JP2018163051A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which allows for improving measurement accuracy, minimizing temperature rise, and enhancing product value.SOLUTION: A current detector 100 comprises: a case body 102 having an insertion hole 104 for a busbar Bh to be inserted formed through an inner part thereof, and an accommodating part 102g formed around the insertion hole 104 to accommodate a ring-like magnetic core 110 disposed to surround the busbar Bh and a current detection circuit; a potting resin 106 that fills and seals the accommodating part 102g with the magnetic core 110 and the current detection circuit accommodated therein; and regulation parts 102e integrally formed on a wall plate section 102d of the accommodating part 102g along the insertion hole 104 and configured to regulate inclination of the busbar Bh inside the insertion hole 104 and the amount of the potting resin 106 filling the accommodating part 102g.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a current detector such as a magnetic balance type or a magnetic proportional type used for current measurement.

  Conventionally, a prior art of a current sensor that eliminates an error caused by data processing of a detection signal is known (see Patent Document 1). In this prior art, a voltage from a magnetic field detection element such as a Hall element is converted to digital data by A / D conversion and then processed, thereby reducing bit errors associated with data conversion and suppressing measurement errors. . Moreover, the fin part is integrally formed with the resin case to dissipate heat and prevent an excessive temperature rise.

JP 2009-210405 A

The above prior art pays attention to the data processing error after the magnetic flux density is converted to voltage by the Hall element, and also reduces the influence of heat.
However, even if the same current to be detected flows through the conductor, if the positional relationship between the conductor and the magnetic core varies, the magnetic flux density before the voltage is converted into voltage by the Hall element will vary. To do. Further, even if the resin case has heat dissipation performance, the heat transmitted from the conductor cannot be suppressed, so that the temperature rise cannot be suppressed so much.

  Therefore, an object of the present invention is to provide a technique capable of increasing the measurement accuracy to suppress a temperature rise and further increasing the product value.

In order to solve the above problems, the present invention employs the following solutions.
In the current detector of the present invention, a restriction part is integrated with the case body. The case body has an insertion hole formed inside, and a housing portion is formed around the insertion hole. The insertion hole is a through portion for inserting a conductor, and the accommodating portion is a portion that accommodates and holds the magnetic core and the current detection circuit. The inside of the housing portion is filled and sealed with a resin sealing body.

  The restriction portion is integrated with a portion constituting the wall of the housing portion along the insertion hole of the case body. The restricting portion has different restrictions on the inside of the insertion hole (outside of the case body) and the inside of the accommodating portion (inside of the case body). That is, the restricting portion restricts the inclination of the conductor with respect to the insertion direction by bringing the outer surface of the case body close to the conductor in the insertion hole. On the other hand, the regulating portion conversely separates the inner surface of the case main body from the conductor in the accommodating portion. As a result, the restricting portion brings the inner surface of the case main body close to the magnetic core, thereby restricting the filling range (filling amount, volume) of the sealing body in the accommodating portion.

  As a result, the positional relationship between the conductor inserted through the insertion hole and the magnetic core accommodated in the accommodating portion is kept constant, so that not only the detection (measurement) accuracy by the current detection circuit can be improved, but also the case The product weight (mass) can be kept low by suppressing the filling amount of the sealing body into the main body (housing portion). Even if the outer surface of the case main body is close to the conductor, the inner surface of the case main body is separated from the conductor, so that the influence of heat transmitted from the conductor on the internal current detection circuit and the like can be reduced.

  Preferably, the restriction part includes a plurality of plate-like pieces and is close to the conductor at the leading edge of the plate-like piece. Thereby, the area which a conductor and a case main body contact can be decreased, and it can be set as the shape which cannot receive the influence of a heat | fever from a conductor. In addition, a large total surface area of the case body can be ensured by the plurality of plate-like pieces, and the heat dissipation effect can be enhanced.

  Moreover, in the accommodating part, the site | part which comprises a wall around a magnetic body core is made into a step shape, and it adjoins to a magnetic body core, and the filling range of a sealing body is controlled. The portion constituting the wall of the housing portion reduces (regulates) the filling amount of the sealing body over the entire circumference of the insertion hole by the amount close to the magnetic core in a stepped shape, which can greatly contribute to the reduction of the product weight. .

