JP2004077184A - Current detecting sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of components and assembling man-hour, to miniaturize a current detecting sensor, to facilitate installation, and to reduce cost, by correctively mounting, to a circuit board, a unitary structure where the magnetic substance is excellent in shock resistance or oxidation resistance, hence a case and sealing are not required, and a sensor unit comprises a conductor, an electrical insulation ring, the magnetic substance, and a hall element. <P>SOLUTION: The current detecting sensor has the annular magnetic substance 14 made of magnetic material and synthetic resin and having a magnetic gap. The current detecting sensor has the conductor 6 that penetrates through the magnetic substance 14 and changes magnetic flux passing in a magnetic gap 28 when load current to be detected is supplied. The sensor has a magnetism sensing element 18 engaged with the magnetic gap 28, and a detecting circuit for detecting the magnetic flux with the magnetism sensing element 18 and outputting an electric signal for indicating the load current based on the detected magnetic flux. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a current detection sensor that detects a current flowing in an electric circuit.
[0002]
[Related background art]
This type of current detection sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-201438. This known current detection sensor includes a current detection conductor, a magnetic core around which the current detection conductor is wound, and a magnetoelectric transducer arranged in a magnetic gap of the magnetic core.
According to the above-described current detection sensor, when a load current to be detected flows through the current detection conductor, the load current changes the magnetic field of the magnetic core, and the change in the magnetic field appears in the output of the magnetoelectric conversion element. That is, the current detection sensor can detect the load current as the output of the magneto-electric conversion element.
[0003]
Incidentally, sintered ferrite or cast iron is generally used for the magnetic core used in the above-described current detection sensor. Ferrite is vulnerable to external impact and the like, and moreover, both ferrite and iron are oxidized by moisture in the air and the like, and there is a problem that the characteristics of the current detection sensor are easily deteriorated.
The magnetoelectric conversion element is generally mounted on a circuit board, and the magnetic core also needs to be mounted on the circuit board.
[0004]
Under such circumstances, a magnetic core provided with a magnetoelectric conversion element is generally mounted on a circuit board and then covered with a case, as in the current detection sensor of the above publication, and the case and the circuit board Are sealed via a sealant. Note that the sealant is also used to fix the magnetic core on the circuit board.
[0005]
[Problems to be solved by the invention]
Although the above-described case and sealant are effective in protecting the magnetic core against external impact and moisture, they not only increase the number of components and assembly steps of the current detection sensor, but also increase the entire sensor. Causes a large size.
Furthermore, since the sealant is also used to hold the magneto-electric conversion element in the magnetic gap of the magnetic core, the assembly of the current detection sensor is further complicated, and the consumption of a large amount of the sealant reduces the current detection. It is increasing the cost of sensors.
[0006]
The present invention has been made to solve the above-described problems, and has as its object to provide a current detection sensor that can reduce the number of parts and the number of assembling steps, and is also advantageous in reducing costs. I do.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a current detection sensor according to the present invention includes a ring-shaped magnetic body made of a magnetic material and a synthetic resin and having a magnetic gap, and a supply of a load current that penetrates the magnetic body and is to be detected. A magnetic flux passing through the magnetic gap, and a magnetic-sensitive element fitted in the magnetic gap, the magnetic-sensitive element detects the magnetic flux, and the load is determined based on the detected magnetic flux. A detection circuit that outputs an electric signal indicating a current.
[0008]
Furthermore, an electric insulating member provided between the conductor and the magnetic body to form a unit in which these are integrally connected is further included (claim 2).
The unit may further include an attachment portion integrally formed at both ends of the conductor and used to attach the unit to a circuit board, wherein the magnetically sensitive element has the unit attached to the circuit board. At this time, the semiconductor device has an input / output terminal electrically connected to the circuit board.
[0009]
Further, the magnetic body is an injection-molded product, and the magnetic gap further has a lock portion for preventing the magnetic sensitive element from coming off (claim 4).
According to such a current detection sensor, the magnetic body is made of a magnetic material and a synthetic resin, and has excellent impact resistance and oxidation resistance. Therefore, there is no need to cover the unit with a case. There is no need to seal the space between the two with a sealant. Further, the unit is an integrated structure including a conductor, an electrically insulating ring, and a magnetic material, and a magnetic material is provided with a magnetic sensitive element, and is mounted on a circuit board collectively. Therefore, a case and a sealant are not required, and the number of parts and the number of assembling steps can be reduced, the size and the installation can be easily reduced, and the cost can be reduced.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a current detection sensor according to the first embodiment. The current detection sensor includes a sensor unit 4 mounted on a circuit board 2. The conductor 6 on the circuit board 2 is formed of a substantially U-shaped wire, and includes a support portion 8 parallel to the circuit board 2 and a pair of legs 10 extending from both ends of the support portion 8 toward the circuit board 2. Having. The tips of the legs 10 are formed as plugs 12 that can be inserted into mounting holes (not shown) of the circuit board 2. After the plugs 12 are inserted, the conductors 6 are fixed to the circuit board 2 by soldering. I have. The plug 12 of the conductor 6 is connected to a wiring (not shown) through which a current to be detected, that is, a load current flows, and can receive the supply of the load current.
