WO2019142780A1

WO2019142780A1 - Position detection device

Info

Publication number: WO2019142780A1
Application number: PCT/JP2019/000917
Authority: WO
Inventors: 正之三木; 川村　佳嗣
Original assignee: 三木篤子
Priority date: 2018-01-16
Filing date: 2019-01-15
Publication date: 2019-07-25
Also published as: CN111868480A; KR20200104900A; JPWO2019142780A1; JP6778339B2; CN111868480B

Abstract

[Problem] To provide a position detection device capable of detecting the position in a wide range in order to detect a movement distance of an object to be measured. [Solution] A position detection device comprises: a first exciting coil: a reference coil; a second exciting coil; an output coil; and a magnetic response element. The mutual inductance value of the first exciting coil and the reference coil is constant. The mutual inductance value of the second exciting coil and the output coil through the magnetic response element monotonously increases or decreases with respect to the relative movement distance between the magnetic response element and the output coil. The reference coil and the output coil are differentially connected. By detecting the position on the basis of a difference in output voltage between the reference coil and the output coil, the position detection device capable of detecting the position in a wide range with high noise tolerance.

Description

Position detection device

The present invention relates to a position detection device, and more particularly to a position detection device capable of detecting the displacement of a detection object in a wide range.

Conventionally, differential transformers are known as position detection devices. The differential transformer applies an alternating voltage to the primary coil (excitation coil) and detects the difference between the voltages induced in the two secondary coils (detection coils). In a differential transformer, the mutual inductance value between the primary side coil and the two secondary side coils changes depending on the position of the linearly movable magnetic core (movable core) inside the coil, and two secondary A voltage difference occurs in the side coil. Therefore, the magnetic core is connected to the detection target, and the change (displacement) of the position of the detection target is detected by detecting the change of the position of the magnetic core as the voltage difference of the secondary coil.

However, the range of displacement that can be detected by the differential transformer is limited to the range in which the magnetic core moves inside the secondary coil. Therefore, the differential transformer has a problem that it can not detect a wide range of displacement.
Therefore, in Patent Document 1, the shape of the core is a conical or tapered shape in which the cross-sectional area gradually changes depending on the position in the axial direction, and a wide range of positions is detected by "ratio of output voltage" of two adjacent detection coils. Methods are disclosed.
Further, in Patent Document 2, a plate-like magnetic piece whose area changes in the axial direction is attached to the side surface of the square pole core, and the mutual inductance value between the exciting coil and the detecting coil changes depending on the axial position. Disclosed a method for detecting a wide range of positions by "difference in output voltage" of two adjacent detection coils.

JP 2003-75106 Japanese Patent Application Laid-Open No. 63-265115

In the case of the position detection device of Patent Document 1, the “difference in output voltage” of the two detection coils is constant regardless of the position in the axial direction, so the position is detected by the “ratio of output voltages” of the two detection coils. Method. However, since the two detection coils are close to each other, the difference between the output voltages at all positions is small, which causes a problem that the detection sensitivity is low.
Also, since the two detection coils are not differentially connected, there is a problem that no offset effect can be obtained against noise.

In the case of Patent Document 2, since the position is detected by the “difference in output voltage” of the two detection coils, it is possible to obtain an offsetting effect that is an advantage of the differential transformer against noise and temperature change.
However, in order to detect a position by the difference of a voltage, if the difference of a voltage is constant like the document 1, for example, position detection can not be performed. Therefore, it is necessary to change the voltage difference depending on the detection location, and there is a problem that the shape design of the magnetic piece is difficult.
Further, as in Patent Document 1, since the two detection coils are arranged close to each other, the "difference in output voltage" between the two detection coils is always small, and the amount of change in the position-dependent differential voltage is small. Therefore, there is a problem that the detection sensitivity is low.

In view of the above problems, the present invention has an object to provide a position detection device using a differential voltage conversion method capable of detecting the absolute position of an object to be detected over a wide range with high accuracy.

The position detection device according to the present invention is
A first excitation coil, a reference coil, a second excitation coil, an output coil, and a magnetic response body,
The magnetic response body and the output coil are movable relative to each other,
The output voltage of the output coil at the time of applying an AC voltage to the second excitation coil monotonously increases or monotonously depending on the relative movement distance of the magnetic response body with respect to the output coil.
The output voltage of the reference coil at the time of applying an AC voltage to the first excitation coil is constant regardless of the relative movement distance of the magnetic response body with respect to the output coil,
The reference coil and the output coil are differentially connected.

With such a configuration, the voltage output from the output coil is uniquely determined, and the output voltage of the output coil is determined, depending on the relative movement distance between the magnetic response body and the output coil. Since the voltage output from the reference coil is constant regardless of the moving distance, the output voltage of the reference coil can be used as a reference.
Since the output coil and the reference coil are differentially connected, the differential voltage between the output voltage of the output coil and the output voltage of the reference coil serving as a reference cancels out the influence of noise and allows relative movement. It is possible to provide a position detection device capable of detecting the movement distance (or absolute position) in a wide range over the distance.
That is, even if electrical noise intrudes from the outside into the reference coil and the output coil, or even if the electrical resistance change occurs due to a change in environmental temperature, the differential voltage between the two coils is offset by their influence. Be done. Therefore, the position detection device according to the present invention is resistant to noise, reduces fluctuations due to environmental temperature changes, and has high reliability of the detected position.
Furthermore, since the output voltage of the reference coil as a reference is constant, the distance between the differential coil of the output coil and the reference coil as compared with the differential voltage of the adjacent output coil as disclosed in

Patent Documents

1 and 2 Since the amount of change with respect to (change in position) becomes large, the position detection sensitivity is improved.

Further, the position detection device according to the present invention is
The magnetic response body is characterized by including a conductive member whose electric resistance monotonously increases or monotonically decreases along the direction of movement relative to the output coil.

With such a configuration, the mutual inductance value of the second excitation coil and the output coil monotonously increases or decreases monotonously depending on the moving distance due to the eddy current loss. The voltage decreases monotonously or increases monotonously depending on the movement distance, and the movement distance can be detected uniquely.

The position detection device according to the present invention is
The conductive member is
It is characterized in that it is rotationally symmetrical with respect to an axis along the direction of relative movement with respect to the output coil, and its cross-sectional area monotonously decreases or monotonously.

With such a configuration, the electrical resistance of the conductive member in the magnetic response body can be monotonously increased or monotonically reduced along the relative moving direction of the magnetic response body and the output coil.

The position detection device according to the present invention is
The conductive member has a groove on its side wall surface,
The cross-sectional area of the groove may increase or decrease monotonously along the direction of movement relative to the output coil.

With such a configuration, the electrical resistance of the conductive member in the magnetic response body can be easily monotonously increased or monotonically reduced along the relative moving direction of the magnetic response body and the output coil. It becomes possible. The manufacture of the magnetic response body is facilitated, and the manufacturing cost of the position detection device can be reduced.

The position detection device according to the present invention is
The magnetic response body is characterized in that a ferromagnetic member is provided outside or inside the conductive member.

With such a configuration, the temperature dependency of the mutual inductance value between the second excitation coil and the output coil through the magnetic response body can be reduced, and the position where the fluctuation with respect to the environmental temperature is further reduced. It becomes possible to realize a detection device.

The position detection device according to the present invention is
The conductive member is characterized in that the absolute value of the amount of change in electrical resistance along the direction of movement relative to the output coil is larger in a specific area than in the other areas.

With such a configuration, the position detection sensitivity and spatial resolution of a specific area can be improved, and more precise (fine) position detection can be performed only in the specific area. As a result, it is possible to prevent the position detection device from becoming unnecessarily large.

The position detection device according to the present invention is
The magnetic response body is characterized by comprising a ferromagnetic body in which a cross-sectional area monotonously increases or monotonically decreases along a moving direction relative to the output coil.

With such a configuration, the mutual inductance value of the second excitation coil and the output coil via the magnetic response body monotonously increases along the relative movement direction of the magnetic response body and the output coil. Or it can be monotonically decreased, and it becomes possible to uniquely detect the distance along the relative movement direction.

The position detection device according to the present invention is
The output coil and the second excitation coil have the same central axis, and are stacked in the radial direction with respect to the central axis.

With such a configuration, the width of the occupied area by the output coil and the second excitation coil can be shortened, and downsizing of the device or improvement of spatial resolution (more fine position detection) is possible. Become.

The position detection device according to the present invention is
A winding ratio of the reference coil with respect to the first excitation coil and a winding ratio of the output coil 7 with respect to the second excitation coil are the same, and both are larger than one.

With such a configuration, the output voltage of the output coil and the reference coil can be increased, the detection sensitivity of the position detection device can be enhanced, and the burden on the electronic circuit associated with the position detection device can be reduced. .

The position detection device according to the present invention is
A float is connected to the magnetic response body,
A guide is provided for movably supporting the detection body.

