Patent Publication Number: US-11644517-B2

Title: Magnetic sensor

Description:
TECHNICAL FIELD 
     The present invention relates to a magnetic sensor and, more particularly, to a magnetic sensor provided with a magnetic member for collecting magnetic flux in a magnetic detection element. 
     BACKGROUND ART 
     A magnetic sensor using a magnetic resistance element is widely used in an ammeter, a magnetic encoder, and the like. The magnetic sensor is sometimes provided with a magnetic member for collecting magnetic flux in a magnetic detection element and, in this case, the magnetic member is disposed offset to the magnetic detection element (see Patent Documents 1 and 2). With this configuration, the direction of the magnetic flux is bent in a magnetism fixing direction by the magnetic member, thereby enabling high-sensitivity detection. 
     CITATION LIST 
     Patent Document 
     [Patent Document 1] Japanese Patent No. 5,500,785 
     [Patent Document 2] JP 2014-182096 A 
     SUMMARY OF INVENTION 
     Technical Problem to be Solved by Invention 
     However, in the magnetic sensor described in Patent Documents 1 and 2, a large part of the magnetic detection element is exposed from the magnetic member, so that the sensor is subject to an environmental magnetic field acting as noise. 
     It is therefore an object of the present invention to provide a magnetic sensor less subject to the environmental magnetic field. 
     Means for Solving Problem 
     A magnetic sensor according to the present invention includes a plurality of magnetic detection elements including at least a first magnetic detection element positioned on a first plane, and a magnetic member provided on a second plane parallel to the first plane. The magnetic member includes a first main body part forming a first space between itself and the second plane and a first leg part protruding from the first main body part and fixed to the second plane, and the first magnetic detection element is covered with the first main body part. 
     According to the present invention, a magnetic field to be detected is collected in the first leg part, and the first magnetic detection element is covered with the first main body part, thereby allowing an environmental magnetic field acting as noise to bypass the first magnetic detection element through the first main body part. Thus, influence of the environmental magnetic field can be reduced. The magnetic member is preferably made of a soft magnetic material. 
     Preferably, in the present invention, the plurality of magnetic detection elements further include a second magnetic detection element covered with the first main body part, the magnetic member further includes a second leg part protruding from the first main body part and fixed to the second plane, the first main body part is positioned between the first and second leg parts, the first magnetic detection element is disposed offset to the first leg part side, and the second magnetic detection element is disposed offset to the second leg part side. This allows magnetic fields collected in the first and second leg parts to be given to the first and second magnetic detection elements, respectively, so that a differential signal can be obtained. In addition, the first and second magnetic detection elements are sandwiched between the first and second leg parts in a plan view and covered with the first main body part, effectively preventing the environmental magnetic field from coming in the first space. Thus, influence of the environmental magnetic field can be reduced further. 
     In this case, the cross-sectional shape of the first space in a direction crossing the first and second planes and first and second leg parts may be polygonal, and the cross section of the bottom surface of the first main body part in a direction crossing the first and second planes and first and second leg parts may have a curved part. 
     Preferably, in the present invention, the plurality of magnetic detection elements further include a second magnetic detection element, the magnetic member further includes a second main body part forming a second space between itself and the second plane, the first leg part is positioned between the first and second main body parts, and the second magnetic detection element is covered with the second main body part. Also in this case, the differential signal can be obtained by the first and second magnetic detection elements. 
     Preferably, in this case, the magnetic member further includes second and third leg parts fixed to the second plane, the first main body part is positioned between the first and second leg parts, the second main body part is positioned between the first and third leg parts, and both the first and second magnetic detection elements are disposed offset to the first leg part side. As a result, the first magnetic detection element is sandwiched between the first and second leg parts in a plan view, and the second magnetic detection element is sandwiched between the first and third leg parts in a plan view, so that influence of the environmental magnetic field can be reduced further. 
     In the present invention, the first magnetic detection element is preferably disposed so as not to overlap the first leg part. This allows a larger number of magnetic field components parallel to the first plane to be applied to the first magnetic detection element. 
