Magnetic sensor and magnetic detection system

Abstract

To provide a magnetic sensor capable of improving the detection accuracy of magnetic field direction applied thereto.SOLUTION: A magnetic sensor 100 has at least one bias magnet 5, a first half-bridge circuit 1, a second half-bridge circuit 2, and a base material. One of a pair of the first half-bridge circuit 1 first magnetoresistive elements 1 P, 1Q, a bias magnetic field along the positive direction of the X axis is applied, and a bias magnetic field along the negative direction of the X-axis is applied to the other. To one of a pair of second magnetoresistive elements 2P, 2Q of the second half-bridge circuit 2, a bias magnetic field along the positive direction of the Y axis is applied, and the other is applied with a bias magnetic field along the negative direction of the Y-axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates generally to magnetic sensors and magnetic sensing systems, and more particularly to magnetic sensors and magnetic sensing systems that include at least one bias magnet. [Background technology]

[0002] The rotation angle detection sensor (magnetic sensor) described in Patent Document 1 is configured as follows: At least two pairs of GMR elements, each having a free magnetic layer and a pinned magnetic layer, are provided on a substrate. Each pair of GMR elements is connected in series, and a rotatable magnet is arranged facing the GMR elements, applying a saturation magnetic field to the GMR elements. The rotation angle of the magnet's rotation axis is detected by the change in resistance of the GMR element, which occurs due to the angle between the magnetization direction of the free magnetic layer, which follows the direction of the magnet's magnetic field lines, and the magnetization direction of the pinned magnetic layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-303536 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a magnetic sensor and a magnetic detection system that can improve the detection accuracy of the direction of a magnetic field applied to the magnetic sensor. [Means for solving the problem]

[0005] A magnetic sensor according to one embodiment of the present disclosure includes at least one bias magnet, a first half-bridge circuit, a second half-bridge circuit, and a substrate, wherein the at least one bias magnet generates a bias magnetic field along a positive direction of an X-axis, a bias magnetic field along a negative direction of the X-axis, a bias magnetic field along a positive direction of a Y-axis that is an axis perpendicular to the X-axis, and a bias magnetic field along the negative direction of the Y-axis. The first half-bridge circuit outputs a first output signal, the second half-bridge circuit outputs a second output signal, the third half-bridge circuit outputs a third output signal that is out of phase with the first output signal, and the fourth half-bridge circuit outputs a fourth output signal that is out of phase with the second output signal. The substrate includes the at least one bias magnet, the first half-bridge circuit, 、 the second half-bridge circuit , the third half-bridge circuit, and the fourth half-bridge circuit The first half-bridge circuit includes a pair of first magnetoresistive effect elements that are half-bridge connected to detect a magnetic field along the X-axis, and a connection point between the pair of first magnetoresistive effect elements. The aforementioned The second half-bridge circuit has a pair of second magnetoresistive effect elements connected in a half-bridge configuration to detect a magnetic field along the Y-axis, and a first output terminal that outputs a first output signal. The aforementioned and a second output terminal for outputting a second output signal. The third half-bridge circuit has a pair of third magnetoresistive elements connected in a half-bridge configuration to detect a magnetic field along the X-axis, and a third output terminal that outputs the third output signal from a connection point between the pair of third magnetoresistive elements. The fourth half-bridge circuit has a pair of fourth magnetoresistive elements connected in a half-bridge configuration to detect a magnetic field along the Y-axis, and a fourth output terminal that outputs the fourth output signal from a connection point between the pair of fourth magnetoresistive elements. One of the pair of first magnetoresistive effect elements the first magnetoresistive element and one of the pair of third magnetoresistive elements; The bias magnetic field is applied to the positive direction of the X-axis. the first magnetoresistive element and the other third magnetoresistive element The bias magnetic field along the negative direction of the X-axis is applied to one of the pair of second magnetoresistance effect elements. the second magnetoresistive element, and one fourth magnetoresistive element of the pair of fourth magnetoresistive elements; The bias magnetic field is applied to the positive direction of the Y-axis. the second magnetoresistive element and the other fourth magnetoresistive element The bias magnetic field is applied to the negative Y-axis. Both the one first magnetoresistance effect element and the one third magnetoresistance effect element are disposed on the positive side of the Y-axis from the center of the substrate. Both the other first magnetoresistance effect element and the other third magnetoresistance effect element are disposed on the negative side of the Y-axis from the center of the substrate. Both the one second magnetoresistance effect element and the one fourth magnetoresistance effect element are disposed on the positive side of the X-axis from the center of the substrate. Both the other second magnetoresistance effect element and the other fourth magnetoresistance effect element are disposed on the negative side of the X-axis from the center of the substrate.

