Patent Publication Number: US-2022229094-A1

Title: Magnetic sensor and current detecting apparatus including the same

Description:
CLAIM OF PRIORITY 
     This application is a Continuation of International Application No. PCT/JP2020/037911 filed on Oct. 6, 2020, which claims benefit of priority to Japanese Patent Application No. 2019-185174 filed on Oct. 8, 2019. The entire contents of each application noted above are hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a magnetic sensor capable of measuring a current flowing through a bus bar and to a current detecting apparatus including the magnetic sensor. 
     2. Description of the Related Art 
     A current sensor disclosed in Japanese Unexamined Patent Application Publication No. 2014-98633 includes a U-shaped current path, a magnetoelectric transducer that detects a magnetic field generated when a current flows through the current path, an internal magnetic shield surrounding at least part of the U-shape and the magnetoelectric transducer, and an external magnetic shield surrounding at least part of the internal magnetic shield. The magnetoelectric transducer is disposed at a center within a plane of a tabular current path as viewed along the normal to the current path. 
     However, the configuration in which the magnetoelectric transducer is disposed in the current path, like the current sensor disclosed in Japanese Unexamined Patent Application Publication No. 2014-98633, can cause noise generated from the current path at ON-OFF switching of a voltage for controlling the current to enter through an output terminal or a supply terminal of the magnetoelectric transducer to affect the result of magnetoelectric conversion. 
     SUMMARY 
     The present disclosure provides a magnetic sensor capable of measuring a current flowing through a bus bar and a current detecting apparatus including the magnetic sensor and the bus bar, in which, even if noise is generated from the bus bar at ON-OFF switching of a voltage for controlling the current to be measured flowing through the bus bar, the influence on the detection result can be reduced. 
     A magnetic sensor according a first aspect of the present disclosure includes a main body having two opposing sides, the main body being capable of measuring a value of a current to be measured flowing through a bus bar by detecting a magnetic field induced by the current to be measured, wherein a signal terminal for outputting a detection signal and a supply terminal for supplying electrical power to the main body extend only from one of the two sides of the main body. 
     Thus, by disposing one side on which the signal terminal and the supply terminal are provided away from the bus bar, even if noise is generated from the bus bar at ON-OFF switching of the voltage for controlling the current to be measured flowing through the bus bar, the influence on the detection result can be reduced. 
     A current detecting apparatus according to a second aspect of the present disclosure includes a plate-like bus bar and a magnetic sensor including a main body capable of measuring a current flowing through the bus bar, wherein a signal terminal for outputting a detection signal and a supply terminal for supplying electric power to the main body extend from the main body, wherein the main body includes a portion overlapping the bus bar and a portion not overlapping the bus bar as viewed along a thickness direction of the bus bar, and wherein the signal terminal and the supply terminal extend from the portion of the main body not overlapping the bus bar without overlapping the bus bar. 
     This allows the signal terminal and the supply terminal to be disposed not overlapping the bus bar as viewed along the thickness of the bus bar, allows being distant from the bus bar. For this reason, even if noise is generated from the bus bar at ON-OFF switching of the voltage for controlling the current to be measured flowing through the bus bar, the influence on the detection result can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a current detecting apparatus according to an embodiment of the present disclosure, illustrating the basic configuration thereof; 
         FIG. 1B  is an exploded perspective view of the current detecting apparatus; 
         FIG. 2A  is a cross-sectional view taken along line IIA-IIA of  FIG. 1A ; 
         FIG. 2B  is a cross-sectional view taken along line IIB-IIB of  FIG. 1A ; 
         FIG. 3A  is a diagram showing the positional relationship between a bus bar and a magnetic sensor in a first embodiment; 
         FIG. 3B  is a diagram showing the positional relationship between the bus bar and the magnetic sensor in the first embodiment; 
         FIG. 4A  is a diagram illustrating the positional relationship between a bus bar and a magnetic sensor in a second embodiment; 
         FIG. 4B  is a diagram illustrating the positional relationship between the bus bar and the magnetic sensor in the second embodiment; 
         FIG. 5  is a side view of a current detecting apparatus of a modification of the second embodiment, illustrating the layout of two shields, a magnetic sensor, and a bus bar; and 
         FIG. 6  is a plan view of a bus bar, a magnetic sensor, and a circuit board of a third embodiment, showing the positional relationship among them. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Magnetic sensors and current detecting apparatuses according to embodiments of the present disclosure will be described in detail hereinbelow with reference to the drawings. 
