WO2009151011A1

WO2009151011A1 - Current sensor

Info

Publication number: WO2009151011A1
Application number: PCT/JP2009/060366
Authority: WO
Inventors: 賢二坂脇; 哲郎石川; 正和小林
Original assignee: 株式会社タムラ製作所
Priority date: 2008-06-10
Filing date: 2009-06-05
Publication date: 2009-12-17
Also published as: JP4814283B2; JP2009300123A

Abstract

A current sensor is provided with an annular core wherein a gap is formed, an electromagnetic conversion element arranged in the gap, and a grounded shield means which electrostatically shields the electromagnetic conversion element. The core has first and second end surfaces defining the boundary of the gap, the electromagnetic conversion element has first and second sensing surfaces, and the first and the second sensing surfaces are arranged to face the first and the second end surfaces, respectively. The shield means has a first section covering the first sensing surface, a second section covering the second sensing surface and a support section which supports the first section and the second section. The current sensor is also provided with a first pressing means. The first pressing means is arranged between the first section of the shield means and the first end surface of the core, and presses the first section and the first end surface so as to carry electricity between the core and the shield means.

Description

Current sensor

The present invention relates to a current sensor using a magnetoelectric conversion element.

As a current sensor for detecting the magnitude of a current, one using a magnetoelectric conversion element such as a Hall element that converts a magnetic field generated by the current into an electromotive force is widely used. Many of such current sensors have an annular core, and when a current is passed through an electric wire passing through a hole in the core, a magnetic flux that circulates in the core along the circumferential direction of the core is generated. Since the magnetic flux density of this magnetic flux is substantially proportional to the magnitude of the current flowing through the electric wire, the magnitude of the current flowing through the electric wire can be measured by detecting the magnetic flux density with a magnetoelectric transducer.

In order to accurately measure the magnetic flux density, the magnetoelectric conversion element used in such a current sensor is electrostatically shielded by a shield member so that the element is not exposed to an electrostatic field from another adjacent electric circuit. Is desirable. An example of a shield member for electrostatically shielding a magnetoelectric conversion element is described in Patent Document 1 below. The shield member for a magnetoelectric conversion element described in Patent Literature 1 is a metal plate bent in a handle shape, and an element storage portion (a portion corresponding to the handle of a handle) bent in a U shape, and an element storage portion It is comprised from the flat-shaped attachment part (part corresponding to the handle of a handle) extended from one end. In addition, the element storage portion includes a rectangular bottom portion and a pair of side portions bent at substantially right angles at the long sides of the bottom portion. The inside of the element housing part is formed in a shape corresponding to the outer shape of the package body of the Hall element, and each side part of the element housing part converts each magnetosensitive surface of the Hall element (the magnetic current passing through the magnetosensitive surface is converted into a magnetoelectric conversion). The element housing portion of the shield member is put on the package body of the Hall element so that the element is detected.

The shield member can hold the package body of the Hall element between the pair of side portions of the element storage portion when the element storage portion is put on the package body of the Hall element. Therefore, the shield member can be attached to the wiring board in a state where the element housing portion is put on the package body of the Hall element. The shield member is soldered to the wiring board at the contact portion between the ground pad provided on the wiring board and the mounting part in a state where the mounting part is in contact with the wiring board. Further, when the element housing portion is put on the Hall element, the magnetic sensing surface can be positioned in the direction perpendicular to the wiring board by sandwiching the package body of the Hall element to the back of the element housing portion of the shield member. . Thus, the shield member described in Patent Document 1 functions not only as an electrostatic shield for the magnetoelectric conversion element but also as a member for positioning.

