JP4582298B2 - Magnetic position detector - Google Patents

Description

  The present invention relates to a magnetic position detection apparatus using a magnetoresistive effect element, and more particularly to a magnetic position detection apparatus suitable for use in a magnetic scale, a rotary encoder, or the like.

  As a conventional magnetic position detection device, as shown in Patent Document 1 below, the magnetoresistive effect element 2 is separated at two or more locations in parallel with the magnetic pole arrangement direction of the magnetic member 1 in which the N pole and the S pole are alternately magnetized. The arrangement is known.

In this case, the arrangement interval of the magnetoresistive element 2 is an interval suitable for the magnetization pitch (magnetic pole arrangement pitch) P of the magnetic member 1 as shown in FIG. That is, when n is an integer with respect to the magnetization pitch = P, the arrangement interval L = nP (1/8) P is optimal. Due to the arrangement of the magnetoresistive effect element 2 described above, the output signal of the magnetic position detecting device is a two-phase sine waveform [sinθ, sin (θ + 90 °) = cosθ] whose phase is shifted by 90 ° as shown in FIG. Thus, the angle θ necessary for obtaining the magnetic information of the magnetic member 1 can be obtained from this signal. As described above, the conventional magnetic position detecting device detects the position of the magnetic member 1 by disposing the magnetoresistive effect element 2 at two or more locations.

  By the way, in the conventional magnetic position detecting device, in order to obtain an optimum signal, the magnetoresistive effect element 2 is arranged with respect to the magnetization pitch P of the magnetic member 1 as shown in FIG. (1/8) P (N is an integer). If the magnetization pitch is changed by changing the magnetic member 1 or the like, the phase of the output signal obtained from each magnetoresistive element is shifted, so that an optimum signal cannot be obtained. For example, in the magnetic member, when the magnetization pitch is changed from P to P × 2 as shown in FIG. 9B, a set of magnetoresistive effect elements having the same characteristics and spaced apart {arrangement interval of magnetoresistive effect elements L = nP When ± (1/8) P} is used, the output signal from each magnetoresistive element is a two-phase sinusoidal waveform [sinθ, sin (θ + 45 °) ≠ cosθ with a phase shift of 45 ° as shown in FIG. It becomes difficult to obtain the angle θ necessary for obtaining magnetic information. Also, even if the materials of the magnetic member and the magnetoresistive effect element that are spaced apart are changed (stretched) due to changes in the external environment and the mutual detection pitch is shifted, the phase of the output signal of the magnetic position detection device is shifted. become.

  In the present invention, in consideration of the above points, by arranging at least one pair of vector detection type magnetoresistive effect elements at the same position with respect to the magnetic pole arrangement direction of the magnetic member, it does not depend on the magnetic pole arrangement pitch of the magnetic member, It is an object of the present invention to provide a magnetic position detection device capable of obtaining an appropriate output signal for a magnetic member having an arbitrary magnetic pole arrangement pitch.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, a magnetic position detection apparatus according to the present invention includes a magnetic member in which N poles and S poles are alternately arranged, and one or more pairs facing the magnetic pole arrangement surface of the magnetic member. And a vector detection type magnetoresistive effect element,
The one or more pairs of vector detection type magnetoresistive effect elements are configured such that the pinned layer magnetization of the vector detection type magnetoresistive effect elements that form a pair and have a magnetosensitive surface substantially parallel to an external magnetic field by the magnetic member. It is characterized in that the directions are shifted from each other by approximately 90 °, and all the vector detection type magnetoresistive elements are arranged at the same position with respect to the magnetic pole arrangement direction of the magnetic member.

  In the magnetic position detection device, at least one of the plurality of pairs of vector detection type magnetoresistive effect elements and the remaining pair may be configured such that the pinned layer magnetization direction is opposite.