     First, the basic configuration of a current detecting apparatus  10  according to an embodiment will be described with reference to  FIGS. 1A and 1B  and  FIGS. 2A and 2B . The sizes and relative positions of the individual members will be described for each embodiment with reference to  FIGS. 3A to 6 .  FIG. 1A  is a perspective view of the current detecting apparatus  10  illustrating the basic configuration thereof,  FIG. 1B  is an exploded perspective view of the current detecting apparatus  10 ,  FIG. 2A  is a cross-sectional view taken along line IIA-IIA of  FIG. 1A , and  FIG. 2B  is a cross-sectional view taken along line IIB-IIB of  FIG. 1A . 
     As shown in  FIGS. 1A and 1B , the current detecting apparatus  10  includes a substantially rectangular parallelepiped casing  11  in which a cover  11   a  on the upper side (the Z1 side in  FIGS. 1A and 1B ) and a case member  11   b  on the lower side (the Z2 side in  FIGS. 1A and 1B ) are fixed to each other. Three bus bars  21 ,  22 , and  23  pass through the case member  11   b  along the width of the casing  11  (in the Y1-Y2 direction in  FIGS. 1A and 1B ). 
     The three bus bars  21 ,  22 , and  23  are electrically conductive plates with the same shape, which are arranged so that the two opposing surfaces correspond to each other in the vertical direction of the casing  11 . The bus bars  21 ,  22 , and  23  extend linearly along the width of the casing  11  and are disposed at regular intervals along the length of the casing  11  (in the X1-X2 direction of  FIGS. 1A and 1B ). 
     As shown in  FIGS. 1B and 2B , a circuit board  30  is disposed in the casing  11  so as to extend in the longitudinal direction (X1-X2 direction), and magnetic sensors  31 ,  32 , and  33  are disposed at the positions corresponding to the bus bars  21 ,  22 , and  23  in an X-Y plane (a plane including the X1-X2 direction and the Y1-Y2 direction) on the circuit board  30 . At least part of the main body of each of the magnetic sensors  31 ,  32 , and  33  faces the corresponding bus bar in the vertical direction. 
     The magnetic sensors  31 ,  32 , and  33  may be disposed either the upper surface or the lower surface of the circuit board  30 . However, the magnetic sensors  31 ,  32 , and  33  are desirably disposed on the same surface. 
     For example, the magnetic sensor  32  is disposed at the center of the casing  11  in the width direction (Y1-Y2 direction), and the bus bar  22  and the magnetic sensor  32  face each other in the vertical direction, as shown in  FIG. 2A . The position of the magnetic sensor  32  in the width direction (X1-X2 direction) of the bus bar  22  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B  are given as an example only, and specific examples are shown in the individual embodiments. Disposing the magnetic sensor  32  in correspondence with the bus bar  22  allows the magnetic sensor  32  to measure the value of a current flowing through the bus bar  22  (the current to be measured) by detecting a magnetic field induced by the current. An example of the magnetic sensor  32  is a magnetoresistive sensor, such as a giant magnetoresistive sensor (GMR sensor). 
