JP7341454B2 - magnetic sensor - Google Patents

Description

The present invention relates to a magnetic sensor that outputs a signal depending on the distance to a magnetic body.

For example, as shown in Patent Document 1 below, a magnetic sensor MS that detects the movement of convex portions and concave portions (more specifically, the rotation speed, rotation angle, etc. of gears) is known ( (See Figure 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 magnetic field strength sensing type GMR elements (giant magnetoresistive elements) Ra to Rd. These GMR elements Ra to Rd are connected in a full bridge manner. The GMR elements Ra to Rd are each composed of a linear granular thin film or a linear artificial lattice film formed on an insulating substrate SC1. The configurations of GMR elements Ra to Rd are the same. GMR elements Ra, Rb and GMR elements Rc, Rd are connected to each other to form a half bridge circuit. These two half-bridge circuits are connected to form a full-bridge circuit. The GMR elements Ra, Rd and the GMR elements Rb, Rc are arranged at symmetrical positions within the surface of the insulating substrate SC1 with a center line CL11 extending in the vertical direction in the figure as an axis of symmetry. The GMR elements Ra to Rd are arranged so that the longitudinal direction of the linear granular thin film or the linear artificial lattice film 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 in a full bridge manner. The GMR elements Ra to Rd and the insulating substrate SC1 are housed (sealed) in a chip package CP molded with resin, and include a plurality of conductive lead frame parts electrically connected to the plurality of electrodes Pa to Pd. Fa to Fd protrude from the chip package CP.

The bias magnet BM has an elongated rectangular parallelepiped shape, and its first surface is magnetized to the north pole, and the second surface opposite to the first surface is magnetized to the south pole. This bias magnet BM has a first surface (or second surface) facing the GMR elements Ra to Rd, and a gap between two long sides on the first surface (or second surface) facing the GMR elements Ra to Rd. Center line CL13 is inclined by a predetermined angle (for example, 45 degrees) with respect to center line CL12 connecting the centers of GMR elements Ra, Rd and GMR elements Rb, Rc. The middle point O11 between the GMR elements Ra, Rd and the GMR elements Rb, Rc, which is 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. placed opposite the point. As a result, in the plane of GMR elements Ra to GMR elements Rd, bias magnetic fields of equal strength and opposite directions are applied to the GMR elements Ra, Rd and the GMR elements in a direction inclined by a predetermined angle with respect to the center lines CL11 and CL12. It is applied to Rb and Rc, respectively.

The magnetic sensor configured in this manner has a center line CL12 on the outer circumferential surface of a gear made of a magnetic material and having convex portions (teeth) and concave portions extending in a direction perpendicular to the direction of movement. It is arranged perpendicular to the direction of rotation of the gear (direction of tooth movement). Then, when the gears are rotated, a bias magnetic field that changes sinusoidally in opposite directions in the direction of the center line CL11 is applied to the GMR elements Ra, Rd and GMR elements Rb, Rc, and the GMR elements Ra, Rd The electrical resistance values of the GMR elements Rb and Rc change sinusoidally in opposite directions in accordance with the movement of the magnetic body. As a result, a sinusoidal differential signal corresponding to the rotation of the gear can be obtained from the bridge circuit made up of the GMR elements Ra to Rd.

Patent No. 6425519

In the above-described conventional magnetic sensor MS, if the midpoint O11 does not face the center point of the first surface (or second surface) of the bias magnet BM (if both are shifted), the GMR elements Ra to In the plane of Rd, the intensity of the bias magnetic field applied to the GMR elements Ra and Rd is different from the intensity of the bias magnetic field applied to the GMR elements Rb and Rc. Therefore, when the gear rotates, the waveform of the output signal from the bridge circuit is not sinusoidal, but slightly distorted. In order to increase the accuracy of detecting the rotation of the gear, it is necessary to maintain high accuracy in the arrangement of the bias magnets BM with respect to the GMR elements Ra to Rd, which increases the manufacturing cost of the magnetic sensor MS.

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

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 an intermediate value (a value between the maximum value and the minimum value) of the variation range. As the gear rotates, the strength of the bias magnetic field changes, and the electrical resistance values of the GMR elements Ra to Rd change in a substantially sinusoidal manner, and a sinusoidal electrical signal (voltage) is output from the full bridge circuit. Ru.

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 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, in a region where the electrical resistance value does not change much (saturation region), the output signal is not sinusoidal and its waveform is distorted. Therefore, in this case, the accuracy of detecting the rotation of the gear decreases.

