JP2020197394A - Magnetic sensor - Google Patents

Abstract

To provide a magnetic sensor in which a manufacturing cost is reduced and detection accuracy is improved.SOLUTION: A magnetic sensor 1 outputs a signal according to a distance to a magnetic body. The magnetic sensor 1 includes magnetic field generation means for applying a magnetic field in a direction opposite to each other to a predetermined space so that a magnetic field strength of the predetermined space is smaller than a magnetic field strength of a region around the predetermined space, and an electric circuit in which at least a pair of giant magnetoresistance effect elements, the electric resistance value of which decreases as the intensity of the applied magnetic field increases, are arranged in a predetermined plane in the predetermined space at a predetermined first distance in a predetermined first direction and are bridge-connected.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic sensor that outputs a signal according to a distance from a magnetic material.

For example, as shown in Patent Document 1 below, for example, a magnetic sensor MS that detects the movement of convex portions and concave portions (more specifically, the rotation speed, rotation angle, etc. of a gear) is known (more specifically, See FIG. 24). This magnetic sensor MS includes a sensor chip SC, a chip package CP, and a bias magnet BM.

The sensor chip SC includes four GMR elements (giant magnetoresistive elements) Ra to Rd of the magnetic field strength detection type. These GMR elements Ra to Rd are fully bridge-connected. The GMR elements Ra to Rd are each composed of a linear granular thin film or a linear artificial lattice film formed on the insulating substrate SC1. The configurations of the GMR elements Ra to Rd are the same. The GMR elements Ra and Rb and the GMR elements Rc and Rd are connected to each other to form a half-bridge circuit. Then, these two half-bridge circuits are connected to form a full-bridge circuit. The GMR elements Ra and Rd and the GMR elements Rb and Rc are arranged symmetrically on the surface of the insulating substrate SC1 with the center line CL11 extending in the vertical direction shown in the drawing as the axis of symmetry. The linear granular thin film or the linear artificial lattice film constituting the GMR elements Ra to Rd is arranged so that the longitudinal direction is parallel to the extending direction of the center line CL11.

The insulating substrate SC1 is provided with a plurality of electrodes Pa to Pd electrically connected to the GMR elements Ra to Rd connected by a full bridge. The GMR elements Ra to Rd and the insulating substrate SC1 are housed (sealed) in a chip package CP molded from resin, and a plurality of conductive lead frame portions electrically connected to a plurality of electrodes Pa to Pd. Fa to Fd protrude from the chip package CP.

The bias magnet BM has a rectangular parallelepiped shape and is formed in a long shape, and its first surface is magnetized to the N pole and the second surface opposite to the first surface is magnetized to the S pole. In this bias magnet BM, the first surface (or the second surface) is opposed to the GMR elements Ra to Rd, and between the two long sides on the first surface (or the second surface) facing the GMR elements Ra to Rd. The center line CL13 is tilted by a predetermined angle (for example, 45 degrees) with respect to the center line CL12 connecting the centers of the GMR elements Ra and Rd and the GMR elements Rb and Rc. The midpoint O11 between the GMR elements Ra and Rd and the GMR elements Rb and Rc on the center line CL12 is the center of the first surface (or second surface) of the bias magnet BM which is a point on the center line CL13. Arranged so as to face the points. As a result, in the plane of the GMR elements Ra to GMR elements Rd, bias magnetic fields of equal strength in opposite directions, which are inclined by a predetermined angle with respect to the center lines CL11 and CL12, are the GMR elements Ra and Rd and the GMR element. It is applied to Rb and Rc, respectively.

The magnetic sensor configured in this way has a center line CL12 on the outer peripheral surface of a gear formed of a magnetic material having convex portions (teeth) and concave portions extending in a direction orthogonal to the moving direction. It is arranged so as to be orthogonal to the rotation direction of the gear (movement direction of the teeth). Then, when the gear is rotated, a bias magnetic field that changes in a sinusoidal shape in the direction opposite to the center line CL11 is applied to the GMR elements Ra and Rd and the GMR elements Rb and Rc, respectively, and the GMR elements Ra and Rd And the magnetoresistive values of the GMR elements Rb and Rc change in a sinusoidal direction in opposite directions according to the movement of the magnetic material. As a result, a sinusoidal differential signal corresponding to the rotation of the gear can be obtained from the bridge circuit composed of the GMR elements Ra to Rd.

Japanese Patent No. 6425519

In the conventional magnetic sensor MS, when the midpoint O11 does not face the center point of the first surface (or the second surface) of the bias magnet BM (when both are deviated), the GMR element Ra ~ In the plane of Rd, the strength of the bias magnetic field applied to the GMR elements Ra and Rd is different from the strength of the bias magnetic field applied to the GMR elements Rb and Rc. Therefore, the waveform of the output signal of the bridge circuit when the gear rotates is not sinusoidal and is slightly distorted. In order to increase the detection accuracy of the rotation of the gear, it is necessary to keep the arrangement accuracy of the bias magnet BM with respect to the GMR elements Ra to Rd high, and the manufacturing cost of the magnetic sensor MS is high.

Further, in general, the electric resistance values of the GMR elements Ra to the GMR elements Rd are the largest when the strength of the applied magnetic field is “0” (see FIG. 12). Then, as the strength of the magnetic field increases, the electric resistance value gradually decreases. As shown in the figure, the rate of change of the electric resistance value is substantially constant within a predetermined range of the strength of the magnetic field. That is, the change in the electric resistance value with respect to the change in the strength of the magnetic field is linear. When the strength of the magnetic field exceeds the predetermined value, the rate of change of the electric resistance value gradually decreases, and the electric resistance value hardly changes (saturates) even if the magnetic field strength is changed.

As described above, in the magnetic sensor MS of Patent Document 1, a bias magnetic field is applied to the GMR elements Ra to Rd. That is, the electrical resistance values of the GMR elements Ra to Rd are set to the intermediate value (value between the maximum value and the minimum value) of the change range. Then, as the gear rotates, the strength of the bias magnetic field changes, the electric resistance values of the GMR elements Ra to Rd change in a substantially sinusoidal shape, and a sinusoidal electric signal (voltage) is output from the full bridge circuit. To.

