JP2694360B2 - Capacitive detector - Google Patents

Description

The present invention relates to a structure of a capacitance type detector that converts a mechanical minute displacement amount into an electric signal as a change amount of the electrostatic capacitance.

<Prior Art> Conventionally, the parallel leaf spring mechanism used when handling a minute mechanical displacement has very smooth movement because there is no friction in the moving parts, and there are no various problems caused by friction. Therefore, it is used in detectors such as electric micrometers.

FIG. 7 is a schematic cross-sectional view of a conventional electric micrometer detector including the parallel leaf spring mechanism.

In this detector, a parallel leaf spring composed of two leaf springs arranged in parallel so that the spindle 4 which moves together with the tracing stylus 2 can move in the axial direction on the axial center line of the cylindrical hole 6a of the case 6. Supported by 8,10. The spindle 4 has a ring-shaped core 12 and parallel leaf springs 8 and 10.
It is fitted by means of press fitting, adhesion, screwing, etc. so as to be located between them.

A bobbin 20 including a primary coil 14 and two secondary coils 16 and 18 sandwiching the primary coil 14 is attached to the inner wall of the cylindrical hole 6a.

The bobbin 20 in this detector is wound so as to form a differential transformer by the above three coils, and is arranged so as to face the core 12 with a certain gap.

In this detector, 2
The spindle 4 supported by the parallel leaf springs 8 and 10 linearly moves in the axial direction, and this movement causes the spindle 4 to move from the secondary coils 16 and 18 in the differential transformer including the core 12 and the bobbin 20. A differential output proportional to the displacement is obtained.

The differential output of the secondary coils 16 and 18 thus obtained is
It is transmitted to an indicator (not shown) via a lead wire 22 drawn outside the case, passing the side of the case 6 bypassing the parallel leaf spring, and the displacement amount of the spindle 4 is visualized there by a meter or the like. Is displayed.

<Problems to be Solved by the Invention> Like the detector of the electric micrometer described above, the lead wire 22 is connected only to the bobbin 20 on the fixed side, and the lead wire is attached to the core 12 attached to the spindle 4 as a movable part. If the connection is unnecessary, the parallel leaf spring mechanism can be easily adopted.

However, when a lead wire is also required for the movable part supported by the parallel leaf spring, the lead wire also moves together with this movable part, so it is not possible to bundle and pull it out together with the fixed side lead wire 22. However, if the mounting method is such that frictional resistance is generated even when the lead wire is moved, the moving part is affected, and high-precision detection cannot be performed.

For this reason, it has been considered that the parallel leaf spring mechanism cannot be adopted in the detection system which requires the lead wire in the movable portion.

The present invention provides a more accurate capacitance type detector by adopting the parallel leaf spring mechanism even if the capacitance type detector requires a lead wire also in the movable part. The purpose is to provide.

<Means for Solving the Problems> A capacitive detector according to the present invention comprises a cylindrical case,
A plurality of parallel plate springs, a movable shaft supported by the parallel plate spring so as to move substantially on the axial center line of the case, and a movable electrode attached to the movable shaft via an insulating member,
The movable electrode and the pair of fixed electrodes, which are arranged with a certain gap with respect to the movable electrode and are attached to the case via an insulating member, are attached to the parallel electrode spring on one parallel plate spring. The lead wire that is fixed to each electrode by passing through the slit provided and that is attached to at least the movable electrode among them is connected via a flexible member at the stage before being inserted into the slit of the leaf spring. Is characterized by.

<Operation> The movable shaft in the capacitance type detector of the present invention is supported by the parallel plate spring and is movably supported without frictional resistance.

A lead wire drawn through a slit of a parallel leaf spring is attached to the movable electrode attached to the movable shaft, and a flexible member is interposed in the lead wire before the slit is inserted.

Therefore, when the movable electrode moves together with the movable shaft, the lead wire also moves, but at this time, the flexible member is deformed such as being bent, and the lead wire itself is not bent or bent.

Therefore, the movable shaft can be moved smoothly without causing resistance due to friction or deformation of the lead wire.

The principle of this capacitance type detector is as follows.

A sine voltage having a phase difference of 180 degrees is applied from a transmission circuit to a pair of fixed electrodes from a lead wire.

