JP6161619B2 - Capacitive displacement sensor - Google Patents

Description

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

  Conventionally, in this type of displacement sensor, a pair of semi-cylindrical fixed electrodes are arranged outside a columnar movable electrode so as to face each other, and the displacement of a valve body connected to the movable electrode is measured ( For example, see Patent Document 1). In the device described in Patent Document 1, the capacitance between the pair of fixed electrodes changes as the movable electrode moves in the axial direction, and the displacement of the valve body is measured from the change in capacitance. Yes.

  Moreover, in the thing of patent document 1, while introducing a dielectric fluid between a movable electrode and a fixed electrode, a pair of compensation electrode is arrange | positioned facing the part which a dielectric fluid distribute | circulates. And the electrostatic capacitance between a pair of compensation electrodes is measured, and the measurement error of the displacement resulting from the change of the dielectric constant of a dielectric fluid is compensated.

  Furthermore, in the thing of patent document 1, a movable electrode and a fixed electrode are covered with the metal electrostatic shield in the electrically insulated state, and the electrostatic shield is electrically grounded. For this reason, even if a user touches the main body of the sensor (the valve device main body including the sensor), it is possible to prevent the capacitance between the pair of fixed electrodes from becoming unstable.

WO2012 / 090583A1

  By the way, in the thing of patent document 1, it is necessary to arrange | position a pair of semi-cylindrical fixed electrode to oppose the outer side of a column-shaped movable electrode. However, it is not easy to accurately arrange a pair of semi-cylindrical fixed electrodes facing each other at a predetermined interval.

  Furthermore, in the thing of patent document 1, the movable electrode and the fixed electrode are covered with the electrostatic shield in the state electrically insulated. For this reason, it is necessary to pull out the fixed electrode and the compensation electrode to the outside of the electrostatic shield by wiring or pins. Therefore, it is inevitable that the structure for drawing out the fixed electrode and the compensation electrode becomes complicated.

  The present invention has been made in view of such circumstances, and a main object of the present invention is to accurately arrange a pair of fixed electrodes at a predetermined interval in a capacitive displacement sensor including an electrostatic shield, It is to facilitate drawing of the electrode to the outside of the shield.

  The present invention employs the following means in order to solve the above problems.

  The first means is a capacitance type displacement sensor, and a rod-shaped member having an outer surface portion formed of an insulating material, and a predetermined range is inserted inside from one end in the longitudinal direction of the rod-shaped member, and a measurement target A pair of fixed electrodes formed in a thin film shape on the outer surface portion of the rod-shaped member and facing each other across the rod-shaped member, and the fixed electrode And is provided in the cylindrical member in a state insulated from the measurement object, and is formed in a thin film on the outer surface portion of the rod-shaped member, and a continuous movable electrode facing the pair of fixed electrodes, A compensation electrode that does not face the movable electrode, an electrostatic shield that covers and grounds the fixed electrode, the movable electrode, and the compensation electrode in a state insulated from the compensation electrode, and the outer surface portion of the rod-shaped member Thin A fixed electrode terminal that is connected to each of the fixed electrodes and extends to the outside of the electrostatic shield in a state of being insulated from the electrostatic shield, and the outer surface portion of the rod-shaped member A compensation electrode terminal formed in a thin film shape on the top and extending in the longitudinal direction in a state of being insulated from the electrostatic shield and connected to the compensation electrode to the outside of the electrostatic shield. .

  According to the said structure, the continuous movable electrode which opposes a pair of fixed electrode in the state insulated from the fixed electrode and the measuring object is provided in the cylindrical member. For this reason, a capacitor is formed between each fixed electrode and the opposed movable electrode, and a composite capacitor is formed in which these capacitors are connected in series by a single movable electrode. And if a cylindrical member moves to the longitudinal direction of a rod-shaped member with the displacement of a measuring object, since the area of the part which a fixed electrode and a movable electrode oppose will change, the electrostatic capacitance of a synthetic | combination capacitor will change. Therefore, the displacement of the measurement target can be measured based on the change in the capacitance of the composite capacitor, that is, the change in the capacitance between the pair of fixed electrodes.

  Further, in addition to the pair of fixed electrodes, a compensation electrode that does not face the movable electrode is formed in a thin film shape on the outer surface portion of the rod-shaped member. Therefore, by measuring the capacitance of the compensation capacitor formed with the compensation electrode as one electrode, it is possible to compensate for the displacement measurement error caused by the change in the dielectric constant between the fixed electrode and the movable electrode. it can.

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

  In addition, the fixed electrode, the movable electrode, and the compensation electrode are covered with an electrostatic shield that is insulated from the electrodes. Since the electrostatic shield is grounded, even if the user touches the main body of the sensor (the main body of the device including the sensor), the electrostatic capacitance between the pair of fixed electrodes is prevented from becoming unstable. Can do.

  Here, the fixed electrode terminal and the compensation electrode terminal which are connected to each fixed electrode and the compensation electrode and extend in the longitudinal direction of the rod-shaped member in a state insulated from the electrostatic shield to the outside of the electrostatic shield are the outer surfaces of the rod-shaped member. Each part is formed in a thin film shape. For this reason, it is possible to draw out the fixed electrode and the compensation electrode to the outside of the electrostatic shield only by forming the fixed electrode terminal and the compensation electrode terminal as a thin film pattern together with the fixed electrode and the compensation electrode. Accordingly, it is possible to facilitate drawing of the electrode to the outside of the electrostatic shield.

  In the second means, the electrostatic shield has a projecting portion that projects to a position close to the compensation electrode.

  According to the above configuration, since the overhanging portion of the electrostatic shield and the compensation electrode are close to each other, a compensation capacitor having a relatively large capacitance can be formed by the compensation electrode and the overhanging portion. Therefore, the electrostatic shield can be used as one electrode of the compensation capacitor, and the accuracy of the compensation capacitor can be improved. Furthermore, it is possible to form a compensation capacitor in a narrow space.

  In the third means, the fixed electrode, the movable electrode, the compensation electrode, and a fluid chamber for storing a dielectric fluid in contact with the overhang portion includes a sensor body formed therein, and the electrostatic shield Is formed with a communication hole for communicating the space between the compensation electrode and the overhanging portion on both sides of the compensation electrode in the longitudinal direction with the space outside the electrostatic shield in the fluid chamber. .

  According to the above configuration, the fluid chamber for storing the dielectric fluid is formed inside the sensor main body, and the dielectric fluid is in contact with the fixed electrode, the movable electrode, the compensation electrode, and the protruding portion of the electrostatic shield. For this reason, 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 overhanging portion can be increased.

  Here, due to the communication hole formed in the electrostatic shield, the space between the compensation electrode and the overhanging portion is different from the space outside the electrostatic shield in the fluid chamber on both sides of the compensation electrode in the longitudinal direction of the rod-shaped member. Communicated. Therefore, it is possible to promote the flow of the dielectric fluid in the space between the compensation electrode and the overhanging portion that are close to each other, and the state of the dielectric fluid in the space between the compensation electrode and the overhanging portion The state of the dielectric fluid in other parts of the chamber can be approached. Therefore, changes in the state of the dielectric fluid, such as changes in dielectric constant due to changes in temperature, liquid quality, etc., can be reflected sensitively to changes in the capacitance of the compensation capacitor, and accuracy to compensate for displacement measurement errors Can be improved.

  In the fourth means, the end of the rod-shaped member opposite to the predetermined range in the longitudinal direction is annularly sealed with an insulating material along the outer periphery of the outer surface portion.

