JP2015125057A - Eddy current type displacement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eddy current type displacement sensor having excellent detection accuracy.SOLUTION: An eddy current type displacement sensor 10 includes: an oscillation circuit 12 oscillating a coil 14 which is provided on a plane surface and which is formed by winding a conducting wire in a rectangular shape; a metal plate 17 displaced along long side parts 14a, 14b in a manner not to cover the whole of a space closed by the coil 14; and a CPU 16 detecting a position of the metal plate 17 through a partial pressure of the coil 14.

Description

  The present invention relates to an eddy current displacement sensor.

  Patent Document 1 discloses an eddy current displacement sensor that detects the position of a metal plate by using an eddy current generated in the metal plate. In this eddy current type displacement sensor, utilizing the fact that the inductance of the coil decreases when the metal plate is brought close to the coil to which an electrical signal is applied, the position of the metal plate is detected by monitoring the partial voltage signal of the coil. .

JP 58-105460 A

  The decrease in the inductance of the coil is caused by the fact that the magnetic flux generated from the coil is blocked by the metal plate. Moreover, the conducting wire to which the electric signal is applied forms a concentric magnetic field. Furthermore, the magnetic flux density is inversely proportional to the distance from the conductor. For these reasons, when a coil in which a conducting wire is wound in a rectangular shape on a plane is adopted and an attempt is made to detect the position of the metal plate that moves so as to cover the entire coil along the long side of the coil, Since the position and the amount of magnetic flux blocked by the metal plate are not constant, it is difficult to accurately determine the position of the metal plate.

  The present invention has been made in view of such a situation, and an object thereof is to provide an eddy current type displacement sensor with high detection accuracy.

  In order to solve the above problems, an eddy current displacement sensor includes an oscillation circuit that is provided on a plane and that oscillates a coil having a linear portion, and the linear portion that does not cover the entire space closed by the coil. The gist of the present invention is to include a detection target that is displaced along with a detection unit that detects the position of the detection target through the partial pressure of the coil.

  According to this structure, it is suppressed that a detection target interrupts the magnetic flux which arises around the conducting wire part of the coil extended in the direction which cross | intersects with respect to the displacement direction of a detection target. For this reason, since the detection target is not easily affected by magnetic flux generated from the conductive wire portion of the coil that extends in the direction intersecting the displacement direction of the detection target while being displaced, the detection unit detects the displacement of the detection target. The partial pressure of the coil that is detected changes linearly. Thereby, the position of the detection target can be accurately detected.

The said structure WHEREIN: It is preferable that the said coil is comprised by winding conducting wire in a rectangular shape.
According to this configuration, it is possible to accurately detect the position of the detection target by employing a rectangular coil.

The said structure WHEREIN: It is preferable that the said detection target displaces along the long side part of the said coil.
According to this configuration, the detection range is wider than when the detection target is displaced along the short side of the coil.

The said structure WHEREIN: It is preferable that the said detection object consists of a pair of metal plate, and is displaced along two sides which the said coil respectively opposes.
According to this configuration, since the change in the partial pressure of the coil is larger than when there is one detection target, the detection accuracy is further improved.

  The eddy current displacement sensor of the present invention has good detection accuracy.

The block diagram which shows schematic structure of an eddy current type displacement sensor. The graph which shows the difference of this example and a prior art example in an inductance and linearity. The top view which shows another example of a metal plate. The top view which shows another example of a metal plate.

Hereinafter, an embodiment of an eddy current displacement sensor will be described with reference to the drawings.
As shown in FIG. 1, the eddy current displacement sensor 10 includes a power supply 11, an oscillation circuit 12, a resistor 13, a coil 14, an amplification / detection circuit 15, a CPU 16, and a metal plate 17. Yes.

The oscillation circuit 12 generates an oscillation signal from the signal of the power supply 11.
The resistor 13 is interposed between the oscillation circuit 12 and the amplification / detection circuit 15.
One end of the coil 14 is connected between the resistor 13 and the amplification / detection circuit 15, and the other end is grounded. Therefore, a divided voltage signal is generated between the resistor 13 and the coil 14. The divided signal is input to the amplification / detection circuit 15. Here, the coil 14 is wound in a planar shape and a rectangular shape by using a conductive wire of 0.035 mm. The coil 14 has a length of 22 mm in the longitudinal direction and 12 mm in the short direction. The coil 14 includes two long side portions 14a and 14b and two short side portions 14c and 14d.

  The metal plate 17 includes a pair of copper plates 17a and 17b. Each of the copper plates 17a and 17b has a rectangular shape with a length of 24 mm, a width of 2 mm, and a thickness of 0.5 mm. When the coil 14 is viewed from a direction perpendicular to the plane, the copper plate 17a covers the long side portion 14a, and the copper plate 17b covers the long side portion 14b, so that the longitudinal direction of the coil 14, that is, the long side portions 14a and 14b is covered. Displaces along.

The amplification / detection circuit 15 amplifies and detects the divided signal to generate a detection signal.
The CPU 16 monitors the detection signal to detect how much the long side portions 14 a and 14 b of the coil 14 are covered with the metal plate 17. The metal plate 17 corresponds to a detection target, and the CPU 16 corresponds to a detection unit.

  Next, the operation of the eddy current displacement sensor 10 will be described. Here, the simulation result of the eddy current displacement sensor 10 of the present example by a computer and the simulation result of the comparative example will be compared. Here, a simulation is performed until the metal plate covers 21 mm by being displaced in the longitudinal direction so that the amount of the metal plate covering the coil by 1 mm increases from the state where the coil is covered. Here, the inductance and linearity are simulated. Linearity is an index indicating how much the simulation value differs from the ideal value.

