Abstract:
The present invention relates to a magnetic sensor which can improve the detection precision of a weak magnetic field. A magnetic sensor wherein a magnetic body which changes the direction of a magnetic field input to a magnetoresistance effect element is provided in the vicinity of the magnetoresistance effect element in which the resistance value changes according to the direction of the input magnetic field, and the magnetic body has a recess with a concave shape on the surface at a side where the magnetoresistance effect element is formed. The center of the recess may be substantially identical to that of the magnetic body. The concave shape may at least include polygon having three or more sides, or may at least include arc.

Description:
[0001]    The present invention relates to a magnetic sensor, especially a magnetic sensor utilizing a magnetoresistance effect element. 
       BACKGROUND 
       [0002]    A magnetic sensor capable of detecting the change of the magnetic field is developed as a measuring device and used in various applications such as the galvanometer, the magnetic encoder and the like. One example of such a magnetic sensor is disclosed in the following Patent Document 1 in which a GMR element (Giant Magneto Resistive element) is used as the element for detecting the change of the magnetic field. The GMR element is a kind of element in which the output resistance value changes according to the input magnetic field, and the change of the magnetic field to be detected can be measured based on the output resistance value. 
         [0003]    As one example showing the specific configuration of the magnetic sensor where the GMR element is used, as described in Patent Document 1, four GMR elements are provided in the substrate to form a bridge circuit. As such, the change of the resistance value in the GMR element is detected by detecting the differential voltage in the bridge circuit, wherein the change of the resistance value in the GMR element is with the change of the magnetic field which becomes a detection object. In this respect, a sensor that is highly sensitive to the change of magnetic field has been provided. 
         [0004]    In particular, as an element to detect the change of magnetic field, a GMR chip (the chip for detecting magnetic field) is provided in the magnetic sensor as disclosed in Patent Document 1, wherein the GMR chip utilizes the spin valve typed GMR elements (Giant Magneto Resistive element) in which the output resistance value changes depending on the direction of the input magnetic field. As such, each GMR element is magnetized fixedly in a specific direction in one surface so as to detect the magnetic field in the specified direction. Here, in order to downsize the GMR chip and also to lower the deviation in each resistance value, four GMR elements which have already formed the bridge circuit are provided on one GMR chip. Thus, all four GMR elements are magnetized fixedly in the same direction. 
         [0005]      FIG. 1  and  FIG. 2  illustrate the characteristic of the GMR element. First of all, the characteristic of the GMR element used in the present invention will be described with reference to  FIG. 1  and  FIG. 2 . The GMR element is the GMR element (Giant Magneto Resistive element) made in the spin valve type in which output resistance value changes depending on the direction of the input magnetic field. As such, in  FIG. 1  and  FIG. 2 , the relationship between the approach angle and the resistance value is shown, wherein the approach angle refers to the angle of magnetic field H relative to the GMR element. 
         [0006]    In the example as shown in  FIG. 1 , GMR elements are formed on the upper surface of GMR chip  1 . The GMR elements are arranged in such a manner that they are magnetized fixedly in the direction indicated by arrow A. Thus, the magnetic field in the direction as indicated by arrow A can be detected. 
         [0007]    In  FIG. 1 , the GMR elements are arranged in magnetic field H that enters in the direction perpendicular to the form surface of the GMR elements. In this respect, the resistance value of the GMR element turns to “R 0 ” as shown in  FIG. 2 . In contrast, if the direction of magnetic field inclines, the incidence angle of magnetic field H relative to the GMR element surface deviates from the perpendicular direction with an angle of i.e., −Δθ or +Δθ, as shown in  FIG. 1  with dotted lines, wherein Δ(Delta) refers to the variation. In this way, the GMR element is magnetized fixedly in one direction and the resistance value of the GMR element changes when the direction of the magnetic field changes with respect to said direction, as shown in  FIG. 2 . As such, the GMR element has the following characteristic. If the resistance value is defined as R 0  when the magnetic field enters in a perpendicular direction, the resistance value will have substantial change when the direction of the magnetic field H inclines with a tiny angle. 
         [0008]      FIG. 3  and  FIG. 4  show the configuration of the conventional magnetic sensor. When the magnetic field in one direction is detected by using a GMR chip where the bridge circuit as described above has been formed, magnetic body  21  which changes the direction of the magnetic field input to the GMR element is provided in the vicinity of the element forming part where the GMR elements in pair that are adjacent but not connected to each other in the bridge circuit are provided at almost symmetrical positions, as described in Patent Document 1. 