     The magnetic sensor  32  is sandwiched between a first shield  41   a  disposed in the cover  11   a  and a second shield  41   b  disposed in the case member  11   b  from above and below. The first shield  41   a  and the second shield  41   b  are preferably made of a ferromagnetic substance as a magnetic shield made of a magnetic material and are disposed parallel to each other so as to face each other in the vertical direction. Each of the first shield  41   a  and the second shield  41   b  has a configuration in which a plurality of metal plates with the same rectangular shape in plan view and the same size are vertically laminated, and has substantially the same length as that of the circuit board  30  in the width direction (Y1-Y2 direction), as shown in  FIG. 2A , and a size so as to cover the bus bar  22  in the longitudinal direction (X1-X2 direction). Furthermore, the first shield  41   a  and the second shield  41   b  are aligned so as not to extend off from each other as viewed along the thickness of the bus bar  22 . Disposing the first shield  41   a  and the second shield  41   b  so as to sandwich the magnetic sensor  32  allows the magnetic sensor  32  to be shielded from an extraneous magnetic field (external magnetic field), such as a magnetic field induced by a current flowing through the adjacent bus bars  21  and  23 , thereby reducing the influence thereof. 
     The layout of the magnetic sensor  32  relative to the bus bar  22 , the layout of the two shields  41   a  and  41   b  relative to the magnetic sensor  32 , and the operation and advantages of the layout apply also to the two magnetic sensors  31  and  33  on both sides of the magnetic sensor  32 . The two shields  41   a  and  41   b  may be omitted in a case where the influence of the extraneous magnetic field is small. 
       FIGS. 3A and 3B  are diagrams showing the positional relationship between a bus bar  120  and a magnetic sensor  130  in a first embodiment, in which  FIG. 3A  is a side view, and  FIG. 3B  is a plan view.  FIGS. 3A and 3B  illustrate the shapes of the bus bar  120  and the magnetic sensor  130  in a simplified manner. 
     In the first embodiment, as shown in  FIGS. 3A and 3B , the bus bar  120  and the magnetic sensor  130  with the size relationship as described below are arranged in the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , and the magnetic sensor  130  includes terminals as will be described later. The other configuration is the same as that of the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , in which a plurality of bus bars  120  made of the same material and having the same shape as those of the bus bars  21 ,  22 , and  23  passes through the casing  11 , a plurality of magnetic sensors  130  is disposed on the circuit board  30  in the casing  11  so as to correspond to the individual bus bars  120 , and the plurality of magnetic sensors  130  are sandwiched between the two vertically opposing shields  41   a  and  41   b.    
     As shown in  FIGS. 3A and 3B , the bus bar  120  is a plate-like member extending linearly along the width of the casing  11  (in the Y1-Y2 direction, see  FIG. 2A ) and having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars  21 ,  22 , and  23  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B . 
     As shown in  FIG. 3B , the magnetic sensor  130  includes a main body  131  having a substantially rectangular shape in plan view viewed along the vertical direction (Z1-Z2 direction) and having thickness in the vertical direction and a plurality of terminals  132   a  and  132   b  extending outward from the sides of the main body  131  (end faces in the width direction of the bus bar  120 ). The main body  131  detects a magnetic field induced by a current (a current to be measured) flowing through the bus bar  120  facing it to measure the value of the current to be measured and outputs the current value as a detection signal. Both of the magnetic sensor  130  and the bus bar  120  have thickness in the vertical direction. In the following description, the plan view refers to a view seen along the thickness thereof. 
     The main body  131  may include a first area  131   a  which overlaps the bus bar  120 , and a second area  131   b  and a third area  131   c,  which do not overlap the bus bar  120 , in plan view seen along the thickness direction. More specifically, the main body  131  may include the first area  131   a  in the center and the second area  131   b  and the third area  131   c,  on both sides, which lie out of the bus bar  120 , along the width of the bus bar  120  (X1-X2 direction). 
     The plurality of terminals  132   a  extends outward from a side of the second area  131   b  (the left in  FIG. 3B ) along the width of the bus bar  120 , and the plurality of terminals  132   b  extends outward from a side of the third area  131   c  (the right in  FIG. 3B ) along the width of the bus bar  120 . Thus, the plurality of terminals  132   a  and  132   b  extend without overlapping the bus bar  120  in plan view. 
