can be facilitated.

The fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 are arranged to extend in the longitudinal direction of the columnar member 31 and are close to each other. Therefore, the electrode terminals can be concentrated, and the electrode terminals can be easily connected to an external circuit.

The fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 extend in the circumferential direction of the outer surface portion of the columnar member 31. Therefore, the electrode terminals Ta, Tb, T1, and T2 can be concentrated, and the electrodes 40A, 40B, 41, and 42 can be efficiently disposed, and the areas of the electrodes 40A, 40B, 41, and 42 can be secured. Therefore, the accuracy of the displacement x of the measuring bobbin 22 can be improved.

In the longitudinal direction of the columnar member 31, the end portion on the side of the fixed electrode 40A, 40B of the columnar member 31 is provided with an exposed portion 31b which is exposed by the outer surface portion formed of an insulating material. Therefore, even if the end portion of the columnar member 31 comes into contact with the tubular member 33, the fixed electrodes 40A, 40B can be prevented from coming into contact with the tubular member 33.

‧ Since the fixed electrodes 40A and 40B are formed in a film shape on the outer surface portion of the columnar member 31, the pattern is not formed at the end of the columnar member 31 as the fixed electrodes 40A, 40B, or in the pattern of the fixed electrodes 40A, 40B After forming the end portion of the columnar member 31, the pattern of the end portion is removed, whereby The exposed portion 31b can be easily formed.

‧ Since the compensation electrode 42 is formed larger than the compensation electrode 41, the opposing area between the compensation electrode 42 and the electrostatic shield 37 is also larger than the opposing area between the compensation electrode 41 and the electrostatic shield 37. In other words, the compensation capacitor C1 formed by the compensation electrode 41 and the electrostatic shield 37 corresponds to a state in which the opposing area between the pair of fixed electrodes 40A and 40B and the tubular member 33 is small (displacement x1 of the bobbin 22). Further, the compensation capacitor C2 formed by the compensation electrode 42 and the electrostatic shield 37 corresponds to a state in which the opposing area between the pair of fixed electrodes 40A and 40B and the tubular member 33 is large (displacement x2 of the bobbin 22). Therefore, the displacement x1 of the bobbin 22 when the combined capacitor Cab formed by the pair of fixed electrodes 40A and 40B and the tubular member 33 corresponds to the compensation capacitor C1, and the combined capacitor Cab equivalent compensation are obtained by experiments or the like in advance. The displacement x2 of the bobbin 22 in the case of the capacitor C2 can be based on the difference between the electrostatic capacity of the compensation capacitor C1 and the electrostatic capacitance of the compensation capacitor C2, and the capacitance between the compensation capacitor C1 and the electrostatic capacity of the composite capacitor Cab. The difference is calculated to calculate the displacement x of the spool 22.

‧ Even if the dielectric constant ε between the pair of fixed electrodes 40A and 40B and the tubular member 33 changes, the dielectric constant ε also changes in the compensation capacitors C1 and C2. Therefore, the combined capacitor Cab corresponds to the displacement x1 of the bobbin 22 in the case of compensating the capacitor C1, and the displacement x2 of the bobbin 22 when the combined capacitor Cab corresponds to the compensating capacitor C2 does not change. In addition, even if the electrostatic capacitance of the compensation capacitors C1 and C2 changes due to a change in the capacitance of the adjustment capacitor Ct, the change in the capacitance of the compensation capacitors C1 and C2 tends to be the same. Therefore, according to the compensation The difference between the electrostatic capacitance of the container C1 and the electrostatic capacitance of the compensation capacitor C2, and the difference between the electrostatic capacitance of the compensation capacitor C1 and the electrostatic capacitance of the composite capacitor Cab are used to calculate the displacement x of the bobbin 22, whereby the adjustment can be eliminated. The effect caused by the change in the electrostatic capacity of the capacitor Ct. Therefore, even if the dielectric constant ε between the pair of fixed electrodes 40A and 40B and the tubular member 33 changes, or the capacitance of the compensation capacitor C1 and C2 changes due to the change in the electrostatic capacitance of the adjustment capacitor Ct, it is correct. The displacement x of the bobbin 22 is calculated.

