JP2010008179A - Current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current detector capable of achieving an optimum measurement environment. <P>SOLUTION: The current detector 100 includes: a magnetic core 102 disposed along a circumferential direction of the magnetic field generated by a current to be detected; and a Hall element 106 disposed in a gap 102d in the magnetic core 102. The Hall element 106 is inserted in the gap 102d while being held by a holding member 108, so that it is positioned in an appropriate position in the gap 102d by the holding member 108. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic proportional current detector used for current measurement and detection, feedback control, and the like.

  As a prior art related to this type of current detector, there is known a current sensor that converts a magnetic field generated by a current to be detected into a voltage signal by a Hall element and indirectly detects a current value therefrom (for example, Patent Document 1). reference.). This known current sensor includes a magnetic core constituting a magnetic circuit, and a Hall element is arranged in a gap (effective gap) formed in the core. A magnetic field generated in the core by the detected current circulates through the gap and is converted into a voltage signal (Hall voltage) by the Hall element.

In particular, in the above prior art, a current line (electric wire) through which a current to be detected flows, a magnetic core, a hall element, and the like are integrally fixed by a resin mold, and these are formed as one part. For this reason, since the positional relationship between the magnetic core and the Hall element is always constant, the strength of the magnetic field acting on the Hall element in the gap during current measurement is stabilized, thereby suppressing the occurrence of measurement errors. It is considered possible.
JP 59-9565 A

  The above prior art is intended to suppress the occurrence of measurement errors due to the positional deviation of the Hall element after manufacture by hardening the Hall element with a resin mold while the Hall element is inserted into the gap during the manufacture of the current sensor. is there. However, strictly speaking, the distribution of the magnetic field generated in the gap is not uniform, and the strength of the magnetic field varies depending on a minute position within the same gap. For this reason, for example, when there is a bias in the magnetic field distribution in the gap, an appropriate measurement environment is not always obtained at that position even if the position of the Hall element is fixed in one place in advance. Absent.

  For example, even if there is an optimum position where the measurement result can be obtained most efficiently in view of the distribution state of the magnetic field in the gap, the prior art technique does not necessarily fix the Hall element at the optimum position. . For this reason, in some cases, the Hall element may be fixed at an inefficient position (for example, a position where the magnetic field to be measured is hardly distributed or a position where more magnetic fields not to be measured are distributed). There is. In such a situation, since the measurement environment itself is not appropriate before the measurement error is suppressed, there is a problem that the measurement result originally intended by the current sensor cannot be obtained satisfactorily.

  Accordingly, an object of the present invention is to provide a technique capable of realizing a measurement environment suitable for a current detector.

  The present invention is arranged in a ring shape along the circulation direction of a magnetic field generated when a current to be detected is conducted, and a magnetic core in which a gap is formed in a part thereof, and a magnetic core disposed in the gap of the magnetic core. A current detector including a Hall element that outputs a voltage signal corresponding to the strength of a magnetic field generated in a gap through a magnetic core when current is conducted. In particular, the current detector of the present invention inserts a holding member together with the Hall element into the gap to hold the Hall element, and positions the Hall element at a predetermined position in the gap while the holding member holds the Hall element. This solves the above problem.

  According to the current detector of the present invention, since the holding member is inserted into the gap together with the Hall element and holds the Hall element, the Hall element can be reliably positioned at a predetermined position in the gap. For this reason, for example, if a position suitable for measurement within the gap (for example, a position where the distribution of the magnetic field to be measured is large or a position where there is almost no magnetic field to be measured) is known in advance, the position is determined. Since the Hall element can be accurately positioned by aiming, the accuracy of the current detector can be improved accordingly.

  More preferably, the holding member positions the Hall element in the circumferential direction of the magnetic core in the gap. That is, if the magnetic field distribution varies in the circumferential direction of the magnetic core even within the same gap, the Hall element can be accurately positioned at a position suitable for measurement in view of the distribution state.

  The current detector of the present invention is disposed in the vicinity of the gap with respect to the magnetic core, and generates a secondary magnetic field in a direction to cancel the magnetic field generated when the detected current is conducted as viewed in the circumferential direction of the magnetic core. A winding is further provided. In this case, the holding member positions the Hall element at a position where the magnetic field disappears in the gap as a reverse magnetic field is generated by the secondary winding.