Here, if the change in the intensity of the bias magnetic field applied to the GMR elements Ra to Rd is increased, the amplitude of the output signal is increased. For example, if the gap between the GMR elements Ra to Rd and the magnetic material is set to be relatively small, the amplitude of the output signal becomes large. However, when the intensity of the bias magnetic field applied to the GMR elements Ra to Rd changes, the output signal is not sinusoidal in the region (saturation region) where the electrical resistance value does not change so much, and the waveform is distorted. Therefore, in this case, the rotation detection accuracy of the gear is lowered.

The present invention has been made to address such a problem, and an object of the present invention is to provide a magnetic sensor having improved detection accuracy while reducing manufacturing cost. In the following description of each component of the present invention, in order to facilitate understanding of the present invention, the reference numerals of the corresponding parts of the embodiments are described in parentheses, but each component of the present invention is described. It should not be construed as limited to the configuration of the corresponding parts indicated by the reference numerals of the embodiments.

In order to achieve the above-mentioned object, the magnetic sensors (1, 2) according to the present invention oppose each other so that the magnetic field strength in the predetermined space is smaller than the magnetic field strength in the surrounding region. A magnetic field forming means (13) for applying a magnetic field in a direction and at least a pair of giant magnetic resistance effect elements (122a to 122d, 222a to 222d), the electric resistance thereof as the strength of the applied magnetic field increases. A giant magnetic resistance effect element whose value decreases is arranged in a predetermined plane in the predetermined space in a predetermined first direction at a predetermined distance by a predetermined first distance, and is bridge-connected with an electric circuit. A signal corresponding to the distance from the magnetic material (G) is output.

In one aspect of the present invention, the magnetic field forming means is a tubular permanent magnet extending in a second direction orthogonal to the predetermined first direction, and one end surface in the axial direction thereof is magnetized to the north pole, and the other It is a permanent magnet whose end face is magnetized to the S pole, and the electric circuit is housed inside the magnetic field forming means formed in a tubular shape.

In one aspect of the present invention, the magnetic field forming means is a pair of plate-shaped permanent magnets parallel to the second direction orthogonal to the first direction, and is orthogonal to the first direction and the second direction. It is composed of a pair of permanent magnets separated in three directions, one end surface of the pair of permanent magnets in the second direction is magnetized to the N pole, and the other end surface is magnetized to the S pole.

In one aspect of the present invention, the pair of giant magnetoresistive elements is composed of a granular thin film having a linear portion extending in the second direction.

In one aspect of the present invention, it is applied to the detection of the operation of a magnetic material having at least one convex portion or concave portion moving in the first direction.

In a state where the magnetic sensor according to the present invention is not arranged near the magnetic material, the magnetic field strength applied to the giant magnetoresistive element is relatively small, and the electric resistance value of the giant magnetoresistive element is relatively large. .. Therefore, even if the magnetic material is brought close to the magnetic sensor and the gap (distance) is relatively small, the electric resistance value of the giant magnetoresistive element is unlikely to be saturated. Therefore, when the magnetic sensor according to the present invention is used, the output signal waveform is not easily distorted, and the magnetic material can be detected with high accuracy.

Further, when the magnetic material is arranged in the vicinity of the magnetic sensor, the strength of the magnetic field applied to the magnetic sensor in the direction of the magnetic material becomes larger. As a result, the smaller the distance (gap) between the magnetic sensor and the magnetic material, the larger the output of the magnetic sensor can be obtained.

Further, when a permanent magnet is used as the magnetic field forming means, the direction of the magnetic field differs greatly depending on the position in the region where the magnetic force is weakened by the magnetic field heading in the opposite direction, but the intensities tend to be substantially the same. is there. Therefore, for a giant magnetoresistive element having a characteristic that the electric resistance value decreases as the strength of the applied magnetic field increases, even if the arrangement accuracy of the magnetic field forming means is slightly low, the electric resistance value of the electric resistance value Since fluctuation (deviation) can be suppressed, the detection accuracy of the magnetic material by the magnetic sensor can be kept high. Therefore, the manufacturing cost of the magnetic sensor can be reduced.

In one aspect of the present invention, two sets of the electric circuits are provided, respectively, arranged in the predetermined plane, and the two sets of electric circuits are arranged so as to be displaced in the first direction by a predetermined second distance. ing.

According to this, when the uneven portion made of the magnetic material is moved in the direction parallel to the first direction, two (two-phase) output signal waveforms out of phase can be obtained. By the arithmetic processing based on these two signal waveforms, the position of the uneven portion can be detected with high accuracy.

Further, in one aspect of the present invention, the position and orientation of the electric circuit with respect to the magnetic field forming means are determined based on the electric resistance value of the electric circuit.

The electric resistance value of the electric circuit changes according to the strength of the magnetic force applied to the giant magnetoresistive element constituting the electric circuit. Therefore, when the electric circuit is moved in the vicinity of the magnetic field forming means, the electric resistance value of the electric circuit changes. Based on the change in the electric resistance value, the region where the magnetic force in the magnetic field forming means is weakened can be easily detected. According to this, the position and orientation of the electric circuit with respect to the magnetic field forming means can be easily determined.