  When the dielectric fluid is in contact with the fixed electrode and the compensation electrode, it is necessary to draw out the fixed electrode and the compensation electrode to the outside of the electrostatic shield while sealing so that the dielectric fluid does not leak to the outside.

  In this regard, according to the above configuration, the end of the rod-shaped member opposite to the predetermined range in the longitudinal direction of the rod-shaped member is annularly sealed with the insulating material along the outer periphery of the outer surface portion. As described above, the fixed electrode terminal and the compensation electrode terminal respectively connected to the fixed electrode and the compensation electrode are formed in a thin film shape on the outer surface portion of the rod-shaped member. For this reason, the thicknesses 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 periphery.

  In the fifth means, the electrostatic shield extends along the longitudinal direction and is exposed at the opening of the sensor body, and the end of the rod-shaped member opposite to the predetermined range in the longitudinal direction; The space between the electrostatic shield and the electrostatic shield is sealed with the insulating material.

  According to the above configuration, since the electrostatic shield extends along the longitudinal direction of the rod-shaped member and is exposed at the opening of the sensor body, the protruding portion of the electrostatic shield that forms one electrode of the compensation capacitor is provided. It can be easily connected to an external electric circuit. And between the edge part on the opposite side to the predetermined range of a rod-shaped member in the longitudinal direction of a rod-shaped member, and the electrostatic shield are sealed with the insulating material. Therefore, the dielectric fluid can be sealed so as not to leak outside while ensuring the insulation between the fixed electrode terminal and the compensation electrode terminal and the electrostatic shield.

  In the sixth means, the whole rod-shaped member is formed of an insulating material.

  According to the said structure, since the whole rod-shaped member is formed with the insulating material, the outer surface part of a rod-shaped member can be easily made into an insulating material, and manufacture of a rod-shaped member can be facilitated.

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

  According to the said structure, since the whole cylindrical member is formed with the electrically-conductive material, the cylindrical member itself functions as a movable electrode, and can connect a movable electrode easily. As a result, the manufacture of the movable electrode can be facilitated.

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

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

  Furthermore, the fixed electrode and the compensation electrode extend in the circumferential direction of the outer surface portion of the rod-shaped member. For this reason, it is possible to efficiently arrange the electrodes while concentrating the electrode terminals, and to secure the area of the electrodes. Therefore, the accuracy of measuring the displacement of the measurement target can be improved.

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

  When the cylindrical member moves in the longitudinal direction of the rod-shaped member in accordance with the displacement of the measurement target, if the cylindrical member is inclined with respect to the rod-shaped member, the fixed electrode and the movable electrode facing each other may come into contact with each other. In this case, the fixed electrode and the movable electrode are likely to come into contact with each other first, particularly at the end of the rod-shaped member and the end of the cylindrical member.

  In this regard, according to the above configuration, the exposed portion where the outer surface portion formed of the insulating material is exposed is provided at the end of the rod-shaped member on the predetermined range side in the longitudinal direction of the rod-shaped member. For this reason, even if the edge part of a rod-shaped member contacts a cylindrical member, it can suppress that a fixed electrode and a movable electrode contact.

  Furthermore, since the fixed electrode is formed in a thin film shape on the outer surface portion of the rod-shaped member, the fixed electrode is formed at the end of the rod-shaped member, or the pattern of the fixed electrode is formed up to the end of the rod-shaped member. The exposed portion can be easily formed by scraping the pattern of the end portion later.

  In the tenth means, the compensation electrode is a first compensation electrode, the compensation electrode terminal is a first compensation electrode terminal, and is thinner than the first compensation electrode in the form of a thin film on the outer surface portion of the rod-shaped member. A second compensation electrode that is formed large and does not oppose the movable electrode, and is formed in a thin film 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, A second compensation electrode terminal extending in the longitudinal direction in a state insulated from the electrostatic shield, a measurement circuit for measuring a capacitance between the two electrodes, the first compensation electrode terminal, and the electrostatic shield. Measuring the first state connected to the measurement circuit, the second state connecting the second compensation electrode terminal and the electrostatic shield to the measurement circuit, and the fixed electrode terminal connected to each of the fixed electrodes. Third shape to connect to the circuit And a switching circuit that switches between the first capacitance, the second capacitance, and the third capacitance, respectively, in the first state, the second state, and the third state. And calculating the displacement of the measurement target based on the difference between the first capacitance and the second capacitance and the difference between the first capacitance and the third capacitance. And comprising.

  According to the said structure, the 2nd compensation electrode larger than a 1st compensation electrode is formed on the outer surface part of a rod-shaped member. The second compensation electrode is drawn out of the electrostatic shield by the second compensation electrode terminal.

  The switching circuit connects each of the first compensation electrode terminal and the electrostatic shield to the measurement circuit, the second state of connecting the second compensation electrode terminal and the electrostatic shield to the measurement circuit, and the fixed electrode. The third state in which the fixed electrode terminal thus connected is connected to the measurement circuit is switched. Then, in the first state, the second state, and the third state, the measurement circuit measures the first capacitance, the second capacitance, and the third capacitance, respectively.

  Here, since the second compensation electrode is formed larger than the first compensation electrode, the facing area between the second compensation electrode and the electrostatic shield is larger than the facing area between the first compensation electrode and the electrostatic shield. That is, the first compensation capacitor formed by the first compensation electrode and the electrostatic shield corresponds to a state where the facing area between the pair of fixed electrodes and the movable electrode is small (a state where 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 where the facing area between the pair of fixed electrodes and the movable electrode is large (a state where 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 electrode and movable electrode corresponds to the first compensation capacitor and the displacement of the measurement target when the composite capacitor corresponds to the second compensation capacitor The displacement of the measurement target is calculated based on the difference between the first capacitance and the second capacitance, and the difference between the first capacitance and the third capacitance by obtaining in advance through experiments or the like. can do.

  Furthermore, even if the dielectric constant between the pair of fixed electrodes and the movable electrode changes, the dielectric constant also changes in the first compensation capacitor and the second compensation capacitor. For this reason, the displacement of the measurement target when the composite capacitor corresponds to the first compensation capacitor and the displacement of the measurement target when the composite capacitor corresponds to the second compensation capacitor do not change. Further, even if the capacitances of the first compensation capacitor and the second compensation capacitor are changed due to a change in the capacitance of the adjustment capacitor or the like used in the measurement of the capacitance, the first compensation capacitor and the second compensation capacitor The change in the capacitance of the compensation capacitor has the same tendency. Therefore, the adjustment capacitor is calculated by calculating the displacement of the measurement object based on the difference between the first capacitance and the second capacitance and the difference between the first capacitance and the third capacitance. It is possible to cancel the influence due to the change in the electrostatic capacitance. Therefore, regardless of changes in the dielectric constant between the pair of fixed electrodes and the movable electrode, and changes in the capacitances of the first compensation capacitor and the second compensation capacitor due to changes in the capacitance of the adjustment capacitors and the like. The displacement of the measurement object can be accurately calculated.

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

  When a temperature difference occurs between the first compensation electrode and the second compensation electrode, there is a possibility that a difference in dielectric constant occurs between the capacitor formed by the first compensation electrode and the capacitor formed by the second compensation electrode. As a result, when calculating the displacement of the measurement object based on the difference between the first capacitance and the second capacitance and the difference between the first capacitance and the third capacitance, the calculation of the displacement is performed. The accuracy may be reduced.