  In the magnetic position detection device, the one or more pairs of vector detection type magnetoresistive effect elements may be arranged in a line substantially perpendicular to the magnetic pole arrangement direction of the magnetic member. Alternatively, the one or a plurality of pairs of vector detection type magnetoresistive elements may be arranged so as to be substantially perpendicular to the magnetic pole arrangement direction of the magnetic members and overlap each other. Further, the plurality of pairs of vector detection type magnetoresistive elements may be arranged in a plurality of rows substantially perpendicular to the magnetic pole arrangement direction of the magnetic member, and the rows may be arranged to overlap each other.

  In the magnetic position detection device, the first output signal using one of the vector detection type magnetoresistive effect elements forming a pair and the second output signal using the other are 2 out of phase by 90 °. It may be a sinusoidal waveform of the phase.

  The magnetic pole array surface of the magnetic member may be a flat surface or a curved surface.

  As the vector detection type magnetoresistance effect element, a spin valve type giant magnetoresistance effect element can be used.

  According to the magnetic position detecting device of the present invention, the vector detection type magnetoresistive effect element of one or more pairs is arranged such that the magnetosensitive surface is substantially parallel to the external magnetic field by the magnetic member and makes a pair. The pinned layer magnetization directions of the sensing type magnetoresistive elements are arranged so as to be shifted from each other by approximately 90 °, and all the vector sensing types are located at the same position with respect to the magnetic pole arrangement direction of the N pole and S pole of the magnetic member. Since the magnetoresistive effect element is arranged, an appropriate output signal can be obtained for a magnetic member having an arbitrary magnetic pole arrangement pitch without depending on the magnetic pole arrangement pitch of the magnetic member.

  Even if the magnetic member and the magnetoresistive element are changed (expanded / contracted) due to the influence of the external environment, the output signal is hardly affected, and an optimum output signal can always be obtained.

  Furthermore, since the magnetoresistive effect element is not spaced apart from the magnetic pole arrangement direction of the magnetic member, the sensor surface with respect to the magnetic member is reduced, so that the sense region is widened. Cannot be extended to both ends).

  Hereinafter, as the best mode for carrying out the present invention, an embodiment of a magnetic position detection device will be described with reference to the drawings.

  A first embodiment of a magnetic position detection apparatus according to the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes a magnetic member to be detected in which N poles and S poles are alternately magnetized. A magnetic pole array surface 1a in which N poles and S poles appear alternately is a flat surface, and the magnetic pole array direction is The magnetic poles are linearly arranged in the longitudinal direction of the magnetic member.

  On the other hand, the spin valve type giant magnetoresistive effect elements SV-GMR1 to SV-GMR4 as the two pairs of vector detection type magnetoresistive effect elements are arranged so as to face the magnetic pole array surface 1a of the magnetic member 1. One row is arranged perpendicular to the magnetic pole arrangement direction. As a result, all SV-GMR1 to SV-GMR4 are arranged at the same position with respect to the magnetic pole array direction of the magnetic member 1. In FIG. 1, SV-GMR1 to SV-GMR4 are shown larger than the magnetic member 1 for easy understanding, but in actuality, they are very small. As will be described later with reference to FIG. 4, the magnetic sensitive surfaces of SV-GMR1 to SV-GMR4 are arranged so as to be parallel to the external magnetic field.

  In order to configure the magnetic position detecting device, at least one of the magnetic member 1 and the two pairs of SV-GMR1 to SV-GMR4 is linearly movable in the magnetic pole arrangement direction of the magnetic member 1. That is, both the magnetic member 1 and the two pairs of SV-GMR1 to SV-GMR4 are provided so as to be relatively movable in the magnetic pole arrangement direction.

