JP5952652B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor characterized by a shield structure.

  A current sensor for detecting a current flowing in a current path (for example, a bus bar or the like) connecting an in-vehicle battery and a vehicle electrical component of an automobile is known (see Patent Document 1 and Patent Document 2).

  As shown in FIGS. 6A and 6B, the current sensor 100 of Patent Document 1 includes a sensor main body 200 and a shield 300 fixed to the sensor main body 200, and includes a sensor main body 200 and a shield 300. The current path 400 is disposed between them, and the current flowing through the current path 400 is detected. The current is measured by detecting the magnetic intensity by the magnetic detection element 220 mounted on the substrate 210 attached to the sensor body 200 and outputting electric power corresponding thereto. The shield 300 has a substantially “U” shape and completely surrounds the back surface of the current path 400 (see FIG. 6B). It is disclosed that with this configuration, a highly reliable current sensor 100 without magnetic distortion can be realized. FIG. 6B is not disclosed in Patent Document 1, but is drawn in order to clarify the difference from the configuration of the present invention.

  Further, in the current sensor of Patent Document 2, the magnetic detection element is provided at a position away from the center position in the width direction perpendicular to the current flow by a predetermined distance in the width direction. Thereby, the frequency characteristic band of the magnetic detection element can be widened to improve the frequency characteristic. It is also disclosed that the current flowing through the current path can be measured by detecting the magnetic field in the width direction.

JP 2010-223868 A Japanese Patent No. 4515855

  In the current sensor 100 described in Patent Document 1, the shield 300 completely covers the current path 400 from the back surface at the attachment portion of the current sensor 100. For this reason, an eddy current generated by the current flowing in the current path 400 is generated, and there is a drawback that the phase of the magnetic field detected by the magnetic detection element 220 is delayed from the phase of the current. Particularly at a high current of high frequency, the magnetic saturation of the shield is expected, and the linear relationship between the magnetic flux density detected by the magnetic detection element 400 and the current is disrupted, making it difficult to measure within the error tolerance. It was happening. In the current sensor described in Patent Document 2, although the magnetic detection element is shifted in the width direction, a high current sensitivity is obtained by bringing the magnetic detection element close to the current path instead of providing a shield. Therefore, for example, there is a problem that it is easily affected by a magnetic field generated from an adjacent magnetic field in three-phase alternating current or an adjacent electric component, and it is difficult to measure an accurate current value.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a highly reliable current sensor by improving high-speed response for detecting a magnetic field generated by a current flowing in a current path. .

In order to achieve the above-described object, the current sensor according to the present invention is characterized by the following (1).
(1) A current sensor installed in a current path through which current flows,
A sensor body having a substrate and a magnetic detection element mounted on the substrate;
A pair of shields paired by a first shield and a second shield;
With
The first shield is composed of only a flat plate-like fitting portion and a flat plate-like flat portion extending from the upper end portion of the fitting portion in a direction substantially perpendicular to the fitting portion,
The second shield is composed only of a flat fitting portion,
The fitting portion of the first shield and the fitting portion of the second shield are respectively fixed so as to extend along the vertical direction on both sides in the width direction of the sensor body and to face each other.
The flat portion of the first shield extends from the upper end of the fitting portion of the first shield toward the center in the width direction of the sensor body,
On the end portion of the fitting portion of the first and the second shield and the previous end of the flat portion of the shield is spaced apart,
The magnetic detection element is on the second shield side in the width direction with respect to the center in the width direction of the sensor body , and on the second shield side in the width direction with respect to the tip of the flat portion of the first shield. Arranged ,
That.

  According to the current sensor of (1) above, the magnetic field phase in the magnetic detection element is not delayed, the high-speed response can be improved, and the influence from magnetic interference is prevented as much as possible from the adjacent current path. Since the leakage magnetic flux is applied to the magnetic detection element only in the vertical direction, a current sensor can be provided in which the magnetic phase error is reduced and the magnetic saturation is reduced.

  According to the present invention, since the magnetic detection element is disposed at a position closer to one shield than the central position of the shield, the magnetic field phase in the magnetic detection element is not delayed, and the response is improved. In particular, a current sensor excellent in high-speed response can be provided. Furthermore, the influence of electromagnetic noise directed to the magnetic detection element can be reduced by making the shape of the shield L-shaped. In addition, since the shield is paired and the end portions are separated from each other, magnetic saturation is reduced, and even a large current can be measured with high accuracy.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is an exploded perspective view showing an embodiment of a current sensor according to the present invention. 2 is a cross-sectional view of the current sensor according to FIG. 3 is a cross-sectional view of the current sensor BB according to FIG. FIG. 4A is a comparative graph of the 90% -90% response time according to the configuration of the prior art and the embodiment of the present invention, and FIG. 4B is a graph for explaining the 90% -90% response time. FIG. 5 is a graph showing the performance in terms of current value and magnetic flux density. 6 (a) and 6 (b) show a conventional current sensor, FIG. 6 (a) is an exploded perspective view, and FIG. 6 (b) is a longitudinal sectional view.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  A current sensor which is an embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view of the current sensor, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line BB in FIG.

  The current sensor 1 includes a sensor main body 2 and a shield 3 fixed to the sensor main body 2, and detects a current flowing through a current path 4 attached to the sensor main body 2. The current sensor 1 is attached to, for example, a current path that connects an in-vehicle battery of an automobile and a vehicle electrical component.

  In the sensor body 2, a substrate 21 on which a circuit and the like are mounted is accommodated in a casing formed from an insulating synthetic resin or the like. A magnetic detection element 22 is attached to the substrate 21. The magnetic detection element 22 is an element that measures a magnetic field generated in the current path 4, and uses, for example, a semiconductor Hall element using a Hall effect generated by Lorentz force received by carriers in the magnetic field or a magnetic impedance effect by an amorphous magnetic material. Magnetic impedance element, etc. The current sensor 1 outputs a voltage value having a value proportional to the magnetic field detected by the magnetic detection element 22 via an amplification circuit or the like mounted on the substrate 21.