         [0009]    Further, magnetic body  21  can change the external magnetic field in one direction into a different direction between the GMR elements. In this way, four GMR elements inside the bridge circuit are provided in such a manner that the magnetic field comes out in the direction in which the magnetization is fixed relative to one and comes out in the opposite direction relative to another one. As such, a high differential voltage is output from the bridge circuit, and the magnetic field in one direction can be detected in precision. 
         [0010]      FIG. 5  is a schematic view showing the magnetic field H introduced to the GMR element parts  11  and  12  through magnetic body  21  as described in Patent Document 1. The magnetic field bends due to magnetic body  21 , and the component of the magnetic field is generated in the GMR element parts  11  and  12  in the direction of the induced magnetic field (magnetic field component in the X-axis direction) and the resistance value of said GMR element changes. Thus, the sensor is provided which is highly sensitive to the change of the magnetic field. In addition, in the following description, the direction parallel to that where the GMR element is magnetized fixedly is defined as the X-axis direction, and the direction which is perpendicular to that where the GMR element is magnetized fixedly and also is located on the surface where the GMR elements are formed is defined as the Y-axis direction. Further, the direction perpendicular to the surface where the GMR elements are formed is defined as the Z-axis direction. 
         [0011]    Patent Document 2 has disclosed a sensor in which several magnetic bodies are provided for the magnetoresistance effect element to convert the external magnetic field in the vertical direction into magnetic field component in the horizontal direction so that the component of the magnetic field entering in the vertical direction is detected. 
       PATENT DOCUMENTS 
       [0012]    Patent Document 1: JP-P5500785 
         [0013]    Patent Document 2: JP-P5597206 
       SUMMARY 
       [0014]    However, in the techniques disclosed in Patent Document 1 and Patent Document 2, the following problem exists. That is, in the detection of a weak magnetic field, the intensity of the magnetic field coming out of the element part is not sufficiently high. Thus, it is necessary to improve the detection precision. 
         [0015]    Thus, the objective of the present invention is to solve the technical problem mentioned above. That is, the present invention aims to improve the detection precision of the magnetic sensor with an easy and convenient configuration. 
         [0016]    Here, the magnetic sensor according to one embodiment of the present invention, wherein a magnetic body which changes the direction of a magnetic field input to a magnetoresistance effect element is provided in the vicinity of the magnetoresistance effect element in which the resistance value changes according to the direction of the input magnetic field, and the magnetic body has a recess with a concave shape on the surface at a side where the magnetoresistance effect element is formed. In this way, the magnetic field to be detected is introduced to the magnetoresistance effect element effectively to improve the detection precision. 
         [0017]    Preferably, the recess of the magnetic body is provided on the side of the placement surface of the magnetic body, and the center of the recess is substantially identical to that of the magnetic body in the perpendicular direction of the placement surface of the magnetoresistance effect element. 
         [0018]    Further, the concave shape may at least include polygon having three or more sides, or may at least include arc. More preferably, the magnetic body is the soft magnetic body. 
         [0019]    According to the invention mentioned above, the detection precision of the magnetic sensor can be improved by introducing the magnetic field to be detected to the magnetoresistance effect element through the recess of the magnetic body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a view showing the configuration of the GMR chip. 
           [0021]      FIG. 2  is a diagram showing the characteristic of the GMR element. 
           [0022]      FIG. 3  is a view showing the configuration of the conventional magnetic sensor (the surface involving X-Z axis). 
           [0023]      FIG. 4  is a view showing the configuration of the conventional magnetic sensor (the surface involving X-Y axis). 
           [0024]      FIG. 5  is a schematic view showing the magnetic flux introduced to the GMR element part in the example of prior art. 
           [0025]      FIG. 6  is a view showing the configuration of the magnetic sensor in Embodiment 1 (the surface involving X-Z axis). 
           [0026]      FIG. 7  is a view showing the configuration of the magnetic sensor in Embodiment 1 (the surface involving X-Y axis). 
           [0027]      FIG. 8  is a schematic view showing the magnetic flux introduced to the GMR element part in Embodiment 1. 
           [0028]      FIG. 9  is a view showing the enlarged GMR element part in the example of prior art. 
           [0029]      FIG. 10  is a view showing the enlarged GMR element part in Embodiment 1. 
           [0030]      FIG. 11  shows the stimulation results in the example of prior art and Embodiment 1 about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
           [0031]      FIG. 12  is a view showing the configuration of the magnetic sensor in Embodiment 2 (the surface involving X-Z axis). 
           [0032]      FIG. 13  is a view showing the configuration of the magnetic sensor in Embodiment 2 (the surface involving X-Y axis). 
           [0033]      FIG. 14  is a schematic view showing the magnetic flux introduced to the GMR element part in Embodiment 2. 