  Here, the spin-valve giant magnetoresistive element (hereinafter referred to as a spin-valve GMR element) used in FIG. 1 has a strong magnetization direction fixed in one direction as shown in the film configuration of FIG. A magnetic pinned layer, a nonmagnetic layer through which a current mainly flows, and a ferromagnetic free layer whose magnetization direction coincides with the external magnetic field direction (external magnetic flux direction). When the pinned layer magnetization direction and the vector direction of the external magnetic field coincide with each other, the state a (low resistance state) shown in FIG. 4B is obtained, and when the vector direction of the external magnetic field is rotated in the plane of the spin valve GMR element, The resistance value changes depending on the angle formed with the magnetization direction. At an angle of 90 °, the resistance value change due to the external magnetic field is substantially zero in the state b (medium resistance state), and the state c (high resistance state) is obtained in the opposite direction. This characteristic is the in-plane magnetic characteristic of the spin-valve GMR element shown in FIG. 4C, under the condition that there is an external magnetic field parallel to the magnetosensitive surface (plane where the free layer exists) of the spin-valve GMR element. The relationship between the rotation angle and the resistance change rate (ΔR / R) with respect to the pinned layer magnetization direction is shown by rotating the external magnetic field around the rotation center axis perpendicular to the magnetosensitive surface. In this case, the rate of change in resistance (ΔR / R) changes gently in a sinusoidal waveform.

  In the case of FIG. 1, the magnetosensitive surfaces of each of the SV-GMR1 to SV-GMR4 are perpendicular to the magnetic pole array surface 1a and parallel to the external magnetic field by the magnetic member 1, and FIG. 4 (C The resistance change rate (ΔR / R) changes as shown in FIG. The arrows shown in each of the SV-GMR1 to SV-GMR4 indicate the pinned layer magnetization direction, and the pinned layer magnetization direction of one of the SV-GMR1 and SV-GMR2 of the pair SV-GMR1 and SV-GMR2 is in the magnetic pole arrangement direction. The pinned layer magnetization direction of the other SV-GMR2 is perpendicular to the magnetic pole arrangement direction. That is, the pin layer magnetization directions of the SV-GMR1 and SV-GMR2 forming a pair are shifted by 90 ° from each other. Similarly, the pin layer magnetization directions of SV-GMR3 and SV-GMR4 that make a pair are shifted by 90 ° from each other, but the pin layer magnetization direction is opposite to that of the pair of SV-GMR1 and SV-GMR2. .

  FIG. 2 shows a circuit configuration for extracting two-phase output signals Vout1 and Vout2 when two pairs of spin-valve GMR elements SV-GMR1 to SV-GMR4 are arranged. SV-GMR1 and SV-GMR3 are connected in series to the supply voltage Vin, an output signal Vout1 is taken out from the connection point between them, and SV-GMR2 and SV-GMR4 are connected in series to the supply voltage Vin. An output signal Vout2 is extracted from the connection point.

  The operation of Embodiment 1 of the present invention will be described in the case where the magnetization pitch (magnetic pole arrangement pitch) of the magnetic member 1 = P as shown in FIG.

  When SV-GMR1 to SV-GMR4 arranged in one row are located close to and opposite to the center of the north pole of the magnetic member 1 as the detection target, the magnetization directions of the free layers of SV-GMR1 to SV-GMR4 are the magnetic member 1. Turn in the opposite direction. Therefore, the resistance values of SV-GMR1 to SV-GMR4 are SV-GMR1 maximum value, SV-GMR3 minimum value, SV-GMR2 and SV-GMR4 intermediate values.

  When one row of SV-GMR1 to SV-GMR4 is positioned close to and opposite to the center of the S pole of the magnetic member 1, the magnetization directions of the free layers of SV-GMR1 to SV-GMR4 are directed toward the magnetic member 1. . Accordingly, the resistance values of SV-GMR1 to SV-GMR4 are SV-GMR1 minimum value, SV-GMR3 maximum value, SV-GMR2, and SV-GMR4 intermediate values.

  In addition, when the SV-GMR1 to SV-GMR4 arranged in a single row are positioned in close proximity to each other between S and N (boundary between the S pole and the N pole) in the magnetic member 1, the free layers of SV-GMR1 to SV-GMR4 The magnetization direction of S is directed to S ← N. The resistance values of SV-GMR1 to SV-GMR4 are SV-GMR2 maximum value, SV-GMR4 minimum value, SV-GMR1 and SV-GMR3 intermediate values.

