JP2013148513A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of accurately performing a current measurement even when bus-bars that connect a motor and an inverter are arranged adjacent to each other.SOLUTION: A current sensor 100 includes: a core 20 formed by stacking directional electromagnetic steel plates in an U-shape, in which each of at least three bus-bars 10 which comprises a flat-shaped conductor for connecting a three-phase motor and an inverter that energizes the three-phase motor, and are adjacent to each other so as to overlap each other by stacking each other as viewed along the flat plate-like thickness direction, is inserted to the side of an U-shaped bottom part 22 with a flat plate-like width direction of the bus-bar 10 being matched with the depth direction of the U-shaped U-groove; and a detection element 30 arranged so as to make a detection direction run along the interval direction of an opening 21 at the side of the U-shaped opening 21 and detect the strength of a magnetic field.

Description

  The present invention relates to a current sensor that measures a current flowing through a conductor.

  In recent years, hybrid vehicles and electric vehicles equipped with a motor and an inverter have become widespread. In order to properly control the rotation of the motor, it is important to measure the current flowing through the motor. As a method for measuring such current, a magnetic field generated around the conductor is detected according to the current flowing through the conductor connecting the motor and the inverter, and the current flowing through the conductor is calculated based on the detected magnetic field. There is what is required (for example, Patent Documents 1 and 2).

  The current sensor described in Patent Documents 1 and 2 includes a core and a Hall IC. The core is provided around the conductor so as to strengthen the magnetic field generated by the current flowing through the conductor. A gap is formed in a part of the core in the circumferential direction, and the Hall IC is disposed in the gap so that the detection surface of the Hall element is orthogonal to the direction of the lines of magnetic force generated in the gap.

JP 2007-155400 A JP 2005-308526 A

  Here, in a vehicle, a plate-like conductor is used from the viewpoint of heat generation because a large current flows through the motor. In addition, since a three-phase motor is used as the motor, a plurality of conductors are arranged in series. On the other hand, in the vehicle, the size of each equipment is reduced from the viewpoint of improving fuel consumption. For this reason, the conductors connecting the motor and the inverter are similarly reduced in size so that the adjacent plate-like conductors face each other in the longitudinal direction of the cross section intersecting the axial direction (direction in which the current flows). Has been placed in.

  However, when the plate-like conductors are arranged in this way, the distance between the adjacent plate-like conductors is reduced. For this reason, when the current is measured using the techniques described in Patent Documents 1 and 2, there is a problem that the current cannot be measured accurately due to the influence of the magnetic field caused by the current flowing in the adjacent plate-like conductor.

  In view of the above problems, an object of the present invention is to provide a current sensor that can accurately measure current even when bus bars connecting a motor and an inverter are arranged in parallel with each other. There is to do.

In order to achieve the above object, the characteristic configuration of the current sensor according to the present invention is:
Each of at least three bus bars is formed of a flat conductor connecting a three-phase motor and an inverter that energizes the three-phase motor, and is juxtaposed so as to overlap each other when viewed in the thickness direction of the flat plate. The directional magnetic steel sheets are formed in a U-shape, and are inserted into the U-shaped bottom portion side so that the width direction of the bus bar coincides with the depth direction of the U-shaped U-groove. The core,
A detection element arranged on the U-shaped opening side so that the detection direction is along the interval direction of the opening, and detecting the strength of the magnetic field;
It is in the point equipped with.

  With such a characteristic configuration, the detection element can be brought close to the bus bar, so that the detection element can be separated from the opening. For this reason, the core between the opening and the detection element can act as a shield against an external magnetic field (for example, a magnetic field from an adjacent bus bar). In other words, since the external magnetic field can be attracted to the core before the external magnetic field reaches the detection element, it is possible to appropriately detect the magnetic field from the bus bar inserted through the core while reducing the influence of the external magnetic field. It becomes. Therefore, even when the bus bars connecting the motor and the inverter are arranged in parallel with each other, current measurement can be accurately performed.

  In addition, it is preferable that the detection element is disposed on the edge side with respect to a central part of the opening and an edge on the opening side of the bus bar.

  With such a configuration, it is possible to reduce the influence on the detection element due to the magnetic field from the adjacent bus bar. Therefore, accurate current measurement can be performed.

  In the bus bar, it is preferable that the opening side of a portion overlapping the core when the core is viewed from the interval direction is notched.

  With such a configuration, the detection element can be further arranged on the back side of the core. Therefore, the influence on the detection element by the magnetic field from the adjacent bus bar can be reduced.

Moreover, the manufacturing method of the current sensor according to the present invention includes:
A laminating step of laminating a directional electrical steel sheet on a core rod having a track-shaped outer peripheral surface to produce an annular laminated core;
An adhering step of impregnating and adhering an adhesive to the annular laminated core; and
A dividing step of dividing the fixed annular laminated core into a plurality of parts;
There is a feature in having.