  In this regard, according to the above configuration, each of the first compensation electrode and the second compensation electrode has a plurality of branch portions extending in the circumferential direction of the outer surface portion of the rod-shaped member. And since the branch part of the 1st compensation electrode and the branch part of the 2nd compensation electrode are alternately arranged in the longitudinal direction of a rod-shaped member, a temperature difference arises with the 1st compensation electrode and the 2nd compensation electrode. Can be suppressed. Therefore, it can suppress that the precision which calculates the displacement of a measuring object falls.

FIG. 6 is a partial cross-sectional view showing a part of a capacitance type displacement sensor and a spool valve. The side view of the displacement sensor of FIG. The front view which shows a columnar member and an electrode. The expanded view which expands and shows the electrode of FIG. The schematic diagram which shows typically the capacitor | condenser formed in each part of the displacement sensor of FIG. FIG. 6 is an electric circuit diagram showing an equivalent circuit of FIG. 5. The block diagram which shows the electric constitution of the displacement sensor of FIG. The graph which shows the relationship between the displacement of a spool, and an electrostatic capacitance. The fragmentary sectional view which shows the example of a change of a cylindrical member and a movable electrode. The fragmentary sectional view which shows the example of a change of an electrostatic shield. The fragmentary sectional view which shows the other example of a change of an electrostatic shield. The front view which shows the example of a change of a compensation electrode. The fragmentary sectional view which shows the example of a change of a cylindrical member. The front view which shows the example of a change of a fixed electrode. The expanded view which expands and shows the electrode of FIG. The front view which shows the example of a change of a fixed electrode. The expanded view which expands and shows the electrode of FIG. The fragmentary sectional view which shows the structure of the displacement sensor using the fixed electrode shown in FIG.

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

  FIG. 1 is a partial cross-sectional view showing a part of the capacitive displacement sensor 30 and the spool valve 20. As shown in the figure, the valve device 10 includes a first main body 11, a second main body 12, a spool valve 20, a capacitive displacement sensor 30, and the like. The 1st main body 11 and the 2nd main body 12 are shape | molded by the metals, such as stainless steel, in the square cylinder shape (cylindrical shape) which has a cylindrical space inside. The second main body 12 is attached to the end of the first main body 11 so that the respective central axes coincide with each other, and the space between the first main body 11 and the second main body 12 is sealed with a seal member. A spool valve 20 and a displacement sensor 30 are accommodated in the first main body 11 and the second main body 12. The spool valve 20 and the displacement sensor 30 are arranged side by side in the central axis direction (longitudinal direction) of the first main body 11. The first main body 11 has a fluid inlet 11a and an outlet 11b.

  The spool valve 20 includes a sleeve 21, a spool 22, an actuator (not shown), and the like. The sleeve 21 and the spool 22 are formed of a metal such as stainless steel. The sleeve 21 is formed in a cylindrical shape (tubular shape), and the spool 22 is formed in a columnar shape (columnar shape). The sleeve 21 and the spool 22 are formed with corresponding cross-sectional shapes, and the spool 22 is slidably inserted into the sleeve 21. A through hole 22 b extending in the central axis direction (longitudinal direction) is formed inside the spool 22.

  In the sleeve 21, communication holes 21 a and 21 b are formed at positions corresponding to the inlet 11 a and the outlet 11 b of the first main body 11, respectively. The communication holes 21a and 21b extend in the circumferential direction of the sleeve 21, and allow the inside and the outside of the sleeve 21 to communicate with each other. The spool 22 is formed with an annular groove 22a extending in the circumferential direction with a width corresponding to the interval between the communication holes 21a and 21b of the sleeve 21. The spool 22 (measurement target) is connected to an actuator such as an electromagnetic actuator, and is reciprocated in the central axis direction (longitudinal direction) by the actuator. As a result, the communication between the communication hole 21a and the communication hole 21b of the sleeve 21 is blocked by the outer peripheral surface of the spool 22, and the communication hole 21a and the communication hole 21b are communicated by the groove 22a of the spool 22. Be controlled.

  A displacement sensor 30 is accommodated in the first main body 11 and the second main body 12. The displacement sensor 30 includes a columnar member 31, a cylindrical member 33, a connecting member 35, an electrostatic shield 37, and the like.

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

  A through hole 33 b extending in the central axis direction (longitudinal direction) of the cylindrical member 33 is formed in the bottom 33 a of the cylindrical member 33. The through hole 22b of the spool 22 and the through hole 33b of the bottom 33a communicate with each other through a cylindrical connecting member 35. That is, the inside of the spool 22 communicates with the inside of the cylindrical member 33.

  The columnar member 31 (bar-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 electrodes 40A, 40B, a compensation electrode 41 (first compensation electrode), and a compensation electrode 42 (second compensation electrode) are formed in a thin film shape. A predetermined range from one end in the central axis direction (longitudinal direction) of the columnar member 31, specifically, a portion corresponding to the fixed electrodes 40 </ b> A and 40 </ b> B is inserted into the cylindrical member 33. The columnar member 31 and the cylindrical member 33 have the same center axis. A predetermined clearance (gap) is formed between the fixed electrodes 40 </ b> A and 40 </ b> B (columnar member 31) and the cylindrical member 33. That is, the fixed electrodes 40A and 40B and the cylindrical member 33 are opposed to each other in an electrically insulated state.

  On the outer periphery of the columnar member 31 and the cylindrical member 33, the fixed electrodes 40 </ b> A and 40 </ b> B, the compensation electrodes 41 and 42, and the electrostatic shield 37 that covers the cylindrical member 33 are provided. The electrostatic shield 37 is formed in a cylindrical shape (cylindrical shape) from 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 cylindrical member 33.

  A space between the outer peripheral surface of the end portion 37a of the electrostatic shield 37 and the inner peripheral surface of the second main body 12 is annularly sealed (sealed) along the circumferential direction by the low melting point glass 51 (insulating material). (See FIG. 2). Thereby, the electrostatic shield 37 is attached to the second main body 12 in a state of being electrically insulated from the second main body 12. The end 31 a of the columnar member 31 is exposed to the outside of the electrostatic shield 37, that is, the opening 12 a of the second main body 12. The space between 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 is annularly sealed along the circumferential direction by a low melting point glass 52 (insulating material) ( (See FIG. 2). Thereby, the columnar member 31 is attached to 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 in the central axis direction (longitudinal direction), and an end portion 37 a of the electrostatic shield 37 is exposed to the opening 12 a of the second main body 12. A wiring (not shown) is connected to the end 37a of the electrostatic shield 37, and the electrostatic shield 37 is grounded by the wiring.

  A fluid chamber 13 for storing fluid is formed in the first main body 11 and the second main body 12. The fluid chamber 13 is partitioned by the first main body 11, the second main body 12, the sleeve 21, the spool 22, the electrostatic shield 37, and the columnar member 31. The fluid whose flow is controlled by the spool valve 20 flows into the fluid chamber 13 from the clearance (gap) between the inner peripheral surface of the sleeve 21 and the outer peripheral surface of the spool 22. The interior 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. A fluid composed of a chemical solution is a dielectric, and functions as a dielectric fluid. The first main body 11 and the second main body 12 constitute a sensor main body of the displacement sensor 30.

  In the electrostatic shield 37, a protruding portion 37 b that protrudes toward the compensation electrodes 41 and 42 is formed at a portion facing the compensation electrodes 41 and 42. The overhang portion 37 b projects in a ring shape to a position close to the compensation electrodes 41 and 42. The compensation electrodes 41 and 42 do not face the cylindrical member 33.

