JP2013113631A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detector which effectively eliminates influences of an external magnetic field regardless of its simple structure, is easily assembled, and is suitable for downsizing.SOLUTION: In a current detector 10A, a magnetic detection element 52 for detecting density of a magnetic flux formed by a value of current flowing a bus bar 20 is provided in an area magnetically shielded by a magnetic shield 40, and a value of the current flowing the bus bar 20 is detected. In order to offset magnetic changes operating the magnetic detection element 52 by influences of the external magnetic field, the magnetic detection element 52 is installed facing a central part in the width direction of the bus bar 20 near the bus bar 20, whereas the magnetic shield 40 is symmetrically placed with respect to the bus bar 20 in such a way that a pair having the same size grip the bus bar 20 at both side edges in the width direction from outside.

Description

  The present invention relates to a current detection device that detects a current flowing in a conductor by detecting a magnetic flux density and a magnetic field strength.

  2. Description of the Related Art Conventionally, there is known a current detection device that can detect a current value flowing between a battery and a vehicle electrical component by detecting a magnetic flux generated from a current flowing in a harness connected to a battery terminal. The current detection device is attached to a part of the vehicle using a jig such as a bracket. By inserting the harness through the detection hole of the current detection device, the magnetic flux is detected at that portion.

  However, in the conventional current detection device, it is necessary to use a separate part such as a bracket in order to attach the current detector to the vehicle. For this reason, the number of parts increased and the configuration was complicated. Furthermore, since it is necessary to pass a flexible harness through the detection hole, it is necessary to enlarge the detection hole from the viewpoint of workability. For this reason, it has been difficult to reduce the size of the current detection device.

  Therefore, a vehicle current detection device has been proposed that is downsized, improves assembly workability, and has a simple configuration (see, for example, Patent Document 1). As shown in FIG. 10, in this current detection device, one end 201 of a bus bar 200 is tightened and connected to a terminal 101 of a battery 100 with a screw 102, and a current detector 300 is supported on the bus bar 200. Further, the other end 202 of the bus bar 200 is connected by a screw 402 and a terminal 401 that bites an end of a harness 400 connected to a vehicle electrical component (not shown).

  In addition, as shown in FIG. 11, a magnetic core 302 is fixed to the current detector 300 so as to surround a detection hole 304 through which the bus bar 200 penetrates in a synthetic resin detector body 301. The Hall element 303 is mounted so as to be positioned between both ends of the core 302. As a result, the vehicle current detection device can be easily configured, can be miniaturized, and can further improve the assembly workability.

  Furthermore, a current detection device as described in Patent Document 2, for example, has also been proposed. As shown in FIG. 12, the current detection device 500 is configured by a coreless current sensor that has high detection accuracy of the sensor itself and can avoid magnetic interference from the outside such as an adjacent bus bar.

  That is, this current detection device 500 is attached to the magnetic shield 501 attached to the bus bar BU, the magnetic shield 502 attached to the bus bar BV, and the bus bar BW in order to avoid the magnetic interference and use the coreless current sensor. And a magnetic shield 503.

  The magnetic shield employs a unique arrangement in order to reduce magnetic interference with the coreless current sensor mounted on the adjacent bus bar. That is, on the bus bars BU, BV, and BW arranged in parallel, the current sensors SU, SV, and SW are arranged at positions shifted alternately along the bus bars. On the other hand, the magnetic shields are similarly arranged at positions shifted alternately along each bus bar. In other words, the arrangement of the magnetic shield and the current sensor is a so-called staggered arrangement.

JP 2001-272422 A JP 2006-112968 A

  However, the current detection device described in Patent Document 1 has the following disadvantages. That is, as described above, in order to install the core 302 for collecting magnetic flux, it is necessary to provide the detection hole 304 through which the bus bar 200 is inserted, and to insert the bus bar 200 through the detection hole 304. Further, if the shape of the bus bar 200 is complicated, it is difficult to insert the bus bar 200 into the detection hole 304, so that the core 302 is enlarged because the detection hole 304 needs to be formed larger.

  Further, in the current detection device described in Patent Document 2, bus bars BU, BV, and BW are arranged side by side adjacent to each other. Therefore, in order to make the structure difficult to be affected by the magnetic field from the unnecessary adjacent generated due to this, measures such as alternating arrangement of the current sensors SU, SV, SW are necessary. For this reason, an enlargement will be brought about. As a result, the mounting environment and space are also limited.