The above embodiment can also be modified as follows. Incidentally, the same members as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

‧ As shown in Fig. 9, the film-shaped electrode 133a may be formed of a conductive material such as silver on the inner surface of the tubular member 133 formed of an insulating material such as ceramic or resin. With such a configuration, the electrode 133a can also function as a movable electrode that faces the fixed electrodes 40A and 40B. In addition, the bobbin 22 is electrically insulated from the electrode 133a.

‧ As shown in FIG. 10, the electrostatic shield 137 is not exposed to the opening 112a of the second body 112, and the end portion 137a of the electrostatic shield 137 is connected by the connection electrode 43 and the connection electrode terminal T3. It is pulled out to the opening portion 112a of the second body 112. The connection electrode 43 and the connection electrode terminal T3 are formed in a film shape on the outer surface portion of the columnar member 31. The end portion 137a of the electrostatic shield 137 is connected to the connection electrode 43, and the connection electrode terminal T3 is connected to the connection electrode 43. The connection electrode terminal T3 is arranged in parallel (parallel) to the compensation electrode terminal T2.

‧ As shown in Fig. 11, an electrostatic shield 237 in which the above-described protruding portion 37b and the communication holes 37c, 37d are not formed may be used. At this time, since the capacitance of the compensation capacitor C1 formed by the compensation electrode 41 and the compensation capacitor C2 formed by the compensation electrode 42 become small, it is preferable that the area of the compensation electrodes 41 and 42 is larger than that of the fixed electrodes 40A and 40B. Larger. According to this configuration, since the compensation electrodes 41 and 42 are not close to the electrostatic shield 237, even if the communication holes 37c and 37d are not formed in the electrostatic shield 237, the dielectric fluid easily flows between the compensation electrodes 41 and 42 and the electrostatic shield 237. Further, the columnar member 31 is attached to the inner side of the electrostatic shield 237 through a holding member 14 made of an insulating material such as ceramic or resin.

‧ As shown in FIG. 12, the compensation electrodes 141 and 142 have a plurality of branching portions 141a and 142a extending in the circumferential direction of the columnar member 31, respectively. The branching portions 141a and 142a are alternately arranged in the longitudinal direction of the columnar member 31. According to this configuration, the difference in dielectric constant between the compensation electrode 141 and the compensation electrode 142 can be suppressed. Therefore, it is possible to suppress the difference between the electrostatic capacitance C1 (ε) of the compensation capacitor C1 and the electrostatic capacitance C2 (ε) of the compensation capacitor C2, and the electrostatic capacitance C1 (ε) and the electrostatic capacitance Cab (ε) of the synthetic capacitor Cab. The difference in accuracy when calculating the displacement x of the bobbin 22 deteriorates.

‧ The columnar member 31 and the tubular member 33 may have a cross-sectional shape corresponding to each other, and a quadrangular cross section or a hexagonal cross section may be employed in addition to the circular cross section. Further, in these cases, in order to keep the electrode interval constant, it is necessary to stop the tubular member. Further, the cross-sectional shape can be arbitrarily changed with respect to the electrostatic shield 37.

In the above embodiment, the entire columnar member 31 is formed of an insulating material. However, the columnar member may be formed of a conductive material, and the outer surface portion may be covered with an insulating material. Further, instead of the columnar member 31, a member formed in a tubular shape may be used.

‧ The fixed electrodes 40A, 40B, the compensation electrodes 41, 42, the fixed electrode terminals Ta, Tb, and the compensation electrode terminals may be fixed by a pattern forming method other than screen printing, for example, a pattern forming method of etching of a vapor deposited film T1 and T2 are formed into a film shape.

In the above embodiment, the fluid chamber 13 is filled with a dielectric fluid such as a chemical liquid. However, the fluid chamber 13 may be filled with a gas such as air or the fluid chamber 13 may be evacuated.

‧ In the above embodiment, the displacement sensor 30 is applied to the valve device 10 having the spool valve 20. However, the displacement sensor 30 may be applied to a valve device having other types of valves such as a poppet valve. . Further, it is not limited to the valve, and the displacement of the other measurement object may be measured by the displacement sensor 30.

