Magnetic sensor and method for manufacturing bias magnet

Abstract

The present invention improves the detection accuracy of a magnetic sensor. A bias magnet (5) provided to this magnetic sensor (100) has first to fourth magnets (511)-(514) magnetized in a first direction (D1). The first magnet (511) and the second magnet (512) are joined such that the N-pole (50A) of the first magnet (511) and the S-pole (50B) of the second magnet (512) are adjacent to each other and the S-pole (50B) of the first magnet (511) and the N-pole (50A) of the second magnet (512) are adjacent to each other in a second direction (D2). The first magnet (511) and the third magnet (513) are joined such that the N-pole (50A) of the first magnet (511) and the S-pole (50B) of the third magnet (513) are adjacent to each other and the S-pole (50B) of the first magnet (511) and the N-pole (50A) of the third magnet (513) are adjacent to each other in a third direction (D3). The third magnet (513) and the fourth magnet (514) are joined adjacent to each other in the second direction (D2). The second magnet (512) and the fourth magnet (514) are joined adjacent to each other in the third direction (D3).

Description

Magnetic sensor and bias magnet manufacturing method

[0001] The present disclosure relates to a magnetic sensor and a method for manufacturing a magnet, and more particularly to a magnetic sensor including a bias magnet and a method for manufacturing a bias magnet.

[0002] The magnetic sensor device described in Patent Document 1 includes a first bias magnet, a second bias magnet, and a magnetic sensor. The second bias magnet is rotated by a predetermined angle relative to the first bias magnet. The magnetic sensor is disposed between the bottom surface of the first bias magnet and the top surface of the second bias magnet.

[0003] Japanese Patent Application Laid-Open No. 2017-173236

[0004] In a magnetic sensor device (magnetic sensor) such as that described in Patent Document 1, improvement in detection accuracy is desired.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide a magnetic sensor that can improve detection accuracy and a method for manufacturing a bias magnet used therein.

[0006] A magnetic sensor according to one aspect of the present disclosure includes an output circuit and a bias magnet. The output circuit has a plurality of magnetoresistive elements and outputs an output signal corresponding to the strength of a magnetic field applied to the plurality of magnetoresistive elements. The bias magnet applies a bias magnetic field to the plurality of magnetoresistive elements. The bias magnet includes a first magnet, a second magnet, a third magnet, and a fourth magnet magnetized in a first direction. The first magnet and the second magnet are coupled such that the north pole of the first magnet and the south pole of the second magnet are adjacent to each other and the south pole of the first magnet and the north pole of the second magnet are adjacent to each other in a second direction perpendicular to the first direction. The first magnet and the third magnet are coupled such that the north pole of the first magnet and the south pole of the third magnet are adjacent to each other and the south pole of the first magnet and the north pole of the third magnet are adjacent to each other in a third direction perpendicular to both the first direction and the second direction. The third magnet and the fourth magnet are coupled in the second direction such that the north pole of the third magnet is adjacent to the south pole of the fourth magnet and the south pole of the third magnet is adjacent to the north pole of the fourth magnet, and the second magnet and the fourth magnet are coupled in the third direction such that the north pole of the second magnet is adjacent to the south pole of the fourth magnet and the south pole of the second magnet is adjacent to the north pole of the fourth magnet.

[0007] A bias magnet manufacturing method according to another aspect of the present disclosure is a method for manufacturing a bias magnet used as part of the magnetic sensor of the above aspect. The manufacturing method includes a generating step, a first bonding step, a second bonding step, a third bonding step, and a fourth bonding step. In the generating step, a first magnet, a second magnet, a third magnet, and a fourth magnet are generated by magnetizing a plurality of magnetic materials in a first direction. In the first bonding step, the first magnet and the second magnet are bonded together so that the north pole of the first magnet and the south pole of the second magnet are adjacent to each other in the second direction, and the south pole of the first magnet and the north pole of the second magnet are adjacent to each other in the third direction. In the second bonding step, the first magnet and the third magnet are bonded together so that the north pole of the first magnet and the south pole of the third magnet are adjacent to each other in the third direction. In the third coupling step, the third magnet and the fourth magnet are coupled so that the north pole of the third magnet and the south pole of the fourth magnet are adjacent to each other in the second direction, and the south pole of the third magnet and the north pole of the fourth magnet are adjacent to each other in the third direction. In the fourth coupling step, the third magnet and the fourth magnet are coupled so that the north pole of the second magnet and the south pole of the fourth magnet are adjacent to each other in the third direction.

[0008] According to the magnetic sensor and bias magnet manufacturing method of the present disclosure, it is possible to improve the detection accuracy of the magnetic sensor.

[0009] FIG. 1 is a plan view of a magnetic sensor according to an embodiment. FIG. 2 is a cross-sectional view of the magnetic sensor according to an embodiment. FIG. 3A is a plan view of a bias magnet included in the magnetic sensor according to an embodiment. FIG. 3B is a front view of the bias magnet included in the magnetic sensor according to an embodiment. FIG. 3C is a rear view of the bias magnet included in the magnetic sensor according to an embodiment. FIG. 4 is a schematic diagram showing a state in which the magnetic sensor according to an embodiment is used. FIG. 5 is an equivalent circuit diagram of a first full-bridge circuit of the magnetic sensor according to an embodiment. FIG. 6 is an equivalent circuit diagram of a second full-bridge circuit of the magnetic sensor according to an embodiment. FIG. 7 is an explanatory diagram showing an output signal of the magnetic sensor according to an embodiment. FIG. 8 is a schematic diagram for explaining the effect achieved by the magnetic sensor according to an embodiment. FIG. 9 is a schematic diagram for explaining a method for magnetizing the bias magnet included in the magnetic sensor according to an embodiment. FIG. 10 is a flowchart showing a method for manufacturing a bias magnet used as part of the magnetic sensor according to an embodiment.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Common elements in the embodiments described below are designated by the same reference numerals, and redundant descriptions of the common elements may be omitted. The following embodiments and modifications are merely a portion of the various embodiments of the present disclosure. Various modifications of the following embodiments and modifications can be made depending on the design, etc., as long as the object of the present disclosure can be achieved. The configurations of the modifications can also be combined as appropriate.

[0011] The drawings described in this disclosure are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios. Note that the arrows indicating the directions in the drawings are merely examples and are not intended to define the directions when using the magnetic detection system 200 (or the magnetic sensor 100). Furthermore, the arrows indicating the directions in the drawings are merely shown for the purpose of explanation and do not have any substance.

[0012] In addition, the term "orthogonal (perpendicular)" as used herein not only refers to a state in which the angle between two things is exactly 90 degrees, but also refers to a state in which two things intersect within a certain range of difference. In other words, the angle between two orthogonal things falls within a certain range of difference from 90 degrees (for example, 10 degrees or less). In other words, the term "orthogonal" as used herein includes cases in which the angle between two things is 80 degrees or more and 100 degrees or less. Similarly, the term "parallel" as used herein also includes not only a state in which two things do not strictly intersect, but also a state in which two things are lined up within a certain range of difference. For example, the term "parallel" as used herein includes cases in which one thing is inclined at an angle of 10 degrees or less relative to the other. In other words, the term "parallel" as used herein includes cases in which the angle between one thing and the other is -10 degrees or more and 10 degrees or less.

[0013] (1) Overview First, an overview of the magnetic sensor 100 according to this embodiment will be described with reference to FIGS. 1 to 3C.

[0014] 1 is a plan view of a magnetic sensor 100 according to this embodiment. As shown in FIG. 1, the magnetic sensor 100 according to this embodiment includes an output circuit 3 and a bias magnet 5.