The present invention has been made to address such problems, and its purpose is to provide a magnetic sensor with reduced manufacturing costs and improved detection accuracy. In addition, in the following description of each component of the present invention, in order to facilitate understanding of the present invention, the reference numerals of corresponding parts in the embodiment are written in parentheses, but each component of the present invention is as follows: It should not be interpreted as being limited to the configuration of corresponding parts indicated by the reference numerals in the embodiments.

In order to achieve the above object, the magnetic sensors (1, 2) according to the present invention include a pair of flat permanent magnets that are parallel to a predetermined first direction and parallel to a second direction orthogonal to the first direction. and are spaced apart in a third direction perpendicular to the first direction and perpendicular to the second direction, one end in the second direction is magnetized to the north pole, and the other end in the second direction is magnetized to the south pole. A magnetic field strength in a predetermined space that includes a pair of permanent magnets that are magnetized as poles and that is spaced apart from the one end or the other end and extends in the first direction is smaller than the magnetic field strength in the surrounding area. a magnetic field forming means (13) for applying magnetic fields in opposite directions to the predetermined space; and at least a pair of giant magnetoresistive elements (122a to 122d, 222a to 222d), A giant magnetoresistive element whose electrical resistance value decreases as the strength of the magnetic field increases is positioned in a predetermined first direction within a predetermined plane perpendicular to the third direction within the predetermined space. and an electrical circuit arranged at a distance from the magnetic body (G) and connected in a bridge manner, and outputs a signal according to the distance to the magnetic body (G).

In one aspect of the present invention, the magnetic field forming means is a rectangular cylindrical permanent magnet extending in the second direction, one end surface of which in the axial direction is magnetized to a north pole, and the other end surface is magnetized to a south pole. It is a magnetized permanent magnet, and the electric circuit is housed inside the cylindrical magnetic field forming means.

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

In one aspect of the present invention, the present invention is applied to detecting the operation of a magnetic body having at least one convex portion or concave portion that moves in the first direction.

In a state where the magnetic sensor according to the present invention described above is not placed near a magnetic body, the magnetic field strength applied to the giant magnetoresistive element is relatively small, and the electrical resistance value of the giant magnetoresistive element is relatively large. . Therefore, even if a magnetic body is brought close to the magnetic sensor and the gap (distance) therebetween becomes relatively small, the electrical resistance value of the giant magnetoresistive element is difficult to saturate. Therefore, when the magnetic sensor according to the present invention is used, the output signal waveform is less likely to be distorted, and a magnetic substance can be detected with high precision.

Further, when a magnetic body is placed near the magnetic sensor, the intensity of the magnetic field applied to the magnetic sensor and directed toward the magnetic body becomes larger. As a result, the smaller the distance (gap) between the magnetic sensor and the magnetic body, the greater the output of the magnetic sensor can be obtained.

Furthermore, when a permanent magnet is used as a magnetic field forming means, in a region where the magnetic force is weakened by a magnetic field directed in the opposite direction, the direction of the magnetic field varies greatly depending on the position, but the strength tends to be approximately the same. be. Therefore, for a giant magnetoresistive element that has the characteristic that its electrical resistance value decreases as the intensity of the applied magnetic field increases, even if the arrangement precision of the magnetic field forming means is somewhat low, the electrical resistance value will decrease. Since the fluctuation (shift) can be suppressed, the detection accuracy of the magnetic body by the magnetic sensor can be kept high. Therefore, the manufacturing cost of the magnetic sensor can be reduced.

One aspect of the present invention includes two sets of the electric circuits respectively arranged within the predetermined plane, and the two sets of electric circuits are arranged so as to be shifted by a predetermined second distance in the first direction. ing.

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

Further, in one aspect of the present invention, the electric circuit is arranged with respect to the magnetic field forming means so that the electric resistance value of the electric circuit is maximized .

The electrical resistance value of the electrical circuit changes depending on the strength of the magnetic force applied to the giant magnetoresistive element constituting the electrical circuit. Therefore, when the electric circuit is moved near the magnetic field forming means, the electric resistance value of the electric circuit changes. Based on the change in the electrical resistance value, a 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.

