JP2018194419A - Linear type differential transformer - Google Patents

Abstract

To provide a linear type differential transformer capable of simply improving a yield and having a long stroke.SOLUTION: A linear type differential transformer 10 comprises a bobbin 2, a primary coil 20, a secondary coil 21, a probe 3, a core 4, a first end plate 60a, a second end plate 60b and a case 5. The first end plate 60a is provided in a first end portion 22a of the bobbin 2, and the second end plate 60b is provided in a second end portion 22b. Flat surfaces are formed in a direction orthogonal to the axial direction of the bobbin 2 in the first end plate 60a and the second end plate 60b. A first ring-shaped shielding member 63a consisting of a magnetic material is provided on a first flat surface 62a being a flat surface at an outside of the first end plate 60a. A second ring-shaped shielding member 63b consisting of a magnetic material is provided on a second flat surface 62b being a flat surface at an outside of the second end plate 60b. And the first and second shielding members 63a and 63b are formed of, for example, a material having high permeability, such as permalloy.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a linear differential transformer.

  The linear differential transformer (LVDT) includes a rod-like probe containing a magnetic material in a cylindrical bobbin having a winding composed of a primary coil and a secondary coil. In the linear type differential transformer, when the core is linearly displaced in the bobbin, the magnetic coupling degree in the primary coil and the secondary coil that are magnetically coupled by the magnetic material changes, and the secondary coil is changed. The output voltage, which is the induced electromotive force generated, changes. The linear differential transformer detects the linear displacement of the probe from this changing output voltage.

  For example, as shown in FIG. 4, in the linear differential transformer 1 described in Patent Document 1, a primary coil 20 and a pair of secondary coils 21 are wound around a bobbin 2. The core 4 provided on the probe 3 is linearly displaced in the bobbin 2. At this time, when the core 4 approaches the end 22 of the bobbin 2, magnetic flux leaks out of the case 5, so that the linearity of the output of the linear differential transformer 1 deteriorates. For this reason, the output linearity is generally corrected by adding a correction coil winding to a portion of the secondary coil 21 close to the end 22. It is also common to use a design that does not use the vicinity of the end 22 where the linearity of the output deteriorates, using only the range in which the linearity of the good output can be maintained out of the total length of the linear differential transformer 1. Has been done.

JP 2000-213956 A

  However, when the correction coil winding is added, it is difficult to add the correction coil winding so as to obtain a stable output linearity, which leads to deterioration of the yield of the linear differential transformer 1. There's a problem. Further, when the design is such that the vicinity of the end portion 22 is not used, there is a problem that it is difficult to realize the long stroke linear differential transformer 1.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a linear differential transformer having a high yield and a long stroke in a simple manner.

  In order to solve the above problems, a linear differential transformer according to the present invention includes a bobbin in which a primary coil and a secondary coil are wound in a coaxial two-layer cylindrical shape and provided in a case; A core that is freely movable in the axial direction in the longitudinal hollow portion, and first and second ends that are provided at the first and second end portions of the bobbin and that are formed in a plane perpendicular to the axial direction of the bobbin. A second end plate, and each end plate is provided with first and second shield members, and leakage of magnetic flux generated from the primary coil and the secondary coil to the outside of the case by the shield members. The shield member is made of permalloy, and the shield members are provided in a ring shape.

  According to the linear differential transformer of the present invention, the first and second ends provided at the first and second ends of the bobbin and having a plane formed in a direction orthogonal to the axial direction of the bobbin. A plate, and each end plate is provided with first and second shield members, and each shield member shields leakage of magnetic flux generated from the primary coil and the secondary coil to the outside of the case. Therefore, a linear differential transformer having a high yield and a long stroke can be easily obtained.

It is a section schematic diagram of a linear type differential transformer concerning an embodiment of the invention. It is a cross-sectional schematic diagram of the first end plate and the second end plate shown in FIG. 2 is a linearity comparison between the linear differential transformer of FIG. 1 and a conventional linear differential transformer. It is the cross-sectional schematic of the conventional linear type differential transformer.