[0015] The output circuit 3 has a plurality of (eight in the example of FIG. 1 ) magnetoresistive elements 300 (or magnetoresistive effect elements 300). The output circuit 3 outputs an output signal according to the strength of the magnetic field applied to the plurality of magnetoresistive elements 300.

[0016] 2 is a cross-sectional view of the magnetic sensor 100 according to the embodiment. The bias magnet 5 applies a bias magnetic field to the multiple magnetoresistance elements 300. As shown in Fig. 1, the bias magnet 5 includes a first magnet 511, a second magnet 512, a third magnet 513, and a fourth magnet 514, which are magnetized in a first direction D1 (see Fig. 2).

[0017] 3A is a plan view of the bias magnet 5 included in the magnetic sensor 100 according to the embodiment. FIG. 3B is a front view of the bias magnet 5 included in the magnetic sensor 100 according to the embodiment. FIG. 3C is a rear view of the bias magnet 5 included in the magnetic sensor 100 according to the embodiment. As shown in FIGS. 3A and 3B , the first magnet 511 and the second magnet 512 are coupled together in a second direction D2 that is orthogonal to the first direction D1, such that the north pole 50A of the first magnet 511 and the south pole 50B of the second magnet 512 are adjacent to each other, and the south pole 50B of the first magnet 511 and the north pole 50A of the second magnet 512 are adjacent to each other.

[0018] As shown in Figures 3A to 3C, the first magnet 511 and the third magnet 513 are connected in a third direction D3 that is perpendicular to both the first direction D1 and the second direction D2, so that the north pole 50A of the first magnet 511 and the south pole 50B of the third magnet 513 are adjacent to each other, and so that the south pole 50B of the first magnet 511 and the north pole 50A of the third magnet 513 are adjacent to each other.

[0019] As shown in Figures 3A and 3C, the third magnet 513 and the fourth magnet 514 are connected in the second direction D2 so that the north pole 50A of the third magnet 513 and the south pole 50B of the fourth magnet 514 are adjacent to each other, and the south pole 50B of the third magnet 513 and the north pole 50A of the fourth magnet 514 are adjacent to each other.

[0020] As shown in Figures 3A to 3C, the second magnet 512 and the fourth magnet 514 are connected in the third direction D3 so that the north pole 50A of the second magnet 512 and the south pole 50B of the fourth magnet 514 are adjacent to each other, and the south pole 50B of the second magnet 512 and the north pole 50A of the fourth magnet 514 are adjacent to each other.

[0021] In this embodiment, the first direction D1 is a direction parallel to the Z-axis direction in the figure, the second direction D2 is a direction parallel to the Y-axis direction in the figure, and the third direction D3 is a direction parallel to the X-axis direction in the figure.

[0022] For example, a magnet having four magnetic poles by magnetizing two regions contained in a single magnetic material can be used as a bias magnet for a magnetic sensor. The magnet having four magnetic poles has a first magnetized region and a second magnetized region magnetized in a first direction D1. The first magnetized region and the second magnetized region are magnetized in the first direction D1 so that their north and south poles are opposite each other. In a magnet having four magnetic poles, the space between the first magnetized region and the second magnetized region is a neutral zone. Note that the neutral zone is an unmagnetized region. As will be described later, the smaller the neutral zone that can be contained in the bias magnet, the stronger the bias magnetic field can be, thereby improving the detection accuracy of the magnetic sensor.

[0023] According to the magnetic sensor 100 of this embodiment, a bias magnet is used by combining multiple magnets that are magnetized in only one direction, so there is almost no neutral zone in the bias magnet, thereby improving detection accuracy.

[0024] (2) Details The detailed configuration of the magnetic detection system 200 according to this embodiment will be described below with reference to FIGS. 1 to 7. FIG.

[0025] 4 is a schematic diagram showing a state in which the magnetic sensor 100 according to the embodiment is used. In this embodiment, as an example, a case will be described in which the magnetic detection system 200 is used to determine the rotation angle of the rotor 8 of a motor.

[0026] The rotor 8 includes a plurality of permanent magnets. The plurality of permanent magnets form a plurality of magnetic poles 80. The plurality of magnetic poles 80 are aligned in the rotation direction of the rotor 8 so that north and south poles alternate. In FIG. 4, the plurality of magnetic poles 80 are aligned so that the north and south poles alternate every 45 degrees along the rotation direction of the rotor 8. Note that in FIG. 4, each magnetic pole 80 is labeled with the letter "N" representing the north pole or the letter "S" representing the south pole, but these are merely letters added for the purpose of explanation and are not actually attached. The same applies to the "N" and "S" attached to the bias magnet 5 in FIGS. 1 to 3C.

[0027] As shown in FIG. 1 , the magnetic detection system 200 of this embodiment includes a magnetic sensor 100 and a processing circuit 201 .

[0028] 1 and 2, the magnetic sensor 100 of this embodiment includes a bias magnet 5, a first protective film 71, a GMR (Giant Magneto Resistance) film 72, a thermal oxide film 73, a substrate 74, and a second protective film 75. Note that the first protective film 71, the thermal oxide film 73, the substrate 74, and the second protective film 75 are not shown in FIG.

[0029] 1 to 3C, the bias magnet 5 has a rectangular parallelepiped shape. As described above, the bias magnet 5 has a first magnet 511, a second magnet 512, a third magnet 513, and a fourth magnet 514. In the following description, when the first magnet 511, the second magnet 512, the third magnet 513, and the fourth magnet 514 are not to be distinguished from one another, the first magnet 511, the second magnet 512, the third magnet 513, and the fourth magnet 514 may each be simply referred to as a "magnet 51."

[0030] Each magnet 51 is shaped like a rectangular parallelepiped. The first magnet 511, the second magnet 512, the third magnet 513, and the fourth magnet 514 have the same shape and size. The magnet 51 is a single member. A ferrite magnet or a neodymium magnet may be used as the magnet 51.

[0031] Each of the first magnet 511, the second magnet 512, the third magnet 513, and the fourth magnet 514 is magnetized in a first direction D1. In other words, the first direction D1 is the magnetization direction of the magnet 51. The magnet 51 has a north pole 50A and a south pole 50B aligned in the first direction D1. When the north pole 50A and the south pole 50B are not distinguished from each other, the north pole 50A and the south pole 50B may be referred to as a "magnetic pole 50."

[0032] As described above, the first magnet 511 and the second magnet 512 are connected in the second direction D2 perpendicular to the first direction D1 so that the north pole 50A (see Figure 3B) of the first magnet 511 and the south pole 50B (see Figure 3B) of the second magnet 512 are adjacent to each other, and so that the south pole 50B (see Figure 3B) of the first magnet 511 and the north pole 50A (see Figure 3B) of the second magnet 512 are adjacent to each other.

[0033] The first magnet 511 and the third magnet 513 are connected in a third direction D3 that is perpendicular to both the first direction D1 and the second direction D2, so that the north pole 50A of the first magnet 511 and the south pole 50B of the third magnet 513 (see Figure 3C) are adjacent to each other, and so that the south pole 50B of the first magnet 511 and the north pole 50A of the third magnet 513 (see Figure 3C) are adjacent to each other.

[0034] The third magnet 513 and the fourth magnet 514 are connected in the second direction D2 so that the north pole 50A of the third magnet 513 and the south pole 50B of the fourth magnet 514 (see Figure 3C) are adjacent to each other, and the south pole 50B of the third magnet 513 and the north pole 50A of the fourth magnet 514 (see Figure 3C) are adjacent to each other.

[0035] The second magnet 512 and the fourth magnet 514 are connected in the third direction D3 so that the north pole 50A of the second magnet 512 and the south pole 50B of the fourth magnet 514 are adjacent to each other, and the south pole 50B of the second magnet 512 and the north pole 50A of the fourth magnet 514 are adjacent to each other.

