JP6672901B2 - Current sensor unit - Google Patents

Description

  The present invention relates to a current sensor unit. In particular, the present invention relates to a current sensor unit including a current sensor element that measures a current flowing through each of a plurality of bus bars extending in parallel.

  In an inverter or the like that outputs three-phase alternating current, a current sensor unit including a current sensor element that measures the current of each phase may be used (for example, Patent Document 1). The current sensor unit of Patent Literature 1 includes a main body through which a plurality of bus bars through which current flows. The bus bar is a conductor using an elongated metal plate (or a metal bar). Inside the main body, a current sensor element is arranged so as to face each bus bar. A shield plate is provided inside the main body so as to surround each bus bar and the corresponding current sensor element. The current sensor element is generally a magnetoelectric conversion element, and the shield plate is provided to block an external magnetic field (noise magnetic field). Some of the plurality of shield plates are molded and supported by resin inside the main body.

JP 2015-108554 A

  If the shield plate is molded with a hard resin, it receives stress from the resin and causes distortion. The distortion of the shield plate causes deterioration of the shield plate and displacement from the original design, and the expected magnetic field blocking effect may not be obtained.

  The present specification relates to a current sensor unit in which a shield plate is embedded in a resin mold body through which a plurality of bus bars penetrate, and provides a technique for reducing stress applied to the shield plate from the resin mold body. By reducing the stress applied to the shield plate, the shield plate is prevented from being distorted or displaced.

  The current sensor unit disclosed in this specification is a unit that measures a current flowing through each of a plurality of bus bars extending in parallel. The current sensor unit includes a resin mold body and a shield plate. The resin mold body is molded so that a plurality of bus bars penetrate. A current sensor element corresponding to each bus bar is arranged on the resin mold so as to be adjacent to each bus bar. The shield plate is embedded in the resin mold body. The resin mold body has a fitting groove on a side surface facing a direction intersecting both the arrangement direction and the extension direction of the plurality of bus bars. The fitting groove extends over the plurality of bus bars, and has an inclined side surface that is inclined so that the groove width becomes smaller toward the bottom. Further, a projection for positioning the shield plate is provided at the bottom of the fitting groove. The shield plate is provided with a through hole that engages with the positioning projection, and is fitted so as to be in contact with the boundary between the bottom surface of the fitting groove and the inclined side surface. The fitting groove is filled with a resin having a lower hardness than the resin forming the resin mold body so as to cover the shield plate. This current sensor unit is not filled with one kind of resin so as to surround the shield plate, but a shield plate is attached so as to fit in a groove provided in the resin mold body, and a hardness of Fill with low another resin. The position of the shield plate is accurately determined by the boundary between the bottom surface and the inclined side surface of the fitting groove and the positioning projection. Therefore, the position of the shield plate is accurately determined without covering the whole with the hard resin of the resin mold body. Another resin filled in the fitting groove so as to cover the shield plate has a lower hardness than the resin forming the resin mold body. Therefore, the shield plate does not receive high stress from the resin mold body, and another resin covering the shield plate does not need to apply high stress to the shield plate. In this current sensor unit, the stress applied to the shield plate is reduced, so that the shield plate is prevented from being distorted or displaced. In addition, the hardness of the resin is evaluated, for example, by Rockwell hardness.

  The details and further improvements of the technology disclosed in this specification will be described in the following “Detailed description of the invention”.

It is a perspective view of the current sensor unit of an example. FIG. 3 is an exploded perspective view of a plurality of bus bars and a sensor board. It is a perspective view of a plurality of bus bars and a sensor board. FIG. 4 is an exploded perspective view in which a shield plate is separated from a resin mold body. FIG. 5 is a sectional view taken along line VV of FIG. 1. FIG. 6 is a sectional view taken along the line VI-VI of FIG. 1.

