JP2008039734A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized easily-placeable current sensor capable of removing a uniform external magnetic field, and measuring a heavy current. <P>SOLUTION: This current sensor is constituted as follows: a sensor substrate 12 is formed, equipped with a bridge circuit wherein the first and fourth magnetoresistance effect elements and the second and third magnetoresistance effect elements are arranged specifically and connected with a connection current wire; on the other hand, at least one opening part is formed on a primary conductor 9, and each of a pair of primary conductor 9 spots facing across the opening part is used as each shunt conductor 10a, 10b respectively; the pair of shunt conductors 10a, 10b has a configuration wherein the under surface of one shunt conductor 10a and the upper surface of the other shunt conductor 10b are arranged point-symmetrically across a clearance part 11; and the sensor substrate 12 is arranged in the clearance part 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a current sensor for measuring a current flowing in a current line to be measured and a method for installing the current sensor.

As a conventional method for measuring the current flowing through the current line to be measured, a small window is opened at the central portion of the primary conductor, and a magnetic sensor is disposed at the central portion (for example, see Patent Document 1).
Further, as another shunting shape of the primary conductor, there is one in which a slit is obliquely formed in the central portion (for example, see Patent Document 2).

  As a conventional current sensor, there is one in which bridge circuits composed of four magnetoresistive elements are arranged in a mirror-symmetric manner (see, for example, Patent Document 3).

JP-A-8-136587 JP-T-2002-523751 Japanese Patent Application Laid-Open No. 8-21138

  The primary conductor of the current sensor disclosed in Patent Document 3 has a U-shaped structure, and there is an advantage that a reverse magnetic field is applied to the left and right half bridges of the bridge circuit to remove a uniform external magnetic field. It is difficult to measure a large current, and there is a problem that a U-shaped conductor is not compatible with a general linear conductor in the manufacturing process.

  For the measurement of a large current, the measurement at the shunt portion of the primary conductor disclosed in Patent Document 1 or 2 is effective. However, when a sensor board having a bridge circuit composed of four magnetoresistive elements is installed in the shunt portion, it is necessary to install the sensor substrate perpendicularly or at an angle with respect to the primary conductor. There was a problem that a convex part was generated with respect to the primary conductor.

  In addition, in the shunt structure with the slit structure disclosed in Patent Document 2, it is not necessary to install the sensor substrate vertically, but it is necessary to install the sensor substrate at an angle with respect to the primary conductor. There was a problem that a convex part was generated.

  The present invention has been made to solve the above-described problems. A current sensor that can remove a uniform external magnetic field and can measure a large current, is small and easy to install, and a method for installing the current sensor. The purpose is to obtain.

  In order to achieve the above object, a current sensor according to the present invention is arranged on an installation board as described in claim 1 and has a magnetoresistive effect in which both resistance values increase in accordance with an increase in magnetic fields in opposite directions. First and fourth magnetoresistive elements having characteristics, and second and second magnetoresistive effects which are disposed on the installation substrate and have both resistance values that decrease with an increase in the magnetic field in the opposite direction to each other. 3 and the first to fourth magnetoresistive effect elements are connected to the first half bridge by connecting the first to fourth magnetoresistive effect elements. And a connection current line constituting a bridge circuit composed of a second half-bridge circuit composed of the third and fourth magnetoresistive elements, and one divided with respect to the center line of the installation board The first half-bridge circuit is disposed in the region, and the sensor substrate on which the second half-bridge circuit is disposed in the other region, and a primary conductor having at least one opening, The provided at least two shunt conductors separated by the opening are arranged in a point-symmetric manner with the lower surface of one shunt conductor and the upper surface of the other shunt conductor having a predetermined gap, and The sensor substrate is arranged substantially in parallel.

The above invention is preferably embodied as follows.
That is, as described in claim 2, the two shunt conductors provided with one primary conductor having one opening and separated by the opening provided in the primary conductor have the same cross-sectional shape. In addition, the lower surface of one shunt conductor and the upper surface of the other shunt conductor are arranged point-symmetrically with a predetermined gap.

  Further, as described in claim 3, the two shunt conductors provided with one primary conductor having one opening and provided in the primary conductor and separated by the opening have different cross-sectional shapes, The lower surface of one shunt conductor and the upper surface of the other shunt conductor are arranged with a predetermined gap.

