JP2022144505A - Linearly variable differential transformer - Google Patents

Abstract

To provide a linearly variable differential transformer with which it is possible to suppress a disturbance magnetic field in the movable direction of a probe from being mixed in.SOLUTION: The linearly variable differential transformer comprises: a straight tube-like primary coil; a pair of secondary coils provided coaxially with the primary coil; probes provided in the inside of the primary and the secondary coils and capable of moving in the center axial direction of the primary and the secondary coils, with a magnetic core mounted to the probes; and a housing for accommodating some of the probes, the primary and the secondary coils and the magnetic core, which one end or both ends of a probe are put through, or which is provided with a pair of open holes, with a shield member provided that electrically shields the inside of the housing.SELECTED DRAWING: Figure 1

Description

The present invention relates to linear variable differential transformers.

US Pat. No. 6,200,000 describes a linear variable differential transformer (LVDT) used for measuring aircraft engines. The linear variable actuation transformer is an inductive electrical sensor for detecting linear displacement of an object, such as a variable stator vane, comprising a primary coil, a pair of secondary coils and a central core mounted on a probe. , detects the linear position of the object engaging the probe tip based on the change in the differential voltage of the pair of secondary coils, which depends on the linear displacement of the central core.

Japanese translation of PCT publication No. 2015-521747

By the way, the linear variable differential transformer described above has a linear coil having a structurally finite length with the moving direction of the central core being the direction of the central axis as the primary coil. At the ends of the primary coil, the magnetic flux density of the magnetic flux penetrating through the primary coil in the direction of the center axis drops sharply. The magnetic flux penetrating in the central axis direction is the magnetic flux that dominates the differential voltage. Therefore, the linear variable differential transformer has a basic problem that the detection accuracy of the linear displacement tends to deteriorate when the magnetic flux penetrating the primary coil in the central axis direction is mixed with the disturbance magnetic field.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a linear variable differential transformer capable of suppressing the mixing of a disturbance magnetic field in the moving direction of a probe.

In order to achieve the above object, in the present invention, as a first solution related to a linear variable differential transformer, a straight tubular primary coil, a pair of secondary coils provided coaxially with the primary coil, a probe provided inside the primary coil and the secondary coil, movable in a central axis direction of the primary coil and the secondary coil, and having a magnetic core mounted thereon; a part of the probe, the primary coil, and the A means comprising a housing containing a secondary coil and the magnetic core and provided with a through hole through which one end of the probe penetrates, and a shield member for electromagnetically shielding the inside of the housing. adopt.

According to the present invention, as a second solution to the linear variable differential transformer, in the first solution, the shield member is provided on a side of the housing perpendicular to the central axis direction. to adopt.

In the present invention, as a third solution to the linear variable differential transformer, in the second solution, the shield member constitutes the housing.

In the present invention, as a fourth solution to the linear variable differential transformer, in any one of the first to third solutions, the shield member includes a magnetic member and a conductive member, and the magnetic member is arranged on the inside and the conductive member is arranged on the outside.

In the present invention, as a fifth solution related to the linear variable differential transformer, in the above fourth solution, the magnetic member and the conductive member are plate members and are arranged so as to overlap each other. adopt the means of

In the present invention, as a sixth solution to the linear variable differential transformer, in any one of the first to fifth solutions, the linear variable differential transformer is arranged coaxially with the rotating shaft in the rotor of the rotary electric machine. adopt means.

ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the linear variable differential transformer which can suppress mixing of the disturbance magnetic field to the central axis direction of a primary coil.

1 is a perspective view showing the overall configuration of a linear variable differential transformer according to one embodiment of the present invention; FIG. 1 is a perspective view showing an internal configuration of a linear variable differential transformer according to one embodiment of the present invention; FIG. 1 is a cross-sectional view showing an internal configuration of a linear variable differential transformer according to one embodiment of the present invention; FIG. FIG. 4 is a characteristic diagram showing the position detection accuracy of the linear variable differential transformer according to one embodiment of the present invention;

An embodiment of the present invention will be described below with reference to the drawings.
A linear variable differential transformer A according to this embodiment is a substantially cylindrical displacement sensor that is attached to an electric motor B as shown in FIG.

