JP2021135186A - Current sensor - Google Patents

Abstract

To provide a current sensor including a magnetic substance core composed of a magnetic substance material, capable of inhibiting decrease in current measuring accuracy due to residual magnetization of the magnetic substance core.SOLUTION: A current sensor 1 is provided which comprises: a conductor 10 which extends in a predetermined direction and which current flows in the predetermined direction; a detector element 11 detecting a magnetic field generated by the current flowing through the conductor 10; and a magnetic substance core 12 including two plate-like magnetic substances 121, 122 holding the conductor 10 and the detector element 11 therebetween from both sides of the detector element in a magneto-sensitive direction and collecting the magnetic field.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current sensor.

Conventionally, a conductive portion that stretches in a predetermined direction and allows a current to flow in that direction, a detection portion that detects a magnetic field generated by the current flowing through the conductive portion, and a shield made of a conductive portion and a ferromagnetic material that surrounds the detection portion. A current sensor is known (see, for example, Patent Document 1).

The shield in the current sensor described in Patent Document 1 has a bottom portion facing the conductive portion and two side portions extending from the bottom portion with the conductive portion and the detection portion sandwiched between them, and the conductive portion and the detection portion are external to the shield. The magnetic field input from is shielded to reduce the influence of disturbance on the detection unit.

Japanese Unexamined Patent Publication No. 2017-181415

However, in a current sensor as described in Patent Document 1, although the influence of an external magnetic field can be suppressed by the shield, residual magnetization occurs when the magnetic field generated by the current flowing through the conductive portion is applied to the shield. Therefore, there is a problem that the measurement accuracy of the current is lowered due to the influence of the magnetic field generated by the residual magnetization of the shield.

Therefore, an object of the present invention is to provide a current sensor including a magnetic core made of a magnetic material, which can suppress a decrease in current measurement accuracy due to residual magnetization of the magnetic core. be.

An object of the present invention is to solve the above-mentioned problems, the present invention includes a conductor that is stretched in a predetermined direction and a current flows in the predetermined direction, a detection element that detects a magnetic field generated by a current flowing through the conductor, and the above-mentioned. Provided is a current sensor including a conductor and a magnetic material core having two plate-shaped magnetic materials sandwiching the detection element from both sides in the magnetic sensing direction of the detection element and collecting the magnetic field. ..

According to the present invention, it is possible to provide a current sensor including a magnetic core made of a magnetic material, which can suppress a decrease in current measurement accuracy due to residual magnetization of the magnetic core.

FIG. 1 is a perspective view of a current sensor according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of the current sensor cut along the cutting line AA shown in FIG. FIG. 3 is a view obtained by adding a vector of the magnetic flux density of the magnetic field generated by the residual magnetization of the magnetic core to the vertical cross-sectional view of the current sensor shown in FIG. FIG. 4 shows, as a comparative example, a vertical cross-sectional view of a current sensor having a magnetic core made of one curved plate-shaped magnetic material, and a vector of the magnetic flux density of the magnetic field generated by the residual magnetization of the magnetic core is added. It is a figure. FIG. 5 is a graph showing an example of the magnetic flux density distribution of the magnetic field generated by the residual magnetization of the magnetic core in the current sensor according to the present embodiment shown in FIG. 3 and the current sensor according to the comparative example shown in FIG. Is. 6 (a) and 6 (b) are vertical cross-sectional views of a modified example of the current sensor according to the embodiment of the present invention. FIG. 7 is a vertical cross-sectional view of a modified example of the current sensor according to the embodiment of the present invention.

[Embodiment]
FIG. 1 is a perspective view of the current sensor 1 according to the embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of the current sensor 1 cut along the cutting line AA shown in FIG.

