JP2019012031A - Current sensor - Google Patents

Abstract

To provide a current sensor with a structure that current field derived in a current path next to a current path targeted for measurement is hard to be given as noise field to a magnetic sensing element detecting the current path targeted for measurement.SOLUTION: A first shield 11u and a second shield 12u are provided at a position across current path 2u of U phase and magnetic sensing element 5u. An outside end E2 of a second facing plane 13w of the second shield 12u is located between an outside end E1 of a first facing plane 13u of the first shield 11u and the magnetic sensing element 5u. An angle α between a magnetic line of force M2 caused by driving current flowing through a current path 2v of V phase and entering to the magnetic sensing element 5u, and an element vertical line Sv can be made small, and current field becomes hard to be detected by the magnetic sensing element 5u as noise field.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a current sensor in which a magnetic sensing element faces each of a plurality of current paths, and a current flowing through each current path is detected by the magnetic sensing element.

  In the current sensor described in Patent Document 1, a sensor element is opposed to each of two bus bars arranged in parallel in the X direction, and a magnetic field induced by a current flowing through each bus bar is a sensor element. Is detected. Each bus bar and the sensor element facing the bus bar are sandwiched by a pair of shield plates from the Z direction. By providing this shield plate, it is possible to block a magnetic field other than the magnetic field caused by the bus bar that is the target of current measurement by the magnetic sensor.

  However, in this structure, the lines of magnetic force induced by the current flowing in the bus bar located next to the bus bar that is the current measurement target are induced by the pair of shield plates and enter the magnetic sensor used for current measurement, There is a problem that this magnetic field line is detected as a noise magnetic field.

  Therefore, in the current sensor described in Patent Document 1, the magnetic sensor is arranged such that the magnetic sensing direction is inclined with respect to the X direction, and the magnetic lines of force induced by the current of the adjacent bus bar are sensitive to the magnetic sensor. The structure is difficult to enter from the magnetic direction to reduce the influence of magnetic field lines from adjacent bus bars as a noise magnetic field.

Japanese Unexamined Patent Publication No. 2016-200388

  However, the current sensor described in Patent Document 1 is induced by the current flowing in the current measurement target bus bar because the magnetic sensor's magnetic sensing direction is obliquely directed to the current measurement target bus bar. The component of the measurement magnetic field that is oriented in the direction of the magnetic sensing of the current sensor is reduced. Therefore, there is a problem that the detection sensitivity to a magnetic field induced by a bus bar that is a target of current measurement is lowered.

  Moreover, in the sensor board | substrate which supports the several current sensor, it is necessary to form the attachment surface for attaching a current sensor diagonally, and the structure of a sensor board | substrate becomes complicated. It is also difficult to optimally set the inclination angle of the current sensor in order to minimize the influence of the magnetic field caused by the current of the adjacent bus bar.

  The present invention solves the above-described conventional problems, and can reduce the influence of a noise magnetic field induced by a current flowing in an adjacent current path without arranging the sensitivity axis of the magnetic sensing element obliquely. An object of the present invention is to provide a current sensor.

The present invention provides a current sensor in which a magnetic sensing element facing each of a plurality of current paths arranged in parallel is provided, and a magnetic field induced by a current flowing in each of the current paths is detected by the magnetic sensing element. ,
When the direction that crosses all the current paths orthogonally is the horizontal direction, and the direction that is orthogonal to both the current direction and the horizontal direction of the current path is the vertical direction,
The magnetic sensing elements are opposed to the current paths from the vertical direction, and their sensitivity axes are directed in the horizontal direction.
A first shield and a second shield sandwiching both the current path and the magnetic sensing element from both sides in the vertical direction are provided, and the first shield is a plane parallel to both the current direction and the lateral direction. A first opposing plane facing the magnetic sensing element; and the second shield is a plane parallel to both the current direction and the lateral direction and facing the current path. And
Each of the first opposing plane and the second opposing plane has an outer end that faces the outside where the current path does not exist next to the first opposing plane, and the outer end of the second opposing plane is the first It is located between the said outer side edge part of an opposing plane, and the said magnetic sensing element.

  In the current sensor of the present invention, a distance between the magnetic sensing element and the first opposing plane is shorter than a distance between the magnetic sensing element and the second opposing plane.

In the current sensor of the present invention, the first shield and the second shield are individually provided for each of the current paths,
The first opposing plane and the second opposing plane can be configured to have the outer end and an inner end directed inward where the current path is adjacent.

  In the current sensor according to the present invention, in the first shield and the second shield facing each other, the inner end portion of the first opposing plane and the inner end portion of the second opposing plane are at the same position in the vertical direction. It is preferable to be formed.

In the current sensor of the present invention, the three current paths are provided, and the first shield and the second shield face each of the current paths,
In the first shield and the second shield positioned on both sides in the lateral direction, the outer end portion of the second opposing plane is positioned between the outer end portion of the first opposing plane and the magnetic sensing element. The inner end portion of the first opposing plane and the inner end portion of the second opposing plane are formed at the same position in the vertical direction,
In the first shield and the second shield located at the center in the longitudinal direction, both lateral ends of the first opposing plane and lateral ends of the second opposing plane are both longitudinal. They are formed at the same position.

  In the current sensor of the present invention, the lateral length of the first opposing plane is L, and the lateral distance between the outer end of the first opposing plane and the outer end of the second opposing plane is When the shortened length is Lc, the ratio of Lc / L is preferably 0.11 or more and 0.44 or less.