     Preferably, in the present invention, a first direction that is parallel to the first and second planes is set as the magnetization fixing direction of the plurality of magnetic detection elements, and the length of the magnetic member in a second direction parallel to the first and second planes and crossing the magnetization fixing direction is greater than the length of each of the plurality of magnetic detection elements in the second direction. This allows a magnetic field parallel to the magnetization fixing direction can be obtained over a wider area in the second direction, thereby making it possible to enhance the magnetic detection sensitivity of the magnetic sensor. 
     In the present invention, the plurality of magnetic detection elements are each preferably covered with the magnetic member. This allows a magnetic field to be detected to be efficiently given to the magnetic detection elements and allows the magnetic detection elements to be effectively shielded from the environmental magnetic field. 
     Advantageous Effects of Invention 
     According to the present invention, there can be provided a magnetic sensor capable of reducing influence of the environmental magnetic field. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 A according to a first embodiment of the present invention. 
         FIG.  2    is a cross-sectional view of the magnetic sensor  10 A. 
         FIG.  3    is a top view of the magnetic sensor  10 A. 
         FIG.  4    is a schematic diagram for explaining a flow of magnetic flux ϕz in the z-direction in the first embodiment. 
         FIG.  5    is a schematic diagram for explaining a flow of magnetic flux ϕx in the x-direction in the first embodiment. 
         FIG.  6    is a circuit diagram for explaining the connection relationship between the magnetic detection elements MR 1  to MR 4 . 
         FIG.  7    is a cross-sectional view of the magnetic sensor  10 A 1  according to a first modification. 
         FIG.  8    is a cross-sectional view of the magnetic sensor  10 A 2  according to a second modification. 
         FIG.  9    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 B according to a second embodiment of the present invention. 
         FIG.  10    is a cross-sectional view of the magnetic sensor  10 B. 
         FIG.  11    is a top view of the magnetic sensor  10 B. 
         FIG.  12    is a schematic diagram for explaining a flow of magnetic flux ϕz in the z-direction in the second embodiment. 
         FIG.  13    is a schematic diagram for explaining a flow of magnetic flux ϕx in the x-direction in the second embodiment. 
         FIG.  14    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 C according to a third embodiment of the present invention. 
         FIG.  15    is a cross-sectional view of the magnetic sensor  10 C. 
         FIG.  16    is a top view of the magnetic sensor  10 C. 
         FIG.  17    is a schematic diagram for explaining a flow of magnetic flux ϕz in the z-direction in the third embodiment. 
         FIG.  18    is a schematic diagram for explaining a flow of magnetic flux ϕx in the x-direction in the third embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will now be explained in detail with reference to the drawings. 
     First Embodiment 
       FIG.  1    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 A according to the first embodiment of the present invention.  FIG.  2    is a cross-sectional view of the magnetic sensor  10 A, and  FIG.  3    is a top view of the magnetic sensor  10 A. In particular,  FIG.  2    illustrates the cross section taken along line A-A of  FIG.  3   . 
     As illustrated in  FIGS.  1  to  3   , the magnetic sensor  10 A according to the present embodiment includes a sensor chip  20 , and a magnetic member  30 A fixed to the sensor chip  20 . 
     The sensor chip  20  has a substrate  21  having a substantially rectangular parallelepiped shape, and four magnetic detection elements MR 1  to MR 4  are formed on an element forming surface  21   a  of the substrate  21 . The element forming surface  21   a  is an xy plane and constitutes a part of a first plane P 1 . The element forming surface  21   a  is covered with an insulating film  22 , and the surface of the insulating film  22  constitutes a second plane P 2  parallel to the first plane P 1 . A common method to produce the sensor chip  20  is to form a large number of sensor chips  20  on an aggregate substrate at a time and then to separate them for taking multiple sensor chips; however, the present invention is not limited to this, and the sensor chips  20  may be individually produced. 
