JP6747909B2 - Current sensor - Google Patents

Description

The present invention relates to a current sensor using a magnetoelectric conversion element.

In Japanese Patent No. 4861155 (Patent Document 1), a conductor in which an electric current flows and an annular shape which is arranged so as to surround an axis around the electric current flowing direction of the conductor and has a gap along the electric current flowing direction An example of a conventional current sensor having a shield plate and a magnetoelectric conversion element that detects the magnetic flux density of a magnetic field generated when a current flows through a conductor and converts the magnetic flux density into an electric signal is disclosed. In this current sensor, the magnetoelectric conversion element is arranged in the vicinity of a position where the magnetic flux density of the magnetic field generated when a current flows through the conductor is minimized between the conductor and the gap of the shield plate measured in advance. According to the configuration of this current sensor, the influence of magnetic saturation of the shield plate can be reduced, so that the current in a wide range can be measured with high accuracy, and the current in a wide range can be accurately measured without increasing the gap. It is described in Patent Document 1 that it can be measured.

Japanese Patent No. 4861155

However, the inventor has found that the current sensor having the conventional structure has a problem that the linearity of the sensor sensitivity is poor.

An object of the present invention is to provide a current sensor using a magnetoelectric conversion element, which is excellent in linearity of sensor sensitivity.

The present invention provides a conductor through which an electric current flows, a shield main body which is arranged so as to surround a virtual center line extending in the electric current flowing direction of the conductor, and has a gap extending along the electric current flowing direction, and a current flowing through the conductor. A current sensor having a magnetoelectric conversion element that detects a magnetic flux density of a magnetic field generated when flowing and converts it into an electric signal is an object of improvement. The current sensor of the present invention includes the blocking shield part that closes the gap of the shield body. The thickness dimension of the shield main body and the thickness dimension of the blocking shield portion are determined so that the linearity of the sensitivity of the current sensor is better than the linearity of the sensitivity when the blocking shield portion is not provided. The present invention is based on the finding that the linearity of the sensitivity can be improved by the inventor's test by providing the blocking shield portion having a predetermined thickness, although the clear reason is still unknown. From the test results, it can be seen that the linearity of the sensitivity is changed (the linearity may be poor or the linearity may be improved) by changing the thickness of the shield body and the thickness of the blocking shield. understood. Therefore, according to the present invention, by appropriately changing these thicknesses, a current sensor having better linearity of sensitivity than before is provided.

More specifically, the thickness dimension of the shield main body and the thickness dimension of the closed shield portion are determined so that the linearity of the sensitivity of the current sensor in the measurement range of 0 to 100 A is within ±1%. It is assumed that the linearity is within the range of ±1% when the shield body is made of PC permalloy or ferrite and the linearity is ±2% when the blocking shield is not provided. This is because the linearity is higher than that in this case because it falls within the range.

The present invention is based on the finding that the linearity of the sensitivity can be improved by the inventor's test by providing the blocking shield portion having a predetermined thickness, although the clear reason is still unknown. From the test results, it was found that the linearity of the sensitivity was changed by changing the thickness of the shield body and the thickness of the blocking shield. Therefore, according to the present invention, these thicknesses are appropriately changed to improve the linearity of the sensitivity of the current sensor in a predetermined measurement range.

As the shield body, one having a pair of side wall portions and a connecting portion that connects one end of each of the pair of side wall portions integrally formed can be used. In this case, the closing shield part is connected to the other ends of the pair of side wall parts to close the gap. The conductor is arranged on the coupling portion side, and the magnetoelectric conversion element is arranged on the gap side. This structure has the advantages that the current measurement range can be expanded and that the sensitivity linearity can be easily obtained.

As the magnetoelectric conversion element, it is preferable to use an AMR element or a GMR element whose resistance value decreases in proportion to the strength of the magnetic field generated by the magnetic flux surrounding the conductor. The AMR element or the GMR element has a wide current measuring range and is excellent in measuring a large current.

In a specific structure, it is preferable that the connecting portion is curved along the outer circumference of the conductor, and the pair of side wall portions are opposed to each other in parallel with a certain distance. In this case, when the diameter of the conductor is 10±0.4 mm or more, the thickness of the connecting portion and the pair of side wall portions is set to 1.5±0.1 mm or more and 2.0±0.1 mm or less, and the blocking shield is formed. It is preferable to set the thickness of the part to a value within the range of 0.7±0.1 mm.