     The plurality of terminals  132   a  and  132   b  includes a signal terminal for outputting a detection signal detected by the main body  131  and a supply terminal for supplying electrical power to the main body  131 , and in addition to these terminals, a terminal for correcting the detection signal before shipment, for example. 
     All of the terminals  132   a  and  132   b  including the signal terminal and the supply terminal extend outward from the second area  131   b  and the third area  131   c  of the main body  131 , which do not overlap the bus bar  120  in plan view, respectively, without overlapping the bus bar  120 . Thus, all of the terminals  132   a  and  132   b  do not face the bus bar  120  in the thickness direction, which allows the terminals  132   a  and  132   b  to be distant from the bus bar  120  as compared with a case in which the terminals  132   a  and  132   b  face the bus bar  120 . This reduces the influence of noise generated from the bus bar  120  at the start or stop of application of a current to the bus bar  120 , that is, at ON-Off switching of a voltage for controlling the current to be measured flowing through the bus bar  120 . For example, this reduces the influence of noise entering the signal terminal on the components on the circuit board  30  which are electrically connected to the signal terminal. 
     The circuit board  30  on which the magnetic sensor  130  is disposed may be sandwiched between the two vertically opposing shields  41   a  and  41   b,  as shown in  FIGS. 2A and 2B . This causes the magnetic sensor  130  on the circuit board  30  to be sandwiched between the first shield  41   a  and the second shield  41   b  from above and below, which blocks an extraneous magnetic field, such as a magnetic field induced by a current flowing through adjacent bus bars, reducing the influence thereof. 
       FIGS. 4A and 4B  are diagrams illustrating the positional relationship between a bus bar  220  and a magnetic sensor  230  of a second embodiment, in which  FIG. 4A  is a side view and  FIG. 4B  is a plan view.  FIGS. 4A and 4B  illustrate the shapes of the bus bar  220  and the magnetic sensor  230  in a simplified manner. 
     In the second embodiment, as shown in  FIGS. 4A and 4B , the bus bar  220  and the magnetic sensor  230  with the size relationship as described below are arranged in the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , and the magnetic sensor  230  includes terminals as will be described later. The other configuration is the same as that of the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , in which a plurality of bus bars  220  made of the same material and having the same shape as those of the bus bars  21 ,  22 , and  23  passes through the casing  11 , a plurality of magnetic sensors  230  is disposed on the circuit board  30  in the casing  11  so as to correspond to the individual bus bars  220 , and the plurality of magnetic sensors  230  are sandwiched between the two vertically opposing shields  41   a  and  41   b.    
     As shown in  FIGS. 4A and 4B , the bus bar  220  is a plate-like member extending linearly along the width of the casing  11  (in the Y1-Y2 direction) and having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars  21 ,  22 , and  23  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B . 
     As shown in  FIG. 4B , the magnetic sensor  230  includes a main body  231  having a substantially rectangular shape in plan view viewed along the vertical direction (Z1-Z2 direction) and having thickness in the vertical direction and a plurality of terminals  232   a  and  232   b  extending outward from the sides  231   as  and  231   bs  of the main body  231  opposing each other in the X1-X2 direction, respectively. The main body  231  detects a magnetic field induced by a current (a current to be measured) flowing through the bus bar  220  facing it to measure the value of the current to be measured and outputs the current value as a detection signal. Both of the magnetic sensor  230  and the bus bar  220  have thickness in the vertical direction. In the following description, the plan view refers to a view seen along the thickness thereof. 
     The main body  231  may include a first area  231   a  which overlaps the bus bar  220  and a second area  231   b  which does not overlap the bus bar  220 , in plan view seen along the thickness direction. 
     The plurality of terminals  232   a  individually extends outward from the side  231   as  of the first area  231   a  along the width of the bus bar  220 . The plurality of terminals  232   a  extends over the bus bar  220  in plan view. In contrast, the plurality of terminals  232   b  extends outward from the side  231   bs  of the second area  231   b  along the width of the bus bar  220 . The plurality of terminals  232   b  extends without overlapping the bus bar  220  in plan view. In other words, the plurality of terminals  232   b  extends in a direction distancing away from the bus bar  220 . 