  The difference between this example and the comparative example is a metal plate. As shown by a broken line in FIG. 1, the comparative example employs a configuration in which the entire coil 14 is covered with one large metal plate (copper plate). The size of the copper plate employed as a comparative example is 24 mm long, 14 mm wide, and 0.5 mm thick.

  As shown in FIG. 2, the inductance of this example is larger than the inductance of the conventional example. Further, the linearity of this example takes a value closer to 0 (zero) than the linearity of the conventional example. The metal plate of the conventional example covers the entire coil 14, that is, the short side portions 14 c and 14 d in addition to the long side portions 14 a and 14 b, whereas the metal plate 17 of this example is composed of two copper plates 17 a and 17 b and has a long side portion. It is set as the structure displaced so that 14a, 14b may be covered. Therefore, the amount of the metal plate 17 of this example covering the short sides 14c and 14d is smaller than that of the conventional example. That is, the metal plate 17 of this example is configured to be less likely to block the magnetic flux generated around the short sides 14c and 14d, which becomes weaker in inverse proportion to the distance than the conventional example. Thus, if the eddy current displacement sensor 10 of this example is employed, the rate of change of the inductance is constant with respect to the amount of displacement of the metal plate 17 as compared with the conventional example, so the rate of change of the partial pressure signal is also high. It becomes constant. Thereby, the position of the metal plate 17 can be accurately detected from the detection signal.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) A pair of copper plates is used to displace the metal plate 17 that is displaced along the long side portions 14a and 14b so as to cover the long side portions 14a and 14b of the coil 14 that is provided on a flat surface and wound in a rectangular shape. 17a and 17b. The copper plates 17a and 17b were provided so as to be difficult to cover the short side portions 14c and 14d. That is, the copper plates 17 a and 17 b are displaced so as not to cover the entire space closed by the coil 14. Thereby, the copper plates 17a and 17b are difficult to block the magnetic flux generated around the short side portions 14c and 14d. As a result, the rate of change of the partial pressure signal with respect to the amount of displacement of the metal plate 17 becomes constant, so that the position of the metal plate 17 can be detected with high accuracy.

  (2) The metal plate 17 is configured to be displaced along the long side portions 14 a and 14 b of the coil 14. Thereby, compared with the case where it comprises so that it may displace along short side parts 14c and 14d, the range which can detect the position of metal plate 17 is wide.

(3) The metal plate 17 is composed of a pair of copper plates 17a and 17b. As a result, the change in partial pressure is greater than when a single copper plate is used, so that the detection accuracy is better.
In addition, you may change the said embodiment as follows.

In the above embodiment, the metal plate 17 is composed of a pair of copper plates 17a and 17b, but may be composed of a single metal plate.
-In above-mentioned embodiment, although the metal plate 17 displaced along the long side parts 14a and 14b, the structure displaced along the short side parts 14c and 14d may be sufficient.

In the above embodiment, as shown in FIG. 1, the widths of the copper plates 17a and 17b are set longer than the widths of the long side portions 14a and 14b, but may be shorter as shown in FIG.
In the above embodiment, as shown in FIG. 1, the copper plates 17a and 17b are provided so as to cover the entire long side portions 14a and 14b, but as shown in FIG. 4, the long side portions 14a and 14b You may provide so that a part may be covered.

  In the above embodiment, the coil 14 is formed by winding a conducting wire in a rectangular shape, but has a shape provided with linear portions corresponding to the long side portions 14a and 14b of the above embodiment, such as a parallelogram, for example. Also good. In this case, the metal plate is configured to be displaced along the straight portion. Even in such a configuration, the rate of change of the partial pressure signal with respect to the amount of displacement of the metal plate is also constant, so that the position of the metal plate can be detected with high accuracy.

-In the said embodiment, the size of the coil 14 and the size of the copper plates 17a and 17b can be changed suitably.
In the above embodiment, the metal plate 17 is composed of the copper plates 17a and 17b, but this is an example. Various metals can be applied to the metal plate as long as an induced electromotive force is generated by blocking the magnetic flux of the coil 14. It does not have to be plate-shaped.

  In the above embodiment, the eddy current displacement sensor 10 can be applied to various devices that perform control according to the position of the metal plate. For example, it may be used as a shift lever device. In this case, the metal plate 17 is displaced in conjunction with the shift lever.

  DESCRIPTION OF SYMBOLS 10 ... Eddy current type displacement sensor, 11 ... Power supply, 12 ... Oscillation circuit, 13 ... Resistance, 14 ... Coil, 15 ... Amplification / detection circuit, 16 ... CPU, 17 ... Metal plate.

Claims (4)

An oscillation circuit that oscillates a coil provided on a plane and having a linear portion;
A detection object that is displaced along the straight line so as not to cover the entire space closed by the coil;
An eddy current displacement sensor comprising: a detection unit that detects a position of a detection target through a partial pressure of the coil. The eddy current displacement sensor according to claim 1,
The coil is an eddy current displacement sensor configured by winding a conducting wire in a rectangular shape. The eddy current displacement sensor according to claim 2,
The detection target is an eddy current displacement sensor that is displaced along a long side portion of the coil. In the eddy current type displacement sensor according to claim 2 or 3,
The detection target is an eddy current type displacement sensor that includes a pair of metal plates and is displaced along two opposing sides of the coil.