It is a front view showing one embodiment of a current sensor concerning the present invention. It is a schematic perspective view which abbreviate|omits a part of structure of the current sensor of FIG. It is a figure which shows the test result of the linearity of sensitivity when changing the thickness of a block shield part and a shield main body.

Embodiments of a current sensor according to the present invention will be described below with reference to the drawings.

In each figure, the current sensor of the present embodiment detects the current flowing through the cable C that is a conductor. The conductor is the cable C in the present embodiment, but in other embodiments, other insulated electric wires, bus bars, and the like can be detected.

The current sensor includes a shield body 1, an AMR element 2 that is a magnetoelectric conversion element, and a blocking shield portion 3 that closes a gap 4 of the shield body 1. A signal processing circuit 5 having a function of driving the AMR element 2 and processing an output signal from the AMR element is arranged in a mold portion 6 made of a molding resin. The signal processing circuit 5 and the molding unit 6 are not shown in FIG.

The shield body 1 is disposed so as to surround the virtual center line extending in the current flow direction in the extending direction of the cable C, and has a gap 4 extending along the current flow direction. The shield body 1 is made of PC permalloy in order to shield the influence of a magnetic field from the outside. PC permalloy is a high-permeability material having Ni as a main component, at least one of Cu and Mo as a secondary component, and the balance being Fe. In the present embodiment, Ni is 77 to 79% and Cu is 0 to 0%. 5%, Mo 4 to 5%, Fe 13 to 15.4%, and C, Si, Mn, etc. are used. The shield body 1 is formed by bending a belt-shaped PC permalloy plate into a U shape. That is, it is provided with a pair of side wall portions 11 and 11 that are two U-shaped linear portions and a connecting portion 12 that is a U-shaped semicircular curved portion, and the pair of side wall portions 11 and 11 and one end of each of them. And a connecting portion 12 for connecting the above are integrally formed. The other ends of the pair of side wall portions 11 and 11 are open without being connected, and the opening constitutes the gap 4.

In the current sensor of the present invention, the gap 4 of the shield body 1 is closed by the closed shield portion 3. The blocking shield portion 3 is also made of PC permalloy, but is formed of a PC permalloy plate having a smaller thickness than the shield body 1. In the present embodiment, although not shown, the closing shield part 3 is mechanically connected to the pair of side wall parts 11, 11 of the shield body 1 by a mechanical connection such as a screwing, a clip, or the like, which enables magnetic connection. It is connected to the pair of side wall parts 11 and 11 by means.

The AMR element 2 detects the magnetic flux density of the magnetic field generated when a current flows through the cable C and converts it into an electric signal. In the present invention, the AMR element whose resistance value decreases in proportion to the strength of the magnetic field generated by the magnetic flux generated so as to surround the circumference of the cable C is used, but in other embodiments, a GMR element, a TMR element, etc. , Other magnetoelectric conversion elements can also be used. The AMR element has a wide current measuring range and is excellent in measuring a large current.

The AMR element 2 is arranged inside the shield body 1 at a distance from the cable C in the radial direction of the cable C. It should be noted that the AMR element does not have to be arranged at the position as described in Patent Document 1, that is, in the vicinity of the position where the magnetic flux density of the magnetic field generated when the current flows in the cable C is minimum. In the present embodiment, since the blocking shield portion 3 is also provided, the AMR element 2 is arranged at a position away from the position where the magnetic flux density of the magnetic field generated when a current flows through the cable C is minimum.

The U-shaped connecting portion 12 of the shield body 1 is curved so as to follow the outer circumference of the cable C, and the pair of side wall portions 11 and 11 face each other in parallel with a constant space. As long as the shield body 1 can sufficiently shield the magnetoelectric conversion element (AMR element 2) from the influence of a magnetic field from the outside and can provide a gap extending along the current flow direction of the cable C, It may be C-shaped or U-shaped.

When the cable C is arranged on the coupling portion side of the shield body 1 and the AMR element 2 is arranged on the gap 4 side, the current measurement range can be expanded, and moreover the sensitivity linearity can be easily obtained. There are advantages.

In the current sensor of the present embodiment, the thickness dimension of the shield main body 1 and the thickness dimension of the blocking shield portion 3 are determined so that the linearity of the sensitivity of the current sensor in the measurement range of 0 to 100 A is within ±1%. To be

Although the clear reason is not yet clear, the present embodiment is based on the knowledge obtained by the inventor's test that the linearity of sensitivity can be improved by providing a blocking shield portion having a predetermined thickness. From the test results, it was found that the linearity of the sensitivity was changed by changing the thickness dimension of the shield body 1 and the thickness dimension of the blocking shield portion 3. Therefore, in the current sensor of the present embodiment, it is possible to obtain a current sensor in which the linearity of the sensitivity of the current sensor in the measurement range of 0 to 100 A is within ±1% by appropriately changing these thicknesses. ..

