JP2002303536A - Rotation angle detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detecting sensor with excellent sensitivity, requiring small exclusive space and with large variation of the output of voltage from the sensor. SOLUTION: Pairs of GMR elements Ra1 and Ra2, and Rb1 and Rb2 are located opposite to each other with the line of the rotation axis of a magnet in-between in such a way that the directions of magnetization of pinned magnetic layers of the GMR elements Ra1 and Ra2, and Rb1 and Rb2 are opposite to each other. The rotation angel of the rotation axis is detected by the variation of values of the resistance of the GMR elements Ra1, Ra2, Rb1 and Rb2 generated in the angels between the directions of magnetization g1, g2, g3 and g4 of the pinned magnetic layers and the direction of magnetization of free magnetic layers corresponding to the direction of the magnetic field Hex of the magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detection sensor, for example, a rotation angle detection sensor connected to a steering shaft of an automobile to detect a rotation angle of a steering wheel.

[0002]

2. Description of the Related Art A conventional rotation angle detecting sensor according to the present invention will be described with reference to FIGS. FIG. 17 is a plan view of a conventional rotation angle detection sensor, and FIG. 18 is a front view of a conventional rotation angle detection sensor.

A rotation angle detection sensor 21 of the prior art is a two-pole magnetized disk-shaped magnet having a neutral point m (shown by a two-dot chain line) fixed to a rotation shaft 22 and passing through the center of rotation. 23
And a wiring board provided so as to face the side edge surface 23a of the disk-shaped magnet 23 and face the side edge surface 23a of the magnet 23 at a position out of phase with respect to the rotation direction of the rotating shaft 22. It is constituted by Hall elements 25 and 26 fixed to 24.

The magnet 23 is disk-shaped and has a hole 23b at the center thereof. A rotating shaft 22 for transmitting the rotation of an external rotating body (not shown) is fitted into and fixed to the hole 23b. The disk of the magnet 23 is magnetized on two poles, an N pole and an S pole, such that the neutral point M passes through the center of the disk.

Two Hall elements 25 and 26 are provided.
The Hall elements 25 and 26 are electrically connected to the wiring board 24 by a known method such as soldering.
3a, and is fixed on the wiring board 24 at a position shifted by π / 2 (rad) with respect to the rotation direction of the rotation axis d of the rotation shaft 22.

A method of detecting a rotation angle of the rotation angle detection sensor 21 according to the prior art having the above-described configuration will be schematically described. Rotating shaft 22
Is rotated counterclockwise and the S pole of the disc-shaped magnet 23 comes closest to the Hall element 25, so that the magnetic flux B incident across the magneto-sensitive surface of the Hall element 25 becomes maximum.
The output of the hall element 25 takes the maximum value, and the rotating shaft 22 further rotates in the same direction so that the N pole of the magnet 23 is
, The output of the Hall element takes a minimum value because the density of the magnetic field lines in the opposite direction becomes maximum. In this way, the output of the Hall element 25 becomes a sine wave of one cycle per rotation as the rotating shaft 22 rotates in the same direction. The output of the Hall element 26 is π with respect to the rotation axis d of the rotation shaft 22.
Since it is arranged at a position shifted by / 2 (rad), a sine wave output having a phase shifted by π / 2 (rad) from the output of the Hall element 25 is generated. Using these two sine waves having a phase difference of π / 2 (rad), the rotation angle is detected using a known method.

[0007]

However, in the rotation angle sensor of the prior art described above, two Hall elements must be mounted around the magnet to secure the space, and the device becomes large as a whole. Along with
It is necessary to accurately determine the position accuracy of the element. Also, since a Hall element is used, the change in output voltage is generally 1 unit.
% Or less, the sensor sensitivity is poor, and it is necessary to use an amplifier having a large amplification factor of about 30 to 50 times.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation angle detection sensor having a good waveform accuracy, a small occupied space, a large change in sensor output voltage, and a high sensor sensitivity.

[0009]

SUMMARY OF THE INVENTION A rotation angle detection sensor according to the present invention has a GMR having a free magnetic layer and a pinned magnetic layer.
At least two pairs of elements are provided on a substrate, and the GMR of each pair is provided.
The elements are connected in series, and a magnet is rotatably arranged facing the GMR element.
A saturation magnetic field is applied to the element, a magnetic field is generated such that the direction of the magnetic field lines parallel to the GMR element surface rotates, and the pair of GMR elements oppose each other with the rotation axis of the magnet rotating axis interposed therebetween. And the GM
The directions of magnetization of the pinned magnetic layers of the R element are set to be opposite to each other, and the angle between the direction of the magnetization of the free magnetic layer and the direction of the magnetization of the pinned magnetic layer according to the direction of the line of magnetic force of the magnet is determined. The rotation angle of the rotating shaft is detected based on the change in the resistance value of the GMR element. According to this configuration, the elements can be arranged close to each other around the rotation axis, the space occupied by the elements is small, and the GMR element is used. Therefore, a rotation angle detection sensor having a large sensor output voltage output change and good sensor sensitivity can be obtained. .

Further, in the rotation angle detecting sensor according to the present invention, the paired GMR elements are arranged at symmetrical positions with respect to the rotation axis. With this configuration, the rotation angle can be detected more accurately.