It is a perspective view which shows the state which the magnetic sensor which concerns on 1st Embodiment of this invention is arranged near a gear as a detection target. FIG. 1 is a perspective view showing a state in which the bias magnet of the magnetic sensor is omitted. FIG. 2 is a perspective view showing a state in which the resin sealing portion of the magnetic sensor is omitted in FIG. It is a front view (view from the right side) which shows the inside of the magnetic sensor of FIG. It is an enlarged view of the sensor chip in FIG. It is an electric circuit diagram which shows the electrical connection relation of the GMR element of the magnetic sensor of FIG. It is a top view of the magnetic sensor. It is the schematic which shows the outline of the magnetic field (magnetic vector) in the lower surface of a bias magnet. It is a graph which shows the intensity ratio of the magnetic field component of the central part in the left-right direction of the lower surface of the bias magnet when the gear is rotated below the bias magnet. It is a layout drawing which shows the position of the GMR element of the magnetic sensor of FIG. 1 with respect to a bias magnet. It is a layout drawing which shows the position of the GMR element of the magnetic sensor of FIG. 1 with respect to a gear. It is a graph which shows the change of the electric resistance value of a GMR element with respect to the magnetic field applied to a GMR element. It is a graph which shows the output signal waveform of the magnetic sensor of FIG. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the misalignment in the left-right direction of the GMR element of the magnetic sensor of FIG. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the positional deviation of the GMR element of the magnetic sensor of FIG. 1 in the front-rear direction. It is a front view (the view seen from the right side) which shows the inside of the magnetic sensor which concerns on 2nd Embodiment of this invention. It is an electric circuit diagram which shows the electrical connection relation of the GMR element of the magnetic sensor of FIG. It is a layout drawing which shows the position of the GMR element of the magnetic sensor of FIG. 16 with respect to a gear. It is a graph which shows the output signal waveform of the magnetic sensor of FIG. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the misalignment in the left-right direction of the GMR element of the magnetic sensor of FIG. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the displacement in the front-rear direction of the GMR element of the magnetic sensor of FIG. It is a perspective view of the magnetic sensor which concerns on the modification of this invention. It is a perspective view of the magnetic sensor which concerns on other modification of this invention. It is a top view which shows the inside of the conventional magnetic sensor. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the displacement in the longitudinal direction of the GMR element of the magnetic sensor of FIG. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the displacement of the GMR element of the magnetic sensor in the lateral direction of FIG. 24. It is a graph which shows the output signal waveform of the magnetic sensor of FIG. It is a top view which shows the inside of another conventional magnetic sensor. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the displacement in the longitudinal direction of the GMR element of the magnetic sensor of FIG. 28. It is a graph which shows the offset of the output signal of a magnetic sensor with respect to the displacement of the GMR element of the magnetic sensor in FIG. 28 in the lateral direction.

(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the magnetic sensor 1 according to the first embodiment of the present invention includes a chip package 11, a sensor chip 12, and a bias magnet 13.

The chip package 11 includes a resin sealing portion formed of an epoxy resin in a substantially rectangular plate shape. In the following description, the extending direction of the long side of the chip package 11 is referred to as the front-rear direction, and the extending direction of the short side of the chip package 11 is referred to as the vertical direction. Further, the plate thickness direction of the chip package 11 is referred to as a left-right direction.

As shown in FIGS. 3 and 4, the chip package 11 includes an island portion 111 and lead frame portions 112a to 112d. These parts are thin plate parts that are substantially perpendicular to the left-right direction. These sites are made of a non-magnetic conductor material (eg, a copper plate).

The island portion 111 has a rectangular shape extending in the front-rear direction, and is arranged in the lower half portion of the chip package 11. The long side and the short side of the island portion 111 are parallel to the long side and the short side of the chip package 11, respectively.

The lead frame portions 112a to 112d have a hook shape, their lower edge portions are positioned slightly above the upper edge portion of the island portion 111, and their upper end portions are projected upward from the upper surface of the chip package 11. There is. In addition, in FIGS. 1 to 3, the shapes of the lead frame portions 112a to 112d are simplified.

The sensor chip 12 is fixed to the surface (right surface) of the island portion 111. The sensor chip 12 includes an insulating substrate 121 made of an insulating material such as silicon, glass, or ceramic and formed in a substantially rectangular plate shape. The length L1 of the short side of the insulating substrate 121 is set to 1.05 mm, and the length L2 of the long side is set to 1.8 mm (see FIG. 5). Further, the thickness of the insulating substrate 121 is set to 0.25 mm. The long side and the short side of the insulating substrate 121 are parallel to the long side and the short side of the chip package 11, respectively, and are fixed to the upper surface of the island portion 111 by a die bond material.

GMR elements (giant magnetoresistive elements) 122a to 122d and electrodes 123a to 123d are arranged on the surface of the insulating substrate 121. The GMR elements 122a to 122d are composed of a linear granular thin film made of Ag-FeCo, and are formed on the insulating substrate 121 by forming a granular thin film on the surface of the insulating substrate 121 by a sputtering method. ing. The GMR elements 122a and 122d are formed on the rectangular region 121a provided on the rear side portion of the surface of the insulating substrate 121, and the GMR elements 122b and 122c are formed on the rectangular region 121b provided on the front side portion on the surface of the insulating substrate 121. ing. The shapes and sizes of the rectangular regions 121a and 121b are the same, and the length in the vertical direction is set to be larger than the length in the front-rear direction. The positions of the rectangular regions 121a and 121b in the vertical direction are the same. That is, the distances from the lower sides of the rectangular regions 121a and 121b to the lower sides of the insulating substrate 121 and the chip package 11 are the same, and the rectangular regions 121a and 121b are related to the center line CL1 extending in the vertical direction through the center in the front-rear direction of the insulating substrate 121. It is arranged in a symmetrical position. The length L3 of the long side of these rectangular regions 121a and 121b is set to 0.48 mm, and the length L4 of the short side is set to 0.3 mm. Further, the distance L5 of the opposite long sides of the rectangular region 121a and the rectangular region 121b is set to 0.92 mm. The distance L6 between the center of the rectangular region 121a and the center of the rectangular region 121b is 1.25 mm.

The GMR elements 122a and 122d are formed on the rectangular region 121a. The GMR elements 122a and 122d exhibit a rectangle extending in the vertical direction as a whole. The GMR elements 122a and 122d are each formed in a linear shape having a plurality of folded portions. More specifically, the GMR elements 122a and 122d extend in a straight line in the vertical direction by a fixed length (a length slightly shorter than the length L3) in the rectangular region 121a, and are folded forward from the upper end or the lower end thereof. It is configured so that the portions that are curved in the vertical direction and are configured to extend linearly in the vertical direction by the fixed length are continuous.

