JP2013231691A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor whereby, even when a bus bar of a vehicle such as an electric vehicle temporarily becomes a high temperature according to change of power transferred therethrough, a magnetoelectric transducer of a current sensor measuring current of the bus bar is prevented from becoming an excessive high temperature.SOLUTION: A current sensor 1 includes an insulation body 40 which supports a magnetic core 10 penetrated by a bus bar 30 and a hall element 20 in a fixed positional relationship. The insulation body 40 includes an outer frame part 411 or an inner frame part 421 having a double-wall structure forming cavities 4110, 4210 thereinside, and constituting a cylindrical double-partition penetrating a hollow part 11 of the magnetic core 10 for partitioning between an inner periphery part of the magnetic core 10 and the bus bar 30.

Description

  The present invention relates to a current sensor that measures a current flowing in a bus bar that penetrates a hollow portion of a magnetic core.

  A vehicle such as a hybrid vehicle or an electric vehicle is often equipped with a current sensor that measures a current flowing through a bus bar connected to a battery. As such a current sensor, a magnetic proportional current sensor or a magnetic balance current sensor may be employed.

  For example, as disclosed in Patent Documents 1 and 2, a magnetic proportional type or magnetic balance type current sensor includes a magnetic core and a magnetoelectric conversion element. The magnetic core is a generally ring-shaped magnetic body formed in a series surrounding both sides of a hollow portion where both ends face each other through a gap portion and the bus bar passes therethrough. The hollow portion of the magnetic body is a space through which the current to be measured passes.

  The magnetoelectric conversion element is disposed in the gap portion of the magnetic core, measures the magnetic flux that changes according to the current flowing through the bus bar disposed through the hollow portion, and outputs the magnetic flux measurement signal as an electrical signal. It is an element. As the magnetoelectric conversion element, a Hall element is usually adopted.

  In addition, as shown in Patent Documents 1 and 2, the current sensor includes a non-conductive housing that houses necessary devices such as a magnetic core, a magnetoelectric conversion element, and a circuit board on which the magnetoelectric conversion element is mounted. Provided as an electrical component having a dustproof structure. The magnetic core and the magnetoelectric conversion element are supported in a fixed positional relationship by the casing. Note that the casing of the current sensor is generally made of a non-conductive resin member.

JP 2004-101384 A JP 2009-128116 A

  By the way, in an electric vehicle such as an electric vehicle and a hybrid vehicle, the fluctuation of the electric power supplied to the motor through the bus bar is large, and the bus bar temporarily becomes excessively hot due to self-heating when conducting a large amount of electricity. There is a case. In that case, the magnetoelectric conversion element of the current sensor arranged near the bus bar is also likely to become high temperature due to the influence of heat generated by the bus bar.

  For example, the heat of the bus bar is transmitted to the magnetoelectric conversion element through a partition wall that partitions the bus bar in the housing from the inner edge of the magnetic core, or through the partition wall and the magnetic core having high thermal conductivity. Since the magnetoelectric conversion element is not excellent in heat resistance, the magnetoelectric conversion element is likely to break down when the temperature is excessively high due to the heat generated by the bus bar.

  In the present invention, even when a bus bar of a vehicle such as an electric vehicle temporarily becomes high temperature in accordance with fluctuations in electric power conducted by the vehicle, the magnetoelectric conversion element of the current sensor that measures the current of the bus bar becomes excessively high temperature. The purpose is to prevent becoming.

The current sensor according to the first aspect of the present invention includes the following components.
(1) The first component is a magnetic core formed in a series around the periphery of the hollow portion through which the bus bar passes.
(2) A 2nd component is a magnetoelectric conversion element which measures the magnetic flux which arises in the said magnetic body core.
(3) The third component is a non-conductive casing that accommodates the magnetic core and the magnetoelectric transducer and supports them in a fixed positional relationship. The casing has a double-wall structure that forms a cavity therein, and has a cylindrical shape that penetrates the hollow portion of the magnetic core and partitions the inner edge of the magnetic core and the bus bar. A heavy bulkhead is provided.

  The current sensor according to the second aspect of the present invention is an aspect of the current sensor according to the first aspect. In the second aspect, the housing includes a container member that houses the magnetic core and the magnetoelectric conversion element, and a lid member that is combined with the container member and closes the opening of the container member. Further, the double partition wall of the housing protrudes from the cylindrical inner double partition wall formed by projecting on one of the container member and the lid member, and the other of the container member and the lid member. And a double-layered double-wall structure including an outer double partition formed along the outer peripheral surface of the inner double partition.