  The current sensor unit 2 according to the embodiment will be described with reference to the drawings. FIG. 1 shows a perspective view of the current sensor unit 2. The current sensor unit 2 is a unit in which six bus bars 3a to 3f penetrate the main body (resin molded body 20) and measures the current of each of the six bus bars 3a to 3f. The six bus bars 3a to 3f are provided inside, for example, an inverter that supplies AC power to two three-phase AC motors, and are conductors that transmit two sets of three-phase AC. Bus bars 3a to 3f shown in the figure are parts of long bus bars arranged inside the inverter. Hereinafter, when any one of the six bus bars 3a to 3f is shown without distinction, it is referred to as a bus bar 3. FIG. 5 is a cross-sectional view taken along the line VV of FIG. 1, and FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. These sectional views will be described later.

  Inside the resin mold body 20, a sensor substrate on which a plurality of current sensor elements are mounted and two shield plates are arranged. FIG. 2 is an exploded view of the six bus bars 3 and the sensor board 12. FIG. 3 is a perspective view showing a state where the sensor boards 12 are attached to the plurality of bus bars 3. 2 and 3, the illustration of the resin mold body 20 and the two shield plates is omitted.

  Each of the bus bars 3a to 3f is made of an elongated metal plate, and extends in parallel so that flat surfaces face each other. The X direction of the coordinate system in the drawing corresponds to the extending direction of the bus bar, and the Y direction corresponds to the direction in which the plurality of bus bars 3 are arranged. Each bus bar 3 is provided with notches 5 and 6 in a part thereof. The notches 5 and 6 are provided so as to cut out both edges when the wide surface of the bus bar is viewed in a plan view, and the cross sections of the bus bar are smaller than those of the other portions due to the notches 5 and 6. A small cross section 4 is formed. In FIG. 2, only the bus bars 3a and 3f are denoted by reference numerals 5 and 6 indicating notches and the reference numeral 4 indicating small cross-sections, and the other bus bars 3b to 3e are not denoted by reference numerals. ing. In FIG. 3, only the bus bar 3a is provided with reference numerals 5 and 6 indicating notches and reference numeral 4 indicating a small cross-section, and the other bus bars 3b to 3f are omitted. In FIG. 3, reference numeral 7a is assigned only to the current sensor element corresponding to the bus bar 3a, and reference numerals are omitted for the current sensor elements corresponding to the other bus bars 3b to 3f.

  The small cross sections 4 of the plurality of bus bars 3 are arranged so as to be alternately arranged in order along the direction in which the bus bars 3 are arranged. The sensor board 12 fits into the notches 5 of the plurality of bus bars 3. The sensor board 12 is provided with slits 13a to 13f into which the wide portions 5a adjacent to the cutouts 5 of the bus bars 3 are fitted. In addition, current sensor elements 7a to 7f are attached to the sensor board 12 at positions facing the small cross-section 4 of each bus bar 3. When any one of the current sensor elements 7a to 7f is shown without distinction, it is referred to as a current sensor element 7. Note that a connector for connecting a cable from an external controller and a printed wiring for connecting the terminal of the connector to each current sensor element 7 are mounted on the sensor board 12, but these are not shown. is there.

  The bus bar 3a and the current sensor element 7a that measures the current flowing through the bus bar 3a will be described. The current sensor element 7a is a magnetoelectric conversion element, and detects an induced magnetic field generated around the bus bar 3a due to a current flowing through the corresponding bus bar 3a. The current sensor element 7a is, for example, a Hall element. The voltage across the current sensor element 7a changes according to the magnitude of the magnetic field (magnetic flux) that has passed through. The upper controller of the current sensor unit 2 multiplies the voltage between both ends of the current sensor element 7a by a predetermined conversion coefficient, and specifies the magnitude of the current flowing through the bus bar 3a.

  The same applies to the other current sensor elements 7b to 7f. Each of the current sensor elements 7b to 7f measures a magnetic field (magnetic flux) caused by a current flowing through the corresponding bus bar 3b to 3f, and based on the measurement result, The magnitude of the current flowing through each of bus bars 3b to 3f is specified. Hereinafter, for convenience of description, the “magnetic field caused by the current flowing through the bus bar” is simply referred to as “the magnetic field of the bus bar”.