  The electrostatic shield 37 is formed with communication holes 37 c and 37 d that allow the inside and the outside of the electrostatic shield 37 to communicate with each other in the fluid chamber 13. The communication holes 37 c and 37 d are formed on both sides of the compensation electrodes 41 and 42 in the central axis direction (longitudinal direction) of the columnar member 31. Specifically, the communication holes 37c and 37d are formed at both ends of a 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, respectively.

  Next, the configuration of the pair of fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 will be described in detail. 3 is a front view showing the columnar member 31, the fixed electrodes 40A and 40B, and the compensation electrodes 41 and 42, and FIG. 4 is a development view showing the electrodes 40A, 40B, 41, and 42 in FIG. .

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

  Fixed electrode terminals Ta and Tb are connected to portions where the fixed electrode 40A and the fixed electrode 40B are adjacent to each other. The fixed electrode terminals Ta and Tb extend to the end 31 a in the longitudinal direction of the columnar member 31. Further, the fixed electrode terminals Ta and Tb extend to the end face of the end portion 31a (see FIG. 2). For this reason, 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 main body 12 (see FIG. 1). The fixed electrode terminals Ta and Tb are arranged close to each other in parallel (parallel).

  The compensation electrode 42 is formed in a range adjacent to the range where the fixed electrodes 40 </ b> A and 40 </ b> B are formed in the central axis direction (longitudinal direction) of the columnar member 31. The compensation electrode 42 extends in the circumferential direction of the outer surface portion of the columnar member 31. The compensation electrode 42 is formed in a cylindrical shape on the outer surface portion of the columnar member 31.

  A compensation electrode terminal T2 is connected to a portion of the compensation electrode 42 adjacent to the fixed electrode terminal Ta. The compensation electrode terminal T <b> 2 (second compensation electrode terminal) extends to the end 31 a in the longitudinal direction of the columnar member 31. Furthermore, the compensation electrode terminal T2 extends to the end surface of the end portion 31a (see 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 main body 12 (see FIG. 1). The compensation electrode terminal T2 is disposed in parallel (parallel) in proximity to the fixed electrode terminal Ta.

  The compensation electrode 41 is formed in a range adjacent to the range where the compensation electrode 42 is formed in the central axis direction (longitudinal direction) of the columnar member 31. 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 larger than the area of the compensation electrode 41.

  A compensation electrode terminal T1 is connected to a portion of the compensation electrode 41 adjacent to the fixed electrode terminal Tb. The compensation electrode terminal T <b> 1 (first compensation electrode terminal) extends to the end 31 a in the longitudinal direction of the columnar member 31. Further, the compensation electrode terminal T1 extends to the end face of the end portion 31a (see FIG. 2). For this reason, the compensation electrode terminal T1 is exposed to the outside of the electrostatic shield 37, that is, the opening 12a of the second main body 12 (see FIG. 1). The compensation electrode terminal T1 is arranged in parallel (parallel) close to the fixed electrode terminal Tb.

  The electrodes 40A, 40B, 41, and 42 and the terminals Ta, Tb, T1, and T2 are formed in a thin film shape by screen-printing and baking a paste containing a conductive material such as silver. That is, the electrodes 40A, 40B, 41, and 42 and the terminals Ta, Tb, T1, and T2 are formed by printing a conductive material using a screen mask on which an electrode pattern is formed.

  The terminals Ta, Tb, T1, and T2 are concentrated at one place in the circumferential direction of the outer surface portion of the columnar member 31. In the electrostatic shield 37, concave portions 37e are formed in portions facing these terminals Ta, Tb, T1, and T2 (see FIG. 2). The recess 37e extends in the central axis direction (longitudinal direction) of the columnar member 31 along the terminals Ta, Tb, T1, and T2. The depth of the recess 37e is set deeper than the thickness of the thin film terminals Ta, Tb, T1, T2. Thereby, the distance between the terminals Ta, Tb, T1, T2 and the electrostatic shield 37 is ensured, and the terminals Ta, Tb, T1, T2 and the electrostatic shield 37 are insulated. The low melting point glass 52 is also introduced into the recess 37e, and the space between the columnar member 31 and the electrostatic shield 37 is sealed. That is, the electrodes 40 </ b> A, 40 </ b> B, 41, 42 are drawn out of the electrostatic shield 37 while sealing so that the fluid does not leak from the fluid chamber 13.

  Next, in the capacitance type displacement sensor 30, a capacitor for measuring capacitance and a capacitor formed in other portions will be described. FIG. 5 is a schematic diagram schematically showing capacitors formed in each part in the displacement sensor 30 of FIG. FIG. 6 is an electric circuit diagram showing the equivalent circuit of FIG.

  As shown in the figure, the fixed electrode 40A and the cylindrical member 33 form a capacitor Ca, and the fixed electrode 40B and the cylindrical member 33 form a capacitor Cb. Since the cylindrical member 33 has a continuous shape, the capacitor Ca and the capacitor Cb are connected in series by the cylindrical member 33. A synthetic capacitor Cab is formed by the capacitors Ca and Cb.

  Here, in the spool valve 20, when the spool 22 is moved by driving the actuator, the cylindrical member 33 connected to the spool valve 20 is moved in the central axis direction (longitudinal direction). As a result, the area of the portion where the fixed electrodes 40A, 40B and the cylindrical member 33 face each other changes, and the capacitance C of the composite capacitor Cab changes. That is, the relationship C = ε × S / d is established. C is the capacitance of the capacitor, ε is the dielectric constant, S is the electrode area, and d is the distance between the electrodes. The inter-electrode distance d is a known constant value, and the electrode area S changes corresponding to the displacement of the spool 22. Therefore, by measuring the capacitance between the fixed electrode terminal Ta and the fixed electrode terminal Tb, the displacement of the spool 22 can be measured based on the change in the capacitance.

  When the cylindrical member 33 is tilted with respect to the columnar member 31 when the cylindrical member 33 moves in the central axis direction (longitudinal direction) of the columnar member 31 with the displacement of the spool 22, the fixed electrodes 40 </ b> A facing each other. There is a possibility that 40B and the tubular member 33 come into contact with each other. In this case, the fixed electrodes 40 </ b> A and 40 </ b> B and the tubular member 33 are likely to contact each other at the end of the columnar member 31 and the end of the tubular member 33 in the first place.

  In this regard, an exposed portion 31b where the fixed electrodes 40A and 40B are not formed is provided at the end of the columnar member 31 in the longitudinal direction of the columnar member 31. For this reason, even if the exposed part 31b contacts the cylindrical member 33, it can suppress that fixed electrode 40A, 40B and the cylindrical member 33 contact.

  The compensation electrode 41 and the overhanging portion 37b of the electrostatic shield 37 form a compensation capacitor C1 (first compensation capacitor), and the compensation electrode 42 and the overhanging portion 37b form a compensation capacitor C2 (second compensation capacitor). Is formed. As described above, the space between the fixed electrodes 40A and 40B and the cylindrical member 33 and the space between the compensation electrodes 41 and 42 and the overhanging portion 37b of the electrostatic shield 37 are filled with a fluid made of a dielectric. .

  Here, when the state of the fluid (temperature and liquid quality) changes, the dielectric constant ε of the fluid changes, and the capacitance of the composite capacitor Cab changes. At this time, the capacitances of the compensation capacitors C1 and C2 also change 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 acquired in advance by design values or actual measurements. Therefore, by measuring the 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 C = ε × S / d. it can. Then, by measuring the capacitance of the composite capacitor Cab using the calculated dielectric constant ε, the measurement error of the displacement of the spool 22 due to the change in the dielectric constant of the fluid can be compensated.

