JP2006003116A - Magnetic sensor - Google Patents

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JP2006003116A
JP2006003116A JP2004177176A JP2004177176A JP2006003116A JP 2006003116 A JP2006003116 A JP 2006003116A JP 2004177176 A JP2004177176 A JP 2004177176A JP 2004177176 A JP2004177176 A JP 2004177176A JP 2006003116 A JP2006003116 A JP 2006003116A
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magnetic
magnetic sensor
axis
biaxial
sensor unit
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Osamu Shimoe
治 下江
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Hitachi Metals Ltd
日立金属株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-size three-axis magnetic sensor having high sensitivity with respect to direction detection, and having excellent mass productivity. <P>SOLUTION: This magnetic sensor has: a two-axis magnetic sensor part having a magnetoresistive effect element formed such that the magnetoresistive effect element has sensitivity in a plane direction including orthogonal two axes; a magnetic member provided in the two-axis magnetic sensor part such that the magnetic member projects from the plane including the orthogonal two axes, bending a magnetic component in a third axis direction orthogonal to the orthogonal two axes to the plane direction including the orthogonal two axes, and making the two-axis magnetic sensor part detect it; and a signal processing means detecting output in three-axis directions on the basis of a resistance value of the magnetoresistive effect element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic sensor, and more particularly to a magnetic sensor suitable for an orientation sensor that detects geomagnetism and detects an orientation.

  The direction sensor is a magnetic sensor that detects a geomagnetic direction based on the geomagnetism using a magnetosensitive element that detects magnetism. The geomagnetic direction is the horizontal direction of the geomagnetic vector with respect to the ground. Usually, the surface of one direction sensor is used as a reference, the geomagnetic component is detected in two axial directions parallel or perpendicular to the surface, and the geomagnetic direction is obtained from this. A biaxial magnetic sensor is used. However, if the reference surface of the azimuth sensor is tilted with respect to the ground for azimuth detection, the detected geomagnetic component changes according to the amount of variation, and the correct azimuth cannot be obtained. Actually, in Japan, the geomagnetism itself is not horizontal with respect to the ground surface, but is tilted over a range of 35 to 60 degrees (dip angle), and this tilt is also taken into account in order to determine the orientation from the geomagnetism. There is a need. In order to correct errors due to the inclination and dip of the azimuth sensor itself from the ground surface and detect a more accurate azimuth, it is only necessary to detect the geomagnetic component in three axial directions. A three-axis azimuth sensor using an element has been proposed.

The Hall element is a magnetosensitive element that detects a magnetic field component perpendicular to the element surface. The triaxial magnetic sensor described in Patent Document 1 has a Z-axis direction orthogonal to the surface on the surface of the support. Are arranged in the axial direction of each of the X axis and the Y axis orthogonal to each other in the surface, and a magnetic focusing plate is arranged in parallel to the support surface above the Hall element, The outer peripheral end is arranged in the vicinity of the Hall element. For this reason, the magnetic fluxes in the X-axis and Y-axis directions parallel to the support surface are converged by the magnetic focusing plate and spread in the Z-axis direction in the vicinity of the end of the magnetic focusing plate, and thus can be detected by the Hall element. At this time, for example, the pair of Hall elements arranged in the X-axis direction detects not only the magnetic flux in the X-axis direction but also the magnetic flux in the Z-axis direction, and the total amount is output. However, since the magnetic flux in the X-axis direction is detected as opposite Z-axis magnetic flux at both ends of the magnetic flux converging plate, the magnetic flux component in the Z-axis direction is canceled by taking the difference between the outputs of the pair of Hall elements. It is described that only the magnetic flux in the X-axis direction can be detected. Further, the magnetic flux in the Y-axis direction can be detected in the same manner, and the magnetic flux in the Z-axis direction can be detected by canceling the magnetic flux components in the X-axis and Y-axis directions by taking the sum of the outputs of all the Hall elements. It is explained.
JP 2003-172633 A (paragraph numbers 0029 to 0034)

  In order to mount the azimuth sensor in a mobile terminal device, it is required that the outer shape is small, the sensor has a sensitivity to detect geomagnetism, and can be mass-produced at low cost. The triaxial azimuth sensor disclosed in Patent Document 1 uses a Hall element as a magnetosensitive element, and the Hall element is excellent in miniaturization and mass productivity, but an output obtained for geomagnetism of 100 μT or less. The voltage is 1 mV or less, and since the semiconductor is used, there is noise 1 / f noise generated by the Hall element itself in addition to the thermal noise of the resistor, the detectable resolution is as low as mT, and the magnetic flux density of the geomagnetism is low. Considering that it is around 30 μT, it is difficult to measure geomagnetism with sufficient S / N, and it is insufficient in terms of detecting the direction with high accuracy. Further, in order to improve the SN ratio, which is a relative ratio to the geomagnetic signal to be detected, and to measure with high accuracy, random noise components may be averaged for a long time, but there is a problem that the measurement takes time.

