JP2009133751A - Moving body detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moving body detection device, capable of detecting not only the movement information of a magnetic material moving body, but also the stop position information. <P>SOLUTION: A soft magnetic body gear 1 has at least one projection part or recessed part. SV-GMR elements R1-R4 are fixed and arranged in one row close to the inside of the thickness width W of the soft magnetic body gear 1 or to its periphery. A pin layer magnetization direction of the SV-GMR elements R1, R3 (first set) is in the direction reverse to the direction where the soft magnetic body gear 1 exists, and a pin layer magnetization direction of the SV-GMR elements R2, R4 (second set) is a direction where the soft magnetic body gear 1 exists. The magnetization direction of a bias magnet 5 is substantially vertical to the pin layer magnetization direction of the SV-GMR elements R1-R4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for detecting a change in a magnetic field associated with movement of a magnetic material moving body, and for example, a moving body suitable for use in detecting rotation information of a soft magnetic gear used in industrial machine tools, automobile engines, and the like. The present invention relates to a detection device.

The present applicant has already proposed a moving body detection device using a spin valve type giant magnetoresistive element (hereinafter also referred to as “SV-GMR element”) in Patent Document 1 below. As shown in FIG. 10, the moving body detection apparatus 800 of Patent Document 1 has a resistance value corresponding to a soft magnetic gear 81, a bias magnet 85, and a magnetic field changed by the soft magnetic gear 81. The spin-valve giant magnetoresistive elements R91 to R94, which change, form a bridge circuit with the spin-valve giant magnetoresistive elements R91 to R94, and the pin layer magnetization directions of the paired spin-valve giant magnetoresistive elements are antiparallel. It has become. The soft magnetic gear 81 has a total of eight convex portions 82 on the outer peripheral surface, one at every about 45 ° from the rotation center O.
JP-A-2005-089442

  FIG. 11 is an explanatory diagram of the fundamental configuration and magnetic characteristics of the SV-GMR element. The magnetosensitive surface of the SV-GMR element has a magnetoresistive film that forms a magnetosensitive pattern. The magnetoresistive film is formed by laminating a ferromagnetic pinned layer, a nonmagnetic layer, and a ferromagnetic free layer. The magnetization direction of the pinned layer is fixed regardless of the external magnetic field H, while the magnetization direction of the free layer is changed by the external magnetic field H. The magnetic characteristics of the SV-GMR element are such that the direction of the external magnetic field and the pinned layer magnetization direction are forward parallel and the resistance change rate (ΔR / R) is negative, the direction of the external magnetic field and the pinned layer magnetization direction are antiparallel and the resistance change. The rate (ΔR / R) is positive. That is, the SV-GMR element has a low resistance when the direction of the external magnetic field and the pinned layer magnetization direction are forward parallel, and has a high resistance when the direction of the external magnetic field and the pinned layer magnetization direction are antiparallel.

  In the moving body detection device of Patent Document 1, as shown in an enlarged view in FIG. 10, the pin layer magnetization direction of the SV-GMR elements R91 and R93 is substantially opposite to the rotation direction of the soft magnetic gear 81, and SV The pinned layer magnetization direction of the GMR elements R92 and R94 is substantially forward of the rotational direction of the soft magnetic gear 81.

  When the convex portion of the soft magnetic gear 81 approaches the magnetic sensitive surface of the SV-GMR elements R91 to R94, the convex portion approaches the magnetic material rotation tangential component of the magnetic field at the magnetic sensitive surface position of each SV-GMR element. It faces in the direction of coming (substantially opposite to the rotational direction of the soft magnetic gear 81). At this time, the SV-GMR elements R91 and R93 have a low resistance and the SV-GMR elements R92 and R94 have a high resistance due to the magnetic characteristics described above.

  On the other hand, when the convex portion of the soft magnetic gear 81 moves away from the magnetic sensitive surface of the SV-GMR elements R91 to R94, the magnetic material rotation tangential component of the magnetic field at the position of the magnetic sensitive surface of the SV-GMR element is the direction in which the convex portion moves away. (Generally forward direction of the rotation direction of the soft magnetic gear 81). At this time, the SV-GMR elements R91 and R93 have a high resistance and the SV-GMR elements R92 and R94 have a low resistance due to the magnetic characteristics described above.