  The present invention has been made in view of the above-described circumstances, and its object is to easily remove the influence of an external magnetic field in spite of a simple configuration, and to be easily assembled and downsized. An object of the present invention is to provide a current detection device suitable for the above.

In order to achieve the above-described object, the current detection device according to the present invention is characterized by the following (1) to (3).
(1) In a region magnetically shielded by the magnetic shield, a magnetic detection element for detecting a magnetic flux density or a magnetic field intensity formed by a current value flowing through the conductor is provided, and a current value flowing through the conductor is A current detection device for detecting with the magnetic detection element,
The magnetic detection element is installed facing the central portion in the width direction of the conductor in the vicinity of the conductor,
The pair of magnetic shields having the same dimensions are disposed symmetrically opposite the conductor in a state where both side edges in the width direction of the conductor are sandwiched from outside.
about.
(2) In the current detection device having the configuration of (1) above,
The conductor is a wide plate bus bar,
A housing formed of a non-magnetic material, having a sensor chamber that is surrounded by a wall surface and accommodates a sensor, with a bottom surface facing one surface of the bus bar;
The magnetic shield is composed of a pair of magnetic plates having the same shape symmetrically provided on both opposing wall surfaces of the sensor chamber of the housing in such a manner that both side edges of the bus bar are sandwiched from the outside. And
The magnetic field in the cross section in the bus bar width direction in the sensor chamber is generated in a symmetrical distribution pattern with the magnetic detection element as the center.
(3) In the current detection device having the above configuration (1) or (2),
The magnetic detection element includes a first sensor disposed in a central portion in the width direction in the vicinity of one surface of the bus bar in the sensor chamber, and a central portion in the width direction in the vicinity of the other surface of the bus bar. A second sensor disposed in the
The first sensor and the second sensor are arranged symmetrically with respect to the center position of the bus bar in the thickness direction.

According to the current detection device having the above configuration (1), it is possible to effectively remove the influence of the external magnetic field in spite of the simple configuration, and it is easy to assemble and is suitable for downsizing. Can be realized.
According to the current detection device having the above configuration (2), the magnetic flux density or the magnetic field strength in the cross section in the width direction of the bus bar in the sensor chamber is generated symmetrically vertically and horizontally with the magnetic detection element as the center. Yes. For this reason, when affected by an external magnetic field, it is easy to find this from the disturbance of magnetic flux density or magnetic field strength. As a result, it is possible to reliably remove the external magnetic field without overlooking it.
According to the current detection device having the configuration of (3) above, by adding the outputs from both sensors, it is possible to easily and reliably cancel the influence of the magnetic field disturbance due to the external magnetic field. Detection is possible.

  The present invention has been briefly described above. Further, details of the present invention will be further clarified by reading through the modes for carrying out the invention described below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view, partly broken, showing the configuration of the current detection device according to the first embodiment of the present invention. 2A is a plan view of the current detection device in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB showing the main part of FIG. 3A is a magnetic force distribution diagram showing the action of a magnetic field and the like in the current detection device in FIG. 1, and FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB in FIG. FIG. 4 is a magnetic force distribution diagram showing the action of a magnetic field and the like in the current detection device according to the second embodiment of the present invention. FIG. 5 is an exploded perspective view, partly broken, showing the configuration of the current detection device according to the third embodiment of the present invention. 6A is a plan view of the current detection device in FIG. 5, and FIG. 6B is a cross-sectional view taken along the line VIB-VIB showing the main part of FIG. 6A. 7A is a magnetic force distribution diagram showing the action of a magnetic field and the like in the current detection device in FIG. 5, and FIG. 7B is a cross-sectional view taken along the line VIIB-VIIB in FIG. FIG. 8 is an explanatory diagram showing a state when an external magnetic field acts on the current detection device of FIG. FIG. 9 is a graph showing a change in output voltage from each sensor of the current detection device of FIG. 5, and FIGS. 9A and 9B show the output states of the first sensor and the second sensor, respectively. Showing change. FIG. 10 is a side view showing the entire conventional current detection device. FIG. 11 is a front view showing a main part of the current detection device in FIG. FIG. 12 is an explanatory diagram showing the overall arrangement of another conventional current detection device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
[First Embodiment]
A current detection device 10A according to the present embodiment shown in FIGS. 1 and 2 includes a bus bar 20 that is a wide conductor, a housing 30 that forms a connector connecting portion α and a detection portion β, and a magnetic shield that forms a magnetic shield. 40 and a sensor main body 50.

