JP4281913B2 - Moving body detection device - Google Patents

Description

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

  2. Description of the Related Art Conventionally, as a rotation sensor for detecting the rotation of a magnetic material moving body (a magnetized detection body) such as a soft magnetic gear, a sensor in which a magnetosensitive element is arranged in two regions facing the magnetic material moving body is known. ing. The arrangement interval of the magnetic sensing elements is an interval suitable for the concave / convex pitch of the magnetic material moving body (the magnetic sensor arrangement interval L = P / 2 is optimum for the convex / convex pitch = P of the gear). ing). And if the said magnetic material moving body rotates, the signal corresponding to the unevenness | corrugation will be output.

  In particular, when a magnetoresistive element is used as the magnetosensitive element, the above-mentioned two regions each include two magnetoresistive elements, and a configuration in which a total of four magnetoresistive elements are assembled in a Wheatstone bridge circuit is described in the following patent document. 1 is proposed.

JP-A-9-329462

  In Patent Document 1, when a convex portion of a gear is provided in one magnetic sensitive region, a concave portion of the gear is provided in the other magnetic sensitive region, so that the magnetoresistive element output has a reverse polarity. By taking these differences, an output four times that of one element is obtained by assembling it into a Wheatstone bridge circuit.

  Incidentally, the magnetoresistive element used in the conventional rotation sensor is a magnetic field strength dependent type, and has a characteristic that the resistance value becomes maximum when the external magnetic field is 0, and the resistance value decreases as the external magnetic field increases. FIG. 6A schematically shows the arrangement of the magnetic sensing element, the bias magnet, and the soft magnetic gear in the case of the prior art in which the magnetic field strength-dependent magnetic sensing elements are spaced apart in two regions. The arrangement interval of the region is L, and the convex / concave pitch of the gear is P. Two magnetoresistive elements are arranged in each magnetosensitive element region.

  6B and 6C show signal output and differential output from each element in the case of the optimum element arrangement in the prior art (L = P / 2) (a Wheatstone bridge circuit is composed of a total of four magnetosensitive elements). As shown in FIG. 5B, the signal output phases of the elements in the two regions are shifted by 180 °, so that the differential output in FIG.

  6 (D) and 6 (E) are for explaining the problems of the prior art (when deviating from the optimum element arrangement), and the signal output and differential from each element when L> P / 2. This is an output, and the difference in the signal output phase of the elements in the two regions is reduced as shown in FIG. 4D, so that the differential output in FIG.

  As described with reference to FIG. 6, since the magnetosensitive element used in the conventional rotation sensor is a magnetic field strength-dependent type, in order to obtain an optimal output change, there are two regions with respect to the convex / convex pitch (= P) of the gear. Need to be arranged at an interval of L = P / 2, and when the convex / convex pitch (= P) of the gear and the interval L of the two regions have a relationship of L> P / 2, the phase shift of the output signal of the two regions is small. Therefore, there is a problem that the optimum differential signal output from the Wheatstone bridge circuit cannot be obtained (the amplitude of the differential output is reduced).

  In view of the above, the present invention uses at least one pair of magnetic field vector detection type spin valve giant magnetoresistive elements as the magnetosensitive element, and the pin layer magnetization direction of the paired spin valve giant magnetoresistive elements is Provided is a moving body detection device in which the detection output does not depend on the concave / convex pitch of the magnetic material moving body by disposing the magnetic material moving bodies so as to face substantially forward and substantially opposite directions with respect to the moving direction of the magnetic material moving body. For the purpose.

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

In order to achieve the above object, the invention of claim 1 of the present application
A magnetic material moving body having at least one convex portion or concave portion;
A bias magnet that generates a magnetic field, wherein the magnetic material moving body and the magnetic pole surface face each other, and the magnetic pole surface faces or does not face the convex portion or the concave portion as the magnetic material moving body moves. ,
Connected to form a bridge circuit, a moving object detecting apparatus having at least a pair of spin-valve giant magnetoresistive element located between the pole faces of the magnetic material moving member and the biasing magnet,
The spin-valve giant magnetoresistive elements forming a pair are arranged such that the pinned layer magnetization directions are substantially in the forward and reverse directions with respect to the moving direction of the magnetic material moving body.