Further, the GMR elements 122a and 122d have a portion in which the distance between the adjacent linear portions in the front-rear direction is increased and a portion in which the distance between the adjacent linear portions is reduced in the front-rear direction. Then, the portion of the GMR element 122a in which the distance between the adjacent linear portions in the front-rear direction is increased is inserted into the portion of the GMR element 122d in which the distance between the adjacent linear portions is reduced in the front-rear direction, and the portion adjacent to the GMR element 122d is adjacent. A portion of the GMR element 122a in which the distance between the adjacent linear portions in the front-rear direction is reduced is inserted into the portion where the distance between the adjacent linear portions is increased in the front-rear direction. The number of turns of these GMR elements 122a and 122d is set so that, for example, the number of straight portions extending in the vertical direction of the GMR elements 122a and 122d is 17.

The GMR elements 122b and 122c are configured in the same manner as the GMR elements 122a and 122d on the rectangular region 121b. The GMR element 122b is arranged so as to be symmetrical with respect to the GMR element 122a with the center line CL1 as the axis of symmetry. Further, the GMR element 122c is arranged so as to be symmetrical with respect to the GMR element 122d with the center line CL1 as the axis of symmetry.

The electrodes 123a to 123d are thin plate-shaped non-magnetic conductor materials (for example, aluminum), and are formed in a square pattern on the insulating substrate 121. The electrode 123a is located above the GMR elements 122b and 122c, and the electrode 123b is located above the GMR elements 122a and 122d. The electrodes 123a and 123b are arranged symmetrically with respect to the center line CL1. The electrode 123c is located behind the GMR elements 122b and 122c and between the center line CL1 and the GMR elements 122b and 122c, and the electrode 123d is in front of the GMR elements 122a and 122d and is located in front of the center lines CL1 and the GMR element 122a. , 122d. The electrodes 123c and 123d are arranged symmetrically with respect to the center line CL1.

Further, as shown in FIG. 5, a wiring pattern 124 for electrically connecting the GMR elements 122a to 122d and the electrodes 123a to 123d is formed on the insulating substrate 121. The wiring pattern 124 is also made of a thin plate-shaped non-magnetic conductor material (for example, aluminum). One end of the GMR element 122a is electrically connected to the electrode 123a by the wiring pattern 124, and the other end of the GMR element 122a is connected to the electrode 123c by the wiring pattern 124. One end of the GMR element 122b is electrically connected to the electrode 123b by the wiring pattern 124, and the other end of the GMR element 122b is connected to the electrode 123c by the wiring pattern 124. As a result, the GMR elements 122a and 122b are half-bridged (see FIG. 6). Further, one end of the GMR element 122c is electrically connected to the electrode 123a by the wiring pattern 124, and the other end of the GMR element 122c is connected to the electrode 123d by the wiring pattern 124. One end of the GMR element 122d is electrically connected to the electrode 123b by the wiring pattern 124, and the other end of the GMR element 122d is connected to the electrode 123d by the wiring pattern 124. As a result, the GMR elements 122c and 122d are also half-bridged.

The electrodes 123a to 123d are electrically connected to the lead frame portions 112a to 112d, respectively, via wires 113a to 113d made of conductive wires (for example, gold wires) (see FIG. 4). The lead frame portion 112a is connected to a power supply terminal of an electric circuit device provided externally. The lead frame portion 112b is connected to the ground terminal of the electric circuit device (see FIG. 6). As a result, a constant voltage V is applied between the lead frame portion 112a and the lead frame portion 112b. The lead frame unit 112c outputs the voltage Vo1 at the connection point between the GMR element 122a and the GMR element 122b to the electric circuit device. The lead frame unit 112d outputs the voltage Vo2 at the connection point between the GMR element 122c and the GMR element 122d to the electric circuit device. As described above, the GMR elements 122a to 122d form a full bridge circuit. Further, the electric circuit device includes a differential amplifier 125, and the differential amplifier 125 outputs a voltage and a difference voltage of Vo1 and Vo2 as an output signal.

The bias magnet 13 is a neodymium magnet whose main raw materials are neodymium and iron. The bias magnet 13 has a tubular shape extending in the vertical direction (see FIG. 1). That is, the bias magnet 13 has a through hole TH ₁₃ that penetrates in the vertical direction. In the plan view of the bias magnet 13, the bias magnet 13 exhibits a substantially rectangular shape extending in the front-rear direction (see FIG. 7). In the figure, the length L7 of the long side and the length L8 of the short side of the outer shape of the bias magnet 13 are set to 7.5 mm and 2.7 mm, respectively. The length L10 of the shorter side of the long side length L9 and the through-hole _{TH 13} of the through-hole _{TH 13} is set to 6.0mm and 1.5mm respectively.

Further, the height L11 (see FIG. 1) of the bias magnet 13 is set to 3.0 mm. Further, the bias magnet 13 is polarized with a surface that divides the height direction into two equal parts as a boundary, and is magnetized to two poles in the direction perpendicular to the boundary surface, and the lower side is magnetized to the N pole. , The upper side is magnetized to the S pole.

A part of the magnetic field lines from the north pole to the south pole of the bias magnet 13 configured as described above passes through the through hole TH ₁₃ . Of these lines of magnetic force, the lines of magnetic force that go in opposite directions cancel each other out. As a result, a region Z in which the magnetic force is weakened as compared with the periphery thereof is formed slightly below the through hole TH ₁₃ of the bias magnet 13 (see FIG. 8). The region Z extends in the anteroposterior direction slightly below the through hole TH ₁₃ . The central axis of the region Z is located at the central portion (or slightly below it) in the width direction (left-right direction) of the through hole TH ₁₃ . It should be noted that the two points having the same distance from the central axis of the region Z and the two points slightly separated from each other around the central axis of the region Z have the same magnitude, but the directions of the magnetic vectors are large. different.