FIG. 3 shows an example of the test results. In this test, in the basic configuration shown in FIG. 1, the diameter of the cable C is set to 10 mm, the thickness of the blocking shield part 3 is changed from 0 (no blocking shield part is provided) to 0.2 mm, 0.5 mm, 0.7 mm and 1 The results show that the linearity of the current detection sensitivity was tested with the thickness of the shield body 1 set to 0.0 mm, the thickness of the shield body 1 set to 1 mm, 1.5 mm and 2.0 mm. The variation in the diameter of the cable C was ±0.4 mm, and the variation in the thickness of the blocking shield portion 3 and the thickness of the shield body 1 was ±0.1 mm. In addition, for example, the display of "+0.1/-0.2" in each test data of FIG. 3 means the value of the output linearity. From this test result, in the present embodiment, the diameter dimension of the cable C is 10±0.4 mm or more, and in that case, the thickness t1 of the connecting portion 12 of the shield body 1 and the pair of side wall portions 11 and 11 is calculated. By setting the thickness t3 of the blocking shield part 3 to a value in the range of 0.7±0.1 mm, the current in the measurement range of 0 to 100 A is set to 1.5±0.1 mm or more and 2.0±0.1 mm or less. It was confirmed that the linearity of the sensitivity of the sensor can realize a current sensor within the range of ±1%.

According to the current sensor of the present embodiment, the change in the value of the signal output from the AMR element 2 with respect to the change in the current flowing through the cable C is in a substantially proportional relationship, and exhibits linearity within a range of ±1%. Therefore, the current sensor of the present embodiment is very useful when it is necessary to continuously and accurately detect changes in the current flowing through the conductor, such as an ammeter.

Although the shield body is made of PC permalloy in the above embodiment, it is needless to say that it may be made of ferrite having the same performance. Further, in the above-described embodiment, the AMR element is used as the magnetoelectric conversion element, but it goes without saying that other magnetoelectric conversion elements such as a GMR element can be used.

According to the present invention, it is possible to obtain a current sensor using a magnetoelectric conversion element, which is excellent in linearity of sensor sensitivity.

1 Shield Main Body 2 AMR Element 3 Blocking Shield Section 4 Gap 5 Signal Processing Circuit 6 Mold Section 11 Side Wall Section 12 Connecting Section C Cable t1 Thickness of Connecting Section and Pair of Side Wall Sections of Shield Main Body t3 Thickness of Blocking Shield Section

Claims (4)

A conductor through which an electric current flows, a shield main body that is arranged so as to surround a virtual center line of the conductor that extends in the current flowing direction, and has a gap that extends along the current flowing direction, and a current flows through the conductor. In a current sensor having a magnetoelectric conversion element that detects the magnetic flux density of the magnetic field generated when
With a blocking shield portion for closing the gap of the shield body,
The shield body is configured by integrally forming a pair of side wall portions and a connecting portion that connects one end of each of the pair of side wall portions,
The closing shield part is connected to the other ends of the pair of side wall parts to close the gap,
The conductor is arranged on the coupling portion side, the magnetoelectric conversion element is arranged on the gap side,
The shield body and the blocking shield portion are formed of PC permalloy or ferrite,
The thickness dimension of the shield body and the thickness dimension of the blocking shield portion are determined so that the linearity of the sensitivity of the current sensor is better than the linearity of the sensitivity when the blocking shield portion is not provided. Characteristic current sensor. The thickness dimension of the shield main body and the thickness dimension of the closed shield portion are determined such that the linearity of the sensitivity of the current sensor in the measurement range of 0 to 100 A is within ±1%. The current sensor according to item 1. The magnetoelectric converting element, a current sensor according to claim 1 or 2 which is AMR element resistance value in proportion to the intensity of the magnetic field due to the magnetic flux generated is lowered so as to surround the conductor. The connecting portion is curved so as to follow the outer periphery of the conductor, the pair of side wall portions are opposed to each other in parallel at a constant interval,
The conductor has a diameter of 10±0.4 mm or more, the connecting portion and the pair of side wall portions have a thickness of 1.5±0.1 mm or more and 2.0±0.1 mm or less, and the blocking shield portion is 2. The current sensor according to claim 1 , wherein the thickness is in the range of 0.7±0.1 mm.

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