The above current sensor is a small one that is slightly larger than the core. However, in the current sensor having such a configuration, when the potential on the primary side (that is, the potential of the electric wire for measuring the current) rapidly changes, the potential of the core fluctuates due to electrostatic coupling. As a result, the potential of the magnetoelectric conversion element also fluctuates, and noise is added to the electrical signal output from the magnetoelectric conversion element, so that the magnitude of the current cannot be accurately measured. In order to solve this problem, it is necessary to ground the core. However, in this case, it is necessary to add a mechanism for grounding the core to the current sensor separately, which increases the size of the current sensor, increases the number of parts, and consequently increases the number of assembly steps of the current sensor. Will be invited. Thus, in a conventional current sensor, when measuring a current flowing through a conductor whose potential changes abruptly, such as a three-phase motor drive circuit, the current sensor is large, has a large number of parts, and has a large number of assembly steps. I had to choose.

JP 2005-024519 A

The present invention has been made in view of the above problems in the prior art. That is, according to the embodiment of the present invention, a current sensor capable of accurately measuring the magnitude of a high-voltage alternating current is provided without substantially increasing the number of parts and man-hours.

According to an embodiment of the present invention, there is provided a current sensor including an annular core having a gap formed therein, a magnetoelectric conversion element disposed in the gap, and a grounded shield means for electrostatically shielding the magnetoelectric conversion element. The The core has first and second end faces that define a gap boundary, the magnetoelectric transducer has first and second sensing faces, and the first and second sensing faces face the first and second end faces, respectively. Are arranged as follows. The shield means has a first part that covers the first sensing surface, a second part that covers the second sensing surface, and a support part that supports the first part and the second part. The current sensor further includes first compression means. The first compression means is disposed between the first part of the shield means and the first end face of the core, and presses the first part and the first end face to make the core and the shield means conductive.

Thus, according to the embodiment of the present invention, the core can be grounded by a simple configuration in which the first compression means is provided between the shield means and the core. Therefore, according to the embodiment of the present invention, a small-sized current sensor corresponding to high-voltage alternating current can be realized with almost no increase in the number of parts and man-hours.

Preferably, a part of the shielding means forms the first compression means. For example, the first compression means may be a leaf spring-like member formed by bending a part of the first part of the shielding means toward the first end surface of the core. According to such a configuration, the number of parts and man-hours are not increased at all. A small current sensor corresponding to high voltage alternating current is realized.

The first compression means may be a conductive elastic member sandwiched between the first part of the shield means and the first end face of the core.

The current sensor may further include a wiring board to which the shield means and the magnetoelectric conversion element are connected.

The current sensor may further include a case for accommodating the wiring board, the core, the magnetoelectric conversion element, the shielding means, and the first pressing means. In this case, it is preferable that the case has holding means for holding the substrate and the core.

The current sensor may further include a second compression means. In this case, the second compression means may be disposed between the second part of the shield means and the second end face of the core, and may press the second part and the second end face to make the core and the shield means conductive. . Moreover, a part of shield means may form a 2nd compression means. In this case, the second compression means is preferably a leaf spring-like member formed by bending a part of the second part of the shield means toward the second end surface of the core. The second compression means may be a conductive elastic member that is sandwiched between the second part of the shield means and the second end face of the core. In this case, the first and second compression means may be integrated to form an elastic member having a U-shaped cross section.

1 is a schematic perspective view of a current sensor according to an embodiment of the present invention. It is A arrow directional view of FIG. It is the schematic perspective view which looked at the shielding member which concerns on embodiment of this invention from the front side of FIG. It is the schematic perspective view which looked at the shield member which concerns on embodiment of this invention from the back side of FIG. It is the schematic side view which showed the modification of the current sensor which concerns on embodiment of this invention. It is the schematic side view which showed another modification of the current sensor which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view of a current sensor 1 according to an embodiment of the present invention. FIG. 2 is a schematic side view of the current sensor 1 according to the embodiment of the present invention, viewed from the direction of the arrow A in FIG. As shown in FIG. 1, a current sensor 1 according to an embodiment of the present invention is a case in which a substrate 20 on which a Hall element 40 is mounted and an annular core 30 are housed in a case 10. The core 30 is formed of various ferromagnetic materials, and a silicon steel plate, permalloy, a ferrite core, or the like is used. As shown in FIG. 2,

protrusions

14 a, 14 b, 15 a and 15 b are provided inside the case 10. The core 30 is gripped by the projecting

portions

14a and 14b, and the substrate 20 is gripped by the projecting

portions

15a and 15b, respectively, and positioned in the case 10.