  Accordingly, an object of the present invention is to provide a triaxial magnetic sensor that has sufficient sensitivity for azimuth detection, is small, and has excellent mass productivity.

In general, a magnetoresistive effect element is made of a thin film ferromagnetic material patterned on a substrate, and the electric resistance of the thin film changes depending on a magnetic field applied to the magnetoresistive effect element. The fraction R is expressed as R (θ) = ΔR · cos 2 θ, where θ is the angle between the magnetization direction of the thin film magnetic material and the current direction (ΔR is the maximum resistance change). The thickness of the metal thin film is usually several tens of nanometers, which is sufficiently smaller than the in-plane dimension (several tens of micrometers to several hundreds of micrometers), so that the magnetization is directed in the plane of the thin film. Since the current also normally flows in the plane direction, the magnetoresistive element has a characteristic that it has sensitivity to a magnetic field parallel to the plane and has no sensitivity in the direction perpendicular to the plane. Thus, a thinned two-axis magnetic sensor having in-plane sensitivity can be realized, and such a two-axis sensor has already been provided to the market. In addition, the magnetoresistive element has higher sensitivity than the Hall element, and not only can obtain an output of several mV with respect to geomagnetism, but also is made of a metal thin film, so that generated noise is small and high. Can detect geomagnetism. The inventor has intensively studied based on these technical backgrounds, and has completed the present invention.

  The present invention includes a two-axis magnetic sensor unit having a magnetoresistive effect element formed so as to have sensitivity in a plane direction including two orthogonal axes, and a two-axis magnetic sensor unit protruding from a plane including the two orthogonal axes. A magnetic member that is provided so as to be bent in a plane direction that includes the orthogonal two axes and that is detected by the two-axis magnetic sensor unit, and the magnetoresistive effect element And signal processing means for detecting outputs in the three-axis directions based on the resistance value.

  Furthermore, the present invention is characterized in that a second magnetic member is further provided on the side opposite to the magnetic member with the biaxial magnetic sensor portion interposed therebetween. The magnetic member is preferably a film body.

The biaxial magnetic sensor unit according to the present invention includes a planar coil having at least two pairs of parallel opposite sides, and four pairs of magnetoresistive effect element pairs formed on a plane parallel to the coil surface. The longitudinal direction of each of the two magnetoresistive effect elements in each of the two pairs of the resistive effect element intersects only the same one side of the opposite side pair of the planar coil, and each of the other two magnetoresistive effect elements. The longitudinal direction intersects only the opposite side of the one side of the opposite side pair, and the longitudinal direction of each of the two other magnetoresistive effect elements of the other two sets of the magnetoresistive effect element pair is the other opposite side. It intersects only with the same one side of the pair, and the longitudinal direction of each of the other two magnetoresistive elements intersects only with the opposite side of the one side of the other pair of opposite sides and intersects with the same side of the planar coil. Of the magnetoresistive elements Preferably it is in the non-parallel.
In the biaxial magnetic sensor unit according to the present invention, it is desirable that one terminal of each magnetoresistive element pair is connected, and an intermediate potential output taken out from the two terminals is input to the signal processing means.

  Furthermore, the present invention is characterized in that the assembly composed of the four pairs of magnetoresistive effect elements, the planar coil, and the magnetic member have a four-fold symmetry with respect to the center of the biaxial magnetic sensor unit. To do.

  The basic structure of the magnetic sensor of the present invention is composed of a biaxial sensor portion having a magnetoresistive effect element formed in a plane and a magnetic member for guiding a magnetic field perpendicular to the plane in the plane direction. A highly accurate three-axis magnetic sensor is realized. In particular, when mounted on a portable terminal or portable electronic device that uses map information as an azimuth sensor, the azimuth can be detected with high accuracy regardless of the orientation of the mounted device itself and the measurement location.

  The magnetic sensor of the present invention includes a two-axis magnetic sensor unit that detects magnetism in two orthogonal (X, Y) directions on one surface using a magnetoresistive effect element having sensitivity in the in-plane direction, and a two-axis magnetic sensor unit. The biaxial magnetic sensor is provided so as to protrude from a plane including the two orthogonal axes, and a magnetic component in a third axis direction (Z direction) orthogonal to the orthogonal two axes is bent in a plane direction including the two orthogonal axes. A magnetic member to be detected by the unit is provided, a change in the resistance value of the magnetoresistive effect element is processed, and a magnetic component is detected in three axial directions. That is, since the magnetic component in the third axis direction is converged by the magnetic member, the magnetic component that was originally in the third axis direction is bent near the end of the magnetic member, and the component in the biaxial (X, Y) direction is changed. This component is detected by the biaxial magnetic sensor unit. This makes it possible to configure a triaxial magnetic sensor without requiring a new magnetic sensor unit other than the biaxial magnetic sensor unit.

