JP2012145387A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor having so high versatility as to be able to be commonly used even if a device to which the current sensor is applied is changed.SOLUTION: A current sensor comprises a detector 24 having a magnetic detection part 23 built-in and a holder part 25 having a half-square tubular holding part 27. The detector 24 is attached on a top face 27a of the holding part 27. A current line 22 where current to be measured flows is housed in a groove part constituted by an underside 27b of the holding part 27 where a convex contact part 28 contacting with the current line 22 is provided and side faces 27c and 27d adjacent to the top face 27a.

Description

  The present invention relates to a current sensor that detects a current to be measured by a magnetic field generated around a current line through which the current to be measured flows.

  In recent years, there has been a demand for a current sensor for accurately measuring large currents on the order of several tens of A to several hundreds of A such as charge / discharge currents of batteries of hybrid cars, EV cars, etc., and drive inrush currents of electric motors. . FIG. 6 is a perspective view of a current sensor using a magnetoresistive element as a magnetic field detecting element. In FIG. 6, the current sensor includes a case 4 that includes a magnetoresistive element 1, a permanent magnet 2 that applies a bias magnetic field Hb to the magnetoresistive element 1, and a conductor 3 that conducts a current i. In the current sensor configured as described above, the magnitude of the current flowing through the conductor 3 is detected from the resistance change generated when the detection magnetic field H generated when the current i flows through the conductor 3 acts on the magnetoresistive element 1. It is. For example, Patent Document 1 is known as prior art document information relating to the invention of this application.

Japanese Patent Laid-Open No. 1-292981

  In the current sensor shown in FIG. 6, even when the magnetic field acting on the magnetoresistive element 1 is small, a large resistance change occurs in the magnetoresistive element 1 so that highly sensitive current measurement is possible. However, since the magnetic field H acting on the magnetoresistive element 1 when the current i flows through the conductor 3 varies greatly depending on the distance between the magnetoresistive element 1 and the conductor 3, the magnetoresistive element 1 is fixed to the conductor 3. Since the conductor 3 needs to be held in position, and the cross-sectional shape and measurement current range of the conductor 3 are diverse, the case 4 that accommodates the magnetoresistive element 1 and the conductor 3 is designed and manufactured for each set to which the current sensor is applied. I had to. As a result, there is a problem that the manufacturing cost increases and the development period is prolonged.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a highly versatile current sensor that can be used in common even if a device to which the current sensor is applied changes.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, there is provided a detection unit including a magnetoresistor and including a magnetic detection unit for detecting a magnetic field generated by a current flowing in a current line, and the detection unit on the first surface. A convex abutting portion that abuts the current line on the second surface side facing the first surface, and has third and fourth surfaces adjacent to the second surface. And a holder portion for storing the current line in a groove portion constituted by the second, third, and fourth surfaces. According to this configuration, the current line to which the current sensor is applied is provided. By changing only the holder part according to the shape, the magnetoresistive element can be held at a fixed position with respect to the current line, so that various sets of currents can be generated while using the same detection part. It has the effect that it can be measured. In addition, since the current line and the holder part are in contact with each other at the convex contact part provided on the second surface of the holder part, the current line and the holder part are compared with the case where the current line and the holder part are in contact with each other. This also has the effect that the possibility that the distance between the magnetoresistive element and the current line fluctuates due to the presence of foreign matter between the parts can be greatly reduced.

  In the invention according to claim 2 of the present invention, in particular, the protrusion provided on the detection part is inserted and fixed in a through-hole provided from the first surface to the second surface of the holder part, The tip of the projection protruding from the second surface of the holder is a convex contact that contacts the current line. According to this configuration, the tip of the projection provided on the detection unit is directly In order to make contact with the current line, the distance between the magnetoresistive element and the current line can be accurately held at a certain position, and this has the effect of enabling high-precision current measurement. is there.

  As described above, the present invention includes a detection unit that includes a magnetoresistor and includes a magnetic detection unit that detects a magnetic field generated by a current flowing through a current line, and holds the detection unit on the first surface, The second surface facing the first surface has a contact portion that contacts the current line, and has third and fourth surfaces adjacent to the second surface, and the second, second 3, provided with a holder part for storing the current line in the groove part constituted by the fourth surface, by changing only the holder part according to the shape of the current line to which the current sensor is applied, The magnetoresistive element can be held at a fixed position with respect to the current line, thereby providing an excellent effect that a wide variety of sets of currents can be measured while using the same detection unit. It is.