FIG. 1 is a perspective view showing a state in which a magnetic sensor according to a first embodiment of the present invention is arranged near a gear as a detection target. FIG. 2 is a perspective view showing a state in which the bias magnet of the magnetic sensor in FIG. 1 is omitted. FIG. 3 is a perspective view showing a state in which the resin sealing portion of the magnetic sensor in FIG. 2 is omitted. FIG. 2 is a front view (view from the right side) showing the inside of the magnetic sensor in FIG. 1. FIG. 5 is an enlarged view of the sensor chip in FIG. 4. FIG. 5 is an electric circuit diagram showing the electrical connection relationship of the GMR element of the magnetic sensor of FIG. 4. FIG. FIG. 2 is a plan view of a magnetic sensor. FIG. 2 is a schematic diagram showing an outline of a magnetic field (magnetic vector) on the lower surface of a bias magnet. It is a graph showing the strength ratio of magnetic field components at the center in the left-right direction of the lower surface of the bias magnet when a gear is rotated below the bias magnet. FIG. 2 is a layout diagram showing the position of a GMR element of the magnetic sensor of FIG. 1 with respect to a bias magnet. FIG. 2 is a layout diagram showing the position of the GMR element of the magnetic sensor of FIG. 1 with respect to a gear. 3 is a graph showing a change in electrical resistance value of a GMR element with respect to a magnetic field applied to the GMR element. 2 is a graph showing an output signal waveform of the magnetic sensor in FIG. 1. FIG. 2 is a graph showing the offset of the output signal of the magnetic sensor with respect to the horizontal positional deviation of the GMR element of the magnetic sensor of FIG. 1. FIG. 2 is a graph showing the offset of the output signal of the magnetic sensor with respect to the longitudinal positional shift of the GMR element of the magnetic sensor of FIG. 1. FIG. It is a front view (view from the right side) showing the inside of a magnetic sensor concerning a 2nd embodiment of the present invention. 17 is an electric circuit diagram showing the electrical connection relationship of the GMR element of the magnetic sensor of FIG. 16. FIG. FIG. 17 is a layout diagram showing the position of the GMR element of the magnetic sensor of FIG. 16 with respect to the gear. 17 is a graph showing an output signal waveform of the magnetic sensor of FIG. 16. FIG. 17 is a graph showing the offset of the output signal of the magnetic sensor with respect to the horizontal positional deviation of the GMR element of the magnetic sensor of FIG. 16. FIG. 17 is a graph showing the offset of the output signal of the magnetic sensor with respect to the longitudinal positional deviation of the GMR element of the magnetic sensor of FIG. 16. FIG. It is a perspective view of the magnetic sensor concerning the modification of the present invention. FIG. 6 is a perspective view of a magnetic sensor according to another modification of the present invention. FIG. 2 is a plan view showing the inside of a conventional magnetic sensor. 25 is a graph showing the offset of the output signal of the magnetic sensor with respect to the longitudinal positional deviation of the GMR element of the magnetic sensor of FIG. 24. FIG. 25 is a graph showing the offset of the output signal of the magnetic sensor with respect to the positional shift in the lateral direction of the GMR element of the magnetic sensor of FIG. 24. FIG. 25 is a graph showing an output signal waveform of the magnetic sensor in FIG. 24. FIG. FIG. 3 is a plan view showing the inside of another conventional magnetic sensor. 29 is a graph showing the offset of the output signal of the magnetic sensor with respect to the longitudinal positional deviation of the GMR element of the magnetic sensor of FIG. 28. FIG. 29 is a graph showing the offset of the output signal of the magnetic sensor with respect to the positional shift in the lateral direction of the GMR element of the magnetic sensor of FIG. 28. FIG.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described using the drawings. 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, as shown in FIGS. 1 to 3.

The chip package 11 includes a resin sealing portion made of epoxy resin and formed into a substantially rectangular plate shape. In the following description, the direction in which the long sides of the chip package 11 extend will be referred to as the front-back direction, and the direction in which the short sides of the chip package 11 will extend will be referred to as the up-down direction. Further, the thickness direction of the chip package 11 is referred to as the 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 portions are thin plate portions that are substantially perpendicular to the left-right direction. These parts are formed of a non-magnetic conductive material (for example, a copper plate).

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

The lead frame parts 112a to 112d have a hook-shaped shape, have their lower edges located slightly above the upper edge of the island part 111, and have their upper ends protrude upward from the upper surface of the chip package 11. There is. Note that 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 having 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. This insulating substrate 121 is fixed to the upper surface of the island section 111 with a die bonding material, with its long sides and short sides parallel to the long sides and short sides of the chip package 11, respectively.

On the surface of the insulating substrate 121, GMR elements (giant magnetoresistive elements) 122a to 122d and electrodes 123a to 123d are arranged. The GMR elements 122a to 122d are composed of linear granular thin films made of Ag-FeCo, and are formed on the insulating substrate 121 by depositing a granular thin film on the surface of the insulating substrate 121 using a sputtering method. ing. The GMR elements 122a and 122d are formed in a rectangular area 121a provided on the rear side of the surface of the insulating substrate 121, and the GMR elements 122b and 122c are formed on a rectangular area 121b provided on the front side of the surface of the insulating substrate 121. ing. The shape and size of the rectangular regions 121a and 121b are the same, and the length in the up-down direction is set to be larger than the length in the front-back direction. The vertical positions of the rectangular areas 121a and 121b 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 located at a distance from the lower sides of the insulating substrate 121 and the chip package 11 with respect to the center line CL1 that passes through the center of the insulating substrate 121 in the front-rear direction and extends in the vertical direction. They are placed in symmetrical positions front and back. The length L3 of the long side of these rectangular areas 121a, 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 between the opposing long sides of the rectangular area 121a and the rectangular area 121b is set to 0.92 mm. The distance L6 between the center of the rectangular area 121a and the center of the rectangular area 121b is 1.25 mm.