  When the SV-GMR1 to SV-GMR4 in a single row are positioned in close proximity to each other between NS on the magnetic member 1 (the boundary between the N pole and the S pole), the magnetization of the free layers of SV-GMR1 to SV-GMR4 The direction is N → S. The resistance values of SV-GMR1 to SV-GMR4 are SV-GMR2 minimum value, SV-GMR4 maximum value, and SV-GMR1 and SV-GMR3 intermediate values.

  Therefore, the output signals Vout1 and Vout2 obtained from the circuit configuration of FIG. 2 are two-phase sine waveform outputs whose phases are shifted from each other by 90 ° as shown in FIG. This corresponds to 0 ° to 360 ° of 3 (A).

  Next, considering the case where the magnetization pitch (magnetic pole arrangement pitch) of the magnetic member 1 = P × 2 as shown in FIG. 1B, SV-GMR1 to SV-GMR4 are arranged in one row, and the magnetic member 1 Since they are at the same position with respect to the magnetic pole arrangement direction, even when SV-GMR1 to SV-GMR4 arranged in one row are located close to and opposed to the center of the N-pole or S-pole of the magnetic member 1, between S-N When the SV-GMR1 to SV-GMR4 arranged in a single row are located in close proximity to each other (boundary between S pole and N pole) or between NS (boundary between N pole and S pole), FIG. The operation is exactly the same, and the output signals Vout1 and Vout2 shown in FIG. 3B are obtained. That is, it is possible to obtain an appropriate output signal for a magnetic member having an arbitrary magnetic pole arrangement pitch, that is, a two-phase sine waveform output that is 90 ° out of phase with each other without depending on the magnetic pole arrangement pitch of the magnetic member 1. I understand.

  According to this embodiment, the following effects can be obtained.

(1) Four spin-valve GMR elements SV-GMR1 to SV-GMR4 are arranged so that the magnetic sensitive surfaces are parallel to the external magnetic field by the magnetic member 1, and the pair of SV-GMR1 and SV-GMR2 The pin layer magnetization directions of the SV-GMR3 and SV-GMR4 pairs are shifted by 90 ° from each other. The other SV-GMR3 and SV-GMR3 and SV-GMR2 pairs are opposite to each other. The pin layer magnetization direction of the pair of -GMR4 is reversed, and four SV-GMR1 to SV-GMR4 are arranged in a line perpendicular to the magnetic pole arrangement direction of the magnetic member 1. As a result, the four SV-GMR1 to SV-GMR4 are located at the same position with respect to the magnetic pole arrangement direction of the magnetic member 1, and the magnetic member has an arbitrary magnetic pole arrangement pitch without depending on the magnetic pole arrangement pitch of the magnetic member 1. In this case, appropriate output signals Vout1 and Vout2 are obtained.

(2) As the magnetic member 1 moves in the direction of the magnetic pole arrangement with respect to SV-GMR1 to SV-GMR4 arranged in a single row under the condition that an external magnetic field parallel to the magnetosensitive surface of the spin valve type GMR element exists. Since the direction of the external magnetic field changes, the in-plane magnetic characteristics of the spin valve type GMR element shown in FIG. 4C are used, and the phases are shifted by 90 ° from each other by using the circuit configuration of FIG. Output signals Vout1 and Vout2 having a sinusoidal waveform are obtained.

(3) Even if the magnetic member 1 is changed (expanded / contracted) due to the influence of the external environment, the output signals Vout1 and Vout2 are hardly affected and an optimum output signal can always be obtained.

(4) Since the SV-GMR1 to SV-GMR4 are not arranged apart from the magnetic pole arrangement direction of the magnetic member 1, the sensor surface with respect to the magnetic member 1 is reduced, and the sense region is expanded. That is, in the conventional separation arrangement, the sense region cannot be extended to both ends of the magnetic member, but in the present embodiment, it can be effectively used up to the end of the magnetic member 1.

  FIG. 5 shows a second embodiment of the present invention, in which each of the spin valve GMR elements SV-GMR1 to SV-GMR4 faces the magnetic pole array surface 1a of the magnetic member 1 and is in the direction of the magnetic pole array of the magnetic member 1. The magnetic members 1 are arranged so as to overlap each other so as to be in the same position with respect to the magnetic pole arrangement direction of the magnetic member 1. The pinned layer magnetization directions of SV-GMR1 to SV-GMR4 are the same as those in the first embodiment.