  When the secondary winding is provided as described above, the current detector is a so-called servo type. Such a servo-type current detector cancels the magnetic field generated when the current to be detected is conducted with a reverse magnetic field generated by energizing the secondary winding, and performs secondary winding based on the voltage signal obtained from the Hall element. It is used for the purpose of feedback control of the current flowing through the line. For example, assuming that the state in which the magnetic field in the gap is completely canceled by the reverse magnetic field is the steady state of the system (for example, an electric circuit), when the system is actually stabilized in the target steady state for control, the Hall element The voltage signal from becomes an appropriate value (= 0). In this case, the system can be stabilized by feedback-controlling the current of the secondary winding in a direction in which the voltage signal approaches an appropriate value.

  However, even if the system is actually stable in the desired steady state, the position where the magnetic field ideally cancels out in the same gap may be limited. In this case, if the Hall element is not accurately positioned at that position, the obtained voltage signal varies, and the accuracy as a current detector is lowered. For this reason, in the present invention, the Hall element is accurately positioned at the position where the magnetic field disappears in the gap, so that a voltage signal that accurately represents the state of the system is output from the Hall element. Thereby, more accurate feedback control can be realized using the current detector of the present invention.

  As described above, the current detector of the present invention can obtain a highly accurate measurement result by correctly arranging the Hall elements at appropriate positions in accordance with the magnetic field distribution in the gap. In addition, even after the Hall element is correctly positioned at the time of manufacture, since the positioning state is maintained by the holding member, the position of the Hall element is not shifted when the current detector is used, and it is optimal for a long period of time. The state can be maintained and high detection accuracy can continue to be exhibited.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing a configuration of a current detector 100 according to an embodiment. Hereinafter, the configuration of the current detector 100 will be described.

[Magnetic core]
The current detector 100 includes a magnetic core 102 made of ferrite, for example, and the magnetic core 102 has a substantially square ring shape as a whole. A substantially rectangular current conducting portion 102a is formed inside the magnetic core 102 (inner circumference of the ring), and a conductor 105 such as a bus bar is inserted into the current conducting portion 102a. The current detector 100 is for detecting the current passing through the conductor 105, and the magnetic core 102 is arranged in an annular shape along the direction of the magnetic field generated when the current to be detected flows through the conductor 105. .

  As described above, the magnetic core 102 has a substantially square ring shape, and therefore the magnetic core 102 includes a pair of short side portions 102b and long side portions 102c. In addition, a gap 102d is formed in the magnetic core 102 by partially notching one long side portion 102c when viewed in the longitudinal direction. In this example, the gap 102d is positioned in the vicinity of one corner portion in the corner ring of the magnetic core 102. Therefore, when viewed in the circumferential direction of the magnetic core 102 of the gap 102d, the gap 102d is closest to one side. One short side portion 102b is located at the position.

[Secondary winding]
In the present embodiment, the secondary winding 104 is attached to the magnetic core 102. Although shown in a simplified manner in FIG. 1, the secondary winding 104 has a structure in which, for example, a conductive wire 104b is spirally wound around the outer periphery of a resin bobbin 104a (reference numeral is given in FIG. 2). The bobbin 104a has, for example, a rectangular tube shape, and the conductive wire 104b is wound along the outer peripheral surface by the required number of turns. The secondary winding 104 is attached so as to cover the outer periphery of the long side portion 102c adjacent to the gap 102d. For this reason, one end (winding start or winding end) of the secondary winding 104 is in the vicinity of the gap 102d. Is located. In this state, the axis line (spiral center line) of the secondary winding 104 substantially coincides with the center line seen in the longitudinal direction of the long side portion 102c. Although not shown, lead wires extending from the secondary winding 104 to the beginning and end of the winding respectively extend. When the current detector 100 is used, these lead wires are connected to, for example, an electric circuit (not shown). The

〔Hall element〕
In addition, the current detector 100 includes a Hall element 106. Although FIG. 1 shows the Hall element 106 separated from the magnetic core 102, the Hall element 106 is attached to the magnetic core 102 while being inserted into the gap 102 d. The Hall element 106 is an electronic component packaged by, for example, resin sealing, and terminals (for example, pin terminals) extend from the Hall element 106. When the current detector 100 is used, these pin terminals are connected to an amplifier circuit on a substrate (not shown), for example.