Further, by providing a second magnetic member on the opposite side of the magnetic member across the biaxial magnetic sensor unit, the magnetic component in the third axial direction is more effectively guided to the biaxial magnetic sensor unit and detected. Can be made. In this case, by arranging the magnetic member and the second magnetic member so as to be shifted in the biaxial plane direction, the magnetic component in the third axis direction can be more easily directed in the biaxial plane direction.
Hereinafter, the combination and configuration of the biaxial sensor unit and the magnetic member will be specifically described based on the embodiment. In the following description, the magnetoresistive element is abbreviated as MR element.

  (First Embodiment) FIG. 1 is an external view of an orientation sensor for explaining one embodiment of the present invention. A biaxial magnetic sensor unit 10 that detects geomagnetic components in two axial (X, Y axis) directions set so as to be orthogonal to each other and parallel to the surface of the substrate 13, and includes the two axes arranged on the biaxial magnetic sensor unit. And a magnetic member 1 that collects a magnetic field perpendicular to the surface (Z-axis). The magnetic member 1 is fixed to a protective insulating film 12 formed on the surface of the biaxial magnetic sensor unit with, for example, an epoxy adhesive, and the surface is coated with a rust preventive coating. The magnetic member 1 is positioned so as to have a predetermined positional relationship described later with respect to a plurality of MR elements R (see FIG. 4) disposed in the biaxial magnetic sensor unit 10, and is collected by the magnetic member 1. The magnetic flux is guided to the two-axis magnetic field sensor unit 10 and separated into three-axis geomagnetic components by an amplification detection circuit and output.

  First, the biaxial magnetic sensor unit 10 according to the magnetic sensor of the present invention will be described in detail. The biaxial magnetic sensor unit 10 includes an MR element R as a magnetosensitive element and a planar coil C that applies a bias magnetic field to the MR element R, and a semiconductor manufacturing process or the like is performed on a wafer-like silicon substrate. After forming a large number, it is preferable to separate them into individual biaxial magnetic sensor units 10. In the biaxial magnetic sensor unit 10, the MR element R is formed on the surface portion of the substrate 13, and the planar coil C is formed thereon via an insulating film. For example, the size of the substrate is 2 mm × 2 mm in length and width, thickness The thickness of thin film portions such as the formed MR element R and planar coil C is 0.1 to 10 μm. FIG. 2 is a developed perspective view showing the relationship between the MR element R and the planar coil C. FIG.

  In FIG. 2, a planar coil C is produced by a thin film process, and is a planar coil having at least two pairs of parallel opposite sides (here, a square) and wound several tens of times. On the surface opposed to the planar coil surface, four substantially trapezoidal magnetoresistive element pairs (eight MR elements R) are arranged such that the outer dimension of the planar coil C is radially divided into eight equal parts. An MR element assembly is formed. One MR element is preferably a meandering pattern. The longer part of the zigzag is the magnetic sensing part, and each of the eight MR elements is arranged so that the longitudinal direction of the magnetic sensing part is substantially radial. As shown in FIG. 2, when the directions along the sides of the planar coil C or the MR element assembly are the X-axis and Y-axis directions, the eight MR elements are considered to be a pair of MR elements facing opposite sides. Then, two MR element pairs (Rx1, Rx2), (Rx3, Rx4) in the X-axis direction and two MR element pairs (Ry1, Ry2), (Ry3, Ry4) in the Y-axis direction are obtained.