     There is no particular restriction on the type of magnetic detection elements MR 1  to MR 4  as long as physical properties thereof are changed by magnetic flux density. In the present embodiment, a magnetoresistive element (MR element) whose electric resistance is changed in accordance with the direction of a magnetic field is used. The magnetization fixing directions of the magnetic detection elements MR 1  to MR 4  are all aligned in a first direction (positive side in the x-direction) denoted by arrows B in  FIGS.  2  and  3   . 
     The magnetic member  30 A is a block made of a soft magnetic material, such as ferrite, having high permeability and is placed on the second plane P 2 . The magnetic member  30 A has a first main body part  51  and first and second leg parts  41  and  42  protruding from the first main body part  51 . The first leg part  41  is a part fixed to a mounting area  23  positioned on the second plane P 2 , and the second leg part  42  is a part fixed to a mounting area  24  positioned on the second plane P 2 . The first and second leg parts  41  and  42  can be fixed by using an adhesive. The magnetic detection elements MR 1  and MR 3  are disposed on the positive side in the x-direction with respect to the mounting area  23 . Further, the magnetic detection elements MR 2  and MR 4  are disposed on the negative side in the x-direction with respect to the mounting area  24 . 
     The first main body part  51  is positioned between the first leg part  41  and the second leg part  42 , and a bottom surface  51   b  thereof is separated from the second plane P 2  by a predetermined distance H. As a result, a first space  61  is formed between the second plane P 2  and the first main body part  51 . The first main body part  51  covers the magnetic detection elements MR 1  to MR 4  through the first space  61  in a plan view (when viewed in the z-direction). The magnetic detection elements MR 1  and MR 3  are disposed offset to the first leg part  41  side, and the magnetic detection elements MR 2  and MR 4  are disposed offset to the second leg part  42  side. That is, the magnetic detection elements MR 1  and MR 3  are disposed on the negative side in the x-direction with respect to the center of the magnetic member  30 A in the x-direction, and the magnetic detection elements MR 2  and MR 4  are disposed on the positive side in the x-direction with respect to the center of the magnetic member  30 A in the x-direction. The magnetic detection elements MR 1  and MR 3  are arranged in the y-direction that is a second direction, and the magnetic detection elements MR 2  and MR 4  are also arranged in the y-direction. Further, the magnetic detection elements MR 1  and MR 2  are arranged in the x-direction that is a first direction, and the magnetic detection elements MR 3  and MR 4  are also arranged in the x-direction. 
     The magnetic detection elements MR 1  to MR 4  are preferably entirely covered by the first main body part  51 . In other words, the magnetic detection elements MR 1  to MR 4  do not preferably overlap the first leg part  41  or second leg part  42  at all in a plan view. This is because when a part of the magnetic detection element MR 1 , MR 2 , MR 3 , or MR 4  overlaps the first leg part  41  or second leg part  42 , an x-direction component of the magnetic flux given to the magnetic detection element MR 1 , MR 2 , MR 3 , or MR 4  is reduced to degrade detection sensitivity by the reduction. 
     As illustrated in  FIG.  4   , the magnetic member  30 A plays a role of collecting magnetic flux ϕz in the z-direction and distributing half of it to the first leg part  41  and the remaining half to the second leg part  42 . A part of the magnetic flux distributed to the first leg part  41  is bent to the positive side in the x-direction to be applied to the magnetic detection elements MR 1  and MR 3 . A part of the magnetic flux distributed to the second leg part  42  is bent to the negative side in the x-direction to be applied to the magnetic detection elements MR 2  and MR 4 . As a result, the magnetic flux given to the magnetic detection elements MR 1 , MR 3  and the magnetic flux given to the magnetic detection elements MR 2 , MR 4  are mutually in opposite directions. As described above, the magnetization fixing directions of the magnetic detection elements MR 1  to MR 4  are aligned in the positive x-direction denoted by arrows B, so that the magnetic detection elements MR 1  to MR 4  have sensitivity to a magnetic flux component in the x-direction. 
