JP2002090177A - Displacement detection device without contact-making - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure easily an inductance value and a resistant value required for a coil with a simple formation. SOLUTION: In this displacement detection device without contact-making equipped with coils 21a, 21b, a shaft 26, and a metal body 27 mounted on the shaft 26, whose area facing to the coils 21a, 21b is changed by rotation of the shaft 26, capable of taking out the change of inductance of the coils 21a, 21b caused by the change of the facing area as an electric signal, the coils 21a, 21b are arranged on the cylindrical surface having the same axial center as the shaft 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contactless displacement detecting device utilizing a change in coil inductance due to an eddy current effect.

[0002]

2. Description of the Related Art A metal body comprising a coil, a shaft, and a highly conductive metal body mounted on the shaft and configured to rotate with the rotation of the shaft to change the area facing the coil. Various types of displacement detection devices have been proposed in the prior art that are capable of detecting a rotational displacement of a shaft by extracting, as an electric signal, a change in inductance of a coil caused by a change in an area facing the coil.

FIG. 9 schematically shows a conventional configuration example of this type of displacement detection device. In this example, the shaft 11 is inserted into a hole (hidden and invisible in the drawing) provided in the printed circuit board 12, and the printed circuit board 1 is perpendicular to the shaft 11.
A pair of coils 13a and 13b are pattern-formed on the second plate surface. Each of the coils 13a and 13b has a shaft 11
Are formed in a substantially semicircular arc region centered at. The shaft 11 is provided with a metal plate 14 having a semi-circular fan shape and good conductivity, which is mounted on the shaft 11.
And the plate surface of the printed circuit board 12 with a predetermined minute gap,
That is, they are opposed to the coils 13a and 13b. Although not shown in the drawing, the shaft 11 is connected to another rotating device for detecting, for example, the amount of rotational displacement.

When a high frequency is applied to the coils 13a and 13b, an eddy current is generated in the metal body 14, and in that state, the shaft 1
When 1 rotates, the area of the metal body 14 facing the coils 13a and 13b changes, whereby the eddy current value changes and the inductance of the coils 13a and 13b changes.
This change is taken out as an electric signal. Therefore, a rectifier circuit / amplifier circuit is connected to the coils 13a and 13b as a detection system, and an oscillation circuit for applying a high frequency is connected. Although components constituting these circuits are omitted in the drawing, they are mounted on the printed circuit board 12.

[0005]

As described above, in a displacement detecting device for extracting a change in inductance of a coil as an electric signal, a required inductance value and resistance value are ensured for the coil in order to obtain required electric performance. It is necessary. In the case of the conventional displacement detecting device shown in FIG. 9, the coils 13a and 13b formed by patterning on the printed circuit board 12 have a spiral shape, and the inductance value when the coil is wound in a spiral shape as described above. As shown in FIG. 10, L is represented by the following equation, where di is the diameter of the opening of the coil 13, do is the outermost diameter, and n is the number of turns.

L = 39.4a ² n ² / (8a + 11c) [nH] a = (do + di) / 4 c = (do−di) / 2 However, in the conventional displacement detecting device, as shown in FIG. Printed circuit board 1 on which coils 13a and 13b are formed
2 is passed through the shaft 11, that is, the coil 13
Since the opening portions (opening surfaces) a and 13b are formed to be perpendicular to the shaft 11, the diameter of the shaft 11 is large as shown in FIG.
When the difference between the diameter of the printed circuit board 12 and the outer shape of the printed circuit board 12 is small, the coil 13 formed on the printed circuit board 12
Since the areas of a and 13b are reduced and di in the above equation cannot be increased, a situation has arisen in which a sufficient inductance value L cannot be obtained.

In addition, since the frequency of the oscillation circuit increases as the inductance value of the coil decreases, the components used in the oscillation circuit and the rectifier circuit must be special components that can handle such frequencies. In this respect, the coil arrangement structure in the conventional displacement detection device has a problem in that it causes restrictions in design and an increase in cost. As means for increasing the inductance value of the coil, it is possible to increase the inductance value of the coil by increasing the number of turns n of the coil, for example, by multiplying the printed circuit board by the above equation.
Increasing the number of turns of the coil increases the resistance value of the coil, which causes a problem of deteriorating the temperature characteristics.