  Here, the arrangement and electrical connection of the MR elements will be described based on the two MR element pairs (Rx1, Rx2) and (Rx3, Rx4) in the X-axis direction. The longitudinal direction (hereinafter simply referred to as the longitudinal direction) of each MR element Rx1 and Rx4 of each of the two MR element pairs is 45 degrees with only one side C11 of the opposite side pair of the planar coil C. Intersect at an angle. The longitudinal direction of the other MR element Rx2, Rx3 intersects only one side of the opposite side of the planar coil C, that is, only the side C12 at an angle of 45 degrees. The longitudinal directions of the magnetoresistive elements Rx1, Rx4 (Rx2, Rx3) intersecting the same side C11 (C12) of the planar coil are non-parallel, and are orthogonal in the example of FIG. Further, the longitudinal direction of the MR element Rx1, the longitudinal direction of the MR element Rx2, the longitudinal direction of Rx3, and the longitudinal direction of Rx4 are both non-parallel, and are orthogonal in the example of FIG. One end portions of these MR elements Rx1 and Rx2 and one end portions of Rx3 and Rx4 (the end portion on the inner side of the MR element assembly in FIG. 2) are connected, and the MR elements Rx1 and Rx3 are connected to each other. The other end (the end on the outside of the MR element assembly in FIG. 2) is connected to the power supply (Vcc), and the other end of the MR elements Rx2 and Rx4 (the outside of the MR element assembly in FIG. 2) Is connected to a ground terminal (GND). That is, MR element Rx1 and MR element Rx2 and MR element Rx3 and MR element Rx4 are connected in series. In this embodiment, the crossing angle between the longitudinal direction of the MR element and one side of the opposite side of the coil is 45 degrees, but it may be larger than 30 degrees and within 90 degrees.

  For other MR element pairs, the MR elements are arranged and connected in the same manner as described for the MR element pairs (Rx1, Rx2) and (Rx3, Rx4). That is, the longitudinal direction of each MR element Ry1, Ry4 of the MR element pair is only one side C13 of the opposite side pair of the planar coil C, and the longitudinal direction of each other MR element Ry2, Ry3 is the opposite side of the planar coil C. It intersects with only one side C14 of the pair at an angle of 45 degrees. The longitudinal directions of the magnetoresistive elements Ry1, Ry4 (Ry2, Ry3) intersecting the same side C13 (C14) of the planar coil are non-parallel, and are orthogonal in the example of FIG. The longitudinal directions of the MR elements Ry1 and Ry3 are not parallel to the longitudinal directions of the corresponding MR elements Ry2 and Ry4 of the MR element pair, and are orthogonal in the example of FIG. Also, one end of MR elements Ry1 and Ry2 (the end inside MR element assembly in FIG. 2), and one end of MR elements Ry3 and Ry4 (inside MR element assembly in FIG. 2) Each end portion is connected to each other, and the MR element pairs (Ry1, Ry2) and (Ry3, Ry4) are respectively connected in series.

  FIG. 3 shows a schematic diagram of the electrical structure of the biaxial magnetic sensor unit 10 shown in FIG. As can be understood from FIG. 2, when a DC current is passed through the planar coil C, a DC magnetic field is generated on the surface parallel to the planar coil surface from the inside of the coil to the outside or from the outside to the inside. A DC bias magnetic field is applied to the element. By applying a DC bias, the operating point of the MR element can be set in a region sensitive to a magnetic field. In particular, from the viewpoint of obtaining high sensitivity, the angle between the longitudinal direction of the MR element and the bias magnetic field direction is preferably about 45 degrees. As shown in FIG. 3, when a clockwise current Ic flows through the planar coil C, a magnetic field in the + X direction is applied to the MR elements Rx1 and Rx4, and a magnetic field in the -X direction is applied to the MR elements Rx2 and Rx3. An axial geomagnetic component can be detected. Further, a magnetic field in the + Y direction is applied to the MR elements Ry1 and Ry4, and a magnetic field in the -Y direction is applied to the MR elements Ry2 and Ry3, so that the geomagnetic component in the Y-axis direction can be detected.

Here, the reset is a negative current, the bias is a positive current, and the resistance values of the eight MR elements Rx1 to Rx4 and Ry1 to Ry4 are rx1 to rx4 and ry1 to ry4. However, it demonstrates in detail. The respective resistance values can be changed in the linear region of the MR element appropriately biased with respect to the biaxial external magnetic fields Hx and Hy as follows. The resistance values at the operating points (only bias magnetic field) of the eight MR elements were all set equal to r0.
rx1 = r0−Kx × Hx + Ky × Hy
rx2 = r0 + Kx × Hx + Ky × Hy
rx3 = r0 + Kx × Hx−Ky × Hy
rx4 = r0−Kx × Hx−Ky × Hy
ry1 = r0 + Kx × Hx−Ky × Hy
ry2 = r0 + Kx × Hx + Ky × Hy
ry3 = r0−Kx × Hx + Ky × Hy
ry4 = r0−Kx × Hx−Ky × Hy