With such a configuration, it is possible to realize a position detection device capable of measuring the water level of the liquid level.

The position detection device according to the present invention is
The magnetic response body and the output coil may be relatively movable along a track on an arc.

With such a configuration, even when the magnetic response body and the output coil relatively rotate, the relative rotational movement distance can be measured, and the rotational angle and the inclination angle can also be measured. A position detection device can be realized.

For the sake of readability, in the present specification, "monotonically increasing" or "monotonously decreasing" means the mathematical terms "narrow monotonous increase" or "narrow monotonous decrease", and always refers to the distance. It means increasing or decreasing, which means that it does not have the same value for different distances, and specifically means that the derivative of the function with respect to distance always has a positive value or a negative value.
Also, "monotonously increasing or monotonically decreasing" may be referred to as "monotonously changing" for the sake of simplicity.

According to the present invention, it is possible to provide the absolute position of the detection object over a wide range with less influence of disturbance.

FIG. 2 is a cross-sectional view of the position detection device in the first embodiment. The equivalent circuit schematic of a position detection apparatus. The graph which shows the relative movement distance dependence of the output voltage of a reference coil and an output coil. FIG. 2 is a cross-sectional view of the position detection device in the first embodiment. FIG. 7A is a perspective view showing a shape of a magnetic response body in Embodiment 2; FIG. 7 is a cross-sectional view showing the shape of the magnetic response body in Embodiment 2. Sectional drawing of the position detection apparatus in Embodiment 3. FIG. The top view and sectional drawing of the position detection apparatus in Embodiment 4. FIG. Sectional drawing of the position detection apparatus in Embodiment 5. FIG. The graph which shows the temperature dependence of output voltage Vout. Sectional drawing of the position detection apparatus in Embodiment 6. FIG. Sectional drawing of the position detection apparatus in Embodiment 7. FIG. Sectional drawing of the position detection apparatus in Embodiment 7. FIG. Sectional drawing of the position detection apparatus in Embodiment 8. FIG. Sectional drawing of the position detection apparatus in Embodiment 9. FIG. Sectional drawing of the position detection apparatus in Embodiment 10. FIG. The top view and sectional drawing of the position detection apparatus in Embodiment 11. FIG. 11 is a modification of the fourth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, none of the following embodiments gives a limited interpretation in recognizing the gist of the present invention. In addition, the same or similar members may be denoted by the same reference numerals and descriptions thereof may be omitted.

(Embodiment 1)
FIG. 1 schematically shows a cross section of a position detection device 1 according to a first embodiment of the present invention.
The position detection device 1 includes, for example, a magnetic response body 2 which is a cylindrical conductive member made of a conductor such as copper, and a support member 3 which is separated from the magnetic response body 2 and is independent.

The support member 3 may be made of, for example, an insulator such as ceramic or resin, but may be made of the same material as the magnetic response body 2 in a cylindrical shape.
A first coil set consisting of a first excitation coil 4 and a reference coil 5 is installed outside the support member 3, the first excitation coil 4 and the reference coil 5 are connected, and the positional relationship between the two is established. Is fixed. Accordingly, the support member 3 has a function of supporting the first coil set. However, when the support member 3 is formed of a cylinder (pipe) of the same material as the magnetic response body 2, the support member 3 also functions as a magnetic core.

When an alternating voltage is applied to the first exciting coil 4, a magnetic flux is generated, and the magnetic flux penetrates the reference coil 5 to generate an induced electromotive force. At this time, since a part of the magnetic flux intrudes into the support member 3, the electromagnetic characteristics (material, shape, etc.) of the support member 3 determine the mutual inductance value of the first excitation coil 4 and the reference coil 5. It will be. The positional relationship between the support member 3 and the first coil set is fixed, and as a result, the mutual inductance value of the first excitation coil 4 and the reference coil 5 becomes constant.

In the present specification, “magnetic core” has a broad meaning disposed inside or outside of a coil in order to electromagnetically influence the magnetic flux generated by the coil and to determine the inductance value of the coil, For example, the present invention is not limited to a narrow sense magnetic core such as a ferromagnetic body disposed inside a coil. Also, “determining the mutual inductance value” means one of the factors determining the mutual inductance value, and does not mean the sole factor determining the inductance value.

A second coil set consisting of the second excitation coil 6 and the output coil 7 is installed outside the magnetic response body 2. The second excitation coil 6 and the output coil 7 are connected, and the positional relationship between the two is fixed. Therefore, the magnetic response body 2 is configured to function as a magnetic core of the second coil set.
The first exciting coil 4 and the second exciting coil 6 themselves are coils of the same configuration, and have the same electromagnetic characteristics. For example, the same electromagnetic lines can be obtained by rotating the same conductive wire, for example, copper wires of the same diameter and the same material, in the same geometrical shape (the diameter and length of the cylinder are the same) and the same several times. It can have characteristics.
Similarly, the reference coil 5 and the output coil 7 themselves are coils of the same configuration, and have the same electromagnetic characteristics.

The magnetic response body 2 and the second coil set are disposed so as to be relatively movable. The second excitation coil 6 and the output coil 7 are each formed of a cylindrical coil having the same axis, and the second excitation coil 6 and the output coil 7 are connected to form a second coil set. The center axis of the cylinder of the magnetic response body 2 and the axis of the second coil set are made to coincide, and the second coil set is installed independently without coupling and fixing to the magnetic response body 2, and the axis along the axis It can be arranged movably in the direction (direction along the X axis in the figure).

For example, the positions of the second excitation coil 6 and the output coil 7 are fixed, the target for detecting the position (displacement) is fixed (connected) to the magnetic response body 2, and the magnetic response body 2 is moved along with the movement of the target Configure to In this case, the second coil set and the first coil set (and the support member 3) are spaced apart and connected by a predetermined distance, and the positional relationship (distance) between the two coil sets is fixed.

Alternatively, for example, the magnetic response body 2 is separated by a predetermined distance and coupled with the first coil set to fix the position, and the second coil set is made independent of the magnetic response body 2 to detect the position (displacement) The target to be fixed may be fixed to the second coil set, and the second coil set may be moved along with the movement of the target. In this case, the positional relationship between the magnetic response body 2 and the first coil set (and the support member 3) is fixed.

In any configuration, the second coil set and the magnetic response body 2 can be moved relative to each other, and the entire range of relative movement distance (hereinafter sometimes referred to as relative movement distance) is measured. It becomes possible range.
For example, the magnetic response body 2 or the second coil set is slidably supported by a bearing or the like (not shown) to keep the distance between the central axis of the cylinder of the magnetic response body 2 and the second coil set constant. However, they can move relative to each other in the longitudinal direction (direction along the X axis in the drawing).

FIG. 1B is a cross-sectional view of the magnetic response body 2 taken along the line AA 'in FIG. 1A (in the direction perpendicular to the X axis in the figure), and the magnetic response body 2 has a cross-sectional thickness (thickness) Make a cylindrical shape of t). As shown in FIG. 1A, the cross-sectional thickness t changes along the X axis in the drawing and monotonously increases or decreases. Although FIG. 1A shows an example in which the cross-sectional thickness t monotonously increases from the bottom to the top, it may be monotonically decreasing.
That is, the cross-sectional thickness t is a function of the distance x in the direction along the X axis in the figure, for example, with the end O of the magnetic response body 2 (the end closest to the first coil set) as the origin The derivative of t to x is always set to be either positive or negative.

The magnetic response body 2 is composed of a conductor of non-ferromagnetic material, for example, a conductor such as copper or aluminum (preferably, a good conductor having a resistivity of 10 ⁻⁷ Ωm or less). Since the cross-sectional area (hereinafter simply referred to as the cross-sectional area) of the magnetic response body 2 in the direction perpendicular to the X-axis in the figure (hereinafter simply referred to as the cross-sectional area) monotonously increases or monotonously along the X axis Do.
When an alternating voltage is applied to the second exciting coil 6, a magnetic flux is generated, and the magnetic flux penetrates the output coil 7 to generate an induced electromotive force. At this time, since a part of the magnetic flux intrudes into the adjacent magnetic response body 2, the output coil 7 is electromagnetically induced by the second excitation coil 6 through the magnetic response body 2.
In the present specification, “adjacent” means disposed in line with each other (adjacent to each other) in a direction perpendicular to the X axis (relative movement direction) in the drawing. When the second coil set and the magnetic response body 2 are adjacent to each other, the magnetic flux generated by the second excitation coil 6 intrudes into the magnetic response body 2 and an eddy current is generated. The mutual inductance value of the coil set is determined. As shown in FIG. 1, in the range from O to P (the point at which the relative movement distance to the first coil set is the shortest in the second coil set), while the output coil 7 and the magnetic response body 2 are adjacent, relative It is movable to Also in the following embodiments, the second coil set and the magnetic response body 2 are disposed adjacent to each other.