     On the other hand, as illustrated in  FIG.  5   , magnetic flux ϕx in the x-direction is absorbed into the first leg part  41  or second leg part  42  and is led to the first main body part  51 . In the example of  FIG.  5   , the magnetic flux ϕx absorbed into the second leg part  42  is discharged from the first leg part  41  through the first main body part  51 . As a result, the magnetic flux ϕx hardly comes in the first space  61  and, thus, influence that the magnetic flux ϕx has on the magnetic detection elements MR 1  to MR 4  becomes very small. As described above, the magnetic member  30 A has a function of bringing the magnetic flux ϕx in the x-direction away from the magnetic detection elements MR 1  to MR 4 , i.e., causing the magnetic flux ϕx to bypass the magnetic detection elements MR 1  to MR 4 , so that influence of an environmental magnetic field acting as noise is significantly reduced. 
     Assuming that the length of each of the magnetic detection elements MR 1  to MR 4  in the y-direction is w 0  and that the width of the magnetic member  30 A in the y-direction is w 1 , 
     w 0 &lt;w 1  is preferably satisfied. As a result, the magnetic flux bent in the x-direction by the magnetic member  30 A covers a wider area of each of the magnetic detection elements MR 1  to MR 4  in the y-direction. That is, a magnetic field component in the x-direction can be obtained over the wider area in the y-direction, thereby enhancing magnetic detection sensitivity. In addition, a shield effect against an environmental magnetic field acting as noise which is brought about by the magnetic member  30 A becomes wider in the y-direction, influence of the environmental magnetic field is reduced more effectively. 
     There is no particular restriction on the height of the magnetic member  30 A in the z-direction; however, by increasing the height thereof in the z-direction, selectivity of the magnetic flux in the z-direction can be enhanced. In the present embodiment, the magnetic member  30 A has the two leg parts  41  and  42  protruding from the bottom surface thereof, and the leg parts  41  and  42  are fixed to the second plane P 2 , so that even when the height of the magnetic member  30 A in the z-direction is increased, the magnetic member  30 A can be supported comparatively stably. 
       FIG.  6    is a circuit diagram for explaining the connection relationship between the magnetic detection elements MR 1  to MR 4 . 
     In the example of  FIG.  6   , a constant voltage source  71  is used. Between both ends of the constant voltage source  71 , the magnetic detection elements MR 1  and MR 2  are connected in series in this order, and the magnetic detection elements MR 4  and MR 3  are connected in series in this order. A voltage detection circuit  72  is connected between a connection point C 1  located between the magnetic detection elements MR 1  and MR 2  and a connection point C 2  located between the magnetic detection elements MR 4  and MR 3 , whereby the level of an output voltage appearing between the connection points C 1  and C 2  is detected. 
     The magnetic detection elements MR 1  and MR 3  are disposed offset to the first leg part  41  side in a plan view, and the magnetic detection elements MR 2  and MR 4  are disposed offset to the second leg part  42  side in a plan view, so that the magnetic detection elements MR 1  to MR 4  constitute a differential bridge circuit, making it possible to detect at high sensitivity an electric resistance change based on the magnetic flux density in each of the magnetic detection elements MR 1  to MR 4 . 
     Specifically, the magnetic flux ϕz in the z-direction attracted to the magnetic member  30 A is distributed to the mounting areas  23  and  24  of the sensor chip  20  and returned to the source of the magnetic flux after traveling on both sides in the x-direction. At this time, since the magnetic detection elements MR 1  to MR 4  have the same magnetization fixing direction, a difference occurs between the resistance change amounts of the magnetic detection elements MR 1  and MR 3  positioned on the positive side in the x-direction with respect to the mounting area  23  and the resistance change amounts of the magnetic detection elements MR 2  and MR 4  positioned on the negative side in the x-direction with respect to the mounting area  24 . The difference is amplified twofold by the differential bridge circuit illustrated in  FIG.  6    and detected by the voltage detection circuit  72 . 