The current sensor 1 has a bus bar 10 having a current measuring unit 101 that extends in a predetermined direction X and a current flows in the predetermined direction X, a detection element 11 that detects a magnetic field generated by a current flowing through the current measuring unit 101, and a bus bar. It has two plate-shaped magnetic bodies 121 and 122 that sandwich the current measuring unit 101 of 10 and the detection element 11 from both sides, and includes a magnetic body core 12 that collects the above magnetic field.

The current sensor 1 can measure the magnitude of the current flowing through the bus bar 10 based on the magnitude of the magnetic field generated by the current flowing through the current measuring unit 101 detected by the detection element 11.

The bus bar 10 is, for example, a flat plate-shaped wiring member connected to terminals of an inverter device, an electric motor, a battery cell, and the like, and as shown in FIG. 2, the shape of the cross section of the current measuring unit 101 perpendicular to the direction X. Is rectangular.

Instead of the bus bar 10, a conductor other than the bus bar 10 in which a current flows in a predetermined direction X may be used. In this case, the shape of the cross section of the current measuring unit perpendicular to the direction X may be rectangular or another shape like the current measuring unit 101 of the bus bar 10.

As described above, the detection element 11 is an element that detects the magnetic field generated by the current flowing through the current measuring unit 101. Therefore, the detection element 11 is installed at a position where a magnetic field formed around the current measuring unit 101 due to the current flowing through the current measuring unit 101 passes, that is, a position facing the current measuring unit 101. The detection element 11 has a magnetically sensitive portion that senses a magnetic field, and the magnetically sensitive direction of the magnetically sensitive portion is a horizontal direction (a direction parallel to the Z direction shown in FIGS. 1 and 2). When the current measuring unit 101 has a flat plate shape as shown in FIGS. 1 and 2, the width direction of the current measuring unit 101 is parallel to the Z direction, so that the magnetic sensing direction (of the magnetic sensing unit) of the detection element 11 Is parallel to the width direction of the current measuring unit 101.

The detection element 11 has a magnetically sensitive portion composed of, for example, a magnetoresistive effect element such as a GMR element, and the current sensor 1 outputs according to the magnitude of the magnetic field applied to the magnetically sensitive portion of the detection element 11. The value of the current flowing through the bus bar 10 is acquired based on the voltage to be applied.

The magnetic core 12 has a function of collecting a magnetic field generated by a current flowing through the current measuring unit 101 to increase the magnetic flux density passing through the detection element 11. The magnetic core 12 is made of a soft magnetic material such as a silicon steel plate.

As shown in FIGS. 1 and 2, the magnetic body 121 and the magnetic body 122 sandwich the current measuring unit 101 of the bus bar 10 and the detection element 11 from both sides of the detection element 11 parallel to the Z direction in the magnetic sensing direction.

The magnetic core 12 is, for example, a curved plate-shaped magnetic material separated into two magnetic materials 121 and 122 by a slit 123. In this case, the magnetic body 121 and the magnetic body 122 are formed by dividing one curved plate-shaped magnetic body, and usually, the end face 121a of the magnetic body 121 and the end face 122a of the magnetic body 122 constituting the slit 123 are formed. Face each other.

The magnetic core 12 shown in FIGS. 1 and 2 is made of, for example, a curved plate-shaped magnetic material having a U-shaped cross section, which is composed of a plate-shaped bottom portion and plate-shaped side portions continuous on both sides thereof. It is formed by dividing the bottom. Since the vicinity of the lower end portion of the magnetic body 121 and the magnetic body 122 shown in FIGS. 1 and 2 is a part of the bottom portion of one curved plate-shaped magnetic body, it is curved so as to face each other. doing. Here, the curved portions of the magnetic body 121 and the magnetic body 122 are referred to as a curved portion 121c and a curved portion 122c, respectively.

The smaller the inclination angle (closer to horizontal) of the curved portions 121c and 122c of the magnetic material 121 and the magnetic material 122, the easier it is for magnetic saturation, and the maximum value of the current that can be detected by the current sensor 1 is increased. It becomes smaller.

