JP2018169188A - Current detection device - Google Patents

Abstract

An object of the present invention is to suppress the influence of magnetic flux from a bus bar of another phase and perform highly accurate current detection.
A bus bar BU, BV, BW, which is arranged in parallel to the Y direction and extends in the X direction, and a magnetoelectric conversion element SU, SV, SW for detecting a current flowing in the bus bar BU, BV, BW. And magnetic shields 10 and 11 arranged so as to sandwich the bus bars BU, BV and BW and the magnetoelectric transducers SU, SV and SW in the Z direction. The bus bars BU, BV and BW are provided with a narrow portion BUS. , BVS, BWS, and the narrow portions BUS, BVS, BWS are arranged at positions not facing the adjacent narrow portions and at positions close to the magnetic shield 11, and the magnetoelectric transducers SU, SV, SW are The narrow portions BUS, BVS, BWS and the magnetic shield 11 are disposed.
[Selection] Figure 2

Description

  The present invention relates to a current detection device, and more particularly to a current detection device that detects a current flowing in a bus bar.

  A rotating electrical machine used for a hybrid vehicle or an electric vehicle includes three bus bars for a three-phase AC power supply (U phase, V phase, W phase) for electrical connection with the outside. And the electric current which flows through a bus bar is detected and control of a rotary electric machine is performed. As a device for detecting a current flowing through a bus bar, a current provided with three C-shaped magnetic blocks (magnet collection cores) surrounding each bus bar and three magnetoelectric transducers arranged in a C-shaped notch A detection apparatus is described in Patent Document 1, for example.

  In addition, it is required to reduce the pitch between the bus bars in order to reduce the size of the rotating electrical machine, and accordingly, the current detection device must also be reduced in size, and only a magnetoelectric conversion element is used without using a magnetic collecting core. A coreless current sensor that detects the current of the bus bar is also employed.

JP 2010-002277 A

  The current detection device described in Patent Document 1 is difficult to reduce in size because a magnetic flux collecting core is required for each phase bus bar. Moreover, since there is a magnetic flux collecting core, the number of parts is large and it is difficult to reduce the cost.

  On the other hand, the coreless current sensor can be miniaturized because it does not use a magnetic collecting core, but is affected by the magnetic flux of the current flowing through the bus bar of the other phase when detecting the current flowing through the bus bar of the predetermined phase. This influence causes a detection error and makes it difficult to detect current with high accuracy.

  Therefore, an object of the present invention is to suppress the influence of magnetic flux from the bus bar of the other phase and perform highly accurate current detection.

  The current detection device of the present invention is arranged in parallel to the first direction, and each of the bus bars extending in a second direction orthogonal to the first direction and the current flowing through the bus bar. And a pair of magnetic shields arranged so as to sandwich the bus bar and the magnetoelectric conversion element in a third direction orthogonal to the first direction and the second direction. Each bus bar has a narrow portion cut out from a side surface, and the narrow portion is located at a position not facing the adjacent narrow portion and at a position close to one of the magnetic shields. The magnetoelectric transducer is arranged between the narrow portion and one of the magnetic shields.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of the magnetic flux from the bus bar of another phase can be suppressed, and a highly accurate electric current detection can be performed. In particular, in a coreless current detection device that does not use a magnetic collecting core, highly accurate current detection can be performed, and the size of the device can be reduced.

It is a circuit diagram of a rotating electrical machine. It is a perspective view which shows schematic structure of the electric current detection apparatus in 1st Embodiment. It is aa sectional drawing of FIG. It is bb sectional drawing of FIG. It is cc sectional drawing of FIG. FIG. 6 is a characteristic diagram in which characteristics of currents IW and IV are superimposed. It is a characteristic view which shows the simulation result of the magnetic flux distribution in the aa cross section of FIG. It is a characteristic view which shows the simulation result of the magnetic flux distribution in the bb cross section of FIG. It is a perspective view which shows schematic structure of the electric current detection apparatus in 2nd Embodiment. It is a top view of the magnetic shield in a 2nd embodiment. It is a perspective view which shows schematic structure of the electric current detection apparatus in 3rd Embodiment. It is a side view of the bus bar in 3rd Embodiment.

  FIG. 1 is a schematic circuit diagram of a rotating electrical machine 1 in which the current detection device 6 according to the first embodiment is used. As shown in FIG. 1, the rotating electrical machine 1 includes a DC power source 2, an inverter 3, and a motor generator 4. Inverter 3 and motor generator 4 are electrically connected by bus bar B.