The perspective view of the current sensor in Embodiment 1 of the present invention AA line sectional view of the same current sensor Sectional drawing of the magnetic detection part in Embodiment 1 of this invention The figure which shows the simulation result which shows the change of the x direction component Bx of magnetic flux density when the observation position of magnetic flux density is displaced to + x direction and + z direction from the initial position. Sectional drawing of the current sensor in Embodiment 2 of this invention A perspective view of a conventional current sensor

(Embodiment 1)
Hereinafter, the first aspect of the present invention will be described using the first embodiment. FIG. 1 is a perspective view of a current sensor 21 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the current sensor 21 taken along line AA. This is suitable for detecting a current flowing in a current bar or the like connecting a motor.

  1 and 2, when the XYZ coordinate system is taken as shown in the figure, the current line 22 through which the current I flows in the Y-axis direction includes a magnetoresistor and is generated by the current flowing through the current line 22. A current sensor 21 including a detection unit 24 including a magnetic detection unit 23 that detects a magnetic field and a holder unit 25 is disposed.

  Here, the current line 22 is made of copper or the like having a rectangular cross section of 18 mm and 3 mm in the X-axis and Z-axis directions, respectively, and the lengths in the X-axis, Y-axis, and Z-axis directions are approximately on the XY plane. 8 mm, 8 mm, and 0.5 mm magnetic detectors 23 are arranged.

  The magnetic detection unit 23 is formed by winding a magnetoresistive element formed on an insulating substrate, a thin film magnet formed on the magnetoresistive element via an insulating layer, and a copper wire coated with insulation around the insulating substrate. And a cancel coil.

  The configuration of the magnetic detection unit 23 will be briefly described with reference to FIG. 3 is a cross-sectional view of the magnetic detection unit 23, FIG. 3A is a cross-sectional view when the magnetic detection unit 23 is cut horizontally, and FIG. 3B is a cross-sectional view of FIG. It is sectional drawing when cut by B line.

  In FIG. 3, four electrodes, that is, an application electrode 31a, a first output electrode 31b, a second output electrode 31c, and a ground electrode 31d are formed on an insulating substrate 30. A meandering magnetoresistive element 32a made of a magnetoresistor is formed between the application electrode 31a and the first output electrode 31b. Similarly, between the first output electrode 31b and the ground electrode 31d, between the application electrode 31a and the second output electrode 31c, and between the second output electrode 31c and the ground electrode 31d, a meandering magnetic field is formed. Resistive elements 32b, 32c, and 32d are formed. By making such an electrical connection, the magnetoresistive elements 32a, 32b, 32c, and 32d constitute a bridge circuit. The magnetoresistive elements 32a, 32b, 32c, and 32d are magnetoresistive thin films having a thickness of about 0.1 μm made of a ferromagnetic material such as Ni—Co. In FIG. 3, the magnetoresistive element 32a has the longitudinal direction of the meandering pattern in a 45 ° direction inclined obliquely upward to the right on the paper surface. The longitudinal direction of the meander pattern is located in a 45 ° direction inclined obliquely upward, and the angle between them is a right angle. The positional relationship between the magnetoresistive element 32c and the magnetoresistive element 32d is the same. Further, the positional relationship between the magnetoresistive element 32a and the magnetoresistive element 32c is the same. Here, the magnetosensitive directions of the magnetoresistive elements 32a, 32b, 32c and 32d are perpendicular to the longitudinal direction of each meander pattern.

The insulating layer 33 is made of a SiO ₂ thin film having a thickness of about 1 μm, and electrically insulates the thin film magnet 34 described later by covering the magnetoresistive elements 32a, 32b, 32c, and 32d.

The thin film magnet 34 is made of CoPt or the like having a thickness of about 0.6 μm, and is formed on the insulating layer 33 by vapor deposition, sputtering, or the like, and then patterned by exposure and etching to have a plurality of substantially rectangular parallelepiped shapes having a longitudinal direction. It is divided into The direction of the generated magnetic field is the direction perpendicular to the longitudinal direction of the thin-film magnet 34, that is, the left-right direction in FIG. The thin film magnet 34 is divided into a plurality of substantially rectangular parallelepipeds having a longitudinal direction in a direction forming 45 ° with respect to the longitudinal direction of the pattern of the magnetoresistive elements 32a, 32b, 32c, and 32d. This direction is also a direction that forms 45 ° with respect to the magnetosensitive direction of the magnetoresistive elements 32a, 32b, 32c, and 32d. The magnetic field generated by the thin film magnet 34 is arranged in the same direction as the current flowing through the current line 22, that is, in the direction perpendicular to the magnetic field generated by the current to be measured flowing through the current line 22. The insulating layer 35 is made of a SiO ₂ thin film and covers the thin film magnet 34.