     The plurality of terminals  232   b  extending from the second area  231   b  may include a signal terminal for outputting a detection signal detected by the main body  231  and a supply terminal for supplying electrical power to the main body  231 . The signal terminal and the supply terminal are not included in the plurality of terminals  232   a  extending from the first area  231   a.  In other words, the signal terminal and the supply terminal may extend from only the side  231   bs  of the two opposing sides  231   as  and  231   bs  of the main body  231 , which does not overlap the bus bar  220  in plan view, in the direction perpendicular to the extending direction of the bus bar  220 . Another terminal other than the signal terminal and the supply terminal, for example, a terminal for correcting the detection signal before shipment, may be extended from either of the sides  231   as  and  231   bs.    
     The plurality of terminals  232   b  including the signal terminal and the supply terminal extends outward from the second area  231   b  of the main body  231 , which does not overlap the bus bar  220  in plan view, without overlapping the bus bar  220 . Thus, the terminals  232   b  do not face the bus bar  220  in the thickness direction, which allows the terminals  232   b  to be distant from the bus bar  220  as compared with a case in which the terminals  232   b  face the bus bar  220 . This reduces the influence of noise generated from the bus bar  220  at ON-Off switching of a voltage for controlling the current to be measured flowing through the bus bar  220 , for example, the influence of noise entering the signal terminal on the components on the circuit board  30  which are electrically connected to the signal terminal. 
     Furthermore, the signal terminal and the supply terminal are provided only on the side  231   bs  of the two opposing sides  231   as  and  231   bs  of the main body  231 . This configuration allows the bus bar  220  to be provided in the area facing the first area  231   a  and from the area in the direction distancing away from the plurality of terminals  232   b  (X2 direction) while keeping the effect of reducing the influence of noise generated from the bus bar  220 . 
     The circuit board  30  on which the magnetic sensor  230  is disposed is sandwiched between the two vertically opposing shields  41   a  and  41   b,  as shown in  FIGS. 2A and 2B . This causes the magnetic sensor  230  on the circuit board  30  to be sandwiched between the first shield  41   a  and the second shield  41   b  from above and below, which blocks an extraneous magnetic field, such as a magnetic field induced by a current flowing through adjacent bus bars, reducing the influence thereof. 
       FIG. 5  is a side view of a current detecting apparatus of a modification of the second embodiment, illustrating the layout of the two shields  41   a  and  41   b,  the magnetic sensor  230 , and the bus bar  220  in a simplified manner. The first area  231   a  and the second area  231   b  of the main body  231  of the magnetic sensor  230  may have any size in the width direction of the bus bar  220  (X1-X2 direction). However, disposing the main body  231  so that a plane center  233  is positioned on a widthwise end face  221  of the bus bar  220  so as to be aligned with a plane center  40   x  common to the two shields  41   a  and  42   b,  as shown in  FIG. 5 , provides a well-balanced effect of reliable reduction of the influence of an extraneous magnetic field and accurate measurement of a current value based on a magnetic field induced by the current flowing through the bus bar  220 . 
       FIG. 6  is a plan view of a bus bar  320 , a magnetic sensor  330 , and a circuit board  30  of a third embodiment, showing the positional relationship among them. In  FIG. 6 , the shapes of the bus bar  320 , the magnetic sensor  330 , and the circuit board  30  are illustrated in a simplified manner, and components on the circuit board  30  other than the magnetic sensor  330  are omitted. 
     In the third embodiment, as shown in  FIG. 6 , the bus bar  320  and the magnetic sensor  330  with the size relationship as described below are arranged in the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , and the magnetic sensor  330  includes terminals as will be described later. The bus bar  320  includes a base  321  and two extension ends  322  and  323 . The other configuration is the same as that of the current detecting apparatus  10  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B , in which a plurality of bus bars  320  made of the same material and having the same shape as those of the bus bars  21 ,  22 , and  23  passes through the casing  11 , a plurality of magnetic sensors  330  is disposed on the circuit board  30  in the casing  11  so as to correspond to the individual bus bars  320 , and the plurality of magnetic sensors  330  are sandwiched between the two vertically opposing shields  41   a  and  41   b.    
