JPH0623659B2 - Displacement measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a displacement amount measuring device suitable for use in detecting or measuring a displacement amount in a mechanical device or an inspection device.

[Outline of Invention]

According to the present invention, a pair of first and second coils, each having a built-in core and wound in a fixed length, are provided close to each other, and the first coil is movably covered with a variable inductance /
The coil and the second coil are covered with a second metal outer cylinder in an adjustable manner to form a fixed inductance coil, respectively. By combining these coils with a detection circuit including a high frequency oscillator and a rectifier, a desired output voltage can be obtained. In addition, the linearity and stability of the device can be maintained, and the device can be downsized and an accurate and uniform product can be manufactured.

[Conventional technology]

In mechanical devices, various scales are used to electrically measure the amount of displacement, but the scales are large and expensive, and there is a drawback that their applications are limited. When the displacement amount is relatively small, the differential transformer is most often used, but the differential transformer has the following three drawbacks.

First, since the core has a structure that moves in and out of the coil,
It is unsuitable when the entire device is longer than the coil of the differential transformer and the displacement amount is long.

Secondly, the differential transformer has a structure in which two coils are lined up in the axial direction, and the length of the two coils lined up is usually about three times longer than the displacement measurement range.

Thirdly, in the structure in which the core goes in and out, the core is cantilevered, which makes it weak against vibration.

Therefore, the present applicant has previously proposed a displacement measuring device that solves the above first to third problems as a structure in which a core that enters the coil is fixed and a metal outer cylinder that covers the outside of the coil is moved. (Japanese Patent Application No. 62-107357).

However, in the case of the displacement measuring device described in this Japanese Patent Application No. 62-107357, since the coils A and B are adjacently arranged side by side in the axial direction, the length of the entire coil becomes large and the entire device eventually becomes large. There is a drawback.

This becomes a problem especially in a hydraulic cylinder, a pneumatic cylinder or the like to which the present device is applied.

Therefore, the present applicant has previously proposed a displacement measuring device capable of reducing the coil length substantially and keeping the desired output voltage, linearity, and stability, thereby reducing the shape of the device (Japanese Patent Application No. 2000-242242). 63-271434).

This displacement measuring device has a first coil which has a built-in core and is wound to a certain length, and a first metal outer cylinder having substantially the same length as the first coil is movably covered. It has an inductance coil and a second coil that has a built-in core and is wound into a fixed length, and a second metal outer cylinder fixed or fixed to this second coil. Covered fixed inductance coil, including high frequency oscillator and rectifier Variable inductance coil and fixed inductance
A detection circuit connected to the coil, the fixed inductance coil is provided separately from the variable inductance coil, and when the first metal outer cylinder moves, a DC voltage corresponding to the displacement amount is output to the output side of the detection circuit. It is configured to obtain.

[Problems to be Solved by the Invention]

However, in the case of the displacement measuring device as described in Japanese Patent Application No. 63-271434, when the second coil as a dummy coil is incorporated in the detector, the inductance of the second coil is adjusted according to the first coil. Since the whole detector is molded with epoxy resin after adjustment, there is a drawback that the second coil cannot be adjusted after molding. That is, even the second metal outer cylinder of the second coil is molded and fixed. In addition, there is a drawback that even if the characteristics of the sensor are slightly adjusted after molding and treatment such as heat aging, it cannot be done.

The present invention has been made in view of the above circumstances, and provides a displacement measuring device capable of adjusting a dummy coil in a final stage after molding a coil and a detector with resin and performing aging.

[Means for Solving the Problems]

The displacement measuring device according to the present invention has a first coil which has a built-in core and is wound to a certain length, and a first metal outer cylinder (4) having substantially the same length as the first coil is moved to the first coil. It has a variable inductance coil (A) that is covered as much as possible and a second coil that has a built-in core and is wound to a certain length, and a second coil that is approximately the same length or shorter than this second coil. 2 A fixed inductance coil (B) that covers the metal outer cylinder (5) adjustably,
High frequency oscillator (OSC) and rectifier (D ₁ , r ₁ , C ₁ ), (D ₂ , r ₁ , C ₂ )
It includes a variable inductance coil (A) and a detection circuit (10) connected to the fixed inductance coil (B), and the fixed inductance coil (B) is provided close to the variable inductance coil (A). , The first metal outer cylinder (4)
When the motor moves, the detection circuit detects the DC voltage according to the displacement.
It is configured to be obtained at the output side of (10).