  In the detection unit β, a magnetic detection element 52 that detects a magnetic field generated from the bus bar 20 is provided on a substrate 51 that constitutes a part of the sensor main body 50. By using this magnetic detection element 52, the bus bar 20 is based on the detected magnetic flux density (which is also synonymous with magnetic induction, but here the name is unified with the magnetic flux density B) or the magnetic field strength H. The value of the current I that flows through is calculated. A substrate 51 on which the magnetic detection element 52 is mounted is installed in the sensor chamber 32 of the housing 30. In the calculation of the current in the present invention, instead of the magnetic flux density B in the present embodiment, the magnetic flux density is B = μH (where μ is the magnetic permeability), which is an auxiliary formula in the well-known Maxwell equation. The above-described magnetic field strength H that uniquely corresponds to B may be used.

  The magnetic detection element 52 detects a magnetic flux Φ generated around the current I with respect to the flow of the current I in the bus bar 20 shown in FIG. It has the same configuration as the one. In other words, the magnetic detection element 52 of the present embodiment is disposed in the plane direction (that is, the XY plane) for detecting the magnetic flux density B of the current I flowing through the bus bar 20 and is perpendicular to the plane of the bus bar 20. The magnetic flux is not detected.

  That is, in the Z direction perpendicular to the XY plane of the bus bar 20 having a wide shape, there is almost no change in the magnetic flux due to the arrangement and configuration of the magnetic detection element 52. That is, it is a direction in which this cannot be detected. Under such circumstances, the upper side of the substrate 51 provided with the magnetic detection element 52 is structurally open, but this does not adversely affect the magnetic detection of the present embodiment.

  The magnetic detection element 52 of the present embodiment uses a Hall element utilizing the Hall effect. For example, an output voltage V proportional to the magnetic flux density B (generated according to the intensity of the current I flowing through the bus bar 20) is used. Output.

  The bus bar 20 has one end (left end in FIG. 2) attached to one end of a harness (not shown) for connecting vehicle electrical components, and the other end (right end in FIG. 2). It is attached to a battery terminal (not shown). As shown in FIG. 1 and FIG. 2, the bus bar 20 has holes 21 and 22 for screwing at both end portions. For example, a battery terminal (to avoid a short circuit) using the holes 21 is provided. It is fastened with a bolt or a screw to a terminal on the negative side (not shown), and is fastened with a bolt or a screw to one end of the harness using the hole 22.

  Further, in the bus bar 20 of this embodiment, a screw insertion hole 23 is formed so as to penetrate from the upper surface to the lower surface of the bus bar 20 at a position near the one hole 22 between the screw fixing holes 21 and 22. ing. This screw insertion hole 23 is for inserting a synthetic resin screw S as shown in FIG. 2A, and has a smaller diameter than the above-described holes 21 and 22, and a shaft portion of the screw S described later. Can be inserted in a size and form (usually round). Further, upright pieces 24 as shown in FIG. 1 protrude in an upright state toward the upper (Z) direction at the side edge portions in the vicinity of the four corners of the bus bar 20, and are formed at corresponding portions of the housing 30. By being inserted into the slit 33, it is temporarily fixed.

  The housing 30 of this embodiment is a non-magnetic material that is integrally formed of a synthetic resin material that is solidified after heat melting, and the connector connecting portion α in order from the end side closer to the battery (right side in FIG. 2). And a detection unit β. These both side surfaces will be referred to as a first side surface 30A and a second side surface 30B.

  The connector connecting portion α is for connecting a connector (not shown) attached to the signal line L. In this embodiment, a room (hereinafter referred to as a connector chamber 31) surrounded by standing walls in four directions is a connector. It is composed. The signal line L is for transmitting an electric signal corresponding to the magnitude of the magnetic flux density B detected by a magnetic detection element 52 of the detection unit β described later to a control IC unit (not shown).

  In the detection unit β, a substrate 51 is installed in a sensor chamber 32 surrounded by walls in four directions, and a magnetic detection element 52 is mounted on the substrate 51, correctly on the back surface of the substrate 51. The substrate 51 on which the magnetic detection element 52 is mounted is covered in an airtight and watertight manner by an insulating coating such as a synthetic resin (not shown). This makes it possible to avoid moisture intrusion into the electronic circuit including the magnetic detection element 52 and interference with external components.