  According to the current sensor of the present invention, the outer end of the second opposing plane of the second shield is arranged closer to the magnetic sensing element than the outer end of the first opposing plane of the first shield. Of the magnetic field induced by the current in the current path, the component of the lines of magnetic force directed to the sensitivity axis of the magnetic sensing element can be reduced, and noise due to the magnetic field from the adjacent current path can be suppressed.

  In addition, since the sensitivity axis of the magnetic sensing element is oriented in the lateral direction in which a plurality of current paths are arranged, the detection sensitivity of the magnetic sensing element with respect to the magnetic field induced in the current path to be measured can be maintained high. . Also, the assembly of each magnetic sensing element is easy.

The perspective view which shows the current sensor of the 1st Embodiment of this invention, (A) is sectional drawing which cut | disconnected the current sensor shown in FIG. 1 by the II-II line, (B) is sectional drawing of the current sensor of a comparative example, (A) is explanatory drawing which shows the simulation result of the magnetic force line distribution in the current sensor shown in FIG. 1, (B) is explanatory drawing which shows the simulation result of the magnetic force line distribution in the current sensor of a comparative example, (A) is explanatory drawing which shows typically the inclination of the magnetic force line which goes to a magnetic detection element in the current sensor of embodiment of this invention, (B) is typical about the inclination of the magnetic force line which goes to a magnetic detection element in the current sensor of a comparative example. Explanatory diagram shown in the (A) is the shortening length of the outer edge part of the 2nd opposing plane in U phase in the current sensor of embodiment shown in FIG. 1, and the inclination angle with respect to the vertical direction (Z direction) of the magnetic force line toward a magnetic sensing element. FIG. 4B is a diagram showing the relationship, in the current sensor of the embodiment shown in FIG. 1, the shortened length of the outer end portion of the second opposing plane in the W phase and the longitudinal direction (Z direction) of the magnetic force lines toward the magnetic sensing element ) Is a diagram showing the relationship between the angle of inclination and (A) is the diagram which shows the change of the magnetic flux density given to a magnetic sensing element when a current is separately given to the U phase, V phase, and W phase in the current sensor of the first embodiment, and (B) In the current sensor of the first embodiment, a diagram showing the influence of the magnetic field caused by the current in the adjacent current path on the magnetic sensing element when current is applied to each of the U phase, V phase, and W phase; (A) is the diagram which shows the change of the magnetic flux density given to a magnetic sensing element when a current is separately given to the U phase, V phase, and W phase in the current sensor of the second embodiment, and (B) is a diagram. In the current sensor of the second embodiment, a diagram showing the influence of the magnetic field caused by the current in the adjacent current path on the magnetic sensing element when current is applied to each of the U phase, V phase, and W phase, (A) is a diagram showing changes in magnetic flux density applied to the magnetic sensing element when current is individually applied to the U phase, V phase, and W phase in the current sensor of the comparative example, and (B) is a comparative example. FIG. 5 is a diagram showing the influence of a magnetic field caused by a current in an adjacent current path on a magnetic sensing element when current is applied to each of the U phase, V phase, and W phase in the current sensor of FIG. Sectional drawing which shows the current sensor of the 2nd Embodiment of this invention,

1 and 2A show a current sensor 1 according to a first embodiment of the present invention.
The current sensor 1 detects the amount of current flowing through the three current paths 2u, 2v, 2w and changes thereof. A drive current for driving a three-phase AC motor used in an automobile or the like flows through the current paths 2u, 2v, and 2w. A U-phase drive current Iu flows through the current path 2u, a V-phase drive current Iv flows through the current path 2v, and a W-phase drive current Iw flows through the current path 2w. The drive currents Iu, Iv, and Iw are relatively large-capacity alternating currents, each having a phase difference of 120 degrees.

  The current paths 2u, 2v, 2w are called bus bars and are formed of a low-resistance metal material such as copper or a copper alloy. The current paths 2u, 2v, 2w have a flat plate shape, are linear in the Y direction, and extend in parallel to each other. As shown in FIG. 2A, the current paths 2u, 2v, 2w have a rectangular cross-sectional shape. In the current paths 2u, 2v, and 2w, the surface on the Z1 side and the surface on the Z2 side are planes parallel to the XY plane. In the cross-sectional view shown in FIG. 2A, the surface on the Z1 side and the surface on the Z2 side Is long and extends in the X1-X2 direction.

  In the current sensor 1, the X direction which is a direction orthogonally crossing all the current paths 2u, 2v and 2w is a horizontal direction. The Y direction is the current direction in which the drive currents Iu, Iv, Iw flow in the current paths 2u, 2v, 2w. The Z direction, which is the direction perpendicular to both the Y direction, which is the current direction, and the X direction, which is the horizontal direction, is the vertical direction.

  As shown in FIG. 2A, the printed wiring board 3 is provided on the Z1 side of the current paths 2u, 2v, 2w. The mounting surface 3a which is the lower surface of the printed wiring board 3 is a plane parallel to both the horizontal direction (X direction) and the current direction (Y direction). Magnetic detection elements 5 u, 5 v, 5 w are mounted on the mounting surface 3 a of the printed wiring board 3. The magnetic sensing element 5u is positioned on a center line Ou that bisects the U-phase current path 2u in the lateral direction (X direction), and faces the current path 2u from the Z1 side. The magnetic detection element 5v is located on a center line Ov that bisects the V-phase current path 2v in the lateral direction (X direction), and faces the current path 2v from the Z1 side. Further, the magnetic detection element 5w is positioned on a center line Ow that bisects the W-phase current path 2w in the lateral direction (X direction), and faces the current path 2w from the Z1 side.

