WO2015008439A1

WO2015008439A1 - Rotation sensor

Info

Publication number: WO2015008439A1
Application number: PCT/JP2014/003436
Authority: WO
Inventors: 孝昌金原; 紀博車戸; 泰行奥田
Original assignee: 株式会社デンソー
Priority date: 2013-07-17
Filing date: 2014-06-27
Publication date: 2015-01-22
Also published as: DE112014003316T5; JP2015021795A; DE112014003316B4; JP6064816B2

Abstract

A rotation sensor has a plurality of magnetoelectric conversion units (10, 20), and each of the magnetoelectric conversion units has paired magnetoresistance effect elements (11-14, 21-24). The magnetization directions of the pinned layers provided to each of the paired magnetoresistance effect elements are different from each other by 180°. The paired magnetoresistance effect elements provided to each of the magnetoelectric conversion units are disposed side-by-side along the rotation direction of a rotating body and are disposed so as to be symmetrical in relation to a reference line extending from the axis of rotation of the rotating body so as to be perpendicular to the rotation direction. The paired magnetoresistance effect elements form bridge circuits, and the midpoint potentials of the bridge circuits are made to be signals based on the rotation state of the rotating body.

Description

Rotation sensor

Cross-reference of related applications

This disclosure is based on Japanese Application No. 2013-148785 filed on July 17, 2013, the contents of which are incorporated herein.

The present disclosure relates to a rotation sensor that detects a rotation state of a rotating body based on a change in magnetic flux whose direction periodically changes as the rotating body rotates.

Conventionally, for example, as shown in Patent Document 1, a magnetic member in which N poles and S poles are alternately arranged, and one or more pairs of vector detection type magnetoresistive effect elements facing the magnetic pole arrangement surface of the magnetic member, Have been proposed. One or a plurality of pairs of vector detection type magnetoresistive elements are arranged in a line substantially perpendicular to the magnetic pole arrangement direction of the magnetic member. Thereby, the phase of the magnetic flux which permeate | transmits all the vector detection type | mold magnetoresistive effect elements is the same.

However, in the magnetic position detection device, since the facing distance between each vector detection type magnetoresistive effect element and the magnetic member is different, the intensity of the magnetic flux passing through each vector detection type magnetoresistive effect element is different. Therefore, it may be difficult to detect the rotation state of the magnetic member (rotating body) with high accuracy based on an electric signal that depends on the resistance value of each vector detection type magnetoresistive element.

Japanese Unexamined Patent Publication No. 2006-23179

This disclosure is intended to provide a rotation sensor with improved detection accuracy of the rotation state of a rotating body.

A rotation sensor according to an aspect of the present disclosure is a rotation sensor that detects a rotation state of a rotating body based on a change in magnetic flux whose direction periodically changes with the rotation of the rotating body. Has a plurality of magnetoelectric conversion units that convert the change in magnetic flux that fluctuates into an electrical signal. Each of the plurality of magnetoelectric conversion units includes a pair of magnetoresistive elements. Each of the pair of magnetoresistive effect elements includes a pinned layer having a fixed magnetization direction, a free layer whose magnetization direction varies according to an external magnetic field, and a non-layer provided between the pinned layer and the free layer. A magnetic intermediate layer, and the resistance value varies depending on the magnetization directions of the pinned layer and the free layer. The magnetization directions of the pinned layers of the magnetoresistive elements forming a pair are different from each other by 180 °. The magnetoresistive effect elements forming a pair included in each of the plurality of magnetoelectric conversion units are arranged side by side along the rotation direction of the rotating body, and extend from the rotation axis of the rotating body so as to be orthogonal to the rotation direction. They are arranged symmetrically with lines. A bridge circuit is formed by each of the magnetoresistive effect elements forming a pair, and a midpoint potential of the bridge circuit is set as a signal based on the rotation state of the rotating body.

The rotation sensor can improve the detection accuracy of the rotating state of the rotating body by utilizing the midpoint potential of the bridge circuit as a signal based on the rotating state of the rotating body.