‧ As shown in FIG. 13, a communication hole 33c is formed in the tubular member 33. The communication hole 33c is provided in a space inside the tubular member 33 (that is, a space formed between the columnar member 31 and the tubular member 33: the same applies hereinafter), and a space outside the tubular member 33 (that is, formed) The space between the tubular member 33 and the electrostatic shield 37 is the same as the following. In this configuration, the receiving and the supply of the fluid or the like are smoothly performed between the space inside the tubular member 33 and the space outside the tubular member 33. Therefore, according to this configuration, the occurrence of the displacement measurement error of the bobbin 22 due to the change in the spatial dielectric constant of the inside of the tubular member 33 can be more satisfactorily suppressed.

Here, the communication hole 33c is preferably provided at a position corresponding to the upper end portion in the space inside the cylindrical member 33. In particular, the central axis of the tubular member 33 may be inclined with respect to the horizontal plane such that the bottom portion 33a is larger than the opening portion of the cylindrical member 33 (the end portion on the opposite side to the through hole 33b in the longitudinal direction, that is, the drawing) The opening portion of the end portion of the left side of 13 is also high. At this time, the communication hole 33c is a position provided in the space inside the cylindrical member 33, and corresponds to the end portion (the end portion on the opposite side to the opening portion) on the side of the through hole 33b in the longitudinal direction. Thereby, it is possible to satisfactorily suppress the occurrence of measurement errors due to the gas (air bubbles) remaining in the space inside the tubular member 33.

‧ As shown in FIGS. 14 and 15 , the fixed electrodes 40A and 40B may be formed in a comb shape. In this configuration, the electrostatic capacitance change with the displacement of the bobbin 22 is stepped. Therefore, the displacement measurement of the bobbin 22 is performed based on the stepped or pulsed output signal. Therefore, according to this configuration, the displacement measurement of the bobbin 22 can be performed more simply. Further, at this time, the thin electrode-shaped electrode patterns constituting the comb-shaped electrodes in the fixed electrodes 40A and 40B may have the same width. Alternatively, the width of a part of the plurality of thin linear electrode patterns may be different from the others (according to this configuration, the origin detection or calibration of the displacement measurement of the bobbin 22 can be performed favorably).

‧ As shown in FIGS. 16 to 18, the fixed electrodes 40A and 40B are disposed so as not to overlap each other in the central axis direction (long direction) of the columnar member 31. At this time, as shown in FIG. 18, a cylindrical member 133 made of an insulating material such as ceramic or resin is used (see FIG. 9). In this configuration, the electrostatic capacitance between the electrode 133a formed on the inner surface of the cylindrical member 133 and the fixed electrode 40A, and the electrostatic capacitance between the electrode 133a and the fixed electrode 40B are Poor, to measure the displacement of the spool 22. Therefore, in this configuration, the compensation electrodes 41 and 42 can be omitted (see FIG. 1 and the like).

31‧‧‧ Columnar members (rod members)

31a‧‧‧End

31b‧‧‧Exposed Department

40A, 40B‧‧‧ fixed electrode

41‧‧‧Compensation electrode (1st compensation electrode)

42‧‧‧Compensation electrode (2nd compensation electrode)

T1‧‧‧Compensation electrode terminal (1st compensation electrode terminal)

T2‧‧‧Compensation electrode terminal (2nd compensation electrode terminal)

Ta, Tb‧‧‧ fixed electrode terminal

Claims (11)