  The magnetic sensing elements 5u, 5v, 5w are configured by a magnetoresistive effect element (GMR element) using a giant magnetoresistive effect, a magnetoresistive effect element (TMR element) using a tunnel effect, or one or a plurality of Hall elements. The sensitivity axis, which is the axis with the highest sensitivity to magnetic field lines, is directed in the lateral direction (X direction).

  As shown in FIG. 2A, the U-phase current path 2u and the magnetic sensing element 5u are sandwiched between the first shield 11u and the second shield 12u from both sides in the longitudinal direction (Z direction). The first shield 11u has a first opposing plane 13u that faces the magnetic sensing element 5u from the Z1 side, and the second shield 12u has a second opposing plane 14u that faces the current path 2u from the Z2 side. . The V-phase current path 2v and the magnetic sensing element 5v are sandwiched between the first shield 11v and the second shield 12v from both sides in the vertical direction (Z direction). The first shield 11v has a first opposing plane 13v that faces the magnetic sensing element 5v from the Z1 side, and the second shield 12v has a second opposing plane 14v that faces the current path 2v from the Z2 side. . Further, the W-phase current path 2w and the magnetic sensing element 5w are also sandwiched between the first shield 11w and the second shield 12w from both sides in the longitudinal direction (Z direction). Similarly, the first shield 11w has a first opposing plane 13w, and the second shield 12w has a second opposing plane 14w.

  The U-phase first shield 11u and second shield 12u, the V-phase first shield 11v and second shield 12v, and the W-phase first shield 11w and second shield 12w are all made of Ni-Fe alloy or the like. It is made of a magnetic material with high magnetic permeability.

  The first opposing planes 13u, 13v, 13w of the first shields 11u, 11v, 11w are located on the same plane parallel to both the current direction (Y direction) and the lateral direction (X direction). The second opposing planes 14u, 14v, 14w of the second shields 12u, 12v, 12w are located on the same plane parallel to both the current direction (Y direction) and the lateral direction (X direction).

  Between the current paths 2u, 2v, 2w and the printed wiring board 3, between the printed wiring board 3 and the first shields 11u, 11v, 11w, and between the current paths 2u, 2v, 2w and the second shields 12u, 12v, 12w Is embedded with an insulating material and is electrically insulated. A resin material or the like is used as the insulating material. Further, without using an insulating material such as resin, the printed wiring board 3, the first shields 11u, 11v, 11w, the second shields 12u, 12v, 12w, and the like are supported by a support member such as a housing, and each member Gaps may be formed between them.

  As shown in FIG. 2A, the first opposing plane 13u formed on the U-phase first shield 11u faces the outside (X1 side) where the current path, the first shield, and the second shield do not exist next to each other. It has an outer end E1, and an inner end E3 facing the inner side (X2 side) where the current path 2v, the first shield 11v, and the second shield 12v exist next to each other. Similarly, the second opposing plane 14u formed on the U-phase second shield 12u has an outer end E2 facing the X1 side and an inner end E3 facing the X2 side.

  The width dimension in the lateral direction (X direction) of the first opposing plane 13u formed on the U-phase first shield 11u is L1, and the width dimension in the lateral direction of the second opposing plane 14u formed on the second shield 12u. Is shorter than the width dimension L1. And the outer side edge part E2 of the 2nd opposing plane 14u is located in the X2 side rather than the outer side edge part E1 of the 1st opposing plane 13u. That is, the outer end E2 of the second opposing plane 14u is located between the outer end E1 of the first opposing plane 13u and the magnetic detection element 5u. The distance in the X direction between the outer end E1 and the outer end E2 is the shortened length Lc of the second opposing plane 14u. The inner end E3 of the U-phase first opposing plane 13u and the inner end E3 of the second opposing plane 14u are at the same position in the vertical direction (Z direction).

  The first opposing plane 13w formed in the W-phase first shield 11w has an outer end E1 facing the outer side (X2 side) where no current path or first shield and second shield exist adjacent to each other, and an adjacent current path. 2v, an inner end E3 facing the inner side (X1 side) where the first shield 11v and the second shield 12v exist. The second opposing plane 14u formed on the U-phase second shield 12u has an outer end E2 facing the X2 side and an inner end E3 facing the X1 side.

  The width dimension in the lateral direction (X direction) of the first opposing plane 13w formed on the W-phase first shield 11w is L1, and the width dimension in the lateral direction of the second opposing plane 14w formed on the second shield 12w. Is shorter than the width dimension L1. The width dimension L1 of the U-phase first opposing plane 13u and the width dimension L1 of the W-phase first opposing plane 13w are the same. The outer end E2 of the second opposing plane 14w of the W phase is located closer to the X1 side than the outer end E1 of the first opposing plane 13w, and the outer end E2 of the second opposing plane 14w is the first opposite. It is located between the outer end E1 of the plane 13w and the magnetic sensing element 5w. Also in the W phase, the distance in the X direction between the outer end E1 and the outer end E2 is the shortened length Lc of the second opposing plane 14w. The inner end E3 of the W-phase first opposing plane 13w and the inner end E3 of the second opposing plane 14w are at the same position in the vertical direction (Z direction).

  The first opposing plane 13v formed on the V-phase first shield 11v located at the center and the second opposing plane 14v formed on the second shield 12v are both end portions E4 in the vertical direction (Z direction). ) In the same position. The width dimension L2 of the first opposing plane 13v and the second opposing plane 14v in the V phase is shorter than the width dimension L1 of the first opposing planes 13u and 13w in the U phase and the V phase. However, the width dimension L2 may be larger than the width dimension L1, and the width dimension L1 and the width dimension L2 may be the same.