In the current sensor 1 according to the embodiment of the present invention, the electric wire W that is the object of current measurement is passed through the hole 35 of the core 30, and the magnetic flux that circulates around the core 30 inside the core 30 due to the current flowing through the electric wire W. It is supposed to occur. At this time, the magnitude of the magnetic flux density generated in the core 30 is proportional to the magnitude of the current flowing through the electric wire W. Therefore, the magnitude of the current flowing through the electric wire W can be measured by measuring the magnetic flux density in the core 30 using the Hall element 40 which is a kind of magnetoelectric conversion element. Therefore, as shown in FIG. 2,

openings

12, 13, and 22 for passing the electric wires W through the holes 35 of the core 30 are formed in the upper and lower surfaces of the case 10 and the substrate 20, respectively.

In addition, the substrate 20 is provided with four terminals 21. The terminals 21 are connected to the lead terminals 42 of the Hall element 40 through wirings formed on the substrate 20 respectively. As shown in FIGS. 1 and 2, the terminal 21 extends in a direction parallel to the substrate 20, and an opening 11 for allowing the terminal 21 to pass is provided on the side surface of the case 10. That is, the tip of the terminal 21 protrudes outside the case 10, and driving power is supplied to the Hall element 40 through the terminal 21 and is output from the Hall element 40 according to the magnitude of the current flowing through the electric wire W. An electrical signal can be acquired.

As shown in FIG. 1, the Hall element 40 is a so-called SIP (Single in-line package) type package in which lead terminals 42 (four in this embodiment) extend from one surface of a rectangular package body 41. It is a mounted device. The Hall element 40 is attached to the substrate 20 such that the package body 41 is disposed substantially perpendicular to the substrate 20.

A part of the core 30 is cut out by two parallel surfaces orthogonal to the circumferential direction, and a gap 31 is formed. The hall element 40 is arranged so that the package body 41 is accommodated in the gap 31. Specifically, as shown in FIG. 2, the first magnetosensitive surface provided on both surfaces of the first end surface 32 and the second end surface 33 of the core 30 forming the gap 31 and the package body 41 of the Hall element 40. The package body 41 of the Hall element 40 is disposed in the gap 31 so that 41a and the second magnetosensitive surface 41b face each other. As a result, the magnetic flux lines that circulate in the core 30 pass through the magnetically

sensitive surfaces

41a and 41b of the Hall element 40 substantially vertically.

In the present embodiment, a clip-shaped shield member 50 is used to shield the Hall element 40 from an unnecessary electrostatic field. The shield member 50 is formed by bending a plate of a nonmagnetic conductor such as phosphor bronze. As shown in FIG. 2, the shield member 50 of the present embodiment includes a cover portion 51 that covers the first magnetic sensitive surface 41 a and the second magnetic sensitive surface 41 b of the Hall element 40, and a support portion 52 that supports the cover portion 51. It is composed of The cover portion 51 includes a first portion 51a that faces the first magnetic sensitive surface 41a, a second portion 51b that faces the second magnetic sensitive surface 41b, and a connecting portion that connects the first portion 51a and the second portion 51b. 51c.

In the present embodiment, the first portion 51a and the connecting portion 51c are substantially perpendicular. On the other hand, the second portion 51b and the connecting portion 51c form an angle slightly smaller than a right angle. For this reason, the space | interval of the 1st part 51a and the 2nd part 51b becomes small as it distances from the connection part 51c. Minimum distance d ₁ between the first part 51a and second part 51b is set smaller than the thickness of the package body 41 in a natural state. Therefore, when inserting the package body 41 to the cover portion 51, second portion 51b is moved counterclockwise in FIG. 2, spreads distance d _1. At this time, the package body 41 is sandwiched between the first portion 51a and the second portion 51b by the elastic force generated in the second portion 51b, and is held by the shield member 50 so as not to move easily. Further, as described above, since the first portion 51a is substantially perpendicular to the connecting portion 51c, when the package main body 41 is fully inserted into the cover portion 51, the upper surface 41c of the package main body 41 becomes the inner surface of the connecting portion 51c (FIG. 2). The first magnetosensitive surface 41a contacts the inner surface (the right side in the drawing) of the first portion 51a. Thus, the Hall element 40 can be positioned with respect to the shield member 50 by bringing the package body 41 into contact with the inner surface of the cover portion 51.