  The current sensor element 7 which is a magnetoelectric conversion element may also detect a magnetic field of a bus bar other than the corresponding bus bar and a magnetic field (noise magnetic field) outside the current sensor unit 2. Here, the magnetic field of the bus bar increases as the current density flowing through the bus bar increases. By providing notches 5 and 6 in the bus bar 3 to form a small cross-section 4 having a smaller cross-sectional area than other portions, and disposing a current sensor element 7 as a magnetoelectric conversion element near the small cross-section 4, The magnetic field measured by the current sensor element 7 is increased. In addition, by providing the small cross-sections 4 of the adjacent bus bars so as to be shifted in the bus bar extending direction, the influence of the magnetic field of the adjacent bus bars is suppressed, and the SN ratio of the current sensor element 7 is increased. Further, the current sensor unit 2 includes a plurality of bus bars 3 and a plurality of current sensor elements 7 in a direction (Z direction) intersecting both the extending direction (X direction) and the arrangement direction (Y direction) of the bus bars 3. And a pair of shield plates sandwiching the. A pair of shield plates reduce the noise magnetic field.

  The shield plate included in the current sensor unit 2 will be described. The resin molded body 20 is molded and formed such that the plurality of bus bars 3 in the state of FIG. 2 penetrate. In other words, the resin mold body 20 is molded so as to cover a part of the plurality of bus bars 3 extending in parallel. As will be described in detail later, the resin mold body 20 has a substrate groove into which the sensor substrate 12 is fitted. The sensor substrate 12 is arranged in the substrate groove after the resin mold body 20 is formed. The plurality of current sensor elements 7 are arranged inside the resin mold body 20. FIG. 4 shows a perspective view of the current sensor unit 2 including the resin mold body 20. However, the resin mold body 20 in FIG. 4 is before the shield plates 14 and 15 are attached. In FIG. 4, the shield plates 14 and 15 are illustrated separately from the resin mold body 20. The resin mold body 20 is formed so as to surround the plurality of bus bars 3 and penetrate the resin mold body 20. The upper surface of the resin mold body 20 in FIG. 4, that is, one side surface facing in a direction (Z direction) intersecting both the extending direction (X direction) and the arrangement direction (Y direction) of the plurality of bus bars 3. A groove 21 is provided. The fitting groove 21 extends along the direction in which the plurality of bus bars 3 are arranged, and extends over the plurality of bus bars 3. In addition, the protrusion 23 in the fitting groove is a portion that covers a wide portion adjacent to the notch 6 of the bus bar 3. A projection 22 for positioning the shield plate 15 is provided on the bottom surface of the fitting groove 21.

  A groove (fitting groove 26) similar to the fitting groove 21 is formed on the lower surface of the resin mold body 20 in FIG. 4, that is, both in the extending direction (X direction) and the arrangement direction (Y direction) of the plurality of bus bars 3. It is provided on the other side surface that faces the intersecting direction (Z direction). Although the fitting groove 26 is not visible in FIG. 4, the structure is the same as that of the fitting groove 21. However, another groove is provided on the bottom surface of the fitting groove 26. The other groove will be described with reference to FIGS.

  The shield plate 14 fits into a fitting groove 21 provided on the upper surface of the resin mold body 20, and the shield plate 15 fits into a fitting groove 26 provided on the lower surface of the resin mold body 20. The shield plate 14 is provided with slits 14a corresponding to each of the plurality of ridges 23. The shield plate 14 is provided with a through hole 14h into which the projection 22 fits. Similarly, the shield plate 15 is provided with slits 15a corresponding to each of the plurality of protrusions of the fitting groove 26 on the lower surface, and a through hole 15h into which a projection extending from the bottom of the fitting groove 26 is fitted. Is provided.

  Hereinafter, the relationship between the shield plates 14 and 15 and the resin mold body 20 will be described with reference to FIGS. FIG. 5 is a sectional view taken along the line VV of FIG. 1, and FIG. 6 is a sectional view taken along the line VI-VI of FIG.

  As shown in FIGS. 5 and 6, the side surfaces 21a and 21b of the fitting groove 21 are inclined such that the width of the fitting groove 21 becomes narrower toward the bottom. These side surfaces are hereinafter referred to as inclined side surfaces 21a and 21b. The shield plate 14 is fitted so as to be in contact with the boundary between the bottom surface of the fitting groove 21 and the inclined side surfaces 21a and 21b. As shown in FIG. 6, the through hole 14 h of the shield plate 14 is fitted into a projection 22 provided on the bottom surface of the fitting groove 21.