[0036] The first magnet 511, the second magnet 512, and the third magnet 513 are magnetically coupled to each other while in contact with each other. The second magnet 512, the first magnet 511, and the fourth magnet 514 are magnetically coupled to each other while in contact with each other. The third magnet 513, the first magnet 511, and the fourth magnet 514 are magnetically coupled to each other while in contact with each other. The fourth magnet 514, the second magnet 512, and the third magnet 513 are magnetically coupled to each other while in contact with each other. In other words, in the bias magnet 5 of this embodiment, two magnets 51 aligned along the second direction D2 or the third direction D3 are magnetically coupled to each other while in contact with each other. This allows multiple magnets 51 to be coupled together in a relatively easy manner. Furthermore, because two magnets 51 aligned along the second direction D2 or the third direction D3 are coupled to each other while in contact with each other, the neutral zone between the two magnets 51 can be almost eliminated.

[0037] As described above, the bias magnet 5 has a plurality of (eight in this embodiment) magnetic poles 50. Four of the eight magnetic poles 50 are arranged on a first plane parallel to both the X-axis and the Y-axis. The remaining four of the eight magnetic poles 50 are arranged on a second plane parallel to the first plane.

[0038] That is, the bias magnet 5 has two sets of four magnetic poles 50, and in each set, the four magnetic poles 50 are arranged on the same plane. The magnetic poles 50 belonging to different sets are arranged at different positions in the Z-axis direction. The Z coordinates of the four magnetic poles 50 shown in FIG. 1 are greater than the Z coordinates of the remaining four magnetic poles 50.

[0039] The eight magnetic poles 50 are arranged such that adjacent magnetic poles 50 in the X-axis direction have different poles and adjacent magnetic poles 50 in the Y-axis direction have different poles. The eight magnetic poles 50 are also arranged such that adjacent magnetic poles 50 in the Z-axis direction have different poles.

[0040] The bias magnet 5 generates a bias magnetic field along the positive direction of the X axis, a bias magnetic field along the negative direction of the X axis, a bias magnetic field along the positive direction of the Y axis, and a bias magnetic field along the negative direction of the Y axis.

[0041] The bias magnet 5 of this embodiment applies bias magnetic fields in opposite directions along the third direction D3 to the first magnetic resistance element 111 and the third magnetic resistance element 121, and the second magnetic resistance element 112 and the fourth magnetic resistance element 122. The bias magnet 5 also applies bias magnetic fields in opposite directions along the second direction D2 to the fifth magnetic resistance element 211 and the seventh magnetic resistance element 221, and the sixth magnetic resistance element 212 and the eighth magnetic resistance element 222. This makes it possible to suppress distortion of the output waveform of each of the multiple magnetic resistance elements 300.

[0042] The substrate 74 has a plate-like shape, for example, as shown in Fig. 2. The substrate 74 is, for example, a silicon substrate. The substrate 74 holds the bias magnet 5 and the GMR film 72. Note that the substrate 74 is not limited to a silicon substrate, and may be, for example, an alumina substrate.

[0043] 2, the GMR film 72 is formed on the surface of a substrate 74. More specifically, the GMR film 72 is formed indirectly on the surface of the substrate 74 via a thermal oxide film 73. In this way, the substrate 74 holds the GMR film 72.

[0044] The GMR film 72 includes a plurality of layers, which are electrically connected to one another via through holes.

[0045] The GMR film 72 includes an output circuit 3 (see FIG. 1). The output circuit 3 also has a first full-bridge circuit 1 (see FIG. 5, which will be described later) and a second full-bridge circuit 2 (see FIG. 6, which will be described later).

[0046] FIG. 5 is an equivalent circuit diagram of the first full-bridge circuit 1 of the magnetic sensor 100 according to the embodiment. As shown in FIG. 5, the first full-bridge circuit 1 includes a first series circuit 11 and a second series circuit 12. The first series circuit 11 and the second series circuit 12 are connected in parallel to each other. The first series circuit 11 includes a first magnetic resistance element 111 and a second magnetic resistance element 112. The first magnetic resistance element 111 and the second magnetic resistance element 112 are connected in series to each other and detect a magnetic field along the X-axis (third direction D3). The second series circuit 12 includes a third magnetic resistance element 121 and a fourth magnetic resistance element 122. The third magnetic resistance element 121 and the fourth magnetic resistance element 122 are connected in series to each other and detect a magnetic field along the X-axis (third direction D3).

[0047] The first magnetic resistance element 111 and the third magnetic resistance element 121 are adjacent to each other in the X-axis direction. The second magnetic resistance element 112 and the fourth magnetic resistance element 122 are adjacent to each other in the X-axis direction. A bias magnetic field is applied from the bias magnet 5 to the first magnetic resistance element 111 and the third magnetic resistance element 121 in the positive direction of the X-axis. A bias magnetic field is applied from the bias magnet 5 to the second magnetic resistance element 112 and the fourth magnetic resistance element 122 in the negative direction of the X-axis.

[0048] FIG. 6 is an equivalent circuit diagram of the second full-bridge circuit 2 of the magnetic sensor 100 according to the embodiment. As shown in FIG. 6 , the second full-bridge circuit 2 includes a third series circuit 21 and a fourth series circuit 22. The third series circuit 21 and the fourth series circuit 22 are connected in parallel to each other. The third series circuit 21 includes a fifth magnetoresistance element 211 and a sixth magnetoresistance element 212. The fifth magnetoresistance element 211 and the sixth magnetoresistance element 212 are connected in series to each other and detect a magnetic field along the Y-axis (second direction D2). The fourth series circuit 22 includes a seventh magnetoresistance element 221 and an eighth magnetoresistance element 222. The seventh magnetoresistance element 221 and the eighth magnetoresistance element 222 are connected in series to each other and detect a magnetic field along the Y-axis (second direction D2).

[0049] The fifth magnetic resistance element 211 and the seventh magnetic resistance element 221 are adjacent to each other in the Y-axis direction. The sixth magnetic resistance element 212 and the eighth magnetic resistance element 222 are adjacent to each other in the Y-axis direction. A bias magnetic field is applied from the bias magnet 5 to the fifth magnetic resistance element 211 and the seventh magnetic resistance element 221 in the positive direction of the Y-axis. A bias magnetic field is applied from the bias magnet 5 to the sixth magnetic resistance element 212 and the eighth magnetic resistance element 222 in the negative direction of the Y-axis.

[0050] As shown in FIG. 1 , the magnetic sensor 100 further includes a first output terminal 1T, a second output terminal 2T, a third output terminal 3T, and a fourth output terminal 4T. The first output terminal 1T outputs a first output signal from a connection point between the first magnetic resistance element 111 and the second magnetic resistance element 112. The second output terminal 2T outputs a second output signal from a connection point between the third magnetic resistance element 121 and the fourth magnetic resistance element 122. The third output terminal 3T outputs a third output signal from a connection point between the fifth magnetic resistance element 211 and the sixth magnetic resistance element 212. The fourth output terminal 4T outputs a fourth output signal from a connection point between the seventh magnetic resistance element 221 and the eighth magnetic resistance element 222. In this embodiment, the first output signal is a −cos signal, the second output signal is a +cos signal, the third output signal is a +sine signal, and the fourth output signal is a −sine signal. That is, the first output signal and the second output signal are in opposite phases to each other, and the third output signal and the fourth output signal are in opposite phases to each other.

[0051] Hereinafter, each of the first magnetoresistance element 111, the second magnetoresistance element 112, the third magnetoresistance element 121, the fourth magnetoresistance element 122, the fifth magnetoresistance element 211, the sixth magnetoresistance element 212, the seventh magnetoresistance element 221, and the eighth magnetoresistance element 222 may be referred to as a magnetoresistance element 300. In other words, the output circuit 3 has a plurality (eight) of magnetoresistance elements 300.