  As the soft magnetic gear 81 rotates, the convex portions 82 of the soft magnetic gear 81 sequentially approach and move away from the magnetic sensitive surfaces of the SV-GMR elements R91 to R94, and as the soft magnetic gear 81 rotates. Repeated. For this reason, the magnetic material rotation tangential component of the magnetic field at the position of the magnetic sensitive surface of each SV-GMR element repeats the same change every time the soft magnetic gear 81 rotates about 45 °. Therefore, an output signal Vout that varies with the rotation of the soft magnetic gear 81 is obtained from the SV-GMR elements R91 to R94 that are Wheatstone bridge connected (full bridge connection) as shown in FIG. The output signal Vout is amplified by, for example, a differential amplifier and then converted into a rectangular wave signal by a Schmitt trigger circuit. Based on this rectangular wave signal, rotation information of the soft magnetic gear 81 can be detected.

  Since the moving body detection apparatus of Patent Document 1 uses the SV-GMR element as the magnetic sensing element as described above, the soft magnetic gear and the magnetic sensing element (rotation sensor) are compared with the case where other magnetoresistive elements are used. ), A sufficiently large output signal can be obtained, and sensor design that does not depend on the uneven pitch of the soft magnetic gear is also possible. However, the output signal Vout obtained from the SV-GMR elements R91 to R94 connected to the Wheatstone bridge in the moving object detection apparatus of Patent Document 1 is soft magnetic as shown in FIGS. 6 (A) and 7 (A). Although the convex portion 82 of the body gear 81 swings large and small when approaching and moving away from the SV-GMR elements R91 to R94, the vicinity of the center of the convex portion 82 is on the magnetosensitive surface of the SV-GMR elements R91 to R94. Sometimes it becomes zero. Here, the output signal Vout is zero even when the convex portion 82 and the portion other than the vicinity of the edge (between the convex portion and the convex portion) are on the magnetosensitive surface of the SV-GMR elements R91 to R94. In the moving body detection device of Document 1, stop position information (particularly, stop position information when the power is turned on) cannot be detected even if rotation information of the soft magnetic gear 81 can be detected. This problem is the same when a linear moving body such as a rack is to be detected.

  The present invention has been made in view of such a situation, and an object of the present invention is to detect not only movement information of a magnetic material moving body but also stop position information using a magnetic field vector detection type SV-GMR element. Is to provide a simple moving body detection apparatus.

One embodiment of the present invention is a moving object detection apparatus. This device
A magnetic material moving body having at least one convex portion or concave portion, a bias magnetic field generating means, and a spin valve type giant magnetoresistive element fixedly arranged with respect to the bias magnetic field generating means,
The pinned layer magnetization direction of the spin-valve giant magnetoresistive element is the direction in which the magnetic material moving body is present or the opposite direction.
The bias magnetic field generating means generates a magnetic field on the magnetosensitive surface of the spin valve giant magnetoresistive element according to a positional relationship between the spin valve giant magnetoresistive element and the convex portion or the concave portion of the magnetic material moving body. The pinned layer magnetization direction component is arranged to change.

  In the moving body detection device of a certain aspect, the pinned layer magnetization direction may be substantially perpendicular to a formation surface of the convex portion or the concave portion of the magnetic material moving body.

  In the mobile object detection device of a certain aspect, the spin valve giant magnetoresistive element may be present within or near the thickness width of the magnetic material mobile object.

  In the mobile object detection device of a certain aspect, the magnetization direction of the bias magnetic field generation means may be substantially perpendicular to the pinned layer magnetization direction of the spin valve giant magnetoresistive element.

  In this case, the two bias magnetic field generating means may be disposed opposite to each other with the same polarity, and the spin valve giant magnetoresistive element may be fixedly disposed between the opposing surfaces of the two bias magnetic field generating means.

  In a mobile object detection device according to an aspect, the spin valve giant magnetoresistive elements adjacent to each other whose pinned layer magnetization directions are antiparallel to each other may form a bridge circuit.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, output signals having different magnitudes can be obtained according to the positional relationship between the spin valve type giant magnetoresistive element and the convex portion or concave portion of the magnetic material moving body. It is also possible to detect stop position information.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

(First embodiment)
FIG. 1 is an exemplary schematic perspective view of a moving body detection apparatus 100 according to the first embodiment of the present invention. The moving body detection apparatus 100 includes a soft magnetic gear 1 as a magnetic material moving body, a bias magnet 5 as a bias magnetic field generating means, and SV-GMR elements R1 to R4. Note that the bias magnet 5 and the SV-GMR elements R1 to R4 are shown larger than actual in relation to the soft magnetic gear 1.

  The plate-like or columnar soft magnetic gear 1 has at least one convex portion or concave portion (for example, has convex portions 2 with a constant arrangement pitch P), and is attached to a rotating shaft (not shown). In FIG. 1, as an example, the soft magnetic gear 1 has a total of eight convex portions 2 on the outer peripheral surface, one at about 45 ° in angle from the rotation center O.