[0006] A magnetic detection system according to one aspect of the present disclosure includes the magnetic sensor and a processing circuit, wherein the processing circuit determines the direction of a magnetic field applied to the magnetic sensor based on at least the first output signal and the second output signal. [Effects of the Invention]

[0007] The present disclosure has an advantage in that it is possible to improve the detection accuracy of the direction of a magnetic field applied to a magnetic sensor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view of a magnetic sensor according to an embodiment. [Figure 2] FIG. 2 is a plan view of the magnetic sensor in which the bias magnet is omitted. [Figure 3] FIG. 3 is a cross-sectional view of the magnetic sensor. [Figure 4] FIG. 4 is a schematic diagram showing the above magnetic sensor in use. [Figure 5] FIG. 5 is an equivalent circuit diagram of a first half-bridge circuit and a third half-bridge circuit of the magnetic sensor. [Figure 6] FIG. 6 is an equivalent circuit diagram of a second half-bridge circuit and a fourth half-bridge circuit of the magnetic sensor. [Figure 7] FIG. 7 is a cross-sectional view of a magnetoresistive element of the magnetic sensor. [Figure 8] FIG. 8 is an explanatory diagram showing an output signal of the magnetic sensor of the above embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A magnetic sensor and a magnetic detection system according to an embodiment will be described below with reference to the drawings. However, the embodiment described below is merely one of various embodiments of the present disclosure. The embodiment described below can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each figure described in the embodiment described below is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0010] (overview) As shown in FIG. 1, the magnetic sensor 100 of this embodiment includes at least one bias magnet 5, a first half-bridge circuit 1, a second half-bridge circuit 2, and a substrate 73 (see FIG. 3). The at least one 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, which is an axis perpendicular to the X-axis, and a bias magnetic field along the negative direction of the Y-axis. The substrate 73 supports the at least one bias magnet 5, the first half-bridge circuit 1, and the second half-bridge circuit 2. The first half-bridge circuit 1 includes a pair of first magnetoresistance effect elements 1P and 1Q connected in a half-bridge configuration to detect a magnetic field along the X-axis, and a first output terminal 1T that outputs a first output signal from a connection point between the pair of first magnetoresistance effect elements 1P and 1Q. The second half-bridge circuit 2 has a pair of second magnetoresistance effect elements 2P, 2Q connected in a half-bridge configuration to detect a magnetic field along the Y-axis, and a second output terminal 2T that outputs a second output signal from the connection point between the pair of second magnetoresistance effect elements 2P, 2Q. A bias magnetic field along the positive direction of the X-axis is applied to one of the pair of first magnetoresistance effect elements 1P, 1Q, and a bias magnetic field along the negative direction of the X-axis is applied to the other. A bias magnetic field along the positive direction of the Y-axis is applied to one of the pair of second magnetoresistance effect elements 2P, 2Q, and a bias magnetic field along the negative direction of the Y-axis is applied to the other.

[0011] According to this embodiment, the waveform of the first output signal outputted in accordance with the rotation of the magnetic field applied to the magnetic sensor 100 is close to an ideal sine wave, and the waveform of the second output signal is close to an ideal cosine wave. Therefore, it is possible to accurately determine the direction of the magnetic field applied to the magnetic sensor 100 based on the first output signal and the second output signal.

[0012] Furthermore, the first half-bridge circuit 1 and the second half-bridge circuit 2 are integrated into a single substrate 73. This eliminates the need to adjust the positional relationship between the first substrate and the second substrate, as opposed to a case where a first substrate on which the first half-bridge circuit 1 is mounted and a second substrate on which the second half-bridge circuit 2 is mounted are separately provided. This also prevents a decrease in the accuracy of detecting the direction of the magnetic field due to a misalignment of the positional relationship.

[0013] When the direction of the bias magnetic field or the direction in which the magnetoresistive element detects the magnetic field is said to be along the X-axis or Y-axis, the angular difference between the two is preferably 5 degrees or less.

[0014] In the following description, in addition to the X-axis and Y-axis, a Z-axis that is orthogonal to both the X-axis and Y-axis will also be used. The X-axis, Y-axis, and Z-axis are imaginary axes set on the magnetic sensor 100, and are not tangible components.

[0015] (detail) (1) Overall structure 1 to 3, the magnetic sensor 100 includes a second protective film 72, a bias magnet 5, a first protective film 71, a wiring layer W1, and a substrate 73. The wiring layer W1 includes a first half-bridge circuit 1, a second half-bridge circuit 2, a third half-bridge circuit 3, and a fourth half-bridge circuit 4. Note that only the wiring layer W1 and the bias magnet 5 are shown in FIG. 1, and only the wiring layer W1 is shown in FIG. 2.

[0016] The magnetic detection system 200 includes the magnetic sensor 100 and a processing circuit 201. The processing circuit 201 determines the direction of the magnetic field applied to the magnetic sensor 100 based on at least the first output signal and the second output signal.

[0017] In this embodiment, as an example, a case will be described in which the magnetic sensor 100 and the magnetic detection system 200 are used to determine the direction of the magnetic field generated from the rotor 8 of a motor (see FIG. 4), thereby determining the rotation angle of the rotor 8.

[0018] (2) Rotor 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 the north poles and south poles are alternately aligned. In FIG. 4, the plurality of magnetic poles 80 are aligned so that the north poles 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 just letters added for the purpose of explanation and are not actually attached. The same applies to the "N" and "S" displayed on the bias magnet 5 in FIGS. 1 and 3.