     As described using  FIG.  5   , in the magnetic sensor  10 A according to the present embodiment, the magnetic flux ϕx in the x-direction which acts as noise passes through the magnetic member  30 A and is hardly applied to the magnetic detection elements MR 1  to MR 4 . That is, the magnetic member  30 A has a shield effect against the magnetic flux ϕx in the x-direction, thus allowing significant reduction in the influence of the environmental magnetic field. 
     Further, the magnetic member  30 A has the leg parts  41  and  42  on both sides thereof in the x-direction in a plan view, while it has no leg part on the both sides in the y-direction in a plan view. The reason for this is as follows. Since the magnetic detection elements MR 1  to MR 4  are elements having sensitivity to the magnetic flux in the x-direction, they need to be disposed adjacent to the leg parts  41  and  42  in the x-direction in a plan view, while when such leg parts are provided on the both sides in the y-direction, the magnetic flux ϕz in the z-direction to be detected flows in the leg parts to reduce a magnetic filed component to be detected. Thus, it is preferable not to provide the leg part on the both sides of the magnetic member  30 A in the y-direction. In other words, the first space  61  is preferably opened on the both sides thereof in the y-direction. 
     While the xz cross section of the first space  61  is rectangular in the above magnetic sensor  10 A, the present invention is not limited to this. For example, like a magnetic sensor  10 A 1  according to a first modification illustrated in  FIG.  7   , it is possible to use a magnetic member  30 A 1  having an inclined bottom surface  51   b  of the first main body part  51  to make the xz cross section of the first space  61  triangular. This provides an advantage that, when a die is used to mold the magnetic member  30 A 1 , the magnetic member  30 A 1  is easily removed from the die. The xz cross section of the first space  61  may have a polygonal shape other than the triangle or rectangle. 
     Further, like a magnetic sensor  10 A 2  according to a second modification illustrated in  FIG.  8   , it is possible to bend the bottom surface  51   b  of the first main body part  51  into a circular arc shape or a bow-like shape to form a curved part. Accordingly, when a die is used to mold the magnetic member  30 A 2 , the magnetic member  30 A 2  is removed from the die more easily. In this case, the entire bottom surface  51   b  may be formed into a curved shape, or a configuration may be possible in which a part of the bottom surface  51   b  is formed into a linear shape, and the remaining part is formed into a curved shape. 
     Second Embodiment 
       FIG.  9    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 B according to the second embodiment of the present invention.  FIG.  10    is a cross-sectional view of the magnetic sensor  10 B, and  FIG.  11    is a top view of the magnetic sensor  10 B. In particular,  FIG.  10    illustrates the cross section taken along line A-A of  FIG.  11   . 
     As illustrated in  FIGS.  9  to  11   , the magnetic sensor  10 B according to the present embodiment differs from the magnetic sensor  10 A according to the first embodiment in that a magnetic member  30 B having a shape different from that of the magnetic member  30 A is used in place of the magnetic member  30 A. Other configurations are the same as those of the magnetic sensor  10 A according to the first embodiment, so the same reference numerals are given to the same elements, and overlapping description will be omitted. 
     The magnetic member  30 B has a first leg part  41  and first and second main body parts  51  and  52 . The first leg part  41  is a part fixed to a mounting area  25  positioned on the second plane P 2  and positioned between the first and second main body parts  51  and  52 . The magnetic detection elements MR 1  and MR 3  are disposed on the negative side in the x-direction with respect to the mounting area  25 , and the magnetic detection elements MR 2  and MR 4  are disposed on the positive side in the x-direction with respect to the mounting area  25 . 
     The first main body part  51  is provided on the positive side in the x-direction of the first leg part  41 , and a bottom surface  51   b  thereof is separated from the second plane P 2  by a predetermined distance H. As a result, a first space  61  is formed between the second plane P 2  and the first main body part  51 . The first main body part  51  covers the magnetic detection elements MR 2  and MR 4  through the first space  61  in a plan view. The magnetic detection elements MR 2  and MR 4  are arranged in the y-direction along the first leg part  41 . 