On the other hand, in FIG. 11, for example, the outer shape of the printed circuit board 12 is made sufficiently larger than the diameter of the shaft 11,
If the area in which the coils 13a and 13b are formed can be increased, the inductance value can be increased, but the outer shape of the device becomes large, which hinders miniaturization. In view of these problems, the object of the present invention is to make it possible to easily secure required inductance and resistance values of a coil, and to make the coil compact even if the shaft has a large diameter. An object of the present invention is to provide a displacement detection device.

[0009]

According to the first aspect of the present invention, there is provided a coil, a shaft, and a metal body which is integrated with the shaft and whose area facing the coil changes by rotation of the shaft, In the non-contact type displacement detecting device configured to extract a change in inductance of the coil due to a change in the facing area as an electric signal, the coil is arranged on a cylindrical surface coaxial with the shaft.

According to a second aspect of the present invention, in the first aspect, the shaft and the metal body are integrally formed. According to a third aspect of the present invention, in the first aspect, the metal body is a metal film provided on a peripheral surface of a resin flange integrated with the shaft. According to a fourth aspect of the present invention, in the third aspect, the shaft and the flange are integrally formed.

According to a fifth aspect of the present invention, in the first aspect, the shaft is made of a resin, and the metal body is a metal film provided on a peripheral surface of the shaft. According to a sixth aspect of the present invention, in any one of the third to fifth aspects, the metal film is an electroless plating film. In the invention of claim 7, claims 3 to 5
In any one of the inventions, the metal film is a metal foil and is attached to the peripheral surface.

According to the eighth aspect of the present invention, there is provided a metal shaft and a coil disposed on a cylindrical surface coaxial with the shaft, and a notch is provided in a portion of the shaft facing the coil, The opposed area between the coil and the circumferential surface of the shaft is changed by the rotation of the shaft, and the change in the inductance of the coil due to the change is taken out as an electric signal.

[0013]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is an exploded view of a main part thereof. First, the configuration of the main part will be described with reference to FIG. In this example, the coils 21a, 21
1b is formed by a flexible printed wiring board (FPC) 22, and the FPC 22 is adhered and fixed to the inner peripheral surface of a cylindrical housing 23 with an adhesive or the like.

The FPC 22 is formed in a strip shape, the length of which is substantially the entire circumference of the housing 23, and the coils 21a and 21b are formed in each half in a spiral pattern. A terminal portion 24 protrudes from the center of the side edge of the FPC 22, and the terminal portion 2
4, a coil terminal 25 is led out. Housing 23
Is made of, for example, a resin which does not cause an eddy current effect. A metal body 27 having good conductivity is attached to the shaft 26. The metal body 27 has a semicircular fan shape as shown in the figure, and has a predetermined length (thickness) in the axial direction of the shaft 26 so that its circumferential surface can sufficiently oppose the coils 21a and 21b. ). The shaft 26
Has an E-ring mounting groove 28 formed therein.

The circuit board 29 has a circular shape and has various circuit components mounted thereon. Further, a hole 31 through which the shaft 26 is inserted is formed at the center. Next, the structure of the contactless displacement detection device 32 incorporating these components will be described with reference to FIG. Cylindrical case 3
3 has a closed end formed with a bearing portion 34 protruding from the one end surface thereof, and a lid 35 is screwed on the open other end surface to be closed. The case 33 is made of metal in this example.

A circuit board 29 is arranged in an internal space defined by the case 33 and the lid 35 as shown in FIG.
A housing 23 to which the FPC 22 is fixed is disposed thereon. The circuit board 29 and the housing 23 are arranged such that the outer peripheral surfaces thereof are substantially in contact with the inner peripheral surface of the case 33, and are positioned and fixed between one end surface of the case 33 and the inner end of the lid 35. The inner end of the shaft 26 has the lid 3
5 is supported by a bearing portion 36 formed on the inner surface of the case 5, and is further supported by a bearing portion 34 of the case 33 via a bearing 37. In the figure, reference numeral 38 denotes an E-ring.

