JP2015102535A - Capacitive angle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitive angle sensor which is small-sized to be applicable for angle detection of an electrically driven valve actuator and is less influenced by individual difference and temperature.SOLUTION: A fixed electrode 10 having, as a main body, a base 11 formed of an insulator having a small linear expansion coefficient such as ceramics and a movable shielding plate 20 made of a conductor are combined. The fixed electrode 10 includes a base surface 11-0 orthogonal to an axial direction, cylindrical walls 11-1 to 11-5 which are formed like concentric circles in the axial direction with the base surface 11-0 as a base and are different in diameters, and a slit 11-6 dividing the cylindrical walls 11-1 to 11-5 into two in a radial direction. Electrodes 12 are formed on respective opposite surfaces of the cylindrical walls 11-1 to 11-5. The fixed electrode 10 and the movable shielding plate 20 are combined in such a state that the movable shielding plate 20 has semicylindrical walls 20-1 to 20-4 like comb teeth inserted to gaps between opposite surfaces of the cylindrical walls 11-1 to 11-5 of the fixed electrode 10, and they are rotated in accordance with the change in angle of a detection object.

Description

  The present invention relates to a capacitance type angle sensor that detects an angle of a detection target based on an amount of change in capacitance.

  Conventionally, for example, a potentiometer has been used to detect the rotation angle of an electric valve actuator. The structure of a general potentiometer consists of resistors, shafts, electrodes and cases and covers that wrap them, and is simple and inexpensive, and has no electronic circuit inside, so it is resistant to noise. There are features. However, the potentiometer has a defect that the resistor and the electrode are always in contact with each other and sliding, and whisker-like noise is generated due to deterioration over time.

  Therefore, the applicant of the present application considers using a capacitive angle sensor to detect the rotation angle of the electric valve actuator. Since the capacitance type angle sensor detects the angle of the detection target based on the amount of change in capacitance, there is an advantage that the detection unit becomes non-contact and mechanical aging of the detection unit hardly occurs.

  The theoretical formula of capacitance is given by Q = εS / d, where ε is the dielectric constant, d is the gap, and S is the electrode area (see FIG. 9). Specific examples of the capacitance type angle sensor include “AC servo motor control system angle sensor” as shown in Patent Document 1, and “Non-contact electrostatic sensor” as shown in Patent Document 2. There is a “capacitive sensor”.

JP2012-58106A JP-A-7-91607

  However, when a capacitance type angle sensor is used to detect the rotation angle of the electric valve actuator, the current detection circuit requires a capacitance of several pF order or more, and is considered as a pair of electrodes. And, as in “Angle sensor for AC servo motor control system” disclosed in Patent Document 1, the area of the detection unit needs to be about the total length of the electric valve actuator × the total width. Difficult.

  As a method of integrating the structure and increasing the capacitance, in the “contactless capacitance sensor” disclosed in Patent Document 2, a plurality of electrodes are stacked with a spacer until the required capacitance is reached. It is integrated. However, in the case of this structure, tolerances such as the thickness of the electrode itself, warpage, spacer thickness, etc. are accumulated, affecting the gap in the theoretical formula, causing individual differences, and the difference in the linear expansion coefficient of each material Therefore, in the case of a device having a wide application temperature range such as an electric valve actuator, there is a problem that the electrode and the spacer may further expand and contract depending on the temperature, which may affect the output.

  The present invention has been made to solve such a problem, and the object of the present invention is to provide a small capacitance that can be applied to angle detection of an electric valve actuator and that is less influenced by individual differences and temperature. It is to provide a mold angle sensor.

  In order to achieve such an object, the present invention provides a base surface orthogonal to the axial direction, and a plurality of cylindrical walls having different diameters, which are integrally formed concentrically in the axial direction on the basis of the base surface. And a base made of an insulator having a plurality of cylindrical walls and a slit that divides the cylindrical wall into two in the radial direction, and covers almost the entire surfaces of the opposing surfaces of the plurality of cylindrical walls. A fixed electrode provided with a conductor, a base surface orthogonal to the axial direction, and a plurality of semi-cylindrical walls having different diameters, which are integrally formed concentrically in the axial direction based on the base surface. And a conductor that rotates in response to a change in the angle of the detection target in a state where the plurality of semi-cylindrical walls are inserted in a comb-like shape into the gaps between the opposing surfaces of the plurality of cylindrical walls of the fixed electrode. And a movable shielding plate.