By inputting the two outputs from the X-axis bridge, that is, the intermediate potential outputs Vx + and Vx of the magnetoresistive effect element pairs rx1 / rx2 and rx3 / rx4 to the signal processing means and calculating them, the following can be easily performed. An output corresponding to the magnetic component in the X-axis direction can be obtained. An amount proportional to the voltage X1 obtained by amplifying the difference between the intermediate potential outputs Vx + and Vx is obtained by the following equation.
X1αVx + -Vx -
∝ (rx2-rx1)-(rx4-rx3)
= (Kx × Hx + Ky × Hy + Kx × Hx−Ky × Hy)
− (− Kx × Hx−Ky × Hy−Kx × Hx + Ky × Hy)
= (2 * Kx * Hx)-(-2 * Kx * Hx)
= 4 x Kx x Hx
Similarly, an amount proportional to the output from the Y-axis bridge is obtained as follows.
Y1αVy + -Vy -
∝ (ry2-ry1)-(ry4-ry3)
= 4 x Ky x Hy
As described above, by configuring the two-axis magnetic sensor unit according to the present invention, the output corresponding to each axis can be independently generated from the output terminals for the X and Y axes using the intermediate potential output of the magnetoresistive effect element pair. Obtainable. When this operation is performed by inverting the pulsed reset current and bias current, a signal component output with the sign reversed can be obtained from the bridge. By taking the difference between the two measurement outputs, the DC offset and noise can be reduced, and the signal output can be doubled.

  Next, the magnetic member 1 that collects a magnetic field perpendicular to the magnetic sensitive surface of the biaxial magnetic sensor unit 10 (Z axis) and guides it to the biaxial magnetic sensor unit will be described. The magnetic member 1 is a means for efficiently collecting the geomagnetic component in the Z-axis direction and bending it in the XY direction, and is attached so as to protrude in the Z-axis direction as shown in FIG. And has a flat or curved end surface in which the magnetic flux density in the Z-axis direction component is the highest. As shown in FIG. 7, when the magnetic field is in the direction of the arrow, the upper end surface 1 a opened in the Z-axis direction becomes a part that collects the magnetic field in the Z-axis direction, or the surface of the biaxial magnetic sensor unit 10 or the substrate constituting it. The lower end surface 1b attached to the surface of 13 serves as a portion for releasing the magnetic field collected on the upper end surface 1a to the biaxial magnetic sensor unit side. The lower end surface 1b may be parallel to the surface of the biaxial magnetic sensor unit 10 or the surface of the substrate 13 constituting the biaxial magnetic sensor unit 10, and faces the surface direction of the MR element R constituting the biaxial magnetic field sensor unit 10. You may form as follows. In short, any shape that effectively guides the lines of magnetic force to the MR element R may be used.

  The magnetic member 1 is preferably made of a ferromagnetic material having a high magnetic permeability. For example, in addition to oxide magnetic materials and iron-based magnetic materials, permalloy, soft magnetic amorphous materials, nanocrystalline soft magnetic materials, and the like may be used in the form of foil, thin wire, ribbon, or thin plate.

  The magnetic member 1 has a cross-shaped cross section substantially parallel to the surface of the biaxial magnetic sensor unit 10 or the surface of the substrate 13 and has four rotational symmetry axes. For example, the cross-shaped magnetic member 1 can be assembled by laminating high magnetic permeability thin plates, or a cross-shaped cross-shaped bar or wire can be cut to an appropriate length, or a high-permeability material can be formed on the surface of the cross-shaped substrate. This film can be formed by depositing the film by a film forming method such as plating, or by attaching a foil or a thin high magnetic permeability material to the surface of the cross-shaped substrate. If the magnetic member as a whole exhibits the function of collecting magnetism, the substrate may be made of a non-magnetic or low-permeability material. It is desirable that the magnetic member is composed of only a high permeability material. In particular, the manufacturing process can be simplified and a low-profile magnetic sensor can be configured by using the magnetic member as a film body produced by film forming means such as sputtering or plating.

  Although the height (projection height in the Z-axis direction) h of the magnetic member 1 is exaggerated in FIGS. 1 and 7, it is about 500 μm. In the case of a smaller and lower-profile magnetic sensor, it is advantageous that the height of the magnetic member is lower, and in that case, it is preferably 10 μm or less. The cross-sectional area (thickness t × length s) in the cross-shaped cross section is appropriately set according to the size of the MR element assembly. However, the magnetic component in the third axis (Z) direction can be efficiently converted into two magnetic sensor units. From the viewpoint of leading to the above, it is preferable that the thickness t is in a range in which one cross-shaped wing portion does not protrude from one MR element.