The metal body 27 attached to and integrated with the shaft 26 has a circumferential surface of the coil 21a, 21b.
And a predetermined gap therebetween. Coils 21a, 21
“b” is connected to a circuit arranged on the circuit board 29 via the coil terminal 25. FIG. 3 shows this displacement detecting device 3.
2 shows an example of a circuit configuration, in which an oscillator circuit 41, a rectifier circuit 42, and an amplifier circuit 43 are arranged on a circuit board 29, and these circuits are connected to the coils 21a and 21b.

The displacement detecting device 3 having the above structure
2, the coils 21a and 21b are arranged on a cylindrical surface coaxial with the shaft 26.
6 are attached to the coils 21a,
It rotates inside 21b. Shaft 2
6, the area where the metal body 27 and the coils 21a and 21b are opposed to each other changes.
The inductance of b changes. This change in inductance is converted into a required electric signal by the rectifier circuit 42 and the amplifier circuit 43 and output to the outside through the input / output terminal 44. In FIG. 1, reference numeral 45 denotes an input / output terminal 44 of the case 33.
The resin that seals the lead-out portion is shown.

According to the displacement detecting device 32 shown in FIG. 1, the coils 21a and 21b are not arranged on the circuit board 29, but the cylindrical housing 2 surrounding the shaft 26.
3, it is easy to secure the formation area, that is, the formation area is not easily limited, and thus it is possible to easily secure the required inductance value and resistance value. It is possible and the design flexibility is large. In the example described above, the coils 21a, 2
1b is constituted by the FPC 22, but the coil 21
A and 21b may be of a flexible sheet shape, and may be formed, for example, directly on the housing 23 by printing or vapor deposition.

In this embodiment, the metal body 27 formed separately from the shaft 26 is attached to the shaft 26. However, the shaft 26 and the metal body 27 are formed integrally with a metal having good conductivity. You may. On the other hand, as shown in FIG.
A configuration in which a flange 46 having the same shape as that of 7 is formed of resin and attached to the shaft 26, and a metal body 27 having a film shape is provided on the peripheral surface of the flange 46 as shown in the figure can also be adopted. In this case, the shaft 26 and the flange 4
6 may be integrally formed of resin.

The metal member 27 in the form of a film, that is, a metal film can be constituted by, for example, an electroless plating film. Further, for example, a metal foil may be attached to the peripheral surface of the flange 46. Further, in this example, the case 33 is made of metal, so that the effect of the conductor existing outside the device on the coils 21a and 21b can be prevented. When the case 33 is used, if the case 33 is formed of an insulating material such as a resin which does not cause an eddy current effect, and the coils 21a and 21b are arranged and formed directly on the inner peripheral surface of the case 33, the housing 23 is unnecessary. The configuration can be simplified and the size can be reduced accordingly.

In this example, the two coils 21a, 21a
1b, but the number of coils may be one. FIG. 5 shows an FPC2 on the outer peripheral surface of the housing 23.
2 shows an example in which the coil 21 formed by the metal 2 is arranged, and the metal body 27 is located outside the coil 21. In this example, as shown in FIG.
Reference numeral 7 denotes a semi-cylindrical plate portion 47 and a flat plate portion 48 provided at one end thereof. The flat plate portion 48 is attached to and supported by the shaft 26.

FIGS. 6A and 6B show the positional relationship between the coil 21 and the metal body 27 in FIGS.
Are shown when viewed from the axial center direction. These show the case where the rotating metal body 27 faces the inside of the coil 21 and the case where the rotating metal body 27 faces the outside of the coil 21, for example, as shown in FIG. 6C. Metal body 2 integrally rotating on both inside and outside of coil 21
7, 27 'may be arranged.

FIG. 7 shows an example of an arrangement relationship between the coil 21 and the metal body 27 when the diameter of the shaft 26 is large. In this example, the coil 21 formed by the FPC 22 is disposed on the outer peripheral surface of the housing 23. The shaft 26 is made of resin.
A metal body 27 in the form of a film is provided on the peripheral surface of. This metal body 27 is made of an electroless plating film or a metal foil as in the case of FIG.