The above and other objects, configurations, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the following drawings. In the drawing
FIG. 1 is a perspective view schematically showing positions of a rotation sensor and a rotating body according to the first embodiment. FIG. 2 is a top view schematically showing positions of the rotation sensor and the rotating body. FIG. 3 is a schematic diagram showing the magnetization direction of the pinned layer. FIG. 4 is a circuit diagram showing a bridge circuit assembled by magnetoresistive elements. FIG. 5 is a timing chart showing the midpoint potential and the pulse signal. FIG. 6 is a schematic diagram showing a reference magnetic flux passing through an intersection. FIG. 7 is a graph showing fluctuations in resistance values of the magnetoresistive effect element and the midpoint. FIG. 8 is a top view illustrating a modification of the magnetoelectric conversion unit. FIG. 9 is a top view illustrating a modification of the magnetoelectric conversion unit. FIG. 10 is a top view illustrating a modification of the magnetoelectric conversion unit. FIG. 11 is a circuit diagram showing the first full bridge circuit. FIG. 12 is a circuit diagram showing a second full bridge circuit.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
(First embodiment)
A rotation sensor according to this embodiment will be described with reference to FIGS. In the following, a plane at the same height position where the rotator 200 and the rotation sensor 100 are arranged is defined as a specified plane, and a direction perpendicular to the specified plane and passing through the rotation center RC of the rotator 200 is indicated as an axial direction. A direction around the axial direction is indicated as a rotation direction, and a direction extending from the rotation center RC along the prescribed plane is indicated as a radial direction. The rotation axis is along the axial direction.

The rotation sensor 100 detects the rotation state of the rotating body 200 based on a change in magnetic flux whose direction periodically changes as the rotating body 200 rotates. The rotating body 200 has an annular shape, and an N pole 210 and an S pole 220 are formed on the outer ring surface at equal intervals along the rotation direction. As shown in FIGS. 1 and 2, the N pole 210 and the S pole 220 are alternately formed, and a magnetic flux flows from the N pole 210 to the S pole 220. The magnetic flux between the adjacent N pole 210 and S pole 220 flows so as to draw a semicircular locus. The rotation sensor 100 detects a periodic change due to the rotation of the magnetic flux that draws this semicircular locus.

The rotation sensor 100 includes a first magnetoelectric conversion unit 10 and a second magnetoelectric conversion unit 20 that convert changes in the direction of magnetic flux into electrical signals. The 1st magnetoelectric conversion part 10 has the

magnetoresistive effect elements

11 and 12 which make a pair, and the 2nd magnetoelectric conversion part 20 has the

magnetoresistive effect elements

21 and 22 which make a pair. The

magnetoresistive effect elements

11 and 12 forming a pair and the

magnetoresistive effect elements

21 and 22 forming a pair are arranged side by side along the rotation direction as shown in FIGS. Are symmetrically arranged on a reference line BL extending in the radial direction from the center. The

magnetoresistive elements

11 and 12 forming a pair are rotated in the rotational direction (strictly speaking, the rotation of the rotating body 200 at the intersection CP in the rotational direction where the reference line BL and the

magnetoresistive elements

11 and 12 are arranged). The

magnetoresistive elements

21 and 22 forming a pair are arranged in the rotational direction (strictly, the tangential direction) via the

magnetoresistive elements

11 and 12. The parallel direction corresponds to the tangential direction described above.

In the present embodiment, the lateral widths of the

magnetoresistive elements

11, 12, 21, and 22 in the rotational direction are the same. Therefore, if the lateral width of the

magnetoresistive effect elements

11, 12, 21, and 22 is L, the center of each of the

magnetoresistive effect elements

11 and 12 is L / 2 in the rotational direction (tangential direction) from the reference line BL (intersection CP). It is separated. The centers of the

magnetoresistive elements

21 and 22 are separated from the reference line BL (intersection CP) by 3L / 2 in the rotational direction (tangential direction). Thus, each of the

magnetoresistive effect elements

11, 12, 21, and 22 is separated from the reference line BL (intersection CP) by the width. Therefore, there is a phase difference between the magnetic flux that passes through the centers of the

magnetoresistive elements

11, 12, 21, and 22 and the magnetic flux that passes through the intersection CP.

