JP2017075919A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector capable of making variation of induced electromotive force at the time when a detected part actuates large.SOLUTION: A position detector 1 includes: an exciting coil 3 excited by a constant voltage AC; a detection coil 4 configured to generate induced electromotive force by mutual induction with the exciting coil 3; a detection object 5 interlocked with a detected part 2 to change the induced electromotive force of the detection coil 4. The detection coil 4 includes a first coil part 4a and a second coil part 4b of which coil winding directions are reverse to each other by employing a shape (a truncated chevron shape) folded back in the middle of a coil. The detection object 5 includes a non-magnetic body 5a capable of covering the first coil part 4a, and a magnetic body 5b capable of covering the second coil part 4b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a position detection device that detects the position of a detected portion.

  Conventionally, a position detection device that calculates a position (distance) of a detected portion by applying a magnetic field from an excitation coil to a detection coil and detecting a change in the magnetic field applied to the detection coil in accordance with the approach or separation of a metal portion Is well known (see Patent Documents 1 and 2, etc.). In this type of position detection device, the excitation coil and the detection coil are electromagnetically coupled, and the distance to the detected part is calculated based on the induced electromotive force of the detection coil that changes according to the approach or separation of the metal part. .

JP 2008-37180 A JP 2006-262422 A

  In this type of position detection device, there is a need to improve the position detection resolution by taking a large change in the induced electromotive force when the metal part moves with respect to the detection coil during operation of the detected part. It was.

  The objective of this invention is providing the position detection apparatus which can take the change of an induced electromotive force large when a to-be-detected part act | operates.

  A position detection device that solves the above problems includes an excitation coil excited by a constant voltage, a detection coil that generates an induced electromotive force by electromagnetic coupling with the excitation coil, and the induced electromotive force at a position of a detected portion. In a configuration including a detection target to be changed according to the position and a position calculation unit that detects the position of the detected portion based on the induced electromotive force, the detection coil is folded around the coil so that the coil is wound. A first coil portion and a second coil portion whose directions are opposite to each other are provided, and the detection target covers a magnetic body capable of covering one of the first coil portion and the second coil portion, and the other. And a non-magnetic material capable of.

  According to this configuration, the first coil portion and the second coil portion in which the winding directions of the coils are opposite to each other are provided by forming the detection coil in a folded shape in the middle. Then, the detection target that approaches or separates from the detection coil is configured as a magnetic body and a non-magnetic body, one of which is opposed to the first coil portion and the other is opposed to the second coil portion. Thereby, when the detection target approaches or separates from the detection coil, the mutual inductance of the first coil portion covered with the non-magnetic material and the mutual inductance of the second detection coil portion covered with the magnetic material are positive and negative. Take the opposite value. Therefore, since the mutual inductance viewed from the circuit end of the detection circuit that detects the output of the detection coil changes in the same direction, the mutual inductance can be greatly changed. Therefore, it is possible to greatly change the induced electromotive force when the detected portion is activated.

  In the position detection device, it is preferable that the excitation coil and the detection coil are arranged to face each other so that the detection target moves reciprocally along the axial direction of the excitation coil and the detection coil. According to this configuration, it is possible to detect the position of the detected portion that moves along the axial direction of the excitation coil and the detection coil.

  In the position detection device, the detection coil is preferably formed in an eight-letter shape in which the annular first coil portion and second coil portion are arranged in a plane direction. According to this configuration, the detection coil can be formed in a simple shape such as an eight-letter shape.

  In the position detection device, the magnetic body is preferably formed thicker than the non-magnetic body. According to this configuration, it is possible to make a large change in the mutual inductance of the detection coil covered with the magnetic material, which is further advantageous in taking a large change in the induced electromotive force.

  According to the present invention, in the position detection device, it is possible to greatly change the induced electromotive force when the detected portion is activated.

The block diagram of the position detection apparatus of one Embodiment. The top view of an exciting coil, a detection coil, and a detection target. The block diagram of the conventional position detection apparatus. The characteristic diagram of the mutual inductance of the conventional position detection apparatus, the exciting current, and the self-inductance of the exciting coil. The operation | movement figure of a position detection apparatus when a detection target approaches a detection coil. The characteristic diagram of the mutual inductance of a position detection apparatus, an exciting current, and the self-inductance of an exciting coil.