  The current sensor according to the third aspect of the present invention is an aspect of the current sensor according to the first aspect or the second aspect. In the third aspect, the double partition wall of the casing is molded by synthetic resin gas injection molding.

  In the first to third aspects, the double partition wall of the housing is a wall that partitions between the inner edge portion of the magnetic core and the bus bar that penetrates the hollow portion of the magnetic core. In addition, since the magnetoelectric conversion element is disposed in the gap portion of the magnetic core, the double partition wall of the housing is also a wall that partitions the magnetoelectric conversion element and the bus bar.

  And in the 1st-3rd aspect, since the double partition of a housing | casing has the double wall structure which forms a cavity inside, it is excellent in heat insulation. Therefore, according to the current sensor according to the first to third aspects, even when the bus bar penetrating the magnetic core temporarily becomes high temperature according to the fluctuation of the electric power conducted by the bus bar, the insulation of the double partition wall Therefore, it is possible to prevent the magnetoelectric conversion element of the current sensor from being excessively heated.

  Moreover, according to the current sensor which concerns on a 2nd aspect, a double partition has a double-layered double wall structure which consists of an inner double partition and an outer double partition. Therefore, the heat insulation of the double partition wall is further improved, and the high temperature of the magnetoelectric conversion element can be prevented more reliably.

  Moreover, according to the current sensor which concerns on a 3rd aspect, the double partition of a housing | casing is shape | molded by the gas injection molding of a synthetic resin. For this reason, the structure of the mold for molding the casing is simplified, and the casing having the double partition wall can be easily molded.

1 is an exploded perspective view of a current sensor 1 according to an embodiment of the present invention. It is a perspective view of the lid member which constitutes the case with which current sensor 1 is provided. 3 is a three-side view of the current sensor 1. FIG. 1 is a cross-sectional view of a current sensor 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and is not an example of limiting the technical scope of the present invention.

  Hereinafter, the configuration of the current sensor 1 according to the embodiment of the present invention will be described with reference to FIGS. 3A is a plan view of the current sensor 1, FIG. 3B is a front view of the current sensor 1, and FIG. 3C is a side view of the current sensor 1. FIG. 4 is a cross-sectional view of the current sensor 1 in the II plane shown in FIG.

  The current sensor 1 is a device that measures a current flowing through a bus bar that electrically connects a battery and a device such as a motor in a vehicle such as an electric vehicle or a hybrid vehicle. As shown in FIG. 1, the current sensor 1 includes a magnetic core 10, a Hall element 20, an insulating housing 40, a circuit board 50, and a connector 60. Further, as shown in FIGS. 1 and 2, the insulating housing 40 includes a container member 41 and a lid member 42 that are combined with each other.

<Magnetic core>
The magnetic core 10 is a member made of a magnetic material such as ferrite or silicon steel. The magnetic core 10 has a shape in which both end faces 13 are opposed to each other via a gap portion 12 of about several millimeters and are formed in a series around the hollow portion 11. That is, the magnetic core 10 is formed in an annular shape together with the narrow gap portion 12.

  In the present embodiment, the magnetic core 10 is formed in a generally rectangular ring surrounding the rectangular hollow part 11 with rounded corners together with the gap part 12. Note that the magnetic core 10 may be formed in an annular shape surrounding the circular hollow portion 11 together with the gap portion 12.

  The bus bar 30 that is a power transmission path through which the current to be measured flows is disposed through the hollow portion 11 of the magnetic core 10. In FIG. 1, the bus bar 30 is drawn by an imaginary line (two-dot chain line).

<Hall element (magnetoelectric conversion element)>
The Hall element 20 is a sensor that measures a magnetic flux in the gap portion 12 of the magnetic core 10. The Hall element 20 shown in FIG. 1 is a lead wire type IC including a magnetic detection unit 21 which is a main body of the element and a plurality of lead terminals 22 protruding from the bottom surface of the magnetic detection unit 21. The plurality of lead terminals 22 include a power input terminal and a measurement signal output terminal. The plurality of lead terminals 22 are inserted into Hall element mounting holes 53 formed in the circuit board 50 and fixed to the wiring pattern of the circuit board 50 by soldering. Note that a surface-mount type Hall element 20 may be employed.