As shown in FIG. 2, the

magnetoresistive elements

11 and 21 are located on the left side of the drawing with respect to the reference line BL, and the

magnetoresistive elements

12 and 22 are located on the right side of the drawing with respect to the reference line BL. Therefore, when the rotating body 200 rotates counterclockwise, the

magnetoresistive effect elements

11 and 21 are positioned upstream of the reference line BL, and the

magnetoresistive effect elements

12 and 22 are positioned downstream of the reference line BL. It becomes. Therefore, the magnetic flux that passes through the magnetoresistive effect element 21 has a phase that is 3L / 2 faster than the reference magnetic flux that passes through the reference line BL, and the magnetic flux that passes through the magnetoresistive effect element 11 has a phase that is L / 2 faster than the reference magnetic flux. Become. On the contrary, the magnetic flux passing through the magnetoresistive effect element 12 is delayed in phase by L / 2 than the reference magnetic flux, and the magnetic flux passing through the magnetoresistive effect element 22 is delayed in phase by 3 L / 2 from the reference magnetic flux. . On the contrary, when the rotating body 200 rotates clockwise, the

magnetoresistive effect elements

12 and 22 are located upstream from the reference line BL, and the

magnetoresistive effect elements

11 and 21 are located downstream from the reference line BL. Will be located. Therefore, the magnetic flux that passes through the magnetoresistive effect element 22 has a phase that is 3L / 2 faster than the reference magnetic flux, and the magnetic flux that passes through the magnetoresistive effect element 12 has a phase that is L / 2 faster than the reference magnetic flux. On the contrary, the magnetic flux passing through the magnetoresistive effect element 11 is delayed in phase by L / 2 from the reference magnetic flux, and the magnetic flux passing through the magnetoresistive effect element 21 is delayed in phase by 3 L / 2 from the reference magnetic flux. In the present embodiment, the case where the rotating body 200 rotates counterclockwise will be described. When the rotating body 200 rotates clockwise, the above-described relationship is established, and thus the description thereof is omitted.

Although not shown, each of the

magnetoresistive effect elements

11, 12, 21, and 22 includes a pinned layer having a fixed magnetization direction, a free layer whose magnetization direction varies according to an external magnetic field, and a pinned layer and a free layer. And a nonmagnetic intermediate layer provided on the substrate. The resistance value fluctuates depending on the magnetization direction of each of the pinned layer and the free layer. The resistance value fluctuates the lowest when the magnetization directions of the free layer and the pinned layer are parallel, and the resistance value varies most when the magnetization directions are antiparallel. Highly fluctuating. In the present embodiment, the intermediate layer has conductivity, and each of the

magnetoresistive elements

11, 12, 21, and 22 is a giant magnetoresistive element.

The magnetization directions of the pinned layers of each of the

magnetoresistive effect elements

11, 12, 21, and 22 are along the prescribed plane, and the magnetization directions of the pinned layers of each of the

magnetoresistive effect elements

11 and 12 forming a pair are in the radial direction. The magnetization direction of the pinned layer of each of the

magnetoresistive effect elements

21 and 22 that form a pair is along the rotational direction (strictly, the tangential direction thereof). Therefore, the magnetization direction of the pinned layer included in each of the

magnetoresistive effect elements

11 and 12 forming a pair is different from the magnetization direction of the pinned layer included in each of the

magnetoresistive effect elements

21 and 22 forming a pair by 90 ° (270 °). Yes. In addition, the magnetization directions of the pin layers of the

magnetoresistive elements

11 and 12 forming a pair are different from each other by 180 °, and the magnetization directions of the pin layers of the

magnetoresistive elements

21 and 22 forming a pair are different from each other by 180 °. Yes.