Hereinafter, an embodiment of the position detection device will be described with reference to FIGS.
As shown in FIG. 1, the position detection device 1 is a kind of eddy current sensor, and detects the position of the detected portion 2. The position detection device 1 includes an excitation coil 3 excited by a constant voltage, a detection coil 4 that generates an induced electromotive force V _DE by electromagnetic coupling with the excitation coil 3, and an induced electromotive force V _DE at the position of the detected portion 2. And a detection object 5 to be changed according to the above. The detection target 2 is attached to the detection target 5 and operates integrally with the detection target 5. The excitation coil 3 and the detection coil 4 are arranged to face each other so as to face each other.

  As shown in FIGS. 1 and 2, the exciting coil 3 is formed in an annular shape (square annular shape) in which coil wiring is wound around. The exciting coil 3 includes a substrate pattern formed by attaching coil wiring to a substrate (not shown) of the position detection device 1.

  The detection coil 4 is formed in a shape in which the coil is folded halfway. The detection coil 4 of this example includes a first coil portion 4a and a second coil portion 4b in which the coil winding directions are reversed by forming the coil in the middle. The detection coil 4 is formed in an eight-letter shape in which the first coil portion 4a and the second coil portion 4b are arranged in the plane direction by folding the center of the coil, so that the winding direction is right and left half. They are formed so as to be opposite to each other. The detection coil 4 includes a substrate pattern formed by attaching coil wiring to a substrate (not shown) of the position detection device 1. The detection coil 4 is disposed so as to overlap the excitation coil 3 in plan view.

  The detection target 5 is formed of a flat metal plate (metal part), and is formed in a shape capable of covering both the first coil part 4a and the second coil part 4b of the detection coil 4. The detection target 5 of this example includes a nonmagnetic body 5a capable of covering the first coil portion 4a and a magnetic body 5b capable of covering the second coil portion 4b. The detection target 5 takes a reciprocating motion along the axial direction of the excitation coil 3 and the detection coil 4 (the direction of the arrow R in FIG. 1), and approaches the first coil portion 4a in accordance with the motion of the detected portion 2. Or reciprocate linearly so as to be separated. The nonmagnetic material 5a is preferably made of copper, for example. The magnetic body 5b is preferably made of iron, for example.

As shown in FIG. 1, the position detection device 1 includes a position calculation unit 6 that calculates the position of the detected unit 2 based on the induced electromotive force V _DE output from the detection coil 4. The position calculation unit 6 is connected to the excitation coil 3 via an excitation circuit 7 necessary for exciting the excitation coil 3, and is connected to the detection coil 4 via a detection circuit 8. The exciting circuit 7 excites the exciting coil 3 with a constant voltage alternating wave (alternating voltage Vac). The detection circuit 8 is a circuit that can detect a change in the amplitude of the induced electromotive force V _DE (output voltage) output from the detection coil 4.

Next, the operation of the position detection apparatus 1 will be described with reference to FIGS. 1 and 3 to 6.
As shown in FIG. 1, when an AC voltage Vac having a constant voltage amplitude is applied from the excitation circuit 7 to the excitation coil 3, an induced electromotive force V _DE corresponding to the distance K from the detection target 5 is applied to the detection coil 4. Occur. The induced electromotive force V _DE is obtained from the equation (α) shown in FIG. The position calculation unit 6 detects the amplitude of the induced electromotive force V _DE by the detection circuit 8, and calculates the distance K between the detection coil 4 and the detection target 5, that is, the position of the detected unit 2 from the value.

One of the parameters for calculating the induced electromotive force V _DE is a mutual inductance M between the excitation coil 3 and the detection coil 4. Incidentally, for example, when the detection target 5 is not present, the mutual inductance M takes the same value in the first coil portion 4a and the second coil portion 4b formed by folding the coil wire into an eight shape. For this reason, assuming that the detection target 5 does not exist, the mutual inductance M is “0” when viewed from the detection circuit 8 side. Therefore, when the detection target 5 does not exist, the induced electromotive force V _DE is also “0”.

As can be seen from the equation (α) in FIG. 1, the calculation of the induced electromotive force V _DE mainly includes the mutual inductance M of the excitation coil 3 and the detection coil 4, the excitation current I _EX flowing through the detection target 5, and the excitation coil. 3 parameters of the self-inductance L _EX are related. That is, when the detection object 5 approaches and separates from the detection coil 4, these parameters need to be optimally changed in order to obtain a large change in the induced electromotive force _VDE .