  Furthermore, communication holes 37 c and 37 d are formed in the electrostatic shield 37. Therefore, the space between the compensation electrodes 41 and 42 and the protruding portion 37 b of the electrostatic shield 37 communicates with the outside of the electrostatic shield 37 on both sides of the compensation electrodes 41 and 42 in the longitudinal direction of the columnar member 31. ing. 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, respectively. Accordingly, even if the compensation electrodes 41 and 42 and the overhang portion 37b are close to each other, the fluid can be circulated between the compensation electrodes 41 and 42 and the overhang portion 37b. As a result, the state of the fluid between the compensation electrodes 41 and 42 and the overhang portion 37b can be brought close to the state of the fluid in the other part of the fluid chamber 13, and the accuracy of compensating for the measurement error of the displacement of the spool 22 can be obtained. Can be improved.

  The electrodes 40A, 40B, 41, and 42 are covered with an electrostatic shield 37, and the electrostatic shield 37 is grounded. For this reason, even if a user touches the main bodies 11 and 12 and the charge state and electrostatic capacity Cn of the main bodies 11 and 12 change, the influence of the influence on the electrodes 40A, 40B, 41 and 42 is suppressed. can do.

  The fixed electrode 40A and the electrostatic shield 37 form a capacitor Cas. In addition, a capacitor Cc is formed in a portion where the fixed electrode 40A and the fixed electrode 40B are close to each other, and a capacitor Cms is formed by the cylindrical member 33 and the electrostatic shield 37. The capacitances of these capacitors Cas, Cc, Cms are very small compared to the capacitances of the capacitors Ca, Cb, Cab, C1, C2.

  Next, the electrical configuration of the displacement sensor 30 of FIG. 1 will be described with reference to FIG. The displacement sensor 30 includes a capacitance measurement circuit 61 and a switch circuit 62.

  The capacitance measuring circuit 61 is a known circuit that measures the 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 such as CMOS, and can be switched ON and OFF at high speed by the MC 64. The capacitance measuring circuit 61 includes an adjustment capacitor Ct used for adjustment in capacitance measurement. The capacitance of the adjustment capacitor Ct is not related to the dielectric constant of the fluid, and changes due to other factors such as a change in environmental temperature.

  Then, the switch SW1 is turned on and the switches SW2 and SW3 are turned off, whereby the compensation electrode terminal T1 and the electrostatic shield terminal Ts are connected to the capacitance measuring circuit 61. By switching the switch SW2 to ON and the switches SW1 and SW3 to OFF, the second state in which the compensation electrode terminal T2 and the electrostatic shield terminal Ts are connected to the capacitance measuring circuit 61 is obtained. By switching the switch SW3 to ON and the switches SW1 and SW2 to OFF, the third state is reached in which the fixed electrode terminals Ta and Tb are connected to the capacitance measuring circuit 61.

  In the first state, the first capacitance that is the capacitance C1 (ε) of the compensation capacitor C1 is measured by the capacitance measurement circuit 61. In the second state, the second capacitance that is the capacitance C2 (ε) of the compensation capacitor C2 is measured by the capacitance measurement circuit 61. In the third state, the capacitance measurement circuit 61 measures the third capacitance, which is the capacitance Cab (ε) of the composite capacitor Cab. The measured capacitances C1 (ε), C2 (ε), and Cab (ε) are transmitted from the capacitance measurement circuit 61 to the MC 64 of the switch circuit 62.

  FIG. 8 shows the relationship between the displacement of the spool 22 and the electrostatic capacity Cab (ε) of the composite capacitor Cab. As shown in the figure, the capacitance Cab (ε) is proportional to the displacement of the spool 22. In other words, the capacitance Cab (ε) is proportional to the area of the portion where the fixed electrodes 40A, 40B and the cylindrical member 33 face each other. FIG. 1 shows a state where the displacement of the spool 22 is the largest, that is, a state where the area of the portion where the fixed electrodes 40A and 40B and the cylindrical member 33 face each other is the largest.

  Here, when the dielectric constant of the fluid is εa, as indicated by the solid line, at the displacement x1 of the spool 22, the capacitance Cap (εa) of the composite capacitor Cab is equal to the capacitance C1 (εa) of the compensation capacitor C1. Are equal. Further, at the displacement x2 of the spool 22, the electrostatic capacity Cab (εa) of the composite capacitor Cab is equal to the electrostatic capacity C2 (εa) of the compensation capacitor C2.

  That is, the compensation capacitors C1 and C2 are set so that the compensation capacitor C1 corresponds to the displacement x1 of the synthesis capacitor Cab and the compensation capacitor C2 corresponds to the displacement x2 of the synthesis capacitor Cab. These displacements x1 and x2 can be obtained in advance by experiments or the like. Then, the capacitances C1 (εa), C2 (εa), and Cab (εa) are measured, and the capacitance Cab (εa) is in a straight line passing through the capacitance C1 (εa) and the capacitance C2 (εa). Can be applied to measure the displacement x of the spool 22.

  When the dielectric constant of the fluid changes to εb, as indicated by a broken line, at the displacement x1 of the spool 22, the capacitance Cab (εb) of the composite capacitor Cab is equal to the capacitance C1 (εb) of the compensation capacitor C1. Will be equal. Further, at the displacement x2 of the spool 22, the electrostatic capacity Cab (εb) of the composite capacitor Cab becomes equal to the electrostatic capacity C2 (εb) of the compensation capacitor C2. In this case, since the dielectric constant of the fluid similarly changes by εb in the composite capacitor Cab and the compensation capacitors C1 and C2, the displacement x1 of the spool 22 when the composite capacitor Cab corresponds to the compensation capacitor C1, and the composite capacitor The displacement x2 of the spool 22 when Cab corresponds to the compensation capacitor C2 does not change.

  Further, as described above, the capacitance of the adjusting capacitor Ct of the capacitance measuring circuit 61 is not related to the dielectric constant of the fluid, and changes due to other factors such as a change in environmental temperature. For this reason, when the dielectric constant of the fluid is εa, for example, when the capacitance of the adjustment capacitor Ct increases, the capacitances C1 (εa) and C2 (εa) of the compensation capacitors C1 and C2 respectively have capacitances. It increases to C1m (εa) and C2m (εa). As a result, as indicated by the alternate long and short dash line, the relationship between the displacement of the spool 22 and the electrostatic capacity Cab (εa) of the composite capacitor Cab deviates from the relationship indicated by the solid line. Therefore, the accuracy of measuring the displacement of the spool 22 may be reduced due to the change in the capacitance of the adjustment capacitor Ct.

  In this regard, in this embodiment, the MC 64 (calculation unit) calculates the difference between 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 the displacement of the spool 22 are calculated based on the difference between the capacitance of the composite capacitor Cab and the capacitance Cab (ε). That is, the difference between the capacitance C1 (ε) and the capacitance C2 (ε) corresponds to the change from the displacement x1 to the displacement x2, and the capacitance C1 (ε) and the capacitance Cab (ε). Displacement x corresponding to the difference is calculated.

  Here, even if the capacitances C1 (ε) and C2 (ε) of the compensation capacitors C1 and C2 change due to the change in the capacitance of the adjustment capacitor Ct, the capacitances C1 (ε) and C2 The change in (ε) has a similar tendency. For example, an alternate long and short dash line passing through the capacitances C1m (εa) and C2m (εa) is a straight line obtained by translating a solid line passing through the capacitances C1 (εa) and C2 (εa). Therefore, the displacement x of the spool 22 is based on the difference between the capacitance C1 (ε) and the capacitance C2 (ε) and the difference between the capacitance C1 (ε) and the capacitance Cab (ε). , The influence on the capacitances C1 (ε) and C2 (ε) due to the change in the capacitance of the adjustment capacitor Ct can be canceled out.