  In the present invention, the movable shielding plate is the object to be detected in a state where the plurality of semicylindrical walls of the movable shielding plate are inserted in a comb-like shape into the gaps between the opposing surfaces of the plurality of cylindrical walls of the fixed electrode. Rotates according to angle change. Here, when one of a plurality of cylindrical walls divided into two in the radial direction of the fixed electrode is a first plurality of semi-cylindrical walls and the other is a second plurality of semi-cylindrical walls, it is movable. Since the surface areas of the electrodes on the opposing surfaces of the first and second plurality of semi-cylindrical walls of the fixed electrode shielded by the shielding plate change, each of the opposing surfaces of the first plurality of semi-cylindrical walls is changed. The capacitance between the conductors on the surface and the capacitance between the conductors on each of the opposing surfaces of the second plurality of semi-cylindrical walls change. Therefore, the capacitance between the conductors on the opposing surfaces of the first plurality of semicylindrical walls and the capacitance between the conductors on the opposing surfaces of the second plurality of semicylindrical walls are changed. Thus, the angle of the detection target can be detected.

  In the present invention, the fixed electrode includes a base surface orthogonal to the axial direction, a plurality of cylindrical walls having different diameters, which are integrally formed concentrically in the axial direction on the basis of the base surface, A base made of an insulator having a slit that divides a cylindrical wall into two in the radial direction, and a conductor formed so as to cover almost the entire surfaces of the opposing surfaces of the plurality of cylindrical walls. ing. By adopting such an electrode structure, the necessary gap is maintained, the electrode area is integrated, as if d (gap) in the theoretical formula of capacitance is kept constant, and S (electrode area) is increased. It is possible to reduce the size. In addition, the accumulation of tolerances related to the gap can be reduced, and the influence of individual differences and temperature can be reduced.

  In the present invention, the capacitance between the conductors on each face of the first plurality of semi-cylindrical walls and the capacitance between the conductors on each face of the second plurality of semi-cylindrical walls are determined. Although it is possible to detect the angle of the detection target, it is not always necessary to use both capacitances. That is, the angle of the object to be detected may be detected from the capacitance between the conductors on the opposing surfaces of the first plurality of semi-cylindrical walls. The angle of the detection target may be detected from the capacitance between the conductors on each surface.

  In the present invention, the capacitance between the conductors on the opposing surfaces of the first plurality of semi-cylindrical walls and the capacitance between the conductors on the opposing surfaces of the second plurality of semi-cylindrical walls When the angle of the detection target is detected using both, for example, the total value of the capacitance between the conductors of the opposing surfaces of the first plurality of semi-cylindrical walls is the first total capacitance value. And the total value of the capacitance between the conductors of each of the opposing surfaces of the second plurality of semi-cylindrical walls is the second total capacitance value, and the first total capacitance value and the second The angle of the detection target is detected based on the difference from the total capacitance value.

  According to the present invention, a base surface orthogonal to the axial direction, a plurality of cylindrical walls having different diameters, which are integrally formed concentrically in the axial direction with the base surface as a base, and the plurality of cylindrical shapes A fixed electrode comprising a base made of an insulator having a slit that divides the wall of the wall into two in the radial direction, and a conductor formed so as to cover almost the entire surfaces of the opposing surfaces of the plurality of cylindrical walls. And a base plate perpendicular to the axial direction and a plurality of semi-cylindrical walls with different diameters, which are integrally formed concentrically in the axial direction with the base surface as a base, and a movable shielding plate made of a conductor In accordance with the change in the angle of the detection target with the plurality of semi-cylindrical walls of the movable shielding plate inserted in a comb-like shape in the gap between the opposing surfaces of the plurality of cylindrical walls of the fixed electrode Since it is rotated, the necessary gap is maintained, the electrode area is integrated, Moreover, d (gap) in the theoretical formula of capacitance is kept constant, and S (electrode area) can be made large so as to reduce the size, and the electric motor that requires capacitance of several pF order or more. It becomes possible to apply to the angle detection of a valve actuator. In addition, the accumulation of tolerances related to the gap can be reduced, and the influence of individual differences and temperature can be reduced.