  According to a fourth aspect of the present invention, there is provided a configuration including at least one attachment member that fixes a part of the sensor substrate and a part of the shunt conductor in close contact with each other or in close contact through an auxiliary member. .

  Furthermore, as described in claim 5, an electric field shield cover for removing a disturbance electric field is provided above, below or both of the sensor substrate.

  According to the present invention, the first half-bridge circuit is arranged in one area separated from the center line of the installation board by four magnetoresistive elements on the installation board, and the first area is arranged in the other area. 2 half-bridge circuits are arranged, and a magnetic field in the opposite direction is applied to each half-bridge circuit, so that a uniform external magnetic field is removed and the primary conductor has a shunt structure, allowing measurement of large currents. Thus, since the sensor substrate is installed substantially parallel to the gap portion of the shunt conductor, the structure of the current sensor including the primary conductor is small, and the sensor substrate can be easily installed.

<Embodiment 1>
1 is a perspective view of a current sensor according to Embodiment 1 of the present invention, FIG. 2 is a plan view of the current sensor according to Embodiment 1 of the present invention, FIG. 3 is a side view of FIG. 2, and FIG. It is sectional drawing which shows a cross section. In these drawings, the current sensor includes a measured current detection unit 1, a sensor substrate 12 having a sensor circuit unit 15, a primary conductor 9, and an attachment member 14 for fixing them.

First, the configuration of the measured current detection unit 1 will be described.
FIG. 5 shows a plan view of the measured current detector 1, which is divided into two regions by the center line 3 of the installation substrate 2, and the magnetoresistive effect elements 4a and 4b, the magnetoresistive effect element 4c, 4d are arranged equally in line symmetry. The four magnetoresistive effect elements 4a to 4d are arranged in parallel to each other with respect to the center line 3 of the installation substrate 2, and the magnetoresistive effect elements 4a and 4d have a resistance value according to an increase in the magnetic field in the opposite direction. The magnetoresistive effect elements 4b and 4c have a magnetoresistive effect characteristic in which both resistance values decrease as the magnetic fields increase in opposite directions. Although omitted in FIG. 2, a barber pole electrode structure is formed on the magnetoresistive element.

  In addition, although the four magnetoresistive effect elements 4 are each configured by one, a plurality of magnetoresistive effect elements may be connected in a crank shape to increase the line length. Further, it may be configured symmetrically with respect to the center point on the center line 3.

  The connection current line 6 forms a bridge circuit by connecting the four magnetoresistive elements 4.

  FIG. 6 is a schematic configuration diagram showing a measured current detection unit of the current sensor according to Embodiment 1 of the present invention. In the figure, by connecting the four magnetoresistive elements 4, the magnetoresistive elements 4 a, A bridge circuit comprising a parallel connection of a half bridge circuit (second half bridge circuit) 7b comprising a series connection of a half bridge circuit (first half bridge circuit) 7a comprising a series connection of 4b and a magnetoresistive effect element 4c, 4d. 8 is constituted.

  The connection area (first connection area) 5 a is connected to the connection current line 6 between the magnetoresistive elements 4 a and 4 c of the bridge circuit 8, and the connection area (second connection area) 5 b is the magnetic field of the bridge circuit 8. The voltage is supplied to the bridge circuit 8 from the contact areas 5a and 5b, connected to the connection current line 6 between the resistance effect elements 4b and 4d. The connection area (third connection area) 5 c is connected to the connection current line 6 between the magnetoresistive elements 4 a and 4 b of the bridge circuit 8, and the connection area (fourth connection area) 5 d is the magnetic field of the bridge circuit 8. It is connected to the connection current line 6 between the resistance effect elements 4c and 4d, and the output voltage of the bridge circuit 8 is detected from the connection areas 5c and 5d.

  Although not shown in FIGS. 5 and 6, a compensating conductive line is disposed above, below, or both of the four magnetoresistive elements 4 a to 4 d on the installation substrate 2 via an insulating layer, and the bridge Based on the output voltage of the circuit 8, a current that cancels out the magnetic fields generated in the vicinity of the four magnetoresistive elements 4 may be supplied to the compensation conductive line.