  Inner ends E3 facing the X2 side of the U-phase first opposing plane 13u and the second opposing plane 14u, and ends facing the X1 side of the V-phase first opposing plane 13v and the second opposing plane 14v, respectively. An interval δ is provided in the horizontal direction (X direction) between E4 and E4. Also, the inner end E3 facing the X1 side of each of the W-phase first opposing plane 13w and the second opposing plane 14w, and the X2-side of each of the V-phase first opposing plane 13v and the second opposing plane 14v. An interval δ is also provided in the lateral direction (X direction) between the end portion E4 and the end portion E4.

FIG. 2B shows a current sensor 101 of a comparative example.
The current sensor 101 of the comparative example has the same components as the current sensor 1 of the first embodiment shown in FIG. However, the first opposing plane 13u formed on the U-phase first shield 11u and the second opposing plane 14u formed on the second shield 12u have the same width dimension L1 in the lateral direction, and the first opposing plane 13u and the 2nd opposing plane 14u have the both ends E3 and E5 of the horizontal direction corresponded in the vertical direction (Z direction). Also in the W phase, the first opposing plane 13w and the second opposing plane 14w have the same lateral width L1, and the first opposing plane 13w and the second opposing plane 14w have both end portions E3 in the lateral direction. , E5 coincide in the vertical direction (Z direction).

Next, the operation of the current sensor 1 will be described.
In the current sensor 1, the three-phase AC motor is driven by the drive currents Iu, Iv, Iw flowing in the current paths 2u, 2v, 2w. The drive currents Iu, Iv, and Iw are alternating currents whose phases are different from each other by 120 degrees.

  The current magnetic field induced by the drive current Iu flowing in the U-phase current path 2u is detected by the magnetic detection element 5u facing the current path 2u. Since the sensitivity axis of the magnetic detection element 5u is oriented in the horizontal direction (X direction), the component of the current magnetic field directed in the X direction is detected by the magnetic detection element 5u. The X-direction component of the current magnetic field induced by the drive current Iv flowing in the V-phase current path 2v is detected by the magnetic detection element 5v facing the current path 2v, and the drive current Iw flowing in the W-phase current path 2w. The component in the X direction of the induced current magnetic field is detected by the magnetic detection element 5w facing the current path 2w.

  The magnetic sensing elements 5u, 5v, 5w detect the X-direction component of the current magnetic field induced by the drive currents Iu, Iv, Iw flowing in the current paths 2u, 2v, 2w with the sensitivity axis directed in the X direction. Therefore, it is possible to detect the magnetic field with high sensitivity by using the magnetic detection elements 5u, 5v, and 5w. Further, since the mounting surface 3a of the printed wiring board 3 is a flat surface, the mounting work of the magnetic sensing elements 5u, 5v, 5w on the mounting surface 3a is easy.

  The U-phase current path 2u is sandwiched between the first shield 11u and the second shield 12u, the V-phase current path 2v is sandwiched between the first shield 11v and the second shield 12v, and the W-phase current path 2w is the first shield. 11w and the second shield 12w. Therefore, it is possible to block noise magnetic fields other than the magnetic field caused by the drive currents Iu, Iv, and Iw flowing in the current paths 2u, 2v, and 2w.

  However, in the current sensor 1 that detects the drive currents Iu, Iv, and Iw flowing through the plurality of current paths 2u, 2v, and 2w arranged in parallel, the magnetic detection element facing the current path to be measured is There is a problem that a current magnetic field induced by a drive current flowing in a current path located adjacently acts as a noise magnetic field.

  FIG. 3A shows the relationship between the distribution of the lines of magnetic force induced by the drive current Iv flowing in the V-phase current path 2v and the U-phase magnetic sensing element 5u in the current sensor 1 of the first embodiment. It is shown as a simulation result. FIG. 3B shows, as a simulation result, the relationship between the distribution of magnetic lines of force induced by the drive current Iv flowing in the V-phase current path 2v and the U-phase magnetic sensing element 5u in the current sensor 101 of the comparative example. It is shown.

  4A is a schematic diagram for explaining the simulation result shown in FIG. 3A, and FIG. 4B is a schematic diagram for explaining the simulation result shown in FIG. 3B. is there. 4A and 4B show a lateral center line O1 that passes through the center of the opposing distance between the first opposing plane 13u of the first shield 12u and the second opposing plane 14u of the second shield 12u. Yes.

  In both the current sensor 1 of the first embodiment shown in FIG. 3A and the current sensor 101 of the comparative example shown in FIG. 3B, the drive current Iv flows through the V-phase current path 2v. A part of the magnetic field lines of the current magnetic field induced by the current Iv are drawn into the first shield 11v and the second shield 12v facing the current path 2v, and a part of the magnetic field lines are adjacent to each other with a distance δ. The U-phase first shield 11u and the second shield 12u are positioned. The magnetic lines of force that cross between the U-phase first shield 11u and the second shield 12u are applied to the magnetic sensing element 5u facing the U-phase current path 2u.

  3B and 4B, in the current sensor 101 of the comparative example, the current is induced by the drive current Iv flowing in the V-phase current path 2v, and is applied to the U-phase first shield 11u and the second shield 12u. Of the guided magnetic flux, the line of magnetic force crossing between the outer end portions E5 of both the first opposed plane 13u and the second opposed plane 14u is indicated by Ma, and the first opposed plane 13u and the second opposed plane 14u The magnetic field lines that cross the gap and enter the magnetic sensing element 5u are indicated by Mb.

  In the current sensor 101 of the comparative example, both outer end portions E5 of the first opposing plane 13u of the U-phase first shield 11u and the second opposing plane 14u of the second shield 12u are on the same line in the vertical direction (Z direction). Is located. Therefore, the magnetic field lines Ma between the respective outer ends E5 extend in a line-symmetric shape in the longitudinal direction (Z1-Z2 direction) with respect to the lateral center line O1, and project in the X1 direction. Go through the bulging path. The magnetic lines of force Mb entering the magnetic detection element 5u also extend symmetrically in the vertical direction with respect to the horizontal center line O1 and pass through a path that bulges in a protruding shape in the X1 direction.