  As described above, the magnetic sensor according to the first embodiment has a configuration in which the cross-shaped magnetic member 1 is disposed on the biaxial magnetic sensor unit 10 via the protective insulating film 12. FIG. 4 is a diagram showing a planar arrangement of the MR element R and the magnetic member 1 in the biaxial magnetic sensor unit 10 described above, and FIG. 5 shows an amplifier for adding and subtracting the output from the MR element to increase the amplitude. It is a circuit connection diagram. As shown in FIG. 4, the magnetic member 1 has the center of the cross substantially coincided with the center of the MR element assembly of the biaxial magnetic sensor unit 10, and the cross wings (fins) are angled from the X and Y axes. It is arranged by rotating φ. The angle φ is larger than 0 degree and less than 45 degrees, but it is desirable to set it to about 23 degrees in the middle. Furthermore, the same applies when an integer multiple of 45 degrees is added in consideration of symmetry. Therefore, the cross-shaped wings (fins) of the magnetic member 1 are arranged on every other four MR elements (rx1, ry4, rx3, ry2: first magnetosensitive element), and the other four MR elements. Fins are not disposed on (ry1, rx2, ry3, rx4: second magnetosensitive element). That is, the first magnetosensitive element receives a large magnetic field from the magnetic member 1 and the magnetic field received by the second magnetosensitive element from the magnetic member 1 is smaller than the first magnetosensitive element. In addition, with respect to either one of the first magnetosensitive element or the second magnetosensitive element, the direction of the zigzag is changed so that the longitudinal direction of the magnetosensitive part is substantially perpendicular to the center, It is also possible to change the sensitivity of the first magnetosensitive element and the second magnetosensitive element to the Z-axis direction magnetic field component. In addition, since the first magnetosensitive element and the second magnetosensitive element are alternately arranged adjacent to each other, it is possible to perform measurement with higher accuracy by canceling noise of the measurement signal. Further, as shown in FIGS. 2 and 4, the MR element assembly and the planar coil are shaped to have a 4-fold symmetry with respect to the center of the biaxial magnetic sensor portion in the X and Y plane directions, and the magnetic member is similarly 4 By adopting a shape having rotational symmetry, it is possible to easily calculate and detect the magnetic component in the Z-axis direction in addition to the X and Y axes as shown below. In addition to the cross shape, for example, a square or the like can be used as the shape of the magnetic member having fourfold symmetry.

Next, a method for detecting the geomagnetic component in the triaxial direction will be described with reference to FIGS.
In the magnetic sensor having the above structure, the magnetic lines of force are bent in the vicinity of the magnetic member 1, and the magnetoresistive element causes a resistance change even with respect to the Z-axis magnetic field Hz. The resistance values of the first magnetosensitive element and the second magnetosensitive element are different depending on the difference in distance from the cross magnetic body. Here, for the sake of simplicity, the four MR elements of the first magnetosensitive element are used. Assuming that only the four MR elements of the second magnetosensitive element are not affected, the resistance change occurs in each MR element as follows. As is clear from the symmetry of the cross shape, the same conclusion can be obtained if there is a difference in sensitivity coefficient with respect to Hz.
rx1 = r0−Kx × Hx + Ky × Hy−Kz × Hz
rx2 = r0 + Kx × Hx + Ky × Hy
rx3 = r0 + Kx × Hx−Ky × Hy−Kz × Hz
rx4 = r0−Kx × Hx−Ky × Hy
ry1 = r0 + Kx × Hx−Ky × Hy
ry2 = r0 + Kx × Hx + Ky × Hy−Kz × Hz
ry3 = r0−Kx × Hx + Ky × Hy
ry4 = r0−Kx × Hx−Ky × Hy−Kz × Hz

Based on FIG. 5, the output of each axis is obtained in the same manner as in the case of the two axes described above.
X1αVx + -Vx with respect to 1) X-axis -
∝ (rx2-rx1)-(rx4-rx3)
= (Kx × Hx + Ky × Hy + Kx × Hx−Ky × Hy + Kz × Hz)
− (− Kx × Hx−Ky × Hy−Kx × Hx + Ky × Hy−Kz × Hz)
= 4 x Kx x Hx
Y1αVy + -Vy respect 2) Y-axis -
∝ (ry2-ry1)-(ry4-ry3)
= (Kx * Hx + Ky * Hy-Kz * Hz-Kx * Hx + Ky * Hy)
− (− Kx × Hx−Ky × Hy−Kz × Hz + Kx × Hx−Ky × Hy)
= 4 x Ky x Hy
3) Z1αVz + -Vz to the Z-axis -
∝ (rx2 + rx4-rx1-rx3)-(ry2 + ry4-ry1-ry3)
= (Kx * Hx + Ky * Hy-Kx * Hx-Ky * Hy + Kx * Hx-Ky * Hy
+ Kz × Hz-Kx × Hx + Ky × Hy + Kz × Hz)
− (Kx × Hx + Ky × Hy−Kz × Hz−Kx × Hx−Ky × Hy−Kz × Hz
−Kx × Hx + Ky × Hy + Kx × Hx−Ky × Hy)
= (+ Kz × Hz + Kz × Hz) − (− Kz × Hz−Kz × Hz)
= 4 x Kz x Hz
As described above, it is understood that independent outputs can be obtained for the Z axis as well as the X axis and the Y axis. In this way, the intermediate potential outputs of the four pairs of magnetoresistive effect element pairs are input to the signal processing means and operated, so that the number of elements and the number of terminals can be increased by two bridges without adding one amplifier, and 3 The magnetic field of the shaft can be detected.