  Further, in the detection unit β, the magnetic shield 40 is accommodated in the portion of the second side surface 30B of the housing 30 from below. Specifically, it is mounted inside the narrow groove 35 of each second side surface 30B. That is, the above-described narrow groove hole 35 penetrating vertically is provided on the second side surface 30B on both sides of the detection part β of the housing 30. The lengths and widths of these narrow groove holes 35 are sized so that a magnetic shield 40 described later can be inserted.

  On the other hand, a substantially cylindrical boss portion 34 as shown in FIGS. 1 and 2 protrudes from the other end portion of the housing 30, and the boss portion 34 has a substantially central portion on the lower surface of the housing 30. A hole 34 </ b> A that opens toward the top is formed. A screw S made of synthetic resin as shown in FIG. 2 can be screwed into the hole 34A from below.

  As a result, the magnetic shield 40 and the bus bar 20 can be mounted on the housing 30 using the synthetic resin screw S without having a protruding portion such as a caulking portion made of a metal material. For this reason, it is possible to stabilize the magnetic hysteresis and improve the accuracy of magnetic detection and current detection.

The magnetic shield 40 is composed of a magnetic plate having an appropriate thickness and size formed of an appropriate magnetic material, and in particular, two sheets having the same dimensions (particularly the height H ₁ ) and the same thickness. Consists of things. As described above, the magnetic shield 40 is externally covered with the housing 30 so as to cover the periphery of the detection unit β of the housing 30 and the bus bar 20 from the outside, and magnetically shields the magnetic shield 40.

  Specifically, the magnetic shield 40 is inserted into the narrow groove hole 35 of the second side surface 30B on both side surface portions of the detection portion β of the housing 30 as shown in FIG. Y) The magnetic detection element 52 and the bus bar 20 are surrounded with respect to the direction. Thereby, magnetic shielding is performed for the magnetic field formed by the bus bar 20. At the same time, magnetic shielding of an external magnetic field is performed so that a magnetic field generated from various electrical components installed in the vicinity of the current detection device 10A does not adversely affect the magnetic detection element 52.

  In addition, as shown in FIG. 3, each magnetic shield 40 has a magnetic path M formed therein, and the periphery of the lower end 40D and the upper end 40U of each magnetic shield 40 is not particularly different between corresponding ends. In the meantime, the magnetic flux Φ is formed in a predetermined distribution pattern.

  Therefore, according to the in-vehicle current detection device 10A according to the present embodiment, the magnetic shield 40 is provided, and the electromagnetic shielding effect by the magnetic shield 40 is ensured. The current flowing through the bus bar 20 can be accurately detected by the magnetic detection element 52.

  As a result, even when an external magnetic field is generated around the Hall element used as the magnetic detection element 52, or when a relay or a motor is installed nearby, the influence of the magnetic shield 40 is affected by the electromagnetic shielding action. Can be avoided. That is, it can be avoided that the magnetic detection operation is hindered due to the magnetic field generated from the relay or motor. Moreover, the influence of geomagnetism and high-voltage electric wires can be effectively avoided as the influence of the environment when the vehicle travels.

  In addition, according to the present embodiment, the magnetic shield 40 is fitted and fixed to the housing 30 from one end side, so that the positioning of the magnetic shield 40 and the bus bar 20 attached to the housing 30 can be easily positioned. It can be carried out. As a result, the mounting work of the magnetic shield 40 to the bus bar 20 and the housing 30 can be made efficient.

Next, the operation of the magnetic detection element 52 for current detection according to the present invention will be described with reference to FIG.
In the current detection device 10A according to the present embodiment, as shown in FIG. 3, when the current I flows through the bus bar 20, as is well known, the current I flows around the bus bar 20 according to Ampere's law, particularly according to the right-handed screw law. A magnetic field is formed having clockwise magnetic field lines along the flow.

  On the other hand, in the current detection device 10 </ b> A of the present embodiment, a magnetic shield 40 composed of a pair of flat magnetic plates is installed so as to surround both sides in the width direction of the bus bar 20. For this reason, a magnetic path M is formed inside the magnetic shield 40 as schematically shown in FIG.

  Thus, at the same time as the magnetic path M is formed in each magnetic shield 40, the lower end 40D and the upper end 40U of each magnetic shield 40 are connected to the corresponding counterpart end as described above. A flux that is a bundle of magnetic flux lines, that is, a magnetic flux Φ is formed in a predetermined distribution pattern.