Hereinafter, a linear differential transformer according to an embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected and demonstrated to a part the same as that of a prior art example, or equivalent.
FIG. 1 is a schematic sectional view of a linear differential transformer according to an embodiment of the present invention.
As shown in FIG. 1, the linear differential transformer 10 includes a bobbin 2, a primary coil 20, a secondary coil 21, a probe 3, a core 4, a case 5, a first end plate 60a, and a second end plate 60b. , Is provided. The probe 3 is inserted into the bobbin 2 and is provided so as to be able to advance and retreat in the longitudinal hollow portion 23 of the bobbin 2. A core 4 is provided at the tip of the probe 3. The core 4 is linearly displaced in the longitudinal hollow portion 23 as the probe 3 advances and retreats.

  The primary coil 20 and the secondary coil 21 are wound around the bobbin 2. The primary coil 20 and the secondary coil 21 are formed in a coaxial double-layered cylindrical shape on the outer periphery of the bobbin 2, and the primary coil 20 is on the outer periphery of the bobbin 2 with respect to the outer periphery of the bobbin 2. The secondary coil 21 is provided directly on the outer periphery of the primary coil 20 via an insulating member (not shown). The primary coil 20 is connected to an AC power source (not shown). The secondary coil 21 is connected to a voltage sensor (not shown). The core 4, the primary coil 20, and the secondary coil 21 constitute a known linear differential transformer.

  The first end plate 60a is provided at the first end 22a of the bobbin 2, and the second end plate 60b is provided at the second end 22b. The first and second end plates 60 a and 60 b are ring-shaped with a hole 61 formed in the center, and the first and second end portions 22 a and 22 b are inserted into the hole 61. The first and second end plates 60a and 60b are formed of a known resin such as a PBT resin which is an insulating material. Flat surfaces are formed on the first and second end plates 60 a and 60 b in a direction orthogonal to the axial direction of the bobbin 2.

  As shown in FIG. 2A, a ring-shaped first made of a magnetic material so as to be embedded in a first plane 62a which is a plane on the end side of the bobbin 2 among the planes of the first end plate 60a. A shield member 63a is provided. Further, as shown in FIG. 2 (b), a ring-shaped ring made of a magnetic material is embedded in a second plane 62b which is a plane on the end side of the bobbin 2 among the planes of the second end plate 60b. A second shield member 63b is provided. The first and second shield members 63a and 63b are formed of a material having high magnetic permeability such as permalloy, for example.

  As shown in FIG. 1, the cylindrical case 5 is provided outside the secondary coil 21, the first end plate 60a, and the second end plate 60b.

Next, the operation of the linear differential transformer 10 according to this embodiment will be described.
When an alternating current flows through the primary coil 20, magnetic flux is generated from the primary coil 20 and the secondary coil 21. The magnetic flux passes through the core 4, the primary coil 20, and the secondary coil 21 to form a magnetic circuit. When the probe 3 moves in the axial direction of the bobbin 2 and the core 4 approaches the first end 22a, the magnetic flux easily passes through the first shield member 63a having a high magnetic permeability. Magnetic flux leaking from the vicinity of the first end 22a to the outside of the case 5 is shielded and reduced.

  Further, when the core 4 approaches the second end 22b, the magnetic flux easily passes through the second shield member 63b having a high magnetic permeability, and therefore, from the vicinity of the second end 22b to the outside of the case 5. The leaking magnetic flux is shielded and reduced by the second shield member 63b.

  Therefore, the linearity of the linear differential transformer 10 at the first end 22a and the second end 22b shown by solid lines in FIG. 3 is more than that of the conventional linear differential transformer shown by dotted lines. improves.

