JP4814283B2 - Current sensor - Google Patents

Description

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

  As a current sensor for detecting the magnitude of current, one using a magnetoelectric conversion element such as a Hall element is widely used. Such a current sensor has an annular core, and when a current is passed through an electric wire passed through the hole of 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 measure the magnetic flux density more accurately, the magnetoelectric conversion element used in such a current sensor may be shielded by a shield member so that the element is not exposed to an electrostatic field from other nearby electronic circuits. desirable. An example of such a shield member for the magnetoelectric conversion element is described in Patent Document 1. The shield member for a magnetoelectric conversion element described in Patent Document 1 is formed by bending a metal plate into a U shape so that a surface through which a magnetic flux detected by the magnetoelectric conversion element passes (a magnetosensitive surface) is covered. It is attached. One end portion of the shield member is bent so as to be substantially parallel to the substrate on which the element is mounted, and comes into contact with a ground pad provided on the substrate and is soldered at the contact portion. It has become.
JP 2005-024519 A

  Further, this shield member can hold the magnetoelectric conversion element at the U-shaped portion. For this reason, the magnetoelectric conversion element can be positioned with respect to the shield member in the direction perpendicular to the tip of the shield member (that is, the normal direction of the substrate) by inserting the magnetoelectric conversion element to the back of the U-shaped portion. As described above, the shield member of Patent Document 1 functions not only as a shield of the magnetoelectric conversion element but also as a member for positioning.

  The current sensor having the above configuration is a small sensor having a size slightly larger than the core. However, in the current sensor having the above configuration, when the potential on the primary side changes abruptly, the core potential is shaken by electrostatic coupling, and noise in the normal mode is generated in the electric circuit, which outputs noise to the sensor. There was a problem that the magnitude of the current could not be measured accurately. 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, the number of parts, and the increase in 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.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a current sensor that can accurately measure the magnitude of a high-voltage alternating current without substantially increasing the number of parts and man-hours.

In order to achieve the above object, a current sensor according to the present invention includes a magnetoelectric conversion element mounted on a substrate so that a magnetosensitive surface is substantially perpendicular to the substrate, an annular core having a gap formed therein, A first part that covers one of the magnetic sensitive surfaces and a second part that is connected to the first part and covers the other of the magnetic sensitive surfaces, extends from one of the first part and the second part, and is connected to a ground pad on the substrate. The shield means having the third part, and is disposed between the first end part and the first part facing the first part among the both end faces constituting the gap in the core, and is connected to the first part And a first pressing means for compressing the first end face and electrically connecting the core and the shielding means.
It is more preferable that a leaf spring-like member formed by bending the first portion toward the first end face is used as the first compression means.

  As described above, according to the present invention, the potential of the core can be dropped to the ground only by providing the first pressing means between the shield means and the core, and the number of parts and man-hours are almost increased. A small current sensor corresponding to high-voltage alternating current can be realized without any problems. In particular, when a leaf spring-like member formed by bending the first portion toward the first end surface is used as the first compression means, the above-described current sensor can be realized without increasing the number of steps and the number of parts.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a current sensor according to an embodiment of the present invention. FIG. 2 is a view taken in the direction of arrow A in FIG. As shown in FIG. 1, the current sensor 1 of the present embodiment 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. 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 guided and held by the protrusions 14a and 14b, and the substrate 20 is held by the protrusions 15a and 15b.

  In the current sensor 1 of the present embodiment, the electric wire W is passed through the hole 35 of the core 30, and a current flows through the electric wire W to generate a magnetic flux that goes around the core 30 inside the core 30. Since the magnitude of the magnetic flux is proportional to the magnitude of the current flowing through the electric wire W, the current flowing through the electric wire W is measured by measuring the magnetic flux density of the magnetic flux in the core 30 by the Hall element 40 which is a kind of magnetoelectric conversion element. Can be measured. For this reason, 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 or the substrate 20.

  The substrate 20 is provided with four terminals 21 for supplying electric power for driving the Hall element 40 and outputting a current measurement result. 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 through is provided on a 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 the magnitude of the current flowing through the electric wire W can be acquired.

  As shown in FIG. 1, the Hall element 40 is a so-called SIP (System-in-package) -shaped device in which four lead terminals 42 extend from one end surface of a rectangular plate-shaped package body 41. 41 is mounted on the substrate 20 so as to be arranged substantially perpendicular to the substrate 20.

  A part of the core 30 is cut away by two mutually parallel surfaces orthogonal to the circumferential direction, and a gap 31 is formed. The hall element 40 is disposed so as to be 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 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 Hall element substantially perpendicular to the magnetic sensitive surfaces 41a and 41b of the Hall element 40.

  In the present embodiment, a clip-shaped shield member 50 is used to shield the Hall element 40 from an unnecessary electromagnetic 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 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. The cover portion 51 is in contact with the first portion 51a facing the first magnetic sensitive surface 41a, the second portion 51b facing the second magnetic sensitive surface 41b, the upper surface of the package body 41 of the Hall element 40, and the first portion 51a. It has the connection part 51c which connects the part 51a and the 2nd part 51b.

The first part 51a is substantially perpendicular to the connecting part 51c. On the other hand, the angle formed by the second part 51b and the connecting part 51c is 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 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 in the counterclockwise direction in FIG. 2, spreads distance d _1. At this time, the package body 41 is sandwiched between the first part 51a and the second part 51b by the elastic force generated in the second part 51b, and is held by the shield member 50 so as not to move easily. Further, as described above, the first portion 51a is substantially perpendicular to the connecting portion 51c, and therefore the upper surface 41c of the package body 41 is connected to the connecting portion 51c when the package main body 41 is fully inserted into the cover portion 51. The first magnetosensitive surface 41a contacts the inner surface (right side in FIG. 2) 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.