[0019] (3) Bias magnet As shown in FIGS. 1 and 3, the bias magnet 5 has a rectangular parallelepiped shape. The bias magnet 5 is a single member. For example, a permanent magnet or an electromagnet can be used as the bias magnet 5. The bias magnet 5 of this embodiment is a permanent magnet. The bias magnet 5 is, for example, a ferrite magnet or a neodymium magnet.

[0020] The bias magnet 5 has multiple (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.

[0021] That is, two sets of four magnetic poles 50 are provided, and in each set, the four magnetic poles 50 are provided on the same plane. The magnetic poles 50 belonging to different sets are provided 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.

[0022] 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.

[0023] (4) Base material 3, the base material 73 has a plate shape and is, for example, an alumina substrate.

[0024] (5) Wiring layer 3, the wiring layer W1 is formed on the surface of the base material 73. As a result, the base material 73 holds the wiring layer W1.

[0025] The wiring layer W1 of this embodiment includes a plurality of layers, which are electrically connected to each other via through holes.

[0026] As shown in FIG. 2, the wiring layer W1 includes a first half-bridge circuit 1, a second half-bridge circuit 2, a third half-bridge circuit 3, and a fourth half-bridge circuit 4.

[0027] The first half-bridge circuit 1 has a pair of first magnetoresistive elements 1P and 1Q and a first output terminal 1T.

[0028] The second half-bridge circuit 2 has a pair of second magnetoresistance effect elements 2P and 2Q and a second output terminal 2T.

[0029] As shown in FIG. 5, the third half-bridge circuit 3 has a pair of third magnetoresistance effect elements 3P and 3Q and a third output terminal 3T. The pair of third magnetoresistance effect elements 3P and 3Q are half-bridge connected. The pair of third magnetoresistance effect elements 3P and 3Q detect a magnetic field along the X-axis. The third output terminal 3T outputs a third output signal from the connection point between the pair of third magnetoresistance effect elements 3P and 3Q.

[0030] As shown in FIG. 6, the fourth half-bridge circuit 4 has a pair of fourth magnetoresistance elements 4P and 4Q and a fourth output terminal 4T. The pair of fourth magnetoresistance elements 4P and 4Q are half-bridge connected. The pair of fourth magnetoresistance elements 4P and 4Q detect a magnetic field along the Y-axis. The fourth output terminal 4T outputs a fourth output signal from the connection point between the pair of fourth magnetoresistance elements 4P and 4Q.

[0031] Hereinafter, the first magnetoresistive effect elements 1P, 1Q, the second magnetoresistive effect elements 2P, 2Q, the third magnetoresistive effect elements 3P, 3Q, and the fourth magnetoresistive effect elements 4P, 4Q may be referred to as magnetoresistive effect element Mr0. That is, the magnetic sensor 100 includes a plurality (eight) of magnetoresistive effect elements Mr0.

[0032] 2, the wiring layer W1 further includes power supply terminals H10 and H20 and reference terminals L10 and L20. The power supply terminals H10 and H20 are high-potential side terminals electrically connected to a high-potential side electric circuit of the power supply. The reference terminals L10 and L20 are low-potential side terminals electrically connected to a low-potential side 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.

[0033] A first terminal of the first magnetoresistive element 1P is electrically connected to the reference terminal L20. A second terminal of the first magnetoresistive element 1P is electrically connected to a first terminal of the first magnetoresistive element 1Q. A second terminal of the first magnetoresistive element 1Q is electrically connected to the power supply terminal H10. A first output terminal 1T is electrically connected to a connection point between the pair of first magnetoresistive elements 1P and 1Q.

[0034] A first terminal of the second magnetoresistance effect element 2P is electrically connected to a power supply terminal H10. A second terminal of the second magnetoresistance effect element 2P is electrically connected to a first terminal of the second magnetoresistance effect element 2Q. A second terminal of the second magnetoresistance effect element 2Q is electrically connected to a reference terminal L10. A second output terminal 2T is electrically connected to a connection point between the pair of second magnetoresistance effect elements 2P and 2Q.

[0035] A first terminal of the third magnetoresistive element 3P is electrically connected to the power supply terminal H20. A second terminal of the third magnetoresistive element 3P is electrically connected to a first terminal of the third magnetoresistive element 3Q. A second terminal of the third magnetoresistive element 3Q is electrically connected to the reference terminal L10. A third output terminal 3T is electrically connected to a connection point between the pair of third magnetoresistive elements 3P and 3Q.

[0036] A first terminal of the fourth magnetoresistance effect element 4P is electrically connected to the reference terminal L20. A second terminal of the fourth magnetoresistance effect element 4P is electrically connected to a first terminal of the fourth magnetoresistance effect element 4Q. A second terminal of the fourth magnetoresistance effect element 4Q is electrically connected to the power supply terminal H20. The fourth output terminal 4T is electrically connected to a connection point between the pair of fourth magnetoresistance effect elements 4P and 4Q.

[0037] 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, in Fig. 1 and Fig. 2, only the first output terminal 1T is shown as being connected to the processing circuit 201.

[0038] 1, 2, 4, 5, and 6, the shape of the magnetoresistive element Mr0 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 Mr0 and does not necessarily match the actual shape of the magnetoresistive element Mr0.