  With such a characteristic configuration, the core used for the current sensor can be easily manufactured. Therefore, the manufacturing cost of the current sensor can be reduced.

It is the perspective view which showed the current sensor typically. It is the front view which showed the current sensor typically. It is the III-III sectional view taken on the line of FIG. It is the figure which showed typically the manufacturing method of the core which an electric current sensor has.

1. Hereinafter, embodiments of the present invention will be described in detail. The current sensor 100 according to the present invention is configured to be able to measure a current to be measured flowing through a conductor. Here, when a current flows through the conductor, a magnetic field is generated around the conductor as an axis according to the magnitude of the current (Ampere's law), and a magnetic flux is generated by the magnetic field. The current sensor 100 detects the density of such magnetic flux, and measures the current (current value) flowing through the conductor based on the detected magnetic flux density.

  FIG. 1 is a perspective view of a current sensor 100 according to the present embodiment. FIG. 1 shows a bus bar 10 made of a flat conductor, and a direction in which the bus bar 10 extends is defined as an extending direction A. FIG. 2 schematically shows the current sensor 100 as viewed in the extending direction A of the bus bar 10. This will be described below with reference to FIGS.

  The current sensor 100 includes a bus bar 10, a core 20, and a detection element 30. The bus bar 10 is composed of a flat conductor as described above. The bus bar 10 is used to connect a three-phase motor (not shown) and an inverter that energizes the three-phase motor. The three-phase motor is used for a power source such as a hybrid vehicle or an electric vehicle. The inverter converts DC power output from a battery or the like into AC power. The bus bar 10 supplies the three-phase motor with the voltage and current converted into AC power by such an inverter. Therefore, the bus bar 10 is configured to have at least three as shown in FIG.

  At least three bus bars 10 are juxtaposed so as to overlap each other when viewed in the direction along the thickness direction of the flat plate. The plate-like thickness direction is a direction parallel to the thickness of the bus bar 10, and corresponds to the direction B in FIG. Being arranged side by side so as to overlap each other indicates a state in which the surfaces in the width direction of two adjacent bus bars 10 are disposed so as to face each other. Therefore, when the bus bars 10 having the same plate width are arranged side by side, when viewed in the thickness direction (direction B), the bus bars 10 arranged behind are hidden by the bus bars 10 arranged forward and cannot be seen. By arranging the bus bar 10 in this way, it is possible to wire the space between the three-phase motor and the inverter in a space-saving manner. In FIG. 1, only one bus bar 10 is shown for easy understanding.

  The core 20 is formed by laminating grain-oriented electrical steel sheets 60 in a U shape. The grain-oriented electrical steel sheet 60 is a metal magnetic body and corresponds to a silicon steel sheet. Lamination in a U-shape refers to a state in which U-shaped grain-oriented electrical steel sheets 60 are laminated. For this reason, a laminated surface turns into a surface parallel to the direction of A in FIG.1 and FIG.2. The core 20 is configured in such a state that such U-shaped grain-oriented electrical steel sheets 60 are laminated.

  Each of the bus bars 10 is inserted into the U-shaped bottom portion 22 side of the core 20 with the plate width direction of the bus bar 10 aligned with the depth direction of the U-shaped U groove. The U-shaped bottom portion 22 corresponds to the bottom portion of the U-groove that forms the U-shape. Therefore, the bus bar 10 is inserted through the bottom portion of the U groove of the core 20. Matching the plate width direction of the bus bar 10 with the depth direction of the U-shaped U-groove means arranging the bus bar 10 so that the surface of the bus bar 10 faces the inner surface of the U-groove. Accordingly, as shown in FIGS. 1 and 2, the bus bar 10 is inserted so that the surface in the plate width direction of the bus bar 10 and the surface in the depth direction of the U groove of the core 20 are parallel to each other. The bus bar 10 inserted through the core 20 is configured to have at least an inner surface of the core 20 and a gap. Thereby, the core 20 and the bus bar 10 can be insulated.

  The detection element 30 is arranged on the U-shaped opening 21 side so that the detection direction is along the interval direction of the opening 21. The opening 21 is an opening end of the U groove. Therefore, the detection element 30 is arranged on the opening end side in the U groove of the core 20. For this reason, the detection element 30 is arranged closer to the opening end of the U groove than the bus bar 10. Here, magnetic flux generated according to the current flowing through the bus bar 10 is collected in the core 20. The collected magnetic flux jumps over the gap formed by the opening 21 of the core 20 on the opening 21 side.

  The detection element 30 is arranged so that the detection direction coincides with the gap interval direction. Thereby, a magnetic path is formed by the core 20 and the detection element 30. Therefore, it is possible to detect the strength of the magnetic field formed by the current to be measured flowing through the bus bar 10.