  The embodiment described in detail above has the following advantages.

  In addition to the pair of fixed electrodes 40 </ b> A and 40 </ b> B, compensation electrodes 41 and 42 that do not face the cylindrical member 33 are formed in a thin film shape on the outer surface portion of the columnar member 31. For this reason, the change of the dielectric constant ε between the fixed electrodes 40A, 40B and the cylindrical member 33 is measured by measuring the capacitance of the compensation capacitors C1, C2 formed with the compensation electrodes 41, 42 as one electrode. It is possible to compensate for the measurement error of the displacement x caused by the above.

  The pair of fixed electrodes 40A and 40B facing each other with the columnar member 31 in between are formed in a thin film shape on the outer surface portion of the columnar member 31 formed of an insulating material. For this reason, it is not necessary to arrange a pair of fixed electrodes formed as separate members from each other, and the pair of fixed electrodes 40A and 40B can be formed as a thin film pattern on the outer surface portion of one columnar member 31. it can. Therefore, the interval between the pair of fixed electrodes 40A and 40B is defined by the dimensions of the columnar member 31, and the pair of fixed electrodes 40A and 40B can be accurately arranged at a predetermined interval.

  The fixed electrodes 40A and 40B, the cylindrical member 33, and the compensation electrodes 41 and 42 are covered with an electrostatic shield 37 that is insulated from these electrodes. Since the electrostatic shield 37 is grounded, the capacitance between the pair of fixed electrodes 40A and 40B becomes unstable even if the user touches the sensor bodies 11 and 12 and the spool valve 20 body. It can be suppressed.

  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 in the longitudinal direction of the columnar member 31 while being insulated from the electrostatic shield 37 to the outside of the electrostatic shield 37. The fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 are each formed in a thin film shape on the outer surface portion of the columnar member 31. For this reason, the fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 together with the fixed electrodes 40A and 40B and the compensation electrodes 41 and 42 are fixed to the outside of the electrostatic shield 37 only by forming a thin film pattern. The electrodes 40A and 40B and the compensation electrodes 41 and 42 can be drawn out, respectively. Therefore, the extraction of the electrodes 40A, 40B, 41, 42 to the outside of the electrostatic shield 37 can be facilitated.

  Since the overhanging portion 37b of the electrostatic shield 37 and the compensation electrodes 41 and 42 are close to each other, the compensation electrodes 41 and 42 and the overhanging portion 37b provide compensation capacitors C1 and C2 having a relatively large capacitance. Can be formed. Therefore, the electrostatic shield 37 can be used as one electrode of the compensation capacitors C1 and C2, and the accuracy of the compensation capacitors C1 and C2 can be improved. Further, the compensation capacitors C1 and C2 can be formed in a narrow space.

  A fluid chamber 13 for storing a dielectric fluid is formed inside the main bodies 11 and 12, and the fixed electrodes 40A and 40B, the cylindrical member 33, the compensation electrodes 41 and 42, and the overhanging portion 37b of the electrostatic shield 37 A dielectric fluid contacts the surface. For this reason, the capacitances of the composite capacitor Cab formed by the fixed electrodes 40A and 40B and the cylindrical member 33 and the compensation capacitors C1 and C2 formed by the compensation electrodes 41 and 42 and the overhang portion 37b are increased. be able to. Furthermore, a fluid whose flow is controlled by the spool valve 20 can be used as a dielectric.

  The communication holes 37 c and 37 d formed in the electrostatic shield 37 allow the space between the compensation electrodes 41 and 42 and the overhanging portion 37 b to be fluid on both sides of the compensation electrodes 41 and 42 in the longitudinal direction of the columnar member 31. The chamber 13 communicates with the space outside the electrostatic shield 37. For this reason, it is possible to promote the flow of the dielectric fluid in the space between the compensation electrodes 41 and 42 and the overhanging portion 37b that are close to each other, and in the space between the compensation electrodes 41 and 42 and the overhanging portion 37b. The state (temperature and liquid quality) of the dielectric fluid can be brought close to the state of the dielectric fluid in the other part 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 reflected sensitively to the changes in the capacitances C1 (ε) and C2 (ε) of the compensation capacitors C1 and C2, and the displacement x is measured. The accuracy of compensating for the error can be improved.

  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, respectively. For this reason, the state of the dielectric fluid between the fixed electrodes 40A and 40B and the cylindrical member 33 can be brought close to the state of the dielectric fluid between the compensation electrodes 41 and 42 and the overhang portion 37b. Therefore, the measurement error of the displacement x of the spool 22 due to the change in the state (dielectric constant) of the dielectric fluid can be compensated with higher accuracy.

  The end portion 31a of the columnar member 31 is annularly sealed with an insulating material along the outer periphery of the outer surface portion. 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, respectively, are formed into a thin film on the outer surface portion of the columnar member 31. Is formed. For this reason, the thicknesses 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 periphery.

  Since the electrostatic shield 37 extends along the longitudinal direction of the columnar member 31 and is exposed to the opening 12a of the second main body 12, the electrostatic shield 37 that forms one electrode of the compensation capacitors C1 and C2 The overhang portion 37b can be easily connected to an external electric circuit. The space between the end 31a of the columnar member 31 and the electrostatic shield 37 is sealed with an insulating material. Therefore, it is possible to seal the dielectric fluid from leaking to the outside while ensuring insulation between the fixed electrode terminals Ta and Tb and the compensation electrode terminals T1 and T2 and the electrostatic shield 37.

  In the electrostatic shield 37, a concave portion 37e is formed in a portion facing the terminals Ta, Tb, T1, and T2. The recess 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 secured, and the terminals Ta, Tb, T1, T2 and the electrostatic shield 37 can be more reliably insulated.

  -Since the whole columnar member 31 is formed of the insulating material, the outer surface part of the columnar member 31 can be easily made into an insulating material, and manufacture of the columnar member 31 can be facilitated.

  -Since the whole cylindrical member 33 is formed of a conductive material, the cylindrical member 33 itself functions as a movable electrode, and the movable electrodes can be easily connected. 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 extend in the longitudinal direction of the columnar member 31 and are arranged close to each other. For this reason, an electrode terminal can be concentrated and each electrode terminal can be easily connected to an external electric 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 electrodes 40A, 40B, 41, and 42 can be efficiently arranged while concentrating the electrode terminals Ta, Tb, T1, and T2, and the area of the electrodes 40A, 40B, 41, and 42 is ensured. Can do. Therefore, the accuracy of measuring the displacement x of the spool 22 can be improved.

  In the longitudinal direction of the columnar member 31, an exposed portion 31b where an outer surface portion formed of an insulating material is exposed is provided at the end of the columnar member 31 on the fixed electrode 40A, 40B side. For this reason, even if the edge part of the columnar member 31 contacts the cylindrical member 33, it can suppress that fixed electrode 40A, 40B and the cylindrical member 33 contact.

  Since the fixed electrodes 40A and 40B are formed in a thin film shape on the outer surface portion of the columnar member 31, the fixed electrodes 40A and 40B are not formed on the end portion of the columnar member 31, or the end portions of the columnar member 31 are formed. The exposed portion 31b can be easily formed by cutting the end portion pattern after forming the patterns of the fixed electrodes 40A and 40B.