[0039] The electrical resistance value of the magnetoresistive element Mr0 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 Mr0 as a voltage signal. The magnetoresistive element Mr0 is insensitive to magnetic fields in a first direction (a direction along the long side in FIG. 1) and is sensitive to magnetic fields in a second direction (a direction along the short side in FIG. 1). The sensitivity of the magnetoresistive element Mr0 is greatest to magnetic fields in the second direction.

[0040] The pair of first magnetoresistance effect elements 1P, 1Q and the pair of third magnetoresistance effect elements 3P, 3Q are arranged so as to be sensitive to a magnetic field in a direction along the X-axis. The pair of first magnetoresistance effect elements 1P, 1Q and the pair of third magnetoresistance effect elements 3P, 3Q exhibit the same change in resistance value when a magnetic field in the positive direction of the X-axis is applied and when a magnetic field in the negative direction of the X-axis is applied, provided that the magnetic field magnitudes are the same.

[0041] The pair of second magnetoresistance effect elements 2P, 2Q and the pair of fourth magnetoresistance effect elements 4P, 4Q are arranged so as to be sensitive to a magnetic field in a direction along the Y axis. The pair of second magnetoresistance effect elements 2P, 2Q and the pair of fourth magnetoresistance effect elements 4P, 4Q exhibit the same change in resistance value when a magnetic field along the positive direction of the Y axis and a magnetic field along the negative direction of the Y axis have the same magnetic field magnitude.

[0042] When viewed from the direction of the Z axis, with the center of the magnetic sensor 100 as the reference, the magnetoresistive effect elements Mr0 are arranged as follows: The first magnetoresistive effect element 1P and the third magnetoresistive effect element 3P are arranged on the positive side of the Y axis from the center. The first magnetoresistive effect element 1Q and the third magnetoresistive effect element 3Q are arranged on the negative side of the Y axis from the center. The second magnetoresistive effect element 2P and the fourth magnetoresistive effect element 4P are arranged on the positive side of the X axis from the center. The second magnetoresistive effect element 2Q and the fourth magnetoresistive effect element 4Q are arranged on the negative side of the X axis from the center.

[0043] As described above, the Z coordinates of the four magnetic poles 50 shown in Fig. 1 are larger than the Z coordinates of the remaining four magnetic poles 50. In other words, of the multiple magnetic poles 50 of the bias magnet 5, the four magnetic poles 50 shown in Fig. 1 face the multiple magnetoresistive effect elements Mr0 and apply a bias magnetic field to the multiple magnetoresistive effect elements Mr0. In Fig. 1, the direction of the bias magnetic field is indicated by an arrow.

[0044] A bias magnetic field along the positive direction of the X-axis is applied to the first magnetoresistance effect element 1P and the third magnetoresistance effect element 3P, and a bias magnetic field along the negative direction of the X-axis is applied to the first magnetoresistance effect element 1Q and the third magnetoresistance effect element 3Q.

[0045] A bias magnetic field along the positive direction of the Y axis is applied to the second magnetoresistance effect element 2P and the fourth magnetoresistance effect element 4P, and a bias magnetic field along the negative direction of the Y axis is applied to the second magnetoresistance effect element 2Q and the fourth magnetoresistance effect element 4Q.

[0046] In this way, the single bias magnet 5 generates a bias magnetic field along the positive direction of the X axis and a bias magnetic field along the negative direction of the X axis. Furthermore, the single bias magnet 5 also generates 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.

[0047] The magnetoresistive element Mr0 is a GMR (Giant Magneto Resistance) element. More specifically, the magnetoresistive element Mr0 is a CIP (current in plane) type GMR element. As shown in FIG. 7, the magnetoresistive element Mr0 has a stacked portion 90 and an underlayer 93.

[0048] The laminated section 90 is formed by alternately laminating magnetic layers 91 containing NiFeCo as a component and non-magnetic layers 92 containing Cu as a component. Such a structure makes it possible to obtain a high-output magnetoresistance effect element Mr0. The number of layers in the laminated section 90 is, for example, 10 or more or 20 or more. The magnetic layers 91 are layers of a ferromagnetic material. The magnetic layers 91 are more easily magnetized than the non-magnetic layers 92. The non-magnetic layers 92 preferably contain only Cu.

[0049] As shown in FIG. 7, the magnetic sensor 100 includes a substrate layer 6. The substrate layer 6 is included in the wiring layer W1 (see FIG. 3). The substrate layer 6 includes a substrate 61 and a glaze layer 62. The glaze layer 62 is formed on the surface of the substrate 61. The glaze layer 62 includes a glass material such as amorphous glass. The glaze layer 62 is formed by printing a glass paste on the surface of the substrate 61 and firing the glass paste. A magnetoresistive effect element Mr0 is formed on the surface of the glaze layer 62.

[0050] The laminated portion 90 overlaps an underlayer 93. More specifically, the underlayer 93 is formed on the surface of the glaze layer 62 of the substrate layer 6, and the laminated portion 90 is formed on the surface of the underlayer 93. The underlayer 93 contains NiFeCr as a component. By providing the underlayer 93, a high-output magnetoresistive effect element Mr0 can be obtained. Furthermore, by providing the underlayer 93, the crystal grains of the magnetic layer 91 can be grown larger, thereby improving the heat resistance of the magnetoresistive effect element Mr0.