Note that FIG. 8 shows a magnetic field (magnetic vector) when there is no magnetic material around the bias magnet 13. When a magnetic material is present around the bias magnet 13, the magnetic field is in a state different from that in FIG. For example, as shown in the simulation result shown in FIG. 9, when the gear rotates below the region Z, the magnetic field in the region Z changes periodically. In this simulation, it is assumed that the S45C steel involute gear as a magnetic material is rotated below the bias magnet. The gear tooth pitch in this case is set to 2.5 mm. Further, as the bias magnet, it is assumed that two square plate-shaped magnets are simply arranged facing each other instead of the tubular magnet. The configuration of each of the two plate-shaped magnets is the same. The plate thickness directions of both magnets coincide with the left-right direction. The gap between the two magnets is set to 1.5 mm. Of the sides of both magnets, the length of the side extending in the vertical direction is set to 5.0 mm, and the length of the side extending in the front-rear direction is set to 6.0 mm. Further, the thickness of both magnets is set to 0.6 mm. Then, it is assumed that the rotation axes of the gears are arranged below both magnets so as to coincide with each other in the left-right direction. Under such conditions, when the gear is rotated, the vertical component of the magnetic vector at the central position between the lower surfaces of both magnets mainly changes. FIG. 9 shows a change in the intensity (magnetic field intensity) of the component. In the figure, the changes in the magnetic field strength when the distance (gap) between the top surface of the gear teeth and the bottom surfaces of both permanent magnets is set to any value within the range of 0.5 mm to 1.5 mm are shown. ing. In the figure, the magnetic field strength when the gap is set to 0.5 mm is used as a reference, and the magnetic field strengths in other gaps are relative values to the above reference.

As shown in the figure, the change in magnetic field strength with the movement of teeth (rotation of gears) is substantially sinusoidal. Further, as the gap between the tooth and the magnet becomes smaller, the magnetic field strength becomes larger as a whole and its amplitude becomes larger. Even when the bias magnet 13 is used, the same characteristics as those in FIG. 9 are exhibited.

The main body M1 composed of the chip package 11 and the sensor chip 12 configured as described above is housed in the through hole TH ₁₃ of the bias magnet 13 (see FIG. 1). The center line CL2 (see FIG. 5) passing through the centers of the GMR elements 122a and 122d and the centers of the GMR elements 122b and 122c and the central axis of the region Z are coaxially arranged (see FIGS. 7 and 10). In reality, the main body M1 is moved in a state where no magnetic material exists around the bias magnet 13, and the electric resistance value of the electric circuit configured by connecting the GMR elements 122a to 122d is maximized. The position and orientation of the main body M1 with respect to the bias magnet 13 are adjusted so as to be. Then, the intersection O1 between the center line CL2 and the center line CL1 (that is, the central position between the centers of the GMR elements 122a and 122d and the GMR elements 122b and 122c) is located below the central position in the front-rear direction of the through hole TH _13. ing. In addition, in FIG. 7 and FIG. 10, the resin sealing portion of the chip package CP is omitted.

Next, an example (actual measurement value) of detecting the rotation of the gear G, which is a magnetic material, using the magnetic sensor 1 will be described. First, the configuration of the gear G will be described. The gear G has rectangular convex portions (teeth) G1 and concave portions G2 having the same shape and size alternately arranged on a circular outer peripheral surface. The spacing (pitch) of the convex portions G1 of the gear G coincides with twice the length L6. If the gear G is made of a magnetic material, it can be made of various magnetic materials into various shapes. Further, as for the shape of the gear G, if it has the convex portion G1 and the concave portion G2, it can be configured into various shapes. The gear G of the present embodiment is an S45C steel involute-shaped gear. Both the gear G according to the present invention used in various experiments and the conventional gear G described in the section of background technology are S45C steel involute-shaped gears.

The magnetic sensor 1 is fixed in the vicinity of the gear G by using a fixing component (not shown). The lower end surface of the main body M1 faces parallel to the top surface of the convex portion G1 of the gear G, and the front-rear direction of the main body M1 (sensor chip 12) coincides with the rotation direction of the gear G (movement direction of the convex portion G1). The magnetic sensor 1 and the gear G are arranged so as to (see FIGS. 10 and 11). The distance (gap) from the lower end of the chip package 11 to the top surface of the one convex portion G1 is set to, for example, any value within the range of 0.1 mm to 1.0 mm.

When the gear G is rotated with the magnetic sensor 1 arranged with respect to the gear G as described above, the magnetic field passing in parallel (vertical direction) with respect to the element surfaces of the GMR elements 122a and 122d and the GMR element 122b , The magnetic field strength of the magnetic field passing parallel to the element surface of 122c (vertical direction) changes in a substantially sinusoidal shape with a phase difference of 180 °.

Specifically, the magnetic field strength _Had that passes parallel (downward) to the element surface of the GMR elements 122a and 122d is the first when the GMR elements 122a and 122d are at an intermediate position between two adjacent convex portions G1. It is strength. At this time, the GMR elements 122b and 122c face one convex portion G1. The magnetic field strength H _bc passing parallel (downward) to the element surface of the GMR elements 122b and 122c has a second strength higher than the first strength.

As the gear G rotates, the magnetic field strength _Had gradually increases from the first strength, and the magnetic field strength H _bc gradually decreases from the second strength. In a state where the GMR elements 122a and 122d face one convex portion G1, the magnetic field strength _Had becomes the second strength. At this time, the GMR elements 122b and 122c are located at intermediate positions between the two adjacent convex portions G1, and the magnetic field strength H _bc has the first strength.

When the gear G further rotates, the magnetic field strength _Had gradually decreases from the second strength, and the magnetic field strength H _bc gradually increases from the first strength. When the GMR elements 122a and 122d are in the intermediate position between the two adjacent convex portions G1, the magnetic field strength _Had returns to the first strength. At this time, the GMR elements 122b and 122c face one convex portion G1, and the magnetic field strength H _bc returns to the second strength. The changes in the magnetic field intensities _Had and _Hbc are substantially sinusoidal.

Here, with respect to the change in the magnetic field strength applied to the GMR elements 122a to 122d, the electrical resistance values of the GMR elements 122a to 122d change as shown in FIG. Thus, the magnetic field intensity _H ad as described _above, a change in _{H bc,} the electric resistance value of the GMR element 122a~122d varies approximately sinusoidally. The phase of the change in the electrical resistance value of the GMR elements 122b and 122c differs by 180 ° (1/2 pitch of the convex portion G1 of the gear G) with respect to the change in the electrical resistance value of the GMR elements 122a and 122d. ..