  A magnetic sensor having the structure of the above-described embodiment using a planar coil and a four-axis magnetic sensor unit having four meander-like MR elements and a magnetic member was prototyped, and the three-axis magnetic field detection performance was evaluated. The magnetic member 1 is formed of a nanocrystalline soft magnetic material (Finemet (registered trademark) made by Hitachi Metals) having a thickness t of 10 μm in a cross shape having a side length s of 500 μm and a height h of 400 μm. . A permalloy film was used for the MR element. FIG. 6 shows an example of the output voltage from the X1, Y1, and Z1 axis amplifiers shown in FIG. FIG. 6A is a diagram showing outputs appearing on the respective axes X1, Y1, and Z1 when a magnetic field is applied in the X-axis direction. FIGS. 6B and 6C are diagrams showing outputs appearing on the respective axes X1, Y1, and Z1 when a magnetic field is similarly applied to the Y-axis or the Z-axis. In either case, it can be seen that the output of the magnetic field application axis is obtained almost independently from the other axes. Note that it is possible to obtain a more accurate output by performing a mathematical operation to eliminate unnecessary components from unnecessary axes. Note that a magnetic sensor using a cubic ferrite magnetic body having a side of 500 μm as a magnetic member and having a corner portion set in the same direction as one side of the cross shape was also prototyped and evaluated. It was confirmed that it functions as a three-axis magnetic sensor that also detects a magnetic field in the Z-axis direction.

  (Second Embodiment) The magnetic sensor of the second embodiment shown in FIG. 8 is a magnetic member (hereinafter referred to as a first magnetic member) 1 provided in the magnetic sensor of the first embodiment. Further, the second magnetic member 11 is added. The second magnetic member corrects the magnetic flux emitted from the first magnetic member 1 so that the MR element of the biaxial magnetic sensor unit 10 can easily receive the magnetic flux. That is, the second magnetic member has a function of guiding a magnetic field (magnetic field from the magnetic member 1), which was originally a Z-axis magnetic field component, in the magnetosensitive direction (X and Y plane directions) of the MR element. Thus, the Z-axis component is brought closer to the magnetosensitive direction, and the sensitivity is improved. As with the first magnetic member 1, it is desirable to use a material with high magnetic permeability for the second magnetic member 11. The second magnetic member 11 is provided on the opposite side of the magnetic member with the biaxial magnetic sensor portion interposed therebetween. In this case, by disposing the first magnetic member and the second magnetic member in the biaxial plane direction, the magnetic component in the third axis direction can be more easily directed in the biaxial plane direction. In the example of FIG. 8, the back side is not shown, but the portion of the second magnetic member 11 that faces the MR element assembly is hollowed out. The second magnetic member 11 may be formed by film formation using a technique such as photolithography or mask patterning in the wafer manufacturing process for forming the biaxial magnetic sensor portion, as described above. You may form by sticking the sheet | seat of a magnetic body. The shape of the second magnetic member 11 can be such that the magnetic field from the first magnetic member 1 can be efficiently guided to the MR element R when the hollowed out rectangular or circular one is used. In order not to disturb the distribution, a plurality of divided shapes are preferable. Further, it is desirable that the divided shape is radial. Further, the total area of the plane is preferably larger than the area of the magnetic collecting surface 1 a of the first magnetic member 1. When the magnetic sensor is sealed with plastic, the lead frame material itself used as a terminal, or a magnetic body bonded to the lead frame material or formed on the lead frame material may be used as the second magnetic member. it can. In this case, the sensitivity can be increased because a large area can be used effectively without being limited by the chip size of the wafer, which is directly related to the chip unit price.

