JP2013160668A - Core holder and current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core holder and current sensor for suppressing a change in magnetic characteristics of a core.SOLUTION: A core holder 3 is roughly constituted by including: a first protection wall 30 for protecting an outer peripheral surface 20 of a core 2 from pressure from an outside, the core 2 having a first end surface 22 from which magnetic field lines 60 are emitted and a second end surface 23 into which the magnetic field lines 60 are sucked; a second protection wall 31 for protecting an inner peripheral surface 21, the first end surface 22, and the second end surface 23 of the core 2 from pressure from the outside; and a side surface protection wall 32 that is integrated with the first protection wall 30 and the second protection wall 31 and protects at least one side surface of the core 2 from the pressure from the outside.

Description

  The present invention relates to a core holder and a current sensor.

  As a conventional technique, a current sensor that houses a core and a hall element in a component housing chamber in a case body is known (for example, see Patent Document 1).

  This current sensor can prevent the misalignment between the core and the Hall element by filling the component housing chamber with a molding agent.

JP 2009-222729 A

  However, in the conventional current sensor, stress is generated inside the core due to the pressure applied to the core due to the hardening of the molding agent. Due to this stress, there is a problem that current detection accuracy is lowered due to a change in magnetic characteristics such as an increase in the remanent magnetization of the core.

  Accordingly, an object of the present invention is to provide a core holder and a current sensor that suppress changes in the magnetic characteristics of the core.

  One embodiment of the present invention includes a first protective wall that protects an outer peripheral surface of a core having a first end surface from which magnetic lines of force spring out and a second end surface from which magnetic lines of force are sucked, from an external pressure, and an inner periphery of the core A second protective wall that protects the surface, the first end surface, and the second end surface from external pressure, and the first protective wall and the second protective wall, and at least one side surface of the core is And a side protection wall that protects against pressure from the core holder.

  According to the present invention, it is possible to suppress changes in the magnetic characteristics of the core.

FIG. 1A is a perspective view of a current sensor according to an embodiment, and FIG. 1B is a perspective view of a core and a core holder. Fig.2 (a) is the schematic which looked at the core holder which concerns on embodiment from the accommodating part side, (b) is the schematic which looked at the core from the 1st side surface.

(Summary of embodiment)
A core holder according to an embodiment includes: a first protective wall that protects an outer peripheral surface of a core having a first end surface from which magnetic lines of force spring out and a second end surface from which magnetic lines of force are sucked; The second protective wall that protects the peripheral surface, the first end surface, and the second end surface from external pressure, and the first protective wall and the second protective wall are integrated with each other, and at least one side surface of the core is A side protection wall that protects against pressure from the outside.

[Embodiment]
(Configuration of current sensor 1)
FIG. 1A is a perspective view of a current sensor according to an embodiment, and FIG. 1B is a perspective view of a core and a core holder. Fig.2 (a) is the schematic which looked at the core holder which concerns on embodiment from the accommodating part side, (b) is the schematic which looked at the core from the 1st side surface. In each drawing according to the embodiment, the ratio between parts may differ from the actual ratio.

  For example, the current sensor 1 causes the magnetic sensor 5 to detect the magnetic field 6 generated by the current flowing through the bus bar 4 via the core 2. For example, the magnetic sensor 5 outputs a detection signal corresponding to the detected magnetic field 6 to a converter connected to the current sensor 1. For example, the converter is configured to obtain the current value of the current flowing through the bus bar 4 by converting the acquired detection signal into a current value.

  The current sensor 1 according to the present embodiment includes a core holder 3 that is loaded based on insert molding and protects the core 2 from external pressure.

  The core holder 3 includes a first protective wall 30 that protects the outer peripheral surface 20 of the core 2 having a first end surface 22 from which magnetic lines of force 60 spring out and a second end surface 23 into which the magnetic lines of force 60 are sucked, from pressure from the outside. The second protective wall 31 that protects the inner peripheral surface 21, the first end surface 22, and the second end surface 23 of the core 2 from external pressure, and the first protective wall 30 and the second protective wall 31. And a side surface protection wall 32 that protects at least one side surface of the core 2 from external pressure.

  The current sensor 1 includes a bus bar 4 through which a current flows and a magnetic sensor 5 that detects a magnetic field.

  The direction of the magnetic lines of force 60 changes depending on the direction of the current flowing through the bus bar 4. In the present embodiment, for example, the current flows from right to left on the paper surface of FIG. 1A, so that the magnetic lines of force 60 spring out from the first end surface 22 and are sucked into the second end surface 23. However, for example, when the current flows from left to right on the paper surface of FIG. 1A, the direction of the magnetic force line 60 is reversed, so that the current flows out from the second end surface 23 and is sucked into the first end surface 22.

(Configuration of core 2)
The core 2 is formed by, for example, press-working a plurality of ferromagnetic bodies formed by punching a plate so as to have a horseshoe shape and caulking them together. This ferromagnetic material is, for example, an electromagnetic steel plate (silicon steel plate). The core 2 may be made of, for example, one ferromagnetic material.