Further, in the rotation angle detection sensor according to the present invention, the at least two pairs of the GMR elements are located on the same radius with respect to the rotation axis. With this configuration, four GMs
The R elements can be integrated around the rotation axis, and the rotation angle detection sensor can be further reduced in size.

In the rotation angle detecting sensor according to the present invention, the GMR elements of the at least two pairs of GMR elements are arranged at an angular interval of π / 2 (rad) around the rotation axis. With this configuration, π / 2 (ra
d) Two sine waves having different phases can be obtained, and a more accurate rotation angle can be detected.

Further, the rotation angle detecting sensor according to the present invention is arranged such that the magnetization directions of the pinned magnetic layers of all of the adjacent GMR elements are alternately closer to each other and farther away from each other. did. With this configuration,
Since the four bar magnets can be magnetized by a bar magnet block having a simple structure in which the north pole and the south pole are simply bundled so as to be opposite to each other, preparation for the magnetization becomes easier.

Further, in the rotation angle detecting sensor according to the present invention, the at least two pairs of the GMR elements are formed on the same substrate. With this configuration, since the film quality of each GMR element is the same, a GMR element having uniform electric and magnetic characteristics can be obtained, and a detection error due to variation of each element is eliminated, and more accurate rotation angle detection can be performed. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotation angle detection sensor according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a rotation angle detection sensor according to a first embodiment of the present invention, FIG. 2 is a front view of the rotation angle detection sensor, FIG. 3 is a plan view showing a sensor substrate of the rotation angle detection sensor, and FIG. 3 is an enlarged view of a portion D in FIG. 3, FIG. 5 is a sectional view taken along line 5-5 in FIG. 4, FIG. 6 is a view showing a method of magnetizing a GMR element on a sensor substrate of the rotation angle detection sensor, and FIG. FIG. 8 is a diagram showing the direction of magnetic lines of force emitted from a magnetizing rod magnet when magnetizing, FIG. 8 is a circuit diagram showing a circuit on a sensor substrate of the rotation angle detection sensor, and FIG. 9 is a diagram showing an output of an electrode A of the sensor substrate. FIG. 10 is a graph showing both the outputs of the electrodes A and B of the sensor substrate,
FIG. 11 is a diagram showing a modification of the rotation angle detection sensor according to the first embodiment.

The rotation angle detection sensor 1 according to the first embodiment of the present invention has a neutral point M (2) fixed to the rotation shaft 4 and passing through the center of rotation.
(Indicated by a dashed line), a disk-shaped magnet 2 magnetized into two poles, and an end face of the rotation axis 4 of the magnet 2 in a plane orthogonal to the rotation axis 4 of the disk-shaped magnet 2. The sensor substrate 3 is provided facing 4a.

The magnet 2 is a disk-shaped ferromagnetic material having a hole 2a in the center, and a rotating shaft 4 for transmitting rotation of a rotating body (not shown) such as stearing is fitted and fixed in the hole 2a. The rotation is made about the rotation axis C. The disk of the disk-shaped magnet 2 is magnetized on two poles, an N pole and an S pole, such that the neutral point M passes through the center C of the disk. Lines of magnetic force exit from the N pole of the magnet 2 and enter the S pole, and lines of magnetic force Hex associated with the magnetic field are generated on the lower surface of the disc-shaped magnet 2. Further, the GMR element Ra1R is generated by the magnet 2.
A saturation magnetic field is applied to a2, Rb1, and Rb2.

The sensor substrate 3 includes an electrode Vcc, an electrode A, an electrode B, an electrode GND and a GMR element R on a silicon substrate 3a.
a1, a GMR element Ra2, a GMR element Rb1, and a GMR element Rb2 are provided, and these electrodes and the GMR element are connected to a lead L1, a lead L2, a lead L3, a lead L4,
Lead L5 is connected. As shown in FIGS. 3 and 8, the electrode Vcc and one end of the GMR element Ra1 are connected by a lead L1, and the other end of the GMR element Ra1 is connected to the GMR element Ra.
2 is connected to one end of a lead L2.
Is connected to the electrode A, and the other end of the GMR element Ra2 is connected to the electrode GND by a lead L3. That is,
The GMR elements Ra1 and Ra2 are connected in series and
The electrode A is drawn out from between the R elements Ra1 and Ra2. The electrode Vcc and one end of the GMR element Rb1 are connected by a lead L4, and the other end of the GMR element Rb1 is
One end of the MR element Rb2 is connected by a lead L5, the lead L5 is also connected to the electrode B, and the other end of the GMR element Rb2 is connected to the electrode GND by a lead L3. That is, the GMR elements Rb1 and Rb2 are connected in series, and the electrode B is drawn out from between the two GMR elements Rb1 and Rb2. Both ends of the GMR elements Ra1 and Ra2 connected in series and the GMR elements Rb1 and Rb2 connected in series are connected to the electrode Vcc and the electrode GND, respectively. On the silicon substrate 3a,
Parts other than the electrodes A, B, Vcc, and GND are entirely coated with an insulating coating.