Note that this electric motor B corresponds to the rotating electric machine of the present invention. In addition, in FIGS. 1 and 2, three orthogonal axes consisting of the X-axis, Y-axis and Z-axis are added. In this linear variable differential transformer A, the central axis direction is parallel to the Z-axis.

The electric motor B will be described first. This electric motor B has a well-known configuration and includes a stator b1, a rotor b2 and a rotating shaft b3. The stator b1 has a predetermined number of slots arranged in an annular shape. Each slot has a stator core and stator windings and functions as a plurality of electromagnets that generate a rotating magnetic field.

The rotor b2 is an annular member fixed to the rotating shaft b3 and arranged inside the stator b1. The outer peripheral portion of the rotor b2 faces the tip portion of the slot with a small gap therebetween, and permanent magnets that form magnetic poles at predetermined electrical angles are arranged on the outer peripheral portion. Rotational force acts on the rotor b2 due to electromagnetic coupling with the stator b1.

The rotary shaft b3 is a rod-shaped metal member and is the output shaft of the electric motor B. As shown in FIG. That is, the rotating shaft b3 is a rod-shaped metal member that rotates by the torque acting on the rotor b2, and has a through hole b4 formed in the central axis direction. The linear variable differential transformer A according to the present embodiment is, as shown in the figure, a substantially rod-shaped member that is inserted into the through hole b4 at regular intervals.

As shown in FIGS. 1, 2 and 3, the linear variable differential transformer A is arranged coaxially with a rotating shaft b3 in the rotor of an electric motor B (rotating electric machine). , a probe 3 , a bobbin 4 , a primary coil 5 , a pair of secondary coils 6 A, 6 B, a magnetic core 7 and a guide member 8 . Among the components of such a linear variable differential transformer A, the housing 1 corresponds to the shield member of the present invention.

The housing 1 is the most characteristic component in this embodiment, and is a bottomed cylindrical member as illustrated. The housing 1 comprises a cylindrical side 1a and a disk-shaped bottom 1b, 1c and includes a portion of a probe 3, a primary coil 5, a pair of secondary coils 6A, 6B, a magnetic core 7 and guides. The member 8 is accommodated. The side portion 1a is composed of a cylindrical magnetic member 1d, a cylindrical conductive member 1e and a thin cylindrical magnetic member 1f.

That is, the side portion 1a has a three-layer structure in which a cylindrical magnetic member 1d is arranged outside, a cylindrical conductive member 1e is arranged in the middle, and a thin cylindrical magnetic member 1f is arranged inside. The cylindrical magnetic member 1d, the cylindrical conductive member 1e, and the cylindrical thin magnetic member 1f are plate members (plate members) each having a cylindrical shape and a predetermined thickness, and are arranged adjacent to each other so as to be in contact with each other, that is, overlap. ing.

Here, the cylindrical thin magnetic member 1d and the cylindrical thin magnetic member 1f are made of the same magnetic material, but the thickness of the cylindrical thin magnetic member 1f is set smaller than that of the cylindrical magnetic member 1d. there is The thickness ratio between the cylindrical thin magnetic member 1f and the cylindrical magnetic member 1d is, for example, 1:8.76. In addition, the cylindrical magnetic member 1d and the cylindrical thin magnetic member 1f are made of a material known as a magnetic material, such as permalloy.

On the other hand, the cylindrical conductive member 1e is made of a metal material with excellent conductivity and workability. The cylindrical conductive member 1e constitutes the side portion 1a while being sandwiched between the cylindrical magnetic member 1d and the cylindrical thin magnetic member 1f. The cylindrical conductive member 1e is arranged inside the cylindrical magnetic member 1d, which has a relatively large thickness, out of the cylindrical magnetic member 1d and the cylindrical thin magnetic member 1f. A metal material forming such a cylindrical conductive member 1e is, for example, pure copper.

As shown in FIG. 1, one bottom portion 1b is formed with a through hole h penetrating through the center. That is, the housing 1 in this embodiment accommodates a portion of the probe 3, the primary coil 5, the pair of secondary coils 6A and 6B, the magnetic core 7, and the guide member 8 as described above. is provided with a through hole h through which one end of the is passed.

Also, as shown in FIG. 2, the bottom portion 1b is composed of a disk-shaped magnetic member 1g and a disk-shaped conductive member 1h. The disc-shaped magnetic member 1g and the disc-shaped conductive member 1h are plate members (plate members) each having a predetermined thickness, and are arranged adjacent to each other so as to be in contact with each other, that is, overlap.