[Action]

A first metal outer cylinder (4) is movably provided for the variable inductance coil (A), and a fixed inductance coil is provided.
For (B), the second metal outer cylinder (5) is provided so as to be adjustable, and both coils are arranged close to each other. That is, the variable inductance coil (A) and the first metal outer cylinder (4) are provided on the measured side, that is, the moving body side to be measured, and the fixed inductance coil (B) and the second metal outer cylinder (5) are also variable. Provide it close to the inductance coil (A). Then, in terms of a circuit, both of these coils are connected to the detection circuit (10). Then, the inductance of the variable inductance coil (A) is changed by the movement of the first metal outer cylinder (4). The first metal outer cylinder (4) acts as a short-circuit secondary coil provided outside the variable inductance coil (A), and the first metal outer cylinder (4)
The inductance of the variable inductance coil A in the portion covered by (4) is significantly reduced. The amount of displacement can be detected by changing the displacement of this inductance into a voltage. In this case, the second metal outer cylinder (5) covering the fixed inductance coil (B) can move freely regardless of the molding of the coil and the detector, so that an accurate and uniform product can be manufactured.

〔Example〕

An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 shows a first embodiment of the present invention, which is a so-called separated type in which the coil portion and the detector side are separated, and here only the coil portion is shown. In the figure, (1) is a coil outer cylinder, (2) is a support fitting, and A is a variable inductance
A main coil as a coil and B is a dummy coil as a fixed inductance coil. The coil outer cylinder (1) is inserted into the hole of the support fitting (2), in which the cable (3) and the lead wires of the coils A and B are connected. In the coil outer cylinder (1), a short dummy coil B having a length of, for example, about 5 mm is wound in the original direction, and subsequently a long main coil A is wound. The length of the main coil A usually ranges from 20 mm to several hundred mm.

The main coil A is located outside the coil outer cylinder (1) with respect to the main coil A.
The first metal outer cylinder (4) having substantially the same length as is continuously movable. Further, a second metal outer cylinder (5) having a length of, for example, about 4 mm is provided outside the coil outer cylinder (1) with respect to the dummy coil B, and the second metal outer cylinder (5) is moved by hand. it can. An insulator cover (6) made of, for example, plastic is provided as a so-called cap on the outer side of the second metal outer cylinder (5) adjacent to the support fitting (2).

Finally, the support fitting (2), the main coil A, the dummy coil B, etc. are molded with, for example, an epoxy resin, but the first and second metal outer cylinders (4), (5) are not molded. In this case, the coil is substantially lengthened by about 10 mm in the dummy coil B, but the output characteristic can be adjusted by sliding the second metal outer cylinder (5) after the sensor is completed. After the adjustment, the dummy coil B is fixed with an adhesive and the cover (6) is covered to complete the finish.

FIG. 2 shows a second embodiment of the present invention, in which the detector and the coil are integrated. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

Conventionally, the dummy coil B is housed in the detector (7), but since it cannot be adjusted after molding, in this embodiment, the dummy coil B is provided outside the detector (7) as shown in FIG. Also in this case, the dummy coil B has a length of about 10 mm, but the output characteristic can be adjusted by sliding the second metal outer cylinder (5) after the sensor is completed. After the adjustment, the dummy coil B is fixed with an adhesive and the cover (6) is covered to complete the finish.

FIG. 4 shows an example of the detection circuit (10) used in the present invention. This detection circuit (10) applies a high frequency voltage to the coils A and B in the reverse direction by the high frequency oscillator OSC to change the inductance. The AC voltage across the resistor R _{S that} changes due to the rectifier (D ₁ , r ₁ , C ₁ ) and (D ₂ , r ₂ , C ₂ ) including the smoothing circuit is converted to a DC voltage, and the difference voltage is converted to the capacitor C _I try to take out as output at both ends of ₃ . The detection circuit (10) need not be such a differential type, but the differential type has better linearity and temperature characteristics.

In the present embodiment, the coil B is fixed as a dummy to a certain fixed value, and the change in the inductance of the main coil A is used, so that the output voltage greatly shifts up and down depending on the characteristic position of the dummy coil B. Therefore, the adjustment of the dummy coil B is slightly effective for adjusting the output voltage to a certain standard value.