[0011]
The support portion 8 of the conductor 6 penetrates an annular magnetic body, that is, an annular plastic magnet 14, and the plastic magnet 14 is supported by the support portion 8 via an electric insulating ring 16 made of synthetic resin. .
A gap is formed in a part of the outer peripheral surface of the plastic magnet 14, and the gap is open toward the circuit board 2. A Hall element 18 as a magnetic sensitive element is mounted in the gap, and the Hall element 18 has a package and input / output terminals 20 protruding from the package toward the circuit board 2. The input / output terminal 20 is electrically connected to printed wiring on the circuit board 2 via solder, and the printed wiring connects the input / output terminal 20 to a monitor circuit 26 via an amplifier 22 and an interface protection circuit 24. The amplifier 22, the interface protection circuit 24, and the monitor circuit 26 are also arranged on the circuit board 2.
[0012]
The plastic magnet 14 is made of a composite material of a ferrite powder and a binder, and is obtained by injection molding. Here, a synthetic resin such as nylon (polyamide resin) or polyphenylene sulfide (PPS) can be used for the binder. The electric insulating ring 16 is made of a synthetic resin such as PPS.
Here, the sensor unit 4 is obtained by integrating the conductor 6, the electrical insulating ring 16 and the plastic magnet 14, and is formed by the following procedure.
[0013]
First, the electric insulating ring 16 is formed by injection molding using the support portion 8 of the conductor 6 as an insert, and thereafter, the plastic magnet 14 is also formed by injection molding using the electric insulating ring 16 as an insert. The gap of the plastic magnet 14 is formed at the same time by injection molding.
More specifically, as shown in FIG. 2, the gap 28 is formed by grooves opened on the outer peripheral surface and both end surfaces of the plastic magnet 14, and has a cross-sectional shape that matches the outer shape of the package 30 of the Hall element 18. . That is, when the package 30 has a box shape with a substantially trapezoidal cross section and its input / output terminals 20 protrude from the bottom surface on the long side of the package 30, the gap 28 expands toward the outer peripheral surface of the plastic magnet 14. It has such an inverted trapezoidal cross section.
[0014]
The gap 28 is deeper than the height of the package 30, and the thickness between the bottom of the gap 28 and the inner peripheral surface of the plastic magnet 14 is such that the gap 28 expands in the circumferential direction of the plastic magnet 14, The setting is made to allow the elastic deformation of the magnet 14.
Further, lock portions 32 are formed on both inner wall surfaces of the gap 28, and these lock portions 32 are positioned near the outer peripheral surface of the plastic magnet 14. The lock portion 32 slightly protrudes into the gap 28 to reduce the groove width of the gap 28.
[0015]
When the package 30 of the Hall element 18 is pushed into the gap 28 from the state shown in FIG. 2, the plastic magnet 14 is elastically deformed, that is, the gap 28 is expanded, and the package 30 rides over the lock portion 32 in the gap 28. The locking portion 32 is engaged with the bottom surface of the package 30 when the gap 28 is closed. Therefore, once the Hall element 18 is mounted in the gap 28, the lock element 32 prevents the Hall element 18 from coming out of the gap 28.
[0016]
As described above, the sensor unit 4 is an integrated structure in which the conductor 6, the electrical insulating ring 16, and the plastic magnet 14 are integrally combined, and further, has the Hall element 18 mounted in the gap 28 of the plastic magnet 14. I have. Accordingly, the conductor 6 of the sensor unit 4, that is, the plug 12 of the pair of legs 10 is inserted into the mounting hole of the circuit board 2, and at the same time, the input / output terminal 20 of the Hall element 18 is also connected to the printed wiring of the circuit board 2. As a result, the sensor unit 4 can be easily mounted on the circuit board 2.
[0017]
According to the current detection sensor 1 described above, when a load current flows through the conductor 6 of the sensor unit 4, the load current generates a magnetic field around the conductor 6. This magnetic field increases the magnetic flux in the plastic magnet 14, and the change in the magnetic flux is output from the input / output terminal 20 of the Hall element 18. Thereafter, this output is supplied to the amplifier 22, the interface protection circuit 24, and the monitor circuit 26, and the monitor circuit 26 detects the value of the load current.
[0018]
Since the plastic magnet 14 of the sensor unit 4 has better impact resistance and oxidation resistance than a magnetic core made of ferrite or the like, the sensor unit 4 is covered with a case, and a gap between the case and the circuit board 2 is formed. Need not be sealed with a sealant.
Accordingly, a case and a sealant are not required for mounting the sensor unit 4 on the circuit board 2, so that the number of components and the number of assembling steps can be reduced, and the cost of the current detection sensor can be reduced. it can.
[0019]
Further, as described above, at the same time as the plug 12 of the conductor 6 is inserted into the mounting hole of the circuit board 2, the positioning of the Hall element 18, that is, the input / output terminal 20 with respect to the printed wiring of the circuit board 2, The mounting of the plastic magnet 14 is completed, and the mounting of the sensor unit 4 can be easily performed.