  In FIG. 4B, an angle between an action line at which the magnetic force line Mb acts on the magnetic detection element 5u and an element vertical line Sv that passes through the magnetic detection element 5u and extends in the vertical direction is indicated by β. Since the magnetic field lines Mb project in the X1 direction and pass through a path that is line-symmetric in the Z direction with respect to the lateral center line O1, the angle β is increased in the comparative example.

  3A and 4A, in the current sensor 1 of the first embodiment, the U-phase first shield 11u and the second shield are induced by the drive current Iv flowing through the V-phase current path 2v. Of the magnetic flux guided to 12u, the magnetic field lines crossing between the outer end E1 of the first opposing plane 13u and the outer end E2 of the second opposing plane 14u are indicated by M1, and the first opposing plane 13u and the first Magnetic field lines that enter between the two opposing planes 14u and enter the magnetic sensing element 5u are indicated by M2.

  In the current sensor 1 of the first embodiment, the outer end E2 of the second opposing plane 14u of the second shield 12u is closer to the X2 side than the outer end E1 of the first opposing plane 13u of the U-phase first shield 11u. The outer end E2 is located between the outer end E1 and the magnetic sensing element 5u. Therefore, the magnetic force line M1 crossing the space between the outer end E1 and the outer end E2 has an asymmetric shape in the longitudinal direction (Z1-Z2 direction) with respect to the lateral center line O1, and is shown in FIG. It passes through a path inclined counterclockwise (γ direction) with respect to the magnetic field line Ma between the outer end portions E5 shown. Following this, the magnetic force line M2 entering the magnetic detection element 5u also has an asymmetric shape in the vertical direction (Z1-Z2 direction) with respect to the horizontal center line O1, and is γ more than the magnetic force line Mb shown in FIG. It passes through a path inclined in the direction.

  As a result, as shown in FIG. 4A, the angle α between the action line at which the magnetic force line Mb acts on the magnetic detection element 5u and the element vertical line Sv that passes through the magnetic detection element 5u and extends in the vertical direction is It becomes smaller than the angle β shown in FIG.

  In the current sensor 1 of the embodiment, the angle α between the line of action where the magnetic force line M2 acts on the magnetic detection element 5u and the element vertical line Sv is smaller than the angle β of the current sensor 101 of the comparative example. Since the sensitivity axis of the magnetic sensing element 5u is oriented in the lateral direction (X direction), the current sensor 1 of the first embodiment is more sensitive to the magnetic sensing element 5u than the current sensor 101 of the comparative example. It is possible to reduce the component of magnetic field lines that are parallel to the axis, and to suppress the influence of the current magnetic field induced by the drive current of the current path located next to the current path to be measured as a noise magnetic field. Become.

  As shown in FIG. 2 (A), the first shield 11w and the second shield 12w located at the position sandwiching the W-phase current path 2w are located on the second opposing plane 14w rather than the outer end E1 of the first opposing plane 13w. The outer end E2 is located on the X1 side. Therefore, the relationship between the magnetic lines of force induced by the drive current Iv flowing in the V-phase current path 2v and the magnetic detection element 5w for detecting the W-phase is compared to FIGS. 3 (A) and 4 (A). It becomes a line symmetrical shape in the horizontal direction (X direction). Accordingly, similarly in the W phase, it is possible to reduce the noise that the magnetic flux induced by the drive current Iv flowing in the V-phase current path 2v gives to the magnetic detection element 5w.

  As shown in FIG. 2A, the current sensor 1 of the first embodiment includes a U-phase first shield 11u and a second shield 12u, a V-phase first shield 11v, a second shield 12v, and a W-phase. The first shield 11w and the second shield 12w are provided separately for each phase. For this reason, the magnetic field from the outside can be individually shielded for each phase, and is not easily affected by the noise magnetic field from the outside.

  However, in the present invention, without providing the interval δ shown in FIG. 2A, the first shield is continuous in the X direction and the second shield is also continuous in the X direction in the U phase, the V phase, and the W phase. It may be a structure.

FIG. 9 shows a current sensor 201 according to the second embodiment of the present invention.
The current sensor 201 includes U-phase and W-phase two-phase current paths 2u and 2w, a first shield 11u and a second shield 12u disposed between the U-phase current path 2u, and a W-phase current. A first shield 11w and a second shield 12w arranged at positions sandwiching the path 2w are provided. A magnetic sensing element 5u is provided between the U-phase current path 2u and the first shield 11u, and a magnetic sensing element 5w is provided between the W-phase current path 2w and the first shield 11w. Two currents out of drive currents for driving the three-phase AC motor flow through the current paths 2u and 2w.

  As shown in FIG. 9, the outer end E2 of the second opposing plane 14u of the second shield 12u is X2 by the shortened length Lc with respect to the outer end E1 of the first opposing plane 13u of the U-phase first shield 11u. Located in the direction. The outer end E2 of the second opposing plane 14w of the second shield 12w is positioned in the X1 direction by the shortened length Lc with respect to the outer end E1 of the first opposing plane 13w of the W-phase first shield 11w. Yes.

  Also in this current sensor 201, since the outer end E2 is shortened by the shortened length Lc with respect to the outer end E1, it is possible to reduce the influence of noise caused by the current magnetic field induced in the adjacent current path. it can.