FIG. 4 shows that the coils A and B and the second metal outer cylinder (5) are fixed,
The output voltage V _A , V _B obtained at the common terminal (11C) and output terminals (11A), (11B) of the detection circuit (10) when the first metal outer cylinder (4) is displaced is shown. , The output voltage V _B between the common terminal (11C) and the output terminal (11B) when the inductance of the coil B is at P ₁ by moving the second metal outer cylinder (5) is around 9V. Also moves the second metal outer cylinder (5) and the common terminal (11C) when the inductance of the coil B is P _2.
It can be seen that the output voltage V _B (P ₂ ) between the output terminal and the output terminal (11B) is approximately 11V. That is, it can be seen that the output voltage V _B changes depending on how the second metal outer cylinder (5) is set.

Since the output voltage of the detection circuit (10) is the difference between the voltages V _A and V _B , that is, the voltage between the output terminals (11A) and (11B), the output voltage V when the inductance of the coil B is P _1.
A -V _B (P ₁₎ becomes a straight line that varies between 0V from + 6V as Figure 5, the output voltage _V A -V _B (P ₂₎ when the inductance of the coil B is in the _{P 2} fifth ± 3V as shown
It becomes a straight line that changes between.

Here, when the dummy coil B is adjusted to the inductance P ₂ , the output voltage V _A −V _B (P ₂ ) is ± 3 as described above.
The output voltage is V, but if the linearity is not corrected properly, the output voltage 0 point deviates from the center. Thus, the dummy coil B is set according to the main coil A, and even if the setting is slightly deviated, the deviation of the origin of the straight line (output voltage 0) becomes conspicuous. Therefore, it is necessary to finely adjust the second metal outer cylinder (5) and adjust the dummy coil B.

The support metal fitting (2) in Fig. 1 is made of brass rod and its outer diameter is φ6 and its length is 20mm.
(1) has outer diameter φ4, inner diameter φ2.8 length 100 mm, dummy coil B has core length 5 mm, coil 0.06 φ, copper wire 140 turns length 4 mm, second metal outer cylinder made of brass Inner diameter φ4.1,
When the outer diameter is 4.6 mm and the length is 4 mm, the cover (6) is made of black bakelite, and the inner diameter is 4.8 mm, the outer diameter is 5.6 mm, and the length is 10 mm,
It was possible to adjust both the P ₁ point and the P ₂ point in FIG. 4 by moving the second metal outer cylinder (5).

FIG. 6 shows an example in which the parts of the coils A and B used in this embodiment are concretely shown. The core (7) has an outer diameter φ1.8 and an inner diameter φ.
Using a ferrite core bead having a length of 0.7 mm and a ferrite core bead having a diameter of 0.7, it was placed and fixed as shown in FIG. Fig. 9B when making a lot
The dummy coil B and the core (7) of the main coil A are separately wound as shown in (3) and soldered between them. One side of coil A Wire (8) as shown in Fig. 9B
I soldered it on and made the handling of the lead wire easy.

〔The invention's effect〕

As described above, according to the present invention, the coil and the detector are molded with resin, and after aging, the second step is performed at the final stage.
Since the metal outer cylinder (5) can be moved to adjust the dummy coil B, an accurate and uniform product can be produced. Further, since the main coil A and the dummy coil B are substantially close to each other and integrated, it is possible to maintain compatibility with both the detector and the coil, which is easy to use and easy to make. There is a big profit in terms of it. Further, since the dummy coil B is arranged close to the main coil A, the mutual influence of the two coils on the temperature change is offset, and the temperature characteristic is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIG. 3 is a circuit block diagram showing an example of a detection circuit used in the present invention. 4 and 5 are diagrams showing displacement detection characteristics according to the present invention, and FIG.
The figure is a block diagram showing the essential parts of the present invention. (4) is the first metal outer cylinder, (5) is the second metal outer cylinder, (7) is the detector, (10) is the detection circuit, A is the main coil, B is the dummy coil, OSC is the high frequency oscillator, (D ₁ , r ₁ , C ₁ ) and (D ₂ , r ₂ , C ₂ ) are rectifiers.

Claims (1)

[Claims] 1. A first coil having a built-in core and wound to a predetermined length.
A variable inductance coil having a coil, and a first metal outer cylinder of substantially the same length movably covering the coil, and a second coil having a built-in core and wound to a certain length. A fixed inductance coil in which the second metal outer cylinder having a length substantially equal to or shorter than that of the coil is adjustable, and a high frequency oscillator and a rectifier are included, and the variable inductance coil and the fixed inductance coil are connected. The fixed inductance coil is provided close to the variable inductance coil, and when the first metal outer cylinder moves, a DC voltage corresponding to the displacement amount is output to the output side of the detection circuit. Displacement measuring device characterized by being obtained.