     The second main body part  52  is provided on the negative side in the x-direction of the first leg part  41 , and a bottom surface  52   b  thereof is separated from the second plane P 2  by a predetermined distance H. As a result, a second space  62  is formed between the second plane P 2  and the second main body part  52 . The second main body part  52  covers the magnetic detection elements MR 1  and MR 3  through the second space  62  in a plan view. The magnetic detection elements MR 1  and MR 3  are arranged in the y-direction along the first leg part  41 . 
     As illustrated in  FIG.  12   , the magnetic member  30 B plays a role of collecting the magnetic flux ϕz in the z-direction in the first leg part  41 , bending a part of the collected magnetic flux ϕz to the negative side in the x-direction to discharge the same to the magnetic detection elements MR 1  and MR 3  side, and bending another part of the collected magnetic flux ϕz to the positive side in the x-direction to discharge the same to the magnetic detection elements MR 2  and MR 4  side. As a result, the magnetic flux given to the magnetic detection elements MR 1 , MR 3  and the magnetic flux given to the magnetic detection elements MR 2 , MR 4  are mutually in opposite directions, allowing the strength of the magnetic flux ϕz in the z-direction to be detected. 
     On the other hand, as illustrated in  FIG.  13   , the magnetic flux ϕx in the x-direction which is a magnetism sensing direction is transmitted from one side of the first and second main body parts  51  and  52  to the other side thereof. As a result, the amount of magnetic flux ϕx to come into the first space  61  and the second space  62  is reduced, so that influence that the magnetic flux ϕx has on the magnetic detection elements MR 1  to MR 4  becomes small. 
     However, unlike the first embodiment, the first and second spaces  61  and  62  are not closed in the x-direction but are each opened at one side in the x-direction, so that the function of causing the magnetic flux ϕx in the x-direction to bypass the magnetic detection elements MR 1  to MR 4  is slightly reduced. However, in the present embodiment, the size of the magnetic member  30 B in the x-direction is advantageously easily reduced. Further, the magnetic member  30 B collects the magnetic flux ϕz in the z-direction in the first leg part  41 , so that a signal level to be obtained is advantageously higher than that in the first embodiment. 
     Third Embodiment 
       FIG.  14    is a schematic perspective view illustrating the outer appearance of a magnetic sensor  10 C according to the third embodiment of the present invention.  FIG.  15    is a cross-sectional view of the magnetic sensor  10 C, and  FIG.  16    is a top view of the magnetic sensor  10 C. In particular,  FIG.  15    illustrates the cross section taken along line A-A of  FIG.  16   . 
     As illustrated in  FIGS.  14  to  16   , the magnetic sensor  10 C according to the present embodiment differs from the magnetic sensors  10 A and  10 B according to the first and second embodiments in that a magnetic member  30 C having a different shape from those of the magnetic members  30 A and  30 B is used in place of the magnetic members  30 A and  30 B. Other configurations are the same as those of the magnetic sensors  10 A and  10 B according to the first and second embodiments, so the same reference numerals are given to the same elements, and overlapping description will be omitted. 
     The magnetic member  30 C has first to third leg parts  41  to  43  and first and second main body parts  51  and  52 . The first to third leg parts  41  to  43  are parts fixed respectively to mounting areas  25  to  27  positioned on the second plane P 2 . The magnetic detection elements MR 1  and MR 3  are disposed on the negative side in the x-direction with respect to the mounting area  25 , and the magnetic detection elements MR 2  and MR 4  are disposed on the positive side in the x-direction with respect to the mounting area  25 . 
     The first main body part  51  is positioned between the first and second leg parts  41  and  42 , and a bottom surface  51   b  thereof is separated from the second plane P 2  by a predetermined distance H. As a result, a first space  61  is formed between the second plane P 2  and the first main body part  51 . The first main body part  51  covers the magnetic detection elements MR 2  and MR 4  through the first space  61  in a plan view. The magnetic detection elements MR 2  and MR 4  are arranged in the y-direction along the first leg part  41 . 