  Since the compensation electrode 42 is formed larger than the compensation electrode 41, the facing area between the compensation electrode 42 and the electrostatic shield 37 is larger than the facing area between the compensation electrode 41 and the electrostatic shield 37. That is, the compensation capacitor C1 formed by the compensation electrode 41 and the electrostatic shield 37 corresponds to a state where the opposed area between the pair of fixed electrodes 40A and 40B and the cylindrical member 33 is small (displacement x1 of the spool 22). Further, the compensation capacitor C2 formed by the compensation electrode 42 and the electrostatic shield 37 corresponds to a state where the facing area between the pair of fixed electrodes 40A and 40B and the cylindrical member 33 is large (displacement x2 of the spool 22). Therefore, when the combined capacitor Cab formed by the pair of fixed electrodes 40A and 40B and the cylindrical member 33 corresponds to the compensation capacitor C1, the displacement x1 of the spool 22 and the combined capacitor Cab correspond to the compensation capacitor C2. The displacement x2 of the spool 22 is previously determined by experiment or the like, so that the difference between the capacitance of the compensation capacitor C1 and the capacitance of the compensation capacitor C2, and the capacitance of the compensation capacitor C1 and the static capacitance of the composite capacitor Cab. Based on the difference from the electric capacity, the displacement x of the spool 22 can be calculated.

  Even if the dielectric constant ε between the pair of fixed electrodes 40A and 40B and the cylindrical member 33 changes, the dielectric constant ε also changes in the compensation capacitors C1 and C2. Therefore, the displacement x1 of the spool 22 when the combined capacitor Cab corresponds to the compensation capacitor C1 and the displacement x2 of the spool 22 when the combined capacitor Cab corresponds to the compensation capacitor C2 do not change. Further, even if the capacitances of the compensation capacitors C1 and C2 change due to the change in the capacitance of the adjustment capacitor Ct, the change in the capacitances of the compensation capacitors C1 and C2 has the same tendency. For this reason, the displacement x of the spool 22 is based on the difference between the capacitance of the compensation capacitor C1 and the capacitance of the compensation capacitor C2, and the difference between the capacitance of the compensation capacitor C1 and the capacitance of the composite capacitor Cab. Can be used to cancel the influence of the change in the capacitance of the adjustment capacitor Ct. Therefore, the change in the dielectric constant ε between the pair of fixed electrodes 40A, 40B and the cylindrical member 33 and the change in the capacitance of the compensation capacitors C1, C2 due to the change in the capacitance of the adjustment capacitor Ct. Regardless, the displacement x of the spool 22 can be accurately calculated.

  The above embodiment can also be implemented with the following modifications. In addition, about the member same as the said embodiment, description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  As shown in FIG. 9, a thin-film electrode 133a may be formed on the inner surface of a cylindrical member 133 made of an insulating material such as ceramics or resin, using a conductive material such as silver. Also with such a configuration, the electrode 133a can function as a movable electrode facing the fixed electrodes 40A and 40B. The spool 22 and the electrode 133a are electrically insulated.

  As shown in FIG. 10, the electrostatic shield 137 is not exposed in the opening 112a of the second main body 112, and the end 137a of the electrostatic shield 137 is connected to the second by the connection electrode 43 and the connection electrode terminal T3. A configuration in which the main body 112 is drawn to the opening 112a can also be adopted. The connection electrode 43 and the connection electrode terminal T3 are formed in a thin film shape on the outer surface portion of the columnar member 31. An end 137 a of the electrostatic shield 137 is connected to the connection electrode 43, and the connection electrode terminal T 3 is connected to the connection electrode 43. The connection electrode terminal T3 is arranged in parallel (parallel) close to the compensation electrode terminal T2.

  As shown in FIG. 11, the electrostatic shield 237 in which the overhang portion 37b and the communication holes 37c and 37d described above are not formed can also be used. In this case, since the capacitances of the compensation capacitor C1 formed by the compensation electrode 41 and the compensation capacitor C2 formed by the compensation electrode 42 are reduced, the areas of the compensation electrodes 41 and 42 compared to the fixed electrodes 40A and 40B. It is desirable to increase. According to such a configuration, since the compensation electrodes 41 and 42 and the electrostatic shield 237 are not close to each other, even if the communication holes 37c and 37d are not formed in the electrostatic shield 237, the compensation electrodes 41 and 42 and the electrostatic shield 237 are electrostatically charged. Dielectric fluid easily flows between the shield 237 and the shield 237. A columnar member 31 is attached to the inside of the electrostatic shield 237 via a holding member 14 formed of an insulating material such as ceramics or resin.

  As shown in FIG. 12, the compensation electrodes 141 and 142 may have a plurality of branch portions 141a and 142a extending in the circumferential direction of the columnar member 31, respectively. The branch portions 141 a and 142 a are alternately arranged in the longitudinal direction of the columnar member 31. According to such a configuration, it is possible to suppress a difference in dielectric constant between the compensation electrode 141 and the compensation electrode 142. Therefore, the difference between the capacitance C1 (ε) of the compensation capacitor C1 and the capacitance C2 (ε) of the compensation capacitor C2, and the capacitance Cab (ε) of the capacitance C1 (ε) and the composite capacitor Cab. Based on the difference, it is possible to suppress a decrease in accuracy when calculating the displacement x of the spool 22.

  -The columnar member 31 and the cylindrical member 33 should just have a cross-sectional shape corresponding to each other, and a square cross section, a hexagonal cross section, etc. can be employ | adopted besides a circular cross section. In that case, it is necessary to prevent the cylindrical member from rotating in order to keep the electrode interval constant. Further, the cross-sectional shape of the electrostatic shield 37 can be arbitrarily changed.

  In the above embodiment, the entire columnar member 31 is formed of an insulating material, but the columnar member may be formed of a conductive material and the outer surface portion may be covered with the insulating material. Moreover, it replaces with the columnar member 31 and the member formed in the cylinder shape can also be used.

  The fixed electrodes 40A and 40B, the compensation electrodes 41 and 42, the fixed electrode terminals Ta and Tb, and the compensation electrode terminals T1 and T2 are thinned by a pattern formation method other than screen printing, for example, a pattern formation method by etching a deposited film. It can also be formed into a shape.

  In the above embodiment, the fluid chamber 13 is filled with a dielectric fluid such as a chemical solution, but the fluid chamber 13 can be filled with a gas such as air or the fluid chamber 13 can be evacuated.

  In the above embodiment, the displacement sensor 30 is applied to the valve device 10 having the spool valve 20, but the displacement sensor 30 can also be applied to a valve device having another type of valve such as a poppet valve. Further, not only the valve but also the displacement of other measurement objects can be measured by the displacement sensor 30.

  As shown in FIG. 13, the tubular member 33 may be formed with a communication hole 33 c. The communication hole 33c includes a space inside the cylindrical member 33 (that is, a space formed between the columnar member 31 and the cylindrical member 33: the same applies hereinafter) and a space outside the cylindrical member 33 (that is, the cylindrical shape). A space formed between the member 33 and the electrostatic shield 37 (hereinafter the same) is provided so as to communicate with each other. In such a configuration, the fluid and the like are exchanged favorably between the space inside the cylindrical member 33 and the space outside the cylindrical member 33. Therefore, according to such a configuration, occurrence of a measurement error of the displacement of the spool 22 due to a change in the dielectric constant in the space inside the cylindrical member 33 is further suppressed satisfactorily.