  In particular, the magnetic detection element 52 installed at the center in the width direction of the bus bar 20 and below the upper end 40U of each magnetic shield 40 is horizontal to the thickness (Z) direction. Magnetic flux Φ penetrates in the (−Y) direction. Thereby, in the Hall element constituting the magnetic detection element 52, a Hall electric field (electric field strength E) corresponding to the magnetic flux density B is generated, and the current I in the bus bar 20 can be detected correspondingly. it can.

  As described above, in the current detection device 10A of the present embodiment, the magnetic shield 40 is configured by a pair of flat plate-like ones, which is substantially compared to a magnetic shield having a generally U-shaped cross section. It is a structure in which the central part is missing. Therefore, when the current detection is performed on a large bus bar having a structure in which a large current flows, it is not necessary to increase the width corresponding to the wide bus bar. That is, the magnetic shield 40 having the same size as that in the case of detecting a small current in a narrow bus bar can be used. Moreover, the magnetic shield 40 can be easily assembled to the housing 30.

  Therefore, according to the current detection device 10A of the present embodiment, it is possible to detect a current up to ± 600 A, for example, approximately twice that of a current detection device using a magnetic shield having a substantially U-shaped cross section. Moreover, as compared with the case where a magnetic seal having a substantially U-shaped cross section is used, the processing is facilitated, the weight can be reduced, and the cost can be further reduced. In addition, the installation space is reduced and the restrictions on the mounting environment are eased.

  Further, along with the trend of increasing current, conventionally, it was inevitable to increase the size of the magnetic shield having a substantially U-shaped cross section, but according to this embodiment, even when detecting a large current, Not only can the size be reduced, but also the cost can be reduced.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described in detail with reference to FIG.
The current detection device of the present embodiment uses the same material as that of the current detection device 10A of the first embodiment for the current values of a plurality of bus bars arranged in parallel next to each other, here two bus bars 20 ₁ and 20 ₂ , ones such as the shape, i.e., are both allowed juxtaposed adjacent the current sensing device 10A ₁ and the current detection device 10A ₂ together with such the same size.

In particular, the magnetic shields 40R ₁ , 40L ₁ and 40R ₂ , 40L ₂ that are disposed so as to surround the magnetic detection elements 52 ₁ , 52 ₂ that are sensor chambers from both sides are connected to the bus bars 20 ₁ , 20 _2. Are arranged symmetrically. That is, this is to cancel magnetic changes acting on the magnetic sensing elements on the opposite side due to the influence of the external magnetic field.

Also, the magnetic detection element ₅₂ 1, 52 ₂ is the magnetic detection elements, in the vicinity of the bus bar ₂₀ 1, 20 _2, are installed in particular bus bar ₂₀ 1, 20 a position corresponding to the central portion of the _second width direction Yes.

That is, in the present embodiment, unlike the conventional configuration in which the current detection devices are alternately arranged, the current detection devices 10A ₁ and 10A ₂ are arranged side by side along the width direction of the bus bars 20 ₁ and 20 _2. It has a configuration in which two are arranged.

The current detection devices 10A ₁ and 10A ₂ arranged in parallel as described above are configured to detect the current value with high accuracy while suppressing the influence of the external magnetic field formed by the bus bars 20 adjacent to each other. Note that the effect of an external magnetic field where the bus bar 20 _1, 20 ₂ adjacent to each other on the other side, is that the adverse effects of mutual interference of the magnetic field.

In the present embodiment, among the magnetic shields that are the magnetic shields of the current detection devices 10A ₁ and 10A ₂ , they are adjacent to each other's magnetic shield, that is, between the magnetic shields 40R ₁ and 40L ₂ . A magnetic body 40M, which is a magnetic plate, is separately provided and interposed at the center position of the gap. This increases the magnetic shielding effect from the other side adjacent to each other, in other words, external magnetic field resistance is provided in a reinforcing manner.

Next, the operation of this embodiment will be described.
i) When currents of the same direction and the same or almost the same magnitude flow through the two bus bars 20 ₁ and 20 ₂ :
In this case, in the vicinity of the magnetic shield 40R ₁ and 40L _2, in opposite directions, and, since the magnetic field of the same or substantially the same size are formed, it affects the magnetic flux Φ is offset to the opposite sides to each other Is done. As a result, it is possible to accurately detect the current values of the respective bus bars 20 ₁ and 20 _{2 in} the current detection devices 10A ₁ and 10A ₂ .

ii) When two bus bars 20 ₁ and 20 ₂ have currents flowing in the same direction and having significantly different magnitudes:
In this case, the center position of the gap between the magnetic shield 40R ₁ and 40L _2, with intervening magnetic material 40M, which is a magnetic plate imparts an external magnetic field tolerance, the bus bar towards flowing otherwise large current Can be magnetically shielded by the magnetic body 40M.
Therefore, it is possible to suppress the influence of the external magnetic field from the bus bar through which the large current flows into the space between the pair of magnetic shields, which is the sensor chamber of the current detection device through which a small current flows through the bus bar. As a result, the current values of the respective bus bars 20 ₁ and 20 ₂ can be accurately detected by the current detection devices 10A ₁ and 10A ₂ .