Here, FIG. 3 shows a configuration of a conventional positioning position detection device 1, and FIG. 4 shows a parameter (corresponding to a change in the distance between the detection coil 4 and the detection target 5 in the conventional positioning position detection device 1. The change waveforms of the mutual inductance M, the excitation current I _EX , and the self-inductance L _EX of the excitation coil 3 are shown. In the conventional position detection device 1, the detection coil 4 has a simple rectangular shape, and the detection target 5 is formed in a shape that can cover the entire detection coil 4. In this case, when the exciting coil 3 is excited with a constant voltage amplitude, the excitation current I _EX also changes due to the change of the self-inductance L _EX when the distance of the detection target 5 changes, but the distance K becomes closer. In some cases, the exciting current I _EX changes so as to cancel out the change in the mutual inductance M, so that there is a problem that the induced electromotive force V _DE becomes small.

  In the case of this example, as shown in FIG. 5, the following two phenomena occur when the detection target 5 approaches the detection coil 4. The first phenomenon is that when the detection target 5 approaches the detection coil 4, an eddy current is generated in the nonmagnetic material 5 a (nonmagnetic metal plate), and the magnetic flux B <b> 2 is in a direction that prevents the magnetic flux B <b> 1 from the excitation coil 3. Occur. This magnetic flux B2 is applied to the first coil portion 4a. Thereby, the absolute value of the mutual inductance M of the detection coil 4 decreases. The second phenomenon is that when the detection target 5 approaches the detection coil 4, the magnetic body 5 b (magnetic metal plate) acts to increase the magnetic flux B <b> 1 generated from the excitation coil 3. For this reason, the absolute value of the mutual inductance M of the detection coil 4 covered with the magnetic body 5b increases.

  By the way, the mutual inductance M of the detection coil 4 due to the first phenomenon and the mutual inductance M of the detection coil 4 due to the second phenomenon have opposite signs. Therefore, when viewed from the circuit end of the detection circuit 8, these mutual inductances M change in the same direction with respect to the distance K to the detection target 5.

On the other hand, as the detection object 5 approaches, the self-inductance L _EX of the exciting coil 3 decreases in the right half and increases in the left half. For this reason, the self-inductance L _EX viewed from the end of the excitation circuit 7 does not change. That is, the excitation current I _EX does not need to change depending on the distance of the detection target 5.

FIG. 6 shows a change waveform of each parameter (mutual inductance M, excitation current I _EX , self-inductance L _EX of the excitation coil 3) according to a change in the distance between the detection coil 4 and the detection target 5 in the position detection device 1 of this example. Indicates. As shown in the figure, the mutual inductance M is a component of the induced electromotive force V _DE, during approach / separation of the detection target 5 changes largely. Further, since the exciting current I _EX does not change, the mutual inductance M is not disturbed. As described above, a large change in induced electromotive force V _DE can be obtained.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) In the position detection device 1, the first coil part 4a and the second coil part 4b in which the winding directions of the coils are opposite to each other by making the detection coil 4 folded in the middle (eight-letter shape). Is provided. Then, the detection object 5 that approaches or separates from the detection coil 4 is configured as a non-magnetic material 5a and a magnetic material 5b, one of which is opposed to the first coil portion 4a and the other is opposed to the second coil portion 4b. Thereby, when the detection target 5 approaches or separates from the detection coil 4, the mutual inductance M of the first coil part 4a covered with the nonmagnetic material 5a and the mutual of the second coil part 4b covered with the magnetic material 5b are mutually. The inductance M takes a positive / negative judgment value. Therefore, since the mutual inductance M seen from the circuit end of the detection circuit 8 that detects the output of the detection coil 4 changes in the same direction, the change of the mutual inductance M can be made large. Therefore, a large change in the induced electromotive force V _DE when the detected portion 2 is activated can be taken. As a result, the position detection resolution of the position detection device 1 is improved.

  (2) The excitation coil 3 and the detection coil 4 are arranged to face each other so as to face each other. The detection object 5 takes a reciprocating motion along the axial direction of the excitation coil 3 and the detection coil 4 (in the direction of arrow R in FIG. 1). Therefore, the position of the detected portion 2 that moves along the axial direction of the excitation coil 3 and the detection coil 4 can be detected with high accuracy.