An electrostatic capacity type displacement sensor comprising: a rod-shaped member having an outer surface portion formed of an insulating material; and a cylindrical member having a predetermined range toward an inner side from a longitudinal end of the rod-shaped member The insertion moves in the longitudinal direction as the measurement object is displaced; the pair of fixed electrodes are formed in a film shape on the outer surface portion of the rod-shaped member, and are opposed to each other with the rod-shaped member interposed therebetween; One movable electrode is provided in the cylindrical member in a state of being insulated from the fixed electrode and the measurement target, and faces the pair of fixed electrodes; and the compensation electrode is formed on the outer surface portion of the rod-shaped member a film shape that does not face the movable electrode; the electrostatic shield covers the electrodes in a state insulated from the fixed electrode, the movable electrode, and the compensation electrode, and is grounded; and the fixed electrode terminal is external to the rod member The surface portion is formed in a film shape, and is connected to each of the fixed electrodes to the outside of the electrostatic shield to be insulated from the electrostatic shield. a state in which the compensation electrode terminal is formed in a film shape on the outer surface portion of the rod-shaped member, and is connected to the compensation electrode to the outside of the electrostatic shield to be insulated from the electrostatic shield. Extends toward the aforementioned long direction. The electrostatic capacitance type displacement sensor of claim 1, wherein the electrostatic shield has a projection that protrudes toward a position approaching the compensation electrode. An electrostatic capacitance type displacement sensor according to claim 2, comprising: a sensor body having a fluid chamber formed therein, the fluid chamber being storable in contact with the fixed electrode, the movable electrode, the compensation electrode, and the protruding portion a dielectric fluid having a communication hole formed in the electrostatic shield, and a space between the compensation electrode and the protruding portion on both sides of the compensation electrode in the longitudinal direction and an outer side of the electrostatic shield in the fluid chamber Space connectivity. The electrostatic capacitance type displacement sensor according to claim 3, wherein an end portion of the rod-shaped member opposite to the predetermined range in the longitudinal direction is annularly formed by an insulating material along an outer circumference of the outer surface portion. Sealed. The electrostatic capacitance type displacement sensor according to claim 4, wherein the electrostatic shield extends in the longitudinal direction and is exposed to an opening of the sensor body, and the rod member is in the longitudinal direction The end portion on the opposite side of the predetermined range and the electrostatic shield are sealed by the insulating material. The electrostatic capacitance type displacement sensor of claim 1, wherein the entirety of the rod-shaped member is formed of an insulating material. The electrostatic capacitance type displacement sensor of claim 1, wherein the entirety of the cylindrical member is formed of a conductive material. The electrostatic capacitance type displacement sensor according to claim 1, wherein the fixed electrode terminal and the compensation electrode terminal are disposed to extend in the longitudinal direction and are close to each other, and the fixed electrode and the compensation electrode are outwardly The surface portion extends in the circumferential direction. The electrostatic capacitance type displacement sensor according to claim 1, wherein an end portion of the rod-shaped member on the predetermined range side in the longitudinal direction is provided with an exposed portion in which the outer surface portion is exposed. The electrostatic capacitance type displacement sensor according to claim 1, wherein the compensation electrode is a first compensation electrode, the compensation electrode terminal is a first compensation electrode terminal, and the capacitance type displacement sensor is provided with: 2nd The compensation electrode is formed in a film shape on the outer surface portion of the rod-shaped member and is larger than the first compensation electrode and does not face the movable electrode; the second compensation electrode terminal is outside the rod-shaped member The surface portion is formed in a film shape, and is connected to the second compensation electrode to the outside of the electrostatic shield, and extends in a state of being insulated from the electrostatic shield; the measurement circuit measures the capacitance between the two electrodes; The switching circuit switches between a first state in which the first compensation electrode terminal and the electrostatic shield are connected to the measurement circuit, a second state in which the second compensation electrode terminal and the electrostatic shield are connected to the measurement circuit, and a second state. The foregoing is connected to each of the aforementioned fixed electrodes a third state in which the fixed electrode terminal is connected to the measurement circuit; and a calculation unit that measures the first electrostatic capacitance and the second static electricity by the measurement circuit in the first state, the second state, and the third state The capacity and the third electrostatic capacitance are calculated based on the difference between the first electrostatic capacitance and the second electrostatic capacitance, and the difference between the first electrostatic capacitance and the third electrostatic capacitance. The electrostatic capacitance type displacement sensor according to claim 10, wherein each of the first compensation electrode and the second compensation electrode has a plurality of branching portions extending in a circumferential direction of the outer surface portion, and the first compensation electrode The branching portion and the branching portion of the second compensation electrode are alternately arranged in the longitudinal direction.