FIG. 3 is a view obtained by adding a vector of the magnetic flux density of the magnetic field generated by the residual magnetization of the magnetic core 12 to the vertical cross-sectional view of the current sensor 1 shown in FIG. FIG. 3 shows a state in which a current is not passed through the bus bar 10 after a current is passed through the bus bar 10 and a magnetic field is applied to the magnetic core 12. That is, FIG. 3 does not show the magnetic field due to the current flowing through the bus bar 10.

In the current sensor 1, the magnetic field generated by the residual magnetization between the vicinity of the upper end surface 121b of the magnetic material 121 and the vicinity of the upper end surface 122b of the magnetic material 122 is directed from the magnetic material 122 to the magnetic material 121 and is on the lower side of the magnetic material 121. The magnetic field generated by the residual magnetization between the vicinity of the end face 121a and the vicinity of the lower end face 122a of the magnetic body 122 is directed from the magnetic body 121 to the magnetic body 122 (the direction of these magnetic fields when the direction of the current flowing through the bus bar 10 is reversed). Is the opposite).

Therefore, in the space between the magnetic material 121 and the magnetic material 122, the magnetic field from the magnetic material 121 to the magnetic material 122 generated by the residual magnetization of the magnetic material core 12 and the magnetic material 122 generated by the residual magnetizing of the magnetic material core 12 to the magnetic material. The magnetic fields toward 121 cancel each other out, and the magnitude of the magnetic field is reduced. As a result, it is possible to suppress a decrease in current measurement accuracy due to the residual magnetization of the magnetic core 12.

In order to more effectively suppress the decrease in current measurement accuracy due to the residual magnetization of the magnetic core 12, the magnetic field generated by the residual magnetization of the magnetic core 12 in the space between the magnetic material 121 and the magnetic material 122 It is preferable to install the detection element 11 so as to overlap the point where the size (absolute value of the intensity) is minimized (hereinafter referred to as the point P).

Further, in the space between the magnetic material 121 and the magnetic material 122, a magnetic field from the magnetic material 121 to the magnetic material 122 generated by the residual magnetization of the magnetic material core 12 and a magnetic material 122 to the magnetic material generated by the residual magnetizing of the magnetic material core 12 There is a point where the magnetic fields toward 121 cancel each other out and the magnitude of the magnetic field generated by the residual magnetization of the magnetic core 12 becomes zero, that is, the magnitude of the magnetic field generated by the residual magnetization of the magnetic core 12 at the point P It is preferably zero.

When the magnitude of the magnetic field generated by the residual magnetization of the magnetic core 12 at the point P is zero, the detection element 11 is installed so as to overlap the point P, so that the measurement accuracy of the current due to the residual magnetization of the magnetic core 12 can be improved. The drop can be minimized.

For example, when the magnetic body 121 and the magnetic body 122 are in a plane symmetric relationship and the current measuring unit 101 has plane symmetry with respect to the plane of symmetry, the magnitude of the magnetic field generated by the residual magnetization of the magnetic body core 12 on the plane of symmetry. There can be a point P where is zero.

In the example shown in FIG. 3, the magnetic body 121 and the magnetic body 122 have a plane symmetry relationship with respect to the plane of symmetry π, and the current measuring unit 101 has a plane symmetry with respect to the plane of symmetry π. There is a point P on the plane of symmetry π where the magnitude of the magnetic field generated by the magnetism becomes zero. The dotted arrow in FIG. 3 roughly indicates the magnetic field from the magnetic body 121 to the magnetic body 122 and the magnetic field from the magnetic body 122 to the magnetic body 121 that pass through the vicinity of the point P and cancel each other out in the vicinity of the point P. .. Since the detection element 11 is installed so as to overlap the point P, the decrease in current measurement accuracy due to the residual magnetization of the magnetic core 12 is minimized.