At this time, when the movable electrode is displaced relative to the fixed electrode, the difference between the capacitance between the movable electrode and one fixed electrode and the capacitance between the movable electrode and the other fixed electrode is reduced. It changes in proportion to the displacement of the movable electrode.

By obtaining this change as an output from the lead wire of the movable electrode, the displacement amount of the movable electrode is converted into an electric signal and detected.

<Examples> Examples of the present invention will be described below with reference to the drawings.

1 is a sectional view of a capacitance type detector according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II of FIG. 1, and FIG. 3 is II-II of FIG. A sectional view taken along the arrow, FIG. 4 is III of FIG.
-III line sectional view, FIG. 5 is a IV-IV line sectional view of FIG. 2, and FIG. 6 is a VV line sectional view of FIG.

24 is a cylindrical case. Cylindrical hole 24 in this case 24
a is open to the left and right in FIG. 1, and one of the openings 24b, 24c is a bottom wall 24e having three eyebrow-shaped holes 24d and the like near one opening 24c as shown in FIG. Is provided.

Further, on the inner peripheral wall of the cylindrical hole 24a near the bottom wall 24e, a ring-shaped protruding portion 24f for positioning a fixed electrode, a parallel leaf spring, etc., which will be described later, is provided.

26 and 28 are two parallel leaf springs. These parallel leaf springs 2
The ends of the cases 6, 28 on the inner peripheral wall side are sandwiched and fixed by spacers 30, 32, 34, 36, which are sequentially fitted into the case.

Among the parallel leaf springs 26, 28, the parallel leaf spring 26 has a plurality of slits 26a, 26 for inserting lead wires described later.
b and 26c are provided as shown in FIG. The slits 26a, 26b, 26c are provided concentrically with the central axis of the case 24 as the center of the parallel leaf spring 26 along three circles having different diameters, and are divided at intervals of 120 degrees.
Also, the slit 26b is divided at 60
The slit 26c is located at the same position as the slit 26a.

In addition, the dividing angle of this slit is set corresponding to the arrangement interval of the lead wire described later.

Further, the parallel leaf spring is provided with a slit in order to obtain elasticity, but the slit of the parallel leaf spring 28 is also a parallel leaf spring.
The same as 26 may be commonly used, or slits having other shapes may be provided.

38 is a movable shaft, and the parallel plate springs 26 and 28 cause the case 24 to move.
Is movably supported almost on the axis center line. That is,
The movable shaft 38 is arranged on the axis center line of the case 24.
The parallel plate springs 26, 28 are clamped by the outer peripheral portion of the movable shaft 38 by ring-shaped spacers 31, 33, 35, 37 which are sequentially fitted on the 38, and the movable shaft 38 is attached to the parallel plate springs 26, 28. .

A coil spring 39 is provided between one end of the movable shaft 38 and the bottom wall 24e of the case 24 to set the initial position of the movable shaft 38.

Further, a tracing stylus 41 is attached to the other end of the movable shaft 38.

40 is a cylindrical movable electrode. The movable electrode 40 is externally fitted to a portion of the movable shaft 38 between the parallel leaf springs 26, 28 via a tubular insulating member 42 externally fitted to the outer periphery of the movable shaft 38,
Further, the spacers 33 and 35 are sandwiched and fixed.

An escape portion 40a for reducing the weight of the movable electrode 40 is provided on the end surface of the movable electrode 40 in the axial direction of the case 24. By thus providing the escape portion 40a and reducing the weight of the movable electrode 40, there is no difference in the detected values due to the change in the attitude of the detector, and the accuracy can be further improved. still,
The escape portion 40a is formed by cutting the end surface of the movable electrode 40 in a ring shape or by forming a hole.

In addition, ring-shaped insulating sheets 43 and 45 are also provided between the movable electrode 40 and the spacers 33 and 35.

44 and 46 are a pair of ring-shaped fixed electrodes, which are cylindrical holes 24a.
It is fitted into the cylindrical hole 24a through a ring-shaped insulating member 48 attached to the inner peripheral wall of the.