GMR elements 122a and 122d are formed on rectangular region 121a. The GMR elements 122a and 122d as a whole have a rectangular shape extending in the vertical direction. The GMR elements 122a and 122d are each formed in a linear shape with a plurality of folded portions. More specifically, the GMR elements 122a and 122d extend vertically in a straight line for a fixed length (a length slightly shorter than length L3) in the rectangular region 121a, and are folded back forward from the upper or lower end thereof. The portion is configured such that the portion is curved and then extends linearly in the vertical direction by the predetermined length.

Furthermore, the GMR elements 122a and 122d have portions in which the distance between adjacent linear portions is increased in the front-rear direction, and portions in which the distance in the front-rear direction between adjacent linear portions is decreased. Then, a portion of the GMR element 122d where the distance between adjacent linear portions of the GMR element 122d is made smaller in the front and back direction is inserted into a portion of the GMR element 122a where the distance between adjacent linear portions of the GMR element 122d is increased. A portion of the GMR element 122a where the distance between adjacent linear portions in the front-rear direction is reduced is inserted into a portion where the distance between the matching linear portions is increased in the front-back direction. The number of times these GMR elements 122a and 122d are folded back is set such that, for example, the number of vertically extending straight portions of the GMR elements 122a and 122d is 17.

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

The electrodes 123a to 123d are made of a thin plate-like nonmagnetic conductive material (for example, aluminum) and are formed into a square pattern on the insulating substrate 121. Electrode 123a is located above GMR elements 122b and 122c, and electrode 123b is located above GMR elements 122a and 122d. The electrodes 123a and 123b are arranged symmetrically in the front and rear with respect to the center line CL1. The electrode 123c is located behind the GMR elements 122b, 122c and between the center line CL1 and the GMR elements 122b, 122c, and the electrode 123d is located in front of the GMR elements 122a, 122d, between the center line 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, wiring patterns 124 are formed on the insulating substrate 121 to electrically connect the GMR elements 122a to 122d and the electrodes 123a to 123d, respectively. This wiring pattern 124 is also made of a thin plate-like non-magnetic conductive 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. Thereby, the GMR elements 122a and 122b are half-bridge connected (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. Thereby, the GMR elements 122c and 122d are also half-bridge connected.

The electrodes 123a to 123d are electrically connected to the lead frame parts 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 external electric circuit device. 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 section 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 section 112d outputs the voltage Vo2 at the connection point between the GMR element 122c and the GMR element 122d to the electric circuit device. In this way, the GMR elements 122a to 122d constitute a full bridge circuit. Further, the electric circuit device includes a differential amplifier 125, and the differential amplifier 125 outputs a voltage difference between Vo1 and Vo2 as an output signal.

The bias magnet 13 is a neodymium magnet whose main materials are neodymium and iron. The bias magnet 13 has a cylindrical 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 a plan view of the bias magnet 13, the bias magnet 13 has 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. Further, the length L9 of the long side of the through hole TH ₁₃ and the length L10 of the short side of the through hole TH ₁₃ are set to 6.0 mm and 1.5 mm, respectively.

Further, the height L11 (see FIG. 1) of the bias magnet 13 is set to 3.0 mm. In addition, the bias magnet 13 is polarized with a plane dividing the height direction into two equal parts as a boundary, and is magnetized into two poles in a direction perpendicular to the boundary plane, with the lower side being magnetized as a north pole and , the upper side is magnetized to the south pole.

A portion of the magnetic lines of force directed from the N pole to the S pole of the bias magnet 13 configured as described above passes through the through hole TH ₁₃ . Among these lines of magnetic force, lines of magnetic force that go in opposite directions cancel each other out. As a result, a region Z is formed slightly below the through hole TH ₁₃ of the bias magnet 13, where the magnetic force is weaker than the surrounding area (see FIG. 8). The region Z extends in the front-rear direction slightly below the through hole _TH13 . The central axis of the region Z is located at the center (or slightly below the center) of the through hole TH ₁₃ in the width direction (horizontal direction). Note that the magnitude of the magnetic vectors at two points that are the same distance from the central axis of area Z and slightly separated around the central axis of area Z are the same, but the direction of the magnetic vector is large. different.