[0052] 1, the magnetic sensor 100 further includes power supply terminals H10 and H20 and reference terminals L10 and L20. The power supply terminals H10 and H20 are high-potential terminals electrically connected to a high-potential electric circuit of the power supply. The reference terminals L10 and L20 are low-potential terminals electrically connected to a low-potential electric circuit (a reference potential electric circuit) of the power supply. In this embodiment, the reference terminals L10 and L20 are ground terminals electrically connected to a ground potential electric circuit.

[0053] A first end of the first magnetic resistance element 111 is electrically connected to a power supply terminal H10. A second end of the first magnetic resistance element 111 is electrically connected to a first end of the second magnetic resistance element 112. A second end of the second magnetic resistance element 112 is electrically connected to a reference terminal L20. A first output terminal 1T is electrically connected to a connection point between the first magnetic resistance element 111 and the second magnetic resistance element 112.

[0054] A first end of the third magnetic resistance element 121 is electrically connected to the reference terminal L10. A second end of the third magnetic resistance element 121 is electrically connected to a first end of the fourth magnetic resistance element 122. A second end of the fourth magnetic resistance element 122 is electrically connected to the power supply terminal H20. A second output terminal 2T is electrically connected to the connection point between the third magnetic resistance element 121 and the fourth magnetic resistance element 122.

[0055] A first end of the fifth magnetic resistance element 211 is electrically connected to the reference terminal L10. A second end of the fifth magnetic resistance element 211 is electrically connected to a first end of the sixth magnetic resistance element 212. A second end of the sixth magnetic resistance element 212 is electrically connected to the power supply terminal H10. A third output terminal 3T is electrically connected to the connection point between the fifth magnetic resistance element 211 and the sixth magnetic resistance element 212.

[0056] A first end of the seventh magnetic resistance element 221 is electrically connected to the power supply terminal H20. A second end of the seventh magnetic resistance element 221 is electrically connected to a first end of the eighth magnetic resistance element 222. A second end of the eighth magnetic resistance element 222 is electrically connected to the reference terminal L20. The fourth output terminal 4T is electrically connected to the connection point between the seventh magnetic resistance element 221 and the eighth magnetic resistance element 222.

[0057] The first output terminal 1T, the second output terminal 2T, the third output terminal 3T, and the fourth output terminal 4T are electrically connected to the processing circuit 201. For simplification, FIG. 1 shows only the first output terminal 1T as being connected to the processing circuit 201.

[0058] 1 and 4 to 6, the shape of the magnetoresistive element 300 is illustrated as a rectangle when viewed from the Z-axis direction. However, this shape is a schematic diagram illustrating the orientation of the magnetoresistive element 300, and does not necessarily match the actual shape of the magnetoresistive element 300.

[0059] The electrical resistance value of the magnetoresistive element 300 changes depending on the magnitude of the applied magnetic field. The magnetic sensor 100 outputs the change in the electrical resistance value of the magnetoresistive element 300 as a voltage signal. The magnetoresistive element 300 is sensitive to magnetic fields in the third direction D3 (the direction along the long side in FIG. 1 ) and is also sensitive to magnetic fields in the second direction D2 (the direction along the short side in FIG. 1 ). The sensitivity of the magnetoresistive element 300 is greatest for magnetic fields in other directions.

[0060] The first magnetic resistance element 111, the second magnetic resistance element 112, the third magnetic resistance element 121, and the fourth magnetic resistance element 122 are arranged so as to be sensitive to magnetic fields along the X-axis and the Y-axis. The first magnetic resistance element 111, the second magnetic resistance element 112, the third magnetic resistance element 121, and the fourth magnetic resistance element 122 exhibit the same change in resistance value in a magnetic field along the positive direction of the X-axis as in a magnetic field along the negative direction of the X-axis, provided that the magnitudes of the magnetic fields are the same. Furthermore, the first magnetic resistance element 111, the second magnetic resistance element 112, the third magnetic resistance element 121, and the fourth magnetic resistance element 122 exhibit the same change in resistance value in a magnetic field along the positive direction of the Y-axis as in a magnetic field along the negative direction of the Y-axis, provided that the magnitudes of the magnetic fields are the same.

[0061] The fifth magnetoresistance element 211, the sixth magnetoresistance element 212, the seventh magnetoresistance element 221, and the eighth magnetoresistance element 222 are arranged to be sensitive to magnetic fields along the X-axis and the Y-axis. The fifth magnetoresistance element 211, the sixth magnetoresistance element 212, the seventh magnetoresistance element 221, and the eighth magnetoresistance element 222 exhibit the same change in resistance value in a magnetic field along the positive direction of the X-axis as in a magnetic field along the negative direction of the X-axis, provided that the magnitudes of the magnetic fields are the same. Furthermore, the fifth magnetoresistance element 211, the sixth magnetoresistance element 212, the seventh magnetoresistance element 221, and the eighth magnetoresistance element 222 exhibit the same change in resistance value in a magnetic field along the positive direction of the Y-axis as in a magnetic field along the negative direction of the Y-axis, provided that the magnitudes of the magnetic fields are the same.

[0062] When viewed from the Z-axis direction, with the center of the magnetic sensor 100 as the reference, the magnetic resistance elements 300 are arranged as follows: The first magnetic resistance element 111 and the third magnetic resistance element 121 are arranged on the negative side of the Y-axis from the center. The second magnetic resistance element 112 and the fourth magnetic resistance element 122 are arranged on the positive side of the Y-axis from the center. The fifth magnetic resistance element 211 and the seventh magnetic resistance element 221 are arranged on the negative side of the X-axis from the center. The sixth magnetic resistance element 212 and the eighth magnetic resistance element 222 are arranged on the positive side of the X-axis from the center.

[0063] The magnetoresistive element 300 is, for example, a giant magnetoresistance (GMR) element. More specifically, the magnetoresistive element 300 is a current-in-plane (CIP) type GMR element. The magnetoresistive element 300 has no sensitivity in a predetermined direction (for example, the Z-axis direction) and is isotropic sensitivity in directions intersecting the predetermined direction (for example, the X-axis direction and the Y-axis direction).

[0064] The bias magnet 5 applies to each of the plurality of (eight) magnetoresistive elements 300 a magnetic field (bias magnetic field) having a strength equal to or less than half the anisotropic magnetic field of each of the plurality of magnetoresistive elements 300. This makes it possible to suppress distortion of the output waveform of each of the plurality of magnetoresistive elements 300.

[0065] The thermal oxide film 73 covers the surface of the base material 74. The thermal oxide film 73 is formed on the surface of the base material 74 by performing a heat treatment on the base material 74. In this embodiment, the base material 74 is a silicon substrate, and the thermal oxide film 73 is a silicon oxide film.

[0066] 2, the first protective film 71 covers the GMR film 72. The first protective film 71 is made of, for example, a resin or Al. ２ O ３ It is made of a metal oxide such as alumina or a metal nitride.

[0067] 2, the second protective film 75 covers the bias magnet 5 mounted on the back surface of the substrate 74 (the surface opposite to the surface on which the GMR film 72 is disposed). The second protective film 75 of this embodiment is made of resin. In other words, the magnetic sensor 100 of this embodiment further includes a resin member that covers the bias magnet 5.