     The second main body part  52  is positioned between the first and third leg parts  41  and  43 , and a bottom surface  52   b  thereof is separated from the second plane P 2  by a predetermined distance H. As a result, a second space  62  is formed between the second plane P 2  and the second main body part  52 . The second main body part  52  covers the magnetic detection elements MR 1  and MR 3  through the second space  62  in a plan view. The magnetic detection elements MR 1  and MR 3  are arranged in the y-direction along the first leg part  41 . 
     As illustrated in  FIG.  17   , the magnetic member  30 C collects the magnetic flux ϕz in the z-direction and leads a part of the collected magnetic flux ϕz to the first leg part  41 . A part of the magnetic flux passing through the first leg part  41  is bent to the negative side in the x-direction to be discharged to the magnetic detection elements MR 1  and MR 3  side, and another part of the magnetic flux passing through the first leg part  41  is bent to the positive side in the x-direction to be discharged to the magnetic detection elements MR 2  and MR 4  side. As a result, the magnetic flux given to the magnetic detection elements MR 1 , MR 3  and the magnetic flux given to the magnetic detection elements MR 2 , MR 4  are mutually in opposite directions, allowing the strength of the magnetic flux ϕz in the z-direction to be detected. 
     On the other hand, as illustrated in  FIG.  18   , the magnetic flux ϕx in the x-direction which is a magnetism sensing direction is absorbed into the first leg part  41  or third leg part  43  and is led to the first main body part  51  or second main body part  52 . In the example of  FIG.  18   , the magnetic flux ϕx absorbed into the second leg part  42  is discharged from the third leg part  43  through the first main body part  51 , first leg part  41  and second main body part  52 . As a result, the magnetic flux ϕx hardly comes into the first and second spaces  61  and  62  and, thus, influence that the magnetic flux ϕx has on the magnetic detection elements MR 1  to MR 4  becomes very small. As described above, the magnetic member  30 C has a function of bringing the magnetic flux ϕx in the x-direction away from the magnetic detection elements MR 1  to MR 4 , i.e., causing the magnetic flux ϕx to bypass the magnetic detection elements MR 1  to MR 4 , so that influence of an environmental magnetic field acting as noise is significantly reduced. 
     It is apparent that the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention. 
     For example, while the four magnetoresistive elements (MR elements) are used as the magnetic detection element in the above embodiments, the type and number of the magnetic detection elements are not particularly limited. 
     Further, while the z-direction position of the first plane P 1  on which the magnetic detection elements MR 1  to MR 4  are formed and the z-direction position of the second plane P 2  to which the magnetic member  30 A,  30 B, or  30 C is fixed differ from each other in the above embodiments, the first and second planes may be set in the same plane. That is, the magnetic member  30 A,  30 B, or  30 C may be fixed to the first plane P 1 . 
     Further, the first and second spaces  61  and  62  each may not necessarily be completely hollow, but a nonmagnetic member may be filled in each of the first and second spaces  61  and  62 . 
     REFERENCE SIGNS LIST 
     
         
           10 A- 10 C,  10 A 1 ,  10 A 2  magnetic sensor 
           20  sensor chip 
           21  substrate 
           21   a  element forming surface 
           22  insulating film 
           23 - 27  mounting area 
           30 A- 30 C,  30 A 1 ,  30 A 2  magnetic member 
           41  first leg part 
           42  second leg part 
           43  third leg part 
           51  first main body part 
           51   b  bottom surface of first main body part 
           52  second main body part 
           52   b  bottom surface of second main body part 
           61  first space 
           62  second space 
           71  constant voltage source 
           72  voltage detection circuit 
         C 1 , C 2  connection point 
         MR 1 -MR 4  magnetic detection element 
         P 1  first plane 
         P 2  second plane 
         ϕx magnetic flux in x-direction 
         ϕz magnetic flux in z-direction