By adopting such a configuration, even if the diameter of the shaft 26 is large, the overall size can be reduced, and the required coil 21 can be easily formed. In the case of the structure shown in FIG. 7, the shaft 26 and the housing 23 can be easily manufactured by resin molding, and the metal body 27 and the coil 21 are arranged on the respective outer peripheral surfaces, and the shaft 26 and the housing 23 are connected to each other. The coaxial center allows the metal body 27 to be
3 can be rotated concentrically with the coil 3, so that the coil 2 can be rotated as compared with the structure of the conventional displacement detecting device shown in FIG.
The distance between the metal member 1 and the metal body 27 can be kept at a certain accuracy, and in that respect, good electrical performance can be obtained.

FIG. 8 is similar to FIG. 7 in that when the diameter of the shaft 26 is large, the shaft 26 is made of a metal having good conductivity, and the shaft 26 itself functions as a metal body that changes the inductance of the coil 21. In this example, as shown in FIG.
A notch 51 is provided in a portion facing the coil 21 of No. 6. According to this configuration, the rotation of the shaft 26 causes the remaining shaft 26
Since the area where the circumferential surface of the coil faces the coil 21 changes,
As a result, the inductance of the coil 21 changes, and the number of parts can be reduced because a metal body is not required separately from the shaft 26.

[0027]

As described above, according to the present invention, since the coil is arranged on the cylindrical surface coaxial with the shaft, compared with the structure of the conventional displacement detecting device,
It is easy to secure the area for forming the coil, and therefore, it is possible to obtain a displacement detection device which is small in size as a whole and in which the required inductance and resistance of the coil are secured. In particular, when the diameter of the shaft is large, the coil can be formed without being affected by the size of the diameter of the shaft, and a remarkable effect of miniaturization can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is an exploded perspective view of a main part in FIG.

FIG. 3 is a block diagram for explaining a circuit configuration in FIG. 1;

FIG. 4 is a diagram illustrating an example in which a metal body is a metal film.

FIG. 5 is an exploded perspective view of a main part for describing a configuration in which a metal body is located outside a coil.

FIG. 6 is a view for explaining various forms of arrangement relation between a coil and a metal body.

FIG. 7 is an essential part perspective view for explaining one embodiment of the present invention when the diameter of the shaft is large.

FIG. 8 is an exploded perspective view of a main part for describing another configuration example of the present invention when the diameter of the shaft is large.

FIG. 9 is a perspective view schematically showing a conventional contactless displacement detection device.

FIG. 10 is a diagram for explaining the inductance of a coil wound in a spiral shape.

FIG. 11 is a perspective view schematically showing the configuration of a conventional non-contact displacement detection device when the diameter of a shaft is large.

Claims (8)

[Claims] 1. A coil, a shaft, and a metal body integrated with the shaft and having an area facing the coil that changes with rotation of the shaft, wherein a change in inductance of the coil due to a change in the area facing the coil. A contactless displacement detection device configured to extract a signal as an electric signal, wherein the coil is disposed on a cylindrical surface coaxial with the shaft. 2. The non-contact type displacement detecting device according to claim 1, wherein the shaft and the metal body are integrally formed. 3. The contactless displacement detection device according to claim 1, wherein the metal body is a metal film provided on a peripheral surface of a resin flange integrated with the shaft. Non-contact type displacement detector. 4. The contactless displacement detection device according to claim 3, wherein the shaft and the flange are formed integrally. 5. The contactless displacement detection device according to claim 1, wherein the shaft is made of a resin, and the metal body is a metal film provided on a peripheral surface of the shaft. Non-contact type displacement detector. 6. The contactless displacement detecting device according to claim 3, wherein the metal film is an electroless plating film. 7. The non-contact type displacement detecting device according to claim 3, wherein the metal film is a metal foil and is attached to the peripheral surface. Detection device. 8. A metal shaft, and a coil disposed on a cylindrical surface coaxial with the shaft. A notch is provided in a portion of the shaft facing the coil, and the coil and the shaft are provided. A contactless displacement detection device characterized in that the area of the surface facing the peripheral surface changes with the rotation of the shaft, and the change in inductance of the coil due to the change is taken out as an electric signal.