  For example, as illustrated in FIG. 2B, the core 2 has a shape close to an ellipse when viewed from the first side face 25 side. The first end surface 22 and the second end surface 23 are formed in the major axis direction of the core 2. The magnetic sensor 5 is disposed in a region surrounded by the first end surface 22 and the second end surface 23, that is, the gap 24. This arrangement is performed so that the magnetic force lines 60 existing between the first end surface 22 and the second end surface 23 and the detection surface of the magnetic sensor 5 are in a positional relationship that substantially intersects perpendicularly. Is preferred.

(Configuration of core holder 3)
For example, the core 2, the core holder 3, and the bus bar 4 are integrated by insert molding in a state where the core 2, the core holder 3, and the bus bar 4 are assembled. At the time of this insert molding, the mold jig is inserted, for example, between a first end surface protection portion 311 and a second end surface protection portion 312 described later of the core holder 3, and the core holder 3 and the like are attached to the mold. .

  For example, the core holder 3 relieves pressure from the outside of the core holder 3 that is loaded when the resin is injected into the mold and the injected resin is cured (hereinafter referred to as molding pressure). From the viewpoint, it is preferable to use the resin used for the insert molding. That is, using the same resin is advantageous in that the molding pressure applied to the core holder 3 is suppressed as the resin expands and contracts. In this embodiment, as an example, this resin uses polyphenylenesulfide-PPS. Therefore, the core holder 3 is formed using, for example, polyphenylene sulfide.

  The core holder 3 is, for example, a housing part formed by a first protective wall 30, a second protective wall 31, and a side protective wall 32 as shown in FIGS. 1 (a), 1 (b) and 2 (a). 33 is configured to accommodate the core 2.

  The core holder 3 protects the core 2 from the molding pressure applied by insert molding by accommodating the core 2 in the accommodating portion 33.

  Here, it is known that the magnetic characteristics of the core may change depending on the molding pressure applied to the core along with the insert molding. It has been found that when the molding pressure is applied from the side surface side of the core, the change in magnetic characteristics is small, and when the molding pressure is applied from the peripheral surface side of the core, the change in magnetic characteristics is large.

  This change in magnetic characteristics is, for example, the opening of a magnetic hysteresis curve. When the magnetic hysteresis curve of the core opens, magnetization remains in the core (residual magnetization) even when there is no magnetic field, that is, no current flows through the bus bar, and is detected by the magnetic sensor. That is, the offset of the current sensor 1 changes. Therefore, the magnetic sensor cannot accurately detect the magnetic field generated by the current flowing through the bus bar due to the residual magnetization of the core, and the current detection accuracy is lowered.

  However, in this embodiment, since the core 2 is accommodated in the core holder 3, a molding pressure is applied to the outer peripheral surface 20, the inner peripheral surface 21, the first end surface 22, and the second end surface 23 of the core 2. It has become difficult. Therefore, the core 2 can have magnetic characteristics that are substantially the same as those before insert molding even after insert molding. In the present embodiment, the core holder 3 has a structure in which one side surface of the core 2 is exposed. However, the present invention is not limited to this, and the side surface exposed by a lid or the like may be covered.

  The clearance between the housing part 33 and the core 2 is preferably such that, for example, the resin injected into the mold does not enter the gap between the housing part 33 and the core 2. As an example, the clearance is 0.1 mm to 0.2 mm.

  The first protective wall 30 of the core holder 3 is formed so as to cover the outer peripheral surface 20 of the core 2, for example, as shown in FIGS. 1 (b) and 2 (a). An insertion opening 34 is formed by both end portions of the first protective wall 30.

  The second protective wall 31 is formed in the inner peripheral surface protection unit 310 that protects the inner peripheral surface 21 of the core 2 and the bus bar holding unit that holds the bus bar 4 through which the current to be measured flows. 310a.

  The second protective wall 31 includes a first end surface protection portion 311 that protects the first end surface 22, a second end surface protection portion 312 that protects the second end surface 23, and a first end surface protection portion 311. And a slit 35 into which the bus bar 4 can be inserted from the space between the first end face protecting part 312 to the bus bar holding part 310a. In other words, the second protective wall 31 is, for example, a slit 35 that connects portions corresponding to the hole 210 penetrating from the first side surface 25 of the core 2 to the second side surface 26 and the gap 24 of the core 2. Is formed.

  For example, the slit 35 is thicker than a portion corresponding to the gap 24 of the core 2, and a portion to which the bus bar 4 is attached serves as a bus bar holding portion 310 a. The bus bar holding portion 310 a is formed corresponding to the hole 210 of the core 2. The bus bar 4 may be arranged so that the center of the hole 210 of the core 2 is the center of the magnetic field 6 so that the magnetic field 6 generated by the flowing current efficiently forms a magnetic path inside the core 2. preferable. Therefore, the bus bar holding portion 310 a is formed such that the center of the magnetic field 6 generated in the inserted bus bar 4 is substantially the center of the hole 210 of the core 2.

  Further, for example, the magnetic sensor 5 is inserted into a portion of the slit 35 corresponding to the gap 24 of the core 2.