Since the magnetic response body 2 is a conductor, an eddy current is generated in the direction to cancel the magnetic flux, so the voltage induced in the output coil 7 is reduced. That is, the presence of the magnetic response body 2 generates an eddy current loss, and the mutual inductance value of the second excitation coil 6 and the output coil 7 decreases. Therefore, the magnetic response body 2 determines the inductance value.

As the eddy current generated in the magnetic response body 2 increases, the eddy current loss increases, and the mutual inductance value between the second excitation coil 6 and the output coil 7 decreases. When the cross-sectional thickness t of the magnetic response body 2 monotonously increases along the X-axis direction in the figure, the electrical resistance monotonously decreases, and the cross-sectional thickness t of the magnetic response body 2 in the X-axis direction in the figure When monotonically decreasing along, the electrical resistance monotonously increases.

Magnetic response body 2 may have a configuration including a conductive member whose electric resistance monotonously increases or monotonously along the X-axis direction in the figure, and the inside of the cylindrical conductive member as shown in FIG. For example, an insulator may be further provided for protection or reinforcement (for enhancing the rigidity), and a coating layer such as a resin for protection or friction reduction may be provided on the outside of the cylindrical conductive member, for example. You may have.

Note that the support member 3 is fixed without being separated from and adjacent to the magnetic response body 2, and even if the magnetic response body 2 and the second coil set move relatively, The positional relationship with the first coil set does not change (is fixed).

FIG. 2 shows an equivalent circuit of the position detection device 1.
The first excitation coil 4 and the second excitation coil 6 are connected in parallel to a single AC power supply 8, and the same AC voltage is applied.
An induced electromotive force is generated in the reference coil 5 and the output coil 7 by the first excitation coil 4 and the second excitation coil 6 to which the same AC voltage is applied.

On the other hand, the reference coil 5 and the output coil 7 are differentially connected, and the outputs of the reference coil 5 and the output coil 7 are connected to the output terminal 9a and the output terminal 9b.
As a result, an output voltage Vout equal to the difference between the voltage of the reference coil 5 generated by electromagnetic induction and the voltage of the output coil 7 is output between the output terminal 9a and the output terminal 9b.
As described in detail below, with reference to the voltage of the reference coil 5, the amount of change in voltage depending on the position of the voltage of the output coil 7 is output as the output voltage Vout. Since the output voltage of the reference coil 5 is used as a reference, the amount of change with respect to the relative movement distance of the output voltage Vout is large compared to the differential voltage of the output coil disclosed in

Patent Documents

1 and 2, and position detection sensitivity Can be improved.

The electrical connection shown in the equivalent circuit may be made by a normal electric wire. Because the distance between the first and second sets of coils is fixed, placement of the wires is easy.

The mutual inductance value between the second excitation coil 6 and the output coil 7 changes depending on the relative position (relative movement distance) between the second coil set and the magnetic response body 2. Therefore, the voltage induced in the output coil 7 changes depending on the relative position of the second coil set and the magnetic response body 2.
On the other hand, the first coil set and the magnetic response body 2 are always separated (that is, they are not adjacent), and the mutual inductance value of the first excitation coil 4 and the reference coil 5 is the second coil. The voltage induced in the reference coil 5 is constant because it is constant independently of the relative distance between the set and the magnetic response body 2. As a result, the output voltage Vout changes depending on the relative position of the second coil set and the magnetic response body 2. That is, the output voltage Vout is a function of the distance in the X-axis direction shown in FIG. 1A, and monotonously increases or decreases with the distance.
Therefore, the relative position between the second coil set and the magnetic response body 2 can be uniquely determined from the output voltage Vout. Furthermore, since the mutual inductance value changes with the shape change of the magnetic response body 2, the entire range in which the magnetic response body 2 has the shape change adjacent to the second coil set (the range from O to P in FIG. 1) The position detection is possible over a wide range. That is, it is possible to detect an absolute position (absolute position with O on the X axis in the figure as an origin) within the range where position detection is possible.

FIG. 3 is a graph for explaining the detection principle of the position detection device 1 and shows the relative movement distance dependency of the output voltage of the reference coil 5 and the output coil 7.
As the relative positional relationship between the magnetic response body 2 and the second coil set is shown at the bottom of the graph of FIG. 3, the graph shows that the end of the magnetic response body 2 is from O to P on the X axis. The output voltage of reference coil 5 and output coil 7 at the time of moving relatively is shown. Here, an alternating voltage of the same constant voltage is applied to the first excitation coil 4 and the second excitation coil 6.

As shown in FIG. 3, the output voltage of the reference coil 5 exhibits a constant value, but the output coil 7 monotonously changes in accordance with the relative movement distance. This is because the electrical resistance of the magnetic response body 2 changes monotonously depending on the relative movement distance, and the mutual inductance value of the second coil set changes monotonously. Thus, it can be confirmed by monotonously changing the voltage of the output coil 7 that the mutual inductance value of the second coil set changes monotonously.
Further, since the first coil set is disposed so as to be separated from (not adjacent to) the magnetic response body 2, the output voltage of the reference coil 5 exhibits a constant value. The fact that the output voltage of the reference coil 4 is constant when an alternating voltage is applied to the first excitation coil 4 regardless of the relative movement distance between the magnetic response member 2 and the output coil 7 is that in the first coil set. It means that the mutual inductance value is constant.

When the support member 3 is formed of a cylinder (pipe) made of the same material as the magnetic response body 2 and has the same sectional thickness as a specific part of the magnetic response body 2, for example, the center, the second coil set is When located at the center of the magnetic response body 2, the output voltage Vout is 0 (zero). By adjusting the cross-sectional thickness of the support member 3, it is possible to appropriately set the position (reference point) at which the output voltage Vout is 0 (zero). In addition, the support member 3 may be made of another conductive material that can cause eddy current loss at a specific location of the magnetic response body 2.
Strictly speaking, since the cross-sectional thickness of the magnetic response body 2 changes monotonously, the cross-sectional thickness also changes in the range reached by the magnetic field generated by the second excitation coil. If it is constant, the output voltage Vout at a particular point may not be exactly 0 (zero). In this case, the cross-sectional thickness of the support member 3 can be finely adjusted to make the output voltage Vout 0 (zero), or the cross-sectional thickness of the support member 3 is monotonously changed in the same manner as the magnetic response body 2 It is also good.

When measuring the position (displacement) of the object to be measured, it is necessary to detect the amount of change of the output voltage Vout by an electronic circuit. Therefore, the reference point is set in the range where the position can be measured, and the output voltage Vout outputs only the change of the voltage corresponding to the displacement of the measuring object (eliminating an unnecessary voltage offset that does not contribute to the position detection). The detection sensitivity of the electronic circuit to the amount of voltage change can be improved.

The relative position (or the position (displacement) of the object to be measured) appropriately amplifies the output voltage Vout by an amplifier circuit, and the correlation between the output voltage Vout and the relative position by an arithmetic processing circuit built in (or externally attached) to the position detection device 1 It can be calculated from the relationship.
Therefore, the correlation data between the output voltage Vout and the relative position is acquired in advance, and the correlation data is stored in a storage device built in (or externally attached to) the position detection device 1. By comparing, the output voltage Vout can be converted into relative position information.

The spatial resolution of the relative position depends on the performance (S / N ratio etc.) of the amplification circuit, but in order to improve the S / N ratio, it is important to increase the voltage change amount of the output voltage Vout.
Therefore, while making the winding ratio of the first excitation coil 4 and the reference coil 5 and the winding ratio of the second excitation coil 6 and the output coil 7 the same, the voltage change amount of the output voltage Vout is 200 mV or more Adjust to become Specifically, the winding ratio of the reference coil 5 to the first excitation coil 4 ([the number of turns of the electric wire of the reference coil 5] / [the number of turns of the first excitation coil 4]) and the second excitation coil 6 By making the winding ratio of the output coil 7 ([the number of turns of the electric wire of the output coil 7] / [the number of turns of the second excitation coil 6]) equal to The voltage induced electromagnetically in the coil 7 can be increased, and the winding ratio may be set so that the voltage change amount of the output voltage Vout is 200 mV or more. As a result, S / N ratio is improved, position detection with high spatial resolution (miniaturizing detectable minimum displacement) becomes possible, and high S / N ratio and high amplification factor with respect to the performance of the amplification circuit. There is no need to make a request, and the burden on the electronic circuit is also reduced.

The output voltage Vout of the position detection device 1 is highly resistant to noise, and has less fluctuation with respect to environmental changes. As shown in FIG. 2, an alternating current voltage (for example, a sine wave) is applied to the first excitation coil 4 and the second excitation coil 6 by the same alternating current power supply 8. Therefore, the same voltage fluctuation is applied to the first excitation coil 4 and the second excitation coil 6 even when an undesired voltage change occurs due to noise caused by noise for some reason. Be done. Therefore, a voltage fluctuation corresponding to that is induced in the reference coil 5 and the output coil 7.
Also in this case, since the output voltage Vout is the difference between the voltage of the reference coil 5 and the voltage of the output coil 7, the voltage fluctuations of the reference coil 5 and the output coil 7 are offset.