It is an external appearance perspective view which shows the principal part of one Embodiment of the capacitive type angle sensor which concerns on this invention. The figure which shows the fixed electrode combined with the printed circuit board in this electrostatic capacitance type angle sensor (FIG. 2 (a): Top view, FIG.2 (b): AA sectional view taken on the line in FIG. 2 (a), FIG. 2 (c): a cross-sectional view taken along line BB in FIG. 2 (a). It is sectional drawing which looked at the fixed electrode in FIG.2 (c) from diagonally upward direction. FIG. 4A is a bottom view, FIG. 4B is a view of FIG. 4A viewed from the A direction, and FIG. 4C is a diagram showing a movable shielding plate in this capacitance type angle sensor. 4 (a) is a view from the B direction). It is the figure which looked at the movable shielding board in Fig.4 (a) from diagonally right direction. It is a figure (Drawing 6 (a): a top view, Drawing 6 (b): CC sectional view) showing the state where a movable shielding board was combined with a fixed electrode. It is a circuit diagram of this capacitance type angle sensor. It is a figure which shows the relationship between the rotation angle of a movable shielding board, and electrostatic capacitance QR, QL, and QR-QL. It is a figure which shows the dielectric constant (epsilon), the gap d, and the electrode area S which are used for the theoretical formula of an electrostatic capacitance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an external perspective view showing a main part of an embodiment of a capacitance type angle sensor according to the present invention. In the figure, 10 is a fixed electrode, 20 is a movable shielding plate, 30 is a printed circuit board, and 40 is an angle detection unit, and shows a state before the movable shielding plate 20 is combined with the fixed electrode 10.

  The fixed electrode 10 mainly includes a base 11 formed of an insulator having a small linear expansion coefficient such as ceramics, and the base 11 is a base surface 11-0 orthogonal to the axial direction (the direction indicated by the alternate long and short dash line in FIG. 1). And cylindrical walls 11-1 to 11-5 having different diameters, which are integrally formed concentrically in the axial direction with the base surface 11-0 as a base, and the cylindrical walls 11-1 to 11-11 And a slit 11-6 that divides -5 into two in the radial direction (divided into two equal parts).

  The slit 11-6 is an axial direction of the cylindrical walls 11-1 to 11-5 as a straight line connecting the 0 ° position and the 180 ° position in the radial direction of the cylindrical walls 11-1 to 11-5. The base surface 11-0 of the base 11 is provided with a predetermined width. Moreover, in this Embodiment, the space | interval of each surface which cylindrical walls 11-1 to 11-5 oppose is made all equal.

  In the fixed electrode 10, the opposing surfaces of the cylindrical walls 11-1 to 11-5 of the base 11 are plated with a conductor such as copper so as to cover the entire surface. Is formed as an electrode plate 12. Then, the fixed electrode 10 mainly composed of the base 11 is placed on the printed circuit board 30, and the electrode plate 12 and the printed circuit board formed on the opposing surfaces of the cylindrical walls 11-1 to 11-5. Connection with the circuit pattern formed in the circuit 30 is intended.

  2A is a plan view of the fixed electrode 10 combined with the printed circuit board 20, FIG. 2B is a sectional view taken along the line AA in FIG. 2A, and FIG. A sectional view taken along line BB in (a) is shown, and FIG. 3 shows a view of the fixed electrode 10 in FIG.

  The electrode plate 12 formed on each of the opposing surfaces of the cylindrical walls 11-1 to 11-5 of the base 11 has a cylindrical shape that is divided into two in the radial direction (divided into two equal parts) by the slit 11-6. One of the walls 11-1 to 11-5 is a first semi-cylindrical wall 11-1R to 11-5R, and the other is a second semi-cylindrical wall 11-1L to 11-5L. Conductor pins 13 that are electrically connected to the electrode plates 12 formed on the walls 11-1R to 11-5R and 11-1L to 11-5L are joined, and the conductor pins 13 are connected to the printed circuit. The fixed electrode 10 and the printed circuit board 30 are combined by being inserted into through holes formed in the board 30 and soldered on the back side of the printed circuit board 30.

  On the other hand, the movable shielding plate 20 is made of a conductor such as carbon steel, and has a base surface 20-0 orthogonal to the axial direction (the direction indicated by the one-dot chain line in FIG. 1) and the base surface 20-0 as a base. It has semi-cylindrical walls 20-1 to 20-4 with different diameters, which are integrally formed concentrically in the axial direction. In addition, a rotating shaft 20-5 that extends in the same direction as the semi-cylindrical walls 20-1 to 20-4 is integrally formed at the center of the base surface 20-0 of the movable shielding plate 20.

  4A is a view (bottom view) of the movable shield 20 viewed from the lower side in FIG. 1, and FIG. 4B is a view of the movable shield 20 in FIG. 4A viewed from the A direction. 4 (c) shows a view of the movable shield 20 in FIG. 4 (a) viewed from the B direction, and FIG. 5 shows a view of the movable shield plate 20 in FIG. 4 (a) seen from the oblique right direction.