  In the current sensor according to the embodiment of the present invention, the current flowing in the current path may be a current other than the driving current for the motor.

The characteristics of the current sensor 1 having the following structure were simulated.
(Explanation of FIGS. 5A and 5B)
In the current sensor 1 of the first embodiment shown in FIG. 2A, the thickness dimension H1 in the vertical direction (Z direction) of the current paths 2u, 2v, 2w is 4 mm, and the current paths 2u, 2v, 2w The width dimension in the direction (X direction) was 15 mm. The U-phase first shield 11u and the second shield 12u, the V-phase first shield 11v and the second shield 12v, and the W-phase first shield 11w and the second shield 12w are all in the vertical direction (Z direction). The thickness dimension was 1.5 mm.

  The distance H2 in the vertical direction (Z direction) between the surface of the current paths 2u, 2v, 2w facing the Z1 side and the magnetic detection elements 5u, 5v, 5w was 2.5 mm. The distance H3 in the vertical direction (Z direction) between the surface facing the Z1 side of the current paths 2u, 2v, 2w and the first opposing planes 13u, 13v, 13w of the first shields 11u, 11v, 11w is 5 mm, The distance H4 in the vertical direction (Z direction) between the surface facing the Z2 side of the paths 2u, 2v, 2w and the second opposing planes 14u, 14v, 14w of the second shields 12u, 12v, 12w was 2 mm.

  FIG. 5A shows a shortened length Lc in the X2 direction of the outer end E2 of the second opposing plane 14u relative to the outer end E1 of the U-phase first opposing plane 13u, and the magnetic field lines M2 shown in FIG. 4A. Shows the relationship between the line of action acting on the magnetic sensing element 5u and the angle α between the element vertical line Sv. In FIG. 5B, the shortened length Lc in the X1 direction of the outer end E2 of the second opposing plane 14w with respect to the outer end E1 of the W-phase first opposing plane 13w and the magnetic force lines M2 are applied to the magnetic sensing element 5u. The relationship between the action line when acting and the angle α between the element vertical line Sv is shown.

  5A and 5B, the horizontal axis is the shortened length Lc (mm) of the outer end E2 with respect to the outer end E1, and the vertical axis is the angle α (degrees).

  5A and 5B, the lateral width L1 of the first opposing plane 13u of the U phase and the lateral width L1 of the first opposing plane 13w of the W phase are 17 mm, 18 mm, 19 mm, For the four types of current sensors 1 having a diameter of 23 mm, the relationship between the shortened length Lc and the angle α was simulated. The width dimension L2 of the V-phase first opposing plane 13v and the second opposing plane 14v was 17 mm, and the interval δ between the shields adjacent to each other in the U-phase, V-phase, and W-phase was 7.5 mm.

  As shown in FIG. 4A, in the U phase, when the shortened length Lc is small, the magnetic force line M2 passing through the magnetic sensing element 5u is inclined clockwise by the angle α with respect to the element vertical line Sv. The sign of the vertical axis shown in FIG. As the shortened length Lc becomes longer, the angle α becomes smaller. When the shortened length Lc becomes longer, the angle α becomes inclined counterclockwise, and the sign of the vertical axis in FIG. 5A becomes “negative”. .

  As shown in FIG. 5B, in the W phase, when the shortened length Lc is small, the angle α is tilted counterclockwise, so the sign of the vertical axis is “negative”. As the shortened length Lc increases, the angle α decreases. When the shortened length Lc further increases, the angle α tilts clockwise and the sign of the vertical axis becomes “positive”.

  As shown in FIGS. 5A and 5B, when the width dimension L1 of the U-phase first opposing plane 13u and the W-phase first opposing plane 13w is 17 mm, the outer end E2 with respect to the outer end E1 When the shortened length Lc is about 6 mm, the angle α is close to zero, and the current magnetic field induced by the drive current Iv flowing in the V-phase current path 2v is a noise magnetic field in the U-phase magnetic sensing element 5u. Will be almost undetectable. When the width dimension L1 is 18 mm, the U-phase magnetic sensing element 5u is hardly detected as a noise magnetic field when the shortened length Lc is about 5 mm. When the width dimension L1 is 19 mm, the U-phase magnetic sensing element 5u is hardly detected as a noise magnetic field when the shortened length Lc is about 4 mm. Even when the width dimension L1 is 23 mm, the U-phase magnetic sensing element 5u is hardly detected as a noise magnetic field when the shortened length Lc is about 4 mm.

  From the simulation result of FIG. 5A, if the width dimension L1 of the first opposing plane 13u is short, the influence of the shortened length Lc becomes large. If the shortened length Lc is not increased, the drive current Iv of the V-phase current path 2v is increased. It turns out that the influence of the noise magnetic field resulting from this cannot be reduced. This is because when the width dimension L1 of the first opposing plane 13u becomes shorter, the distance from the magnetic sensing element 5u to the outer end E1 of the first opposing plane 13u, and the outer end of the second opposing plane 14u from the magnetic sensing element 5u. This is because the distance to E2 is shortened, and as a result, the bulge in the X1 direction of the magnetic lines of force (M2 in FIG. 4A and Mb in FIG. 4B) passing through the magnetic sensing element 5u increases. . Therefore, in order to reduce the angles α and β with respect to the element vertical line Sv due to the expansion of the magnetic force lines M2 and Mb in the X1 direction, it is necessary to increase the shortened length Lc of the outer end E2 with respect to the outer end E1. Become.