[0051] The magnetoresistive element Mr0 has no sensitivity in a predetermined direction, but has isotropic sensitivity in a direction intersecting the predetermined direction.

[0052] The bias magnet 5 applies a magnetic field (bias magnetic field) having an intensity equal to or less than half the anisotropic magnetic field of each of the plurality of magnetoresistive elements Mr0 to each of the plurality of (eight) magnetoresistive elements Mr0, including the pair of first magnetoresistive elements 1P, 1Q and the pair of second magnetoresistive elements 2P, 2Q, thereby suppressing distortion of the output waveform of each of the plurality of magnetoresistive elements Mr0.

[0053] (6) Protective film 3, the first protective film 71 covers the wiring layer W1. The bias magnet 5 is mounted on the surface of the first protective film 71. The second protective film 72 covers the bias magnet 5.

[0054] The first protective film 71 is made of, for example, a resin, a metal oxide such as Al2O3 (alumina), or a metal nitride. The second protective film 72 is made of, for example, a resin.

[0055] (7) Processing circuit The processing circuit 201 (see FIG. 1) includes 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 provided by being recorded on a non-transitory recording medium such as a memory card.

[0056] The processing circuit 201 determines the direction of the magnetic field applied to the magnetic sensor 100 based on the first output signal, the second output signal, the third output signal, and the fourth output signal. The first output signal, the second output signal, the third output signal, and the fourth output signal are signals output from the first output terminal 1T, the second output terminal 2T, the third output terminal 3T, and the fourth output terminal 4T, respectively. In other words, the first output signal, the second output signal, the third output signal, and the fourth output signal are signals output from the first half-bridge circuit 1, the second half-bridge circuit 2, the third half-bridge circuit 3, and the fourth half-bridge circuit 4, respectively.

[0057] 1 and 5, the first half-bridge circuit 1 and the third half-bridge circuit 3 have the same sensitivity direction of the magnetoresistive element Mr0 and the same direction of the applied bias magnetic field, but the relationship between the high potential side and the low potential side is opposite to each other. Therefore, the third output signal is a signal with an opposite phase to the first output signal.

[0058] 1 and 6, the second half-bridge circuit 2 and the fourth half-bridge circuit 4 have the same sensitivity direction of the magnetoresistive element Mr0 and the same direction of the applied bias magnetic field, but the relationship between the high potential side and the low potential side is opposite to each other. Therefore, the fourth output signal is a signal of opposite phase to the second output signal.

[0059] (8) Magnetic field direction detection 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.

[0060] Even if it is assumed that the magnetic sensor 100, rather than the rotor 8, 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, in the following, with reference to Fig. 4, it is assumed that the rotor 8 is fixed and the position of the magnetic sensor 100 changes in the order of positions L1, L2, L3, L4, and L5. The magnetic sensor 100 rotates around the rotor 8, and the X-axis and Y-axis also rotate accordingly.

[0061] At positions L1, L2, L3, L4, and L5, 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.

[0062] As the position of the magnetic sensor 100 changes in the order of positions L1, L2, L3, L4, and L5 (actually, as the rotor 8 rotates), the first output signal, second output signal, third output signal, and fourth output signal each change in a sine wave or cosine wave. FIG. 8 illustrates the waveform V1 of the first output signal and the waveform V2 of the second output signal. Since the third output signal is a signal with an opposite phase to the first output signal and the fourth output signal is a signal with an opposite phase to the second output signal, the third and fourth output signals are not illustrated. For convenience, FIG. 8 illustrates the multiple magnetic poles 80 in a linear fashion.

[0063] When the magnetic sensor 100 is at position L3 facing the center of the N-pole magnetic pole 80 of the rotor 8, a magnetic field is applied to the magnetic sensor 100 along the positive direction of the Y-axis. The pair of first magnetoresistance effect elements 1P, 1Q and the pair of third magnetoresistance effect elements 3P, 3Q do not detect the magnetic field. Because a bias magnetic field along the positive direction of the Y-axis is applied to the second magnetoresistance effect element 2P and the fourth magnetoresistance effect element 4P, 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 Y-axis is applied to the second magnetoresistance effect element 2Q and the fourth magnetoresistance effect element 4Q, the magnetic field of the rotor 8 and the bias magnetic field weaken each other.

[0064] Therefore, when the magnetic sensor 100 is at position L3, the second output signal is at a minimum and the fourth output signal is at a maximum.

[0065] When the magnetic sensor 100 is at positions L1 and L5 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 L3, so the second output signal is maximum and the fourth output signal is minimum.

[0066] When the magnetic sensor 100 is at position L2 facing 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 positive direction of the X-axis. The pair of second magnetoresistance effect elements 2P, 2Q and the pair of fourth magnetoresistance effect elements 4P, 4Q do not detect the magnetic field. Because a bias magnetic field in the positive direction of the X-axis is applied to the first magnetoresistance effect element 1P and the third magnetoresistance effect element 3P, 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 negative direction of the X-axis is applied to the first magnetoresistance effect element 1Q and the third magnetoresistance effect element 3Q, the magnetic field of the rotor 8 and the bias magnetic field destructively.