FIG. 4 shows a vertical cross-sectional view of a current sensor 5 having a magnetic core 52 made of one curved plate-shaped magnetic material as a comparative example, showing the magnetic flux density of the magnetic field generated by the residual magnetization of the magnetic core 52. It is the figure which added the vector. The magnetic core 52 has a shape corresponding to the shape of the magnetic core 12 that does not include the slit 123, and has a plate-shaped bottom portion 523 facing the lower surface of the current measuring unit 101 and plate-shaped sides continuous on both sides thereof. It is composed of parts 521 and 522.

As shown in FIG. 4, in the current sensor 5, in the entire region of the space between the side portion 521 and the side portion 522 of the magnetic material core 52, the magnetic field generated by the residual magnetization of the magnetic material core 52 is from the side portion 522. Head to the side 521. Therefore, the magnetic fields generated by the remanent magnetization hardly cancel each other out and decrease (at least the vectors in the horizontal direction (direction parallel to the Z direction in FIGS. 1 to 3) cancel each other out and decrease), and the current sensor. In No. 5, the detection element 11 is greatly affected by the magnetic field generated by the residual magnetization as compared with the current sensor 1.

FIG. 5 shows an example of the magnetic flux density distribution of the magnetic field generated by the residual magnetization of the magnetic core in the current sensor 1 according to the present embodiment shown in FIG. 3 and the current sensor 5 according to the comparative example shown in FIG. It is a graph which shows. The vertical axis of FIG. 5 represents the magnetic flux density on the surface π passing through the center of the current measuring unit 101 in the width direction (direction parallel to the Z direction), and the horizontal axis represents the surface of the current measuring unit 101 (upper side of FIG. 3). Represents the distance from the surface). The magnetic flux densities of the current sensors 1 and 5 in FIG. 5 are standardized with the magnetic flux density on the surface of the bus bar 10 of the current sensor 5 as 1.

FIG. 5 shows that the magnetic field generated by the residual magnetization of the magnetic core 12 of the current sensor 1 is much smaller than the magnetic field generated by the residual magnetization of the magnetic core 52 of the current sensor 5. Further, according to FIG. 5, the point P at which the magnetic flux density of the magnetic field generated by the residual magnetization of the magnetic core 12 of the current sensor 1 becomes zero is indicated by an arrow in FIG. 5 (from the surface of the current measuring unit 101). The distance is about 0.6 mm).

In the current sensor 1, the width of the slit 123 (distance between the end face 121a and the end face 122a) is adjusted to change the distribution of the magnetic field between the end face 121a and the end face 122a, which is generated by the residual magnetization of the magnetic core 12. The position in the height direction (direction parallel to the Y direction in FIGS. 1 to 3) of the point P where the magnitude of the magnetic field is minimized can be changed. Specifically, the position of the point P goes down when the width of the slit 123 is narrowed, and goes up when the width of the slit 123 is widened.

By installing the detection element 11 near the center in the space between the magnetic material 122 and the magnetic material 121, the influence of the magnetic field outside the magnetic material core 12 can be further reduced. Further, by installing the detection element 11 at a certain distance from the current measuring unit 101, it is possible to suppress the influence of heat received from the current measuring unit 101 that generates heat due to the flow of the current. The position of the point P can be set by adjusting the width of the slit 123 according to the installation position of the detection element 11 set based on these circumstances.

(Modification example 1)
The magnetic core 12 has a magnetic body 121 and a magnetic body 122 that sandwich the current measuring unit 101 and the detection element 11 from both sides, and a magnetic field from the magnetic body 121 to the magnetic body 122 generated by the residual magnetization of the magnetic body core 12. The shape is particularly good if the magnetic fields from the magnetic body 122 to the magnetic body 121 generated by the residual magnetization of the magnetic body core 12 cancel each other out and the magnetic field in the space between the magnetic body 121 and the magnetic body 122 is reduced. Not limited.