[Holding member]
Further, in the present embodiment, the Hall element 106 is inserted into the gap 102d while being held by the holding member 108. The holding member 108 holds the Hall element 106 in the gap 102d. The Hall element 106 can be appropriately positioned. Hereinafter, this point will be described in detail.

  FIG. 2 is a cross-sectional view (II-II cross section in FIG. 1) showing a state in which the Hall element 106 is installed in the gap 102d together with the holding member 108. As shown in FIG. 2, the holding member 108 has a substantially U-shaped cross section (or C shape), and a groove-shaped holding portion (no reference numeral in the figure) is formed inside thereof. . The holding member 108 has a pair of side walls 108a on both sides of the holding portion, and also has a connecting wall 108b that connects one end of the side walls 108a to each other. Further, flanges 108c are formed at the other ends of the respective side walls 108a, and these flanges 108c extend from the respective side walls 108a toward the outside of the gap 102d.

  The holding member 108 holds the Hall element 106 between the pair of side walls 108a in a state where the Hall element 106 is accommodated (inserted) in the holding portion. At this time, the inner method between the pair of side walls 108a substantially matches the width dimension of the Hall element 106 (reference symbol W in the figure), and the outer dimension of the holding member 108 (between the outer surfaces of the pair of side walls 108a) is It is set to be approximately equal to the entire length (reference symbol LG in the figure) of the gap 102d viewed in the magnetic field circulation direction (circumferential direction of the magnetic core 102). For this reason, the holding member 108 is inserted so as to fit in the gap 102d in a state where the Hall element 106 is accommodated in the holding portion.

  The thicknesses of the pair of side walls 108a (reference symbol T in the figure) are set to be equal to each other. For this reason, the holding member 108 holds the Hall element 106 and positions the Hall element 106 at the center position in the gap 102d. be able to. Even if the overall length (LG) of the gap 102d is constant, if the width dimension (W) differs depending on the Hall element 106, the above positional relationship can be maintained by appropriately adjusting the thickness (T) of each side wall 108a. Good. In addition, the holding member 108 is formed of a nonmagnetic material such as a resin, and thus the holding member 108 does not particularly affect the magnetic field generated in the gap 102d.

[Positioning by holding member]
Next, positioning of the Hall element 106 by the holding member 108 will be described. As described above, the holding member 108 positions the Hall element 106 at the center position of the gap 102d (the center position in the magnetic field circulation direction). The reason why this position is optimized in this embodiment is as follows. Street.

  FIG. 3 is a diagram schematically showing the distribution state of the magnetic field in the gap 102d when the current detector 100 is used. In general, in the servo type current detector 100, a reverse magnetic field is generated from the secondary winding 104 in a direction to cancel the magnetic field generated in the gap 102d by the detected current when used, so that the magnetic field is generated in the gap 102d. The current of the secondary winding 104 is controlled so as to maintain the state in which the magnetic field is lost. In this case, since the voltage signal from the Hall element 106 is almost zero, the control target system (for example, an electric circuit) can be controlled in a steady state using the voltage signal (Hall voltage) at this time as a feedback signal.

  However, as described above, the state in which the magnetic field completely disappears in the entire region in the gap 102d is a theoretical ideal state. In fact, even if the system is stable in a steady state, the gap 102d has a slight amount. There may be a residual magnetic field. According to the verification (for example, simulation analysis) performed by the inventors of the present invention, as shown in FIG. 3, there is a residual magnetic field MF2 with a certain level of strength at both side edges in the gap 102d even in a steady state. It has also been confirmed that a stronger residual magnetic field MF1 exists at the corner of the gap 102d.