In addition, when the resistances of the wires constituting each of the first excitation coil 4, the second excitation coil 6, the reference coil 5 and the output coil 7 change according to the environmental temperature, the voltage of the reference coil 5 due to the resistance change And the voltage of the output coil 7 fluctuate. However, since the difference between the voltage of the reference coil 5 and the voltage of the output coil 7 is output, the voltage fluctuation is canceled.

As described above, by utilizing the output voltage of the reference coil 5 as the reference voltage, it is possible to offset the influence of disturbance such as noise without reducing the output voltage Vout.
As a result, the relative position between the second coil set and the magnetic response body 2 can be detected with high reliability.

In addition, although the magnetic response body 2 is constituted by a cylindrical shape in which the cross-sectional thickness t changes, as shown in FIGS. 4A and 4B, the diameter increases or monotonously along the X axis direction. It may be configured with a decreasing frusto-conical shape. In this case, the support member 3 may be an insulator, but may be a conductive material similar to the magnetic response body 2 and may have the same cross-sectional area as a specific portion of the magnetic response body 2.
By making the magnetic response body 2 into a rotationally symmetric shape with respect to the X axis like a cylindrical shape or a truncated cone shape, control of the cross-sectional area of the cross section cut perpendicular to the X axis is easy by cutting It also has good consistency with general coil shapes.

The detection principle of the position detection device 1 is that while the mutual inductance value of the second coil set via the magnetic response body 2 monotonously increases or decreases monotonously along the X-axis direction, the mutual detection of the first coil set The absolute position is detected by the differential voltage between the reference coil 5 and the output coil 7 by a configuration in which the inductance value is fixed.

Second Embodiment
In the first embodiment, by changing the cross-sectional thickness of the magnetic response body 2, the cross-sectional area is changed according to the relative position with the second coil set.
In the present embodiment, in order to change the cross-sectional area of the magnetic response body 2, an opening is provided on the side wall surface of a cylinder having _a constant cross-sectional thickness (ta), and the cross-sectional area is controlled by the area of the opening. A second magnetic response body 2a (second conductor) of a cylindrical shape (without an opening) having a constant cross-sectional thickness (t _b ) By combining them, the magnetic response body 2 is configured, and the cross-sectional area of the magnetic response body 2 is changed according to the relative position with the second coil set.
The materials of the first conductor that is the first magnetic response body 2a that constitutes the magnetic response body 2 and the second conductor that is the second magnetic response body 2b are the same as the magnetic response body 2 of the first embodiment. However, the same material or different materials may be used.

Fig.5 (a) is a perspective view which shows the shape of the magnetic response body 2 concerning Embodiment 2, FIG.5 (b) and FIG.5 (c) are a cross section AA 'and a cross section BB'. Show the shape of
As shown in FIG. 5 (a), the magnetic response body 2 has a first magnetic response body 2a having an opening 10 at its side wall surface, and a cylindrical second magnetic response body 2b having no opening. The first magnetic response body 2a and the second magnetic response body 2b are in contact with each other at their side faces.
That is, as shown in FIGS. 5 (b) and 5 (c), the inner wall surface of the first magnetic response body 2a and the outer wall surface of the second magnetic response body 2b are in contact with each other and are electrically connected. . By substantially matching the inner diameter of the first magnetic response body 2a with the outer diameter of the second magnetic response body 2b, the inner wall surface of the first magnetic response body 2a and the outer surface of the second magnetic response body 2b It can be in contact with the wall surface.
Needless to say, that the inner diameter of the first magnetic response body 2a and the outer diameter of the second magnetic response body 2b match means that they match in the range of machining accuracy.

The shape of the opening 10 changes depending on the positions of the second coil set and the first magnetic response body 2a, and the opening area of the opening 10 is the second coil set and the first magnetic response body 2a. The shape has a monotonously increasing or monotonously decreasing shape with respect to the relative movement distance of.

For example, as shown in FIGS. 5B and 5B, the opening 10 is provided in a circular arc region of the angle (central angle) θ, and the value of the angle θ is along the X axis in the drawing. Depending on the position of the direction, it may increase or decrease monotonously. Specifically, the angle θ is a function of the distance x in the X-axis direction in the figure with the one end O of the opening 10 of the first magnetic response body 2a as the origin, and θ is monotonously with respect to x To increase or decrease monotonically, the derivative for x can always be set to be either positive or always negative. For example, the angle θ is a linear function of x, and the coefficient of x is either positive or negative. The cross-sectional area of the opening 10 is proportional to θ. Therefore, the cross-sectional area of the first magnetic response body 2a is proportional to 2π-θ.

With such a configuration, the magnetic response body 2 has _a groove with _a depth of ta at the location where the opening 10 exists in the conductor having _a cross-sectional thickness of t _a + t _b . Since the cross-sectional thickness t _b of the second magnetic response body 2 _b is greater than 0, the depth t _a is smaller than the cross-sectional thickness t _a + t _b .
As a result, the thickness of the magnetic response body 2 is reduced in the opening 10 or the groove, and the electrical resistance is increased. Since the area (groove) of the opening 10 monotonously increases or decreases monotonously depending on the position in the direction along the X axis in the drawing, the electric resistance of the magnetic response body 2 is the area where the opening 10 exists. , Monotonously increasing or decreasing depending on the position in the direction along the X axis in the figure.
That is, the amount of change in the cross-sectional area of the magnetic response body 2 in the X-axis direction is determined by the amount of change in the cross-sectional area of the second magnetic response body 2b. Change.
Therefore, the mutual inductance value of the second coil set via the magnetic response body 2 is uniquely determined by the position in the X-axis direction.

Since the direction of the eddy current flowing in the magnetic response body 2 is circumferential, in the region where the opening 10 of the first magnetic response body 2 a exists, eddy current flows in the second magnetic response body 2 b. Become. The detection sensitivity can be adjusted by optimizing t _a and t _b appropriately.
The cross-sectional thickness of the first magnetic response member 2a and (t _a) and the cross-sectional thickness of the second magnetic response member 2a (t _b), even with the same thickness, may be different.

Further, for stabilization of the electrical resistance at the contact interface between the inner wall surface of the first magnetic response body 2a and the outer wall surface of the second magnetic response body 2b, the inner wall surface of the first magnetic response body 2a and the second wall A conductive substance may be interposed between the magnetic response body 2b and the outer wall surface by plating or conductive paste.
In FIGS. 5B and 5C, although the second magnetic response body 2b is provided inside the first magnetic response body 2a, the second magnetic response body 2a is provided outside the first magnetic response body 2a. The response body 2b may be provided, and the outer wall surface of the first magnetic response body 2a and the inner wall surface of the second magnetic response body 2b may be in contact with each other. (See Figure 6 (d).)

In FIG. 5, although one opening 10 is provided on the side wall of the first magnetic response body 2a, as shown in FIGS. 6 (a), (b) and (c), a plurality of openings 10 are provided. You may provide. That is, the magnetic response body 2 may be provided with a plurality of grooves.
In particular, as shown in FIGS. 6 (a) and 6 (c), by arranging the opening 10 axially symmetrically on the side wall of the first magnetic response body 2a, the magnetic response body relative to the second coil set is obtained. Even when the position 2 moves in the direction perpendicular to the X-axis direction in FIG. 5, the effect that the potential induced in the output coil 7 can be stabilized can be obtained.

For example, in FIGS. 6A and 6C, when the magnetic response body 2 is moved in the direction along the Y axis in the drawing, for example, in the right direction in the drawing, the right side surface portion of the magnetic response body 2 is the second coil As the pair approaches, the left side of the magnetic response body 2 moves away from the second coil pair. The right side portion of the magnetic response body 2 has an increased eddy current loss, but the left side portion has a reduced eddy current loss. As a result, the eddy current losses of the entire magnetic response body 2 are averaged.
On the other hand, in FIG. 6B, since the openings 10 are not arranged in axial symmetry, eddy current loss increases on the right side of the magnetic response body 2, but the magnetic response body 2 does not exist on the left side. Therefore, the reduction effect of the eddy current loss in the left side surface portion can not be obtained, and the eddy current losses are not averaged.

Therefore, as shown in FIGS. 6A and 6C, by arranging the openings 10 in axial symmetry, the position of the magnetic response body 2 fluctuates in the direction perpendicular to the X-axis direction due to vibration or the like. Even then, stable output voltage can be obtained.
The other configuration is the same as that of the first embodiment.
Also, as shown in FIGS. 6A, 6B, and 6C, even when the first magnetic response body 2a has a plurality of openings 10, as in FIG. The second magnetic response body 2b may be provided outside the magnetic response body 2a.