           [0034]      FIG. 15  shows the stimulation results in the example of prior art and Embodiment 2 about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
           [0035]      FIG. 16  is a view showing the configuration of the magnetic sensor in Embodiment 3 (the surface involving X-Z axis). 
           [0036]      FIG. 17  is a view showing the configuration of the magnetic sensor in Embodiment 3 (the surface involving X-Y axis). 
           [0037]      FIG. 18  is a schematic view showing the magnetic flux introduced to the GMR element part in Embodiment 3. 
           [0038]      FIG. 19  shows the stimulation results in the example of prior art and Embodiment 3 about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0039]    The specific configuration in the present invention will be described in the following embodiments. Hereinafter, the basic configuration of the magnetic sensor in the present invention will be described in Embodiment 1, and the configuration of the magnetic sensor to be specifically used in to the present invention will be described in Embodiments 2 to 3. 
         [0040]    The GMR element is described as an example of the magnetoresistance effect element, but the element involving the magneto-resistance effect can also be used, including the TMR element, AMR element and the like. 
       Embodiment 1 
       [0041]    The first embodiment of the present invention will be described with reference to  FIG. 6  to  FIG. 11 .  FIG. 6  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Z axis.  FIG. 7  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Y axis.  FIG. 8  is a schematic view showing the magnetic field entering the GMR element part through the magnetic body in the present embodiment.  FIG. 9  is a schematic view showing the magnetic field entering the GMR element part through the magnetic body in the example of prior art where the GMR element part is enlarged.  FIG. 10  is a schematic view showing the magnetic field entering the GMR element part through the magnetic body in present embodiment where the GMR element part is enlarged.  FIG. 11  shows the stimulation results in the example of prior art and the present embodiment about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
       Configuration 
       [0042]    The shape of the soft magnetic body according to the present embodiment will be described with reference to  FIG. 6  and  FIG. 7 . GMR elements  111  and  112  are disposed in GMR chip  110 . These GMR elements form a bridge circuit. In the vicinity of the bridge circuit, magnetic body  121  changing the direction of the magnetic field input to the magnetoresistance effect element is disposed. In addition, in magnetic body  121 , recess  131  with a concave shape is disposed on the surface at a side where GMR elements  111  and  112  are formed, wherein recess  131  changes the direction of the magnetic field. 
         [0043]    Further, on the surface with the X axis and the Z axis, the shape of recess  131  of magnetic body  121  is preferably a triangle with a bottom edge at the side of the element disposing surface. However, as long as the direction of magnetic field H can be changed, the shape may be a polygon having three or more sides. 
         [0044]    Magnetic body  121  is the soft magnetic body made of the material such as the ferrite material, the permalloy (Ni—Fe alloy), Sendust (Fe—Si—Al alloy) or the like. The material is not restricted as long as magnetic body  121  functions to change the direction of magnetic field H. 
         [0045]    Further, magnetic body  121  is preferably composed of one component. However, as long as magnetic body  121  is capable of changing the direction of magnetic field H, the number of the components to constitute magnetic body  121  is not particularly restricted. 
       Function 
       [0046]    Hereinafter, magnetic field H introduced to GMR element parts  111  and  112  through the configuration mentioned above will be described with reference to  FIG. 8  to  FIG. 10 . Similar to that in the example of prior art, the magnetic field entering magnetic body  121  from the upper part of the figure in Z-axis direction is bended by magnetic body  121  and is introduced into the interior of magnetic body  121 . 
         [0047]    Magnetic field H introduced into the interior of magnetic body  121  is guided towards the outside of magnetic body  121  in the X-axis direction through the concave shape in the vicinity of recess  131  of magnetic body  121 . As a result, the magnetically concentrated magnetic field H enters the vicinity of GMR elements  111  and  112 , so the intensity of the magnetic field to be detected is increased. Further, it can be seen from  FIG. 9  and  FIG. 10  where the GMR element parts from the example of prior art and the present example are enlarged that the intensity of the magnetic field is increased in the present embodiment due to the magnetically concentrated magnetic field in recess  131 . In addition, if the incidence angles of magnetic field H entering the GMR element part with the effect mentioned above are compared, magnetic field H will be found to bend towards the X-axis direction in the present embodiment due to the effect produced by recess  131 . As such, with respect to magnetic field H entering GMR element  111 , not only the intensity of the magnetic field is increased, but also the component of magnetic field H in the X-axis direction is increased due to the bending of magnetic field H with the effects from magnetic body  121  and recess  131 , wherein the magnetic induction occurs in the GMR element in the X-axis direction. Thus, the detection of the magnetic sensor can be improved in precision. Although not shown in the figure, at the opposite side along the X-axis, the same happens to magnetic field H entering GMR element  122  with the effects from magnetic body  121  and recess  131 . As a result, the component of magnetic field H in the X-axis direction increases so that the detection precision of the magnetic sensor can be improved, wherein the magnetic induction occurs in the GMR element in the X-axis direction. 