Each GMR element Ra1, Ra2, Rb1, R
b2 includes strip-shaped small resistors r1, r2, and r3 and folded electrodes e1 and e2, respectively. As shown in FIG. 4, the strip-shaped small resistor portions r1, r2, and r3 are connected in series, and the folded electrode e1 is formed. , E2, each small resistance part r1,
r2 and r3 are folded back and arranged so as to be parallel to each other. In addition, the center position of each GMR element is
Is substantially equidistant from a point C ′ where the rotation axis C intersects with the sensor substrate 3, and when the strip-shaped small resistance portions r1, r2, r3 of each GMR element are extended in the longitudinal direction, the point C ′ is almost
Pass through. Further, each GMR element has a pinned magnetic layer and a free magnetic layer, which will be described later, respectively.
In the GMR element Ra1 and GMR element Ra2 provided point-symmetrically with respect to the upper point C ′, the magnetization directions g1 and g2 of the pinned magnetic layer are opposite to each other. Similarly, the GMR element Rb1 and the GMR element Rb2 are also provided point-symmetrically with respect to the point C ′ on the sensor substrate 3, have a pinned magnetic layer and a free magnetic layer, and have the magnetization directions of the pinned magnetic layers opposite to each other. Orientation. Also, the GMR element Ra1
Connecting the center position of each of the GMR elements Ra2 with the GM
A line connecting the center positions of the R element Rb1 and the GMR element Rb2 intersects at right angles.

GMR elements Ra1, Ra2, Rb1, Rb
2, a base layer 5, an antiferromagnetic layer 7, a pinned magnetic layer 8, a nonmagnetic conductive layer 9, a free magnetic layer 10,
The protective layer 11 is sequentially laminated, and the electrode layer 6 is provided at both ends. The exchange coupling of the antiferromagnetic layer 7 and the pinned magnetic layer 8 causes pinning in the magnetization direction of the magnetized antiferromagnetic layer 7. The direction of magnetization of the magnetic layer 8 follows and is fixed in a direction perpendicular to the plane of the paper toward the back of the paper. The free magnetic layer 10 is formed of a ferromagnetic material, the magnetization direction is not fixed, and the direction of magnetization is determined by the direction of the magnetic field line Hex of the magnetic field of the magnet 2. At this time, if the direction of magnetization of the free magnetic layer 10 whose direction has been changed by the line of magnetic force Hex becomes the same as the direction of magnetization of the pinned layer 8, the GMR elements Ra1 and Ra
2, the resistance values of Rb1 and Rb2 are minimized, and when the direction of magnetization of the free magnetic layer 10 is opposite to the direction of magnetization of the pinned magnetic layer 8, the GMR elements Ra1, Ra2, Rb1, R
The resistance value of b2 becomes maximum. Regarding the GMR element Ra1, the direction of magnetization of the pinned magnetic layer 8 on the sensor substrate 3 depends on the direction of magnetization of the antiferromagnetic layer 7, and the band-shaped small resistance portion r
The direction perpendicular to the longitudinal direction of 1, r2 and r3 is directed to the direction of g1 in FIG. Other GMR elements Ra2,
The magnetization directions of the pinned layers of Rb1 and Rb2 are also fixed in the direction perpendicular to the longitudinal direction of the small resistance portions r1, r2, and r3, respectively.

A method of manufacturing the above-described sensor substrate 3 will be described. An alumina (aluminum oxide) layer 5 is formed as a base layer on the silicon substrate 3a by sputtering, and a PtMn layer as an antiferromagnetic layer 7 is formed thereon.
(Platinum manganese) alloy layer, Co as pinned magnetic layer 8
Fe (cobalt iron) alloy layer is used as nonmagnetic conductive layer 9
u (copper) layer, NiFe (nickel iron) alloy layer as free magnetic layer 10, Ta (tantalum) as protective layer 11
The layers are each successively laminated by sputtering.
The laminated film is patterned by photolithography, and four GMR elements Ra1, Ra2, Rb1, Rb2 are formed.
, Small band resistance portions r1, r2, and r3 are formed. Finally, a Cr (chromium) layer and an Au (gold) layer are laminated and formed as electrodes 6 by sputtering again, and four GMR elements Ra1, Ra2, Rb are formed by photolithography.
The pattern formation of the electrodes 6 of 1 and Rb2 is performed. Next, each G
Magnetization is performed to fix the pinned magnetic layers 8 of the MR elements Ra1, Ra2, Rb1, and Rb2. As shown in FIG. 6, four prismatic bar magnets 12a, 12b, 12c, 12
The poles d are bundled so that the polarities of the magnetic poles are opposite to each other to form a bar magnet block 12, and the lower end surface of the bar magnet block 12 is brought close to the surface of the sensor substrate 3. At this time, as shown in FIG. 7, four magnetic poles N, S, N, S exposed on the lower end surface form magnetic lines of force H1, H2, H3 close to each other in four directions, as shown in FIG. , H4 are generated. A magnetic field is applied to each of the GMR elements Ra1 and Ra2 so as to generate magnetic field lines H1 and H2 in opposite directions, and a magnetic field is applied to the GMR elements Rb1 and Rb2 so as to generate magnetic field lines H1 and H2 in opposite directions. Is done. The magnet block 12 is held in a state in which the bar magnet block 12 is brought close to the sensor substrate 3, and is annealed at a high temperature for several hours in a vacuum to complete the magnetization. By this magnetization step, the GMR element Ra1 and the GMR element
The magnetization directions of the pinned magnetic layer of the element Ra2 are fixed to g1 and g2, which are opposite to each other. Also, the GMR element Rb1
And the magnetization directions of the pinned magnetic layers of the GMR element Rb2 are also fixed to g3 and g4, which are opposite to each other. In this magnetizing step, the magnet bar 12 can be formed by a simple method of bundling the four bar magnets 12a, 12b, 12c, and 12d so that the polarities of the magnetic poles are opposite to each other.
Preparation for magnetization is simplified. In addition, the material of each layer described above is not limited to the material described above.