The first magnetic response body 2a of the present embodiment prepares a pipe of a cylindrical conductor having a constant cross-sectional thickness, and cuts a part of the side surface in a diagonal direction to obtain a desired opening. 10 can be formed, and as a result, there is an advantage that the magnetic response body 2 in which the cross-sectional area increases or decreases monotonously can be easily manufactured (implemented).

In addition, since the cross-sectional area (or electric resistance) of the magnetic response body 2 is monotonously changed by comprising the first magnetic response body 2a provided with the opening and the second magnetic response body 2b. The region of the magnetic response body 2 that enables position detection is precisely defined in the range of the region where the opening of the first magnetic response body 2a is formed.

In the present embodiment, the magnetic response body 2 is provided with one or more grooves having _a constant depth ta, and the width of the grooves changes monotonously with the relative movement distance between the magnetic response body 2 and the second coil set. An example is shown, but one or more grooves having a constant width are provided on the side wall surface of the magnetic response body 2, and the depth t _{a of the} grooves is monotonously changed along with the relative movement distance with the second coil set. May be For example, the side wall surface of the cylindrical conductor may be cut to form a groove of varying depth. Also, both the width and the depth of the groove may be monotonously changed.
By changing the cross-sectional area of the groove (that is, the product of “depth” and “width”) monotonously with the change in the relative position between the magnetic response body 2 and the second coil set, in any case, The cross-sectional area of the response body 2 can be monotonously changed with the relative movement distance between the magnetic response body 2 and the second coil set.
It is needless to say that the depth of the groove is smaller than the cross-sectional thickness (thickness) of the magnetic response body 2 in the portion without the groove.

(Embodiment 3)
Although FIG. 1 shows an example in which the second coil set (the second excitation coil 6 and the output coil 7) is installed outside the magnetic response body 2, it may be installed inside the magnetic response body 2 .
In the present embodiment, as shown in FIG. 7, the magnetic response body 2 is constituted by a cylindrical conductive member whose cross-sectional thickness monotonously increases or decreases monotonically along the X-axis direction in the drawing, The second excitation coil 6 and the output coil 7 are disposed inside the magnetic response body 2.

Although the first excitation coil 4 and the reference coil 5 are disposed inside the cylindrical support member 3, as shown in FIG. 1, the first excitation coil 4 and the reference coil 5 may be installed outside the cylindrical support member 3.
When the cylindrical support member 3 is used, the cylindrical support member 3 is made of, for example, the same material as the magnetic response body 2 and configured to have the same cross-sectional thickness as the cross-sectional thickness of the central portion of the magnetic response body 2 The air gap between the first excitation coil 4, the reference coil 5 and the inner surface of the support member 3 may be made of an insulating resin or the like. The support member 3 may function as a magnetic core, and the output voltage Vout may be set to 0 (zero) when the second coil set is positioned at the central portion of the magnetic response body 2.
The other configuration is the same as that of the first embodiment.

In the magnetic response body 2, the cross-sectional thickness monotonously increases or monotonically decreases along the X-axis direction in the drawing, so that the eddy current loss monotonously decreases or monotonously. As a result, the mutual inductance value of the second excitation coil 6 and the output coil 7 is uniquely determined depending on the relative movement distance between the second coil set and the magnetic response body 2, and the relative movement distance It becomes possible to detect the relative position).

(Embodiment 4)
In order to change the mutual inductance value of the second coil set through the magnetic response body 2 monotonically, the magnetic response body 2 is made of a trapezoidal ferromagnetic material having a cross-sectional thickness of t, such as permalloy, ferrite, iron, etc. It may be configured by (Figure 8)

FIG. 8A is a top view showing the main part of the position detection device 1 of the present embodiment. As shown in FIG. 8A, the magnetic response body 2 made of a ferromagnetic material is configured such that the width w monotonously changes from O to P along the X-axis direction.
FIG. 8B is an enlarged view of the AA ′ cross section of FIG. 8A. The second coil set is disposed perpendicular to the magnetic response body 2, and specifically, as shown in FIG. 8 (b), the second excitation coil 6 and the output coil which are the second coil set. The winding axis of 7 is disposed perpendicular to the width direction of the magnetic response body 2. The winding axes of the second excitation coil 6 and the output coil 7 are the same, and the output coil 7 is provided outside the second excitation coil 6.

Also, a reference body 12 is provided so as to be isolated from the magnetic response body 2. FIG. 8C is an enlarged view of the B-B ′ cross section of FIG. 8A. The first coil set is disposed perpendicularly to the reference body 12, and specifically, as shown in FIG. 8 (c), the first exciting coil 4 and the reference coil 5 which are the first coil set. The winding axis of is disposed perpendicular to the width direction of the reference body 12. The winding axes of the first exciting coil 4 and the reference coil 5 are the same, and the reference coil 5 is provided outside the first exciting coil 4.

The reference body 12 corresponds to the support member 3 in FIG. 1, but the mutual inductance value of the first coil set (the first excitation coil 4 and the reference coil 5) is determined through the reference body 12.
The material and thickness t of the reference body 12 are the same as the magnetic response body 2, and the width w is the same as the width of a specific reference point of the magnetic response body 2, for example, the O point.

As in the other embodiments, the first excitation coil 4 and the second excitation coil 6 have the same electrical characteristics, and the reference coil 5 and the output coil 7 have the same electrical characteristics. When the same AC voltage is applied to the coil 4 and the second excitation coil 6, the output voltage of the output coil 7 and that of the reference coil 5 at the reference point, for example, point O coincide with each other, and the differential voltage between both coils is 0 ( It becomes zero. Furthermore, since the electromagnetic characteristics of the reference body 12 and the magnetic response body 2 that determine the mutual inductance value of the first coil set and the second coil set are the same, the temperature characteristics of the output voltage of the output coil 7 and the reference coil 5 are also Since they coincide with each other, it is possible to suppress the temperature change of the "difference in output voltage" of both coils.

Since the width of the magnetic response body 2 changes monotonously along the X-axis direction, strictly speaking, the width of the magnetic response body 2 changes in the area covered by the magnetic field of the second coil set. If the width of 12 is constant, the mutual inductance values of the second coil set and the first coil set will not match exactly. However, by adjusting the width of the reference body 12, it is possible to easily match the mutual inductance values of the second coil set and the first coil set. Alternatively, the output voltage of the output coil 7 and that of the reference coil 5 may be matched by changing the width of the reference body 12 monotonously as the width of the magnetic response body 2.

As in the other embodiments, the magnetic response body 2 and the second coil set are relatively movable in the X-axis direction, and the width w of the magnetic response body 2 which is a ferromagnetic body is along the relative movement direction. It monotonously increases or decreases. Since the magnetic flux generated by the second excitation coil 6 and penetrating through the magnetic response body 2 changes with the width w of the magnetic response body 2, the mutual inductance value of the second coil set monotonously increases along the relative movement direction Or decrease.
As a result, based on the difference between the output voltage of the output coil 7 and the reference coil 5, the position along the relative moving direction of the magnetic response body 2 and the second coil set can be uniquely detected.

The arrangement relationship between the first excitation coil 4 and the reference coil 5 and between the second excitation coil 6 and the output coil 7 is not limited to that shown in FIGS. 8B and 8C, and can be changed as appropriate. For example, as shown in FIGS. 8D and 8E, the winding axes of the first excitation coil 4 and the reference coil 5 are the same, and the reference coil 5 is used as a reference body with respect to the first excitation coil 4. The winding axes of the second excitation coil 6 and the output coil 7 may be the same, and the output coil 7 may be far from the magnetic response body 2 with respect to the second excitation coil 6. You may distribute it.
Since the area of the area where the first coil set and the reference body 12 face each other and the area where the second coil set and the magnetic response body 2 face each other is reduced, the spatial resolution of position detection can be improved.

Further, as shown in FIGS. 8 (f) and 8 (g), the magnetic response body 2 is constituted by two opposing parallel flat plates, and the second three exciting coils 6 and the two output coils 7 are opposed to each other. Between the magnetic response body 2c and the fourth magnetic response body 2d, the reference body 12 is composed of two opposing parallel flat plates, and the first exciting coil 4 and the reference coil 5 are two opposing first ones. The second reference body 12b may be placed between the second reference body 12b and the second reference body 12b.

Also, even if the ferromagnetic material constituting the magnetic response body 2, the third magnetic response body 2c, the fourth magnetic response body 2d, the reference body 12, the first reference body 12a and the second reference body 12b is amorphous. Good. By making the ferromagnetic substance amorphous, the output voltages of the output coil 7 and the reference coil 5 can be increased several times, and the position detection sensitivity can be improved.