(Configuration of magnetic sensor 5)
As the magnetic sensor 5, for example, a Hall sensor that outputs an electrical signal corresponding to a magnetic field, a GMR (Giant Magneto Resistive) sensor, or the like can be used. In the present embodiment, a Hall sensor is used as the magnetic sensor 5.

  The magnetic sensor 5 may be, for example, a sensor IC (Integrated Circuit) in which a sensor in which a magnetic detection element is molded with resin, a bare chip, a control circuit, and the like are integrated.

(Configuration of bus bar 4)
For example, the bus bar 4 is formed in a plate shape using a conductive material. Examples of the conductive material include copper and a copper alloy.

  For example, as shown in FIG. 1A, the bus bar 4 has an L shape in which one end portion of an elongated plate-shaped base portion 40 is bent at 90 °. For example, a connector portion 42 is formed at the other end portion of the base portion 40.

  For example, the connector portion 42 is configured to be electrically connected to an electronic circuit so that a current to be measured flows through the bus bar 4.

(Effect of embodiment)
The core holder 3 according to the present embodiment can suppress changes in the magnetic properties of the core 2. Specifically, the core holder 3 accommodates the core 2 in the accommodating portion 33, thereby causing the magnetic characteristics to change, and the outer peripheral surface 20, the inner peripheral surface 21, the first end surface 22, and the second end surface 23. It is possible to suppress the molding pressure applied to the surface. As a result, the residual magnetization of the core 2 is suppressed, and the change in the offset can be suppressed compared with the case where the residual magnetization is generated in the core, so that the effort for setting the offset is suppressed and the detection accuracy of the current sensor 1 is improved. improves.

  Moreover, since the core holder 3 holds the core 2 by the accommodating part 33 and holds the bus bar 4 by the bus bar holding part 310a, the misalignment between the core 2 and the bus bar 4 can be suppressed. When insert molding is performed, when the core and bus bar are assembled and placed in the mold, and the resin is injected into the mold, the bus bar falls down due to the pressure generated during the injection, causing the core and bus bar to be misaligned. It may occur. However, in this embodiment, since the core 2 and the bus bar 4 can be held by the core holder 3 and the positional relationship between the core 2 and the bus bar 4 can be held, it is easy to attach to the mold and insert molding. Since the positional deviation at the time can be suppressed, the detection accuracy of the current sensor 1 is improved.

  Further, the current sensor 1 can be easily manufactured and the manufacturing cost can be reduced because the core holder 3 facilitates the assembly of the core 2 and the bus bar 4 and suppresses the displacement caused by the insert molding.

  Further, the core holder 3 has the bus bar 4 in the slit 35 in the direction from the outer peripheral surface 20 of the core 2 toward the inner peripheral surface 21 even when the bus bar 4 has a shape in which the hole 210 of the core 2 cannot pass. Since it can insert, compared with the case where it inserts in the hole of a core, the freedom degree of the shape of the bus bar 4 is high. Therefore, the current sensor 1 has a high degree of freedom of installation.

  As mentioned above, although some embodiment of this invention was described, these embodiment is only an example and does not limit the invention which concerns on a claim. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the scope of the present invention. In addition, not all the combinations of features described in these embodiments are essential to the means for solving the problems of the invention. Furthermore, these embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Current sensor 2 ... Core 3 ... Core holder 4 ... Bus bar 5 ... Magnetic sensor 6 ... Magnetic field 20 ... Outer peripheral surface 21 ... Inner peripheral surface 22 ... First end surface 23 ... Second end surface 24 ... Gap 25 ... First side surface 26 ... 2nd side surface 30 ... 1st protection wall 31 ... 2nd protection wall 32 ... Side surface protection wall 33 ... Accommodating part 34 ... Insertion opening 35 ... Slit 40 ... Base part 42 ... Connector part 60 ... Magnetic field line 210 ... Hole 310 ... Inner peripheral surface protection part 310a ... Bus bar holding part 311 ... First end face protection part 312 ... First end face protection part

Claims (4)

A first protective wall that protects the outer peripheral surface of the core having a first end face from which magnetic lines of force spring out and a second end face from which the magnetic lines of force are sucked from external pressure;
A second protective wall that protects the inner peripheral surface of the core, the first end surface, and the second end surface from pressure from the outside;
A side protection wall that is integrated with the first protection wall and the second protection wall and protects at least one side surface of the core from the pressure from the outside;
Core holder with The second protective wall is
An inner peripheral surface protection part for protecting the inner peripheral surface of the core;
A bus bar holding unit that is formed in the inner peripheral surface protection unit and holds a bus bar through which a current to be measured flows;
The core holder according to claim 1, comprising: The second protective wall is
A first end face protecting portion for protecting the first end face;
A second end face protection portion for protecting the second end face;
A slit into which the bus bar can be inserted from between the first end face protection part and the second end face protection part to the bus bar holding part;
The core holder according to claim 2 provided with. The current sensor provided with the core holder of any one of Claims 1 thru | or 3.

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