The differential voltage of the voltage Vo1 and Vo2 of the full bridge circuit formed by hand forming the GMR elements 122a to 122d by full bridge connection is output from the differential amplifier 125 as an output signal. That is, it is possible to obtain a rotation detection signal of the gear G having a relatively large amplitude value (see FIG. 13).

Here, a case where the longitudinal direction of the GMR elements 122a to 122d is the application direction of the magnetic field and a case where the short direction of the GMR elements 122a to 122d is the application direction of the magnetic field will be described. The solid line in FIG. 12 shows the change characteristic of the electric resistance value of the GMR element with respect to the applied magnetic field strength when the longitudinal direction of the GMR element is the application direction of the magnetic field. The broken line in FIG. 12 shows the change characteristic of the electric resistance value of the GMR element with respect to the applied magnetic field strength when the lateral direction of the GMR element is the application direction of the magnetic field. That is, with respect to the magnetic field sensitivity anisotropy, when the longitudinal direction is the magnetic field application direction, the magnetic field strength is "0" than when the short direction is the magnetic field application direction. The change in the electric resistance value of the GMR element is linear and large, and a large output voltage with little distortion can be obtained. Therefore, it is preferable to set the longitudinal direction of the GMR elements 122a to 122d as the magnetic field application direction as in the above embodiment, rather than to set the lateral direction of the GMR elements 122a to 122d as the magnetic field application direction. That is, as in the above embodiment, the magnetic sensor 1 can be arranged with respect to the gear G so that the longitudinal direction of the GMR elements 122a to 122d is parallel to the radial direction (toothing direction) of the gear G. preferable. As a result, as shown in FIG. 13, in the rotation detection of the gear G of the above embodiment, a sinusoidal output voltage having a large amplitude and high accuracy can be obtained.

Further, FIG. 25 shows a change in the offset of the output voltage when the bias magnet BM is shifted in the lateral direction of the element in the magnetic sensor MS of Patent Document 1. Further, FIG. 26 shows a change in the offset of the output voltage when the bias magnet BM is shifted in the longitudinal direction of the element in the magnetic sensor MS. Further, in the magnetic sensor 1 of the present embodiment, FIG. 14 shows a change in the offset of the output voltage when the bias magnet 13 is shifted in the left-right direction with respect to the main body portion M1. Further, FIG. 15 shows a change in the offset of the output voltage when the bias magnet 13 is displaced in the front-rear direction with respect to the main body portion M1 of the magnetic sensor 1.

As shown in FIGS. 25 and 26, in the magnetic sensor MS, if the position of the bias magnet BM with respect to the GMR elements Ra to Rd is slightly deviated, the offset of the output voltage changes significantly. Therefore, in order to keep the rotation detection accuracy of the gear G by the magnetic sensor MS high, it is necessary to keep the placement accuracy of the bias magnet BM high. On the other hand, as shown in FIGS. 14 and 15, even if the position of the bias magnet 13 with respect to the GMR elements 122a to 122d is slightly deviated in the magnetic sensor 1, the offset of the output voltage does not change so much. Therefore, even if the placement accuracy of the bias magnet 13 is slightly low, the rotation detection accuracy of the gear G by the magnetic sensor 1 can be kept high.

Further, FIG. 27 shows an example in which the rotation of the gear G is detected by using the magnetic sensor MS of Patent Document 1. As shown in the figure, in this case, if the gap is made small (for example, when it is 0.1 mm), the output signal waveform is distorted. This factor is due to the fact that in the magnetic sensor MS, the magnetic field strength of the bias magnets BM applied to the GMR elements Ra to Rd is relatively large when the magnetic sensor MS is not arranged in the vicinity of the gear G (magnetic material). Because it is in. That is, when the magnetic sensor MS is arranged in the vicinity of the gear G and the gap is small, the magnetic field strength applied to the GMR elements Ra to Rd is large, and the electric resistance value does not change linearly with the change. This is because (the sensitivity decreases).

On the other hand, in the present embodiment, the magnetic field strength of the bias magnets 13 applied to the GMR elements 122a to 122d is relatively small (in the state where the magnetic sensor 1 is not arranged in the vicinity of the gear G (magnetic material)). It is abbreviated as "0"). Therefore, even when the magnetic sensor 1 is arranged in the vicinity of the gear G and the gap is small, the electric resistance value changes linearly with respect to the change in the magnetic field strength applied to the GMR elements 122a to 122d (). The electrical resistance value is hard to saturate). Therefore, when the magnetic sensor 1 according to the present embodiment is used, as shown by the solid line in FIG. 13, the output signal waveform is not distorted and exhibits a sinusoidal shape even in the same gap (0.1 mm).

As described above, according to the magnetic sensor 1, the rotation of the gear G can be detected with high accuracy. Further, even if the placement accuracy of the bias magnet 13 with respect to the main body M1 is slightly low, the rotation detection accuracy of the gear G is unlikely to decrease. Therefore, the manufacturing cost of the magnetic sensor 1 can be reduced.

(Second Embodiment)
Hereinafter, the second embodiment of the present invention will be described with reference to the drawings. The configuration of the magnetic sensor 2 according to the second embodiment of the present invention is substantially the same as that of the first embodiment. The appearance of the magnetic sensor 2 is the same as that of the magnetic sensor 1 (see FIG. 1). However, the sensor chip 22 is used instead of the sensor chip 12 (see FIG. 16).

The configuration of the chip package 11 is the same as that of the first embodiment. Also in the second embodiment, the extending direction of the long side of the chip package 11 is referred to as the front-rear direction, and the extending direction of the short side of the chip package 11 is referred to as the vertical direction. Further, the plate thickness direction of the chip package 11 is referred to as a left-right direction.

The sensor chip 22 is fixed to the surface (left surface) of the island portion 111. The sensor chip 22 includes an insulating substrate 221 similar to the insulating substrate 121 of the first embodiment. GMR elements (giant magnetoresistive elements) 222a to 222d and electrodes 223a to 223d are arranged on the surface (right surface) of the insulating substrate 221.