  The magnetic detection unit 21 of the Hall element 20 is disposed in the gap portion 12 of the magnetic core 10. In this state, the Hall element 20 measures the magnetic flux that changes in accordance with the current passing through the hollow portion 11 of the magnetic core 10 and outputs a magnetic flux measurement signal as an electrical signal. The Hall element 20 is an example of a magnetoelectric conversion element.

  The Hall element 20 measures the magnetic flux passing through a measurement center portion, which is a predetermined portion in the magnetic detection unit 21, along a predetermined direction with the highest sensitivity. In general, the reference straight line indicating the path of the magnetic flux measured with the highest sensitivity by the Hall element 20 is a straight line that passes through substantially the center of the magnetic detection unit and is orthogonal to the front and back surfaces of the magnetic detection unit 21.

  In the current sensor 1, the measurement center portion of the magnetic detection unit 21 is positioned at the center point of the gap portion 12 of the magnetic core 10, and the reference straight lines of the magnetic detection unit 21 are opposite end surfaces 13 of the magnetic core 10. The state of overlapping with the straight line connecting the centers of the projection planes is an ideal arrangement state of the magnetic detection unit 21.

<Circuit board and connector>
The circuit board 50 is a board on which the Hall element 20 is mounted at the lead terminal 22 portion. In addition to the Hall element 20, the circuit board 50 is mounted with a lead terminal 62 of the connector 60 and a circuit for performing a stabilization process of a measurement signal of magnetic flux output from the Hall element 20.

  In the example shown in FIG. 1, a first through hole 51 through which each of the first screws 71 passes and a second through hole 52 through which the second screws 72 pass are formed in the circuit board 50. The first screw 71 is a screw that fixes the main body 61 of the connector 60 to the circuit board 50. The second screw 72 is a screw that fixes the circuit board 50 to the container member 41 of the insulating housing 40.

  The connector 60 is a component to which a mating connector provided on an electric wire (not shown) is connected. The connector 60 includes a main body portion 61 and lead terminals 62. The main body 61 is a non-conductive member in which a connection port to which a mating connector is connected is formed. The lead terminal 62 is a conductive terminal that electrically connects the metal terminal in the main body 61 and the wiring pattern of the circuit board 50.

  A plurality of lead terminals 62 in the connector 60 are inserted into connector mounting holes 54 formed in the circuit board 50 and fixed to the wiring pattern of the circuit board 50 by soldering.

  The circuit board 50 is provided with a circuit that electrically connects the lead terminals 22 of the Hall elements 20 and the lead terminals 62 of the connector 60. For example, the circuit board 50 is provided with a circuit for supplying power input from the outside via the electric wire and the connector 60 to the lead terminal 22 of the Hall element 20, and a stabilization process for the measurement signal of the Hall element 20. For example, a circuit for outputting the processed signal to the lead terminal 62 of the connector 60 is provided. Thereby, the current sensor 1 can output a current measurement signal to an external circuit such as an electronic control unit through the electric wire with connector connected to the connector 60.

<Insulated housing>
The container member 41 and the lid member 42 constituting the insulating housing 40 are each integrally formed members of an insulating resin material. Each of the container member 41 and the lid member 42 is an integrally formed member made of an insulating resin such as polyamide (PA), polypropylene (PP), or ABS resin.

  The container member 41 is formed in a box shape having an opening, and the lid member 42 closes the opening of the container member 41 by being combined with the container member 41. The container member 41 and the lid member 42 are formed with a bus bar hole 401 that is a through hole through which the bus bar 30 passes.

  On the inner surface of the container member 41, a cylindrical outer frame portion 411 surrounding the periphery of the bus bar hole 401 is formed. Similarly, a cylindrical inner frame portion 421 surrounding the periphery of the bus bar hole 401 is formed on the inner surface of the lid member 42. When the container member 41 and the lid member 42 are combined, the inner frame portion 421 fits inside the outer frame portion 411. Details of the outer frame portion 411 and the inner frame portion 421 will be described later.

  The container member 41 is a member that supports the magnetic core 10, the Hall element 20, the circuit board 50, and the connector 60 in a fixed positional relationship and accommodates them. However, the connector 60 is accommodated in the insulating housing 40 with a part thereof exposed.

  More specifically, on the inner side of the container member 41, a core positioning part 43, an element positioning part 44, and a magnetic core 10, a hall element 20, and a main body part 61 of the connector 60 are supported at predetermined positions. A connector positioning portion 45 is formed. Furthermore, a substrate fixing part 46 to which the circuit board 50 is fixed is also formed inside the container member 41.