  The SV-GMR elements R1 to R4 forming a bridge circuit (Wheatstone bridge) are present in the vicinity of one row in the thickness width W of the soft magnetic gear 1 or in the vicinity thereof (or are fixedly arranged), and the pin layer magnetization direction Is substantially perpendicular to the outer peripheral surface of the soft magnetic gear 1 (that is, the surface on which the convex portion 2 is formed). Here, the pin layer magnetization direction of the SV-GMR elements R1 and R3 (first set) is opposite to the direction in which the soft magnetic gear 1 exists, and the pin of the SV-GMR elements R2 and R4 (second set). The layer magnetization direction is the direction in which the soft magnetic gear 1 exists. In addition, the arrangement interval of the SV-GMR elements is negligibly small with respect to the width of the convex portion (or concave portion) of the soft magnetic gear 1.

  The bias magnet 5 changes the pin layer magnetization direction component of the magnetic field on the magnetosensitive surface of the SV-GMR elements R1 to R4 according to the positional relationship between the SV-GMR elements R1 to R4 and the convex portion 2 of the soft magnetic gear 1. It is arrangement to do. The magnetization direction of the bias magnet 5 is preferably substantially perpendicular to the pinned layer magnetization direction of the SV-GMR elements R1 to R4. In the case of FIG. 1, the bias magnet 5 is magnetized in the direction of the rotational axis of the soft magnetic gear 1, and the N pole surface of the bias magnet 5 and the magnetic sensitive surfaces (pinned layer magnetization direction) of the SV-GMR elements R1 to R4. It is almost parallel. In such an arrangement, since the magnetic field generated by the bias magnet 5 is attracted to the soft magnetic gear 1, the resistance change ΔR of the SV-GMR elements R1 and R3 is compared with that in the absence of a magnetic field based on the magnetic characteristics shown in FIG. Thus, the resistance change ΔR of the SV-GMR elements R2 and R4 is negative as compared with the case of no magnetic field.

  FIG. 2 is an explanatory diagram of a magnetic field when the moving body detection device 100 shown in FIG. 1 is viewed from the upper side. FIG. 2A shows a portion other than the convex portion 2 of the soft magnetic gear 1 in the SV-GMR element R1. To (B) when the convex portion 2 of the soft magnetic gear 1 is present in front of the SV-GMR elements R1 to R4 (hereinafter referred to as “when the convex portion is not opposed”). Hereinafter, “when the convex portion is opposed”) is shown. 3A and 3B are explanatory diagrams of the magnetic field when the moving body detection device 100 shown in FIG. 1 is viewed from the side. FIG. 3A shows a case where the convex portion is not opposed, and FIG. Show. As shown in these figures, the component (the pinned layer magnetization direction component or the component in the opposite direction) of the magnetic field at the magnetic sensing points of the SV-GMR elements R1 to R4 in the direction of the magnetic field is not opposed to the convex portion. The time is small, and the time is large when the convex part is opposed. For this reason, the SV-GMR elements R1 and R3 have a higher resistance when the convex portions are opposed than when the convex portions are not opposed (the amount of increase in resistance from when no magnetic field is greater), and the SV-GMR elements R2 and R3 R4 is further reduced in resistance (a further decrease in resistance from the absence of a magnetic field). Accordingly, the output signal Vout from the SV-GMR elements R1 to R4 connected to the Wheatstone bridge has different magnitudes when the convex portion is opposed and when the convex portion is not opposed. Hereinafter, this will be described with reference to FIGS.

  FIG. 4 is a waveform explanatory diagram of an output signal from the Wheatstone bridge of FIG. In the figure, V1 indicates the voltage at the connection point of the SV-GMR elements R1 and R2, and V2 indicates the voltage at the connection point of the SV-GMR elements R3 and R4. The detection signal Vdet is obtained by inverting and amplifying Vout (= V2−V1) with a differential amplifier (not shown). As shown in the figure, the detection signal Vdet is large when the convex portion is not opposed, and is small when the convex portion is opposed. For reference, actually measured analog waveforms of V1 and V2 are shown in FIG.

  FIG. 6A is a Vout waveform diagram when an arbitrary convex portion of the soft magnetic gear passes in front of the SV-GMR element in the moving body detection apparatus (FIG. 10) of Patent Document 1. FIG. 5B is a Vout waveform diagram when an arbitrary convex portion of the soft magnetic gear passes in front of the SV-GMR element in the moving body detection apparatus of the present embodiment shown in FIG. FIG. 7A is a Vout waveform diagram when the soft magnetic gear (three convex portions on the outer peripheral surface) makes one turn in the moving body detection device (FIG. 10) of Patent Document 1. FIG. 5B is a Vout waveform diagram when the soft magnetic gear (three convex portions on the outer peripheral surface) makes one turn in the moving body detection device of the present embodiment shown in FIG.