  Furthermore, when it has the installation surface which fixes a case main body to a target object, it is set as the shape which contacts a target object in the edge of a some plate-shaped piece within a setting surface. Thereby, it is possible to prevent heat from the heat-generating component of the current detection circuit from being trapped between the installation surface and the object, and to improve the heat radiation efficiency by the plate-like piece.

  According to the present invention, it is possible to enhance the measurement accuracy and suppress the temperature rise, and further increase the product value by reducing the total weight.

It is the schematic which shows the structure of the current detector of one Embodiment. It is the schematic which shows the structure of the current detector of one Embodiment. It is a disassembled perspective view of a current detector. It is the rear view which showed the electric current detector in the installation state. FIG. 5 is a horizontal sectional view of the current detector taken along line VV in FIG. 4. It is a horizontal sectional view of the current detector used as comparative example (1). It is a horizontal sectional view of the current detector used as comparative example (2). It is a perspective view which shows the shape of the bottom face of an electric current detector.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are schematic diagrams illustrating a configuration of a current detector 100 according to an embodiment. FIG. 1 is a perspective view showing the current detector 100 from the front side, and FIG. 2 is a perspective view showing from the back side.
Hereinafter, the configuration of the current detector 100 will be described.

[Case body]
The current detector 100 includes a case body 102 made of resin, for example. The case main body 102 constitutes an external form of the current detector 100, and a conductor (not shown) through which a current to be detected, which is the main purpose, is inserted, or for any object (also not shown). It performs a fixed function. The case body 102 contains a magnetic core and a current detection circuit (not shown in FIGS. 1 and 2). The inside of the case body 102 is filled and sealed with a potting resin 106 (sealing body). Has been.

  The case main body 102 has an approximately ring shape as a whole, and an insertion hole 104 is formed through the center portion in the thickness direction (front-rear direction). In the standing posture shown in FIGS. 1 and 2, a curved portion is conspicuous on the upper surface of the case body 102, but the bottom surface has a shape based on a flat surface. Moreover, in addition to having a portion of a vertically long plane in addition to the curved portion of the upper surface, both side surfaces have a shape in which a plurality of plate-like pieces 102f are vertically arranged at intervals.

  The case main body 102 is formed with an upper bracket 102a, a bottom plate bracket 102b, a lower bracket 102c, and the like that form a pair to be fixed to an object (such as a casing of a device through which a current to be detected flows) as described above. ing. The upper bracket 102a and the lower bracket 102c are respectively positioned at the four corners on the outer side of the case main body 102 with the insertion hole 104 at the center. Further, the pair of bottom plate brackets 102b on both sides extend in a blade shape from the bottom surface of the case body 102 toward both sides.

  Among these, the upper bracket 102a and the lower bracket 102c are used when the case main body 102 is fixed to an object on the back surface. The bottom plate bracket 102b is used when the case main body 102 is fixed to an object on the bottom surface. In any case, each bracket 102a, 102b, 102c is formed with a hole through which any fastener (bolt, nut, boss, etc.) can be inserted.

(Sealed body)
As shown in FIG. 1, the potting resin 106 is filled in the case main body 102, and the surface of the potting resin 106 occupies most of the front surface of the case main body 102 (current detector 100). The potting resin 106 seals the magnetic core and current detection circuit accommodated in the case main body 102, and blocks entry of dust, moisture, and the like. A connector 108 projects from the front surface of the current detector 100.

  Around the insertion hole 104, the case main body 102 is constituted by a wall plate portion 102d and a restricting portion 102e. Of these, the wall plate portion 102 d forms a substantially octagonal peripheral wall on the front side of the case main body 102. One restricting portion 102e is composed of a plurality of plate-like pieces arranged in the circumferential direction on the back side of the case main body 102, whereas the insertion hole 104 has a smooth peripheral wall surface in the wall plate portion 102d. In the restricting portion 102e, the insertion hole 104 has an uneven peripheral wall surface.

[Magnetic core]
FIG. 3 is an exploded perspective view of the current detector 100. As described above, the current detector 100 includes the magnetic core 110 and the current detection circuit, which are accommodated in the case main body 102. For this reason, the housing portion 102 g is formed in the case body 102 in a concave shape from the front side to the back side, and the housing portion 102 g as a whole forms a ring around the insertion hole 104. The magnetic core 110 is accommodated in the accommodating portion 102g so as to surround the insertion hole 104. In this embodiment, the magnetic core 110 is a type having the secondary winding 110c, and most of the outer shape shown in FIG. 3 is occupied by the secondary winding 110c. The magnetic core 110 has a ring core made of a magnetic material (for example, a toroidal ring: not visible in FIG. 3) inside the secondary winding 110c, and an air gap is formed in a part thereof. A hall element (not shown) is arranged in the air gap via a spacer 110a.