[0068] (2.3) Configuration of the Processing Circuit The processing circuit 201 (see FIG. 1) includes, for example, a computer system having one or more processors and a memory. The functions of the processing circuit 201 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0069] The processing circuit 201 determines the direction of the magnetic field applied to the magnetic sensor 100 based on the output signal of the magnetic sensor 100. More specifically, the processing circuit 201 determines the direction of the magnetic field applied to the magnetic sensor 100 based on the first output signal, second output signal, third output signal, and fourth output signal described above. The first output signal and second output signal are signals output from the first full-bridge circuit 1. The third output signal and fourth output signal are signals output from the second full-bridge circuit 2.

[0070] 1 and 5, the first series circuit 11 and the second series circuit 12 in the first full-bridge circuit 1 have the same sensitivity direction of the magnetoresistive element 300 and the same direction of the applied bias magnetic field, but have opposite relationships between the high potential side and the low potential side. Therefore, the second output signal has an opposite phase to the first output signal.

[0071] 1 and 6, the third series circuit 21 and the fourth series circuit 22 in the second full-bridge circuit 2 have the same sensitivity direction of the magnetoresistive element 300 and the same direction of the applied bias magnetic field, but have opposite relationships between the high potential side and the low potential side. Therefore, the fourth output signal has an opposite phase to the third output signal.

[0072] (3) Detection of Magnetic Field Direction Next, the operation of the magnetic sensor 100 according to this embodiment to detect the magnetic field direction of the rotor 8 will be described with reference to FIG.

[0073] The magnetic sensor 100 is installed near the rotor 8. The multiple magnetic poles 80 of the rotor 8 form a magnetic field. As the rotor 8 rotates, the direction of the magnetic field applied to the magnetic sensor 100 changes. The processing circuit 201 determines the direction of the magnetic field applied to the magnetic sensor 100 based on the output of the magnetic sensor 100.

[0074] Note that even when the rotor 8 does not rotate but the magnetic sensor 100 rotates relative to the rotor 8, the direction of the magnetic field applied to the magnetic sensor 100 changes, and the processing circuit 201 can determine the direction of the magnetic field. Therefore, the following description will be given with reference to Figure 4, assuming that the rotor 8 is fixed and the position of the magnetic sensor 100 changes in the order of positions L1, L2, L3, and L4. The magnetic sensor 100 rotates around the rotor 8, and the X-axis and Y-axis also rotate accordingly.

[0075] At each of positions L1, L2, L3, and L4, the magnetic sensor 100 is disposed radially outward of the rotor 8. In this case, the direction of the magnetic field applied to the magnetic sensor 100 is perpendicular to the direction of the rotation axis of the rotor 8, so it is necessary to adjust the orientation of the magnetic sensor 100 so that the Z axis set in the magnetic sensor 100 is aligned with the direction of the rotation axis of the rotor 8.

[0076] As the position of the magnetic sensor 100 changes in the order of positions L1, L2, L3, and L4 (actually, as the rotor 8 rotates), the first output signal, the second output signal, the third output signal, and the fourth output signal each change in a sine wave or cosine wave. Figure 7 shows a waveform W1 of the second output signal and a waveform W2 of the third output signal of the magnetic sensor 100 according to the embodiment. Because the first output signal is a signal with an opposite phase to the second output signal and the fourth output signal is a signal with an opposite phase to the third output signal, the first output signal and the fourth output signal are not shown in the figures.

[0077] When the magnetic sensor 100 is at position L2, where it faces the center of the north magnetic pole 80 of the rotor 8, a magnetic field is applied to the magnetic sensor 100 along the positive direction of the X-axis. In this case, the fifth magnetic resistance element 211, the sixth magnetic resistance element 212, the seventh magnetic resistance element 221, and the eighth magnetic resistance element 222 do not detect the magnetic field. Because a bias magnetic field along the positive direction of the X-axis is applied to the first magnetic resistance element 111 and the third magnetic resistance element 121, the magnetic field of the rotor 8 and the bias magnetic field reinforce each other. On the other hand, because a bias magnetic field along the negative direction of the X-axis is applied to the second magnetic resistance element 112 and the fourth magnetic resistance element 122, the magnetic field of the rotor 8 and the bias magnetic field weaken each other. Therefore, when the magnetic sensor 100 is at position L2, the second output signal is minimum and the first output signal is maximum.

[0078] When the magnetic sensor 100 is at position L4, facing the center of the south pole magnetic pole 80 of the rotor 8, the direction of the magnetic field of the rotor 8 is opposite to that at position L2, so the second output signal is maximum and the first output signal is minimum (see Figure 7).

[0079] When the magnetic sensor 100 is at position L1, where it faces the boundary between the north and south magnetic poles 80 of the rotor 8, a magnetic field is applied to the magnetic sensor 100 in the negative direction of the Y axis. In this case, the first magnetic resistance element 111, the second magnetic resistance element 112, the third magnetic resistance element 121, and the fourth magnetic resistance element 122 do not detect the magnetic field. Because a bias magnetic field in the negative direction of the Y axis is applied to the sixth magnetic resistance element 212 and the eighth magnetic resistance element 222, the magnetic field of the rotor 8 and the bias magnetic field reinforce each other. On the other hand, because a bias magnetic field in the positive direction of the Y axis is applied to the fifth magnetic resistance element 211 and the seventh magnetic resistance element 221, the magnetic field of the rotor 8 and the bias magnetic field weaken each other. Therefore, when the magnetic sensor 100 is at position L1, the third output signal is maximized and the fourth output signal is minimized (see FIG. 7 ).

[0080] When the magnetic sensor 100 is at position L3, facing the boundary between the north pole magnetic pole 80 and the south pole magnetic pole 80 of the rotor 8, the direction of the magnetic field of the rotor 8 is opposite to that at position L1, so the third output signal is at a minimum and the fourth output signal is at a maximum (see Figure 7).

[0081] 4 and 7, the second output signal and the third output signal repeat the same waveforms every time the relative rotation angle between the magnetic sensor 100 and the rotor 8 changes by an amount corresponding to twice the width of the magnetic pole 80. In other words, the rotation angle corresponding to twice the width of the magnetic pole 80 corresponds to one period of the second output signal and the third output signal.

[0082] If the second output signal and the third output signal are each assumed to be a sine wave, the phase difference between the second output signal and the third output signal is a rotation angle corresponding to 1 / 2 the width of the magnetic pole 80. In other words, the phase difference is 1 / 4 period. Therefore, if the third output signal is assumed to be a sine wave, the second output signal corresponds to a cosine wave with respect to the third output signal.

[0083] The processing circuit 201 determines the rotation angle of the magnetic sensor 100 (actually, the rotor 8) based on the first output signal, the second output signal, the third output signal, and the fourth output signal. Specifically, the processing circuit 201 generates a first differential signal, which is a differential signal between the first output signal and the second output signal. The waveform of the first differential signal is a waveform with double the amplitude of the first output signal. Furthermore, the processing circuit 201 generates a second differential signal, which is a differential signal between the third output signal and the fourth output signal. The waveform of the second differential signal is a waveform with double the amplitude of the third output signal.

[0084] The processing circuit 201 determines a common phase of the first differential signal as a cosine wave and the second differential signal as a sine wave based on the first differential signal and the second differential signal. Every time the phase changes by one period, the processing circuit 201 can determine that the magnetic sensor 100 (actually, the rotor 8) has rotated by a rotation angle corresponding to one period. Because the first differential signal and the second differential signal have twice the amplitude of the first output signal and the third output signal, the direction of the magnetic field and the rotation angle of the magnetic sensor 100 (actually, the rotor 8) can be determined with higher accuracy.

[0085] The magnetic detection system 200 may include a sensor (for example, an optical sensor or a magnetic sensor) for detecting the starting point of the movement (rotation) of the measurement object (rotor 8). In this case, the sensor generates a predetermined output signal every time the measurement object makes one rotation, and the processing circuit 201 detects the starting point based on the predetermined output signal.