Note that FIG. 8 shows the magnetic field (magnetic vector) when no magnetic material exists around the bias magnet 13. If a magnetic body exists around the bias magnet 13, the magnetic field will be in a different state from that shown in FIG. For example, as shown in the simulation results 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 an S45C steel involute gear serving as a magnetic material is rotated below a bias magnet. The pitch of the gear teeth in this case is set to 2.5 mm. Furthermore, instead of using a cylindrical magnet as the bias magnet, it is assumed that two rectangular plate-shaped magnets are arranged facing each other. The configurations of these two plate-shaped magnets are the same. The plate thickness directions of both magnets are aligned in the left-right direction. The gap between both magnets is set to 1.5 mm. Among 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-back direction is set to 6.0 mm. Further, the thickness of both magnets is set to 0.6 mm. It is assumed that the gears are arranged below both magnets so that their rotational axes are aligned in the left-right direction. Under such conditions, when the gear is rotated, the vertical component of the magnetic vector at the center position between the lower surfaces of both magnets changes mainly. FIG. 9 shows changes in the strength of the components (magnetic field strength). The figure shows the change in magnetic field strength when the distance (gap) between the top surface of the gear tooth and the bottom surface of both permanent magnets is set to any value within the range of 0.5 mm to 1.5 mm. 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 with respect to the above-mentioned reference.

As shown in the figure, the change in magnetic field strength due to the movement of the teeth (rotation of the gear) has a substantially sinusoidal shape. Furthermore, as the gap between the teeth and the magnet becomes smaller, the overall magnetic field strength increases and its amplitude increases. Note that even when the bias magnet 13 is used, characteristics similar to those shown in FIG. 9 are exhibited.

The main body M1 consisting 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). A 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 is coaxially arranged with the center axis of the region Z (see FIGS. 7 and 10). Note that in reality, the main body M1 is moved in a state where no magnetic material exists around the bias magnet 13, and the electrical resistance value of the electrical circuit configured by connecting each GMR element 122a to 122d is maximized. The position and attitude of the main body portion M1 with respect to the bias magnet 13 are adjusted so that The intersection O1 between the center line CL2 and the center line CL1 (that is, the center position between the centers of the GMR elements 122a, 122d and the GMR elements 122b, 122c) is located below the center position of the through hole _TH13 in the front-rear direction. ing. Note that in FIGS. 7 and 10, the resin sealing portion of the chip package CP is omitted.

Next, an example (actually measured value) in which the rotation of the gear G, which is a magnetic material, is detected using the magnetic sensor 1 will be described. First, the configuration of gear G will be explained. The gear G has rectangular convex portions (teeth) G1 and concave portions G2 of the same shape and size alternately arranged on a circular outer peripheral surface. The interval (pitch) between the convex portions G1 of the gear G is equal to twice the length L6. As long as the gear G is made of a magnetic material, it can be made of various magnetic materials and have various shapes. Further, regarding the shape of the gear G, it can be configured in various shapes as long as it has a convex portion G1 and a concave portion G2. The gear G of this embodiment is an involute gear made of S45C steel. Note that both the gear G related to the present invention used in various experiments and the conventional gear G explained in the background art section are S45C steel involute gears.

The magnetic sensor 1 is fixed near the gear G using a fixed part (not shown). The lower end surface of the main body M1 faces parallel to the top surface of the convex part G1 of the gear G, and the front-rear direction of the main body M1 (sensor chip 12) coincides with the rotating direction of the gear G (the moving direction of the convex part G1). The magnetic sensor 1 and the gear G are arranged so as to do so (see FIGS. 10 and 11). The distance (gap) from the bottom end of the chip package 11 to the top surface of the one convex portion G1 is set, for example, to 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 as described above with respect to the gear G, a magnetic field passing in parallel (in the vertical direction) to the element surfaces of the GMR elements 122a and 122d and a GMR element 122b are generated. , 122c, the magnetic field intensities of the magnetic fields passing in parallel (in the vertical direction) to the element surfaces change approximately sinusoidally with a phase difference of 180°.

Specifically, when the GMR elements 122a, 122d are at the intermediate position between two adjacent convex portions G1, the magnetic field strength H _ad passing parallel to (downward) the element surfaces of the GMR elements 122a, 122d is the first 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 to (downward) the element surfaces of the GMR elements 122b and 122c is a second strength greater than the first strength.

As the gear G rotates, the magnetic field strength H _ad gradually increases from the first strength, and the magnetic field strength H _bc gradually decreases from the second strength. When the GMR elements 122a and 122d face one convex portion G1, the magnetic field strength H _ad 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 is the first strength.