The support part 52 is connected to the front-end | tip (lower end in FIG. 2) of the 1st part 51a. The support portion 52 is bent at an obtuse angle in the middle, and the tip of the bent portion is a tip portion 52a fixed to the substrate 20 at the time of mounting. The shield member 50 is also bent at an obtuse angle at the connecting portion between the first portion 51a and the support portion 52, and the tip portion 52a is perpendicular to the first portion 51a. Therefore, when the front end portion 52 a of the support portion 52 is placed on the substrate 20, the first portion 51 a is substantially perpendicular to the substrate 20. Thereby, the package main body 41 is disposed substantially perpendicular to the substrate 20 at the time of mounting. As described above, since the shield member 50 and the substrate 20 are positioned by fixing the front end portion 52a of the support portion 52 on the substrate, the Hall element 40 positioned by the shield member 50 is also included in the substrate 20. Will be positioned. Thus, the shield member 50 has a function as a positioning member for positioning the Hall element 40 with respect to the substrate 20.

One of the four terminals 21 on the substrate 20 is a ground terminal, and a ground pad 23 connected to the ground terminal is formed on the surface of the substrate 20 (FIG. 1). As shown in FIG. 2, the shield member 50 can be grounded by bringing the tip 52 a of the support portion 52 of the shield member 50 into contact with the ground pad 23 and soldering to the ground pad 23. As a result, the Hall element 40 is protected from an unnecessary electrostatic field that causes an error in current detection.

The shield member 50 of the current sensor 1 according to the present embodiment has a function of shielding and positioning the Hall element 40 and grounding the core 30. For example, when the potential of the core 30 changes due to an electric field applied from the outside, the magnetic flux density in the core 30 changes accordingly. This change in magnetic flux density causes an error in current measurement. In the configuration of the present embodiment, since the core 30 is maintained at the ground potential, there is no error due to the external electric field, and the amount of current flowing through the electric wire W can be accurately calculated from the magnetic flux density in the core 30. This is particularly effective in an environment where the potential in the core 30 can change greatly due to electrostatic coupling of the core 30, the electric wire W, and the substrate 20, for example, when a high-voltage alternating current is applied to the electric wire W.

Next, the grounding function of the core 30 by the shield member 50 will be described. FIG. 3 is a schematic perspective view of the shield member 50 according to the embodiment of the present invention as viewed from the front side of FIG. FIG. 4 is a schematic perspective view of the shield member 50 according to the embodiment of the present invention as viewed from the back side of FIG. 3 and 4, a part of the first portion 51a of the shield member 50 is cut into a U-shape and is drawn outward (left side in FIGS. 3 and 4). 53 is formed. In addition, a second compression portion 54 that is cut out in a U shape and pulled out to the outside (right side in FIGS. 3 and 4) is formed in a part of the second portion 51 b of the shield member 50. Here, the distance d ₂ between the tip portions of the first compression portion 53 and the second compression portion 54 in the natural state is the width of the gap 31 of the core 30, that is, the interval between the first end surface 32 and the second end surface 33. It is formed so as to be larger than d ₃ (FIG. 1). For this reason, when the cover portion 51 of the shield member 50 is inserted into the gap 31, the first compression portion 53 and the second compression portion 54 are pushed inward by the first end surface 32 and the second end surface 33 of the core 30, respectively. At this time, the first end surface 32 and the second end surface 33 of the core 30 are compressed by the elastic force generated in the both compression portions. As a result, the first pressing portion 53 and the second pressing portion 54 are in close contact with the first end surface 32 and the second end surface 33, respectively, so that the core 30 and the shield member 50 are in contact with each other on the two surfaces and are reliably conducted. Become. Further, since the shield member 50 is soldered to the ground pad 23 of the substrate 20 as described above, the potential of the core 30 is kept at the ground potential.