Next, the overall configuration of the current sensor will be described.
The primary conductor 9 to which the current to be measured is applied has a gap portion 11 on the center line 3, and is divided into two shunt conductors 10 a and 10 b by the gap portion 11. As shown in FIG. 3, the gap 11 has a gap 11 even when the primary conductor 9 is viewed from the side. That is, when the shunt conductor 10 has a gap 11 in which the lower surface of one shunt conductor 10a and the upper surface of the other shunt conductor 10b can insert the sensor substrate 12 and the shunt conductor 10 is viewed from a cross section, Are arranged point-symmetrically.

  At this time, the measured current detection unit 1 is installed on the installation substrate mounting unit 13 provided on the center line on the sensor substrate 12 so that the measured current detection unit 1 is installed at the symmetrical center. The center lines of the primary conductor 9, the sensor substrate 12, and the measured current detection unit 1 are installed so as to coincide with each other. The installation board attaching part 13 has a concave shape so as to be located at the center of the sensor board 12 when viewed from the cross section in order to install the measured current detecting part 1 at the center of symmetry. Here, the respective cross-sections of the shunt conductors have the same shape, and the cross-sectional area is determined according to the applied current value. Moreover, such a primary conductor shape is a linear conductor, and is easily produced by punching and bending.

  On the sensor substrate 12, the sensor circuit unit 15 is arranged together with the measured current detection unit 1. The sensor circuit unit 15 supplies the voltage of the bridge circuit 8 to the connection areas 5a and 5b of the measured current detection unit 1, and outputs the output voltage of the bridge circuit 8 after appropriate amplification. Alternatively, in the configuration in which the compensation conductive line is arranged, a current that cancels the magnetic field generated in the vicinity of the four magnetoresistive effect elements 4 is applied to the compensation conductive line 16 based on the output voltage of the bridge circuit 8 as shown in FIG. It is supplied from the operational amplifier 17.

  The sensor substrate 12 and the primary conductor 9 are fixed using an attachment member 14 so as to sandwich each of them. In order to fix stably, it is desirable to fix the both sides of the sensor board 12 using two attachment members 14. The mounting member 14 is not particularly limited in material, but is preferably non-magnetic and has little deterioration with time.

Next, the operation of the current sensor will be described in the case where a compensation conductive line is provided.
When a current flows through the primary conductor 9, a magnetic field rotating clockwise is generated in the two shunt conductors 10a and 10b according to the magnitude of the current, as indicated by the broken line in FIG. Therefore, in the measured current detection unit 1, for example, in FIG. 5, a magnetic field is applied to the magnetoresistive effect elements 4a and 4b in the direction to the left of the center line 3, and the magnetoresistive effect elements 4c and 4d have a center. A magnetic field is applied to the right side of the drawing from the line 3. The magnetoresistive elements 4a and 4d both have a magnetoresistive effect characteristic in which the resistance value increases as the magnetic field increases and the resistance value decreases as the magnetic field decreases, and the magnetoresistive element 4b. On the other hand, 4c is configured to have a magnetoresistive effect characteristic in which the resistance value decreases as the magnetic field increases and the resistance value increases as the magnetic field decreases.

  Therefore, as the current flowing through the primary conductor 9 increases, the resistance values of the magnetoresistive elements 4a and 4d increase, the resistance values of the magnetoresistive elements 4b and 4c decrease, and the current flowing through the primary conductor 9 increases. As the resistance decreases, the resistance values of the magnetoresistive elements 4a and 4d decrease, and the resistance values of the magnetoresistive elements 4b and 4c increase.

  In this way, the balance of the bridge circuit 8 is lost in accordance with the magnitude of the current flowing through the primary conductor 9. At this time, in the sensor circuit unit 15, a current (control that cancels out the magnetic field generated in the vicinity of the magnetoresistive effect elements 4 a to 4 d based on the output voltage detected from the connection areas 5 c and 5 d of the measured current detection unit 1. Current) is supplied to the compensation conductor. Specifically, the magnitude of the control current is adjusted so that the output voltage of the connection areas 5c and 5d becomes zero. The compensating conductive line generates a magnetic field generated in the vicinity of the four magnetoresistive elements 4a to 4d according to the magnitude of the control current, that is, a magnetic field that cancels out the magnetic field according to the magnitude of the current flowing through the primary conductor 9. appear.