  When a plurality of bus bars are installed adjacent to each other, each conventional current detection device requires an area that is twice or more the sensor size as an arrangement space on the current path. On the other hand, in the present embodiment, only half the conventional space, that is, an area having the same dimensions as the sensor is required.

As described above, in the present embodiment, the current detection devices 10A ₁ and 10A ₂ are arranged side by side in a row along the width direction of the bus bars 20 ₁ and 20 ₂ . In particular, the magnetic shields 40R ₁ , 40L ₁ and 40R ₂ , 40L ₂ are arranged symmetrically with respect to the bus bars 20 ₁ , 20 ₂ . In other words, this is for canceling out magnetic changes that act on the magnetic sensing elements on the opposite side due to the adverse effect of the external magnetic field due to mutual interference. Therefore, it is not necessary to have a configuration in which the current detection devices as in the prior art are arranged in a staggered manner.

[Third Embodiment]
Next, a current detection device 10B according to a third embodiment of the present invention will be described in detail with reference to FIGS. In the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals to avoid redundant description.

  Unlike the current detection device 10 </ b> A of the first embodiment, the current detection device 10 </ b> B of the present embodiment configures the magnetic detection element 52 </ b> A and the second sensor that configure the first sensor of the sensor body 50 at the upper and lower positions of the bus bar 20. A magnetic detection element 52B is disposed. In this embodiment, in order to arrange these magnetic detection elements 52A and 52B above and below the housing 30 ', the boards 51A and 51B on which they are mounted are respectively attached above and below the housing 30'. Also, the size of the magnetic shield 40 'is slightly different from that of the first embodiment in the height direction.

  In the housing 30 ', as shown in FIG. 6B, a sensor chamber similar to the upper sensor chamber 32A is provided so that a substrate 51B on which the magnetic detection element 52B is mounted is installed on the lower surface side of the bus bar 20. 32B is formed. The magnetic detection element 52B is mounted on the upper surface with respect to the substrate 51B.

As shown in FIG. 7, the magnetic shield 40 ′ is composed of a pair of magnetic plates similar to the magnetic shield 40 of the first embodiment, but the upper and lower magnetic detection elements 52A and 52B are magnetized from an external magnetic field. having a height dimension H ₂ as to shield.

That is, the magnetic shield 40 ′ has the same magnetic shielding characteristics at each of the magnetic detection elements 52 A and 52 B with respect to an unnecessary external magnetic field, so that the height (Z The shielding height from the center position O in the direction) is the same. That is, the magnetic shields 40 ′ are magnetically shielded up to the same height h _{2 with} respect to the magnetic detection elements 52 A and 52 B separated from the center position O of the bus bar 20 by the same distance h ₁ .

Next, the operation of the magnetic detection elements 52A and 52B for current detection according to the present embodiment will be described with reference to FIGS.
In the current detection device 10B of the present embodiment, as shown in FIG. 7, when the current I flows through the bus bar 20, as in the case of the first embodiment, a current is passed around the bus bar 20 according to the right-handed screw rule. A magnetic field having a clockwise magnetic field line along the flow of I is formed.

  That is, in the current detection device 10B of the present embodiment, a magnetic shield 40 ′ composed of a pair of flat magnetic plates is installed in a state surrounding both sides of the bus bar 20 in the width (Y) direction. Yes. For this reason, as schematically shown in FIG. 7A, a magnetic path M similar to that in the first embodiment is also formed in the magnetic shield 40 ′.

  Thus, the magnetic path M is formed in each magnetic shield 40 ', and at the same time, the lower end 40'D and the upper end 40'U of each magnetic shield 40' are the same as in the case of the first embodiment. Similarly, for example, a magnetic flux Φ as shown in FIG. 7 is formed in a predetermined distribution pattern between corresponding end portions. In FIG. 7, a typical magnetic flux pattern is shown, but the pattern is not limited to this pattern.