  In the example shown in FIG. 1, the core positioning portion 43 is passed through the hollow portion 11 of the magnetic core 10 to support and position the inner edge of the magnetic core 10. The element positioning portion 44 forms a recess into which the magnetic detection portion 21 of the Hall element 20 is fitted. The magnetic detection unit 21 of the Hall element 20 is positioned by the element positioning unit 44 by being fitted into the recess of the element positioning unit 44.

  Further, the connector positioning unit 45 positions the main body 61 of the connector 60 by supporting the back surface, both side surfaces, and the bottom surface of the main body 61 of the connector 60. Further, a screw hole 460 into which the second screw 72 is tightened is formed at the top portion of the substrate fixing portion 46.

  The lid member 42 opens the container member 41 while sandwiching the magnetic core 10 and the circuit board 50 with respect to the container member 41 that supports the magnetic core 10, the Hall element 20, the connector 60, and the circuit board 50. It is attached to the container member 41 in a closed state.

  In addition, as shown in FIG. 2, the lid side core support portion 422 is also formed on the inner side surface of the lid member 42 so as to protrude in addition to the inner frame portion 421. The lid-side core support portion 422 restricts the movement of the magnetic core 10 supported by the core positioning portion 43 of the container member 41 toward the lid member 42.

  The container member 41 and the lid member 42 are provided with a lock mechanism 47 that holds them in a combined state. The lock mechanism 47 shown in FIG. 1 includes a claw portion 471 formed to project from the side surface of the container member 41 and an annular frame portion 472 formed on the side of the lid member 42. By fitting the claw portion 471 of the container member 41 into the hole formed by the frame portion 472 of the lid member 42, the container member 41 and the lid member 42 are held in a state where they are combined.

<Insulation structure>
Next, a heat insulating structure provided in the current sensor 1 will be described with reference to a cross-sectional view shown in FIG. In the present embodiment, each of the container member 41 and the lid member 42 constituting the insulating housing 40 is a synthetic resin member formed by synthetic resin gas injection molding.

  In gas injection molding, molten resin is injected into a mold cavity, a pressurized fluid that does not mix with the resin is injected into the mold cavity, and the molten resin is pressed against the cavity wall by the internal pressure of the pressurized fluid. This is a technique for molding. For example, an inert gas such as nitrogen gas is used as the pressurized fluid. Since gas injection molding is well known, detailed description thereof is omitted here.

  As shown in FIG. 4, cavities 410 and 420 are formed inside the container member 41 and the lid member 42, which are resin members obtained by gas injection molding. Each of the container member 41 and the lid member 42 is formed with gas injection holes 481 and 482 into which a pressurized fluid is injected at the time of gas injection molding.

  Accordingly, the cylindrical outer frame portion 411 surrounding the periphery of the bus bar hole 401 has a double wall structure in which a cavity 4110 is formed. Similarly, the cylindrical inner frame part 421 surrounding the periphery of the bus bar hole 401 also has a double wall structure in which a cavity 4210 is formed. Each of the outer frame portion 411 and the inner frame portion 421 constitutes a cylindrical double partition that penetrates the hollow portion 11 of the magnetic core 10 and partitions the inner edge portion of the magnetic core 10 and the bus bar 30. Yes.

  The inner frame portion 421 is an example of a cylindrical inner double partition wall formed by protruding from the lid member 42, and the outer frame portion 411 is formed by protruding from the container member 41, and the inner frame portion 421 is formed. It is an example of the outer side double partition formed along the outer peripheral surface of (inner side double partition). As described above, the insulating housing 40 has a two-layer double wall structure including the inner frame portion 421 and the outer frame portion 411.

<Effect>
In the current sensor 1, the inner frame portion 421 and the outer frame portion 411 constituting the double partition wall of the insulating housing 40 are formed between the inner edge portion of the magnetic core 10 and the bus bar 30 that penetrates the hollow portion 11 of the magnetic core 10. It is a wall that separates the spaces. Further, since the Hall element 20 is disposed in the gap portion 12 of the magnetic core 10, the inner frame portion 421 and the outer frame portion 411 (double partition walls) are walls that partition the Hall element 20 and the bus bar 30. But there is.

  And in the current sensor 1, since the inner side frame part 421 and the outer side frame part 411 (double partition) have the double wall structure which forms the cavity 4110, 4210 inside, it is excellent in heat insulation. Therefore, when the current sensor 1 is employed, the inner frame portion 421 and the outer frame portion 411 are used even when the bus bar 30 penetrating the magnetic core 10 temporarily becomes high temperature according to fluctuations in the electric power conducted by the bus bar 30. Due to the heat insulation of the (double partition wall), the Hall element 20 is prevented from becoming an excessively high temperature.