     As shown in  FIG. 6 , the bus bar  320  may include the base  321  extending linearly along the width of the circuit board  30  (Y1-Y2 direction) and the two extension ends  322  and  323  extending linearly from the opposite ends of the base  321  in the extending direction (Y1-Y2 direction) to the X1 side along the extending direction of the circuit board  30  (X1-X2 direction). The base  321  extends in the direction perpendicular to the extending direction of the circuit board  30  and overlaps a first area  331   a,  which is part of the main body  331  of the magnetic sensor  330 . The two extension ends  322  and  323  may extend, on the opposite longitudinal sides  2  of the base  321 , in a direction different from the extending direction of the base  321  of the bus bar  320  and perpendicular to the extending direction. The bus bar  320  is a plate-like member having thickness in the vertical direction (Z1-Z2 direction) and is made of the same material as that of the bus bars  21 ,  22 , and  23  shown in  FIGS. 1A and 1B  and  FIGS. 2A and 2B . 
     The extension ends  322  and  323  may extend in a direction not perpendicular to the extending direction of the base  321  of the bus bar  320 , provided that it is different from the extending direction of the base  321  of the bus bar  320  and not approaching the main body  331 . The extension ends may be extended not only to the X1 side, like the extension ends  322  and  323 , but also to the X2 side. In other words, the direction not approaching the main body  331  is, for the extension end  322 , the range from the Y2 direction to the X1 direction shown in  FIG. 6  in the clockwise direction, and for the extension end  323 , the range from the X1 direction to the Y1 direction shown in  FIG. 6  in the clockwise direction. If the distance from the main body  331  is fixed or increases, the extension ends  322  and  323  do not need to have a belt shape along a fixed direction, for example, a rectangular shape having four sides in the X1-X2 direction and the Y1-Y2 direction. 
     The magnetic sensor  330  has the same shape and function as that of the magnetic sensor  230  of the second embodiment. The magnetic sensor  330  includes the main body  331  having a substantially rectangular shape with thickness in the vertical direction and a plurality of terminals  332   a  and  332   b  extending outward from the opposing sides of the main body  331  in the X1-X2 direction, respectively. The main body  331  includes a first area  331   a  which overlaps the base  321  of the bus bar  320  and a second area  331   b  which does not overlap the base  321  of the bus bar  320 , in plan view seen along the thickness direction. 
     The plurality of terminals  332   a  and  332   b  are arranged as are the plurality of terminals  232   a  and  232   b  of the second embodiment. The terminals  332   a  extend outward over the base  321  of the bus bar  320 , and the terminals  332   b  extend outward without overlapping the base  321  of the bus bar  320 . As in the second embodiment, the terminals  332   b  extending from the second area  331   b  include a signal terminal for outputting a detection signal detected by the main body  331  and a supply terminal for supplying electric power to the main body  331 . The signal terminal and the supply terminal are not included in the terminals  332   a  extending from the first area  331   a.    
     Disposing the extension ends  322  and  323  increases the area of the entire bus bar  320  to decrease the resistance of the entire bus bar  320 , thereby reducing heat generation while maintaining the effect of reducing the influence of noise generated from the bus bar  320 . 
     The other operations, effects, and modifications are similar to those of the second embodiment. 
     Having described the present disclosure with reference to the embodiments, it is to be understood that the present disclosure is not limited to the embodiments and modifications and changes may be made within the scope of the object of the modifications and the spirit of the present disclosure. 
     The magnetic sensors and current detecting apparatuses including the same according to embodiments of the present disclosure are useful in reducing the influence of noise, which can be generated from the bus bar at ON-OFF switching of a voltage for controlling the current to be measured flowing through the bus bar, on the result of measurement made by the magnetic sensors.