Conversely, when the width L1 of the first opposing plane 13u is long, the distance from the magnetic sensing element 5u to the outer end E1 of the first opposing plane 13u and the outer end of the second opposing plane 14u from the magnetic sensing element 5u. The distance to E2 becomes longer, and the bulges in the X1 direction of the magnetic lines of force M2 and Mb passing through the magnetic sensing element 5u become smaller. Therefore, it is considered that the effect of reducing the angle α of the magnetic lines of force M2 and Mb with respect to the element vertical line Sv can be obtained by slightly changing the shortened length Lc of the outer end E2 with respect to the outer end E1.
This is the same also in the simulation result shown in FIG.

  5A and 5B, the ratio of Lc / L for reducing the influence of the current magnetic field induced by the V-phase drive current Iv acting as a noise magnetic field on the magnetic sensing elements 5u and 5w is the width. Based on an example in which the dimension L1 is 18 mm, it is preferable that Lc / L = 2/18 or more and Lc / L = 8/18 or less, that is, 0.11 or more and 0.44 or less. This numerical range is considered effective when the width L1 is 17 mm or more and 23 mm or less.

  FIG. 6 is a diagram showing the influence of a noise magnetic field induced in adjacent current paths in the current sensor of the first embodiment, and FIG. 7 is induced in adjacent current paths in the current sensor of the second embodiment. FIG. 8 is a diagram showing the influence of the noise magnetic field induced in the adjacent current path in the current sensor of the comparative example.

(First embodiment)
2A, the thickness H1 in the vertical direction (Z direction) of the current paths 2u, 2v, 2w is set to 4 mm, and the horizontal direction of the current paths 2u, 2v, 2w (X Direction) width dimension was 15 mm. The U-phase first shield 11u and the second shield 12u, the V-phase first shield 11v and the second shield 12v, and the W-phase first shield 11w and the second shield 12w are all in the vertical direction (Z direction). The thickness dimension was 1.5 mm.

  The distance H2 in the vertical direction (Z direction) between the surface of the current paths 2u, 2v, 2w facing the Z1 side and the magnetic detection elements 5u, 5v, 5w was 2.5 mm. The distance H3 in the vertical direction (Z direction) between the surface facing the Z1 side of the current paths 2u, 2v, 2w and the first opposing planes 13u, 13v, 13w of the first shields 11u, 11v, 11w is 5 mm, The distance H4 in the vertical direction (Z direction) between the surface facing the Z2 side of the paths 2u, 2v, 2w and the second opposing planes 14u, 14v, 14w of the second shields 12u, 12v, 12w was 2 mm.

  The lateral width L1 of the first opposing plane 13u of the U-phase first shield 11u and the lateral width L1 of the first opposing plane 13w of the W-phase first shield 11w are 18 mm, and the V-phase The width dimension L2 of the first opposing plane 13v and the second opposing plane 14v was 17 mm, and the interval δ between the shields adjacent to each other in the U phase, the V phase, and the W phase was 7.5 mm.

  The shortened length Lc in the X2 direction of the outer end E2 of the second opposing plane 14u with respect to the outer end E1 of the first opposing plane 13u of the U phase is 5 mm, and even in the W phase, the first opposing plane 13w The shortened length Lc in the X1 direction of the outer end E2 of the second opposing plane 14w with respect to the outer end E1 was set to 5 mm. Lc / L is 0.28.

(Second embodiment)
The shortened length Lc in the X2 direction of the outer end E2 of the second opposing plane 14u relative to the outer end E1 of the U-phase first opposing plane 13u is 6 mm, and the outer end of the first opposing plane 13w also in the W phase The shortened length Lc in the X1 direction of the outer end portion E2 of the second opposing plane 14w with respect to the portion E1 was 6 mm. Lc / L is 0.33.
Other dimensions are the same as in the first embodiment.

(Comparative example)
The width dimension of the first opposing plane 13u and the second opposing plane 14u in the U phase was both 18 mm, and the width dimension of the first opposing plane 13w and the second opposing plane 14w in the W phase was both 18 mm. That is, the shortened length Lc was set to zero.
Other dimensions are the same as in the first embodiment.

(Explanation of FIGS. 6, 7 and 8)
FIG. 6 shows the first embodiment, FIG. 7 shows the second embodiment, FIG. 8 shows the comparative example, and the simulation results for each.
In FIGS. 6A, 7A, and 8A, an alternating drive current Iu is supplied only to the U-phase current path 2u, and the drive currents Iv, Iw are supplied to the other current paths 2v, 2w. In a state where no current flows, a change in magnetic flux density detected by the magnetic sensing element 5u facing the current path 2u, and an AC driving current Iv is allowed to flow only in the V-phase current path 2v, and driving currents are transmitted in the other current paths 2u and 2w. Changes in the magnetic flux density detected by the magnetic sensing element 5v facing the current path 2v without flowing Iu and Iw, and an AC drive current Iw is allowed to flow only in the W-phase current path 2w, and the other current paths 2u, A change in magnetic flux density detected by the magnetic detection element 5w opposed to the current path 2w in the state where the drive currents Iu and Iv are not supplied to 2v is shown.

  6A, FIG. 7A, and FIG. 8A, the horizontal axis indicates the measurement reference time (msec), and the vertical axis indicates the magnetic sensing elements 5u, 5v, and 5w, respectively. The detected magnetic flux density (mT) is shown. Changes in magnetic flux density detected by the U-phase magnetic sensing element 5u, changes in magnetic flux density detected by the V-phase magnetic sensing element 5v, and changes in magnetic flux density detected by the W-phase magnetic sensing element 5w 6A, FIG. 7A, and FIG. 8A, the time is plotted in the horizontal axis direction so that the phases are 120 degrees different from each other.