According to a second aspect of the present invention, there is provided a moving body detection apparatus according to the first aspect, wherein the pair of spin valve type giant magnetoresistive elements are arranged in a moving direction of the magnetic material moving body and a height direction of the convex portion or the concave portion. It is characterized in that it has arranged in direction substantially perpendicular to the.

Moving object detection apparatus according to the invention of claim 3 is Oite to claim 1, the spin-valve giant magnetoresistive element pairs, overlapping the gap direction between the bias magnet and the magnetic member moving body It is characterized by the arrangement .

According to a fourth aspect of the present invention, there is provided a mobile object detection device according to the third aspect, wherein there are two pairs of the spin valve type giant magnetoresistive elements arranged in the gap direction, and two pairs of the spin valve type are provided. The giant magnetoresistive elements are arranged side by side in a direction substantially perpendicular to the moving direction of the magnetic material moving body and the height direction of the convex portion or the concave portion.
According to a fifth aspect of the present invention, there is provided the moving body detection device according to any one of the first to fourth aspects , wherein the paired spin-valve giant magnetoresistive elements comprise two meander patterns parallel to each other as magnetoresistive patterns. It is characterized by having a double meander pattern .

  According to the moving body detection apparatus of the present invention, a spin valve type giant magnetoresistive element (hereinafter referred to as an SV-GMR element) is used as a magnetosensitive element, and a bias magnet for applying a bias magnetic field is used for this. By arranging the pin layer magnetization directions of the SV-GMR elements so as to face the forward direction and the reverse direction with respect to the movement direction of the magnetic material moving body, the detection output becomes the uneven pitch of the magnetic material moving body. It can be made independent.

  Further, since the SV-GMR element is not a magnetic field strength-dependent magnetosensitive element, the detection output can be made independent of the gap change between the magnetic material moving body and the SV-GMR element.

  As a result, the degree of freedom of design in the counterpart device to which the moving body detection device is attached is increased, and the strict management of the SV-GMR element and the bias magnet attachment position is not required. Variation can be reduced.

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

  FIG. 1 shows a first embodiment of a moving body detection apparatus according to the present invention, in which a rotation sensor for detecting rotation of a soft magnetic gear is configured as a magnetic material moving body.

  In FIG. 1A, reference numeral 1 denotes a soft magnetic gear, which has irregularities on the outer peripheral surface (for example, has convex portions 2 with a constant arrangement pitch P).

  Further, four SV-GMR elements R1, R2, R3, R4 are fixedly arranged so as to face the outer peripheral surface of the soft magnetic gear 1, and a bias magnet 5 for applying a bias magnetic field is fixedly arranged behind them. Has been. In this case, the four SV-GMR elements R1, R2, R3 and R4 are linearly arranged in the thickness direction of the gear 1 in a direction substantially perpendicular to the moving direction (rotating direction) of the soft magnetic gear 1. .

  In the present embodiment, an SV-GMR element is used as a GMR element whose resistance value changes in response to a magnetic field changed by the soft magnetic gear 1 that is a magnetic material moving body, and its typical film configuration The magnetic properties are shown in FIG. The SV-GMR element has a ferromagnetic pinned layer whose magnetization direction is fixed in one direction, and a ferromagnetic free layer stacked on the pinned layer via a nonmagnetic material through which a current mainly flows. The magnetization direction of the pinned layer is not changed by an external magnetic field (external magnetic flux), and the free layer is magnetized in the direction of the external magnetic field (external magnetic flux). Here, when the magnetization direction of the pinned layer is perpendicular to the magnetization direction of the free layer (that is, the direction of the external magnetic field) (when θ = 0 in FIG. 2A), the rate of change in resistance (ΔR / R) Is 0. When the magnetization direction of the pinned layer and the magnetization direction of the free layer (that is, the direction of the external magnetic field H) are parallel but opposite to each other, that is, when they are antiparallel, the rate of change in resistance becomes positive, as shown in FIG. High resistance state. When the magnetization direction of the pinned layer and the magnetization direction of the free layer (that is, the direction of the external magnetic field H) are parallel and in the same direction, that is, in the forward parallel direction, the rate of change in resistance becomes negative, as shown in FIG. It becomes a low resistance state.