  The same applies to the fitting groove 26 on the lower surface of the resin mold body 20. The side surfaces 26a and 26b of the fitting groove 26 are inclined such that the width of the groove becomes smaller toward the bottom. These side surfaces are hereinafter referred to as inclined side surfaces 26a and 26b. The shield plate 15 is fitted so as to be in contact with the boundary between the bottom surface of the fitting groove 26 and the inclined side surfaces 26a and 26b. In FIG. 6, the left inclined side surface 26b of the fitting groove 26 is followed by a substrate groove 28 (described later) following the inclined side surface 26b, and a boundary between the inclined side surface 26b and the bottom surface of the fitting groove 26. Does not exist. However, except for the inclined side surface 26b on the left side of the fitting groove 26 in FIG. 6, there is a boundary between the inclined side surface and the bottom surface of the groove, and the shield plate 15 is fitted into the fitting groove 26 so as to contact the boundary. . As shown in FIG. 6, the through hole 15 h of the shield plate 15 is fitted into a projection 27 provided on the bottom surface of the fitting groove 26.

  Further grooves (substrate grooves 28) are provided on the bottom surface of the fitting grooves 26. The substrate groove 28 has a step 28a on the side surface where the groove width is narrowed in a step shape. The sensor board 12 is fitted into the step 28a. The substrate groove 28 is closed by the shield plate 15 after the sensor substrate 12 is installed.

  The fitting groove 21 is filled with another resin 29 so as to cover the shield plate 14. As another resin 29, a resin having a lower hardness than the resin forming the resin mold body 20 is used. The hardness of the resin is compared, for example, with Rockwell hardness. For example, an epoxy resin (Rockwell hardness: M80 to 100) is used for the resin mold body 20, and polycarbonate (Rockwell hardness: M78) is used for another resin 29. As another resin 29, a resin filler that is too soft to be suitable for the Rockwell hardness test may be used. The shield plate 14 fitted in the fitting groove 21 and the shield plate 15 fitted in the fitting groove 26 are sealed in the resin mold body 20 by another resin 29. Since the board groove 28 provided on the bottom surface of the fitting groove 26 is closed by the shield plate 15, it is possible to prevent another resin 29 from entering the board groove 28.

  The pair of shield plates 14 and 15 disposed so as to sandwich the plurality of bus bars 3 and the plurality of current sensor elements 7 are made of a ferromagnetic material such as ferrite, so that the current sensor elements 7 are protected from external noise magnetic fields. Cut off.

  The advantages of the fitting groove 21 having the inclined side surfaces 21a and 21b and the projection 22 and the other resin 29 filling the fitting groove 21 so as to cover the shield plate 14 will be described. The following description also applies to the fitting groove 26 having the inclined side surfaces 26a and 26b and having the protrusion 27, and another resin 29 filling the fitting groove 26 so as to cover the shield plate 15.

  If the shield plates 14 and 15 are completely sealed with the resin mold body 20 having high hardness, the shield plates 14 and 15 receive stress from the constituent resin of the resin mold body 20 and generate distortion. The distortion of the shield plates 14 and 15 may cause deterioration of the shield plates and a displacement from an initial position (designed position), and the expected magnetic field blocking effect may not be obtained. Further, the ferromagnetic material changes its magnetic properties when subjected to stress (magnetostriction effect). When the shield plates 14 and 15 made of a ferromagnetic material are subjected to stress, their magnetic properties change, and this may also be a cause that the initial magnetic field blocking effect cannot be obtained. The shield plate 14 (shield plate 15) of the embodiment is fitted in a fitting groove 21 (fitting groove 26) provided in the resin mold body 20, and another resin 29 having a low hardness is applied thereon. Covered. Since the shield plate 14 (shield plate 15) is not entirely covered with the resin mold body 20 made of a hard resin, it does not receive strong stress from the resin of the resin mold body 20. Further, another resin 29 covering the shield plate 14 (the shield plate 15) has a lower hardness than the resin of the resin mold body 20, so that this other resin 29 is also higher in the shield plate 14 (the shield plate 15). No stress is applied. Therefore, distortion of the shield plate 14 (shield plate 15) is suppressed.