In this case, no sealant is required for attaching the plastic magnet 14 to the circuit board 2.
[0020]
Further, since the plastic magnet 14 is an injection molded product, the gap 28 can also be formed with high precision in accordance with the package 30 of the Hall element 18. Therefore, a sealant is not required for mounting the Hall element 18 in the gap 28, and the width of the gap 28 is unnecessarily widened, and the magnetic flux density in the gap 28 is not undesirably reduced.
[0021]
FIG. 3 shows a current detection sensor according to the second embodiment. In describing this current detection sensor, members and portions having functions similar to those of the current detection sensor according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Will be described.
The current detection sensor according to the first embodiment is applied to detection of a small load current (10 A or less), whereas the current detection sensor according to the second embodiment has a large load current (larger than 10 A). Applies to detection.
[0022]
The conductor 34 of the sensor unit 4 in the current detection sensor is not a wire but a rectangular cross-section plate material, and the tips of the pair of legs 10 are bent in directions away from each other to form a mounting pad 36. ing. A bolt insertion hole is formed in each of the mounting pads 36, and the bolt 38 is screwed into the circuit board 2 through these insertion holes, whereby the mounting pad 36, that is, the sensor unit 4 is mounted on the circuit board 2. The mounting pad 36 is also electrically connected to a wiring through which a load current to be detected flows, and can receive the load current.
[0023]
Further, as described above, since the conductor 34 is a plate material, the electric insulating ring 40 and the plastic magnet 42 are also not in a ring shape, and both the outer peripheral surface and the inner peripheral surface have a rectangular angular ring shape. The plastic magnet 42 has a lower surface facing the circuit board 2, and the package 30 of the Hall element 18 is similarly mounted in the gap 28 formed on the lower surface.
[0024]
The sensor unit 4 of the current detection sensor is also an integrated structure including the conductor 34, the electrically insulating ring 40, and the plastic magnet 42, and the Hall element 18 is mounted on the plastic magnet 42. And has the same advantages as the current detection sensor according to the first embodiment.
In FIG. 3, the amplifier 22, the interface protection circuit 24, and the monitor circuit 26 are omitted.
[0025]
The present invention is not limited to the current detection sensors of the first and second embodiments described above, and various modifications are possible.
For example, the conductors 6 and 34 are fixed to the circuit board 2 by soldering or using bolts, but other fixing means may be adopted.
Further, for the plastic magnets 14 and 42, a powder of a magnetic material such as permalloy or silicon steel may be used in addition to the ferrite powder.
[0026]
Further, the amplifier 22, the interface protection circuit 24, and the monitor circuit 26 do not necessarily need to be arranged on the circuit board 2.
[0027]
【The invention's effect】
According to the current detection sensor of the present invention (claims 1 to 4), since the plastic magnet has excellent impact resistance and oxidation resistance, there is no need to cover the sensor unit with a case. There is no need to seal the space between the two with a sealant. Further, the sensor unit is an integrated structure including a conductor, an electrically insulating ring, and a plastic magnet, and a hall element is mounted on the plastic magnet, and is mounted on the circuit board in a lump. Therefore, a case and a sealant are not required, and the number of parts and the number of assembling steps can be reduced, miniaturization and installation can be facilitated, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing a current detection sensor according to a first embodiment of the present invention.
FIG. 2 is a front sectional view showing a gap portion and a Hall element of the magnetic body according to the first embodiment of the present invention.
FIG. 3 is an external perspective view showing a current detection sensor according to a second embodiment of the present invention.
[Explanation of symbols]
2 Circuit board 4 Sensor unit 6 Conductor 8 Support section 10 Leg section 12 Plug 14 Plastic magnet 16 Electrical insulating ring 18 Hall element 20 Input / output terminal 22 Amplifier 24 Interface protection circuit 26 Monitor circuit 28 Gap 30 Package 32 Lock section 34 Conductor 36 Mounting Pad 38 Bolt 40 Electrical insulation ring 42 Plastic magnet

Claims (4)

An annular magnetic body made of a magnetic material and a synthetic resin and having a magnetic gap,
A conductor that penetrates the magnetic body and changes a magnetic flux passing through the magnetic gap when receiving a supply of a load current to be detected,
A detection circuit having a magnetic-sensitive element fitted in the magnetic gap, detecting the magnetic flux with the magnetic-sensitive element, and outputting an electric signal indicating the load current based on the detected magnetic flux. Characteristic current detection sensor. 2. The current detection sensor according to claim 1, further comprising an electric insulating member provided between the conductor and the magnetic body to form a unit in which these are integrally connected. The unit is
An attachment portion formed integrally with both ends of the conductor and used for attachment of the unit to a circuit board,
The current detection sensor according to claim 2, wherein the magnetically sensitive element has an input / output terminal that is electrically connected to the circuit board when the unit is mounted on the circuit board. The magnetic body is an injection molded product,
The current detection sensor according to any one of claims 1 to 3, wherein the magnetic gap further includes a lock portion that prevents the magnetic sensitive element from being removed.

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