As shown in FIG. 3, when the magnetization direction is expressed by a clockwise angle θ from the reference line BL along the radial direction, the magnetoresistive effect element 11 has a magnetization direction of the pinned layer of 0 °, and the magnetoresistive effect element 12 is The magnetization direction of the pinned layer is 180 °. The magnetoresistive element 21 has a pinned layer with a magnetization direction of 90 °, and the magnetoresistive element 22 has a pinned layer with a magnetization direction of 270 °. Thus, the magnetization directions of the

magnetoresistive effect elements

11 and 12 forming a pair are antiparallel to each other, and the magnetization directions of the

magnetoresistive effect elements

21 and 22 forming a pair are antiparallel to each other. For this reason, when the resistance values of the two magnetoresistive elements are opposite to each other and one of the two magnetoelectric transducers has a small resistance value, the other resistance value is large.

As shown in FIG. 4, a bridge circuit is formed by the

magnetoresistive effect elements

11 and 12 and the

magnetoresistive effect elements

21 and 22 that form a pair, and the midpoint potential is changed to the rotational state of the rotating body 200. As a signal based on this, it is input to a processing circuit (not shown) located in the subsequent stage. The first half-bridge circuit is assembled by the

magnetoresistive effect elements

11 and 12 that form a pair of the first magnetoelectric conversion unit 10, and the magnetoresistive effect element 21 that forms a pair of the second magnetoelectric conversion unit 20. , 22 form a second half bridge circuit. As described above, the magnetization direction of the pinned layer included in each of the paired

magnetoresistive effect elements

11 and 12 and the magnetization direction of the pinned layer included in each of the paired

magnetoresistive effect elements

21 and 22 are 90 ° (270 °). ) Is different. Therefore, the phase difference between the midpoint potential of the first half bridge circuit (hereinafter referred to as the first midpoint potential) and the midpoint potential of the second half bridge circuit (hereinafter referred to as the second midpoint potential) is 90 °. (270 °). Therefore, if the first midpoint potential is a sine wave, the second midpoint potential is a cosine wave. The processing circuit described above has a threshold value (broken line shown in FIG. 5). By comparing this threshold value with the midpoint potential, the first midpoint potential is set as the first pulse signal, and the second midpoint potential is set as the second potential. Convert to 2-pulse signal.

Hereinafter, the characteristic points of the rotation sensor 100 and the effects thereof will be described with reference to FIGS. 6 and 7. As described above, the

magnetoresistive effect elements

11, 12, 21, and 22 are arranged side by side along the rotation direction (the tangential direction of the intersection CP). According to this, unlike the configuration in which a plurality of magnetoresistive elements are arranged in the radial direction perpendicular to the rotational direction instead of the rotational direction, the strength of the magnetic flux transmitted through each magnetoresistive element is the same. It becomes. However, in the case of this configuration, as described above, due to its own lateral width, there is a phase difference between the magnetic flux passing through the

magnetoresistive effect elements

11, 12, 21, and 22 and the reference magnetic flux passing through the intersection CP.

As shown in FIG. 6, the angle around the intersection CP from the reference line BL in the reference magnetic flux is a. When the center of the magnetoresistive effect element 11 is at the intersection CP, the resistance value of the magnetoresistive effect element 11 constituting the first half bridge circuit (hereinafter referred to as the first resistance value) is as shown by a broken line in FIG. The behavior of a sine wave depending on the angle a is shown. However, since the center of the magnetoresistive effect element 11 is deviated from the intersection CP, the first resistance value exhibits a behavior in which the phase is deviated from the sine wave as shown by the solid line in FIG. Similarly, when the center of the magnetoresistive effect element 12 is at the intersection CP, as indicated by a broken line in FIG. 7, the resistance value of the magnetoresistive effect element 12 constituting the first half bridge circuit (hereinafter referred to as the second resistance value). Indicates a behavior of a cosine wave depending on the angle a. However, since the center of the magnetoresistive effect element 12 is deviated from the intersection CP, the second resistance value exhibits a behavior in which the phase is deviated from the cosine wave as shown by the solid line in FIG.