  (Third Embodiment) A magnetic member 2 of a magnetic sensor according to a third embodiment of the present invention is formed so as to overlap along a meander-like magnetic body pattern constituting the MR element R. FIG. 9 shows a schematic cross-sectional view of the meander-shaped pattern cut in the short direction. The magnetic material to be the magnetic member 2 is narrower than the width of the pattern, and the cross-sectional shape is substantially rectangular or square. It is formed so as to be located at an end portion shifted from the center of each MR element portion constituting the meander pattern. In this configuration, the magnetic member 2 is preferably formed by film formation in the wafer manufacturing process for forming the biaxial magnetic sensor unit. In this case, since it is not necessary to attach a magnetic member in a separate process after forming the biaxial magnetic sensor portion, the manufacturing efficiency is high and the mass productivity is excellent. Also, the magnetic sensor having this structure can be reduced in height because the magnetic member 2 is dispersed and acts on each MR element, so that the overall height of the magnetic sensor is almost equal to the height of the two-axis magnetic field sensor section. It can be suppressed equally. For example, a low-profile three-axis magnetic sensor can be configured by using a magnetic member having a film thickness of 0.1 to 10 μm. In addition, since the direction of the lines of magnetic force can be accurately introduced into the pattern of each MR element, all MR elements cause a resistance change with respect to the Z-axis magnetic field, and high sensitivity can be obtained. It is also possible to increase the output by introducing a magnetic field to all MR elements and utilizing the change direction of the output signal depending on its direction. In FIG. 9, the magnetic member 2 is formed above the planar coil C formed on the MR element R, but may be formed between the MR element R and the planar coil C.

1 is a schematic external view of a magnetic sensor according to a first embodiment. It is a perspective view which shows arrangement | positioning of the magnetoresistive effect element and planar coil of the magnetic sensor of 1st Embodiment. It is a schematic diagram which shows the electrical structure of the magnetic sensor of 1st Embodiment. It is a top view which shows arrangement | positioning of the magnetoresistive effect element and magnetic member of the magnetic sensor of 1st Embodiment. It is an electric circuit diagram for amplification output of the magnetic sensor of the first embodiment. 3 is an example of a triaxial magnetic field detection output of the magnetic sensor according to the first embodiment. It is a longitudinal cross-sectional schematic diagram of the magnetic sensor of FIG. It is the external appearance schematic of the magnetic sensor which has arrange | positioned the 2nd magnetic member on the opposite side to the 1st magnetic member on both sides of the biaxial magnetic sensor part. It is the cross-sectional schematic of the magnetic sensor which formed the magnetic member along the pattern of the magnetoresistive effect element.

Explanation of symbols

1, 2: Magnetic member, 1a: Upper end surface of magnetic member, 1b: Lower end surface of magnetic member,
10: biaxial magnetic sensor unit, 11: second magnetic member, 12: protective insulating film,
13: Substrate, 14: Z-axis direction magnetic component, R: Magnetoresistive element, C: Planar coil

Claims (6)

  1.   A biaxial magnetic sensor unit having a magnetoresistive effect element formed so as to have sensitivity in a plane direction including two orthogonal axes, and a biaxial magnetic sensor unit provided so as to protrude from the plane including the orthogonal two axes A magnetic member that causes the magnetic component in the third axis direction orthogonal to the two orthogonal axes to be bent in a plane direction including the orthogonal two axes and detected by the two-axis magnetic sensor unit; and a resistance value of the magnetoresistive element. A magnetic sensor characterized by comprising signal processing means for detecting outputs in three axial directions.
  2.   The magnetic sensor according to claim 1, wherein a second magnetic member is further provided on a side opposite to the magnetic member across the biaxial magnetic sensor unit.
  3.   The magnetic sensor according to claim 1, wherein the magnetic member is a film body.
  4.   The biaxial magnetic sensor unit includes a planar coil having at least two pairs of parallel opposite sides and four pairs of magnetoresistive effect element pairs formed in a plane parallel to the coil surface. The longitudinal direction of each of the two magnetoresistive elements in each of the two sets intersects only the same one side of the opposite side pair of the planar coil, and the longitudinal direction of each of the other two magnetoresistive elements is the opposite side. One side of the pair that intersects only the opposite side of the one side and the longitudinal direction of each of the two other magnetoresistive effect elements in the other two sets is the same as the other side pair Magnetoresistive effect in which the longitudinal direction of each of the other two magnetoresistive elements intersects only the opposite side of the one side of the other opposite side pair and the same side of the planar coil. The longitudinal direction of the elements is not parallel The magnetic sensor according to claim 1, characterized in that.
  5.   5. The magnetic sensor according to claim 4, wherein one terminal of each magnetoresistive effect element pair is connected to each other, and an intermediate potential output taken out therefrom is inputted to the signal processing means.
  6.   6. The assembly comprising the four pairs of magnetoresistive effect element pairs, the planar coil, and the magnetic member have a four-fold symmetry with respect to the center of the biaxial magnetic sensor unit. The magnetic sensor described.
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