  The four SV-GMR elements R1, R2, R3, R4 having magnetic characteristics as shown in FIG. 2 have magnetosensitive surfaces each having one meander pattern as magnetoresistive patterns serving as magnetosensitive patterns. The magnetic surface is preferably in the same plane parallel to the plane in contact with the outer peripheral surface of the soft magnetic gear 1, and R1 of the pair of SV-GMR elements R1 and R2 has the magnetization direction of the pinned layer in the gear rotation direction. R2 is a substantially forward direction. Similarly, among the other pair of SV-GMR elements R3 and R4, R3 has a magnetization direction of the pinned layer substantially opposite to the gear rotation direction, and R4 has a substantially forward direction.

  The bias magnet 5 in FIG. 1A is a permanent magnet having, for example, an N pole on the surface facing the outer peripheral surface of the soft magnetic gear 1 and an S pole on the opposite surface, and the N pole surface and the soft magnetic gear 1. In this relationship, four SV-GMR elements R1, R2, R3, and R4 are positioned between them. Also, it has a sufficient lateral width larger than the arrangement width W1 of the four SV-GMR elements so that a substantially uniform magnetic field can be applied to each of the linearly arranged SV-GMR elements R1, R2, R3, R4. Is desirable. Similarly, the thickness W2 of the gear 1 is desirably equal to or greater than W1.

  As shown in FIG. 1B, a pair of SV-GMR elements R1 and R2 and another pair of SV-GMR elements R3 and R4 constitute a Wheatstone bridge circuit. The supply voltage Vin is supplied. The detection output Vout is obtained as a potential difference between the connection points of R1 and R2 and the connection points of R3 and R4.

  FIG. 3A shows the direction of the external magnetic field (the magnetic flux) when the convex portion 2 of the gear 1 approaches the magnetic sensing point in front of the bias magnet 5 (which may be considered as the arrangement region of the SV-GMR elements R1 to R4). (B) shows the direction of the external magnetic field (direction of magnetic flux) when the convex portion 2 of the gear 1 moves away from the magnetic sensing point.

  Therefore, when the convex portion 2 of the soft magnetic gear 1 to be detected approaches the magnetic sensitive surface of the SV-GMR elements R1, R2, R3, R4 in the arrangement as shown in FIG. 1A, each SV-GMR The gear rotation tangential component of the magnetic flux vector at the position of the magnetosensitive surface of the element faces the direction in which the convex portion 2 approaches. As shown in FIG. 2, 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 in parallel, 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 rate (ΔR / R) is positive. Therefore, when the magnetic flux vector component is directed toward the convex approaching direction, two pairs of SV-GMR elements (the pair of R1 and R2, and the pair of R3 and R4) In one SV-GMR element R1, R3, the resistance value is small (when the pin layer magnetization direction and the gear tangential direction component of the magnetic flux vector direction are forward parallel), and in the other SV-GMR element R2, R4, the resistance value is small. The value becomes large (when the pin layer magnetization direction and the magnetic flux vector direction are anti-parallel to the gear tangential component).

  Further, when the convex part 2 moves away from the magnetic sensitive surfaces of the SV-GMR elements R1, R2, R3, R4, the gear rotation tangential direction component of the magnetic flux vector at the magnetic sensitive surface position of the SV-GMR element is the direction in which the convex part 2 moves away. Facing. When the magnetic flux vector component is directed away from the convex portion, the resistance value is large in one of the SV-GMR elements R1 and R3 (when the pin layer magnetization direction and the gear tangential component of the magnetic flux vector direction are antiparallel), In the other SV-GMR elements R2 and R4, the resistance value is small (when the pinned layer magnetization direction and the gear tangential direction component of the magnetic flux vector direction are forward parallel).