Next, the operation of the rotation angle detection sensor according to the first embodiment of the present invention will be described. The rotation of an external rotator such as a steering is transmitted to the rotating shaft 4, and when the disk-shaped magnet 2 is rotated, the magnetic field lines H generated on the lower surface of the disk-shaped magnet 2 are generated.
ex rotates. The magnet lines 2 are formed sufficiently large compared to the substrate 3 so that the lines of magnetic force Hex are parallel and uniform on the surface of the sensor substrate 3 or can be regarded as parallel and uniform. The lines of magnetic force Hex correspond to the GMR elements Ra.
1, Ra2, Rb1, Rb2, giving a magnetic field sufficient to saturate them. Electrode V of sensor substrate 3
A constant voltage of 5 V is applied to cc, and the electrode GND is connected to the ground. The electrode A is a GMR element Ra1,
An electrode for extracting a voltage output at the connection point of Ra2 as an A output, and an electrode B is an electrode for extracting a voltage output at a connection point of the GMR elements Rb1 and Rb2 as a B output. It should be noted that, although not shown, a 2.5 V
Is connected to one input terminal, and is connected to a differential amplifier having an amplification factor of 12 and a reference voltage of 2.5 V.

First, in FIG. 3, the direction Hex of the line of magnetic force of the magnet 2 is the same as the reference direction Z (corresponding to an angle of 0 rad) from the lower GMR element Ra2 to the upper GMR element Ra1 on the surface of the sensor substrate 3. Is considered, the magnetization direction g1 of the pinned layer 8 of the GMR element Ra1 is
And the direction of the line of magnetic force Hex are perpendicular, so the GMR element Ra
The resistance value of 1 is an intermediate value between the maximum value and the minimum value of the resistance change due to the magnetic flux Hex, and the direction g2 of the pinned magnetic layer 8 of the GMR element Ra2 is also perpendicular to the direction of the magnetic flux Hex. Has an intermediate value between the maximum value and the minimum value. Since the GMR elements Ra1 and Ra2 are formed on the same substrate under substantially the same conditions, their magnetic characteristics are considered to be substantially the same.
Since the resistance change due to the magnetic field Hex of 1 and Ra2 is the same, the maximum value, the minimum value, and the intermediate value between the maximum value and the minimum value are almost the same. Therefore, the line of magnetic force Hex of the magnet 2
Is the same as the reference direction Z on the sensor substrate 3,
As described above, the resistance values of the GMR elements Ra1 and Ra2 have the same value. Therefore, a voltage of about 2.5 V is input to the differential amplifier. Since it is 0, the reference value of 2.5 V is applied, and the A output of the electrode A becomes 2.5 V. Next, when the line of magnetic force Hex of the magnet 2 rotates counterclockwise by the rotation angle π / 2 (rad), the direction of the line of magnetic force Hex and the direction g1 of magnetization of the pinned magnetic layer 8 of the GMR element Ra1 become the same.
The resistance value of the GMR element Ra1 is reduced to a minimum value, that is, a value smaller than the initial resistance value by 2.5% because the GMR element having a change rate of the resistance value of 5% is used in this case. The resistance value of the GMR element Ra2 is the maximum value because the direction g2 of magnetization of the pinned magnetic layer 8 of the GMR element Ra2 and the line of magnetic force Hex are opposite, that is, the rate of change of the resistance value of the GMR element is 5%. Therefore, it takes a value 2.5% larger than the initial resistance value. Therefore, a voltage of about 2.563 V is input to the differential amplifier, and the voltage difference between the input terminals of the differential amplifier is 0.063 V, which is amplified by a factor of 12 to obtain a signal of 0.76 V. When 2.5 V is applied, the A output of the electrode A becomes 3.26 V at the maximum. Next, the line of magnetic force Hex of the magnet 2 further moves in the counterclockwise direction by π / 2 (ra
d) When rotated, that is, when rotated by a rotation angle π (rad) counterclockwise from the reference direction Z, the direction of the magnetic force line Hex and the GM
The magnetization direction g1 of the pinned magnetic layer 8 of the R element Ra1 and the magnetization direction g of the pinned magnetic layer 8 of the GMR element Ra2
2 is a right angle, so that the A output becomes about 2.5 V as in the case where the magnetic force line Hex of the magnet 2 and the reference direction Z match. Next, the line of magnetic force Hex of the magnet 2 is further increased by π in the counterclockwise direction.
/ 2 (rad), that is, 3π / 2 (rad) counterclockwise from the reference direction Z, the magnetic field line Hex
Is opposite to the direction g1 of magnetization of the pinned magnetic layer 8 of the GMR element Ra1, the resistance of the GMR element Ra1 increases and takes the maximum value. The resistance value of the GMR element Ra2 takes a minimum value because the direction g2 of magnetization of the pinned magnetic layer 8 of the GMR element Ra2 and the line of magnetic force Hex are the same.
Accordingly, the output A of the electrode A was calculated to be the same as described above, and became the minimum value of about 1.74V. Next, the magnetic field line H of the magnet 2 is further increased.
ex rotates counterclockwise by π / 2 (rad), that is,
When the rotation is 2π (rad) in the counterclockwise direction from the reference direction Z, one cycle ends, the state becomes the same as the initial state, and the A output becomes about 2.5V. When the magnetic force line Hex of the magnet 2 is further rotated, the output A of the electrode A repeats the output change in the first cycle.