(Modification)
Although each example of FIG. 8 shows an example in which the axis of the coil is disposed perpendicularly to the surface of the thin plate of the magnetic response body 2 which is a ferromagnetic body, as shown in FIGS. 18 (a) and 18 (b), The arrangement of the coils may be arranged to be arranged as in FIG. In this case, the cross-sectional shape of the ferromagnetic material is not a truncated cone as shown in FIG. 4 but a tapered shape having a rectangular cross section with a width w and a thickness t as shown in FIGS. It is a thin plate shaped like a trapezoid in plan view, which monotonously increases or monotonously decreases along the axial direction, and is configured such that the ferromagnetic material passes through the coil. With such a configuration, a very large output was obtained. This is considered to be due to the effect of the edge. Further, as shown in FIGS. 18 (a) and 18 (b) rather than the truncated cone shape as shown in FIG. There is also an advantage that it is easy to manufacture. Furthermore, in the case of a thin plate, it is considered that there is a merit that it is also possible to attach it to a flexible structure and measure the movement of a curve.

Embodiment 5
Since the reference coil 5 and the output coil 7 are differentially connected, the influence of noise is canceled out, and the change in the electric characteristics of the coil itself due to the temperature change, for example, the change in induced electromotive force due to the increase in resistance of the wire constituting the coil Can be offset.
However, since the electrical resistance of the magnetic response body 2 also depends on temperature, the eddy current loss by the magnetic response body 2 depends on temperature. For example, when the electrical resistance of the magnetic response body 2 increases due to temperature rise, the eddy current loss decreases. Therefore, the mutual inductance value of the second excitation coil 6 and the output coil 7 via the magnetic response body 2 depends on the temperature. Furthermore, the cross-sectional area of the magnetic response body 2 changes with positions. As a result, the temperature change of the mutual inductance value is strictly dependent on the position.

Although the temperature dependency of the eddy current loss can be offset by using the support member 3 of the first coil set as a magnetic core and using the same material as the magnetic response body 2, the “position of the mutual inductance value of the second coil set is It is difficult to completely offset the dependent environmental temperature change, which can affect the accuracy of position detection.
The present embodiment can further reduce the change in position detection accuracy due to temperature by further reducing the temperature dependency of the output voltage, and can provide the position detection device 1 with higher accuracy.

FIG. 9 is a cross-sectional view of the position detection device 1 according to the fourth embodiment.
As shown in FIG. 9, in the present embodiment, the magnetic response body 20 is the same as the magnetic response body 2 of the first embodiment, and is a first conductive member made of a conductor such as copper or aluminum, which has a cylindrical shape. 21 and a first ferromagnetic member 22 such as cylindrical permalloy, ferrite, iron or the like.

In the example shown in FIG. 9, the first ferromagnetic member 22 is installed inside the first conductive member 21, and the first conductive member 21 and the first ferromagnetic member 22 are connected. , The mutual positional relationship is fixed.
The cross-sectional thickness of the first conductive member 21 monotonously increases or decreases along the X-axis direction in the figure as in the first embodiment.

The position detection device 1 includes a support member 30, which is separated from the magnetic response body 20 and is independent.
The support member 30 includes a cylindrical second conductive member 31 made of a conductor such as copper or aluminum, and a second ferromagnetic member 32 made of a cylindrical permalloy, ferrite, iron or other ferromagnetic material. It consists of The second ferromagnetic member 32 is installed inside the second conductive member 31.
A second coil set (the second excitation coil 6 and the output coil 7) is disposed relatively movably outside the magnetic response body 20, and a first coil set (a first coil set) is provided outside the support member 30. The exciting coil 4 and the reference coil 5) are fixed and disposed.

FIG. 10 shows the induced electromotive force (black circle in the figure) of the combination of the second excitation coil 6 and the output coil 7 (corresponding to FIG. 9) having a magnetic core with a structure having a ferromagnetic member inside the conductive member; The temperature dependency of the induced electromotive force (white circles in the figure) of the combination of the second excitation coil 6 and the output coil 7 (corresponding to FIG. 1) having a structure without a ferromagnetic member as an inner core is shown in comparison.
FIG. 10 shows the difference between the output voltage and the reference voltage at each temperature of 10 ° C. to 70 ° C., using the voltage (output voltage) of the output coil at a temperature of 10 ° C. as a reference voltage.

From FIG. 10, when the ferromagnetic member is inside the conductive member (black circle in the figure), the temperature fluctuation of the output voltage is greater than in the case where the ferromagnetic member is not inside the conductive member (white circle in the diagram) I can understand that it is small. Thus, the temperature dependency can be reduced by combining the conductive member, which is a conductor, and the ferromagnetic member, which is a ferromagnetic material.

Generally, the permeability of the first ferromagnetic member 22 depends on temperature, and below the Curie temperature, the permeability increases with the temperature rise. The reduction effect of the output voltage on temperature change shown in FIG. 10 is presumed to be due to the difference between the temperature dependence of the magnetic permeability and the temperature dependence of the eddy current loss.
Also, the first conductive member 21 and the first ferromagnetic member 22 are independent entities, and the temperature dependency of the magnetic permeability and the temperature dependency of the eddy current loss can be controlled independently.
The configuration (shape) of the first conductive member 21 is determined for the purpose of position detection. Therefore, the first ferromagnetic member 22 is further provided, the degree of freedom for adjusting the temperature dependency is increased, and the shape of the first ferromagnetic member 22, the distance between the first conductive member 21 and the like are controlled. It is possible to further reduce the temperature dependency.

Similarly, by adopting a combination of the second conductive member 31 and the second ferromagnetic member 32 for the support member 30, the temperature dependency of the output voltage of the reference coil 5 can also be reduced. As a result, the temperature dependency of the output voltage difference between the reference coil 5 and the output coil 7 can also be reduced.

The shape of the first conductive member 21 is, for example, a cylindrical shape having a constant cross-sectional thickness as shown in FIGS. 5 and 6, and the area on the side wall surface monotonously increases or decreases depending on the position. An opening may be provided.
In this case, the first ferromagnetic member 22 may be installed inside the first conductive member 21 with the first ferromagnetic member 22 having, for example, a cylindrical shape.

The present embodiment can also be applied to the fourth embodiment shown in FIG. Magnetic response body 2, third magnetic response body 2c, fourth magnetic response body 2d, reference body 12, first reference body 12a and second reference body 12b, and a laminated structure of a ferromagnetic body and a conductor Thus, it is possible to combine the ferromagnetic material and the conductor to further reduce the temperature dependency of the output voltage difference between the reference coil 5 and the output coil 7.
Further, one of the third magnetic response body 2c and the fourth magnetic response body 2d is made of a ferromagnetic material, and the other is made of a conductor, and the first reference body 12a and the second reference are made. The temperature dependency of the output voltage difference between the reference coil 5 and the output coil 7 by combining one of the body 12b with a ferromagnetic body and the other with a conductor and combining the ferromagnetic body and a conductor Can be further reduced. Since the ferromagnetic body and the conductor exist independently, it becomes easy to adjust the shape and distance from each coil independently, and optimization for reducing the temperature dependency of the output voltage difference The degree of freedom is increased, and optimization work for reducing temperature dependency is facilitated.

Embodiment 6
In the fourth embodiment, the second coil set is arranged relatively movably outside the magnetic response body 20. However, as shown in FIG. 11, the second coil set is provided inside the magnetic response body 20. It may be arranged relatively movable.

In the present embodiment, as shown in FIG. 11, the magnetic response body 20 is composed of the first conductive member 21 and the first ferromagnetic member 22.
As in the fifth embodiment, the first conductive member 21 is formed of a cylindrical conductor such as copper or aluminum.
The first ferromagnetic member 22 is made of a ferromagnetic material such as cylindrical permalloy, ferrite, iron or the like, and is connected to the outside of the first conductive member 21 and installed, and the first conductive member 21 and the first conductive member 21 The positional relationship between the first ferromagnetic member 22 and the first ferromagnetic member 22 is fixed.

The support member 30 includes a cylindrical second conductive member 31 made of a conductor such as copper or aluminum, and a second ferromagnetic member 32 made of a cylindrical ferromagnetic permalloy such as ferrite or iron. It consists of The second ferromagnetic member 32 is installed outside the second conductive member 31, and the second conductive member 31 and the second ferromagnetic member 32 are connected (the positional relationship is fixed).

A second coil set (the second excitation coil 6 and the output coil 7) is disposed relatively movably inside the magnetic response body 20, and a first coil set (first The exciting coil 4 and the reference coil 5) are fixed and disposed.

As in the fourth embodiment, the combination of the first conductive member 21 and the first ferromagnetic member 22 and the combination of the second conductive member 31 and the second ferromagnetic member 32 make it possible to form a first coil set. And the temperature dependency of the output voltage of the second coil set can be reduced. As a result, the temperature dependency of the output voltage difference between the output coil 7 and the reference coil 5 can also be reduced, and the reliability of the position detection of the measurement object can be improved as in the fourth embodiment.