Further, a ring-shaped insulating sheet 50 is sandwiched between the fixed electrodes 44, 46, and the pair of fixed electrodes 44, 4
6 is insulated. Further, the inner peripheral surface 44 of the fixed electrodes 44, 46
The a and 46a are arranged so as to face the outer peripheral surface 44b of the movable electrode 40 with a constant gap.

The positions of the fixed electrodes 44 and 46 are the same as those of the spacers 30 to 36 positioned by the protrusion 24f of the case 24.
It is decided by being sandwiched between 32 and 34. In addition, ring-shaped insulating sheets 52 and 54 are also sandwiched between the spacers 32 and 34 and the fixed electrodes 44 and 46.

56, 58 and 60 are movable electrodes 40 and fixed electrodes 46 and 44, respectively.
Is a lead wire connected to.

The lead wires 56, 58, 60 are drawn out from terminals 62, 64, 66 (Fig. 6) mounted on the bottom wall 24e of the case 24 at 120 ° intervals.

The lead wires 58 and 60 are inserted straight from the terminals 64 and 66 into the slits 26a of the parallel leaf spring 26 and soldered to the fixed electrodes 46 and 44, respectively, as shown in FIGS. At this time, the lead wire 58 passes through the inside of the fixed electrode 44 and is connected to the fixed electrode 46. Therefore, the insulating bush 68 as shown in FIG. Is passing through. The fixed electrodes 46,44
The insulating sheets 50, 52 are attached to the insulating sheets 50, 52 so that the lead wires 58, 60 drawn to the side can be easily attached.
Notches 50a, 52a, 52b are provided as shown in the figure.

On the other hand, the lead wire 56 comprises a lead-out portion 56a drawn out from the terminal 62 as shown in FIG. 1 and a connecting portion 56b connected to the movable electrode 40 and soldered as shown in FIG. Before the lead wire 56 is inserted into the slit 26b of the parallel leaf spring 26, that is, in the vicinity of the bottom wall 24e of the case 24, a flexible member 70 is interposed between the lead-out portion 56a and the connecting portion 56b to connect them. There is.

The flexible member 70 is made of a flexible conductive member such as a coil spring, is bent into a U shape as shown in FIGS. 1 and 6, and is placed in the hole 24d of the bottom wall 24e of the case 24. 72 is a moisture-proof film made of an extremely thin and flexible plastic film such as polyethylene or nylon that prevents dust and moisture entering the case from entering between the electrodes. It is provided between the movable shaft 38 and the inner wall of the case 24 and seals the opening 24b of the case 24.

The movable shaft 38 of the moisture-proof film 72 and the vicinity of the inner wall of the case 24 are sandwiched by ring-shaped packings 74, 76 and 78, 80, respectively.

The packings 74, 76, 78, 80 in this embodiment are made of a Teflon sheet, and are actually between the spacer 36 and the case nut 82 fitted in the opening 24b of the case 24 and between the spacer 37 and the movable shaft. The moisture-proof film 72 is elastically sandwiched by being pressed against the spacer 84 fitted on the outside of the 38.

The moisture-proof film 72 is stretched slightly so as to follow the operation of the movable shaft 38 without applying a mechanical load.

Further, by fitting the nut 86 to the movable shaft 38,
All packings, spacers, etc. between the nut 86 and the large diameter portion 38a at one end of the movable shaft 38 are sandwiched and fixed between them. Also, when the case nut 82 is attached to the case 24, the case nut 82 and the protrusion 24 of the case 24
All packings, spacers, etc. between them and f are clamped and fixed.

When installing the case nut 82, the spacer 36
In order to prevent the parallel leaf spring 28 from twisting due to the rotation of the screw, a groove 36a is provided in a part of the outer periphery of the space 36 as shown in FIG. 1, and a screw 88 penetrating the case 24 is projected here. This prevents the spacer 36 from rotating.

Reference numeral 90 denotes an upper lid that constitutes a lid together with the case nut 82, and is fixed to the case nut 82 by several screws 92.

By attaching the upper lid 90 to the case nut 82, the opening 24b of the case 24 is sealed. This upper lid 90 is provided with at least one vent hole 90a, and when the movable shaft 38 is moved, the space between the moisture-proof film 72 and the upper lid 90 becomes a negative pressure than atmospheric pressure, so that the movable shaft 38 operates. This space communicates with the atmosphere so as not to interfere.