[Current detection circuit]
The current detector 100 includes a base plate 112 and a circuit board 114, and the base plate 112 and the circuit board 114 are also housed in the housing portion 102 g of the case body 102 together with the magnetic core 110. A current detection circuit is formed on the circuit board 114 by mounting various electronic components together with the connector 108 and the Hall element.

  The base plate 112 has an opening 112a at the center, and the wall plate portion 102d around the insertion hole 104 can be received in the opening 112a. In addition, the circuit board 114 has a notch (no symbol) matched with the opening 112 a of the base plate 112. The base plate 112 is positioned between the magnetic core 110 and the circuit board 114 in the accommodating portion 102g, and the magnetic core 110 and the circuit board 114 are attached to the base plate 112 from both sides. Then, by fixing the base plate 112 to the case body 102, the magnetic core 110 and the circuit board 114 are positioned in the housing portion 102 g via the base plate 112. Although illustration of the potting resin 106 is omitted in FIG. 3, the potting resin 106 is filled in the remaining gap in a state where the magnetic core 110, the base plate 112, and the circuit board 114 are all accommodated in the accommodating portion 102g. Has become.

[Installation form]
FIG. 4 is a rear view showing the current detector 100 in an installed state. As described above, the current detector 100 can be installed on the bottom surface of the case main body 102 with respect to the casing S of the object through which the current to be detected flows (generates a current). In this case, the bottom surface of the case body 102 serves as an installation surface, and the case body 102 can be fixed to the housing S via a pair of bottom plate brackets 102b on both sides.

〔conductor〕
As conductors through which the current to be detected flows, there are flat bus bars Bh, Bv and round bar bus bars Br indicated by two-dot chain lines in FIG. The bus bar Bh can be inserted horizontally into the insertion hole 104, the bus bar Bv can be inserted vertically, or the bus bar Br can be inserted through the entire opening.

  As shown in FIG. 4, when the bus bar Bh is inserted horizontally through the insertion hole 104, both end faces (small end faces) are in contact with the left and right regulating portions 102e, and the bus bar Bh is vertically connected. When inserted, the upper and lower end surfaces (small end surfaces) are in contact with the upper and lower restricting portions 102e. Further, when the round bar-shaped bus bar Br is inserted into the insertion hole 104, the outer peripheral surface of the bus bar Br is in contact with the restricting portions 102e at four positions that are exactly the octagonal hypotenuses.

[Regulated parts]
FIG. 5 is a horizontal sectional view of the current detector 100 taken along the line VV in FIG. Here, the horizontal cross section is taken as an example to explain the maintenance of the positional relationship between the bus bar Bh and the magnetic core 110, but the same applies to the vertical cross section and the oblique 45 ° cross section. In FIG. 5 and subsequent figures, illustration of the base plate 112 and the circuit board 114 is omitted.

[Inside insertion hole (outside case body)]
As described above, the case main body 102 includes the wall plate portion 102d and the restriction portion 102e around the insertion hole 104, and the bus bar Bh inserted through the insertion hole 104 is connected to the current detector 100 (case main body 102). The front side (upward in FIG. 5) is in contact with the wall plate portion 102d, and the back side is in contact with the regulating portion 102e. At this time, since the wall plate portion 102d and the restricting portion 102e are continuously connected to the side surface of the bus bar Bh when viewed in the insertion direction, the inclination of the bus bar Bh with respect to the insertion direction is restricted. Thereby, the positional relationship between the bus bar Bh and the magnetic core 110 is kept constant.

[Electrical characteristics]
The magnetic core 110 has the ring core 110a made of a magnetic material and the secondary winding 110b as described above. In particular, when the distances CL and CR from the bus bar Bh to the ring core 110a vary, the electrical characteristics (ring core 110a The magnetic flux density that converges at (1) varies, and the current detection value using the Hall element also varies.
In this regard, in the present embodiment, the wall plate portion 102d and the restricting portion 102e can prevent the bus bar Bh from being displaced, and the positional relationship (distance CL, CR) between the bus bar Bh and the ring core 110a can be kept constant. Therefore, the measurement accuracy by the current detector 100 can be improved.