The B output from the B electrode is applied to the GMR element Rb
1, Rb2 magnetization directions g3, g4 of the pinned magnetic layer 8
Is advanced in the π / 2 (rad) counterclockwise direction from the magnetization directions g1 and g2 of the pinned magnetic layers 8 of the GMR elements Ra1 and Ra2, so that π / 2 (ra) is obtained from the A output from the A electrode.
d) The output voltage is advanced. The rotation angle of the magnet 2 is detected by a known method from the A output and the B output shifted from each other by π / 2 (rad). As described above, in the rotation angle detection sensor according to the first embodiment of the present invention, the GMR element in which the elements can be arranged close to each other around the rotation axis, occupies a small space, and has a resistance change rate of about 5% is used. Since it is used, an output change of the sensor output voltage is large, the sensor sensitivity is good, an amplifier with a small amplification factor can be used, and an accurate rotation angle can be detected.

In the first embodiment, the case where four GMR elements are provided on the same substrate is described. In this case, the four GMR elements Ra1, Ra2, Rb1, and Rb2 can be arranged close to each other. Therefore, the characteristics can be easily made uniform by making the thicknesses of the respective layers shown in FIG. 5 substantially the same, and the accuracy of the rotation angle detection sensor can be easily increased. However, the present invention is not limited to this. 11, GMR elements j1, j2, j3, and j4 are mounted on four substrates S1, s2, s3, and s4, respectively, and the GMR elements j1, j2, and The magnetization directions f1, f2, f3, and f4 of the pinned magnetic layers j3 and j4 are π / 2.
(Rad) Four substrates s1 and s
2, s3, and s4 may be fixed to form the sensor substrate 13 to constitute a rotation angle detection sensor.

Next, a rotation angle detection sensor according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 12 is a plan view showing a sensor substrate of a rotation angle detection sensor according to a second embodiment of the present invention, and FIGS.
15 is a circuit diagram showing an R element and a lead portion, FIG. 15 is a graph showing the output of the electrode A + based on the voltage of the electrode A− of the GMR element, and FIG. 16 is based on the voltage of the electrode A− of the GMR element. The α output which is the voltage of the electrode A + and the electrode B−
Respectively showing the β output which is the voltage of the electrode B + with respect to the voltage of FIG. In the description of the second embodiment, parts that are the same as or similar to the first embodiment are referred to by their names or numbers, description thereof is omitted, and similar descriptions are omitted.

The configuration of the rotation angle detection sensor according to the second embodiment of the present invention is different from the rotation angle detection sensor according to the first embodiment only in the sensor substrate 14, so that only the description of the sensor substrate 14 and its operation will be described. explain.

The sensor substrate 14 has electrodes Vcc1, Vcc2, A +, A-, and Vcc1 on a silicon substrate 14a.
Electrode B +, electrode B-, electrode GND1, electrodes GND2 and G
An MR element ra1, ra2, ra3, ra4 and a GMR element rb1, rb2, rb3, rb4 are provided, and these electrodes and the GMR element are connected to the lead portions l1, l2, l3.
14, 15, 16, 17, 17 ′ and 18 are connected. The GMR element ra1 and the GMR element ra2 are connected in series via a lead l2, and the electrode Vcc1 and the electrode GN
D1 and D1 are connected via leads l1 and l4.
The MR element ra3 and the GMR element ra4 also have a lead l3.
And the electrode Vcc1 and the electrode GND1
Are connected via the leads l1 and l4.
That is, GMR is provided between the electrode Vcc1 and the electrode GND1.
An element in which the element ra1 and the GMR element ra2 are connected in series and an element in which the GMR element ra3 and the GMR element ra4 are connected in series are connected in parallel. Similarly, the GMR element r
b1 and the GMR element rb2 are connected in series via a lead 16 and the electrodes Vcc2 and GND2 are connected via leads 15 and 18; the GMR element rb3 and the GMR element rb4 also have a lead 17 , 17 ', and connected between the electrode Vcc2 and the electrode GND2 via the leads 15, 18. That is, the GMR element rb is provided between the electrode Vcc2 and the electrode GND2.
1 and a GMR element rb2 connected in series, and a GMR element rb3 and a GMR element rb4 connected in series are connected in parallel. On the silicon substrate 14a, the electrodes A +, A-, B +, B-, Vcc1, Vcc2, GND
Parts other than 1 and GND2 are entirely coated with insulation.