As the gear G rotates further, the magnetic field strength H _ad 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 at intermediate positions between the two adjacent convex portions G1, the magnetic field strength H _ad 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. Note that the changes in the magnetic field strengths H _ad and H _bc have a substantially sinusoidal shape.

Here, in response to a 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. 12. Therefore, the electric resistance values of the GMR elements 122a to 122d change in a substantially sinusoidal manner due to changes in the magnetic field intensities H _ad and H _bc as described above. The phase of the change in the electrical resistance value of the GMR elements 122b, 122c is different from the change in the electrical resistance value of the GMR elements 122a, 122d by 180° (1/2 pitch of the convex portion G1 of the gear G). .

A differential voltage between voltages Vo1 and Vo2 of a hand-formed full-bridge circuit in which the GMR elements 122a to 122d are connected in a full-bridge manner is outputted from the differential amplifier 125 as an output signal. That is, a rotation detection signal of gear G having a relatively large amplitude value can be obtained (see FIG. 13).

Here, a case will be described in which the longitudinal direction of the GMR elements 122a to 122d is the direction in which the magnetic field is applied, and the case in which the lateral direction of the GMR elements 122a to 122d is the direction in which the magnetic field is applied. The solid line in FIG. 12 shows the change characteristic of the electrical resistance value of the GMR element with respect to the applied magnetic field strength when the longitudinal direction of the GMR element is the applied direction of the magnetic field. The broken line in FIG. 12 shows the change characteristic of the electrical resistance value of the GMR element with respect to the applied magnetic field strength when the lateral direction of the GMR element is the applied direction of the magnetic field. In other words, regarding the magnetic field sensitivity anisotropy, when the longitudinal direction is the direction of application of the magnetic field, it is better to set the magnetic field strength from the state of "0" when the longitudinal direction is the direction of application of the magnetic field than when the direction of application of the magnetic field is the lateral direction. The change in the electrical resistance value of the GMR element becomes linear and large, and a large output voltage with little distortion can be obtained. Therefore, as in the above embodiment, it is preferable that the longitudinal direction of the GMR elements 122a to 122d be the direction in which the magnetic field is applied, rather than the lateral direction of the GMR elements 122a to 122d to be the direction in which the magnetic field is applied. 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 (tooth depth direction) of the gear G. preferable. As a result, as shown in FIG. 13, in detecting the rotation of gear G in the embodiment described above, a sinusoidal output voltage with 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, in the magnetic sensor MS, 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. Further, in the magnetic sensor 1 of this 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 M1. Further, in the magnetic sensor 1, FIG. 15 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 M1.

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 shifted, the offset of the output voltage changes significantly. Therefore, in order to maintain high precision in detecting the rotation of gear G by magnetic sensor MS, it is necessary to maintain high precision in the arrangement of bias magnet BM. On the other hand, as shown in FIGS. 14 and 15, in the magnetic sensor 1, even if the position of the bias magnet 13 relative to the GMR elements 122a to 122d is slightly shifted, the offset of the output voltage does not change much. Therefore, even if the placement accuracy of the bias magnet 13 is somewhat low, the rotation detection accuracy of the gear G by the magnetic sensor 1 can be maintained high.

FIG. 27 shows an example in which the rotation of the gear G is detected using the magnetic sensor MS of Patent Document 1. As shown in the figure, in this case, if the gap is made smaller (eg, 0.1 mm), the output signal waveform will be distorted. This factor is caused by the fact that in the magnetic sensor MS, the magnetic field strength of the bias magnet BM applied to the GMR elements Ra to Rd is relatively large when the magnetic sensor MS is not placed near the gear G (magnetic body). This is because it is in That is, when the magnetic sensor MS is placed near the gear G and the gap is small, the magnetic field strength applied to the GMR elements Ra to Rd is large, and the electrical resistance value does not change linearly with respect to the change. This is because (sensitivity decreases).

In contrast, in this embodiment, when the magnetic sensor 1 is not placed near the gear G (magnetic material), the magnetic field strength of the bias magnet 13 applied to the GMR elements 122a to 122d is relatively small ( (abbreviated as “0”). Therefore, even if the magnetic sensor 1 is placed near the gear G and the gap therebetween is small, the electrical resistance value changes linearly with changes in the magnetic field strength applied to the GMR elements 122a to 122d ( electrical resistance value is difficult to saturate). Therefore, when the magnetic sensor 1 according to the present embodiment is used, the output signal waveform exhibits a sinusoidal waveform without distortion even at the same gap (0.1 mm), as shown by the solid line in FIG. 13.