[0086] (4) Effects Figure 8 is a schematic diagram for explaining the effects achieved by the magnetic sensor 100 of this embodiment. Width X1 in the figure is the width of the neutral zone between two magnets 51 lined up in the third direction D3 (i.e., between the first magnet 511 and the third magnet 513, and between the second magnet 512 and the fourth magnet 514). Width Y1 in the figure is the width of the neutral zone between two magnets 51 lined up in the second direction D2 (i.e., between the first magnet 511 and the second magnet 512, and between the third magnet 513 and the fourth magnet 514). The overall outer shape of the bias magnet 5 is constant regardless of width X1 and width Y1.

[0087] Tables 1 to 4 below show the relationship between the size (mm) of width X1 and width Y1, the angle error amplitude (°), the bias magnetic field strength (mT), the differential sine output p-p (mV), and the differential cosine output p-p (mV). Tables 1 to 4 show the results of simulations performed by the applicant. The angle error amplitude is the difference between the rotation angle determined by the magnetic detection system and the actual rotation angle of the rotor (or magnetic sensor). The differential sine output p-p is the maximum value of the difference between the third output signal and the fourth output signal. The differential cosine output p-p is the maximum value of the difference between the first output signal and the second output signal.

[0088]

[0089]

[0090]

[0091]

[0092] As shown in Table 1, the smaller the width of the neutral zone, the smaller the angular error amplitude. In other words, the smaller the width of the neutral zone, the more accurate the detection of the magnetic sensor. In the magnetic sensor 100 of this embodiment, the width of the neutral zone between two magnets 51 aligned along the second direction D2 or the third direction D3 is almost zero, so the detection accuracy can be improved compared to conventional magnetic sensors. Furthermore, as shown in Table 2, the smaller the width of the neutral zone, the greater the strength of the bias magnetic field. Furthermore, as shown in Tables 3 and 4, the smaller the width of the neutral zone, the greater the output signal of the magnetic sensor 100.

[0093] In the magnetic sensor 100 according to the embodiment, the rotor magnetic field in the X-axis direction applied by the rotor 8 is represented as H Ｒｘ The rotor magnetic field in the Y-axis direction applied by the rotor 8 is H Ｒｙ The bias magnetic field in the X-axis direction applied by the bias magnet 5 is defined as H Ｂｘ The bias magnetic field in the Y-axis direction applied by the bias magnet 5 is H Ｂｙ In this case, the magnetic field H applied to each magnetoresistance element 300 is expressed by equation (1).

[0094]

[0095] In the following, an example will be described in which the third series circuit 21 is composed of the fifth magnetic resistance element 211 and the sixth magnetic resistance element 212. As described above, the rotor magnetic field applied to each magnetic resistance element 300 is a sine wave or a cosine wave. Therefore, the rotor magnetic field H in the X-axis direction applied to the fifth magnetic resistance element 211 is Ｒ５ｘ , the rotor magnetic field H in the Y-axis direction applied to the fifth magnetic resistance element 211 Ｒ５ｙ , the rotor magnetic field H in the X-axis direction applied to the sixth magnetic resistance element 212 Ｒ６ｘ , the rotor magnetic field H in the Y-axis direction applied to the sixth magnetic resistance element 212 Ｒ６ｙ are expressed as equations (2) to (5), respectively. ５ , u ６ is the amplitude.

[0096]

[0097]

[0098]

[0099]

[0100] Here, the bias magnetic field B applied to the fifth magnetoresistance element 211 ５ and the bias magnetic field B applied to the sixth magnetoresistance element 212 ６ If and are the same size and opposite in direction, B ５ =-B ６ The magnetic field H applied to the fifth magnetoresistance element 211 ５ , and the magnetic field H applied to the sixth magnetoresistance element 212 ６ According to equation (1), equations (6) and (7) are given.

[0101]

[0102]

[0103] Furthermore, if the x component can be ignored, the magnetic fields H5 and H6 are expressed by equations (8) and (9).

[0104]

[0105]

[0106] In addition, when the MR curve (magnetoresistance curve) of each magnetoresistance element 300 is approximated by a straight line, with a slope and b intercept, the resistance value R of the fifth magnetoresistance element 211 is ５ , and the resistance value R of the sixth magnetoresistive element 212 ６ are expressed as equations (10) and (11).

[0107]

[0108]

[0109] Here, the potential of the power supply terminal H10 is Vcc, and the potential of the connection point between the fifth magnetoresistance element 211 and the sixth magnetoresistance element 212, i.e., the potential of the third output signal output from the third output terminal 3T, is V1. In this case, the ratio of the potential V1 to the potential Vcc is given by equation (12).

[0110]

[0111] And the amplitude of the rotor magnetic field u ５ =u ６ In this case, the ratio of the potential V1 to the potential Vcc is given by equation (13).

[0112]

[0113] According to equation (13), it is possible to make the third output signal output from the third output terminal 3T closer to a cosine wave. Similarly, it is possible to make the fourth output signal output from the fourth output terminal 4T closer to a cosine wave. Furthermore, it is possible to make the first output signal output from the first output terminal 1T and the second output signal output from the second output terminal 2T closer to a sine wave. As a result, it is possible to reduce the angle error of the magnetic sensor 100 and improve detection accuracy.

[0114] As described above, it was assumed that the x component can be ignored in the process of deriving Equation (8) and Equation (9). In other words, in order to make the actual output signal of the magnetic sensor 100 a sine wave or a cosine wave, it is desirable that the contribution of the x component be as small as possible.

[0115] In the formula (6), if B5 is equal to or greater than a predetermined value, (H Ｒ５ｙ +B ５ ) ２ >(H Ｒ５ｘ ) ２ It becomes. B ５ The larger the rotor magnetic field H in the X-axis direction, Ｒ５ｘ This reduces the contribution of the sine wave and cosine wave of the output signal from the magnetic sensor 100.

[0116] As shown in Table 2, the smaller the width of the neutral zone between two magnets 51 aligned along the second direction D2 or the third direction D3, the stronger the bias magnetic field. In the magnetic sensor 100 of this embodiment, the width of the neutral zone between two magnets 51 aligned along the second direction D2 or the third direction D3 is almost zero, so the strength of the bias magnetic field can be increased. This reduces the contribution of the x component, allowing the output signal of the magnetic sensor 100 to approach a sine wave or cosine wave.

[0117] The amplitude of the output signal obtained by equation (13) is −au ２ / (2aB ５ +2b). In this embodiment, since the MR curve is assumed to be when the magnetic field is positive, a is a negative value. ５ The larger the value of , the larger the denominator, and the larger the amplitude of the output signal. As described above, the magnetic sensor 100 of this embodiment can increase the strength of the bias magnetic field. This allows the amplitude of the output signal of the magnetic sensor 100 to be increased.

[0118] (5) Manufacturing Method of Magnetic Sensor Next, a manufacturing method of the bias magnet 5 according to this embodiment will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a schematic diagram for explaining a magnetizing method of the bias magnet 5 provided in the magnetic sensor 100 according to this embodiment. Fig. 10 is a flowchart showing a manufacturing method of the bias magnet 5 used as part of the magnetic sensor 100 according to this embodiment.

[0119] The method for manufacturing the bias magnet 5 according to this embodiment is a method for manufacturing a bias magnet 5 used as part of the magnetic sensor 100. As shown in Fig. 10, the method for manufacturing the bias magnet 5 includes a generating step (step S1), a first bonding step (step S2), a second bonding step (step S3), a third bonding step (step S4), and a fourth bonding step (step S5).

[0120] In the generation step, a first magnet 511, a second magnet 512, a third magnet 513, and a fourth magnet 514 are generated by magnetizing multiple (one in the example of Figure 9) magnetic materials 500 (see Figure 9) in a first direction D1.