  In the present embodiment, the detection element 30 is disposed closer to the edge than the center of the opening 21 and the edge of the bus bar 10 on the opening 21 side. The opening 21 is an opening end of the U groove. The edge of the bus bar 10 on the opening 21 side corresponds to a portion of the bus bar 10 that is inserted through the U groove and closest to the opening 21. The detection element 30 is disposed on the side close to the bus bar 10 between the opening 21 and the portion of the bus bar 10 closest to the opening 21. Thereby, since the core 20 exists between the detection element 30 and the opening part 21, even when the space | interval with the adjacent bus bar 10 becomes narrow, the influence of the magnetic flux from the adjacent bus bar 10 is reduced. It becomes possible to do. Therefore, the current flowing through the bus bar 10 can be accurately measured.

  Here, FIG. 3 shows a cross-sectional view taken along line III-III in FIG. As shown in FIG. 3, the bus bar 10 is cut out on the side of the opening 21 that overlaps the core 20 when the core 20 is viewed from the interval direction. The interval direction corresponds to the opposing direction of a pair of straight line portions constituting a U shape, and is the direction B in FIG. When the bus bar 10 according to this embodiment is viewed from this direction, the bus bar 10 is notched on the side of the opening 21 of the core 20 to form the notch 11. Thereby, it becomes possible to arrange | position the detection element 30 in the back | inner side of a U groove more. Therefore, even when the interval between the adjacent bus bars 10 is narrowed, the influence of the magnetic flux from the adjacent bus bars 10 can be reduced, so that the current flowing through the bus bars 10 can be accurately measured. .

  However, the notch depth (the depth in the C direction in FIG. 3) of the notch 11 with respect to the bus bar 10 is set according to the current flowing through the bus bar 10. That is, by increasing the notch depth, the position at which the detection element 30 is disposed can be located on the far side of the opening 21, but the cross-sectional area of the bus bar 10 is reduced, so that the resistance is increased. This is to prevent heat generation when current flows. For this reason, the notch depth of the notch part 11 is set according to the magnitude | size of the electric current which flows into the bus-bar 10. FIG. Thereby, it becomes possible to measure the current with high accuracy while suppressing the heat generation of the bus bar 10.

  As described above, according to the current sensor 100 of the present invention, it is possible to detect the strength of the magnetic field generated by the current flowing through the bus bar 10 by the detection element 30 while reducing the influence of the magnetic field from the adjacent bus bar 10. It becomes. Therefore, even when the bus bars 10 that connect the motor and the inverter are arranged in parallel with each other, it is possible to accurately measure the current.

2. Next, a method for manufacturing the current sensor 100, particularly a method for manufacturing the core 20 used in the current sensor 100 will be described with reference to FIG. In manufacturing the core 20, the core rod 50 having the outer peripheral surface 55 on the track is prepared (# 01). On the track corresponds to an outer peripheral edge having a pair of opposing linear portions 51 and a pair of circular arc upper portions 52 connecting both ends of the linear portions 51. For this reason, the outer peripheral surface 55 on the track corresponds to a surface formed by extending such an outer peripheral edge with a predetermined width L in the axial direction.

  The core rod 50 is laminated by winding the grain-oriented electrical steel sheet 60 (# 02). At this time, the width of the laminated grain-oriented electrical steel sheets 60 is adjusted to the width of the core 20 in advance. Therefore, the core-shaped rod 50 is wound with the sheet-shaped grain-oriented electrical steel sheet 60 cut to the width of the core 20. When the grain-oriented electrical steel sheet 60 previously cut to a predetermined width is wound around the core rod 50, (1) conventional equipment can be used, (2) there is no need to widen the equipment space, (3 ) There are advantages that it is easy to perform the spot welding described below, and (4) it is easy to improve the working efficiency by increasing the winding speed. Such lamination of the grain-oriented electrical steel sheets 60 is repeated several times until the thickness reaches a predetermined value. Such a process is called a lamination process.

  The laminated grain-oriented electrical steel sheets 60 are spot-welded (spot welded) at predetermined locations so as not to be unwound in the following annealing process (# 03). This is referred to as a welding process. After welding, the core rod 50 on the radially inner side of the laminated grain-oriented electrical steel sheets 60 is taken out (# 04). As a result, an annular laminated core (winding core) 61 in which the grain-oriented electrical steel sheet 60 is wound annularly is produced. The laminated core 61 is annealed in order to store the shape of the laminated state in the directional electromagnetic steel sheet 60 and to remove the strain inside the directional electromagnetic steel sheet 60 (# 05). This is called an annealing process. In addition, the annealing process can stabilize the magnetic characteristics of the core 20.