In the current sensor 1 according to the present embodiment described above, a part of the first portion 51a and the second portion 51b of the shield member 50 is formed to press the core 30 as a kind of leaf spring. However, the present invention is not limited to this configuration. That is, the compression part does not necessarily need to be provided on both the first part side and the second part side of the shield member 50, and the compression part may be provided only on one of them.

Alternatively, the core 30 may be pressed by another configuration to make the shield member 50 and the core 30 conductive. For example, as shown in FIG. 5, a plate-like conductive member 53 is provided between the first part 51 a of the shield member 50 and the first end face 32 of the core 30 and between the second part 51 b and the second end face 33. A configuration in which ', 54' is sandwiched may be employed. Further, as shown in FIG. 6, a conductive member 55 having a U-shaped cross section in which the conductive members 53 ′ and 54 ′ of FIG. 5 are integrated may be disposed in the gap 31.

Further, as shown in FIG. 4, the width of the cover portion 51 of the shield member 50 and the width of the tip portion 52 a of the support portion 52 are equal. However, the width of the tip 52a may be narrower than the width of the cover 51. In this configuration, since the tip end portion 52a is small, it is easy to solder the tip portion 52a to the ground pad 23 (FIGS. 1 and 2).

DESCRIPTION OF SYMBOLS 1 Current sensor 10 Case 20 Board | substrate 21 Terminal 23 Ground pad 30 Core 31 Gap 32 1st end surface 33 2nd end surface 35 Hole 40 Hall element 41 Package main body 41a 1st magnetosensitive surface 41b 2nd magnetosensitive surface 50 Shield member 51 Cover part 51a 1st part 51b 2nd part 52 Support part 53 1st compression part 54 2nd compression part W Electric wire

Claims

An annular core with a gap formed;
A magnetoelectric transducer disposed in the gap;
A current sensor comprising a grounded shield means for electrostatically shielding the magnetoelectric transducer;
The core has first and second end faces that delimit the gap,
The magnetoelectric conversion element has first and second sensing surfaces, and the first and second sensing surfaces are arranged so as to face the first and second end surfaces, respectively.
The shielding means includes
A first part covering the first sensing surface;
A second part covering the second sensing surface;
A support part for supporting the first part and the second part,
The current sensor further comprises first compression means,
The first compression means is disposed between the first part of the shield means and the first end face of the core, and presses the first part and the first end face to conduct the core and the shield means. A current sensor.
The current sensor according to claim 1, wherein a part of the shield means forms the first compression means.
The said 1st compression means is a leaf | plate spring-like member formed by bending a part of 1st part of the said shield means toward the 1st end surface of the said core. Current sensor.
The current sensor according to claim 1, wherein the first compression means is a conductive elastic member sandwiched between the first part of the shield means and the first end face of the core.
The current sensor according to claim 1, further comprising a wiring board to which the shield means and the magnetoelectric transducer are connected.
A case for accommodating the wiring board, the core, the magnetoelectric conversion element, the shield means, and the first compression means;
The current sensor according to claim 5, wherein the case includes a holding unit that holds the substrate and the core.
The current sensor further comprises second compression means;
The second compression means is disposed between the second part of the shield means and the second end face of the core, and presses the second part and the second end face to conduct the core and the shield means. The current sensor according to claim 1, wherein:
The current sensor according to claim 7, wherein a part of the shield means forms the second compression means.
The said 2nd compression means is a leaf | plate spring-shaped member formed by bending a part of 2nd part of the said shield means toward the 2nd end surface of the said core. Current sensor.
The current sensor according to claim 7, wherein the second compression means is a conductive elastic member sandwiched between the second part of the shield means and the second end face of the core.
The first compression means is a conductive elastic member sandwiched between the first part of the shield means and the first end face of the core,
The current sensor according to claim 10, wherein the first and second compression means are integrated to form a U-shaped member.