  The cancel coil 36 is formed by winding a copper wire having an insulating coating on the surface thereof, and surrounds the insulating substrate 30, and its winding axis is perpendicular to the current I (that is, in the same direction as the magnetic field induced by the current I). It is provided to become.

  The operation of the magnetic detection unit 23 having the above configuration will be described below.

  A predetermined voltage is applied to the application electrode 31a so as to generate a constant potential difference with the ground electrode 31d.

When the current flowing through the current line 22 is 0, only the bias magnetic field H _B from the thin film magnet 34 is applied so as to form 45 ° with respect to the respective magnetosensitive directions of the magnetoresistive elements 32a, 32b, 32c, and 32d. At this time, the resistance values of the magnetoresistive elements 32a, 32b, 32c, and 32d are the same, and the potentials of the first output electrode 31b and the second output electrode 31c that are the midpoint potential of the bridge circuit are the same. The output from the current sensor will not appear.

When the current I flows through the current line 22, a magnetic field H _I due to the current _I is generated and applied to the magnetic detection unit 23. At this time, a magnetic field obtained by combining the bias magnetic field H _B and the magnetic field H _I due to the current I is applied to the magnetoresistive elements 32a, 32b, 32c, and 32d. At this time, the resistance values of the magnetoresistive element 32a and the magnetoresistive element 32b are different, and the resistance values of the magnetoresistive element 32c and the magnetoresistive element 32d are also different. For this reason, the balance of the bridge circuit is broken, and a potential difference is generated between the first output electrode 31b and the second output electrode 31c. By negatively feeding back this potential difference, a negative feedback current is caused to flow through the cancel coil 36, and a magnetic field in the direction opposite to the magnetic field caused by the current I to be measured is generated in the magnetic detection unit 23. Then, the measured current I is measured from the negative feedback current value flowing through the cancel coil 36 when the potential difference between the first output electrode 31b and the second output electrode 31c becomes zero.

  The holder portion 25 is formed by molding a high heat-resistant resin such as liquid crystal polymer or PPS, provided with flanges 26 for attachment to a vehicle body (not shown) such as a hybrid car on both sides, and a half-square cylindrical holding portion at the center portion. 27 is provided. The detection unit 24 is attached to the upper surface 27a of the holding unit 27, and the current line 22 is accommodated in a groove portion that includes a lower surface 27b facing the upper surface 27a and side surfaces 27c and 27d adjacent to the lower surface 27b. . A convex contact portion 28 that contacts the current line 22 is provided on the lower surface 27b.

  The detection unit 24 can be attached to the holding unit 27 by bonding the bottom surface of the detection unit 24 and the upper surface 27a of the holding unit 27. In the first embodiment, the bottom surface of the detection unit 24 is used. The protruding portion 24a provided on the holding portion 27 is inserted into a through hole 27e provided from the upper surface 27a to the lower surface 27b of the holding portion 27, and the protruding portion 24a and the through hole 27e are fixed using a method such as adhesion or welding. ing.

  In FIG. 2, when a current I flows through the current line 22, a magnetic field is generated around the current line 22. For example, when a current of 400 A flows through the current line 22, according to the simulation results, the x-direction component Bx of the magnetic flux density observed at a position 5 mm from the upper surface of the current line 22 on the Z axis is 8.3 mT. It becomes a magnetic field. Here, the x-direction component Bx of the magnetic flux density is a magnetic flux density component that acts on the magnetic detection elements 32a, 32b, 32c, and 32d of the magnetic detection unit 23 to cause a resistance change.

  FIG. 4 shows a simulation result of calculating how the x-direction component Bx of the magnetic flux density changes when the observation position is displaced from the above position in the + x direction and the + z direction. From this result, the x-direction component Bx of the observed magnetic flux density hardly changes even when the observation position is displaced in the x direction, whereas when the observation position is displaced in the z direction, the observed magnetic flux density The x-direction component Bx varies greatly. For example, if the variation in the observed x-direction component Bx of the magnetic flux density is to be ± 5% or less, the observation position accuracy in the z direction needs to be ± 0.3 mm or less. I understand that.