[Inside housing (inside case body)]
On the other hand, when attention is paid to the inside of the case main body 102, the restriction portion 102e conversely separates the inner surface of the case main body 102 from the bus bar Bh. This is because, since the regulating portion 102e has a plate-like piece shape, the inner surface of the case body 102 is necessarily separated from the bus bar Bh in order for the leading edge thereof to be flush with the wall plate portion 102d. This is because it is necessary to secure a distance for extending in a plate shape to some extent. The fact that the regulating portion 102e separates the inner surface of the case main body 102 from the bus bar Bh means that the inner surface of the case main body 102 is closer to the magnetic core 110 than the wall plate portion 102d in the housing portion 102g. The inner surface of the case main body 102 (part constituting the wall) is offset in a stepped manner by the proximity distance F. As a result, the filling range (filled space and volume) of the potting resin 106 is regulated (reduced) between the inner surface of the case main body 102 and the magnetic core 110 in the housing portion 102g, and the potting resin 106 is filled as a whole. The amount will be suppressed.

  The restriction of the filling range of the potting resin 106 by the restriction part 102e as described above (suppression of the filling amount) becomes clear by comparison with the following comparative example.

[Comparative Example (1)]
FIG. 6 is a horizontal sectional view of a current detector 1000 as a comparative example (1). The current detector 1000 of the comparative example (1) does not have the restriction portion 102e included in the current detector 100 of the present embodiment, and the insertion hole 104 is configured by the wall plate portion 1002d throughout.

  According to the comparative example (1), since the wall plate portion 1002d is in contact with the bus bar Bh throughout the insertion hole 104, the position difference of the bus bar Bh with respect to the insertion direction can be prevented. It can be said that they are equivalent. However, in such a configuration, since the wall plate portion 1002d is only brought close to the bus bar Bh in the insertion hole 104, the wall plate portion 1002d is largely separated from the magnetic core 110 in the housing portion 102g. Therefore, the filling range of the potting resin 106 between the magnetic core 110 is expanded accordingly.

[Effects of filling range restriction]
When this embodiment is compared with the comparative example (1), the difference in the filling amount of the potting resin 106 into the case main body 102 (within the accommodating portion 102g) is obvious. That is, it can be seen that the amount of filling (total amount) of the potting resin 106 is smaller in this embodiment than in the comparative example (1), and the material cost and product mass can be reduced accordingly (cost reduction and weight reduction). This is because if the size of the bus bar Bh to be inserted and the diameter of the magnetic core 110 (which depends on the size of the current to be detected and the magnitude of the magnetic field generated thereby) are equivalent, then the insertion hole 104 and the accommodating portion 102g are naturally used. The size of the case main body 102 and the thickness of the wall plate portions 102d and 1002d are the same, so the shape of the present embodiment reliably ensures the filling amount of the potting resin 106 used in the comparative example (1). The filling amount can be kept small.

  Then, what happens if the filling amount of the potting resin 106 is simply reduced in the comparative example (1)? This will become clear in the following comparative example (2).

[Comparative Example (2)]
FIG. 7 is a horizontal sectional view of a current detector 1000 as a comparative example (2). The current detector 1000 of the comparative example (2) does not have the restriction portion 102e included in the current detector 100 of the present embodiment, but the insertion hole 104 is offset in a stepped shape from the front side to the back side. It is comprised by the wall board part 1002d.

  In the case of the comparative example (2), it can be said that the filling amount of the potting resin 106 is suppressed as compared with the comparative example (1) because the wall plate portion 1002d is certainly offset. However, since the wall plate portion 1002d is simply offset, the displacement of the bus bar Bh cannot be regulated throughout the insertion hole 104. For this reason, depending on the inclination of the bus bar Bh, the distances CL ′ and CR ′ to the ring core 110a become unstable and vary, and the electrical characteristics are not stable, so that the measurement accuracy becomes unstable.

  In the current detector 100 according to the present embodiment, the regulating portion 102e does not function only on one side, but functions on both the inside and outside of the case main body 102 (inside the insertion hole 104 and inside the accommodating portion 102g). Therefore, both improvement of measurement accuracy by stabilization of electrical characteristics and weight reduction of product weight (total mass) are achieved at once. In addition, since the outer surface of the case main body 102 is in linear contact with the bus bar Bh (contacts at the tip edge of the plate-like piece) in the restricting portion 102e, the heat generated by the bus bar Bh is detected by the case main body 102 and the internal current detection circuit. It is also advantageous in that it is difficult to be transmitted to and less susceptible to heat.