  The inverter 3 includes a power conversion unit 5 that converts direct current into alternating current, a current detection device 6 provided in the bus bar B, and a control device 7 that controls the power conversion unit 5. The power conversion unit 5 is configured by a circuit including a MOS transistor, a diode, and the like. The current detection device 6 detects the current flowing through the bus bar B and outputs the detected current value to the control device 7. The detailed configuration of the current detection device 6 will be described later.

  Control device 7 controls power converter 5 based on the current value input from current detection device 6 to control the rotational drive of motor generator 4.

  Next, the current detection device 6 will be described with reference to FIGS. FIG. 2 is a perspective view showing a schematic configuration of the current detection device 6. Each drawing shows an XYZ coordinate system, and each direction will be described using the XYZ coordinate system. The X direction (second direction) indicates the extending direction of the bus bar B, the Y direction (first direction) indicates the direction of the parallel arrangement of the bus bars B, and the Z direction (third direction) indicates the current detection device 6. The vertical direction is shown.

  The current detection device 6 includes a bus bar B including U-phase, V-phase, and W-phase bus bars BU, BV, and BW, magnetoelectric conversion elements SU, SV, and SW that detect currents of the bus bars BU, BV, and BW, respectively, A pair of magnetic shields 10 and 11 that suppress magnetic interference to the conversion elements SU, SV, and SW are provided.

  The bus bars BU, BV, and BW are arranged in parallel with each other in the Y direction and extend in the X direction. The magnetic shields 10 and 11 are disposed so as to sandwich the bus bars BU, BV, and BW and the magnetoelectric conversion elements SU, SV, and SW from the upper and lower sides in the Z direction. In addition, in order to show the arrangement configuration of the bus bars BU, BV, BW and the magnetoelectric transducers SU, SV, SW, etc., the magnetic shield 10 is shown by virtual lines.

  The magnetic shields 10 and 11 are made of, for example, a magnetic material such as high-permeability iron or ferrite, and have a flat plate shape that can cover the bus bars BU, BV, and BW and the magnetoelectric transducers SU, SV, and SW. is there. Further, the magnetic shield 11 is provided with substrates PU, PV, and PW on which the magnetoelectric conversion elements SU, SV, and SW are mounted.

  The magnetoelectric transducers SU, SV, SW detect magnetic flux generated when current flows through the bus bars BU, BV, BW, and calculate current values corresponding thereto. As the magnetoelectric conversion elements SU, SV, SW, Hall elements, MI elements (magnetic impedance elements), MR elements (magnetoresistance elements) and the like can be used.

  Next, the configuration of the bus bars BU, BV, and BW will be described in detail. The bus bars BU, BV, and BW are formed of a flat metal plate that is elongated in the X direction. The bus bars BU, BV, and BW are arranged in parallel to the Y direction so that the wide side surfaces face each other.

  The bus bars BU, BV, BW have wide portions BUL, BVL, BWL and narrow portions BUS, BVS, BWS formed by cutting out the wide portions BUL, BVL, BWL from the width direction. The cross-sectional areas of the narrow portions BUS, BVS, BWS are smaller than the cross-sectional areas of the wide portions BUL, BVL, BWL. Further, the cross-sectional areas of the wide portions BUL, BVL, and BWL are the same, and the cross-sectional areas of the narrow portions BUS, BVS, and BWS are also the same.

  The wide portions BUL, BVL, BWL and the narrow portions BUS, BVS, BWS are arranged in a staggered manner. That is, the narrow portion BUS is arranged so as not to face the adjacent narrow portion BVS, and the narrow portion BVS is arranged not to face the adjacent narrow portion BWS. In other words, the narrow portions BUS, BVS, BWS are arranged in a substantially V shape when viewed from the Z direction. The narrow portions BUS, BVS, and BWS are portions for detecting the current flowing through the bus bars BU, BV, and BW. The narrow portions BUS, BVS, and BWS are the wide portions BUL, BVL, and BWL except for the narrow portions BUS, BVS, and BWS. (See bus bar BV in FIG. 2).

  FIG. 4 shows a cross-sectional view taken along line bb of FIG. In FIG. 4, symbol WLC indicates the center line of the wide portion BWL. Reference sign WSC indicates the center line of the narrow portion BWS. The center line WSC of the narrow part BWS is close to the magnetic shield 11 side by a distance DW with respect to the center line WLC of the wide part BWL. That is, the narrow portion BWS is arranged offset to the magnetic shield 11 side with respect to the wide portion BWL. In this regard, referring to FIG. 3, the narrow portion BWS has a distance H1 between the magnetic shields 10 and 11 and the distance from the magnetic shield 10 to a distance H2 (distance H1> distance). H2), which is arranged close to the magnetic shield 11.