That is, the side portion 1a has a two-layer structure in which the disk-shaped magnetic member 1g is arranged on the outside and the disk-shaped conductive member 1h is arranged on the inside. The disk-shaped magnetic member 1g is made of the same magnetic material as the cylindrical magnetic member 1d and the cylindrical thin-walled magnetic member 1f described above, but its thickness is set larger than that of the cylindrical magnetic member 1d. The thickness ratio between the disk-shaped magnetic member 1g and the cylindrical magnetic member 1d is, for example, 1:0.8.

The disk-shaped conductive member 1h is made of the same conductive material as that of the cylindrical conductive member 1e described above, but is set larger in thickness and/or conductivity than the cylindrical conductive member 1e. there is The thickness and/or conductivity ratio of the disk-shaped conductive member 1h and the cylindrical conductive member 1e is, for example, 1:0.89.

The other bottom portion 1c, as shown in FIG. 2, is composed of a disk-shaped magnetic member 1i and a disk-shaped conductive member 1j. The disk-shaped magnetic member 1i and the disk-shaped conductive member 1j are plate members each having a predetermined thickness, and are arranged so as to be in contact with each other, that is, overlap each other.

That is, the side portion 1a has a two-layer structure in which the disk-shaped magnetic member 1i is arranged on the outside and the disk-shaped conductive member 1j is arranged on the inside. The disk-shaped magnetic member 1i is made of the same magnetic material as the cylindrical magnetic member 1d and the cylindrical thin-walled magnetic member 1f described above, but its thickness is set smaller than that of the cylindrical magnetic member 1d. The thickness ratio between the disk-shaped magnetic member 1i and the cylindrical magnetic member 1d is, for example, 1:1.23.

The disk-shaped conductive member 1j is made of the same conductive material as the cylindrical conductive member 1e described above, but is set larger in thickness and/or conductivity than the cylindrical conductive member 1e. there is The thickness and/or conductivity ratio of the disk-shaped conductive member 1j and the cylindrical conductive member 1e is, for example, 1:0.89.

The bracket 2 is a metal member circumscribing the side portion 1a of the housing 1, and includes a tubular portion 2a and a flange portion 2b as shown in FIG. The cylindrical portion 2 a is a cylindrical portion whose inner peripheral surface contacts the side portion 1 a of the housing 1 . The flange portion 2b is a plate portion having a predetermined thickness provided outside the tubular portion 2a, and is formed with a plurality of mounting holes. These mounting holes are screw holes for fixing the linear variable differential transformer A. As shown in FIG.

The probe 3 is a rod-like member provided coaxially with the bottomed cylindrical housing 1 as shown. That is, the probe 3 is provided in a state of being inserted through a through hole h that penetrates the center of the housing 1, and is movable in the central axis direction (Z-axis direction) of the housing 1, that is, in the central axis direction of itself. be. Such a probe 3 is provided with an engaging member 2a that engages with an object at one end (tip) in the direction of the central axis, that is, in the direction of movement (Z-axis direction). Further, the probe 3 has a cylindrical magnetic core 7 fixed in the middle of the movable direction (Z-axis direction).

The bobbin 4 is a cylindrical member provided coaxially with the housing 1 and the probe 3 within the housing 1 . The bobbin 4 is a cylindrical member having a predetermined length and made of a non-magnetic material. That is, the bobbin 4 is accommodated in the housing 1 so that the inner surface (cylindrical surface) forms a constant gap with respect to the peripheral surface (cylindrical surface) of the magnetic core 7 fixed to the probe 3 .

The primary coil 5 is a straight tube-like winding wound in the central axis direction with a predetermined length around the outer periphery of the bobbin 4 having a predetermined length. An alternating current (excitation current) for exciting the pair of secondary coils 6A and 6B is supplied to the primary coil 5 from an external power source (not shown). An exciting magnetic field is generated around the primary coil 5 based on the exciting current.

The pair of secondary coils 6A and 6B are straight tubular windings coaxial with the primary coil 5 and tapered to a predetermined length. That is, of the pair of secondary coils 6A and 6B, one secondary coil 6A is tapered to a predetermined length on the surface of the primary coil 5 in the direction of the central axis, and the other secondary coil 6B is , is tapered to a predetermined length on the surface of the primary coil 5 in the direction of the central axis.