  The simulation results of FIGS. 6B, 7B, and 8B show that the U-phase current path 2u, the V-phase current path 2v, and the W-phase current path 2w are 120 degrees out of phase with each other. This shows the influence of the noise magnetic field induced by the drive current flowing in the adjacent current path on each of the magnetic sensing elements 5u, 5v, 5w when the drive currents Iu, Iv, Iw to be simultaneously flowed. .

  The horizontal axes of FIG. 6B, FIG. 7B, and FIG. 8B indicate elapsed time (msec). The vertical axes of FIGS. 6B, 7B, and 8B simultaneously apply drive currents Iu, Iv, and Iw whose phases are shifted by 120 degrees to the U phase, the V phase, and the W phase, The magnetic flux density measured by each of the magnetic sensing elements 5u, 5v, and 5w is B1, and the magnetic flux density detection outputs of FIGS. 6A, 7A, and 8A, that is, the U phase and the V phase. In addition, the drive currents Iu, Iv, and Iw are individually applied to the W phase, and the magnetic flux density individually detected by each of the magnetic detection elements 5u, 5v, and 5w is B0, and {(B1-B0) / B0} × 100 (%) Is a calculated value.

8A and 8B, the detection output of the U-phase magnetic detection element 5u and the detection output of the W-phase magnetic detection element 5w are induced by the V-phase drive current Iv. It can be seen that the current magnetic field affects the noise magnetic field. For example, at the time (i) shown in FIG. 8, that is, the time of 10 msec, the magnetic flux density detected by the U-phase magnetic detection element 5u shown in FIG. The magnetic flux density of the current magnetic field induced by Iv is about 10 mT, and the V-phase current magnetic field affects the detection output of the U-phase magnetic detection element 5 u as a noise magnetic field of about 1%. I understand.
Further, the V-phase current magnetic field similarly affects the W-phase detection output as a noise magnetic field.

  As for the detection output of the V-phase magnetic detection element 5v shown in FIG. 8B, for example, at time (i), the V-phase drive current Iv and the drive current Iw of the adjacent W-phase drive current Iw. And are in opposite phase. In addition, at time 5 msec and time 15 msec, the V-phase drive current Iv and the adjacent U-phase drive current Iu are in opposite phases. At other times, the U-phase drive current Iu and the W-phase drive current Iw are often in opposite phases. Therefore, the magnetic field is canceled and the magnetic field induced by the U-phase drive current Iu. It is considered that the influence of the current magnetic field induced by the W-phase drive current Iw on the V-phase magnetic sensing element 5v is reduced.

  On the other hand, in the simulation result of the first embodiment shown in FIG. 6B and the simulation result shown in FIG. 7B, all the magnetic detection elements 5u, 5v, 5w of the U phase, the V phase, and the W phase are used. It can be seen that the current magnetic field induced by the adjacent drive current hardly affects the noise magnetic field.

1 current sensors 2u, 2v, 2w current paths 5u, 5v, 5w magnetic sensing elements 11u, 11v, 11w first shields 12u, 12v, 12w second shields 13u, 13v, 13w first opposing planes 14u, 14v, 14w second Opposing plane E1 Outer end E2 of first opposing plane Outer end Iu, Iv, Iw of second opposing plane Drive current Lc Shortening length M1, M2 Magnetic field line Sv Element vertical line

Claims (6)

In a current sensor in which a magnetic sensing element facing each of a plurality of current paths arranged in parallel is provided, and a magnetic field induced by a current flowing in each of the current paths is detected by the magnetic sensing element,
When the direction that crosses all the current paths orthogonally is the horizontal direction, and the direction that is orthogonal to both the current direction and the horizontal direction of the current path is the vertical direction,
The magnetic sensing elements are opposed to the current paths from the vertical direction, and their sensitivity axes are directed in the horizontal direction.
A first shield and a second shield sandwiching both the current path and the magnetic sensing element from both sides in the vertical direction are provided, and the first shield is a plane parallel to both the current direction and the lateral direction. A first opposing plane facing the magnetic sensing element; and the second shield is a plane parallel to both the current direction and the lateral direction and facing the current path. And
Each of the first opposing plane and the second opposing plane has an outer end that faces the outside where the current path does not exist next to the first opposing plane, and the outer end of the second opposing plane is the first A current sensor, wherein the current sensor is located between the outer end portion of the opposing plane and the magnetic sensing element.   The current sensor according to claim 1, wherein a distance between the magnetic sensing element and the first opposing plane is shorter than a distance between the magnetic sensing element and the second opposing plane. The first shield and the second shield are individually provided for each of the current paths,
3. The current sensor according to claim 1, wherein each of the first opposing plane and the second opposing plane includes the outer end portion and an inner end portion directed inward where the current path exists adjacent thereto.   In the first shield and the second shield facing each other, the inner end portion of the first opposing plane and the inner end portion of the second opposing plane are formed at the same position in the vertical direction. 3. The current sensor according to 3. The three current paths are provided, and the first shield and the second shield are opposed to each of the current paths,
In the first shield and the second shield positioned on both sides in the lateral direction, the outer end portion of the second opposing plane is positioned between the outer end portion of the first opposing plane and the magnetic sensing element. The inner end portion of the first opposing plane and the inner end portion of the second opposing plane are formed at the same position in the vertical direction,
In the first shield and the second shield located at the center in the longitudinal direction, both lateral ends of the first opposing plane and lateral ends of the second opposing plane are both longitudinal. The current sensor according to claim 4, wherein the current sensor is formed at the same position. The lateral length dimension of the first opposing plane is L, and the shortened length which is the lateral distance between the outer end portion of the first opposing plane and the outer end portion of the second opposing plane is Lc. When
The current sensor according to claim 3, wherein a ratio of Lc / L is 0.11 or more and 0.44 or less.