  As is clear from these figures, in the moving body detection device of Patent Document 1, as described above, the Vout swings large and small when the convex portion approaches and moves away from the SV-GMR element. Is passing in front of the SV-GMR element, Vout becomes zero. On the other hand, in the moving body detection device of the present embodiment, when the convex portion passes in front of the SV-GMR element (when the convex portion is opposed), it is more comprehensive than when it is not (when the convex portion is not opposed). Vout is large, especially when the center of the convex portion passes in front of the SV-GMR element.

  As described above, in the moving body detection device of Patent Document 1, the output signal Vout is also output when the convex portion and the portion other than the vicinity of the edge (between the convex portion and the convex portion) are on the magnetically sensitive surface of the SV-GMR element. Since it is zero, when the power is turned on, it is impossible to distinguish between the case where there is a convex portion in front of the SV-GMR element and the case where it is not. On the other hand, according to the moving body detection device of the present embodiment, when the convex portion passes in front of the SV-GMR element (when the convex portion is opposed), when it is not (when the convex portion is not opposed). Since Vout is large as a whole, the above disadvantages are eliminated.

  According to the present embodiment, the following effects can be achieved.

(1) In the moving body detection device of Patent Document 1, when the power is turned on, there is no distinction between the case where there is a convex part in front of the SV-GMR element and the case where it is not so, the stop position information of the soft magnetic gear when the power is turned on However, according to the moving body detecting device of the present embodiment, when the convex portion is opposed, an overall larger output signal Vout is obtained than when the convex portion is not opposed. It becomes possible to detect the stop position information.

(2) Since the SV-GMR element is used as the magnetoresistive element, it is possible to perform magnetic detection with higher sensitivity than in the case of using other magnetoresistive elements. For this reason, the freedom degree of arrangement | positioning of an SV-GMR element is high, and the design flexibility is improved.

(3) Since the spin-valve giant magnetoresistive elements adjacent to each other whose pinned layer magnetization directions are antiparallel to each other form a Wheatstone bridge, highly sensitive magnetic detection is possible. In addition, the influence of the temperature characteristics of the SV-GMR element is reduced.

(Second Embodiment)
FIG. 8 is an exemplary schematic perspective view of a moving object detection apparatus 200 according to the second embodiment of the present invention. In the moving body detection apparatus 200 of the present embodiment, two bias magnets 5A and 5B arranged opposite to each other with the same polarity are used as bias magnetic field generating means, and the SV-GMR elements R1 to R4 are disposed between opposing surfaces of the bias magnets 5A and 5B ( 8 is different from the moving body detection apparatus 100 according to the first embodiment shown in FIG. 1 in that the fixed arrangement is made between the N pole faces), and the other points are the same.

  According to the second embodiment, since the two bias magnets 5A and 5B arranged to face each other with the same polarity are used as the bias magnetic field generating means, the detection sensitivity can be further increased as compared with the first embodiment.

  The present invention has been described above by taking the embodiment as an example. However, it will be understood by those skilled in the art that various modifications can be made to each component of the embodiment within the scope of the claims. Hereinafter, modifications will be described.

  In the embodiment, the SV-GMR element is fixedly disposed within or near the thickness width of the soft magnetic gear, but in the modification, the SV-GMR element is close to the edge of the soft magnetic gear end face instead. Thus, it may exist on the soft magnetic gear end face side (or may be fixedly arranged). In this case, it is preferable that the SV-GMR element is located within the height range of the convex portion of the soft magnetic gear, or the vicinity thereof, as shown in FIG. 9, and the pin layer magnetization direction of the SV-GMR element is the soft magnetic material. It may be substantially perpendicular to the gear end face. The magnetizing direction of the bias magnet 5 is preferably directed to the rotation axis of the soft magnetic gear 1. Also according to this modification, the same effects as in the embodiment can be obtained.

  In the embodiment, the SV-GMR element is connected to the Wheatstone bridge, but the connection form of the SV-GMR element is not limited to this, and may be a half-bridge connection. Although Wheatstone bridge connection is superior in terms of magnetic detection sensitivity and temperature characteristics, in the case of half bridge connection, the number of components can be reduced because only two SV-GMR elements are required. Further, it is possible to form a half bridge with the SV-GMR element and a fixed resistor. In this case, although the magnetic detection sensitivity is lower than that in the case where the half bridge is formed by two SV-GMR elements, the cost can be reduced. This also applies to the Wheatstone bridge connection. Instead of forming a Wheatstone bridge with four SV-GMR elements, a Wheatstone bridge may be formed with two SV-GMR elements and two fixed resistors.