[0067] Therefore, when the magnetic sensor 100 is at position L2, the first output signal is at a maximum and the third output signal is at a minimum.

[0068] The rotor 8 has a plurality of boundary portions between the north and south magnetic poles 80 in the circumferential direction. When the magnetic sensor 100 is at position L4, which is next to position L2 and faces a boundary portion between the north and south magnetic poles 80, the direction of the magnetic field of the rotor 8 is opposite to that at position L2, so the first output signal is minimum and the third output signal is maximum.

[0069] 8, the first and second output signals repeat the same waveforms every time the relative rotation angle between the magnetic sensor 100 and the rotor 8 changes by an angle corresponding to twice the width of the magnetic pole 80. In other words, the angle corresponding to twice the width of the magnetic pole 80 corresponds to one period of the first and second output signals.

[0070] If the first output signal and the second output signal are each assumed to be a sine wave, the phase difference between the first output signal and the second 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 first output signal is assumed to be a sine wave, the second output signal corresponds to a cosine wave of the first output signal.

[0071] As an example, the processing circuit 201 determines a common phase of the first output signal as a sine wave and the second output signal as a cosine wave based on the first output signal and the second output signal. Each 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. In other words, each 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 twice the width of the magnetic pole 80. In this way, the processing circuit 201 can determine how much the magnetic sensor 100 (actually, the rotor 8) has rotated from the rotation angle of the starting point (i.e., the relative rotation angle).

[0072] Furthermore, the phases of the first output signal and the second output signal correspond to the direction of the magnetic field applied to the magnetic sensor 100. That is, the processing circuit 201 can determine the direction of the magnetic field applied to the magnetic sensor 100. More specifically, the processing circuit 201 can determine the direction of the magnetic field applied to the magnetic sensor 100 within the range of 0 to 360 degrees.

[0073] As another example, the processing circuit 201 determines the rotation angle of the magnetic sensor 100 (actually, the rotor 8) based on the third output signal and the fourth output signal in addition to the first output signal and the second output signal. Specifically, the processing circuit 201 generates a first differential signal, which is a differential signal between the first output signal and the third output signal. The waveform of the first differential signal is a waveform with double the amplitude of the first output signal. The processing circuit 201 also generates a second differential signal, which is a differential signal between the second output signal and the fourth output signal. The waveform of the second differential signal is a waveform with double the amplitude of the second output signal. The processing circuit 201 determines a common phase for the first differential signal as a sine wave and the second differential signal as a cosine 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. The first differential signal and the second differential signal have twice the amplitude of the first output signal and the second output signal, so 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.

[0074] The magnetic detection system 200 may include a sensor (for example, an optical sensor or a magnetic sensor) for detecting the starting point of movement (rotation) of the measurement object (rotor 8). For each rotation of the measurement object, the sensor generates a predetermined output signal, and the processing circuit 201 detects the starting point based on the predetermined output signal.

[0075] (Variation 1) The following describes Modification 1 of the embodiment. The same components as those in the embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[0076] In the embodiment, the case where the magnetic sensor 100 is disposed on the outer side in the circumferential direction of the rotor 8 has been described with reference to Fig. 4, but 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 as well, the magnetic field applied to the magnetic sensor 100 rotates as the rotor 8 rotates, and the magnetic sensor 100 can detect the direction of the magnetic field.

[0077] In this case, however, the orientation of the magnetic sensor 100 needs to be different from that of the embodiment. Since the direction of the magnetic field applied to the magnetic sensor 100 is perpendicular to the radial direction of the rotor 8, the orientation of the magnetic sensor 100 needs to be adjusted so that the Z axis set in the magnetic sensor 100 is aligned with the radial direction of the rotor 8.

[0078] (Other Modifications of the Embodiments) Other variations of the embodiment are listed below. The following variations may be implemented in appropriate combination. The following variations may also be implemented in appropriate combination with the above-described variation 1.

[0079] The application of the magnetic sensor 100 is not limited to detecting the rotation angle of a detection target, but may also be used to detect linear movement of a detection target.

[0080] The reference terminal L20 electrically connected to the first magnetoresistive element 1P and the reference terminal L20 electrically connected to the fourth magnetoresistive element 4P may be separate terminals. Similarly, the other reference terminals L10 and power supply terminals H10 and H20 may be individually provided for each magnetoresistive element Mr0.

[0081] The third half-bridge circuit 3 and the fourth half-bridge circuit 4 may be omitted from the magnetic sensor 100. In this case, the processing circuit 201 may determine the direction of the magnetic field applied to the magnetic sensor 100 by using the first output signal and the second output signal instead of the first differential signal which is the differential signal between the first output signal and the third output signal and the second differential signal which is the differential signal between the second output signal and the fourth output signal.

[0082] (summary) The above-described embodiments and the like disclose the following aspects.