Reference numeral 94 is a lower lid attached to the bottom wall 24e of the case 24 with screws 96.

Next, the operation of the characteristic part of the capacitance type detector in this embodiment will be described.

When axial displacement is applied to the tracing stylus 41 of the detector configured as described above, the parallel leaf springs 26, 28 are displaced by the given displacement amount.
The movable shaft 38 supported by the shaft is displaced in the axial direction.

At this time, the lead wire 56 attached to the movable electrode 40
Although b is also displaced in the axial direction together with the movable electrode 40, the lead wire 56b itself does not deform or bend, and the lead wire 5b
The flexible member 70 connected to 6b is deformed.

That is, in FIG. 1, when the movable electrode 40 is displaced rightward in the figure together with the movable shaft 38, the connecting portion 56b of the lead wire 56 is displaced rightward in the figure accordingly.

This displacement is transmitted to the flexible member 70, and the flexible member 70 bends and bulges in the right direction in the drawing. At this time, since the lead-out portion 56a of the lead wire 56 is in a fixed state, the flexible member 70 is deformed to form a substantially J-shape, and the connecting portion 56b of the lead wire 56 is displaced. Absorb.

After that, when the detection is completed, the movable shaft 38 is returned to the initial position by the coil spring 39, and the movable electrode 40 at this time is returned.
The connecting portion 56b of the lead wire 56 also moves to the left in the figure in accordance with the movement of, and the flexible member 70 returns to the initial state.

<Advantages of the Invention> According to the present invention, the lead wire is configured to pass through the slits of the parallel leaf springs, and the flexible member is interposed between the lead wires. The parallel plate spring mechanism can also be adopted in the electrostatic capacitance type detector described above, and more highly accurate detection can be performed.

Further, since it is not necessary to dispose the lead wire in the side wall of the case or the like, the case can be downsized.

[Brief description of the drawings]

1 is a sectional view of a capacitance type detector according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II of FIG. 1, and FIG. 3 is II-II of FIG. 4 is a sectional view taken along the line III-III in FIG. 2, FIG. 5 is a sectional view taken along the line IV-IV in FIG. 2, and FIG. FIG. 7 is a schematic cross-sectional view taken along the line V, and FIG. 7 is a schematic cross-sectional view of a conventional electric micrometer detector. 24 …… Case, 24a …… Cylindric hole, 26,28 …… Parallel leaf spring, 38 …… Movable shaft, 40 …… Movable electrode, 42,48 …… Insulation member, 44,46 …… Fixed electrode, 56, 58,60 …… Lead wire, 70 …… Flexible member, 72 …… Moisture-proof film, 74,76,78,80 …… Packing 82 …… Case nut, 90 …… Top lid.

Claims (6)

(57) [Claims] 1. A cylindrical case, two parallel leaf springs mounted in the case, a movable shaft supported by the parallel leaf spring so as to be movable substantially on the axial center line of the case, A cylindrical movable electrode attached to the movable shaft via an insulating member between parallel leaf springs, and an insulating member on the case side between the leaf springs with a constant gap with the outer peripheral surface of the movable electrode. And a pair of ring-shaped fixed electrodes attached to the movable electrode and the lead wires attached to the pair of fixed electrodes are inserted into the slits provided in the one parallel leaf spring to reach each electrode. Each of the lead wires, which is fixed and is attached to at least the movable electrode, is connected via a flexible member before being inserted into the slit of the leaf spring. Capacitive detector. 2. The capacitance type detector according to claim 1, wherein the movable electrode has an escape portion for weight reduction on an end face in the axial direction. 3. The capacitance type detection device according to claim 1, wherein the opening of the case is sealed by providing a moisture-proof film between the movable shaft and the inner wall of the case. vessel. 4. A capacitance type detector according to claim 3, wherein a lid is fitted in the opening of the case, and a ventilation hole is provided in the lid. 5. The capacitance type detector according to claim 3, wherein the moisture-proof film is sandwiched by packing near the movable shaft and the inner peripheral wall of the case. 6. The static spring according to claim 1, wherein the slit of the leaf spring is provided along a circle concentric with the center of the leaf spring and is divided at a predetermined angle. Capacitive detector.