FIG. 6A is a vertical cross-sectional view of the current sensor 2 which is a modified example of the current sensor 1. The current sensor 2 has a magnetic core 22 having a shape different from that of the magnetic core 12 of the current sensor 1. The magnetic core 22 is, for example, a curved plate-shaped magnetic body separated into two magnetic bodies 221 and 222 by a slit 223, and the end faces 221a and the magnetic body 222 of the magnetic body 221 constituting the slit 223. The end faces 222a face each other.

The magnetic bodies 221 and 222 constituting the magnetic body core 22 are the magnetic bodies 121 and 122 constituting the magnetic body core 12 in that the portion sandwiching the current measuring unit 101 and the detection element 11 is vertical (parallel to the Y direction). Although different, the magnitude of the magnetic field is such that the magnetic field from the magnetic material 221 to the magnetic material 222 generated by the residual magnetization of the magnetic material core 22 and the magnetic field from the magnetic material 222 to the magnetic material 221 generated by the residual magnetism of the magnetic material core 22 cancel each other out. There is an area where is reduced.

FIG. 6B is a vertical cross-sectional view of the current sensor 3, which is a modified example of the current sensor 1. The current sensor 3 also has a magnetic core 32 having a shape different from that of the magnetic core 12 of the current sensor 1. The magnetic core 32 is, for example, a curved plate-shaped magnetic body separated into two magnetic bodies 321 and 322 by a slit 323, and the end faces 321a and the magnetic body 322 of the magnetic body 321 constituting the slit 323. The end faces 322a face each other.

The magnetic bodies 321 and 322 constituting the magnetic body core 32 are different from the magnetic bodies 121 and 122 constituting the magnetic body core 12 in that their upper ends are curved so as to face each other. The magnitude of the magnetic field is reduced by canceling the magnetic field from the magnetic material 321 to the magnetic material 322 generated by the residual magnetization of the magnetic material core 32 and the magnetic field from the magnetic material 322 to the magnetic material 321 generated by the residual magnetism of the magnetic material core 32. There is an area.

In a modified example in which the shapes of the two magnetic bodies are different from those of the current sensor 1, such as the current sensors 2 and 3, the magnitude of the magnetic field generated by the residual magnetization of the magnetic body core is minimized in the YZ plane of the point P. The position may be different from the current sensor 1. Further, similarly to the current sensor 1, the position of the point P in the YZ plane changes depending on the position and shape of the slit.

(Modification 2)
In the current sensor 1, for example, the current measuring unit 101, the detecting element 11, and the magnetic core 12 are housed in a housing or sealed with a mold so that the current measuring unit 101 and the detection element 11 are magnetic with respect to the position of the current measuring unit 101. The position of the body core 12 can be fixed. At that time, since the magnetic body 121 and the magnetic body 122 of the magnetic body core 12 are separated, the magnetic body 121 and the magnetic body are compared with the conventional magnetic body core composed of one component such as the magnetic body core 52. The relative position of 122 may be easily displaced.

FIG. 7 is a vertical cross-sectional view of the current sensor 4, which is a modified example of the current sensor 1. In the current sensor 4, the magnetic body 121 and the magnetic body 122 of the magnetic body core 12 are held by an insulating holding member 40 made of resin or the like so that their relative positions are fixed. Since the magnetic body 121 and the magnetic body 122 are fixed by the holding member 40, the relative positions of the magnetic body 121 and the magnetic body 122 are displaced when the magnetic body core 12 is housed in the housing or sealed with a mold. Can be prevented.

(Effect of embodiment)
According to the current sensor according to the embodiment described above, the magnitude of the magnetic field inside the magnetic core is reduced by forming the magnetic core with two magnetic materials sandwiching the bus bar from both sides, and the magnetic core. It is possible to suppress a decrease in current measurement accuracy due to the residual magnetization of.

(Summary of embodiments)
Next, the technical concept grasped from the above-described embodiment will be described with reference to the reference numerals and the like in the embodiment. However, the respective reference numerals and the like in the following description are not limited to the members and the like in which the components in the claims are specifically shown in the embodiment.