  The shield plate 14 is fitted in the fitting groove 21 so as to be in contact with the boundary between the inclined side surfaces 21 a and 21 b of the fitting groove 21 and the bottom surface, and the through hole 14 h is fitted in the projection 22. I have. With this structure, the position of the shield plate 14 in the resin mold body 20 is accurately determined. Similarly, the shield plate 15 is fitted in the fitting groove 26 so as to be in contact with the boundary between the inclined side surfaces 26a and 26b of the fitting groove 26 and the bottom surface, and the through hole 15h is fitted in the projection 27. ing. With this structure, the position of the shield plate 15 in the resin mold body 20 is accurately determined. Since the relative positions of the shield plates 14 and 15 with respect to the resin mold body 20 (that is, the relative positions with respect to the bus bar 3 and the current sensor element 7) are accurately determined, the shield plates 14 and 15 can exhibit design performance. .

  Points to keep in mind regarding the technology described in the embodiment will be described. One of the opposite side surfaces of the fitting groove may be inclined, and the other may be perpendicular to the bottom surface. Further, the number of current sensor elements 7 provided in the current sensor unit is not limited to six.

  As shown in FIG. 6, there is a gap between the ridge 23 projecting into the fitting groove 21 and the slit 14 a of the shield plate 14. Even if there is a gap between the ridge 23 and the slit 14a, the shield plate 14 is in contact with the boundary between the opposed inclined side surface 21a and the opposed inclined side surface 21b and the bottom surface, and has a through hole. Since 14h is fitted to the projection 22, its position is accurately determined. The width of the slit 14a may be the same as the width of the ridge 23 so that the slit 14a and the ridge 23 also contribute to the positioning of the shield plate 14. The same applies to the shield plate 15 fitted in the fitting groove 26.

  As shown in FIGS. 5 and 6, the shield plate 15 does not have to be embedded so that the entire surface thereof is in contact with the resin. A groove (for example, the above-described substrate groove 28) and a hole are provided in a part of the surface of the resin mold body 20 which is in contact with the shield plate 15, and the region of the shield plate 15 corresponding to the groove and the hole is formed in the resin mold body 20. Not in contact with Nevertheless, it can be said that the shield plate 15 is fixed in contact with the resin mold body 20 at portions other than the grooves and holes, and the shield plate 15 is embedded in the resin mold body 20.

  Another resin 29 in the embodiment corresponds to an example of the “resin having a lower hardness than the resin forming the resin mold body” in the claims.

  As described above, specific examples of the present invention have been described in detail, but these are merely examples, and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and has technical utility by achieving one of the objects.

2: Current sensor units 3, 3a to 3f: Bus bar 4: Small cross section 5, 6: Notch 7, 7a to 7f: Current sensor element 12: Sensor substrate 13a to 13f: Slit 14, 15: Shield plate 14a, 15a: Slits 14h, 15h: Through hole 20: Resin molded bodies 21, 26: Fitting grooves 21a, 21b, 26a, 26b: Inclined side surfaces 22, 27: Projection 23: Projection 28: Board groove

Claims (1)

A current sensor unit that measures a current flowing through each of a plurality of bus bars extending in parallel,
A resin molded body molded so that the plurality of bus bars are penetrated, and a resin molded body in which a current sensor element corresponding to each bus bar is disposed so as to be adjacent to each bus bar,
A shield plate embedded in the resin mold body,
With
The resin mold body extends over a plurality of the bus bars on a side surface that faces a direction intersecting both the arrangement direction and the extending direction of the plurality of bus bars, and the groove width decreases toward the bottom. With a fitting groove having an inclined side surface that is inclined, a projection for shield plate positioning is provided at the bottom of the fitting groove,
The shield plate has a through hole that engages with the protrusion, and is fitted in the fitting groove so as to contact a boundary between a bottom surface of the fitting groove and the inclined side surface,
The current sensor unit, wherein the fitting groove is filled with a resin having a lower hardness than a resin forming the resin mold body so as to cover the shield plate.

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