Each of the GMR elements is connected in series with a small band-shaped resistance portion folded back, and a GMR element ra1 and a GMR element ra are connected.
3, GMR element ra2 and GMR element ra4, GMR element rb1 and GMR element rb3, GMR element rb2 and GMR
The elements rb4 are arranged adjacent to each other so that the strip-shaped small resistance portions are parallel to each other, and the magnetization directions of the pinned magnetic layers 8 are opposite to each other. The center position of each GMR element is located at a position substantially equidistant from a point C ″ where the rotation axis C of the rotating shaft 4 intersects the sensor substrate 14, and the longitudinal direction of the band-shaped small resistance portion of each GMR element is When extended, it almost passes through point C ''. GMR elements ra1 and ra2 and G
MR elements ra3, ra4 and GMR elements rb1, rb2
The GMR elements rb3 and rb4 are provided at substantially point-symmetric positions with respect to a point C ″ on the sensor substrate 14, and the magnetization directions of the pinned magnetic layers 8 are opposite to each other. The GMR element ra1 and the GMR element ra2
Lines connecting the respective center positions, GMR elements rb1 and GM
A line connecting the center positions of the R elements rb2 intersects at right angles. Further, the GMR element ra3 and the GMR element ra
4 A line connecting the center positions of the GMR elements rb3 and G
A line connecting the center positions of the MR elements rb4 intersects at right angles.

Next, the operation of the rotation angle detection sensor according to the second embodiment of the present invention will be described. The rotation of the external rotator is transmitted to the rotation shaft 4, and when the disk-shaped magnet 2 is rotated, the direction of the magnetic force line Hex generated on the lower surface of the disk-shaped magnet 2 rotates. The lines of magnetic force Hex exist parallel to the surface of the sensor substrate 14, and the GMR elements ra1, ra2, ra3, ra4,
The lines of magnetic force Hex are given to rb1, rb2, rb3, and rb4. A constant voltage of 5 V is applied to the electrodes Vcc1 and Vcc2, and the electrodes GND1 and GND2 are connected to the ground. An electrode A + is an electrode for extracting a voltage output at a connection point of the GMR elements ra1 and ra2, and an electrode A− is a GMR element.
This is an electrode for extracting a voltage output at a connection point between the elements ra3 and ra4. The voltage between the electrode A + and the electrode A- is input to a differential amplifier having an amplification factor of 6 and a reference voltage of 2.5 V (not shown). And use it as α output. The electrode B + is an electrode for extracting a voltage output at a connection point between the GMR elements rb1 and rb2, and the electrode B− is an electrode for extracting a voltage output at a connection point between the GMR elements rb3 and rb4. Although not shown here, the voltage is input to a differential amplifier having an amplification factor of 6 and a reference voltage of 2.5 V, taken out as β output, and used together with α output for rotation angle detection. still,
Since the differential amplifier is used, when the output value changes with the same tendency due to a temperature change or noise, the influence can be canceled.

In FIG. 12, first, the direction of the magnetic force line Hex of the magnet 2 is lower than the GMR on the surface of the sensor substrate 14.
Considering the case where the reference direction Z1 (corresponding to the angle 0 rad) from the element ra2 to the upper GMR element ra1 is the same, the GMR elements ra1, ra2, ra3, ra4
Since the directions of magnetization of the free magnetic layers 10 of rb1, rb2, rb3, and rb4 follow the directions of the lines of magnetic force Hex, when the direction of magnetization h1 of the pinned magnetic layer 8 of the GMR element ra1 is perpendicular to the direction of the lines of magnetic force Hex, The resistance value of the GMR element ra1 is an intermediate value between the maximum value and the minimum value of the resistance change depending on the direction of the magnetic field line Hex, and the magnetization direction h2 of the pinned magnetic layer 8 of the GMR element ra2 is perpendicular to the direction of the magnetic line Hex. Therefore, the resistance value of the GMR element ra2 is also an intermediate value between the maximum value and the minimum value. GMR elements ra1, ra2
Are formed on the same substrate under substantially the same conditions, their magnetic properties are considered to be substantially the same, and the resistance changes of the GMR elements ra1 and ra2 due to the direction of the magnetic force line Hex are also the same. , The minimum value, and the intermediate value between the maximum value and the minimum value are almost the same. Therefore, magnet 2
Is the same as the reference direction Z1.
The output voltage at the electrode A + is the voltage 5 applied to the electrode Vcc.
It becomes 2.5V which is half of V. The output voltage at the electrode A- is also 2.5V. Therefore, the α output, which is the voltage of the electrode A + based on the electrode A−, is 2.5V. That is, the voltage difference on the input terminal side of the differential amplifier is 0 V, and even if amplified, it is 0 V, and a reference value of 2.5 V is output.