[0083] A magnetic sensor (100) according to a first aspect includes at least one bias magnet (5), a first half-bridge circuit (1), a second half-bridge circuit (2), and a substrate (73). The at least one 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, which is an axis perpendicular to the X-axis, and a bias magnetic field along the negative direction of the Y-axis. The substrate (73) holds the at least one bias magnet (5), the first half-bridge circuit (1), and the second half-bridge circuit (2). The first half-bridge circuit (1) includes a pair of first magnetoresistance effect elements (1P, 1Q) connected in a half-bridge configuration to detect a magnetic field along the X-axis, and a first output terminal (1T) that outputs a first output signal from a connection point between the pair of first magnetoresistance effect elements (1P, 1Q). The second half-bridge circuit (2) has a pair of second magnetoresistance effect elements (2P, 2Q) connected in a half-bridge configuration to detect a magnetic field along the Y-axis, and a second output terminal (2T) that outputs a second output signal from a connection point between the pair of second magnetoresistance effect elements (2P, 2Q). A bias magnetic field along the positive direction of the X-axis is applied to one of the pair of first magnetoresistance effect elements (1P, 1Q), and a bias magnetic field along the negative direction of the X-axis is applied to the other. A bias magnetic field along the positive direction of the Y-axis is applied to one of the pair of second magnetoresistance effect elements (2P, 2Q), and a bias magnetic field along the negative direction of the Y-axis is applied to the other.

[0084] According to the above configuration, the waveform of the first output signal outputted in response to the rotation of the magnetic field applied to the magnetic sensor (100) is close to an ideal sine wave, and the waveform of the second output signal is close to an ideal cosine wave, so that the direction of the magnetic field applied to the magnetic sensor (100) can be accurately determined based on the first and second output signals.

[0085] In addition, in the magnetic sensor (100) according to the second aspect, in the first aspect, the at least one bias magnet (5) includes a single bias magnet (5) that generates a bias magnetic field along the positive direction of the X-axis and a bias magnetic field along the negative direction of the X-axis.

[0086] With the above configuration, compared to a case where a bias magnet that generates a bias magnetic field along the positive direction of the X-axis and a bias magnet that generates a bias magnetic field along the negative direction of the X-axis are separately provided, it is possible to reduce the angular error between the two bias magnetic fields, thereby reducing distortion in the waveform of the first output signal.

[0087] In addition, in the magnetic sensor (100) according to the third aspect, in the second aspect, the at least one bias magnet (5) includes a single bias magnet (5) that 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.

[0088] According to the above configuration, compared to a case where four bias magnets are provided corresponding to four bias magnetic fields, it is possible to reduce the angle error between the four bias magnetic fields, thereby reducing distortion of the waveforms of the first output signal and the second output signal.

[0089] In addition, in a magnetic sensor (100) according to a fourth aspect, in any one of the first to third aspects, at least one magnetoresistance effect element (Mr0) of the pair of first magnetoresistance effect elements (1P, 1Q) and the pair of second magnetoresistance effect elements (2P, 2Q) has a laminated portion (90) in which magnetic layers (91) containing NiFeCo as a component and non-magnetic layers (92) containing Cu as a component are alternately laminated.

[0090] According to the above configuration, it is possible to increase the output of the magnetoresistive element (Mr0).

[0091] In addition, in the magnetic sensor (100) according to the fifth aspect, in the fourth aspect, at least one magnetoresistance effect element (Mr0) has an underlayer (93) containing NiFeCr as a component and a laminate portion (90) overlapping the underlayer (93).

[0092] According to the above configuration, it is possible to increase the output of the magnetoresistive element (Mr0).

[0093] In addition, in a magnetic sensor (100) according to a sixth aspect, in any one of the first to fifth aspects, at least one bias magnet (5) applies a magnetic field having a strength equal to or less than half the anisotropic magnetic field of each of the plurality of magnetoresistive effect elements (Mr0) to each of the plurality of magnetoresistive effect elements (Mr0), including a pair of first magnetoresistive effect elements (1P, 1Q) and a pair of second magnetoresistive effect elements (2P, 2Q).

[0094] According to the above configuration, it is possible to reduce distortion in the waveforms of the first output signal and the second output signal.

[0095] In addition, the magnetic sensor (100) according to a seventh aspect is the magnetic sensor (100) of any one of the first to sixth aspects, further including a third half-bridge circuit (3) and a fourth half-bridge circuit (4). The third half-bridge circuit (3) outputs a third output signal having a phase opposite to that of the first output signal. The fourth half-bridge circuit (4) outputs a fourth output signal having a phase opposite to that of the second output signal.

[0096] According to the above configuration, by obtaining a differential output between the first output signal and the third output signal, it is possible to obtain an output that is approximately twice as large as that of the first output signal. Similarly, by obtaining a differential output between the second output signal and the fourth output signal, it is possible to obtain an output that is approximately twice as large as that of the second output signal. This makes it possible to more accurately determine the direction of the magnetic field based on the differential output.

[0097] The configurations other than those of the first aspect are not essential for the magnetic sensor (100) and can be omitted as appropriate.

[0098] A magnetic detection system (200) according to an eighth aspect includes the magnetic sensor (100) according to any one of the first to seventh aspects and a processing circuit (201). The processing circuit (201) determines the direction of the magnetic field applied to the magnetic sensor (100) based on at least the first output signal and the second output signal.