Thus, according to the magnetic sensor 1, the rotation of the gear G can be detected with high accuracy. Furthermore, even if the placement accuracy of the bias magnet 13 with respect to the main body portion M1 is somewhat low, the detection accuracy of the rotation of the gear G is unlikely to deteriorate. Therefore, the manufacturing cost of the magnetic sensor 1 can be reduced.

(Second embodiment)
A second embodiment of the present invention will be described below 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 external appearance of the magnetic sensor 2 is the same as the magnetic sensor 1 (see FIG. 1). However, a 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 in the first embodiment. Also in the second embodiment, the direction in which the long sides of the chip package 11 extend is referred to as the front-rear direction, and the direction in which the short sides of the chip package 11 extend is referred to as the up-down direction. Further, the thickness direction of the chip package 11 is referred to as the left-right direction.

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

The GMR elements 222a to 222d are arranged along the upper edge of the insulating substrate 221 at equal intervals in the front-back direction. The interval between the centers of two GMR elements adjacent in the front-rear direction is 1/4 (=0.625 mm) of the tooth pitch of gear G. The configurations of GMR elements 222a to 222d are substantially the same as those of GMR elements 122a to 122d. As described above, the GMR elements 122a to 122d have portions in which the distance between adjacent linear portions is increased in the front-rear direction, and portions in which the distance in the front-rear direction between adjacent linear portions is decreased. In contrast, in the GMR elements 222a to 222d, the distance between 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. Thereby, the GMR elements 222a and 222c are connected in a half bridge, and the GMR elements 222b and 222d are connected in a half bridge (see FIG. 17).

The electrodes 223a to 223d are electrically connected to the lead frame parts 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 external electric circuit device. 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 section 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 section 112d outputs the voltage VoB at the connection point between the GMR element 222b and the GMR element 222d to the electric circuit device.

The main body M2 consisting of the chip package 11 and the sensor chip 22 configured as described above is accommodated in the through hole TH ₁₃ of the bias magnet 13, as in the first embodiment. Gear G is rotated below it (see FIG. 18). In this embodiment, the distance between the GMR element 222a and the GMR element 222c in the longitudinal direction is set to 1/2 the pitch of the convex portion G1 of the gear G. Therefore, when the gear G rotates, the voltage VoA changes sinusoidally, similar to the first embodiment. On the other hand, the distance between the GMR element 222b and the GMR element 222d in the longitudinal direction is also set to 1/2 the pitch of the convex portions G1 of the gear G. Therefore, when the gear G rotates, the voltage VoB changes sinusoidally, similar to the first embodiment. However, in this embodiment, the distance between the GMR elements 222a and 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 elements 222c and 222d in the front-rear direction is set to 1/4 of the pitch of the convex portion G1 of the gear G. The interval is set to 1/4 of the pitch of the convex portions 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, as in the first embodiment, the rotation of the gear G can be detected with high accuracy. Furthermore, highly accurate sinusoidal output signal A (voltage VoA) and cosine waveform output B (voltage VoB) representing the rotation of gear G can be obtained, and arc tangent (arc tangent) using output signals A and B can be obtained. The rotation angle of the gear G can be easily calculated by the tangent) calculation.

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

Here, in the magnetic sensor MS of FIG. 28, FIG. 29 shows changes in the offset of the output voltages of the sensor chips SCA and SCB when the bias magnet BM is shifted in its longitudinal direction. Further, in the magnetic sensor MS, FIG. 30 shows a change in the offset of the output voltage when the bias magnet BM is shifted in the lateral direction. Further, in the magnetic sensor 2 according to 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. Furthermore, in the magnetic sensor 1, 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.

As shown in FIGS. 29 and 30, in the magnetic sensor MS, when the position of the bias magnet BM with respect to the GMR elements Ra to Rd of both sensor chips SCA and SCB shifts, the output voltages of the sensor chips SCA and SCB change greatly. . Furthermore, the manner (direction) of change in the output voltages of the sensor chips SCA and SCB is opposite. Therefore, it is difficult to maintain high precision in the arrangement of the bias magnets BM. On the other hand, as shown in FIGS. 20 and 21, in the magnetic sensor 2, even if the position of the bias magnet 13 relative to the GMR elements 222a to 222d is slightly shifted, the output voltage does not change much. Therefore, even if the arrangement accuracy of the bias magnet 13 is somewhat low, the rotation detection accuracy of the gear G by the magnetic sensor 2 can be maintained high. Therefore, the manufacturing cost of the magnetic sensor 2 can be reduced.

Furthermore, the implementation of the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the purpose of the present invention.