Next, when the direction of the line of magnetic force Hex of the magnet 2 rotates counterclockwise from the reference direction Z1 by a rotation angle π / 2 (rad), the magnetization direction h1 of the pinned magnetic layer 8 of the GMR element ra1 becomes Hex is the opposite direction,
The resistance value of the GMR element ra1 takes the maximum value, and the magnetization direction h2 of the pinned magnetic layer 8 of the GMR element ra2 is
Since the direction is the same as the direction of ex, the resistance value of the GMR element ra2 becomes the minimum value, and the output of the electrode A + decreases and takes the minimum value. That is, using a GMR element having a resistance change rate of 5%,
5VX0.975 / (1.025 + 0.975) = 2.
The output is 438V. Further, since the magnetization direction h3 of the pinned layer of the GMR element ra3 is in the same direction as the line of magnetic force Hex, the resistance value of the GMR element ra3 becomes the minimum value, and GM
Since the direction h4 of magnetization of the pinned magnetic layer 8 of the R element ra4 is opposite to the direction of the line of magnetic force Hex, the GMR element ra3
Has the maximum value, and the output voltage of the electrode A- rises to the maximum value. That is, 5VX1.025 / (1.025
+0.975) = 2.563V. Therefore,
The voltage difference between the input terminals of the differential amplifier is 2.563-2.43.
8 = 0.125, which is amplified by a factor of 6 to obtain a signal of 0.75V. When the reference value of 2.5V is added, the α output becomes the maximum value of 3.25V.

Next, when the direction of the line of magnetic force Hex of the magnet 2 further rotates π / 2 (rad) in the counterclockwise direction, ie, when the rotation angle π (rad) rotates counterclockwise from the reference direction Z1, the direction of the line of magnetic force Hex becomes Since the direction and the direction h1 of magnetization of the pinned magnetic layer 8 of the GMR element ra1 and the direction h2 of magnetization of the pinned magnetic layer 8 of the GMR element ra2 are at right angles, the magnetic field line Hex of the magnet 2 and the reference direction Z1 coincide. As before, the output voltage of the electrodes A + and A- becomes 2.5V. Therefore, the α output becomes 2.5 V similarly to the above.

Next, when the direction of the magnetic force line Hex of the magnet 2 further rotates counterclockwise by π / 2 (rad), that is, by 3π / 2 (rad) counterclockwise from the reference direction Z1, the GMR element ra1 H1 of the magnetization of the pinned layer
Is the same as the direction of the magnetic force line Hex, the resistance value of the GMR element ra1 becomes the minimum value, and the magnetization direction h2 of the pinned magnetic layer 8 of the GMR element ra2 and the direction of the magnetic force line Hex become opposite. The resistance value of the element ra2 takes the maximum value, and the output voltage of the electrode A + rises to 2.563V.
become. In addition, since the magnetization direction h3 of the pinned magnetic layer 8 of the GMR element ra3 is opposite to the direction of the line of magnetic force Hex, the resistance value of the GMR element ra3 becomes the maximum value, and the magnetization of the pinned magnetic layer 8 of the GMR element ra4. Is the same as the direction of the line of magnetic force Hex, the resistance value of the GMR element ra4 becomes the minimum value, and the output voltage of the electrode A- rises to 2.438V. Therefore, the α output takes the minimum value.
That is, the voltage difference between the input terminals of the differential amplifier is 2.438 V
-2.563V = -0.125V, which is amplified by a factor of 6 to obtain a signal of -0.75V. When the reference value of 2.5V is added, the α output becomes the minimum value of 1.75V.

Next, when the direction of the line of magnetic force Hex of the magnet 2 further rotates by π / 2 (rad) in the counterclockwise direction, that is, when the rotation angle is rotated by 2π (rad) in the counterclockwise direction from the reference direction Z1, the direction of the line of magnetic force Hex becomes Since the direction and the reference direction Z1 coincide with each other, the state is the same as the initial state of the rotation of the direction of the line of magnetic force Hex, and the output voltages of the electrodes A + and A- become 2.5V.
Therefore, the α output becomes 2.5V. This completes one cycle, and the rotation of the direction of the line of magnetic force Hex further becomes α in the first cycle.
The output changes repeatedly.

The change in the output voltage of the electrode B + depends on the magnetization directions i1, i1 of the pinned magnetic layer 8 of the GMR elements rb1, rb2.
The relationship between i2 and the direction of the line of magnetic force Hex is the GMR element ra
1, ra2 magnetization directions h1, h2 of the pinned magnetic layer 8
And the direction of the line of magnetic force Hex, it is moving in the π / 2 (rad) counterclockwise direction due to the change in the output voltage of the electrode A +. Electrode B
The change of the output voltage of-also indicates the magnetization directions i3 and i4 of the pinned magnetic layers 8 of the GMR elements rb3 and rb4 and the lines of magnetic force Hex.
Is more advanced in the counterclockwise direction by π / 2 (rad) than the relationship between the magnetization directions h3 and h4 of the pinned magnetic layers 8 of the GMR elements ra3 and ra4 and the direction of the line of magnetic force Hex. From the change in the output voltage of-, π / 2 (rad)
Moving in a counterclockwise direction. Therefore, the β output, which is the voltage of the electrode B + based on the electrode B−, is π / 2 (rad) more than the α output, which is the voltage of the electrode A + based on the electrode A−.
Moving in a counterclockwise direction. The rotation angles of the magnets 2 are π /
It is detected by a known method from the sine wave values of the α output and β output shifted by 2 (rad). As described above, the output change between the α output and the β output is 1.5 V (maximum value−minimum value), and the first implementation is performed despite the fact that a differential amplifier having a half amplification factor is used. The output change (maximum value-minimum value) of the A output and the B output of the form can be made substantially equal to
The sensor sensitivity is doubled. Further, since it is not necessary to use a differential amplifier having a small input offset voltage, it can be produced at low cost.