[0121] 9 shows an example of magnetizing a magnetic material 500 in a first direction D1 using a yoke 61. Here, the magnetic material 500 is, for example, a metal compound containing neodymium, iron, and boron as its main components. A coil 600 is wound around the yoke 61. Then, by passing a current through the coil 600, the magnetic material 500 is magnetized in the first direction D1, and a magnet 51 is generated.

[0122] In the first coupling step, the first magnet 511 and the second magnet 512 are coupled in the second direction D2 (see Figure 1) so that the north pole 50A of the first magnet 511 and the south pole 50B of the second magnet 512 are adjacent to each other, and so that the south pole 50B of the first magnet 511 and the north pole 50A of the second magnet 512 are adjacent to each other.

[0123] In the second joining step, the first magnet 511 and the third magnet 513 are joined in the third direction D3 (see Figure 1) so that the north pole 50A of the first magnet 511 and the south pole 50B of the third magnet 513 are adjacent to each other, and so that the south pole 50B of the first magnet 511 and the north pole 50A of the third magnet 513 are adjacent to each other.

[0124] In the third joining step, the third magnet 513 and the fourth magnet 514 are joined in the second direction D2 so that the north pole 50A of the third magnet 513 and the south pole 50B of the fourth magnet 514 are adjacent to each other, and the south pole 50B of the third magnet 513 and the north pole 50A of the fourth magnet 514 are adjacent to each other.

[0125] In the fourth joining step, the third magnet 513 and the fourth magnet 514 are joined in the third direction D3 so that the north pole 50A of the second magnet 512 and the south pole 50B of the fourth magnet 514 are adjacent to each other, and the south pole 50B of the second magnet 512 and the north pole 50A of the fourth magnet 514 are adjacent to each other.

[0126] As described above, by carrying out the series of processes shown in FIG. 10, the bias magnet 5 used as a part of the magnetic sensor 100 can be manufactured.

[0127] The flowchart shown in FIG. 10 is merely an example, and the order of the processes may be changed as appropriate, and processes may be added or deleted as appropriate.

[0128] (6) Modifications Modifications of the above embodiment are listed below.

[0129] The application of the magnetic sensor 100 is not limited to detecting the rotation angle of the detection target, but may also be used to detect linear movement of the detection target.

[0130] The power supply terminal H10 electrically connected to the first magnetoresistance element 111 and the power supply terminal H10 electrically connected to the sixth magnetoresistance element 212 may be separate terminals. Similarly, the power supply terminal H20 and the reference terminals L10 and L20 may be individually provided for each magnetoresistance element 300.

[0131] The magnetic sensor 100 may be disposed at, for example, position L41 (see FIG. 4 ). That is, the magnetic sensor 100 may be disposed at a position facing the rotor 8 in a direction parallel to the rotation axis of the rotor 8. In this case, the magnetic field applied to the magnetic sensor 100 rotates as the rotor 8 rotates, so that the magnetic field direction can be detected by the magnetic sensor 100. However, in this case, the direction of the magnetic field applied to the magnetic sensor 100 is perpendicular to the radial direction of the rotor 8, so it is necessary to adjust the orientation of the magnetic sensor 100 so that the Z axis set in the magnetic sensor 100 is aligned with the radial direction of the rotor 8.

[0132] In the above embodiment, the output circuit 3 of the magnetic sensor 100 includes the first full-bridge circuit 1 and the second full-bridge circuit 2. However, the output circuit 3 of the magnetic sensor 100 may include a first half-bridge circuit instead of the first full-bridge circuit 1, and a second half-bridge circuit instead of the second full-bridge circuit 2. The first half-bridge circuit and the second full-bridge circuit are circuits in which two magnetoresistance elements 300 are connected in series, and an output signal is output from the connection point of the two magnetoresistance elements.

[0133] (Summary) As is clear from the above-described embodiments and modifications, the magnetic sensor (100) according to the first aspect includes an output circuit (3) and a bias magnet (5). The output circuit (3) has a plurality of magnetoresistive elements (300) and outputs an output signal corresponding to the strength of a magnetic field applied to the plurality of magnetoresistive elements (300). The bias magnet (5) applies a bias magnetic field to the plurality of magnetoresistive elements (300). The bias magnet (5) has a first magnet (511), a second magnet (512), a third magnet (513), and a fourth magnet (514) magnetized in a first direction (D1). The first magnet (511) and the second magnet (512) are connected in a second direction (D2) perpendicular to the first direction (D1) so that the north pole (50A) of the first magnet (511) and the south pole (50B) of the second magnet (512) are adjacent to each other, and so that the south pole (50B) of the first magnet (511) and the north pole (50A) of the second magnet (512) are adjacent to each other. The first magnet (511) and the third magnet (513) are coupled in a third direction (D3) perpendicular to both the first direction (D1) and the second direction (D2) such that the north pole (50A) of the first magnet (511) and the south pole (50B) of the third magnet (513) are adjacent to each other and the south pole (50B) of the first magnet (511) and the north pole (50A) of the third magnet (513) are adjacent to each other. The third magnet (513) and the fourth magnet (514) are coupled in a second direction (D2) such that the north pole (50A) of the third magnet (513) and the south pole (50B) of the fourth magnet (514) are adjacent to each other and the south pole (50B) of the third magnet (513) and the north pole (50A) of the fourth magnet (514) are adjacent to each other. The second magnet (512) and the fourth magnet (514) are connected in the third direction (D3) so that the north pole (50A) of the second magnet (512) and the south pole (50B) of the fourth magnet (514) are adjacent to each other, and so that the south pole (50B) of the second magnet (512) and the north pole (50A) of the fourth magnet (514) are adjacent to each other.

[0134] According to this aspect, it is possible to improve the detection accuracy.

[0135] In the magnetic sensor (100) according to the second aspect, in the first aspect, the first magnet (511) is coupled to each of the second magnet (512) and the third magnet (513) by magnetic force while in contact with each other. The fourth magnet (514) is coupled to each of the second magnet (512) and the third magnet (513) by magnetic force while in contact with each other.

[0136] According to this embodiment, the neutral zone between two adjacent magnets can be almost eliminated.

[0137] The magnetic sensor (100) according to the third aspect is the magnetic sensor (100) according to the first or second aspect, further comprising a resin member (second protective film 75). The resin member covers the bias magnet (5).

[0138] In a magnetic sensor (100) according to a fourth aspect, in any one of the first to third aspects, the output circuit (3) includes a first full-bridge circuit (1) and a second full-bridge circuit (2). The first full-bridge circuit (1) includes a first series circuit (11) and a second series circuit (12). The first series circuit (11) includes a first magnetic resistance element (111) and a second magnetic resistance element (112) connected in series to each other and detecting a magnetic field along a third direction (D3). The second series circuit (12) includes a third magnetic resistance element (121) and a fourth magnetic resistance element (122) connected in series to each other and detecting a magnetic field along the third direction (D3). The first series circuit (11) and the second series circuit (12) are connected in parallel to each other. The second full-bridge circuit (2) includes a third series circuit (21) and a fourth series circuit (22). The third series circuit (21) includes a fifth magnetoresistive element (211) and a sixth magnetoresistive element (212) connected in series to each other and detecting a magnetic field along the second direction (D2). The fourth series circuit (22) includes a seventh magnetoresistive element (221) and an eighth magnetoresistive element (222) connected in series to each other and detecting a magnetic field along the second direction (D2). The third series circuit (21) and the fourth series circuit (22) are connected in parallel to each other.