Such a pair of secondary coils 6A, 6B outputs an induced voltage based on the exciting magnetic field generated by the primary coil 5, respectively. That is, the primary coil 5 and one secondary coil 6A, and the primary coil 5 and the other secondary coil 6A respectively constitute a transformer. The primary coil 5 and one secondary coil 6A constitute a first transformer, and the primary coil 5 and the other secondary coil 6A constitute a second transformer.

The magnetic core 7 is a cylindrical magnetic member fixed coaxially with the probe 3 in the middle of the probe 3 . The length of the magnetic core 7 in the central axis direction of the probe 3 and the housing 1, that is, the length in the central axis direction of itself is set to a predetermined length. Such a magnetic core 7 varies each coupling coefficient of the first transformer and the second transformer according to the position in the central axis direction.

Here, in the first and second transformers described above, the coupling coefficient changes according to the position of the magnetic core 7 which is movable inside the bobbin 4 in the central axis direction. As a result, the change characteristic of the induced voltage (first induced voltage) output by one secondary coil 6A according to the position of the magnetic core 7 is the induced voltage (second induced voltage) output by the other secondary coil 6B. ) depending on the position of the magnetic core 7, the characteristics are reverse.

As shown in FIG. 2, the guide member 8 is provided inside the housing 1 in the vicinity of the other bottom portion 1c. The guide member 8 is an assembly of a plurality of disk-shaped members provided coaxially, and guides the lead wire of the primary coil 5 and the lead wires of the pair of secondary coils 6A and 6B. Although not shown, the lead wire of the primary coil 5 and the lead wires of the pair of secondary coils 6A and 6B are led out of the housing 1 from inside the housing 1 via the guide member 8. FIG.

Next, the effects of the linear variable differential transformer A according to this embodiment will be described in detail with reference to FIG. 4 as well.

In this linear variable differential transformer A, the excitation magnetic field generated by the primary coil 5 acts on the pair of secondary coils 6A and 6B via the magnetic core 7, thereby causing a first induction in one of the secondary coils 6A. A voltage is generated, and a second induced voltage is generated in the other secondary coil 6B. The excitation magnetic field passes through the primary coil 5, the pair of secondary coils 6A and 6B, and the magnetic core 7 mainly in the central axis direction.

A pair of secondary coils 6A and 6B generate a first induced voltage and a second induced voltage mainly based on the excitation magnetic field passing in the movable direction (Z-axis direction). That is, one secondary coil 6A generates a first induced voltage based on an exciting magnetic field passing in the moving direction, and the other secondary coil 6B generates a second induced voltage based on an exciting magnetic field passing in the moving direction. Generate an induced voltage.

The linear variable differential transformer A is a displacement sensor that detects the position of the object to be detected in the central axis direction by the action of an exciting magnetic field passing through it in the moving direction. The magnetic core 7 is fixed to the probe 3, and since the probe 3 is engaged with the object to be detected, the position of the magnetic core 7 in the moving direction (Z-axis direction) is changes depending on the position of That is, the first induced voltage and the second induced voltage change according to the position of the magnetic core 7 in the movable direction.

Such a linear variable differential transformer A converts the difference between the first induced voltage and the second induced voltage, that is, the differential voltage, which changes according to the position in the central axis direction of the object, to the moving direction of the object. Output as a detection signal indicating the position.

On the other hand, when the electric motor B starts operating, a loop-shaped magnetic flux is generated that passes through each slot of the stator b1 and each magnetic pole of the rotor b2. This magnetic flux passes through the rotating shaft b3 in the Z-axis direction. That is, the magnetic field generated by the electric motor B is magnetic flux that passes through the linear variable differential transformer A in the central axis direction, and acts on the linear variable differential transformer A as a disturbance magnetic field.

The interior of the linear variable differential transformer A is magnetically and electrically shielded by the housing 1 against the disturbance magnetic field of the electric motor B as described above. That is, the housing 1 has the side portion 1a and the bottom portions 1b and 1c formed of the magnetic material and the conductive material as described above, and prevents the disturbance magnetic field of the electric motor B from affecting the inside of the housing 1. or significantly suppressed.