[1] A conductor (10) that is stretched in a predetermined direction and a current flows in the predetermined direction, a detection element (11) that detects a magnetic field generated by a current flowing through the conductor (10), and the conductor. It has two plate-shaped magnetic bodies (121, 122, 222, 222, 321 and 222) that sandwich (10) and the detection element (11) from both sides in the magnetic sensing direction of the detection element (11). Current sensors (1-4) including a magnetic core (12, 22, 32) that collects the magnetic field.

[2] Absolute magnetic field strength generated by the residual magnetization of the magnetic core (12, 22, 32) in the space between the two magnetic materials (121, 122, 221 222, 321 and 222). The current sensor (1 to 4) according to the above [1], wherein the detection element is installed so as to overlap the point where the value becomes the minimum.

[3] In the space between the two magnetic materials (121, 122, 221 222, 321 and 222), the magnitude of the magnetic field generated by the residual magnetization of the magnetic material core (12, 22, 32) is zero. The current sensor (1 to 4) according to the above [2], wherein there is a point where the current sensor becomes.

[4] The magnetic core (12, 22, 32) is separated into the two magnetic bodies (121, 122, 221, 222, 321 and 322) by a slit (123, 223, 323), and is curved. The current sensor (1 to 4) according to any one of the above [1] to [3], which is a plate-shaped magnetic material.

[5] The end faces (121a, 122a, 222a, 222a, 321a, 322a) of the two magnetic materials (121, 122, 221, 222, 321 and 222) constituting the slit (123, 223, 323) are The current sensors (1-4) according to the above [4], which face each other.

[6] The conductor (10) is a bus bar, and the two magnetic materials (121, 122, 222, 222, 321 and 222) sandwich the conductor (10) from both sides in the width direction. The current sensor (1 to 4) according to any one of [1] to [5].

[7] The two magnetic materials (121, 122, 221 222, 321 and 222) are held by an insulating holding member (14) so that their relative positions are fixed, as described in [1]. ] To [6], the current sensor (1 to 4) according to any one of the items.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented within a range that does not deviate from the gist of the invention. In addition, the components of the above-described embodiment can be arbitrarily combined within a range that does not deviate from the gist of the invention.

Moreover, the embodiment described above does not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

1, 2, 3, 4 ... Current sensor 10 ... Bus bar 101 ... Current measuring unit 11 ... Detection elements 12, 22, 32 ... Magnetic cores 121, 122, 222, 222, 321 and 322 ... Magnetic materials 121a, 122a, 221a , 222a, 321a, 322a ... End face 123, 223, 323 ... Slit

Claims (7)

A conductor that stretches in a predetermined direction and allows an electric current to flow in the predetermined direction,
A detection element that detects the magnetic field generated by the current flowing through the conductor, and
A magnetic core that has two plate-shaped magnetic bodies that sandwich the conductor and the detection element from both sides in the magnetic sensing direction of the detection element and collects the magnetic field.
With, current sensor. The detection element was installed so as to overlap the point where the absolute value of the magnetic field strength generated by the residual magnetization of the magnetic material core is minimized in the space between the two magnetic materials.
The current sensor according to claim 1. In the space between the two magnetic materials, there is a point where the magnitude of the magnetic field generated by the residual magnetization of the magnetic material core becomes zero.
The current sensor according to claim 2. The magnetic core is a curved plate-shaped magnetic material separated into the two magnetic materials by a slit.
The current sensor according to any one of claims 1 to 3. The end faces of the two magnetic materials constituting the slit face each other.
The current sensor according to claim 4. The conductor is a bus bar,
The two magnetic materials sandwich the conductor from both sides in the width direction.
The current sensor according to any one of claims 1 to 5. The two magnetic materials were held by an insulating holding member so that their relative positions were fixed.
The current sensor according to any one of claims 1 to 6.

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