[0037]

As described above, the rotation angle detecting sensor of the present invention has a GM having a free magnetic layer and a pinned magnetic layer.
At least two pairs of R elements are provided on a substrate, each pair of GMR elements is connected in series, a magnet is rotatably arranged facing the GMR element, and a magnetic field of the magnet is generated in the direction of the substrate surface. The paired GMR elements are arranged so as to be opposed to each other with the rotation axis of the rotation axis of the magnet interposed therebetween.
The pinned magnetic layers of the R element have the magnetization directions opposite to each other, and the GMR element generated by the angle between the magnetization direction of the free magnetic layer and the magnetization direction of the pinned magnetic layer according to the direction of the magnetic field of the magnet. The rotation angle of the rotation axis is detected by a change in the resistance value of the rotation axis, so that the elements can be arranged close to each other around the rotation axis and output a voltage having a predetermined phase difference to detect the rotation angle. Space is small,
A rotation angle detection sensor having a large sensor output voltage output change and a high sensor sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a rotation angle detection sensor according to a first embodiment of the present invention.

FIG. 2 is a front view of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 4 is an enlarged view of a portion D in FIG. 3;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 4;

FIG. 6 is a diagram illustrating a method of magnetizing a GMR element on a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 7 is a diagram showing directions of magnetic force lines emitted from a magnetizing rod magnet when magnetizing a GMR element on a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 8 is a circuit diagram showing a circuit on a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 9 is a graph showing an output of an electrode A of a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 10 is a graph showing both outputs of electrodes A and B on a sensor substrate of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a modification of the rotation angle detection sensor according to the first embodiment of the present invention.

FIG. 12 is a plan view showing a sensor substrate of a rotation angle detection sensor according to a second embodiment of the present invention.

FIG. 13 is a circuit diagram showing a set of GMR elements, electrodes, and leads on a sensor substrate of a rotation angle detection sensor according to a second embodiment of the present invention.

FIG. 14 is a circuit diagram showing another set of GMR elements, electrodes and leads on a sensor substrate of the rotation angle detection sensor according to the second embodiment of the present invention.

FIG. 15 shows an electrode A based on the voltage of the electrode A- of the present invention.
6 is a graph showing α output which is a + voltage.

FIG. 16 is a diagram illustrating an α output that is a voltage of an electrode A + based on a voltage of an electrode A− on a sensor substrate and an electrode based on a voltage of an electrode B− of a rotation angle detection sensor according to a second embodiment of the present invention. It is a graph which shows both the β output which is the voltage of B +.

FIG. 17 is a plan view of a conventional rotation angle detection sensor.

FIG. 18 is a front view of a conventional rotation angle detection sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation angle detection sensor 2 Magnet 3 Sensor substrate 3a Silicon substrate 4 Rotation axis 8 Pinned magnetic layer 10 Free magnetic layer 12 Bar magnet block C Rotation axis line Hex Magnetic field line g1, g2, g3, g4 Direction of magnetization of pinned magnetic layer Ra1 , Ra2, Rb1, Rb2 GMR element

Claims (6)

[Claims] At least two pairs of GMR elements each having a free magnetic layer and a pinned magnetic layer are provided on a substrate, and each pair of the GMR elements is connected in series, and is rotatable facing the GMR element. A magnet is provided, a saturation magnetic field is applied to the GMR element by the magnet, and a magnetic field is generated so that the direction of a magnetic line of force parallel to the GMR element surface is rotated. The pinned magnetic layers of the GMR element are arranged so as to be opposed to each other with the rotation axis of the rotation axis interposed therebetween, and the directions of magnetization of the pinned magnetic layers of the GMR element are opposite to each other, and the free magnetism follows the direction of the magnetic force line of the magnet. GMR generated by the angle between the direction of magnetization of the layer and the direction of magnetization of the pinned magnetic layer
A rotation angle detection sensor wherein a rotation angle of a rotation shaft is detected by a change in a resistance value of an element. 2. The rotation angle detection sensor according to claim 1, wherein said pair of said GMR elements are arranged at positions symmetrical with respect to said rotation axis. 3. The rotation angle detection sensor according to claim 1, wherein the at least two pairs of the GMR elements are located on the same radius with respect to the rotation axis. 4. The method according to claim 1, wherein each of said at least two pairs of said GMR elements comprises a π / 2 (r
3. The arrangement according to claim 2, wherein the arrangement is at an angular interval of ad).
The rotation angle detection sensor according to any one of the preceding claims. 5. The apparatus according to claim 1, wherein the directions of the magnetization directions of the pinned magnetic layers of all of the adjacent GMR elements approach each other and the directions of the directions further away alternately appear. The rotation angle detection sensor according to any one of the preceding claims. 6. The GMR element according to claim 1, wherein said at least two pairs of said GMR elements are formed on a same substrate.
The rotation angle detection sensor according to any one of the preceding claims.