  As shown in FIG. 6, the movable shielding plate 20 is formed by combing semicylindrical walls 20-1 to 20-4 in the gaps between the opposing surfaces of the cylindrical walls 11-1 to 11-5 of the fixed electrode 10. It is combined with the fixed electrode 10 in a state of being inserted into a tooth shape. In this case, the rotating shaft 20-5 of the movable shielding plate 20 protrudes toward the back side of the printed circuit board 30 through the hollow portion 11 a surrounded by the central cylindrical wall 11-1 of the fixed electrode 10. 6A is a plan view of a state in which the movable shielding plate 20 is combined with the fixed electrode 10, and FIG. 6B is a cross-sectional view taken along the line CC in FIG. 6A.

  Although FIG. 1 shows a state before the movable shielding plate 20 is combined with the fixed electrode 10, the capacitive angle sensor 100 of the present embodiment has the movable shielding plate 20 as shown in FIG. 6. Used in combination with the fixed electrode 10.

  In this capacitive angle sensor 100, the movable shielding plate 20 rotates according to a change in the angle of the detection target around the rotation axis 20-5. That is, the movable shielding is performed with the semi-cylindrical walls 20-1 to 20-4 inserted in a comb-like shape in the gaps between the opposing surfaces of the cylindrical walls 11-1 to 11-5 of the fixed electrode 10. The plate 20 rotates around the rotation axis 20-5 according to the change in angle of the detection target.

FIG. 7 shows a schematic circuit diagram of the capacitance type angle sensor 100. In the capacitance type angle sensor 100, a capacitance Q1 _R is generated between the electrode plates 12 of the fixed electrode 10 facing the semicylindrical walls 11-1R and 11-2R, and the semicylindrical wall 11-2R. And an electrostatic capacity Q2 _R is generated between the opposing electrode plates 12 of 11-3R, and an electrostatic capacity Q3 _R is generated between the opposing electrode plates 12 of the semicylindrical walls 11-3R and 11-4R. A capacitance Q4 _R is generated between the opposing electrode plates 12 of the walls 11-4R and 11-5R.

Further, an electrostatic capacitance Q1 _L is generated between the electrode plates 12 facing the semicylindrical walls 11-1L and 11-2L of the fixed electrode 10, and the electrodes facing the semicylindrical walls 11-2L and 11-3L are opposed to each other. An electrostatic capacity Q2 _L is generated between the plates 12, and an electrostatic capacity Q3 _L is generated between the opposing electrode plates 12 of the semicylindrical walls 11-3L and 11-4L, and the semicylindrical walls 11-4L and 11 are formed. A capacitance Q4 _L is generated between the electrode plates 12 facing -5L.

A wiring pattern is formed on the printed circuit board 30 so that the same poles of the capacitances Q1 _{R to} Q4 _R are connected to each other, and so that the same poles of the capacitances Q1 _{L to} Q4 _L are connected to each other. Thereby, the electrostatic capacitances Q1 _{R to} Q4 _R are connected in parallel, and the total value of the electrostatic capacitances is taken out between the terminals T1 and T2 as QR (QR = Q1 _R + Q2 _R + Q3 _R + Q4 _R ). Capacitances Q1 _{L to} Q4 _L are connected in parallel, and a total value of the capacitances is taken out between terminals T3 and T4 as QL (QL = Q1 _L + Q2 _L + Q3 _L + Q4 _L ).

  The printed circuit board 30 and the angle detection unit 40 are electrically connected, and the capacitances QR and QL taken out from the printed circuit board 30 are sent to the angle detection unit 40 as detection signals.

  FIG. 8 shows the relationship between the rotation angle of the movable shielding plate 20 and the capacitances QR, QL and QR-QL. When the rotation angle of the movable shielding plate 20 changes, the opposing surfaces of the semicylindrical walls 11-1R to 11-5R and 11-1L to 11-5L of the fixed electrode 10 shielded by the movable shielding plate 20 are changed. The surface area of the electrode 12 changes, and the capacitances QR and QL taken out from the printed circuit board 30 change. In this case, when the electrostatic capacity QR decreases, the electrostatic capacity QL increases conversely. When the electrostatic capacity QR increases, the electrostatic capacity QL decreases conversely. The angle detection unit 40 obtains a difference (QR−QL) between the electrostatic capacitances QR and QL from the relationship between the electrostatic capacitances QR and QL and the rotation angle of the movable shielding plate 20, whereby the movable shielding plate 20. An output proportional to the rotation angle, that is, an output proportional to the angle of the detection target is obtained.