  Other configurations and operational effects are the same as those of the first embodiment described above, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 shows a third embodiment of the present invention, in which four spin-valve GMR elements SV-GMR1 to SV-GMR4 are arranged in two rows and two tiers so as to face the magnetic pole array surface 1a of the magnetic member 1. It has become. In other words, the pair of spin valve GMR elements SV-GMR1 and SV-GMR2 and the pair of spin valve GMR elements SV-GMR3 and SV-GMR4 form a pair with respect to the magnetic pole arrangement direction of the magnetic member 1. Are arranged so as to be perpendicular to each other and at the same position with respect to the magnetic pole arrangement direction of the magnetic member 1. The pinned layer magnetization directions of SV-GMR1 to SV-GMR4 are the same as those in the first embodiment.

  Other configurations and operational effects are the same as those of the first embodiment described above, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  FIG. 7 shows a fourth embodiment of the present invention, which is an example in which two (one pair) spin valve type GMR elements SV-GMR1, SV-GMR2 are arranged opposite to the magnetic pole array surface 1a of the magnetic member 1. FIG. In this case, SV-GMR1 and SV-GMR2 are arranged in one line perpendicular to the magnetic pole arrangement direction of the magnetic member 1, and the SV-GMR1 and SV-GMR2 are located at the same position with respect to the magnetic pole arrangement direction of the magnetic member 1. positioned. The pinned layer magnetization directions of SV-GMR1 and SV-GMR2 are the same as those in the first embodiment.

  FIG. 8 shows a circuit configuration for extracting two-phase output signals Vout1 and Vout2 when a pair of spin-valve GMR elements SV-GMR1 and SV-GMR2 are arranged as in the fourth embodiment. In this case, resistors R3 and R4 are used in place of SV-GMR3 and SV-GMR4 in the first embodiment. That is, SV-GMR1 and R3 are connected in series to the supply voltage Vin, the output signal Vout1 is taken out from the connection point of both, and SV-GMR2 and R4 are connected in series to the supply voltage Vin. Output signal Vout2. Also in this case, two-phase sinusoidal output signals Vout1 and Vout2 that are 90 ° out of phase with each other are obtained.

  In each of the embodiments, a slight deviation in the parallelism of the magnetosensitive surfaces of the spin valve GMR elements SV-GMR1 to SV-GMR4 with respect to an external magnetic field is practically acceptable, and each of the SV-GMR1 to SV-GMR4 It is sufficient that the magnetosensitive surface is substantially parallel to the external magnetic field. Further, a slight deviation in the orthogonality of the pinned layer magnetization directions in the SV-GMR1 and SV-GMR2 pairs and the SV-GMR3 and SV-GMR4 pairs can be allowed practically, and it is sufficient that they are substantially 90 ° apart from each other. Further, in the first, third, and fourth embodiments, the row of the plurality of spin valve GMR elements is arranged perpendicular to the magnetic pole arrangement direction of the magnetic member 1, but some deviation is practically acceptable and substantially vertical. It only has to be arranged.

  In each embodiment, the magnetic pole array surface 1a of the magnetic member 1 is a flat surface, but the magnetic pole array surface of the magnetic member is a curved surface such as a circumferential surface or a semicircular surface. N poles and S poles may be alternately arranged in the plane direction.

  Furthermore, in the first, second, and third embodiments, two pairs of spin valve GMR elements are used. However, for the purpose of improving detection sensitivity, three or more pairs of spin valve GMR elements may be used.