Among the disturbance magnetic fields of the electric motor B, the low-frequency magnetic field with a relatively low frequency is covered inside the linear variable differential transformer A with the outermost cylindrical magnetic member 1d and disk-shaped magnetic members 1g and 1i. Therefore, it does not act as a disturbance to the excitation magnetic field passing in the moving direction of the probe 3 .

Among the disturbance magnetic fields of the electric motor B, the high-frequency magnetic field with a relatively high frequency is covered by the cylindrical conductive member 1e and the disk-shaped conductive members 1h and 1j inside the linear variable differential transformer A. Therefore, an eddy current is generated in the cylindrical conductive member 1e and the disk-shaped conductive members 1h and 1j. Since this eddy current generates a magnetic field in the direction of canceling the high-frequency magnetic field, it does not act as a disturbance on the excitation magnetic field passing in the moving direction (Z-axis direction) of the probe 3 .

According to this embodiment, since the inside of the housing 1 is magnetically and electrically shielded by the housing 1 functioning as a shield member, the stray magnetic field is sufficiently prevented from entering in the moving direction of the probe 3. It is possible to provide a linear variable differential transformer A capable of suppressing to

FIG. 4 is a characteristic diagram showing an example of the position detection accuracy of the linear variable differential transformer A according to this embodiment. As shown in FIG. 4, in the linear variable differential transformer A according to this embodiment, the disturbance magnetic field of the electric motor B is greatly suppressed from acting as a disturbance. It is possible to detect the position with higher accuracy than conventionally (when no shield member is provided).

Further, in the present embodiment, the housing 1 is configured as a shield member, so the size of the linear variable differential transformer A can be reduced, or the size of the linear variable differential transformer A can be reduced or It is possible to increase the size of the primary coil 5, the pair of secondary coils 6A and 6B, the magnetic core 7, and the like, which are housed in the coil.

It should be noted that the present invention is not limited to the above-described embodiments, and for example, the following modifications are conceivable.
(1) In the above embodiment, the housing 1 is configured as a shield member, but the present invention is not limited to this. A shield member for electromagnetically shielding the inside of the housing 1 may be provided separately from the housing 1 .

(2) In the above embodiment, the inside of the housing 1 is covered in all directions with the shield member, but the present invention is not limited to this. The shield member may cover only the direction from which the disturbance magnetic field enters. For example, in the arrangement state of the linear variable differential transformer A and the electric motor B shown in FIG. , the shield member may be provided only on the side perpendicular to the central axis direction, that is, only on the side portion 1a of the housing 1. FIG.

(3) In the above embodiment, the linear variable differential transformer A is arranged coaxially with the rotary shaft b3 in the rotor b2 of the electric motor B (rotating electric machine), but the present invention is not limited to this. That is, the rotating electric machine of the present invention is not limited to the electric motor B, and may be, for example, a generator.

A linear variable differential transformer B electric motor b1 stator b2 rotor b3 rotating shaft b4 through hole 1 housing (shield member)
2 bracket 3 probe 4 bobbin 5 primary coil 6A, 6B secondary coil 7 magnetic core 8 guide member

Claims (6)

a straight tubular primary coil;
a pair of secondary coils provided coaxially with the primary coil;
a probe provided inside the primary coil and the secondary coil, movable in the central axis direction of the primary coil and the secondary coil, and having a magnetic core mounted thereon;
A housing containing a part of the probe, the primary coil, the secondary coil and the magnetic core and provided with a through hole through which one end of the probe penetrates,
A linear variable differential transformer, comprising a shield member for electromagnetically shielding the interior of the housing. 2. The linear variable differential transformer according to claim 1, wherein the shield member is provided on a side of the housing perpendicular to the direction of the central axis. 3. The linear variable differential transformer according to claim 2, wherein said shield member constitutes said housing. The linear variable according to any one of claims 1 to 3, wherein the shield member includes a magnetic member and a conductive member, wherein the magnetic member is arranged inside and the conductive member is arranged outside. Differential transformer. 5. The linear variable differential transformer according to claim 4, wherein the magnetic member and the conductive member are plate members and are arranged so as to overlap each other. 6. The linear variable differential transformer according to any one of claims 1 to 5, wherein the linear variable differential transformer is arranged coaxially with a rotating shaft in a rotor of a rotating electric machine.

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