Therefore, the imbalance of the bridge circuit 8 according to the magnitude of the current flowing through the primary conductor 9 can be repaired by the control current supplied from the sensor circuit unit 15.
Therefore, the magnitude of the control current supplied from the sensor circuit unit 15 can be detected as a value correlated with the magnitude of the current flowing through the primary conductor 9 or the magnitude of the current flowing through the primary conductor 9.

  The disturbing magnetic field generated outside the primary conductor 9 has an in-phase effect on the magnetoresistive elements 4a and 4b and the magnetoresistive elements 4c and 4d (each half bridge circuit on the left and right sides of the bridge circuit). And does not affect the measurement accuracy.

  Further, in the present embodiment, the example of the two shunt conductors 10a and 10b is shown. However, as shown in FIG. 8, a plurality of (here, three) shunt conductors 10a, 10b, and 10c may be used. I do not care.

  As described above, according to the first embodiment, four magnetoresistive elements 4 on the installation board and the first half bridge circuit in one area divided with respect to the center line 3 of the installation board 12 are arranged. And a second half bridge circuit are arranged in the other region, and a magnetic field in the opposite direction is applied to each half bridge circuit, so that a uniform external magnetic field can be removed.

  Further, since the primary conductor 9 has a shunt structure, it is possible to measure a large current, and since the sensor substrate 12 is installed substantially in parallel in the gap 11 of the shunt conductors 10a and 10b, the structure of the current sensor including the primary conductor 9 is small. And there exists an effect which installation of the sensor board | substrate 12 becomes easy.

<Embodiment 2>
FIG. 9 is a cross-sectional view showing a current sensor according to Embodiment 2 of the present invention. In the figure, the measured current detection unit 1 is placed on a flat installation substrate mounting portion 13 that does not take a concave shape on the sensor substrate 12. Installed. In order to install the measured current detector 1 at the symmetrical center, one of the sensor boards 12 is directly installed on the shunt conductor 10b in the installation part of the sensor board 12 and the shunt conductor 10, but the other is an auxiliary member. It becomes installation through 14a. Therefore, when one mounting member 14 is used on each side of the sensor substrate 12, one mounting member 14 sandwiches the sensor substrate 12 and the shunt conductor 10, and the other sandwiches the sensor substrate 12, the shunt conductor 10 and the auxiliary member 14a. And fix.

The second embodiment has a structure in which the auxiliary member 14a is added to the first embodiment and a part thereof is deformed, and the overlapping parts in other configurations are omitted.
In the present embodiment, an example in which one auxiliary member 14a is installed on one side has been shown. However, the auxiliary member 14a is not limited to one. You may adjust so that it may install in the center of symmetry.

  As described above, according to the second embodiment, since the measured current detection unit 1 is installed on a flat surface on the sensor substrate 12 that is not provided with a recess, connection with the sensor circuit unit 15, etc. The manufacturing process of the current sensor is simplified and the cost can be reduced.

<Third embodiment>
FIG. 10 is a cross-sectional view showing a current sensor according to Embodiment 3 of the present invention. In the figure, the two shunt conductors 10a and 10b have different shapes, and the measured current detector 1 is within the plane of the paper. The center line 3 of the measured current detector 1 shown in FIG. 5 and the portion where the magnetism becomes zero coincide with the portion where the distributed magnetic field becomes zero.

  Since the current-to-be-measured detection unit 1 is installed on the asymmetrical shunt conductor 10 having a different shape, the symmetrical shunt conductor having the same shape when the current shunt ratio in the shunt conductor portion is 9: 1, for example. It is only necessary to measure 1/5 of the current compared to measuring the current flowing through From this, the capacity and the like of the sensor circuit unit 15 can be reduced. In other words, a large current can be measured with a small current sensor.

  As described above, according to the third embodiment, the two shunt conductors 10a and 10b have different shapes, and the measured current detection unit 1 is located at a position where the magnetic field distributed in the plane of the paper becomes zero. Since the configuration is such that the center line 3 of the current-to-be-measured detection unit 1 and the location where the magnetism is zero coincide with each other, the shunt ratio can be lowered, and a large current can be easily measured.