[0139] In the magnetic sensor (100) according to the fifth aspect, in the fourth aspect, the bias magnet (5) applies bias magnetic fields in opposite directions along the third direction (D3) to the first magnetic resistance element (111) and the third magnetic resistance element (121) and the second magnetic resistance element (112) and the fourth magnetic resistance element (122). The bias magnet (5) applies bias magnetic fields in opposite directions along the second direction (D2) to the fifth magnetic resistance element (211) and the seventh magnetic resistance element (221) and the sixth magnetic resistance element (212) and the eighth magnetic resistance element (222).

[0140] The configurations other than the first aspect are not essential for the magnetic sensor (100) and can be omitted as appropriate.

[0141] A manufacturing method according to a sixth aspect is a method for manufacturing a bias magnet (5) used as part of the magnetic sensor (100) according to any one of the first to fifth aspects. The manufacturing method includes a generating step (step S1), a first bonding step (step S2), a second bonding step (step S3), a third bonding step (step S4), and a fourth bonding step (step S5). In the generating step, a first magnet (511), a second magnet (512), a third magnet (513), and a fourth magnet (514) are generated by magnetizing a plurality of magnetic materials (500) in a first direction (D1). In the first coupling step, the first magnet (511) and the second magnet (512) are coupled together in the second direction (D2) so that the north pole (50A) of the first magnet (511) and the south pole (50B) of the second magnet (512) are adjacent to each other and the south pole (50B) of the first magnet (511) and the north pole (50A) of the second magnet (512) are adjacent to each other. In the second coupling step, the first magnet (511) and the third magnet (513) are coupled together in the third direction (D3) so that the north pole (50A) of the first magnet (511) and the south pole (50B) of the third magnet (513) are adjacent to each other and the south pole (50B) of the first magnet (511) and the north pole (50A) of the third magnet (513) are adjacent to each other. In the third coupling step, the third magnet (513) and the fourth magnet (514) are coupled together in the second direction (D2) such that the north pole (50A) of the third magnet (513) and the south pole (50B) of the fourth magnet (514) are adjacent to each other and the south pole (50B) of the third magnet (513) and the north pole (50A) of the fourth magnet (514) are adjacent to each other. In the fourth coupling step, the third magnet (513) and the fourth magnet (514) are coupled together in the third direction (D3) such that the north pole (50A) of the second magnet (512) and the south pole (50B) of the fourth magnet (514) are adjacent to each other and the south pole (50B) of the second magnet (512) and the north pole (50A) of the fourth magnet (514) are adjacent to each other.

[0142] According to this aspect, it is possible to manufacture a bias magnet (5) that can improve the detection accuracy of the magnetic sensor (100).

[0143] The magnetic sensor and bias magnet manufacturing method of the present disclosure can improve the detection accuracy of the magnetic sensor, and thus the magnetic sensor and bias magnet manufacturing method of the present disclosure are industrially useful.

[0144] 1 First full bridge circuit 11 First series circuit 12 Second series circuit 100 Magnetic sensor 111 First magnetic resistance element 112 Second magnetic resistance element 121 Third magnetic resistance element 122 Fourth magnetic resistance element 2 Second full bridge circuit 21 Third series circuit 22 Fourth series circuit 211 Fifth magnetic resistance element 212 Sixth magnetic resistance element 221 Seventh magnetic resistance element 222 Eighth magnetic resistance element 3 Output circuit 300 Magnetic resistance element 5 Bias magnet 50A North pole 50B South pole 500 Magnetic material 511 First magnet 512 Second magnet 513 Third magnet 514 Fourth magnet 75 Second protective film (resin member) D1 First direction D2 Second direction D3 Third direction S1 Step (generation step) S2 Step (first bonding step) S3 Step (second bonding step) Step S4 (third bonding step) Step S5 (fourth bonding step)

Claims

1. An output circuit having a plurality of magnetic resistance elements, which outputs an output signal according to the strength of a magnetic field applied to the plurality of magnetic resistance elements; and a bias magnet which applies a bias magnetic field to the plurality of magnetic resistance elements, wherein the bias magnet has a first magnet, a second magnet, a third magnet, and a fourth magnet magnetized in a first direction, wherein the first magnet and the second magnet are coupled so that the north pole of the first magnet and the south pole of the second magnet are adjacent to each other and the south pole of the first magnet and the north pole of the second magnet are adjacent to each other in a second direction perpendicular to the first direction, and the first magnet and the third magnet are coupled so that the north pole of the first magnet and the south pole of the third magnet are adjacent to each other and the south pole of the first magnet and the north pole of the third magnet are adjacent to each other in a third direction perpendicular to both the first direction and the second direction, a magnetic sensor, wherein the third magnet and the fourth magnet are coupled such that the north pole of the third magnet and the south pole of the fourth magnet are adjacent to each other and the south pole of the third magnet and the north pole of the fourth magnet are adjacent to each other in the second direction; and the second magnet and the fourth magnet are coupled such that the north pole of the second magnet and the south pole of the fourth magnet are adjacent to each other and the south pole of the second magnet and the north pole of the fourth magnet are adjacent to each other in the third direction.

2. The magnetic sensor according to claim 1, wherein the first magnet is coupled to each of the second magnet and the third magnet by magnetic force while in contact with each other, and the fourth magnet is coupled to each of the second magnet and the third magnet by magnetic force while in contact with each other.

3. The magnetic sensor according to claim 1, further comprising a resin member covering the bias magnet.

4. The magnetic sensor according to claim 1, wherein the output circuit comprises a first full bridge circuit and a second full bridge circuit, the first full bridge circuit comprising: a first series circuit including a first magnetic resistance element and a second magnetic resistance element connected in series to each other and detecting a magnetic field along the third direction; and a second series circuit including a third magnetic resistance element and a fourth magnetic resistance element connected in series to each other and detecting a magnetic field along the third direction, the first series circuit and the second series circuit being connected in parallel to each other, and the second full bridge circuit comprising: a third series circuit including a fifth magnetic resistance element and a sixth magnetic resistance element connected in series to each other and detecting a magnetic field along the second direction; and a fourth series circuit including a seventh magnetic resistance element and an eighth magnetic resistance element connected in series to each other and detecting a magnetic field along the second direction, the third series circuit and the fourth series circuit being connected in parallel to each other.

5. A magnetic sensor as described in claim 4, wherein the bias magnet applies the bias magnetic field in mutually opposite directions along the third direction to the first magnetic resistance element and the third magnetic resistance element and the second magnetic resistance element and the fourth magnetic resistance element, and applies the bias magnetic field in mutually opposite directions along the second direction to the fifth magnetic resistance element and the seventh magnetic resistance element and the sixth magnetic resistance element and the eighth magnetic resistance element.

6. A manufacturing method of a bias magnet used as part of a magnetic sensor according to any one of claims 1 to 5, comprising: a generating step of generating the first magnet, the second magnet, the third magnet, and the fourth magnet by magnetizing a plurality of magnetic materials in the first direction; a first connecting step of connecting the first magnet and the second magnet so that the north pole of the first magnet and the south pole of the second magnet are adjacent to each other and the south pole of the first magnet and the north pole of the second magnet are adjacent to each other in the second direction; and a second connecting step of connecting the first magnet and the third magnet so that the north pole of the first magnet and the south pole of the third magnet are adjacent to each other and the south pole of the first magnet and the north pole of the third magnet are adjacent to each other in the third direction. a third joining step of joining the third magnet and the fourth magnet so that the north pole of the third magnet and the south pole of the fourth magnet are adjacent to each other in the second direction, and so that the south pole of the third magnet and the north pole of the fourth magnet are adjacent to each other in the third direction; and a fourth joining step of joining the third magnet and the fourth magnet so that the north pole of the second magnet and the south pole of the fourth magnet are adjacent to each other in the third direction, and so that the south pole of the second magnet and the north pole of the fourth magnet are adjacent to each other.

Images