[Installation surface]
The superiority according to the present embodiment is not limited to the above.
FIG. 8 is a perspective view showing the shape of the bottom surface 102 h of the current detector 100. As described above, the current detector 100 may be attached to the casing S of the object with the bottom surface 102h as the installation surface. In this case, the bottom surface 102h of the current detector 100 (case body 102) is closed by the casing S of the object, and cannot be said to be open to the outside air. Therefore, in general, the heat generated from the mounting components (transistor or the like) on the circuit board 114 is likely to be trapped between the bottom surface 102 h of the case body 102 and the housing S.

  The inventor of the present invention pays attention to the above points, and the bottom surface 102h of the case body 102 is formed such that the edges of the plurality of plate-like pieces 102n are in contact with the housing S, so that the space between the bottom surface 102h and the housing S is obtained. It prevented the heat from accumulating. Specifically, a plurality of plate-like pieces 102n extending in the width direction are arranged in an area close to the bottom of the circuit board 114 in the bottom surface 102h in a state where an edge is set up with respect to the bottom surface 102h. Between the plate-like pieces 102n, the outer surface of the case main body 102 is recessed to give each plate-like piece 102n a sufficient length (depth in the vertical direction). In addition, the area | region far from directly under the circuit board 114 in the bottom face 102h is made into the flat part 102m, and the stability at the time of installation is improved.

  Thereby, the contact area with the housing | casing S in the bottom face 102h of the case main body 102 is suppressed as a whole, and it is prevented that a heat | fever retains. In particular, when the electronic component of the circuit board 114 is a heat generation source, heat tends to be trapped in a region close to the heat source. However, the effect of suppressing heat retention is large by configuring this region with a plurality of plate-like pieces 102n. Further, since the plurality of plate-like pieces 102n have a certain length, the heat radiation area from the case main body 102 is increased by that amount, and the heat radiation performance is improved.

  The present invention can be implemented with various modifications without being limited to the above-described embodiments. In one embodiment, the insertion hole 104 has a substantially octagonal shape in accordance with the bus bars Bh, Bv and the like to be inserted. However, the insertion hole 104 may have a rectangular shape, a hexagonal shape, a circular shape, or the like.

  The number of plate-like pieces arranged in the insertion hole 104 as the restricting portion 102e can be changed as appropriate, and the offset amount (proximity distance F) to be brought close to the magnetic core 110 in the accommodating portion 102g is also set appropriately. Can be changed.

  In addition, the current detector 100 and a part of the structure shown together with the drawings are just preferable examples, and the present invention can be suitably implemented even if various elements are added to the basic structure or a part thereof is replaced. Needless to say.

DESCRIPTION OF SYMBOLS 100 Current detector 102 Case main body 102d Wall board part 102e Control part 104 Insertion hole 106 Potting resin 110 Magnetic body core

Claims (4)

A case main body in which a through hole through which a conductor of a current to be detected is inserted is formed inside, and a housing portion that houses a current detection circuit together with an annular magnetic core around the through hole,
A sealing body that fills and seals the inside of the accommodating portion in a state in which the magnetic core and the current detection circuit are accommodated;
The case body is integrated with the portion constituting the wall of the housing portion along the insertion hole, and in the insertion hole, the case body outer surface is brought close to the conductor to regulate the inclination of the conductor with respect to the insertion direction. On the other hand, a current detector provided with a regulating portion that regulates a filling range of the sealing body by separating the inner surface of the case main body from the conductor and approaching the magnetic core in the housing portion. The current detector of claim 1,
The restriction site is
A current detector comprising a plurality of plate-like pieces extending toward the inside of the insertion hole and having tip edges close to the conductor at a portion constituting a wall of the housing portion. The current detector according to claim 1 or 2,
The restriction site is
The current detector is characterized in that a portion constituting the wall of the housing portion has a stepped shape around the magnetic core in the housing portion and is close to the magnetic core. The current detector according to any one of claims 1 to 3,
The case body is
A current detector having an installation surface for fixing to an object, wherein the case main body contacts the object at the edges of a plurality of plate-like pieces within the installation surface.