Seventh Embodiment
According to the present embodiment, it is possible to improve the spatial resolution of the position detection device 1 in a specific area (to miniaturize the separately detectable minimum moving distance).
For example, in the slide part of a press machine used for press processing, accurate control of the position of the slide is necessary in the area where pressure is applied to the workpiece from the vicinity where the mold contacts the workpiece being a workpiece The position detection accuracy of the slide position is required to be higher than that of the other slide movement area, and the spatial resolution needs to be improved.

In order to improve the spatial resolution, it is necessary to increase the change amount of the output voltage Vout with respect to the movement distance of the object whose position (displacement) is to be detected.

FIG. 12 shows a cross-sectional view of the position detection device 1 in the present embodiment.
As shown in FIG. 12, the absolute value of the amount of change (gradient) relative to the relative movement distance of the cross-sectional thickness of the magnetic response body 2 in the direction along the X axis is the region indicated by .alpha. is referred to as α), and is set to be larger than a region (hereinafter referred to as a region β) indicated by β in the drawing.
That is, the absolute value of the derivative with respect to the distance of the cross-sectional thickness is set larger in the region α than in the region β, with the cross-sectional thickness of the magnetic response body 2 as a function of the distance along the X-axis direction.
Since the cross-sectional thickness of the magnetic response body 2 monotonously increases or decreases, the derivative is always set to a positive or negative value in any region.

In the region α, when an alternating voltage is applied to the second excitation coil 6 with respect to the relative movement distance between the magnetic response body 2 and the second coil set (the second excitation coil 6 and the output coil 7) The amount of change in the eddy current of V is larger than the amount of change in the region β. Therefore, the amount of change with respect to the relative movement distance of the voltage output from the output coil 7 is larger in the region α than in the region β.
In other words, for the same amount of change in voltage output from the output coil 7, the relative movement distance becomes shorter. Therefore, in the electronic circuit, the relative movement distance corresponding to the minimum detectable voltage change can be shortened. That is, the relative movement distance which can be separately detected becomes short, and the spatial resolution is improved.

By improving the spatial resolution with respect to the relative movement distance between the magnetic responder 2 and the second coil set in all the regions, the position detection device 1 becomes larger, so by improving the spatial resolution only in the necessary region, It is possible to prevent the position detection device 1 from being enlarged.

It is needless to say that the region α for improving the spatial resolution is not limited to the position shown in FIG. 12 and can be appropriately set according to the application as shown in FIGS. 13 (a) and 13 (b). .

Moreover, it is needless to say that the form of the above-mentioned magnetic response body 2 is not limited to the above-mentioned embodiment, but is applicable also to other embodiments.
For example, in the magnetic response body 2 shown in FIG. 7, the amount of change with respect to the relative movement distance of the cross-sectional thickness (of a specific region) may be increased.
Further, as shown in FIG. 13C, the magnetic response body 2 is formed in a truncated cone shape as shown in FIG. 4, and the amount of change (gradient) with respect to the relative movement distance of the cross sectional diameter of a specific area (area α) It may be larger than the amount of change (slope) of other regions (region β).
Further, as shown in FIGS. 5 and 6, the magnetic response body 2 is formed in a cylindrical shape having the same cross-sectional thickness and having the opening 10 in the side wall surface, and the size of the opening 10 (of a specific region) The amount of change (slope) of the relative movement distance of (or angle θ) may be larger than the amount of change (slope) of other regions.
Furthermore, the present embodiment can be applied to, for example, the first conductive member 21 of the magnetic response body 20 shown in FIGS. 9 and 11, and even if the inside or the outside of the first conductive member 21 is provided with a ferromagnetic material. Good.

(Embodiment 8)
In the above embodiments, the first excitation coil 4 and the reference coil 5, and the second excitation coil 6 and the output coil 7 are both adjacent to each other along the relative movement direction of the magnetic response body 2. is there. The first excitation coil 4, the reference coil 5, the second excitation coil 6, and the output coil 7 may be arranged in a two-layer structure.

As shown in FIG. 14, the second excitation coil 6 is installed on the outer periphery of the output coil 7 or on the opposite side to the magnetic response body 2, and the outer periphery of the reference coil 5 or on the opposite side to the support member 3. The excitation coil 4 is installed.
Even in such an arrangement, since the mutual inductance value of the second excitation coil 6 and the output coil 7 monotonously increases or decreases relative to the relative movement distance, the relative movement distance is calculated from the output voltage Vout. What can be done is the same as the above embodiment.

The output coil 7 and the second excitation coil 6 have the same central axis and are stacked in the radial direction with respect to the same central axis. The occupied area along the relative movement direction of can be set short. The relationship between the reference coil 5 and the first excitation coil 4 is the same.
As described above, since the area for detecting the position by the output coil 7 and the second excitation coil 6 becomes short in the relative movement direction, it responds sensitively to changes in the relative position, and the spatial resolution of position detection Improve.

The positional relationship between the first exciting coil 4 and the reference coil 5 and the positional relationship between the second exciting coil 6 and the output coil 7 may be reversed.

It goes without saying that this embodiment is applicable to other embodiments.

(Embodiment 9)
The position detection device 1 according to the present invention detects displacement of a measurement object, and can be suitably applied to, for example, a liquid level gauge.

FIG. 15 is a schematic cross-sectional view of the liquid level gauge according to the present embodiment. A float 40 (float) is connected to the tip of the magnetic response body 2 of the position detection device 1 shown in FIG. 7, and a guide 41 is provided to be movable in the vertical direction. The buoyancy of the float 40 allows the magnetic response body 2 to float in the liquid to be measured.

The guide 41 has the same shape as the cross section of the magnetic response body 2 and has an opening 42 with a diameter larger than the diameter of the magnetic response body 2 so that the magnetic response body 2 can slide in the vertical direction. Can move vertically along the side of the opening 42 of the guide 41. Preferably, a bearing is provided on the inner surface of the guide 41 to reduce the friction between the magnetic response body 2 and the guide 41 by the bearing.

The first coil set (the first exciting coil 4 and the reference coil 5) and the second coil set (the second exciting coil 6 and the output coil 7) are connected and fixed by the connecting member 23.
Specifically, the connecting member 23 includes a first fixing portion 23a for fixing the first coil set, a second fixing portion 23c for fixing the second coil set, and a first fixing portion 23a and a second fixing portion 23a. It comprises three parts of the connection part 23b which connects the fixed part 23c at a predetermined interval.

These three parts are vertically connected as shown in the drawings.
The first fixing portion 23a and the second fixing portion 23c are made of, for example, insulating resin or ceramic, and even when an alternating voltage is applied to the first excitation coil 4 and the second excitation coil 6, Use materials that do not generate eddy currents.
The connection portion 23b is made of, for example, a rod-like metal or a highly rigid resin or ceramic in order to separate and fix the first coil set and the second coil set. In addition, the first fixing portion 23a, the second fixing portion 23c, and the connecting portion 23b may be integrally formed of, for example, a resin, a ceramic, or the like.

In addition, the electrical connection shown by FIG. 2 of a 1st coil group and a 2nd coil group can provide an electrical wiring in the connection member 23, and can ensure waterproofness with respect to an electrical wiring.

The first coil set, the second coil set, and the connecting member 23 are fixed to the guide 41 by a connecting jig (not shown). Therefore, the magnetic response body 2 and the second coil set are relatively movable.

In addition, as shown in FIG. 15, you may provide the supporting member 3 in the outer periphery of a 1st coil group. In this case, since the first coil set is fixed and supported by the first fixing portion 23a, the support member 3 for supporting the first coil set is unnecessary. However, by providing the support member 3 with a function as a magnetic core, the reference point of the output voltage Vout can be set.
The function as the magnetic core for the support member 3 has been described in the third embodiment and will not be described.

The first coil set, the second coil set, and the connecting member 23 are fixed by fixing the supporting member 3 and the first coil set and fixing the supporting member 3 and the guide 41 with a connecting jig (not shown). And the guide 41 may be fixed.

Hereinafter, the operation of the position detection device 1 of the present embodiment will be described.

The guide 41 is disposed and fixed, for example, in a container (not shown) for containing the liquid to be measured such that the side surface of the opening 42 of the guide 41 is in the vertical direction. The magnetic response body 2 to which the float 40 (float) is connected is slidably installed in the opening 42 and floats on the liquid surface to be measured.
Due to the buoyancy of the float 40, the magnetic response body 2 moves up and down in the moving direction determined by the side surface of the opening 42 of the guide 41, that is, in the vertical direction, depending on the fluctuation of the liquid level (water level).

The magnetic response body 2 changes according to the liquid level, so the liquid level can be measured by detecting the position of the magnetic response body 2.

Needless to say, it is possible to apply the position detection device 1 of the other embodiment as a modification of the present embodiment.