  A magnetoelectric conversion element SW is disposed between the narrow portion BWS and the magnetic shield 11. As shown in FIG. 3, the magnetoelectric conversion element SW is arranged so as to face the narrow portion BWS so that the magnetosensitive direction faces the Y direction.

  The bus bar BU has the same configuration as the bus bar BW, and the narrow portion BUS is offset from the wide portion BUL on the magnetic shield 11 side, and magnetoelectric conversion is performed in a portion facing the narrow portion BUS. Element SU is arranged.

  As shown in FIGS. 2 and 5, the narrow portion BVS of the bus bar BV is arranged in a different position from the narrow portion BWS of the bus bar BW, but the narrow portion BVS is similar to the narrow portion BWS of the bus bar BW. The wide portion BVL is arranged offset to the magnetic shield 11 side, and the magnetoelectric conversion element SV is arranged in a portion facing the narrow portion BVS. 4 and 5, other bus bars are not shown in order to avoid complication of the drawings.

  Next, the influence of the magnetic flux from the other-phase bus bar when detecting the magnetic flux of the self-phase bus bar will be described. Here, the influence of the magnetic flux from the bus bar BV (other phase) when detecting the magnetic flux of the bus bar BW (own phase) will be described, but the relationship between the other bus bars BU and BV is the same.

  4 and 5, the centers of currents flowing through the bus bars BV and BW are schematically shown as currents IV and IW, respectively. As shown in FIG. 4, the current IW passes through the center line WSC in the narrow portion BWS and passes through the center line WLC in the wide portion BWL. Thus, the current IW also flows while being offset to the magnetic shield 11 side.

  Then, the current IW flowing through the narrow portion BWS is detected by the magnetoelectric conversion element SW. Since the narrow area BWS has a small cross-sectional area, the current IW flows in a concentrated manner. For this reason, a large magnetic flux is generated in the narrow portion BWS. The magnetoelectric conversion element SW detects this magnetic flux and converts it into a current value. At this time, the magnetoelectric conversion element SW detects the magnetic flux of the Y direction component indicated by the arrow in FIG.

  On the other hand, as shown in FIG. 5, the current IV passes through the center line VLC in the wide portion BVL and passes through the center line VSC in the narrow portion BVS. That is, the current IV flows from the center line VLC along the center line VSC. Thus, the current IV also flows while being offset to the magnetic shield 11 side.

  FIG. 6 shows a state in which the currents IW and IV are overlapped when viewed from the magnetoelectric conversion element SW. As shown in FIG. 6, the position where the current IV flows is separated from the magnetoelectric conversion element SW by the distance D1 from the position where the current IW flows. As a result, the influence of the magnetic flux of the current IV can be suppressed.

  The reason for this will be described with reference to FIGS. 7 shows a simulation result of the magnetic flux distribution in the Y direction in the section aa in FIG. 2, and FIG. 8 shows a simulation result of the magnetic flux distribution in the Y direction in the section bb in FIG. 7 and 8, reference numeral GL indicates an area where the magnetic flux is small, and reference numeral GH indicates an area where the magnetic flux is large.

  In FIG. 7, the magnetic flux in the upper region GH1 of the bus bar BV is the largest, and then the magnetic flux in the lower region GH2 of the bus bar BV is the largest. Further, the magnetic flux is small in the region near the magnetic shields 10 and 11, and the magnetic flux in the regions GL1, GL2, GL3, and GL4 away from the regions GH1 and GH2 is also small. In particular, the magnetic flux in the regions GL3 and GL4 is the smallest.

  In FIG. 8, the magnetic flux in the region GH3 above the narrow portion BWS of the bus bar BW and behind the magnetic shield 10 is large. In addition, the magnetic flux is small in the region near the magnetic shields 10 and 11, and the magnetic fluxes in the regions GL5, GL6, and GL7 separated from the region GH3 are also small. In particular, the magnetic flux in the region GL6 is the smallest. 7 and 8, the magnetoelectric conversion element SW is indicated by a one-dot chain line.

  As can be seen from the relationship between the magnetoelectric conversion element SW and the currents IW and IV shown in FIG. 6 and the simulation results shown in FIGS. 7 and 8, the position of the magnetoelectric conversion element SW is far from the position where the current IV flows. Is less affected by the magnetic flux generated by. That is, the magnetoelectric conversion element SW is located in the region GL4 in FIG. 7, and is located in the region GL6 in FIG. Thus, the magnetoelectric conversion element SW is disposed at a position where the influence of the magnetic flux due to the current IV flowing through the bus bar BV is small.