  The shield 3 is made of a high magnetic permeability material such as permalloy or a silicon steel plate, and is formed of a thin plate. The shield 3 is a pair of left and right, and is fixed to both sides of the sensor body 2. The current path 4 is attached to the lower part of the sensor body 2, and the shield 3 is attached from the upper part of the sensor body 2.

  The shield 3 includes a first shield 3S and a second shield 3T. The first shield 3S includes a flat fitting portion 31S that fits into a fitting hole 25 formed in the side portion of the sensor body 2, and a flat portion that extends in a direction substantially perpendicular to the fitting portion 31S. 32S. The right angle direction is a direction from the side of the sensor body 2 toward the center line X at the center. On the other hand, the second shield 3T includes a flat fitting portion 31T. The end portion 33S of the flat portion 32S of the first shield 3S and the end portion 33T of the fitting portion 31T of the second shield 3T are arranged and fixed on the upper portion of the sensor body 2 so as to face each other and be separated from each other. . Accordingly, it can be said that the shields 3S and 3T do not completely surround the current path 4 and have an opening (slit).

  The magnetic detection element 22 is positioned on the left side (in the drawing) of the center line X of the sensor body 2. That is, it is mounted on the substrate 21 so as to be close to the second shield 3T. In other words, the magnetic detection element 22 is arranged from the second shield 3 </ b> T in the direction away from the end 33 </ b> S of the flat portion 32 </ b> S protruding in the center line X direction of the sensor body 2 with the length L. Note that a flat portion may be partially formed at the end portion 33T of the second shield 3T.

  The current path 4 is a bus bar or conductor formed on a flat plate through which an alternating current or the like flows, and is attached to the lower part of the sensor body 2.

  According to the current sensor 1 of the present invention, the magnetic field phase at the magnetic detection element 22 is not delayed by being positioned on the left side (on the drawing) of the center line X of the sensor body 2, and particularly, high-speed response. Can be realized. In addition, since the L-shaped first shield 3 </ b> S is provided on one side of the current path 4, the current sensor 1 that suppresses magnetic interference from the periphery can be provided. Further, a uniform current density distribution in the cross section of the current path 4 is obtained, the responsiveness of the magnetic detection element 22 is improved, the residual magnetic field is suppressed, and the offset error can be reduced. Further, since the magnetic flux leaking from the current path 4 of the adjacent phase is applied to the magnetic detection element 22 only in the vertical direction, the magnetic field phase error is reduced.

  FIG. 4A is a comparative graph of 90% -90% response time (μs) when the current varies at 100 A / μS according to the configuration of the prior art and the embodiment of the present invention. As shown in FIG. 4B, the 90% -90% response time is a voltage value (output voltage 90%) proportional to the corresponding magnetic field with respect to the current (input current) output 90% flowing in the current path 4. ) Is a response time measured by the magnetic detection element 22. In the actual measurement result based on FIG. 4A, the response time of the prior art is improved from 50 μs to the response time of 6 μs of the present invention (the response time of 6 μs is the theoretical value of the magnetic detection element used for the actual measurement) (improvement of about 90%). The effect of the configuration of the shield 3 clearly appears, and the response of the magnetic detection element 22 is improved even when the current fluctuates quickly, and particularly high-speed response can be secured.

  FIG. 5 is a graph showing the performance in terms of current value and magnetic flux density.

  The shield 3 is securely fixed to the sensor body 2 by the fitting of the fitting portion 31 and the fitting hole 25. As a result, the relative positional relationship between the protrusion amount (length L) of the flat portion 32 and the magnetic detection element 22 is extremely stable. In particular, since there is a difference in offset error due to a difference in length L, it is important to maintain a certain length L. Since the fixing is excellent in earthquake resistance, it becomes extremely easy to maintain the optimum offset error value.

  In the graph of FIG. 5, the vertical axis represents the magnetic flux density (mT) inside the shield plate, and the horizontal axis represents the current (A). As understood from this graph, when the current (A) increases, magnetic saturation is likely to occur (see the curve). However, in the present invention, compared to the conventional case, magnetic saturation occurs even when a high-frequency large current flows. It is possible to extend the section where the linearity is maintained (linear section).

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

DESCRIPTION OF SYMBOLS 1 Current sensor 2 Sensor main body 3 Shield (3S 1st shield, 3T 2nd shield)
4 Current path 21 Substrate 22 Magnetic detection element 31 Fitting portion 32 Flat portion 33 End portion L Length

Claims (1)

A current sensor installed in a current path through which current flows,
A sensor body having a substrate and a magnetic detection element mounted on the substrate;
A pair of shields paired by a first shield and a second shield;
With
The first shield is composed of only a flat plate-like fitting portion and a flat plate-like flat portion extending from the upper end portion of the fitting portion in a direction substantially perpendicular to the fitting portion,
The second shield is composed only of a flat fitting portion,
The fitting portion of the first shield and the fitting portion of the second shield are respectively fixed so as to extend along the vertical direction on both sides in the width direction of the sensor body and to face each other.
The flat portion of the first shield extends from the upper end of the fitting portion of the first shield toward the center in the width direction of the sensor body,
On the end portion of the fitting portion of the first and the second shield and the previous end of the flat portion of the shield is spaced apart,
The magnetic detection element is on the second shield side in the width direction with respect to the center in the width direction of the sensor body , and on the second shield side in the width direction with respect to the tip of the flat portion of the first shield. Arranged ,
A current sensor.

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