(Embodiment 10)
The position detection device 1 according to the present invention can be used not only to measure a linear relative movement distance but also to measure a relative movement distance on a curve, that is, an arc.

In the present embodiment, as shown in FIG. 16, for example, the shape of the magnetic response body 2 of the position detection device 1 shown in FIG. It is configured (to be part of a circle), and it becomes possible to measure the relative movement distance in the rotational direction (direction shown by the arrow in the figure) with the center of the circle as the axis of rotation.
That is, the magnetic response body 2 is configured such that the trajectory moving relative to the second coil set forms an arc (part of a circle), that is, along the trajectory on the relative arc. Since it moves, it is possible to measure the relative movement distance around the center of the circle as the rotation axis.
The electric resistance of the detection body 2 is configured to increase or decrease monotonously with respect to the rotation direction of the central axis. That is, the cross-sectional area in the radial direction (radial direction of the circle) of the detection body 2 is configured to decrease monotonically or increase monotonically with respect to the rotation angle.

The first coil set (the first exciting coil 4 and the reference coil 5) and the second coil set (the second exciting coil 6 and the output coil 7) are connected and fixed by the connecting member 23. The positional relationship is fixed.
The connecting member 23 is configured to be a part of a circle so as not to interfere with the side wall surface of the magnetic response body 2 inside the magnetic response body 2.

The magnetic response body 2 is rotatably supported by a rotating shaft (not shown).
On the other hand, the first coil set, the second coil set, and the connecting member 23 are connected and fixed to each other.

The magnetic response body 2 can move relatively to the second coil set within a range in which the second coil set does not contact the inner wall surface of the magnetic response body 2.

The magnetic response body 2 can measure the relative rotational movement distance of the measurement object (the relative movement distance along the trajectory on the arc) by connecting to the measurement object moving in rotation. Further, since the rotational movement distance is the product of the rotation radius and the rotation angle, and the rotation radius is the curvature radius of an arc, it is also possible to detect the rotation angle from the relative rotational movement distance.
Therefore, the rotation angle or inclination angle of the measurement object can be measured, and the position detection device 1 of the present embodiment also functions as a rotation angle detection device or an inclination angle detection device.

Moreover, it is needless to say that the shape of the magnetic response body 2 is not limited to that shown in FIG. 16, and the shapes shown in the other embodiments can be used.
Furthermore, as shown in FIG. 11, a ferromagnetic material may be provided outside the magnetic response body 2 of FIG. 16 to reduce the influence of temperature change.

(Embodiment 11)
It is also possible to apply the fourth embodiment to the position detection device 1 of the tenth embodiment capable of measuring the relative movement distance on the arc.

FIG. 17 (a) is a top view of the position detection device 1 according to this embodiment in which the magnetic response body 2 is formed of two opposing parallel flat plate ferromagnetic members, and FIG. 17 (b) is AA ′. FIG.
The third and fourth

magnetic response members

2c and 2d of parallel flat plates are disposed on the upper and lower sides of the connecting member 23. The magnetic flux generated by applying the AC voltage of the second excitation coil 6 penetrates the third and fourth

magnetic response bodies

2c and 2d, so that the mutual inductance value of the second coil set is the third and fourth ones. It changes depending on the width of the fourth

magnetic response members

2c, 2d.
The winding axes of the second excitation coil 6 and the output coil 7 are disposed perpendicularly to the third and fourth

magnetic response bodies

2c and 2d, as in FIG. 8 (f).

The widths of the third and fourth

magnetic responders

2c and 2d monotonously increase or decrease with respect to the relative movement distance between the second coil set and the third and fourth

magnetic responders

2c and 2d. When the thickness of the third and fourth

magnetic response members

2c and 2d is constant, the mutual inductance value of the second coil set monotonously increases or decreases with the relative movement distance.
As a result, the relative movement distance between the second coil set and the third and fourth

magnetic response members

2c and 2d can be detected, that is, the position can be detected.

Also, a reference body 12 for determining the mutual inductance value of the first coil set is provided, and it is composed of two opposing parallel flat plate ferromagnetic members in the same manner as the third and fourth

magnetic response bodies

2c and 2d. By doing this, it is possible to appropriately set a reference point at which the output voltage Vout, which is the difference between the output voltages of the output coil 7 and the reference coil 5, becomes 0 (zero).
The reference body 12 also has the same configuration as the third and fourth

magnetic response bodies

2c and 2d, and the winding axes of the first excitation coil 4 and the reference coil 5 are 2 as in FIG. 8 (g). It is arranged perpendicular to the two opposing reference bodies 12.

In addition, only one of the third and fourth

magnetic response bodies

2c and 2d configured as parallel flat plates may be configured as a single flat plate formed of only the third magnetic response body 2c, for example. The reference body 12 may be similarly configured of a single flat plate.

The width of the third and fourth

magnetic response members

2c and 2d may be fixed, and the cross-sectional thickness may be monotonously increased or decreased with respect to the relative movement distance.

Further, as described in the fourth embodiment, the third and fourth

magnetic response members

2c and 2d and the reference member 12 have a laminated structure of a ferromagnetic body and a conductor, and the conductor and the ferromagnetic body are combined. The temperature dependency of the output voltage Vout can be further reduced.

Further, one of the third and fourth

magnetic response members

2c and 2d consisting of two opposing parallel flat plates is composed of a ferromagnetic material, the other is composed of a conductor, and similarly, from the two opposing parallel flat plates It is also possible to reduce the temperature dependency of the output voltage Vout by configuring one of the reference body 12 with a ferromagnetic body and the other with a conductor, and combining the conductor and the ferromagnetic body. It is.

In addition, in said each embodiment, although cylindrical shape, a part of conical shape, and flat plate shape were illustrated as a shape of the magnetic response body 2 (20), it is not limited to it. When a conductor is used as the magnetic response body 2 (20), an eddy current is generated by the second coil set, and the value of the eddy current is relative to the relative movement distance between the magnetic response body 2 and the second coil set. It may be monotonously increased or decreased.

According to the present invention, it is possible to realize a position detection device capable of detecting a change in the position of a measurement object and having high resistance to noise and environmental temperature change. The position detection device according to the present invention can be expected to be applied in various fields, and has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Position detection device 2 Magnetic response body 2a 1st magnetic response body 2b 2nd magnetic response body 2c 3rd magnetic response body 2d 4th magnetic response body 3 Support member 4 1st exciting coil 5 Reference coil 6 1st 2 exciting coil 7 output coil 8

AC power supply

9a, 9b output terminal 10 opening 12 reference body 12a first reference body 12b second reference body 20 magnetic response body 21 first conductive member 22 first ferromagnetic member 23 connecting member 30 supporting member 31 second conductive member 32 second ferromagnetic member 40 float 41 guide 42 opening

Claims

A first excitation coil, a reference coil, a second excitation coil, an output coil, and a magnetic response body,
The magnetic response body and the output coil are movable relative to each other,
The output voltage of the output coil at the time of applying an AC voltage to the second excitation coil monotonously increases or monotonously depending on the relative movement distance of the magnetic response body with respect to the output coil.
The output voltage of the reference coil at the time of applying an AC voltage to the first excitation coil is constant regardless of the relative movement distance of the magnetic response body with respect to the output coil,
The position detection device characterized in that the reference coil and the output coil are differentially connected.
The position detecting device according to claim 1, wherein the magnetic response body includes a conductive member in which an electric resistance monotonously increases or monotonously decreases along a moving direction relative to the output coil.
The conductive member is
3. The position detection device according to claim 2, wherein the position detection device has a shape that is rotationally symmetrical with respect to an axis along the direction of relative movement with respect to the output coil, and the cross-sectional area decreases monotonously or monotonously.
The conductive member has a groove on its side wall surface,
3. The position detection device according to claim 2, wherein the cross-sectional area of the groove monotonously increases or monotonously along the direction of movement relative to the output coil.
The position detecting device according to any one of claims 2 to 4, wherein the magnetic response body includes a ferromagnetic member outside or inside the conductive member.
The conductive member is characterized in that the absolute value of the change in electrical resistance along the direction of movement relative to the output coil in a specific area is large as compared to other areas. The position detection device according to any one of the above.
The position detecting device according to claim 1, wherein the magnetic response body is made of a ferromagnetic material in which a cross-sectional area monotonously increases or monotonically decreases along a moving direction relative to the output coil.
The output coil and the second excitation coil have the same central axis, and are laminated in a radial direction with respect to the central axis. Position detection device as described.
9. The winding ratio of the reference coil with respect to the first excitation coil and the winding ratio of the output coil 7 with respect to the second excitation coil are the same, and both of them are larger than one. The position detection device according to any one of the above.
A float is connected to the magnetic response body,
The position detection apparatus according to any one of claims 1 to 9, further comprising a guide that movably supports the detection body.
The position detection device according to any one of claims 1 to 9, wherein the magnetic response body and the output coil are relatively movable along a circular arc trajectory.