         [0048]    With reference to  FIG. 11 , a simulation is performed to predict the intensity of magnetic field H introduced to GMR element parts  111  and  112  through the configuration mentioned above, and the result is described and compared against that from the example of prior art. It can be confirmed in Embodiment 1 that the intensity of magnetic field H introduced to GMR element parts  111  and  112  is increased compared to that in the example of prior art. 
         [0049]    With the functions mentioned above, the detection precision of the magnetic sensor can be improved by increasing the intensity of the magnetic field at the GMR element part. 
       Embodiment 2 
       [0050]    The second embodiment of the present invention will be described with reference to  FIG. 12  to  FIG. 15 .  FIG. 12  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Z axis.  FIG. 13  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Y axis.  FIG. 14  is a schematic view showing the magnetic field entering the GMR element part through the magnetic body in the present embodiment.  FIG. 15  shows the stimulation results in the example of prior art and the present embodiment about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
       Configuration 
       [0051]    The shape of the soft magnetic body according to the present embodiment will be described with reference to  FIG. 12  and  FIG. 13 . GMR elements  211  and  212  are formed in GMR chip  210 . These GMR elements form a bridge circuit. In the vicinity of the bridge circuit, magnetic body  221  changing the direction of the magnetic field input to the magnetoresistance effect element is disposed. In addition, in magnetic body  221 , recess  231  with a concave shape is disposed on the surface at a side where GMR elements  211  and  212  are formed, wherein recess  231  changes the direction of the magnetic field. 
         [0052]    Further, on the surface with the X axis and the Z axis, the shape of recess  231  of magnetic body  221  is preferably a tetragon. However, as long as the direction of magnetic field H can be changed by recess  231 , the shape can be the polygon having four or more sides. 
         [0053]    Magnetic body  221  is the soft magnetic body made of the material such as the ferrite material, the permalloy (Ni—Fe alloy), Sendust (Fe—Si—Al alloy) or the like. The material is not restricted as long as magnetic body  221  functions to change the direction of magnetic field H. 
         [0054]    Further, magnetic body  221  is preferably composed of one component. However, as long as magnetic body  221  is capable of changing the direction of magnetic field H, the number of the components to constitute magnetic body  221  is not particularly restricted. 
       Function 
       [0055]    Hereinafter, magnetic field H introduced to GMR element parts  211  and  212  through the configuration mentioned above will be described with reference to  FIG. 14 . Similar to that in the example of prior art, the magnetic field entering magnetic body  221  from the upper part of the figure in Z-axis direction is bended by magnetic body  221  and is introduced into the interior of magnetic body  221 . 
         [0056]    Magnetic field H introduced into the interior of magnetic body  221  is guided towards the outside of magnetic body  221  in the X-axis direction through the concave shape in the vicinity of recess  231  of magnetic body  221 . As a result, the magnetically concentrated magnetic field H enters the vicinity of GMR elements  211  and  212 , so the intensity of the magnetic field to be detected is increased. Similar to Embodiment 1, the incidence angle of magnetic field H entering the GMR element part in the present embodiment bends to a large extent towards the direction where the magnetic induction of the GMR element occurs (the X-axis direction). As such, with respect to magnetic field H entering GMR element  211 , not only the intensity of the magnetic field is increased, but also the component of magnetic field H in the X-axis direction is increased due to the bending of magnetic field H with the effects from magnetic body  221  and recess  231 , wherein the magnetic induction occurs in the GMR element in the X-axis direction. Thus, the detection of the magnetic sensor can be improved in precision. 
         [0057]    With reference to  FIG. 15 , a simulation is performed to predict the intensity of magnetic field H introduced to GMR element parts  211  and  212  through the configuration mentioned above, and the result is described and compared against that from the example of prior art. It can be confirmed in Embodiment 2 that the intensity of magnetic field H introduced to GMR element parts  211  and  212  is increased compared to that in the example of prior art. 
         [0058]    With the functions mentioned above, the detection precision of the magnetic sensor can be improved by increasing the intensity of the magnetic field at the GMR element part. 
