JP6275941B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor provided with a shield.

  2. Description of the Related Art A current sensor that detects a current flowing in a current path (for example, a bus bar) that connects an in-vehicle battery and a vehicle electrical component is known. An example of this type of current sensor is shown in FIGS. 7A and 7B (see Patent Document 1).

  7 (a) and 7 (b) show a conventional current sensor, FIG. 7 (a) is an exploded perspective view, and FIG. 7 (b) is an enlarged vertical sectional view of a main part. The current sensor 100 includes a sensor main body 200 and a shield 300 fixed to the sensor main body 200, and a current path 400 is disposed between the sensor main body 200 and the shield 300 to detect a current flowing through the current path 400. ing. The current is measured by detecting the magnetic intensity by the magnetic detection element 220 mounted on the substrate 210 attached to the sensor main body 200 and outputting a voltage corresponding to the magnetic intensity. The shield 300 has a substantially “U” shape and completely surrounds the back surface of the current path 400 (see FIG. 7B). It is disclosed that with this configuration, a highly reliable current sensor without magnetic distortion can be realized.

JP 2010-223868 A

  In the current sensor 100 described in Patent Literature 1, in particular, the shield 300 completely covers the current path 400 from the back surface at the mounting 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. This is particularly noticeable at a high frequency and a large current, causing a problem that does not meet the requirements for high-speed response.

  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) and (2).
(1) A current sensor for detecting a current flowing through a flat current path,
A substrate, a magnetic detection element mounted on the substrate and disposed near the plate surface of the current path, and a pair of surrounding the magnetic detection element and the current path so as to circulate around an axis of the current path A shield plate,
The pair of shield plates is
An element-side slit located in a direction away from the current path in the orthogonal direction perpendicular to the plate surface of the current path, and a position farther from the magnetic detection element than the current path in the orthogonal direction. Are separated from each other by current path side slits at positions away from each other,
The pair of shield plates is
A pair of flat fitting portions extending in the orthogonal direction, and extending from the end on the current path side slit side of each of the pair of fitting portions toward each other in a direction along the plate surface of the current path. A pair of flat portions, and the pair of flat portions are disposed so as to overlap with a part of the current path in the orthogonal direction. A road-side slit is defined, and the element-side slit is defined by an end of the pair of fitting portions on the element-side slit side,
The entire substrate is
In the orthogonal direction, the pair of fitting portions are positioned within the extending range , and in the direction along the plate surface of the current path, are positioned within the range between the pair of fitting portions. , That.
(2) A current sensor configured as described in (1) above,
The pair of shield plates is
The length in the extending direction of the flat part is the same.

According to the current sensor of (1) above, the eddy current generated in the current path is suppressed and the delay generated in the magnetic field phase detected by the magnetic detection element is suppressed. Thereby, in particular, the generation of eddy currents in the current path is suppressed, and the delay of the magnetic field phase detected by the magnetic detection element can be eliminated, so that a current sensor with good high-speed response can be provided. Furthermore, a uniform current density distribution in the cross section of the current path is obtained, and the responsiveness of the magnetic detection element is improved.
According to the current sensor of (2) above, the residual magnetic field is suppressed and the offset error can be reduced.

  According to the present invention, the shield is paired and the ends of the shield are separated from each other, thereby suppressing the eddy current generated in the prior art and eliminating the phase lag of the magnetic field detected by the magnetic detection element. Thus, it is possible to provide a current sensor excellent in high-speed response.

  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. FIG. 2 is a cross-sectional view of the current sensor according to FIG. 3A is a longitudinal sectional view of the current sensor according to FIG. 1, and FIG. 3B is a graph showing the relationship between the length of the flat portion of the shield and the phase difference. FIG. 4A is an explanatory diagram showing a magnetic field generated in a current path when there is no shield, and FIG. 4B is an explanatory diagram showing a magnetic field when the shield of the present invention is provided. FIG. 5A is a comparative graph of 90% -90% response time according to the configuration of the prior art and the embodiment of the present invention, and FIG. 5B is a graph for explaining 90% -90% response time. FIG. 6 is a graph showing the performance in terms of current value and magnetic flux density. 7A and 7B show a conventional current sensor, in which FIG. 7A is an exploded perspective view and FIG. 7B 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.

  With reference to FIG. 1 and FIG. 2, the current sensor which is one Embodiment of this invention is demonstrated.

  FIG. 1 is an exploded perspective view of the current sensor 1, and FIG. 2 is a cross-sectional view of the current sensor 1. The current sensor 1 is composed of a sensor body 2 and a shield 3 fixed to the sensor body 2, and a current path 4 is arranged between the sensor body 2 and the shield 3 to detect a current flowing in the current path 4. To do. 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 main body 2, a substrate 21 on which a circuit or the like is mounted is accommodated in a casing formed of an insulating synthetic resin or the like. A magnetic detection element 22 is mounted on 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 material having a high magnetic permeability such as permalloy or a silicon steel plate, and is formed of a substantially L-shaped thin plate. The shield 3 is a pair of left and right, and is fixed to both sides of the sensor body 2. The procedure for assembling the shield 3 is to attach the shield 3 to the lower part of the sensor body 2 so as to surround the current path 4 after the current path 4 is attached to the lower part of the sensor body 2. In addition, the shield 3 includes a fitting portion 31 that is fitted to each side portion of the housing that forms the sensor body 2, and a flat portion 32 that extends in a direction substantially perpendicular to the fitting portion 31. . And each flat part 32 of the shield 3 is arrange | positioned on the same plane, and each edge part 33 of the flat part 32 opposes and spaces apart, and it is arrange | positioned and fixed to the lower part (refer FIG. 2) of the sensor main body 2. FIG. Is done. Accordingly, a part of the current path 4 is covered with the flat portion 32. In other words, it can be said that the shield 3 does not completely surround the current path 4 from the back surface and has an opening (slit).