  In the capacitance type angle sensor 100, the fixed electrode 10 is mainly composed of a base 11 formed of an insulator having a small linear expansion coefficient such as ceramic, and the base 11 has cylindrical walls 11-1 to 11-1 having different diameters. 11-5 is formed concentrically, electrodes 12 are formed on the opposing surfaces of the cylindrical walls 11-1 to 11-5, and the cylindrical walls 11-1 to 11-5 are slit 11 The electrode structure is divided into two by −6.

  By adopting such an electrode structure, in the capacitive angle sensor 100 of the present embodiment, the necessary gap is maintained, the electrode area is integrated, and d (gap) in the theoretical equation of capacitance is constant. Therefore, S (electrode area) is increased to reduce the size and enable mounting on an electric valve actuator that requires a capacitance of the order of several pF or more.

  The capacitive angle sensor 100 according to the present embodiment is not limited to the electric valve actuator, and can be widely used in an apparatus having a relatively wide application temperature range and no space. In addition, since the structure of the angle detection unit is simple, it is advantageous in terms of cost, and since the accumulation of tolerances regarding the gap is small, the influence of individual differences and temperature is small, and the robustness is improved as compared with the prior art.

  In the above-described embodiment, the angle detection unit 40 obtains an output proportional to the angle of the detection target from the difference (QR−QL) between the capacitances QR and QL. And QL may not be used, and an output proportional to the angle of the detection target may be obtained only from the capacitance QR, and conversely, an output proportional to the angle of the detection target may be obtained from only the capacitance QL. You may make it obtain. When either one of the electrostatic capacitances QR and QL is used, the position at which the cylindrical walls 11-1 to 11-5 are divided into two in the radial direction does not necessarily have to be divided into two equal parts.

  In the above-described embodiment, the opposing surfaces of the cylindrical walls 11-1 to 11-5 are plated with a conductor such as copper to form the electrode plate 12. However, the electrode plate 12 is limited to plating. Not a thing. In the above-described embodiment, the printed circuit board 30 and the angle detection unit 40 are separated from each other. However, the angle detection unit 40 may be provided on the printed circuit board 30.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Fixed electrode, 11 ... Base, 11-0 ... Base surface (base), 11-1 to 11-5 ... Cylindrical wall, 11-6 ... Slit, 11-1R to 11-5R, 11-1L -11-5L2 ... Semi-cylindrical wall, 11a ... Hollow part, 12 ... Electrode, 13 ... Conductor pin, 20 ... Movable shielding plate, 20-0 ... Base surface (base), 20-1 to 20-4 DESCRIPTION OF SYMBOLS ... Semi-cylindrical wall, 20-5 ... rotating shaft, 30 ... printed circuit board, 40 ... angle detection part, 100 ... capacitance-type angle sensor.

Claims (3)

A base surface orthogonal to the axial direction, a plurality of cylindrical walls with different diameters formed concentrically in the axial direction on the basis of the base surface, and the plurality of cylindrical walls in the radial direction A fixed electrode comprising: a base made of an insulator having a slit divided into two; and a conductor formed so as to cover almost the entire surface of each of the opposing surfaces of the plurality of cylindrical walls;
A plurality of semi-cylindrical walls, each having a base surface orthogonal to the axial direction, and a plurality of semi-cylindrical walls having different diameters, which are integrally formed concentrically in the axial direction based on the base surface. A movable shielding plate made of a conductor that rotates in response to a change in the angle of a detection target in a state where the wall of the fixed electrode is inserted in a gap between opposing surfaces of the plurality of cylindrical walls of the fixed electrode in a comb shape. A capacitance-type angle sensor comprising: The capacitive angle sensor according to claim 1,
One of the plurality of cylindrical walls divided into two in the radial direction of the fixed electrode is a first plurality of semi-cylindrical walls, and the other is a second plurality of semi-cylindrical walls. Based on at least one of the capacitance between the conductors on each face of the plurality of semi-cylindrical walls and the capacitance between the conductors on each face of the second plurality of semi-cylindrical walls. An electrostatic capacity type angle sensor comprising: an angle detection unit that detects an angle of the detection target. The capacitance type angle sensor according to claim 2,
The angle detector
The total value of the capacitance between the conductors of each of the opposing surfaces of the first plurality of semi-cylindrical walls is defined as a first total capacitance value, and the second plurality of semi-cylindrical walls are opposed to each other. The total value of the capacitance between the conductors on each surface to be used is a second total capacitance value, and the detection target is based on the difference between the first total capacitance value and the second total capacitance value. Capacitance type angle sensor characterized by detecting the angle.

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