  (3) The detection coil 4 is formed in an eight-letter shape in which an annular first coil portion 4a and second coil portion 4b are arranged in the plane direction. Therefore, the detection coil 4 can be made of a simple member having an eight-letter shape.

(4) The magnetic body 5b is preferably formed thicker than the non-magnetic body 5a. In this case, the change in the mutual inductance M of the detection coil 4 covered with the magnetic body 5b can be made large, which is more advantageous for making a large change in the induced electromotive force _VDE .

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
The detection target 5 is not limited to being formed by a single plate. That is, the nonmagnetic material 5a and the magnetic material 5b may be separate from each other.

The non-magnetic body 5a and the magnetic body 5b preferably have a shape that completely covers the detection coil 4 (the first coil portion 4a and the second coil portion 4b).
The nonmagnetic body 5a and the magnetic body 5b may be formed with different areas and shapes.

The nonmagnetic body 5a and the magnetic body 5b are not limited to be arranged on the same plane, and may be arranged on different planes.
The detection target 5 may have a shape that covers only a part of the detection coil 4.

The detection target 5 is not limited to a metal member (metal part, metal plate), and may be a movable coil wound with coil wiring, for example.
-The 1st coil part 4a does not necessarily take the same coil area as the 2nd coil part 4b, You may form a coil area small.

The excitation coil 3 and the detection coil 4 are not limited to a single winding shape, and may be a shape in which a plurality of coil wirings are wound.
When the excitation coil 3 and the detection coil 4 are formed in a substrate pattern, they are not limited to being formed on the same substrate, and may be provided on different substrates.

The excitation coil 3 and the detection coil 4 are not limited to being formed with a substrate pattern, and may be formed at a position not on the substrate.
The excitation coil 3 and the detection coil 4 are not limited to be formed in the same area, and the excitation coil 3 may be formed larger than the detection coil 4, for example.

The detection target 5 is not limited to moving up and down along the axial direction of the detection coil 4, but may be one that moves (slides) in a direction intersecting the axial direction, for example.
The metal detection target 5 (non-magnetic body 5a, magnetic body 5b) is not limited to a rectangular metal plate, but may be changed to another shape such as a circle.

The shape of the exciting coil 3 can be changed to other shapes such as a circular shape.
The detection coil 4 can be changed to other shapes as long as it has the first coil portion 4a and the second coil portion 4b.

-The 1st coil part 4a and the 2nd coil part 4b are not restricted to square shape, For example, it can change into other shapes, such as circular shape.
The detection target 5 may be the fixed side, and the excitation coil 3 and the detection coil 4 may be the movable side.

-The position detection apparatus 1 of this example can be used for various apparatuses and systems, such as a shift lever apparatus of a vehicle, a vehicle-mounted switch apparatus, for example.
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.

  (A) In the position detection device, the detection target is formed with an area capable of covering the entire detection coil. According to this configuration, it is more advantageous to take a large change in the induced electromotive force.

DESCRIPTION OF SYMBOLS 1 ... Position detection apparatus, 2 ... Detected part, 3 ... Excitation coil, 4 ... Detection coil, 4a ... 1st coil part, 4b ... 2nd coil part, 5 ... Detection object, 5a ... Non-magnetic material, 5b ... Magnetic Body, 6 ... position calculation unit, V _DE ... induced electromotive force, R ... axial direction of the coil.

Claims (4)

An excitation coil that is excited by a constant voltage, a detection coil that generates an induced electromotive force by electromagnetic coupling with the excitation coil, a detection target that changes the induced electromotive force in accordance with the position of the detected portion, and the induced electromotive force In a position detection device comprising a position calculation unit that detects the position of the detected portion based on electric power,
The detection coil includes a first coil portion and a second coil portion in which the winding directions of the coils are opposite to each other by being folded back in the middle of the coil,
The position detection apparatus, wherein the detection target includes a magnetic body capable of covering one of the first coil section and the second coil section and a non-magnetic body capable of covering the other. The excitation coil and the detection coil are arranged opposite to face each other,
The position detection apparatus according to claim 1, wherein the detection target moves reciprocally along an axial direction of the excitation coil and the detection coil. The position detection device according to claim 1, wherein the detection coil is formed in an eight-letter shape in which the annular first coil portion and second coil portion are arranged in a plane direction. The position detection device according to claim 1, wherein the magnetic body is formed thicker than the non-magnetic body.

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