  Further, when the current sensor 1 is employed, the inner frame portion 421 and the outer frame portion 411 have a double-layered double wall structure. Therefore, the heat insulation of the double partition wall is further improved, and the high temperature of the Hall element 20 can be prevented more reliably.

  Further, in the current sensor 1, the inner frame portion 421 and the outer frame portion 411 (double partition walls) are formed by synthetic resin gas injection molding. Therefore, the structure of the mold for molding the insulating casing 40 is simplified, and the insulating casing 40 having a double partition wall can be easily molded.

  In the current sensor 1, of the cavities 410 and 420 inside the insulating housing 40, portions other than the cavity 4210 inside the inner frame 421 and the cavity 4110 inside the outer frame 411 are formed from the bus bar 30 to the Hall element. It does not contribute so much to the suppression of heat transfer to 20. That is, cavities other than the cavities 4210 and 4110 inside the inner frame 421 and the outer frame 411 are naturally formed by gas injection molding of synthetic resin, but are cavities that need not be formed.

  In addition, the two-layered cylinder formed by fitting the inner frame portion 421 inside the outer frame portion 411 is electrically connected between the bus bar 30 penetrating the bus bar hole 401 and the component mounted on the circuit board 50. A shielding plate is configured. Therefore, a sufficient creepage distance between the bus bar 30 and the electronic component such as the Hall element 20 is ensured, and the electronic component is less likely to fail due to a surge voltage applied to the bus bar 30.

<Others>
In the insulating housing 40 of the current sensor 1, the inner frame portion 421 (inner double partition wall) is formed to protrude from the container member 41, and the outer frame portion 411 (outer double partition wall) is formed to protrude from the lid member 42. It can also be considered.

  Moreover, in the insulated housing 40 of the current sensor 1, it is conceivable that one of the outer frame portion 411 and the inner frame member 421 is omitted.

  It is also conceivable that the outer frame portion 411 and the inner frame portion 421 forming a double partition wall are formed by general injection molding. In this case, the mold used for injection molding has portions for forming the cavities 4110 and 4210 of the outer frame portion 411 and the inner frame portion 421, respectively.

DESCRIPTION OF SYMBOLS 1 Current sensor 10 Magnetic body core 11 Hollow part of magnetic body core 12 Gap part of magnetic body core 13 End surface of magnetic body core 20 Hall element (magnetoelectric conversion element)
21 Hall Element Magnetic Detection Unit 22 Hall Element Lead Terminal 30 Bus Bar 40 Insulating Housing (Case)
41 Container member 42 Lid member 43 Core positioning portion 44 Element positioning portion 45 Connector positioning portion 46 Board fixing portion 47 Lock mechanism 50 Circuit board 51 First through hole 52 Second through hole 53 Hall element mounting hole 54 Connector mounting hole 60 Connector 61 Connector main body 62 Connector lead terminal 71 First screw 72 Second screw 401 Bus bar hole 411 Outer frame (double partition, outer double partition)
421 Inner frame (double bulkhead, inner double bulkhead)
422 Lid side core support part 460 Screw hole 471 Claw part 472 Frame part 4110 Cavity of outer frame part 4210 Cavity of inner frame part 410,420 Cavity 481,482 Gas injection hole

Claims (3)

A magnetic core made of a magnetic material and formed in a series around the periphery of the hollow portion through which the bus bar passes,
A magnetoelectric transducer for measuring magnetic flux generated in the magnetic core;
A non-conductive housing that houses the magnetic core and the magnetoelectric conversion element and supports the magnetic core in a fixed positional relationship,
The housing is
It has a double wall structure that forms a cavity inside, and includes a cylindrical double partition that penetrates the hollow portion of the magnetic core and partitions the inner edge of the magnetic core and the bus bar, Current sensor. The current sensor according to claim 1,
The housing is
A container member that houses the magnetic core and the magnetoelectric transducer;
A lid member combined with the container member to close the opening of the container member,
The double bulkhead of the housing is
A cylindrical inner double partition formed by projecting on one of the container member and the lid member;
A current sensor having a double-layered double-wall structure formed by projecting on the other of the container member and the lid member and an outer double partition formed along the outer peripheral surface of the inner double partition . The current sensor according to claim 1 or 2,
The double bulkhead of the casing is a current sensor formed by synthetic resin gas injection molding.

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