The GMR elements 222a to 222d are arranged at equal intervals in the front-rear direction along the upper edge of the insulating substrate 221. The distance between the central portions of the two GMR elements adjacent to each other in the front-rear direction is 1/4 (= 0.625 mm) of the pitch of the teeth of the gear G. The configuration of the GMR elements 222a to 222d is substantially the same as the configuration of the GMR elements 122a to 122d. As described above, the GMR elements 122a to 122d have a portion in which the distance between the adjacent linear portions in the front-rear direction is increased and a portion in which the distance between the adjacent linear portions is reduced in the front-rear direction. On the other hand, in the GMR elements 222a to 222d, the distance between the adjacent linear portions in the front-rear direction is constant.

The configurations of the electrodes 223a to 223d are also the same as the configurations of the electrodes 123a to 123d. Further, as in the first embodiment, the GMR elements 222a to 222d and the electrodes 223a to 223d are electrically connected by the wiring pattern 224, respectively. As a result, the GMR elements 222a and 222c are half-bridged, and the GMR elements 222b and 222d are half-bridged (see FIG. 17).

The electrodes 223a to 223d are electrically connected to the lead frame portions 112a to 112d, respectively, via wires 113a to 113d made of conductive wires (for example, gold wires). The lead frame portion 112a is connected to a power supply terminal of an electric circuit device provided externally. The lead frame portion 112c is connected to the ground terminal of the electric circuit device. As a result, a constant voltage V is applied between the lead frame portion 112a and the lead frame portion 112c. The lead frame unit 112b outputs the voltage VoA at the connection point between the GMR element 222a and the GMR element 222c to the electric circuit device. The lead frame unit 112d outputs the voltage VoB at the connection point between the GMR element 222b and the GMR element 222d to the electric circuit device, respectively.

The main body M2 composed of the chip package 11 and the sensor chip 22 configured as described above is housed in the through hole TH ₁₃ of the bias magnet 13 as in the first embodiment. The gear G is rotated below it (see FIG. 18). In the present embodiment, the distance between the GMR element 222a and the GMR element 222c in the front-rear direction is set to 1/2 of the pitch of the convex portion G1 of the gear G. Therefore, when the gear G rotates, the voltage VoA changes in a sinusoidal shape as in the first embodiment. On the other hand, the distance between the GMR element 222b and the GMR element 222d in the front-rear direction is also set to 1/2 of the pitch of the convex portion G1 of the gear G. Therefore, when the gear G rotates, the voltage VoB changes in a sinusoidal shape as in the first embodiment. However, in the present embodiment, the distance between the GMR element 222a and the GMR element 222b in the front-rear direction is set to 1/4 of the pitch of the convex portion G1 of the gear G, and the distance between the GMR element 222c and the GMR element 222d in the front-rear direction is set. The interval is set to 1/4 of the pitch of the convex portion G1 of the gear G. Therefore, the phase difference between the waveforms of voltage VoA and voltage VoA is 90 ° (see FIG. 19).

According to this, the rotation of the gear G can be detected with high accuracy as in the first embodiment. Further, a highly accurate sinusoidal output signal A (voltage VoA) and cosine wave-shaped output B (voltage VoB) representing the rotation of the gear G can be obtained, and the inverse tangent (arc) using the output signals A and B can be obtained. The rotation angle of the gear G can be easily calculated by the tangent) calculation.

In addition, Patent Document 1 describes a magnetic sensor MS including two sets of sensor chips SCA and SCB (see FIG. 28). In this example, the two sets of sensor chips SCA and SCB are arranged so as to be offset in the rotation direction of the gear G and the tooth width direction of the gear G. In this case, the strength of the bias magnetic field applied to the GMR elements Ra and Rd of the sensor chips SCA and SCB is substantially the same as the strength of the bias magnetic field applied to the GMR elements Rb and Rc of the sensor chips SCA and SCB, respectively. The bias magnet BM is arranged so that the directions thereof are substantially opposite to each other. Even with the magnetic sensor MS configured in this way, sinusoidal output signals with a phase shift of 90 ° can be obtained from the sensor chips SCA and SCB, and the rotation angle of the gear G is calculated using these output signals. it can.

Here, in the magnetic sensor MS of FIG. 28, the change in the offset of the output voltage of each of the sensor chips SCA and SCB when the bias magnet BM is shifted in the longitudinal direction is shown in FIG. 29. Further, FIG. 30 shows a change in the offset of the output voltage when the bias magnet BM is shifted in the lateral direction in the magnetic sensor MS. Further, in the magnetic sensor 2 of the second embodiment of the present invention, FIG. 20 shows a change in the offset of the output voltage when the bias magnet 13 is shifted in the left-right direction with respect to the main body MB. Further, FIG. 21 shows a change in the offset of the output voltage when the bias magnet 13 is shifted in the front-rear direction with respect to the main body MB in the magnetic sensor 1.

As shown in FIGS. 29 and 30, when the positions of the bias magnets BM with respect to the GMR elements Ra to Rd of both sensor chips SCA and SCB are displaced in the magnetic sensor MS, the output voltages of the sensor chips SCA and SCB change significantly. .. Moreover, the mode (direction) of the change in the output voltage of the sensor chips SCA and SCB is opposite. Therefore, it is difficult to maintain high placement accuracy of the bias magnet BM. On the other hand, as shown in FIGS. 20 and 21, the output voltage does not change so much even if the position of the bias magnet 13 with respect to the GMR elements 222a to 222d is slightly deviated in the magnetic sensor 2. Therefore, even if the placement accuracy of the bias magnet 13 is slightly low, the rotation detection accuracy of the gear G by the magnetic sensor 2 can be kept high. Therefore, the manufacturing cost of the magnetic sensor 2 can be reduced.

Furthermore, the practice of the present invention is not limited to the above-described embodiment, and various changes can be made as long as the object of the present invention is not deviated.

For example, as shown in FIG. 22, the two main bodies M1 are opposed to each other and are arranged so as to be displaced in the front-rear direction by a distance corresponding to 1/4 of the pitch of the convex portion G1 of the gear G, and a set of these main bodies The portions M1 and M1 may be housed in the through hole TH ₁₃ of the bias magnet 13. This also has substantially the same effect as that of the second embodiment.