  A third portion 52 extends toward the substrate 20 from the tip of the first portion 51a (the lower portion in FIG. 2). The third portion 52 is bent in the middle thereof, and the tip portion 52a faces a direction substantially orthogonal to the first portion 51a. Therefore, when the tip end portion 52 a of the third portion 52 is brought into contact with the substrate 20, the first portion 51 a is substantially perpendicular to the substrate 20. Thus, since the shield member 50 and the substrate 20 are positioned by the contact between the tip 52a of the third portion 52 and the substrate, the Hall element 40 positioned by the shield member 50 is also used by 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 third portion 52 of the shield member 50 into contact with the ground pad 23 and soldering to the ground pad 23. Thus, the Hall element 40 is protected from an unnecessary electrostatic field that causes a current detection error.

  The shield member 50 of the current sensor 1 according to the present embodiment functions to shield and position the Hall element 40 and to ground the potential of the core 30. Although the magnitude of the magnetic flux in the core 30 changes as the potential of the core 30 changes, in the configuration of the present embodiment, the core 30 is kept at the ground potential. The magnitude of the current flowing through W can be accurately calculated. 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 the current flowing through the electric wire W is a high-voltage AC current.

The grounding function of the core 30 by the shield member 50 will be described below. FIG. 3 is a perspective view of the shield member 50 according to the present embodiment as viewed from the front side of FIG. FIG. 4 is a perspective view of the shield member 50 according to the present embodiment as viewed from the back side of FIG. As shown in FIGS. 3 and 4, a part of the first portion 51a of the shield member 50 is cut into a U-shape and pulled out to the outside (upper left in FIG. 3, lower left in FIG. 4). One compression part 53 is formed. Further, a part of the second portion 51b of the shield member 50 is formed with a second compression portion 54 that is cut into a U-shape and pulled out to the outside (lower right side in FIG. 3, upper right side in FIG. 4). ing. Here, the distance d ₂ between the distal ends 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 distance d ₃ between the first end surface 32 and the second end surface 33 ( It is formed to be larger than FIG. For this reason, when the cover part 51 of the shield member 50 is inserted into the gap 31, the first pressing part 53 and the second pressing part 54 are each pushed inward. At this time, the first end face 32 and the second end face 33 are pressed by the elastic force generated in the both pressing 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, as described above, since the shield member 50 is soldered to the ground pad 23 of the substrate 20, the potential of the core 30 is maintained at the ground potential.

  In the current sensor 1 of the present embodiment described above, a part of the first part 51a and the second part 51b of the shield member 50 presses 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.

  Or it is good also as a structure which presses the core 30 with another structure, and makes the shield member 50 and the core 30 electrical conduction. For example, as shown in FIG. 5, a plate-shaped conductive material 53 ′ between the first portion 51a of the shield member 50 and the first end surface 32 of the core 30 and between the second portion 51b and the second end surface 33, A configuration in which 54 'is sandwiched may be employed. Further, as shown in FIG. 6, a conductive material 55 having a U-shaped cross section in which the conductive materials 53 ′ and 54 ′ of FIG. 5 are integrated may be arranged in the gap 31.

  Further, as shown in FIG. 4, the width of the cover portion 51 of the shield member 50 is equal to the width of the tip portion 52 a of the third portion 52. However, the width of the tip 52a may be smaller 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).

1 is a 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 perspective view which looked at the shield member by embodiment of this invention from the front side of FIG. It is the perspective view which looked at the shield member by embodiment of this invention from the back side of FIG. It shows another example of the current sensor according to the embodiment of the present invention. The another example of the current sensor of embodiment of this invention is shown.

Explanation of symbols

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 3rd part 53 1st compression part 54 2nd compression part W Electric wire

Claims (6)

A substrate,
A magnetoelectric conversion element mounted on the substrate such that the magnetic sensitive surface is substantially perpendicular to the substrate;
An annular core in which a gap is formed;
A first portion covering one of the magnetic sensitive surfaces; a second portion connected to the first portion and covering the other of the magnetic sensitive surfaces; and extending from one of the first and second portions to a ground on the substrate Shielding means having a third part connected to the pad;
Of the two end surfaces constituting the gap in the core, the first end surface is disposed between the first end surface facing the first portion and the first portion, and is connected to the first portion and presses the first end surface. First compression means for conducting the core and the shield means;
A current sensor.   2. The current sensor according to claim 1, wherein the first compression unit is a leaf spring-like member formed by bending a part of the first part toward the first end surface.   Of the both end faces constituting the gap in the core, the second end face is arranged between the second end face facing the second part and the second part, and is connected to the second part and presses the second end face. The current sensor according to claim 2, further comprising second compression means for conducting the core and the shield means.   2. The current sensor according to claim 1, wherein the first compression unit is a conductive elastic member sandwiched between the first part and the first end surface.   The elastic member is a member having a U-shaped cross-sectional shape that is also sandwiched between the second portion and the second end surface facing the second portion of the two end surfaces constituting the gap in the core. The current sensor according to claim 4.   6. The current sensor according to claim 1, further comprising holding means for holding the substrate and the core so that the magnetoelectric conversion element is disposed in the gap.

Images