  As described above, when the convex portion 2 of the soft magnetic gear 1 approaches or moves away from each other, in each pair of the two pairs of SV-GMR elements, one resistance value is minimum and the other is maximum. By assembling the Wheatstone bridge circuit of (B), it becomes possible to obtain a detection output Vout that is four times that of one SV-GMR element. Since the detection output Vout changes from a high level to a low level each time the convex portion 2 of the soft magnetic gear 1 passes, the rotation of the soft magnetic gear 1 can be detected.

  In addition, as can be seen from the magnetic characteristics of FIG. 2, the SV-GMR element has a constant positive resistance value or a negative constant value when the external magnetic field is equal to or greater than a predetermined value. , But no longer depends on the strength of the external magnetic field. For this reason, even if the gap between the gear projection and the GMR element magnetosensitive surface changes, the detected output voltage from the Wheatstone bridge in FIG. 1B does not change.

  6A, if the relationship between the arrangement interval L of the magnetosensitive element regions and the convex / convex pitch P of the gear is inappropriate as shown in FIG. 7A (2L> In the case of the present embodiment, the differential output decreases. However, in the case of the present embodiment, as shown in FIG. 7B, even if the convex / convex pitch P of the gear is changed, the Wheatstone in FIG. The detected output voltage (peak value) from the bridge does not change.

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

(1) In a conventional rotation sensor in which magnetic field strength-dependent magnetosensitive elements are arranged in two regions, the detection output voltage must be adjusted if the arrangement pitch of the plurality of magnetosensitive elements is not appropriate with respect to the convex pitch of the soft magnetic gear. However, in the present embodiment, two pairs of SV-GMR elements (R1, R2 pair and R3, R4 pair) are combined into one region as viewed from the rotation direction of the gear 1 in this embodiment. The pin layer magnetization directions of the SV-GMR elements that are paired (arranged in the thickness direction substantially perpendicular to the gear rotation direction) are substantially forward and substantially opposite to the gear rotation direction. Since it is set, the detection output voltage (peak value) of the Wheatstone bridge in which these two pairs of SV-GMR elements are combined is not affected by the gear convex / convex pitch P {FIG. 7B}.

(2) In the conventional rotation sensor using the magnetic field strength-dependent magnetosensitive element, when the gap between the soft magnetic gear and the magnetosensitive element magnetosensitive surface increases, the amount of change in resistance decreases, and the resistance from the Wheatstone bridge decreases. Although the detection output voltage also decreases, in this embodiment, the Wheatstone bridge is configured by combining two pairs of magnetic field vector detection type SV-GMR elements so that the detection output voltage does not depend on the gap.

(3) Due to the effects of (1) and (2), the degree of freedom in designing the device side to which the rotation sensor is attached is increased, and fine position adjustment is possible when the SV-GMR elements R1 to R4 and the bias magnet 5 are assembled. It is no longer necessary (strict management of the mounting position is not required), and variations in the detection output voltage for each product can be reduced.

(4) To obtain an output voltage four times that of one SV-GMR element by forming a Wheatstone bridge using four (two pairs) SV-GMR elements R1 to R4 and extracting the rotation detection output And detection sensitivity can be improved.

  FIG. 4 shows a second embodiment of the present invention. Instead of using four (two pairs) SV-GMR elements, a double meander pattern (two meander patterns) is used as a magnetoresistive pattern serving as a magnetosensitive pattern. Are used, and two SV-GMR elements R13 and R24 are used. The SV-GMR element R13 is a single element composed of R1 and R3 having the same pinned layer magnetization direction, and the SV-GMR element R24 is a single element composed of R2 and R4 having the same pinned layer magnetization direction. is there. The arrangement of the SV-GMR element and the arrangement of the bias magnet 5 with respect to the soft magnetic gear is the same as in the first embodiment.