Further, in the above embodiment, the tubular magnet is used as the bias magnet 13, but instead, as shown in FIG. 23, a bias magnet composed of two flat plate-shaped permanent magnets 13A and 13A is used. You may adopt it.

In the above embodiment, various lengths and distances L1 to L11 are set to predetermined values, but these values can be changed as appropriate. Further, in the above embodiment, the lower side (the side facing the gear G) of the bias magnet 13 is the N pole and the opposite side is magnetized to the S pole, but the N pole and the S pole may be reversed. Further, in the above embodiment, the island portion 111 is formed of a non-magnetic conductive plate similar to the lead frame portions 112a to 112d. However, since the island portion does not require conductivity, a thin plate made of a non-conductive material may be used as long as it is a non-magnetic material.

Further, in the first embodiment, the full bridge circuit is configured by the four GMR elements 122a to 122d, a sinusoidal output signal is obtained from the full bridge circuit, and the rotation of the gear G is detected. However, although the output amplitude value becomes smaller, a half-bridge circuit is formed by two GMR elements 122a and 122b (or GMR elements 122c and 122d), and a sinusoidal output signal is obtained from the half-bridge circuit to obtain a sinusoidal output signal of the gear G. The rotation may be detected.

Further, in the above embodiment, a GMR element using a granular thin film is used as the magnetic field strength detection type GMR element which is an in-plane magnetic sensing element. However, instead of this, an artificial lattice type GMR element can be used as the magnetic field strength detection type GMR element which is an in-plane magnetoreceptive element. This artificial lattice type GMR element is described, for example, in Vol. 15. A laminate in which magnetic layers and non-magnetic layers having a thickness of several angstroms to several tens of angstroms are alternately laminated, which is described in the paper entitled "Magnetic Resistance Effect of Artificial Lattice" in Nos. 51991 and P813-121. It is composed of a so-called artificial lattice film ((Fe / Cr) n, (Permalloy / Cu / Co / Cu) n, (Co / Cu) n, etc.).

Further, in the above embodiment, as the GMR element, the GMR elements 122a to 122d or the GMR elements 222a to 222d in which the granular thin film is folded back and extended linearly are used. However, a spiral GMR element may be used instead of these GMR elements 122a to 122d or the GMR elements 222a to 222d. These spiral GMR elements are formed by extending a linear granular thin film (or artificial lattice film) spirally from the outside to the inside on an insulating substrate and spirally linearly linearly extending from the inner end to the outer side. It is an extension of a thin film (or artificial lattice film).

Further, in the above embodiment, the magnetic sensor 1 and the magnetic sensor 2 are applied to a detection device that detects the rotation of the gear G made of a magnetic material. However, the magnetic sensor 1 described above can be applied not only to the gear G but also to the rotation detection of a disk-shaped member having one or more recesses on the outer peripheral surface of the disk-shaped member. Further, the above-mentioned magnetic sensor 1 and magnetic sensor 2 are also applied to the detection of a moving body which is made of a magnetic material and has convex portions (teeth) or concave portions and moves linearly even if it is not a rotating body. obtain. Also in this case, the magnetic sensor 1 and the magnetic sensor 2 described above may be arranged so as to face the uneven portion of the moving body.

1 ... Magnetic sensor, 2 ... Magnetic sensor, 11 ... Chip package, 12 ... Sensor chip, 13 ... Bias magnet, 13A ... Bias magnet, 22 ... Sensor chip, 121 ... Insulated substrate, 122a ... GMR element, 122b ... GMR element, 122c ... GMR element, 122d ... GMR element, 124 ... Wiring pattern, 125 ... Differential amplifier, 221 ... Insulated substrate, 222a ... GMR element, 222b ... GMR element, 222c ... GMR element, 222d ... GMR element, 224 ... Wiring pattern , G ... Gear, G1 ... Convex, G2 ... Concave, Had ... Magnetic field strength, Hbc ... Magnetic field strength, Z ... Region

Claims (7)

A magnetic sensor that outputs a signal according to the distance to the magnetic material.
A magnetic field forming means for applying magnetic fields in opposite directions to the predetermined space so that the magnetic field strength in the predetermined space is smaller than the magnetic field strength in the surrounding region.
At least a pair of giant magnetoresistive elements whose electrical resistance value decreases as the strength of the applied magnetic field increases, are predetermined in a predetermined plane in the predetermined space. An electric circuit that is arranged and bridge-connected by a predetermined first distance in the first direction of the
With a magnetic sensor. In the magnetic sensor according to claim 1,
It comprises two sets of the electric circuits, each arranged in the predetermined plane.
A magnetic sensor in which the two sets of electric circuits are arranged so as to be displaced in the first direction by a predetermined second distance. In the magnetic sensor according to claim 1 or 2.
The magnetic field forming means is a tubular permanent magnet extending in a second direction orthogonal to the predetermined first direction, and one end surface in the axial direction thereof is magnetized to the N pole and the other end surface is magnetized to the S pole. Is a permanent magnet
A magnetic sensor in which the electric circuit is housed inside the magnetic field forming means formed in a tubular shape. In the magnetic sensor according to claim 1 or 2.
The magnetic field forming means is a pair of plate-shaped permanent magnets parallel to the second direction orthogonal to the first direction, and a pair of plate-shaped permanent magnets separated from each other in the first direction and the third direction orthogonal to the second direction. Consists of permanent magnets
A magnetic sensor in which one end surface of the pair of permanent magnets in the second direction is magnetized to the N pole and the other end surface is magnetized to the S pole. In the magnetic sensor according to claim 3 or 4.
The pair of giant magnetoresistive elements is a magnetic sensor composed of a granular thin film having a linear portion extending in the second direction. In the magnetic sensor according to any one of claims 1 to 5.
A magnetic sensor in which the position and orientation of the electric circuit with respect to the magnetic field forming means are determined based on the electric resistance value of the electric circuit. The magnetic sensor according to any one of claims 1 to 6.
A magnetic sensor applied to detect the movement of a magnetic material having at least one convex or concave portion moving in the first direction.

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