  Based on the above verification results, the inventors of the present invention correctly place the Hall element 106 in the central region A that is not affected by the residual magnetic fields MF1 and MF2 even in the same gap 102d, thereby allowing the Hall element 106 in a steady state of the system. It was concluded that the voltage signal obtained from the element 106 can be close to the theoretical value (= 0). That is, since the magnetic field disappears in the region A, the theoretically appropriate value is accurately obtained as the detection signal of the current detector 100 by correctly positioning the Hall element 106 at the center position (in the region A) in the gap 102d. Therefore, the accuracy of the current detector 100 as a product can be greatly improved.

  Furthermore, as a result of manufacturing a plurality of current detectors 100 according to the present embodiment and statistically evaluating the individual performance by the inventors of the present invention, the Hall element 106 is not positioned by the holding member 108 within the gap 102d. In comparison with the case, it is confirmed that when the positioning by the holding member 108 is performed, the standard deviation is greatly improved in the output distribution of the Hall voltage.

  Furthermore, in this embodiment, since the pair of flange portions 108 c are formed on the holding member 108, the holding member 108 can be attached in a state where these flange portions 108 c are in close contact with the outer surface of the magnetic core 102. In this state, the flange portion 108c restrains the displacement of the holding member 108 in the direction orthogonal to the magnetic field rotating direction (upward in FIG. 2), stabilizes the position thereof, and the holding member 108 moves from the gap 102d. Prevents falling off. Thereby, the accuracy of the current detector 100 can be further improved by further stabilizing the state in which the Hall element 106 is positioned in the gap 102d.

[Another form of holding member]
FIG. 4 is a cross-sectional view when the Hall element 106 is positioned using a holding member 208 of another form. Another type of holding member 208 is a separate type in which the side walls 108a are separated from each other, and such holding member 208 is installed, for example, so as to sandwich the Hall element 106 from both sides in the gap 102d. . In this case as well, the holding member 208 can hold the Hall element 106 in the gap 102d and correctly position the holding member 208 at the center position thereof.

  The present invention can be implemented with various modifications without being limited to the above-described embodiment. For example, the specifications such as the specific shape, size, and thickness of the magnetic core 102 can be appropriately changed according to the characteristics of the current to be detected.

  In the embodiment, the gap 102d is formed at the corner of the magnetic core 102. However, the gap 102d may be formed at the center of the long side 102c or the short side 102b.

  In the embodiment, the current detector 100 is a servo type. However, the present invention is not limited to this type, and the present invention may be implemented as an open type current detector having no secondary winding.

  The shape of the magnetic core 102 is not limited to the square ring shape described in the embodiment, but may be other polygonal ring shapes, circular shapes, or elliptical shapes. The magnetic core 102 may be produced using a magnetic material (silicon steel plate, iron-nickel alloy, etc.) other than ferrite.

  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.

It is a perspective view showing roughly the composition of the current detector of one embodiment. It is sectional drawing (sectional drawing which follows the II-II line | wire in FIG. 1) which shows the state which installed the Hall element in the gap with the holding member. It is the figure which showed typically the distribution condition of the magnetic field in the gap at the time of use of a current detector. It is sectional drawing at the time of positioning a Hall element using the holding member of another form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Current detector 102 Magnetic body core 102a Current conduction | electrical_connection part 102b Short side part 102c Long side part 102d Gap 104 Secondary winding 106 Hall element 108,208 Holding member

Claims (3)

A magnetic core disposed in a ring shape along the circumferential direction of the magnetic field generated when the current to be detected is conducted, and a gap formed in a part thereof;
A Hall element that is arranged in the gap and outputs a voltage signal corresponding to the strength of a magnetic field generated in the gap through the magnetic core when a current to be detected is conducted;
A current detector comprising: a holding member which is inserted into the gap together with the Hall element to hold the Hall element and positions the Hall element at a predetermined position in the gap in this holding state. The current detector of claim 1,
The holding member is
A current detector, wherein the Hall element is positioned in a circumferential direction of the magnetic core within the gap. The current detector according to claim 1 or 2,
A secondary winding that is disposed in the vicinity of the gap with respect to the magnetic core and that generates a reverse magnetic field in a direction that cancels the magnetic field generated when the detected current is conducted when viewed in the circumferential direction of the magnetic core; ,
The holding member is
A current detector, wherein the Hall element is positioned at a position where the magnetic field disappears in the gap as a reverse magnetic field is generated by the secondary winding.

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