  As described above, the first and second end plates 60a and 60b, in which the first and second end portions 22a and 22b of the bobbin 2 are formed with a plane perpendicular to the axial direction of the bobbin 2, are provided. The first and second end plates 60a and 60b are provided with the first and second shield members 63a and 63b, and the primary coil 20 and the second shield members 63a and 63b. Since the configuration prevents the leakage of magnetic flux generated from the secondary coil 21 to the outside of the case 5, there is no need to perform a difficult task of adding a correction coil to the primary coil 20 and the secondary coil 21. Thus, a linear differential transformer having a good yield and a long stroke can be obtained.

  Further, since the first and second shield members 63a and 63b are permalloy, the magnetic permeability is high, and the magnetic flux leaking out of the case 5 can be shielded.

  In this embodiment, the material of the first and second shield members 63a and 63b is permalloy. However, other materials may be used as long as they have a high magnetic permeability. The first and second end plates 60a and 60b are formed of PBT resin or the like, but other appropriate known insulating materials may be used.

  In this embodiment, the first and second end plates 60a and 60b and the first and second shield members 63a and 63b are provided in a ring shape, but may have other shapes such as a polygonal shape. May be. Further, the first and second shield members 63a and 63b are provided so as to be embedded in the first and second end plates 60a and 60b. For example, the surfaces of the first and second end plates 60a and 60b are provided. The first and second shield members 63a and 63b may be provided by other appropriate methods.

  The gist of the linear differential transformer according to the present invention is as follows. That is, the primary coil 20 and the secondary coil 21 are wound in a coaxial double-layered cylindrical shape so that the bobbin 2 provided in the case 5 and the long hollow portion 23 of the bobbin 2 can freely move in the axial direction. The core 4 and the first and second end plates in which the first and second end portions 22a and 22b of the bobbin 2 are formed with planes perpendicular to the axial direction of the bobbin 2 and are movable. 60a, 60b, and the first and second end plates 60a, 60b are provided with the first and second shield members 63a, 63b, and the first and second shield members 63a, 63b It is configured to shield leakage of magnetic flux generated from the primary coil 20 and the secondary coil 21 to the outside of the case 5, and the material of the first and second shield members 63a and 63b is permalloy. In addition, the first 2 shield member 63a, 63b is configured as provided in annular.

  The linear differential transformer according to the present invention is capable of moving freely in the axial direction within a bobbin provided in a case in which a primary coil and a secondary coil are wound in a coaxial double-layered cylindrical shape, and inside the central axis of the bobbin And a first and second end plate provided at the first and second end portions of the bobbin and having a plane formed in a direction perpendicular to the axial direction of the bobbin. The plate is provided with first and second shield members, and the first and second shield members are configured to shield the leakage of magnetic flux generated from the primary coil and the secondary coil to the outside of the case. A linear differential transformer having a good yield and a long stroke can be obtained.

2 bobbin 4 core 5 case 10 linear differential transformer 20 primary coil 21 secondary coil 22a first end 22b second end 23 longitudinal hollow 60a first end plate 60b second end plate 63a first shield Member 63b second shield member

Claims (3)

A bobbin (2) provided in a case (5) in which a primary coil (20) and a secondary coil (21) are wound in a coaxial double-layer cylindrical shape;
A core (4) that is freely movable in the axial direction in the longitudinal hollow portion (23) of the bobbin (2);
First and second end plates (60a) provided on the first and second end portions (22a, 22b) of the bobbin (2) and having a plane formed in a direction orthogonal to the axial direction of the bobbin (2). 60b),
The end plates (60a, 60b) are provided with first and second shield members (63a, 63b), and the primary coil (20) and the secondary coil are formed by the shield members (63a, 63b). A linear differential transformer characterized in that the magnetic flux generated from the coil (21) is configured to shield leakage from outside the case (5).   The linear differential transformer according to claim 1, wherein a material of each shield member (63a, 63b) is permalloy.   The linear differential transformer according to claim 1 or 2, wherein each shield member (63a, 63b) is provided in a ring shape.

Images