  Here, the communication hole 33 c is preferably provided at a position corresponding to the upper end portion in the space inside the tubular member 33. In particular, the bottom 33a is higher than the opening of the cylindrical member 33 (the end on the opposite side to the through hole 33b in the longitudinal direction, that is, the opening provided on the left end in FIG. 13). The central axis of the cylindrical member 33 may be inclined with respect to the horizontal plane. In this case, the communication hole 33c is provided at a position corresponding to the end portion on the through hole 33b side in the longitudinal direction (the end portion on the opposite side to the above-described opening portion) of the space inside the cylindrical member 33. Thereby, generation | occurrence | production of the measurement error by gas (bubble) staying in the space inside the cylindrical member 33 is suppressed favorably.

  -As shown in FIG.14 and FIG.15, fixed electrode 40A, 40B may be formed in the comb-tooth shape. In such a configuration, the change in the capacitance accompanying the displacement of the spool 22 is stepped. Accordingly, the displacement of the spool 22 is measured based on the step-like or pulse-like output signal. Therefore, according to this configuration, the displacement measurement of the spool 22 can be performed more simply. In this case, the thin electrode patterns constituting the comb-like electrodes in the fixed electrodes 40A and 40B may have the same width. Alternatively, a part of the plurality of thin line-shaped electrode patterns may have a width different from that of the other (with such a configuration, the origin detection or the calibration in the displacement measurement of the spool 22 can be performed satisfactorily. Can be broken.)

  As shown in FIGS. 16 to 18, the fixed electrodes 40 </ b> A and 40 </ b> B may be provided so as not to overlap each other in the central axis direction (longitudinal direction) of the columnar member 31. In this case, as shown in FIG. 18, a cylindrical member 133 (see FIG. 9) formed of an insulating material such as ceramics or resin is used. In such a configuration, due to the difference between the capacitance between the electrode 133a formed on the inner surface of the cylindrical member 133 and the fixed electrode 40A and the capacitance between the electrode 133a and the fixed electrode 40B, The displacement of the spool 22 is measured. For this reason, in such a configuration, the compensation electrodes 41 and 42 (see FIG. 1 and the like) can be omitted.

  DESCRIPTION OF SYMBOLS 10 ... Valve apparatus, 11 ... 1st main body, 12 ... 2nd main body, 12a ... Opening part, 13 ... Fluid chamber, 20 ... Spool valve, 22 ... Spool (measurement object), 30 ... Capacitance type displacement sensor, 31 ... Columnar member (bar-shaped member), 31a ... end, 31b ... exposed part, 33 ... cylindrical member (movable electrode), 37 ... electrostatic shield, 37a ... end, 37b ... overhang, 37c ... communication hole, 37d ... Communication hole, 40A ... Fixed electrode, 40B ... Fixed electrode, 41 ... Compensation electrode (first compensation electrode), 42 ... Compensation electrode (second compensation electrode), 51 ... Low melting point glass (insulating material), 52 ... Low Melting point glass (insulating material), 61 ... Capacitance measurement circuit (measurement circuit), 62 ... Switch circuit (switching circuit), 64 ... Microcomputer (calculation unit), 112 ... Second body, 112a ... Opening portion, 133 ... Cylindrical shape Member, 133a ... electrode (movable electrode), 37 ... Electrostatic shield, 137a ... End, 141 ... Compensation electrode (first compensation electrode), 141a ... Branch, 142 ... Compensation electrode (second compensation electrode), 142a ... Branch, 237 ... Electrostatic shield, T1 ... compensation electrode terminal (first compensation electrode terminal), T2 ... compensation electrode terminal (second compensation electrode terminal), Ta ... fixed electrode terminal, Tb ... fixed electrode terminal.

Claims (11)

A rod-shaped member having an outer surface portion formed of an insulating material;
A cylindrical member that is inserted into a predetermined range from one end in the longitudinal direction of the rod-shaped member and moves in the longitudinal direction in accordance with the displacement of the measurement target;
A pair of fixed electrodes formed in a thin film on the outer surface portion of the rod-shaped member and facing each other across the rod-shaped member;
A pair of movable electrodes provided on the cylindrical member in a state insulated from the fixed electrode and the measurement object, and facing the pair of fixed electrodes;
A compensation electrode that is formed in a thin film on the outer surface of the rod-shaped member and does not face the movable electrode;
An electrostatic shield that covers and grounds the fixed electrode, the movable electrode, and the compensation electrode in an insulated state;
A fixed electrode formed in a thin film shape on the outer surface portion of the rod-like member and connected to each of the fixed electrodes and extending in the longitudinal direction while being insulated from the electrostatic shield to the outside of the electrostatic shield A terminal,
A compensation electrode terminal formed in a thin film shape on the outer surface portion of the rod-shaped member, connected to the compensation electrode and extended to the longitudinal direction while being insulated from the electrostatic shield to the outside of the electrostatic shield; ,
A capacitance type displacement sensor comprising:   The electrostatic capacitance type displacement sensor according to claim 1, wherein the electrostatic shield has a protruding portion that protrudes to a position close to the compensation electrode. A fluid chamber for storing a dielectric fluid in contact with the fixed electrode, the movable electrode, the compensation electrode, and the overhang portion includes a sensor body formed therein,
The electrostatic shield has a communication hole that communicates the space between the compensation electrode and the overhanging portion with the space outside the electrostatic shield in the fluid chamber on both sides of the compensation electrode in the longitudinal direction. The capacitance type displacement sensor according to claim 2, wherein:   The capacitive 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 sealed with an insulating material along an outer periphery of the outer surface portion. The electrostatic shield extends along the longitudinal direction and is exposed at the opening of the sensor body,
The capacitive displacement sensor according to claim 4, wherein a gap between the end of the rod-shaped member opposite to the predetermined range in the longitudinal direction and the electrostatic shield is sealed with the insulating material.   The capacitive displacement sensor according to claim 1, wherein the entire rod-shaped member is made of an insulating material.   The capacitive displacement sensor according to claim 1, wherein the entire cylindrical member is formed of a conductive material. The fixed electrode terminal and the compensation electrode terminal extend in the longitudinal direction and are arranged close to each other,
The capacitive displacement sensor according to claim 1, wherein the fixed electrode and the compensation electrode extend in a circumferential direction of the outer surface portion.   The capacitance type displacement according to any one of claims 1 to 8, wherein an exposed portion where the outer surface portion is exposed is provided at an end portion of the rod-shaped member on the predetermined range side in the longitudinal direction. Sensor. The compensation electrode is a first compensation electrode;
The compensation electrode terminal is a first compensation electrode terminal;
A second compensation electrode formed on the outer surface of the rod-like member in a thin film shape larger than the first compensation electrode, and not facing the movable electrode;
A second thin film is formed on the outer surface portion of the rod-shaped member, and is connected to the second compensation electrode and extends to the outside in the longitudinal direction while being insulated from the electrostatic shield to the outside of the electrostatic shield. A compensation electrode terminal;
A measurement circuit for measuring the capacitance between the two electrodes;
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; A switching circuit for switching between a third state in which the fixed electrode terminal connected to each is connected to the measurement circuit;
In the first state, the second state, and the third state, the first capacitance, the second capacitance, and the third capacitance are measured by the measurement circuit, respectively, and the first capacitance And a calculation unit that calculates a displacement of the measurement target based on a difference between the second capacitance and the difference between the first capacitance and the third capacitance;
An electrostatic capacitance type displacement sensor given in any 1 paragraph of Claims 1-9 provided with. The first compensation electrode and the second compensation electrode each have a plurality of branch portions extending in the circumferential direction of the outer surface portion,
The capacitive displacement sensor according to claim 10, wherein the branch portion of the first compensation electrode and the branch portion of the second compensation electrode are alternately arranged in the longitudinal direction.

Images