  Next, in the annular laminated core 61, the directional electromagnetic steel sheet 60 is fixed with an adhesive 70 so that the laminated directional electromagnetic steel sheets 60 are not separated (so as not to be separated). For example, the annular laminated core 61 is immersed in the storage layer 71 in which the adhesive 70 is stored, and the annular laminated core 61 is impregnated with the adhesive 70, and is then fixed by drying (# 06). Such a process is called a fixing process.

  In the fixing step, the annular laminated core 61 to which the laminated grain-oriented electrical steel sheets 60 are fixed is divided into a plurality of parts using, for example, a grinder 80 (# 07). Such a process is called a division process. A grindstone is used for such a grinder 80. This is because the magnetic characteristics stabilized by the annealing process deteriorate when the laser is used for division. In particular, in the division of the annular laminated core 61, the axial laminated core 61 is separated from the annular laminated core 61 by performing along the axial direction so as to pass through the respective midpoints of the pair of linear portions 51 in the axial direction. At the same time, two cores 20 can be obtained (# 08). The manufacturing method of the core 20 used for the current sensor 100 according to the present invention includes such steps.

  The core 20 manufactured in this way is arranged so that the bus bar 10 penetrates, and the detection element 30 is arranged in the opening 21 of the U groove of the core 20. Such a process can be configured using a well-known technique, and thus the description thereof is omitted.

3. Other Embodiments In the above embodiment, the detection element 30 has been described as being disposed on the back side of the U groove of the core 20. However, the scope of application of the present invention is not limited to this. Of course, the detection element 30 may be disposed in the vicinity of the opening 21.

  In the above embodiment, the detection element 30 has been described as being disposed on the side closer to the bus bar 10 between the opening 21 and the edge of the bus bar 10 on the opening 21 side. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to arrange the detection element 30 on the side close to the opening 21.

  In the above-described embodiment, the bus bar 10 has been described on the assumption that the notch portion 11 is formed on the opening 21 side of the portion overlapping the core 20 when the core 20 is viewed from the interval direction B. However, the scope of application of the present invention is not limited to this. Naturally, the current sensor 100 can be configured without forming the notch 11 in the bus bar 10.

  In the embodiment described above, in the dividing step in the method for manufacturing the core 20 used in the current sensor 100, it is assumed that the annular laminated core 61 passes through the midpoint of each of the pair of linear portions 51 when viewed in the axial direction. . However, the scope of application of the present invention is not limited to this. Of course, division at other positions is also possible.

  Further, in the dividing step, the annular laminated core 61 has a predetermined length in the axial direction before the annular laminated core 61 is divided into a plurality of pieces along the axial direction of the annular laminated core 61, and the axial direction It is also possible to perform the above-described dividing step after forming the plurality of annular laminated cores 61 by dividing in a direction orthogonal to the above.

  In the said embodiment, after spot-welding with respect to the laminated directional electromagnetic steel plate 60, it demonstrated taking out the core bar 50 of the laminated directional electromagnetic steel plate 60, and performing an annealing process. However, the scope of application of the present invention is not limited to this. It is possible to assemble the process so that the core rod 50 is taken out after the annealing process, and naturally the order of each process can be changed as appropriate.

  In the above embodiment, the description has been given assuming that the three bus bars 10 are arranged in parallel. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to use four or more bus bars 10.

  The present invention is applicable to a current sensor that measures a current flowing through a conductor.

DESCRIPTION OF SYMBOLS 10: Bus bar 20: Core 21: Opening part 22: Bottom part 30: Detection element 50: Core rod 60: Directional electrical steel sheet 61: Annular laminated core 70: Adhesive 100: Current sensor B: Spacing direction

Claims (4)

Each of at least three bus bars is formed of a flat conductor connecting a three-phase motor and an inverter that energizes the three-phase motor, and is juxtaposed so as to overlap each other when viewed in the thickness direction of the flat plate. The directional magnetic steel sheets are formed in a U-shape, and are inserted into the U-shaped bottom portion side so that the width direction of the bus bar coincides with the depth direction of the U-shaped U-groove. The core,
A detection element arranged on the U-shaped opening side so that the detection direction is along the interval direction of the opening, and detecting the strength of the magnetic field;
Equipped with a current sensor.   2. The current sensor according to claim 1, wherein the detection element is disposed closer to the edge than a center of the opening and an edge of the bus bar on the opening side.   3. The current sensor according to claim 1, wherein the bus bar is cut out on a side of the opening that overlaps the core when the core is viewed from the interval direction. A laminating step of laminating a directional electrical steel sheet on a core rod having a track-shaped outer peripheral surface to produce an annular laminated core;
An adhering step of impregnating and adhering an adhesive to the annular laminated core; and
A dividing step of dividing the fixed annular laminated core into a plurality of parts;
The manufacturing method of the current sensor which has.

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