[0099] According to the above configuration, a magnetic detection system (200) having an integrated processing circuit (201) can be provided. [Explanation of symbols]

[0100] 1 First half-bridge circuit 1P, 1Q First magnetoresistive element 2 Second half-bridge circuit 2P, 2Q Second magnetoresistance element 3 Third half-bridge circuit 4. Fourth Half-Bridge Circuit 5 bias magnet 73 Base material 90 Laminated section 91 Magnetic layer 92 Nonmagnetic layer 93 Base layer 100 Magnetic Sensor 200 Magnetic Detection System 201 Processing circuit Mr0 magnetoresistive element 1T 1st output terminal 2T 2nd output terminal

Claims

1. at least one bias magnet that generates a bias magnetic field along a positive direction of an X-axis, a bias magnetic field along a negative direction of the X-axis, a bias magnetic field along a positive direction of a Y-axis that is an axis perpendicular to the X-axis, and a bias magnetic field along a negative direction of the Y-axis; a first half-bridge circuit that outputs a first output signal; a second half-bridge circuit that outputs a second output signal; a third half-bridge circuit that outputs a third output signal that is in opposite phase to the first output signal; a fourth half-bridge circuit that outputs a fourth output signal that is in opposite phase to the second output signal; a substrate that holds the at least one bias magnet, the first half-bridge circuit, the second half-bridge circuit, the third half-bridge circuit, and the fourth half-bridge circuit; The first half-bridge circuit comprises: a pair of first magnetoresistive elements connected in a half-bridge configuration to detect a magnetic field along the X-axis; a first output terminal that outputs the first output signal from a connection point between the pair of first magnetoresistive effect elements, The second half-bridge circuit is a pair of second magnetoresistive elements connected in a half-bridge configuration to detect a magnetic field along the Y-axis; a second output terminal that outputs the second output signal from a connection point between the pair of second magnetoresistive effect elements, The third half-bridge circuit is a pair of third magnetoresistance effect elements connected in a half-bridge configuration to detect a magnetic field along the X-axis; a third output terminal that outputs the third output signal from a connection point between the pair of third magnetoresistive effect elements, The fourth half-bridge circuit is a pair of fourth magnetoresistance effect elements connected in a half bridge configuration to detect a magnetic field along the Y-axis; a fourth output terminal that outputs the fourth output signal from a connection point between the pair of fourth magnetoresistive effect elements, the bias magnetic field along the positive direction of the X-axis is applied to one first magnetoresistive element of the pair of first magnetoresistive elements and one third magnetoresistive element of the pair of third magnetoresistive elements, and the bias magnetic field along the negative direction of the X-axis is applied to the other first magnetoresistive element and the other third magnetoresistive element; the bias magnetic field along the positive direction of the Y-axis is applied to one second magnetoresistive element of the pair of second magnetoresistive elements and one fourth magnetoresistive element of the pair of fourth magnetoresistive elements, and the bias magnetic field along the negative direction of the Y-axis is applied to the other second magnetoresistive element and the other fourth magnetoresistive element; both the one first magnetoresistive element and the one third magnetoresistive element are disposed on the positive side of the Y-axis from the center of the substrate, the other first magnetoresistive element and the other third magnetoresistive element are both disposed on the negative side of the Y-axis from the center of the substrate, both the one second magnetoresistance effect element and the one fourth magnetoresistance effect element are disposed on the positive side of the X-axis from the center of the substrate, both the other second magnetoresistance effect element and the other fourth magnetoresistance effect element are disposed on the negative side of the X-axis from the center of the substrate; Magnetic sensor.

2. the at least one bias magnet includes a single bias magnet that generates the bias magnetic field along a positive direction of the X-axis and the bias magnetic field along a negative direction of the X-axis. The magnetic sensor according to claim 1 .

3. the at least one bias magnet includes a single bias magnet that generates the bias magnetic field along the positive direction of the X-axis, the bias magnetic field along the negative direction of the X-axis, the bias magnetic field along the positive direction of the Y-axis, and the bias magnetic field along the negative direction of the Y-axis. The magnetic sensor according to claim 2 .

4. At least one of the pair of first magnetoresistive elements and the pair of second magnetoresistive elements has a laminated portion in which magnetic layers containing NiFeCo as a component and non-magnetic layers containing Cu as a component are alternately laminated. The magnetic sensor according to any one of claims 1 to 3.

5. the at least one magnetoresistive element has an underlayer containing NiFeCr as a component, and the laminated portion overlapping the underlayer; The magnetic sensor according to claim 4 .

6. the at least one bias magnet applies a magnetic field having an intensity equal to or less than half of an anisotropic magnetic field of each of the plurality of magnetoresistive elements to each of the plurality of magnetoresistive elements including the pair of first magnetoresistive elements and the pair of second magnetoresistive elements; The magnetic sensor according to any one of claims 1 to 5.

7. A magnetic sensor according to any one of claims 1 to 6, a processing circuit that determines the direction of a magnetic field applied to the magnetic sensor based on at least the first output signal and the second output signal. Magnetic detection system.

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