       Embodiment 3 
       [0059]    The third embodiment of the present invention will be described with reference to  FIG. 16  to  FIG. 19 .  FIG. 16  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Z axis.  FIG. 17  is a view showing the configuration of the magnetic sensor according to the present embodiment in the surface involving X-Y axis.  FIG. 18  is a schematic view showing the magnetic field entering the GMR element part through the magnetic body in the present embodiment.  FIG. 19  shows the stimulation results in the example of prior art and the present embodiment about the intensity of the magnetic field at the magnetoresistance effect element part in the X-axis direction. 
       Configuration 
       [0060]    The shape of the soft magnetic body according to the present embodiment will be described with reference to  FIG. 16  and  FIG. 17 . GMR elements  311  and  312  are disposed in GMR chip  310 . Further, these GMR elements form a bridge circuit. In the vicinity of the bridge circuit, magnetic body  321  changing the direction of the magnetic field input to the magnetoresistance effect element is disposed. In addition, in magnetic body  321 , recess  331  with a concave shape is disposed on the surface at a side where GMR elements  311  and  312  are formed, wherein recess  331  changes the direction of the magnetic field. 
         [0061]    Further, on the surface with the X axis and the Z axis, the shape of recess  331  of magnetic body  321  is preferably a semi-circle. However, as long as the direction of magnetic field H can be changed by recess  331 , recess  331  may be a shape comprising arc in part or the whole part. Further, recess  331  may be a shape in which the arc and the polygon are combined together. 
         [0062]    Magnetic body  321  is the soft magnetic body made of the material such as the ferrite material, the permalloy (Ni—Fe alloy), Sendust (Fe—S—Al alloy) or the like. The material is not restricted as long as magnetic body  321  functions to change the direction of magnetic field H. 
         [0063]    Further, magnetic body  321  is preferably composed of one component. However, as long as magnetic body  321  is capable of changing the direction of magnetic field H, the number of the components to constitute magnetic body  321  is not particularly restricted. 
       Function 
       [0064]    Hereinafter, magnetic field H introduced to GMR element parts  311  and  312  through the configuration mentioned above will be described with reference to  FIG. 18 . Similar to that in the example of prior art, the magnetic field entering magnetic body  321  from the upper part of the figure in Z-axis direction is bended by magnetic body  321  and is introduced into the interior of magnetic body  321 . 
         [0065]    Magnetic field H introduced into the interior of magnetic body  321  is guided towards the outside of magnetic body  321  in the X-axis direction through the concave shape in the vicinity of recess  331  of magnetic body  321 . As a result, the magnetically concentrated magnetic field H enters the vicinity of GMR elements  311  and  312 , so the intensity of the magnetic field to be detected is increased. Similar to Embodiment 1, the incidence angle of magnetic field H entering the GMR element part in the present embodiment bends to a large extent towards the direction where the magnetic induction of the GMR element occurs (the X-axis direction). As such, with respect to magnetic field H entering GMR element  311 , not only the intensity of the magnetic field is increased, but also the component of magnetic field H in the X-axis direction is increased due to the bending of magnetic field H with the effects from magnetic body  321  and recess  331 , wherein the magnetic induction occurs in the GMR element in the X-axis direction. Thus, the detection of the magnetic sensor can be improved in precision. p With reference to  FIG. 19 , a simulation is performed to predict the intensity of magnetic field H introduced to GMR element parts  311  and  312  through the configuration mentioned above, and the result is described and compared against that from the example of prior art. It can be confirmed in Embodiment 3 that the intensity of magnetic field H introduced to GMR element parts  311  and  312  is increased compared to that in the example of prior art. 
         [0066]    With the functions mentioned above, the detection precision of the magnetic sensor can be improved by increasing the intensity of the magnetic field at the GMR element part. 
       Industrial application 
       [0067]    The present invention can be applied to various measuring devices such as the magnetic sensor, the galvanometer and the encoder. Thus, the present invention can be utilized in the industry. 
       DESCRIPTION OF REFERENCE NUMERALS 
       [0000]    
       
           1  GMR chip 
           10  GMR chip in example of prior art 
           11 ,  12  element disposing part in example of prior art 
           21  magnetic body in example of prior art 
           110  GMR chip in Embodiment 1 
           111 ,  112  element disposing part in Embodiment 1 
           121  magnetic body in Embodiment 1 
           131  recess in Embodiment 1 for changing magnetic field 
           210  GMR chip in Embodiment 2 
           211 ,  212  element disposing part in Embodiment 2 
           221  magnetic body in Embodiment 2 
           231  recess in Embodiment 2 for changing magnetic field 
           310  GMR chip in Embodiment 3 
           311 ,  312  element disposing part in Embodiment 3 
           321  magnetic body in Embodiment 3 
           331  recess in Embodiment 3 for changing magnetic field 
         A fixed direction of magnetization 
         H mangetic field