  For this reason, as described above, the narrow portion BWS of the bus bar BW is close to the magnetic shield 11 and is alternately arranged with the narrow portion BUS of the adjacent bus bar BU so that the magnetoelectric conversion element SW is disposed in the narrow portion BWS. By arranging in the vicinity, the magnetic flux of the bus bar BW can be detected well, and the influence of the magnetic flux of the adjacent bus bar BU can be suppressed. As a result, highly accurate current detection can be performed.

  In addition, since the bus bar B is sandwiched by the pair of magnetic shields 10 and 11 from both sides in the Z direction, the bus bars BU, BV, and BW do not need to be individually enclosed, and the number of parts of the magnetic shield is reduced. In addition, the size can be reduced. As a result, the current detection device 6 can be reduced in size, and the cost can be reduced by reducing the number of parts. Therefore, it is possible to achieve both highly accurate current detection and downsizing and cost reduction.

  Next, a second embodiment will be described with reference to FIGS. The second embodiment is different from the first embodiment in the configuration of the magnetic shields 12 and 13, and the other configurations are the same as those in the first embodiment. Therefore, the configuration of the magnetic shields 12 and 13 will be described, and the others Description of the configuration of is omitted.

  As shown in FIG. 10, the magnetic shield 12 includes slits 12U, 12V, and 12W in which portions corresponding to the wide portions BUL, BVL, and BWL of the bus bars BU, BV, and BW are cut out. Similarly, the magnetic shield 13 has slits 13U, 13V, and 13W (see FIG. 9).

  For this reason, the space | interval of the magnetic shields 12 and 13 can be narrowed, without interfering with the wide part BUL, BVL, BWL of bus bar BU, BV, BW. As a result, the size of the current detection device 6 in the Z direction can be reduced. In addition to the effect of the current detection device 6 of the first embodiment, the current detection device 6 can be further downsized.

  Next, a third embodiment will be described with reference to FIGS. The third embodiment is different from the first embodiment in the shape of the bus bars BU, BV, and BW, and the other configurations are the same as those in the first embodiment. Therefore, the shapes of the bus bars BU, BV, and BW will be described. The description of other configurations is omitted.

  As shown in FIGS. 11 and 12, the narrow portions BUS, BVS, BWS of the bus bars BU, BV, BW are formed by cutting out one side end side of the wide portions BUL, BVL, BWL. Therefore, when forming the narrow portions BUS, BVS, BWS of the bus bars BU, BV, BW, the notches of the bus bars BU, BV, BW are compared with the bus bars BU, BV, BW of the first embodiment. Man-hours can be reduced.

  That is, in the bus bars BU, BV, BW of the first embodiment, the narrow portions BUS, BVS, BWS are formed by cutting out the wide portions BUL, BVL, BWL from both sides of the wide portions BUL, BVL, BWL. However, the narrow portions BUS, BVS, BWS of the third embodiment can form the narrow portions BUS, BVS, BWS by cutting out only one side of the wide portions BUL, BVL, BWL. It becomes possible to reduce processing man-hours.

  DESCRIPTION OF SYMBOLS 1 Rotating electrical machine 2 DC power supply 3 Inverter 4 Motor generator 5 Power conversion part 6 Current detection device 7 Control device 10, 11, 12, 13 Magnetic shield, B, BU, BV, BW Bus bar, BUL, BVL, BWL Wide part, BUS, BVS, BWS Narrow part, GH1, GH2, GH3, GL1, GL2, GL3, GL4, GL5, GL6, GL7 region, IV, IW current, PU, PV, PW substrate, SU, SV, SW Magnetoelectric transducer, VLC, VSC, WLC, WSC Center line.

Claims (1)

A plurality of bus bars arranged in parallel to the first direction and extending in a second direction orthogonal to the first direction;
A magnetoelectric transducer for detecting a current flowing in the bus bar;
A pair of magnetic shields arranged so as to sandwich the bus bar and the magnetoelectric conversion element in a third direction orthogonal to the first direction and the second direction;
With
Each bus bar has a narrow portion cut out from a side surface, and the narrow portion is disposed at a position not facing the adjacent narrow portion, and at a position close to one of the magnetic shields,
The magnetoelectric conversion element is disposed between the narrow portion and one of the magnetic shields.
A current detection device characterized by that.