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

  FIG. 3A is an enlarged vertical cross-sectional view of a main part of the current sensor 1. FIG. 3B is a graph showing the relationship between the length L of the flat portion 32 and the phase difference. 3A, the left shield 3 will be described as a first shield 3A, and the right shield 3 will be described as a second shield 3B.

  The length of the flat portion 32A of the first shield 3A is LA, and the length of the flat portion 32B of the second shield 3B is LB. Further, the distance between the end face of the first shield 3A and the end face of the second shield 3B is W. In the present embodiment, LA = LB. The optimum state of the phase difference can be found by changing the length L (LA, LB) of the flat portion 32. When an alternating current is passed, an eddy current is generated in the current path 4 and the phase of the magnetic field detected by the magnetic detection element 22 is delayed from the phase of the current flowing in the current path 4, but the length L of the flat portion 32 is adjusted. This phase delay can be eliminated.

  In the graph shown in FIG. 3B, the phase difference is taken in the vertical direction, the length L of the flat portion 32 is taken in the horizontal direction, and the measurement result of the change in the central magnetic field phase by the length L (see the curve graph) is shown. It is a graph. The point where there is no phase difference delay is 0 ° (the response of the magnetic detection element 22 is good), the length L of the flat portion 32 at the intersection of the curve and the straight line with the phase difference of 0 ° is the optimum value, and the maximum value of the curve The length L of the flat portion 32 in FIG. From this graph, it is understood that it is appropriate (possible range) to set the length L of the flat portion 32 within the range from the optimum value to MAX. Moreover, it can be said from the graph that there is a strong correlation between the length L of the flat portion 32 and the response improvement effect. Therefore, if the length L is adjusted based on the frequency to be used and the maximum peak current, it is possible to perform an optimum phase control design.

  4A and 4B are explanatory diagrams showing how the magnetic field is changed by the shield 3 of the present invention.

  When a sinusoidal alternating current A travels in the direction of the arrow (from the front to the back of the drawing) in the current path 4, a magnetic field M having a strength corresponding to the rate of change of the current with respect to time is generated, and a vortex around the magnetic field M is generated. A current Q is generated. When the current A is alternating current, the magnetic field M is an alternating magnetic field that repeatedly changes in magnitude and direction with time. As shown in FIG. 4A, if there is no shield 3 around the current path 4, a residual magnetic field is generated, which causes a delay in detection of the magnetic detection element 22. On the other hand, when the shields 3A and 3B are provided around the current path 4 (see FIG. 4B) and the flat portions 32A and 32B of the shields 3A and 3B extend in the center direction of the current path 4, the flat portions 32A A magnetic field N is generated from the end portion 33A to the end portion 33B of the other flat portion 32B. When this magnetic field N crosses the current path 4, the magnetic field cancels out with the magnetic field M generated in the current path 4. As a result, the residual magnetic field can be suppressed and the generation of eddy current can be prevented. In addition, the current density distribution in the cross section of the current path 4 can be made uniform, and the delay in detection response of the magnetic detection element 22 is eliminated. Although only one direction has been described, in the case of alternating current, the direction of the magnetic field alternates in a short time.

  FIG. 5A is a comparative graph of 90% -90% response time (μs) when the current fluctuates at a slew rate of 100 A / μs according to the configuration of the prior art and the embodiment of the present invention. As shown in FIG. 5B, the 90% -90% response time is a voltage value (output voltage 90%) that is 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. 5A, the response time of 60 μs of the prior art is improved 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. 6 is a graph showing the performance in terms of current value and magnetic flux density.

  In the graph of FIG. 6, the vertical axis represents magnetic flux density (mT) and the horizontal axis represents current (A). As understood from this graph, magnetic saturation is likely to occur when the current (A) increases (see the curve). However, in the present invention, the occurrence of magnetic saturation is suppressed even when a high-frequency large current flows, and linearity is achieved. It is possible to extend a section (linear section) in which is maintained. The section in which linearity is recognized between the magnetic flux density (mT) and the current (A) in FIG. 6 depends on the length L of the flat portion 32 described with reference to FIG. As the length of the flat portion 32 approaches MAX, the extended linear section is reduced to zero. Thus, also in FIG. 6, it turns out that the effect of the shield structure of this invention is remarkable.

  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 4 Current path 21 Board | substrate 22 Magnetic detection element 31 Fitting part 32 Flat part 33 End part

Claims (2)

A current sensor for detecting a current flowing through a flat current path,
A substrate, a magnetic detection element mounted on the substrate and disposed near the plate surface of the current path, and a pair of surrounding the magnetic detection element and the current path so as to circulate around an axis of the current path A shield plate,
The pair of shield plates is
An element-side slit located in a direction away from the current path in the orthogonal direction perpendicular to the plate surface of the current path, and a position farther from the magnetic detection element than the current path in the orthogonal direction. Are separated from each other by current path side slits at positions away from each other,
The pair of shield plates is
A pair of flat fitting portions extending in the orthogonal direction, and extending from the end on the current path side slit side of each of the pair of fitting portions toward each other in a direction along the plate surface of the current path. A pair of flat portions, and the pair of flat portions are disposed so as to overlap with a part of the current path in the orthogonal direction. A road-side slit is defined, and the element-side slit is defined by an end of the pair of fitting portions on the element-side slit side,
The entire substrate is
In the orthogonal direction, the pair of fitting portions are positioned within the extending range , and in the direction along the plate surface of the current path, are positioned within the range between the pair of fitting portions. ,
Current sensor. The pair of shield plates is
The length in the extending direction of the flat portion is the same,
The current sensor according to claim 1.

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