As described above, each of the first resistance value and the second resistance value behaves with a phase shift from the angle a. The same applies to the resistance values of the

magnetoresistive elements

21 and 22 constituting the second half bridge circuit. However, as described above, the first half bridge circuit is assembled by the

magnetoresistive effect elements

11 and 12 forming a pair, the second half bridge circuit is assembled by the

magnetoresistive effect elements

21 and 22 forming the pair, and the midpoint potential is rotated. The signal is based on the rotation state of the body 200. According to this, the phase shift can be eliminated for the following reason.

As described above, the reference magnetic flux angle is a. An angle deviation from the reference magnetic flux in the direction of the magnetic flux passing through the centers of the paired

magnetoresistive elements

11 and 12 is defined as b. Further, the center value of the resistance value of each of the magnetoresistive effect elements forming the pair is Rc, the amplitude of the resistance change amount of each of the

magnetoresistive effect elements

11 and 12 forming the pair is R0, and the voltage supplied to the first half bridge circuit is V Then, the first midpoint potential is expressed as (R0 × sin (ab) + Rc) V / (R0 × sin (ab) + Rc + R0 × sin (a + b + 180 °) + Rc). To summarize this, the midpoint potential of the first half-bridge circuit is (−V / 2) (sin (a) × cos (b) / (cos (a) × sin (b) −Rc) −1). This corresponds to the resistance at the midpoint of the first half-bridge circuit (hereinafter referred to as the first midpoint resistance) (sin (a) × cos (b) / (cos (a) × sin (b) − It can be seen that it depends on Rc) -1).

Here, since b and Rc are constant in time, sin (b), cos (b), and Rc each have a constant value. For this reason, the first midpoint resistance depends only on a in terms of time, and FIG. 7 shows the behavior indicated by the alternate long and short dash line. That is, it shows behavior similar to a sine wave without phase shift. As described above, even if the phases of the magnetic fluxes transmitted through the paired

magnetoresistive elements

11 and 12 are different, the first midpoint potential is a value at which the phase shift is eliminated. Therefore, by using the first midpoint potential as a signal based on the rotation state of the rotator 200, the detection accuracy of the rotation state of the rotator 200 is improved.

Of course, the same argument can be applied to the

magnetoresistive elements

21 and 22 forming a pair. In this case, the same argument can be advanced by setting the angle deviation from the reference magnetic flux in the direction of the magnetic flux passing through the centers of the paired

magnetoresistive effect elements

21 and 22 to c. The resistance at the midpoint (hereinafter referred to as the second midpoint resistance) is a value with no phase shift. Therefore, by using the second midpoint potential as a signal based on the rotation state of the rotator 200, the detection accuracy of the rotation state of the rotator 200 is improved.

Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and can be implemented with various modifications.

In the present embodiment, the

magnetoresistive effect elements

11 and 12 forming a pair are arranged in the rotational direction (tangential direction) without any intervening therebetween, and the

magnetoresistive effect elements

21 and 22 forming the pair are

magnetoresistive effect elements

11 and 12. In the example shown in FIG. However, as shown in FIG. 8, the

magnetoresistive elements

21 and 22 forming a pair are arranged in the rotational direction (tangential direction) without any intervening elements, and the

magnetoresistive elements

11 and 12 forming a pair are magnetoresistive elements. It is also possible to adopt a configuration in which the rotation direction (tangential direction) is arranged via 21 and 22.

In the present embodiment, the first magnetoelectric conversion unit 10 includes a pair of

magnetoresistive effect elements

11 and 12, and the second magnetoelectric conversion unit 20 includes a pair of

magnetoresistive effect elements

21 and 22. An example is shown. However, the number of pairs of magnetoresistive effect elements forming a pair included in each of the

magnetoelectric conversion units

10 and 20 is not limited to the above example, and a plurality of pairs may be used. For example, as shown in FIGS. 9 and 10, the first magnetoelectric conversion unit 10 includes magnetoresistive effect elements 11 to 14 that form two pairs, and the second magnetoelectric conversion unit 20 forms a magnetoresistance that forms two pairs. A configuration having effect elements 21 to 24 can also be adopted. In this case, as shown in FIGS. 11 and 12, two first half-bridge circuits are formed by the two pairs of magnetoresistive effect elements 11 to 14, and thereby the first full-bridge circuit is formed. In addition, two second half-bridge circuits are formed by the magnetoresistive effect elements 21 to 24 forming two pairs, and the second full-bridge circuit is formed by these.