For example, as shown in FIG. 22, two main bodies M1 are placed facing each other and shifted in the front-rear direction by a distance corresponding to 1/4 of the pitch of the convex parts G1 of the gear G, and a pair of these main bodies The portions M1, M1 may be accommodated in the through hole _TH13 of the bias magnet 13. This also provides substantially the same effects as the second embodiment.

Further, in the above embodiment, a cylindrical magnet is used as the bias magnet 13, but instead of this, as shown in FIG. May be adopted.

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

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

Further, in the above embodiment, a GMR element using a granular thin film is used as a magnetic field intensity sensing 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 a magnetic field strength detection type GMR element which is an in-plane magnetic sensing element. This artificial lattice type GMR element is described in, for example, the Journal of the Japanese Society of Applied Magnetics Vol. 15, No. 51991, P813-821, a laminate in which magnetic layers and nonmagnetic layers with a thickness of several angstroms to several tens of angstroms are alternately laminated, as described in the paper entitled "Magnetoresistance effect of artificial lattice", 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 embodiments, the GMR elements 122a to 122d or the GMR elements 222a to 222d, which are formed by folding back a granular thin film and extending in a straight line, are used as the GMR elements. However, instead of these GMR elements 122a to 122d or 222a to 222d, spiral GMR elements may be used. These spiral GMR elements are made by extending a linear granular thin film (or artificial lattice film) spirally from the outside to the inside on an insulating substrate. This is an extended 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 does not need to be the gear G, and can also be applied to detect rotation of a disc-shaped member having one or more recesses on the outer peripheral surface of the disc-shaped member. Furthermore, the magnetic sensor 1 and the magnetic sensor 2 described above can also be applied to the detection of a linearly moving moving object that is made of a magnetic material and has protrusions (teeth) or recesses, even if it is not a rotating object. obtain. In this case as well, the magnetic sensor 1 and the magnetic sensor 2 described above may be arranged to face the uneven portion of the moving body.

DESCRIPTION OF SYMBOLS 1... Magnetic sensor, 2... Magnetic sensor, 11... Chip package, 12... Sensor chip, 13... Bias magnet, 13A... Bias magnet, 22... Sensor chip, 121... Insulating substrate, 122a... GMR element, 122b... GMR element, 122c...GMR element, 122d...GMR element, 124...wiring pattern, 125...differential amplifier, 221...insulating substrate, 222a...GMR element, 222b...GMR element, 222c...GMR element, 222d...GMR element, 224...wiring pattern , G...gear, G1...convex part, G2...concave part, Had...magnetic field strength, Hbc...magnetic field strength, Z...area

Claims (6)

A magnetic sensor that outputs a signal according to the distance to a magnetic body,
A pair of flat permanent magnets parallel to a predetermined first direction and parallel to a second direction perpendicular to the first direction, and arranged in a third direction perpendicular to the first direction and perpendicular to the second direction. a pair of permanent magnets that are spaced apart and have one end in the second direction magnetized as a north pole and the other end in the second direction as a south pole, the one end or the other end; magnetic field forming means for applying magnetic fields directed in opposite directions to the predetermined space so that the magnetic field strength in the predetermined space extending in the first direction is smaller than the magnetic field strength in the surrounding area; and,
At least a pair of giant magnetoresistive elements, the giant magnetoresistive elements whose electric resistance value decreases as the intensity of the applied magnetic field increases, are arranged with respect to the third direction in the predetermined space. an electric circuit arranged in a predetermined vertical plane, spaced apart by a predetermined first distance in a predetermined first direction, and connected in a bridge manner;
Magnetic sensor with. The magnetic sensor according to claim 1,
comprising two sets of the electric circuits, each arranged within the predetermined plane;
A magnetic sensor, wherein the two sets of electric circuits are arranged so as to be shifted by a predetermined second distance in the first direction. The magnetic sensor according to claim 1 or 2,
The magnetic field forming means is a rectangular cylindrical permanent magnet extending in the second direction, one end surface of which in the axial direction is magnetized to a north pole, and the other end surface is magnetized to a south pole. ,
A magnetic sensor, wherein the electric circuit is housed inside the cylindrical magnetic field forming means. The magnetic sensor according to claim 3 ,
The pair of giant magnetoresistive elements are configured of a granular thin film having a linear portion extending in the second direction. The magnetic sensor according to any one of claims 1 to 4,
A magnetic sensor, wherein the electric circuit is arranged with respect to the magnetic field forming means so that the electric resistance value of the electric circuit is maximized. The magnetic sensor according to any one of claims 1 to 5,
A magnetic sensor applied to detecting the operation of a magnetic body having at least one convex portion or concave portion that moves in the first direction.

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