  In particular, the magnetic detection element 52A installed just above the center portion in the width direction of the bus bar 20 and below the upper end 40'U of each magnetic shield 40 'has a current flowing through the bus bar 20, The magnetic flux Φ penetrates in the horizontal (−Y) direction orthogonal to the thickness (Z) direction. Therefore, the magnetic flux density B generated in the inherent distribution pattern accompanying the current from the bus bar 20 acts on the magnetic detection element 52A.

  That is, in the Hall element constituting the magnetic detection element 52A, a Hall electric field having a strength corresponding to the magnitude of the magnetic flux density B (that is, the strength of the electric field) is generated, and the output voltage V corresponding to this magnitude is generated. Is obtained. Then, the current value of the bus bar 20 can be detected from an appropriate relational expression showing a relationship between the output voltage V and the current value i of the bus bar 20 that are determined in advance, a correspondence table, or the like.

  On the other hand, the magnetic detecting element 52B has the same action. That is, the magnetic detection element 52B installed immediately below the center portion in the width direction of the bus bar 20 and above the lower end 40′D of each magnetic shield 40 ′ has a thickness (Z) direction. On the other hand, the magnetic flux Φ penetrates in a horizontal (−Y) direction orthogonal to the direction. Accordingly, since the magnetic flux density B associated with the current I from the bus bar 20 acts on the magnetic detection element 52B, a Hall electric field having a strength corresponding to the magnitude of the magnetic flux density B (electric field strength E) is generated. Finally, the current value of the bus bar 20 corresponding to this size can be detected.

  By the way, in this embodiment, the magnetic detection element 52A and the magnetic detection element 52B are arranged symmetrically with respect to the bus bar 20. Therefore, when the external magnetic field does not act on the current detection device 10B, it is expected that the current values detected by the magnetic detection element 52A and the magnetic detection element 52B are theoretically the same value. However, when the current values detected by both the magnetic detection elements 52A and the magnetic detection elements 52B are different, it is expected that some external magnetic field is acting.

Even in such a case, according to the current detection device 10B of the present embodiment, it is possible to detect a highly accurate current value by removing the influence of the external magnetic field C shown in FIG.
That is, as shown in the figure, when the external magnetic field is not acting, the magnetic detection elements 52A and 52B have the same magnetic flux density B because of the vertically symmetrical arrangement. Only the direction of the magnetic flux Φ is reversed.

Therefore, when the external magnetic field C acts on the magnetic detection elements 52A and 52B, the Hall electric field (that is, the strength of the electric field) changes and fluctuates by an amount corresponding to the external magnetic field C. That is, as shown in FIGS. 9A and 9B, when the external magnetic field is not acting on the magnetic detection element 52A and the magnetic detection element 52B, the output voltage graphs A ₁ and B ₁ (solid line portions) are assumed. . On the other hand, when a uniform external magnetic field acts, the output voltages from the magnetic detection element 52A and the magnetic detection element 52B shift in opposite directions as shown in graphs A ₂ and B ₂ (dotted line portions). As a result, a change ΔV in the output voltage V proportional to the change in the magnetic flux density B due to the external magnetic field C is received, and an output voltage reflecting this change ΔV is output.

となる。
従って、この平均値を求めることで、バスバー２０の電流値が算出可能となる。 However, when the external magnetic field C acts uniformly on the magnetic detection elements 52A and 52B, the change in the output voltage V from the magnetic detection elements 52A and 52B is ± ΔV, only the sign is different and the absolute value is the same. Become. Therefore, adding both output voltages cancels. That is,

It becomes.
Therefore, the current value of the bus bar 20 can be calculated by obtaining this average value.

  For the output relationship of each sensor, that is, the magnetic detection elements 52A and 52B, refer to [Table 1] below.

  As described above, according to the present embodiment, two magnetic detection elements are required. If these two magnetic detection elements 52A and 52B are arranged vertically symmetrically with respect to the position of the bus bar 20, an external magnetic field is provided. Can be canceled conveniently. As a result, even in a place where an external magnetic field other than the electric wires and magnets to be detected exists, the influence can be removed and highly accurate current detection can be performed.

  Even in the case where the two magnetic detection elements are symmetrically arranged as in the present embodiment, the external magnetic field is canceled if the conventional magnetic shield has a substantially U-shaped cross section. Note that you can't.