  In the embodiment, the soft magnetic gear is shown as an example of the magnetic material moving body. However, the present invention is not limited to this. For example, a soft magnetic rack (straight moving body) in which irregularities are linearly arranged can be used as the magnetic material moving body. Good.

  In the embodiment, the bias magnetic field generating means is a permanent magnet. However, an electromagnet can be used on the principle of operation.

1 is an exemplary schematic perspective view of a mobile object detection device according to a first exemplary embodiment of the present invention. It is explanatory drawing of the magnetic field at the time of seeing the mobile body detection apparatus 100 shown by FIG. 1 from the upper side, (A) is a part other than the convex part 2 of the soft magnetic gear 1 before SV-GMR elements R1-R4. (B) shows when the convex portion 2 of the soft magnetic gear 1 is present in front of the SV-GMR elements R1 to R4 (hereinafter referred to as “convex”). "When facing part"). It is explanatory drawing of the magnetic field at the time of seeing the mobile body detection apparatus 100 shown by FIG. 1 from the side, (A) shows the time of convex part non-opposing, (B) shows the time of convex part opposing. FIG. 2 is a waveform explanatory diagram of an output signal from the Wheatstone bridge in FIG. 1. In the figure, V1 indicates the voltage at the connection point of the SV-GMR elements R1 and R2, and V2 indicates the voltage at the connection point of the SV-GMR elements R3 and R4. FIG. 2 is a measured analog waveform diagram of V1 and V2 in the moving object detection apparatus 100 shown in FIG. (A) is a Vout waveform diagram when an arbitrary convex portion of the soft magnetic gear passes in front of the SV-GMR element in the moving body detection device (FIG. 10) of Patent Document 1. FIG. (B) is a Vout waveform diagram when an arbitrary convex portion of the soft magnetic gear passes in front of the SV-GMR element in the moving body detection device of the present embodiment shown in FIG. (A) is a Vout waveform diagram when the soft magnetic gear (three convex portions on the outer peripheral surface) makes one turn in the moving body detection apparatus (FIG. 10) of Patent Document 1. FIG. (B) is a Vout waveform diagram when the soft magnetic gear (three convex portions on the outer peripheral surface) makes one turn in the moving body detection device of the present embodiment shown in FIG. 1. It is an exemplary schematic perspective view of the moving body detection apparatus which concerns on the 2nd Embodiment of this invention. It is an exemplary schematic perspective view of the moving body detection apparatus which concerns on a modification. It is a schematic perspective view of the moving body detection apparatus of patent document 1. It is explanatory drawing of the fundamental structure and magnetic characteristic of a SV-GMR element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soft magnetic gear 2 Convex part 5 Bias magnet 100 Moving body detection apparatus R1-R4 SV-GMR element

Claims (6)

A magnetic material moving body having at least one convex portion or concave portion, a bias magnetic field generating means, and a spin valve type giant magnetoresistive element fixedly arranged with respect to the bias magnetic field generating means,
The pinned layer magnetization direction of the spin-valve giant magnetoresistive element is the direction in which the magnetic material moving body exists or the opposite direction.
The bias magnetic field generating means generates a magnetic field on the magnetosensitive surface of the spin valve giant magnetoresistive element according to a positional relationship between the spin valve giant magnetoresistive element and the convex portion or the concave portion of the magnetic material moving body. A moving body detection apparatus, wherein the pin layer magnetization direction component changes.   The moving body detection apparatus according to claim 1, wherein the pinned layer magnetization direction is substantially perpendicular to a surface of the magnetic material moving body on which the convex portion or the concave portion is formed.   3. The moving body detection apparatus according to claim 1, wherein the spin-valve giant magnetoresistive element is present within or near a thickness width of the magnetic material moving body. 4.   4. The moving body detection device according to claim 1, wherein a magnetization direction of the bias magnetic field generation unit is substantially perpendicular to a pinned layer magnetization direction of the spin valve giant magnetoresistive element. , Mobile object detection device.   5. The moving body detection apparatus according to claim 4, wherein the two bias magnetic field generating means are disposed opposite to each other with the same polarity, and the spin valve giant magnetoresistive element is fixedly disposed between the opposing surfaces of the two bias magnetic field generating means. The moving body detection device.   6. The moving object detection device according to claim 1, wherein the spin valve giant magnetoresistive elements adjacent to each other whose pinned layer magnetization directions are antiparallel to each other form a bridge circuit. apparatus.

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