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a first embodiment of a magnetic position detection apparatus according to the present invention, where (A) is a perspective view when a magnetization pitch of a magnetic member = P, and (B) is a magnetization pitch of the magnetic member = P × 2. It is a perspective view at the time of. In Embodiment 1, it is a circuit diagram for taking out the output signals Vout1 and Vout2 having a two-phase sine waveform whose phases are shifted from each other by 90 °. FIG. 6A is a waveform diagram of the output signals Vout1 and Vout2, where FIG. 5A is a waveform diagram when the magnetization pitch of the magnetic member is P, and FIG. 5B is a waveform diagram when the magnetization pitch of the magnetic member is P × 2. is there. FIG. 4 is a film configuration and magnetic characteristics of a spin valve type GMR element used in an embodiment of the present invention, where (A) is a schematic perspective view of the film configuration, and (B) is a low resistance state, a medium resistance state, and a high resistance state. FIG. 6C is an explanatory diagram showing the relationship between the pinned layer magnetization direction and the free layer magnetization direction, and (C) is an in-plane magnetic characteristic of the spin valve type GMR element (an angle formed by the pinned layer magnetization direction and the free layer magnetization direction and resistance change) It is a wave form diagram which shows a relationship). It is a perspective view which shows Embodiment 2 of this invention. It is a perspective view which shows Embodiment 3 of this invention. It is a perspective view which shows Embodiment 4 of this invention. In Embodiment 4, it is a circuit diagram for taking out the output signals Vout1 and Vout2 having a two-phase sine waveform whose phases are shifted from each other by 90 °. FIG. 2A is a schematic configuration diagram of a related art, and FIG. 3A is a schematic configuration diagram when the magnetization pitch of a magnetic member is P, and FIG. 2B is a schematic configuration diagram when the magnetization pitch of the magnetic member is P × 2. . FIG. 9 is a voltage waveform of a two-phase output signal in the prior art of FIG. 9, where (A) is a waveform diagram when the magnetization pitch of the magnetic member = P, and (B) is a magnetization pitch of the magnetic member = P × 2. It is a wave form chart at the time of.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic member 1a Magnetic pole arrangement surface 2 Magnetoresistive element SV-GMR1-SV-GMR4 Spin valve type GMR element R3, R4 Resistance

Claims (8)

A magnetic position detection device having a magnetic member in which N poles and S poles are alternately arranged, and one or more pairs of vector sensing magnetoresistive elements facing the magnetic pole arrangement surface of the magnetic member,
The one or more pairs of vector detection type magnetoresistive effect elements are configured such that the pinned layer magnetization of the vector detection type magnetoresistive effect elements that form a pair and have a magnetosensitive surface substantially parallel to an external magnetic field by the magnetic member. The magnetic position detecting device is arranged so that the directions are deviated from each other by about 90 °, and all the vector detection type magnetoresistive effect elements are arranged at the same position with respect to the magnetic pole arrangement direction of the magnetic member. .   2. The magnetic position detecting device according to claim 1, wherein at least one pair of the plurality of pairs of vector detection type magnetoresistive elements and the remaining pairs have opposite directions of pinned layer magnetization.   3. The magnetic position detecting device according to claim 1, wherein the one or more pairs of vector detection type magnetoresistive effect elements are arranged in a line substantially perpendicular to the magnetic pole arrangement direction of the magnetic member. .   3. The magnetic type according to claim 1, wherein the one or more pairs of vector detection type magnetoresistive elements are arranged substantially perpendicular to the magnetic pole arrangement direction of the magnetic members and overlap each other. Position detection device.   3. The plurality of pairs of vector-detecting magnetoresistive elements are arranged in a plurality of rows substantially perpendicular to the magnetic pole arrangement direction of the magnetic member, and the rows are arranged to overlap each other. Magnetic position detector.   The first output signal using one of the vector sensing magnetoresistive effect elements forming a pair and the second output signal using the other are two-phase sine waveforms that are 90 ° out of phase with each other. 6. A magnetic position detecting device according to claim 1, 2, 3, 4 or 5.   7. The magnetic position detecting device according to claim 1, wherein the magnetic pole array surface of the magnetic member is a flat surface or a curved surface.   8. The magnetic position detecting device according to claim 1, wherein the vector detection type magnetoresistive effect element is a spin valve type giant magnetoresistive effect element.

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