In the present embodiment, an example is shown in which the lateral widths of the

magnetoresistive elements

11, 12, 21, and 22 in the rotational direction are the same. However, the lateral widths in the rotational direction (tangential direction) of the magnetoresistive elements forming a pair are equal and the distances from the reference line BL (intersection CP) of the magnetoresistive elements forming the pair may be equal. Therefore, the lateral widths of all the magnetoresistive elements need not be equal.

In the present embodiment, the intermediate layer has conductivity, and each of the

magnetoresistive elements

11, 12, 21, and 22 is a giant magnetoresistive element. However, it is also possible to adopt a configuration in which the intermediate layer has insulating properties and each of the

magnetoresistive effect elements

11, 12, 21, and 22 is a tunnel magnetoresistive effect element.

Claims

A rotation sensor that detects a rotation state of the rotating body based on a change in magnetic flux whose direction periodically changes as the rotating body (200) rotates.
A plurality of magnetoelectric converters (10, 20) for converting a change in magnetic flux whose direction periodically changes into an electrical signal;
Each of the plurality of magnetoelectric conversion units has a pair of magnetoresistive effect elements (11 to 14, 21 to 24),
Each of the pair of magnetoresistive effect elements includes a pinned layer having a fixed magnetization direction, a free layer whose magnetization direction varies according to an external magnetic field, and a non-layer provided between the pinned layer and the free layer. A magnetic intermediate layer, and having a property that a resistance value varies according to the magnetization direction of each of the pinned layer and the free layer,
The magnetization directions of the pinned layers of the magnetoresistive effect elements forming a pair are different from each other by 180 °,
The magnetoresistive effect elements forming a pair included in each of the plurality of magnetoelectric conversion units are arranged side by side along the rotation direction of the rotating body and extend from the rotation axis of the rotating body so as to be orthogonal to the rotation direction. It is arranged symmetrically with the line (BL),
A rotation sensor in which a bridge circuit is formed by each of the paired magnetoresistive effect elements, and a midpoint potential of the bridge circuit is a signal based on the rotation state of the rotating body.
The angle around the intersection from the reference line of the reference magnetic flux that passes through the intersection (CP) between the parallel direction in which each of the magnetoresistive elements forming a pair and the reference line passes is a, and the center of the magnetoresistive effect element is Assuming that the angle deviation from the reference magnetic flux in the direction of the transmitted magnetic flux is b and the central value of the resistance value of each of the magnetoresistive effect elements forming a pair is Rc, the midpoint potential of the bridge circuit is sin (a) The rotation sensor according to claim 1, which depends on x cos (b) / (cos (a) x sin (b) -Rc) -1.
The plurality of magnetoelectric converters includes a first magnetoelectric converter along a radial direction in which the magnetization direction of the pinned layer is orthogonal to the rotation axis, and a magnetization direction of the pinned layer orthogonal to a tangential direction of rotation of the rotating body. A second magnetoelectric converter,
A first half bridge circuit is assembled by a pair of magnetoresistive effect elements (11, 12) included in the first magnetoelectric conversion unit, and a pair of magnetoresistive effect included in the second magnetoelectric conversion unit. The rotation sensor according to claim 2, wherein the second half bridge circuit is assembled by the elements (21, 22).
Two first half-bridge circuits are assembled by two pairs of magnetoresistive effect elements (11 to 14) of the first magnetoelectric converter, and the first full-bridge circuit is formed by the two first half-bridge circuits. Is assembled,
Two second half-bridge circuits are assembled by two pairs of magnetoresistive effect elements (21 to 24) of the second magnetoelectric conversion unit, and a second full-bridge circuit is formed by the two second half-bridge circuits. The rotation sensor according to claim 3, wherein
The rotation sensor according to any one of claims 1 to 4, further comprising a processing circuit that detects the midpoint potential of the bridge circuit as the signal based on the rotation state of the rotating body.