  In the current sensor 21 according to the first embodiment of the present invention, only the groove width and depth of the holder part are changed according to the shape of the current line 22 to which the current sensor 21 is applied, so that Since the distance between the magnetoresistive element and the current line 22 in particular in the z direction can be kept constant, a wide variety of sets of currents can be measured while using the same detector 24. Further, since the current line 22 and the holder part 25 are in contact with each other at the convex contact part 28 provided on the lower surface 27b of the holder part 25, compared with the case where the current line 22 and the holder part 25 are in contact with each other, The possibility that the distance between the magnetoresistive element on the magnetic detection unit 23 and the current line 22 varies due to the presence of foreign matter between the current line 22 and the holder unit 25 can be greatly reduced. In addition, since the current line 22 and the holder portion 25 are in contact with each other at a convex contact portion 28 provided on the lower surface 27 b of the holder portion 25, the thermal conductivity is reduced and a large current flows through the current line 22. It is difficult for the heat generated in to be transmitted to the detection unit 24. Thereby, the temperature rise of the magnetic detection part 23 can be suppressed, and deterioration of the current measurement accuracy due to temperature can also be prevented. In the current sensor 21 according to the first embodiment of the present invention, the convex contact portion 28 is provided only on the lower surface 27b of the holder portion 25, but also on the bottom surface of the detection portion 24 or the upper surface 27a of the holder portion 25. A similar contact portion is provided, and the upper surface 27a of the holder portion 25 and the detection portion 24 are brought into contact with each other at this contact portion, so that foreign matter is interposed between the detection portion 24 and the holder portion 25 and the magnetic detection portion 23 The possibility that the distance between the magnetoresistive element and the current line 22 fluctuates can be further reduced, and the temperature rise of the magnetic detection unit 23 can be further suppressed.

(Embodiment 2)
The second aspect of the present invention will be described below with reference to the second embodiment. FIG. 5 shows a cross-sectional view of a current sensor according to Embodiment 2 of the present invention. In the second embodiment of the present invention, components having the same configuration as the configuration of the first embodiment of the present invention described above are denoted by the same reference numerals, and the description thereof is omitted.

  5, the second embodiment of the present invention is different from the first embodiment of the present invention described above in that it is inserted into a through hole 27 e provided from the upper surface 27 a to the lower surface 27 b of the holding portion 27 of the holder portion 25. The protrusion 24a provided on the fixed detection unit 24 is provided with a convex contact portion 29 that contacts the current line 22, and the other configuration is the same as that shown in FIG. . In the current sensor configured as described above, the distance between the detection unit 24 and the current line 22 is uniquely determined by the length of the protrusion 24a provided on the bottom surface of the detection unit 24. The distance between the magnetoresistive element and the current line 22 in particular in the z direction can be kept constant, and by changing only the holder portion according to the shape of the current line 22 to which the current sensor is applied, The magnetoresistive element can be more accurately held at a fixed position with respect to the current line 22.

  The current sensor according to the present invention can hold the magnetoresistive element at a fixed position with respect to the current line by changing only the holder portion according to the shape of the current line to which the current sensor is applied. Can be used to measure a wide variety of sets of currents while using the same detector, and is particularly useful as a current sensor for detecting currents in vehicles, industrial equipment, etc. It is.

21 Current sensor 22 Current line 24 Detection unit 24a Projection unit 25 Holder unit 28, 29 Convex contact unit

Claims (2)

A detection unit including a magnetoresistor and including a magnetic detection unit configured to detect a magnetic field generated by a current flowing in a current line; and a first unit that holds the detection unit on a first surface and faces the first surface 2 has a convex contact portion that contacts the current line, and has third and fourth surfaces adjacent to the second surface, and the second, third, and fourth surfaces. A current sensor comprising: a holder portion that houses the current line in a groove portion constituted by a surface. The protrusion provided on the detection part is inserted and fixed in a through-hole provided from the first surface to the second surface of the holder part, and the protrusion of the protrusion protruded from the second surface of the holder part. The current sensor according to claim 1, wherein the tip is a convex contact portion that contacts the current line.

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