  Moreover, according to this embodiment, about the magnetic plate which is each magnetic shield 40 ', what has the same dimension formed with the same material should just prepare, and arrange | position with the bus bar 20 symmetrically. Therefore, it is not necessary to examine the shape, thickness, material, etc. as in the prior art.

  In the present invention, by laying out the present embodiment, each magnetic shield having the symmetrical arrangement as described above is installed on the bus bar even if no magnetic shield is provided, and the output voltage is described above. By performing such an operation, it is possible to detect current with high accuracy. As a result, basically, a bus bar and two magnetic detection elements are sufficient, so that a magnetic shield is not required to be installed, so that a significant reduction in size, weight, and cost can be achieved.

  As described above, in the current detection device of the present invention, the magnetic shield is composed of a pair of flat plate-like ones, and the center portion thereof is substantially compared with that of a magnetic shield having a generally U-shaped cross section. It is a deficient structure. Therefore, when the current detection is performed on a large bus bar having a structure in which a large current flows, it is not necessary to increase the width corresponding to the wide bus bar. In other words, a magnetic shield having the same dimensions as in the case of detecting a small current in a narrow bus bar can be used.

  Therefore, according to the current detecting device of the present invention, a conventional magnetic shield having a substantially U-shaped cross section is used with a simple configuration in which a pair of thin magnetic shields having the same size are arranged symmetrically. Compared to the current detection device, for example, current detection up to ± 600 A, which is approximately twice as much, is possible. Moreover, in the conventional magnetic shield having a substantially U-shaped cross section, it is necessary to increase the thickness at the time of detecting a large current, but in the present invention, this is not necessary, and a large current can be detected with a light weight.

  Note that the current detection device of the present invention is not limited to application as a part of a system in a vehicle as in these embodiments. For example, as long as it includes a bus bar or the like, it can be used in various fields. Application as a current detection device is possible.

10A, 10A ₁ , 10A ₂ , 10B Current detection device 20 Bus bar (conductor)
23 Screw insertion hole 24 Standing piece 30 Housing 30B Second side 31 Connector chamber 32, 32A, 32B Sensor chamber 35 Narrow groove 40, 40 'Magnetic shield (magnetic shield)
40D Lower end of magnetic shield 40M Magnetic body 40U, 40'U Upper end of magnetic shield 50 Sensor body 51 Substrate 52 Magnetic detection element 52A First sensor (magnetic detection element)
52B Second sensor (magnetic detection element)
A ₁ Graph when an external magnetic field is not acting on the first sensor A ₂ Graph when an external magnetic field is acting on the first sensor B Magnetic flux density (magnetic induction)
B ₁ Graph when an external magnetic field is not applied to the second sensor B ₂ Graph when an external magnetic field is applied to the second sensor H Magnetic field strengths H ₁ and H ₂ Magnetic shield (magnetic shield) height h1 Height from the bus bar (conductor) to the sensor M Magnetic path S Synthetic resin screw α Connector connection part β Detection part Φ Magnetic flux

Claims (3)

A magnetic detection element for detecting a magnetic flux density or a magnetic field intensity formed by a current value flowing through the conductor is provided in a region magnetically shielded by the magnetic shield, and the current value flowing through the conductor is detected by the magnetic detection. A current detection device for detecting with an element,
The magnetic detection element is installed facing the central portion in the width direction of the conductor in the vicinity of the conductor,
The pair of magnetic shields having the same dimensions are disposed symmetrically opposite the conductor in a state where both side edges in the width direction of the conductor are sandwiched from outside.
A current detection device characterized by that. The conductor is a wide plate bus bar,
A housing formed of a non-magnetic material, having a sensor chamber that is surrounded by a wall surface and accommodates a sensor, with a bottom surface facing one surface of the bus bar;
The magnetic shield is composed of a pair of magnetic plates having the same shape symmetrically provided on both opposing wall surfaces of the sensor chamber of the housing in such a manner that both side edges of the bus bar are sandwiched from the outside. And
The magnetic field in the cross section in the bus bar width direction in the sensor chamber is generated in a symmetrical distribution pattern with the magnetic detection element as the center.
The current detection device according to claim 1. The magnetic detection element includes a first sensor disposed in a central portion in the width direction in the vicinity of one surface of the bus bar in the sensor chamber, and a central portion in the width direction in the vicinity of the other surface of the bus bar. A second sensor disposed in the
The first sensor and the second sensor are arranged symmetrically with respect to the center position in the thickness direction of the bus bar.
The current detection device according to claim 1, wherein:

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