<Embodiment 4>
FIG. 11 is a cross-sectional view showing a current sensor according to Embodiment 4 of the present invention. In the figure, electric field shield layer 17 covers the surface side of current-to-be-measured portion 1 via an insulating layer and It is also installed as the inner layer of the sensor substrate 12 on the back side of the current detection unit 1. Other configurations are the same as those in FIG.

  The electric field shield layer 17 is a nonmagnetic material having electrical conductivity, and is not shown in FIG. 11, but is grounded. In the fourth embodiment, the electric field shield layer 17 is installed so as to sandwich the measured current detection unit 1 from above and below, but it is a case-like electric field shield force bar covering the whole including the sensor substrate 12. May be. By providing the electric field shield layer 17 in this manner, it is possible to shield a disturbance electric field without being affected by electrical noise at the installation location, and current detection accuracy is further improved.

  As described above, according to the fourth embodiment, since the electric field shield layer 17 is provided, the disturbance electric field can be removed and the measurement accuracy can be improved.

It is a perspective view of the current sensor by Embodiment 1 of this invention. It is a top view of the current sensor by Embodiment 1 of this invention. It is a side view of the current sensor by Embodiment 1 of this invention. It is sectional drawing of the current sensor by Embodiment 1 of this invention. It is a top view which shows the to-be-measured current detection part of the current sensor by Embodiment 1 of this invention. It is a structure schematic which shows the to-be-measured current detection part of the current sensor by Embodiment 1 of this invention. It is a block diagram which has arrange | positioned the compensation conductive line by Embodiment 1 of this invention. It is a top view of another shunt conductor by Embodiment 1 of this invention. It is sectional drawing of the current sensor by Embodiment 2 of this invention. It is sectional drawing of the current sensor by Embodiment 3 of this invention. It is sectional drawing of the current sensor by Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current to be measured detection part 2 Installation board 3 Center line 4 Magnetoresistive element 5 Connection area 6 Connection current line 7 Half bridge circuit 8 Bridge circuit 9 Primary conductor 10 Shunt current conductor 11 Air gap part 12 Sensor board 13 Installation board attachment part 14 Attachment Member 14a Auxiliary member 15 Sensor circuit part 16 Compensation conductive wire 17 Electric field shield

Claims (5)

  First and fourth magnetoresistive elements arranged on the installation board and having magnetoresistive effect characteristics in which the resistance value increases together with an increase in the magnetic field in the opposite direction, and arranged on the installation board, Second and third magnetoresistive elements having magnetoresistive effect characteristics that both decrease in resistance value as the magnetic field increases in the reverse direction, and disposed on the installation substrate, the first to fourth magnetic elements A bridge comprising a first half bridge circuit by the first and second magnetoresistance effect elements and a second half bridge circuit by the third and fourth magnetoresistance effect elements by connecting the resistance effect elements. The first half-bridge circuit is disposed in one area separated from the center line of the installation board, and the connection current line constituting the circuit is disposed, and the first half-bridge circuit is disposed in the other area. A half-bridge circuit and a primary conductor having at least one opening, and the at least two shunt conductors provided on the primary conductor and separated by the opening include a lower surface of one shunt conductor The current sensor is characterized in that the upper surface of the other shunt conductor is arranged point-symmetrically with a predetermined gap and the sensor substrate is arranged substantially parallel to the gap.   The two shunt conductors provided with the primary conductor and separated by the opening provided in the primary conductor have the same cross-sectional shape, and the bottom surface of one shunt conductor and the other shunt conductor 2. The current sensor according to claim 1, wherein the upper surface of the shunt conductor is arranged point-symmetrically with a predetermined gap.   The two shunt conductors provided with one primary conductor having one opening and separated by the opening provided in the primary conductor have different cross-sectional shapes, and the bottom face of one shunt conductor and the other shunt The current sensor according to claim 1, wherein the upper surface of the conductor is disposed with a predetermined gap.   4. The apparatus according to claim 1, further comprising at least one attachment member that fixes a part of the sensor substrate and a part of the shunt conductor in close contact with each other or through an auxiliary member. The current / current sensor according to any one of the above.   5. The current sensor according to claim 1, wherein an electric field shield cover for removing a disturbance electric field is provided above, below, or both of the sensor substrate.

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