  In the case of the second embodiment, a Wheatstone bridge can be configured by combining two SV-GMR elements having a double meander pattern on the magnetic sensitive surface, and further miniaturization can be achieved. Further, since the linear arrangement length W3 of the two SV-GMR elements can be shortened, the thickness of the gear can be reduced.

  In the first embodiment, two pairs of SV-GMR elements (the pair of R1 and R2 and the pair of R3 and R4) are perpendicular to the rotation direction of the soft magnetic gear serving as the magnetic material moving body and linear in the thickness direction. However, as in the third embodiment of FIG. 5, the paired SV-GMR elements R1 and R2 are arranged in the gap direction between the soft magnetic gear and the bias magnet 5, and the same The SV-GMR elements R3 and R4 that make a pair may be arranged so as to overlap in the gap direction between the soft magnetic gear and the bias magnet 5. The laminate of SV-GMR elements R1 and R2 and the laminate of SV-GMR elements R3 and R4 are arranged linearly in the thickness direction perpendicular to the rotation direction of the soft magnetic gear. Other configurations are the same as those of the first embodiment.

  In the case of the third embodiment, since the paired SV-GMR elements are arranged to overlap each other, the length of the linear arrangement of the SV-GMR elements in the thickness direction of the soft magnetic gear can be shortened. The thickness can be reduced.

  In Embodiment 3 of FIG. 5, among the four SV-GMR elements R1 to R4, the paired SV-GMR elements are stacked, but all four SV-GMR elements are soft. The magnetic gear and the bias magnet may be arranged so as to overlap each other in the gap direction. Also in this case, four SV-GMR elements are arranged in a direction substantially perpendicular to the rotation direction of the gear.

  Moreover, although the case where the convex part of the rotating soft-magnetic-material gear was periodically arrange | positioned as a magnetic material moving body was shown in said Embodiment 1,2,3, the soft magnetic which a convex part or a recessed part rotates One or more magnetic material moving bodies provided on the outer peripheral surface of the body disk can be used.

  Furthermore, the magnetic material moving body has a configuration in which one or a plurality of convex portions or concave portions are provided on a soft magnetic linear moving body, and is arranged in a direction substantially perpendicular to the moving direction of the magnetic material moving body. The linear movement of the linear moving body may be detected by at least one pair of SV-GMR elements.

  A pair of SV-GMR elements R1 and R2 may be used, and a Wheatstone bridge may be configured using a fixed resistor instead of the other SV-GMR elements R3 and R4. In this case, it is possible to obtain twice the detection output as compared with the case where one SV-GMR element is 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 It is Embodiment 1 of the mobile body detection apparatus which concerns on this invention, Comprising: (A) is a typical perspective view which shows the structure of a mobile body detection apparatus, (B) is a circuit diagram. It is explanatory drawing which shows the film | membrane structure and magnetic characteristic of SV-GMR element used by embodiment of this invention. In Embodiment 1, it is a relationship between the convex part position of a soft-magnetic-material gear, and the direction of the magnetic flux in a magnetic sensing point, Comprising: (A) is an explanation when a convex part approaches, (B) is an explanation when a convex part moves away. FIG. It is a typical perspective view of Embodiment 2 of the present invention. It is a typical perspective view of Embodiment 3 of the present invention. FIG. 2A is a diagram illustrating a conventional element arrangement and signal output and differential output of each element, where FIG. 3A is an explanatory diagram of the element arrangement of the prior art, and FIG. (C) is a differential output waveform diagram of each element in the case of the optimum element arrangement of the prior art, (D) is a signal output waveform diagram from each element when explaining the problems of the prior art, ( E) is a differential output waveform diagram of each element when the problem of the prior art is described. It is the relationship between the convex and convex pitch P of the soft magnetic gear and the differential output (the detected output voltage from the Wheatstone bridge), (A) is the differential output in the case of the element arrangement of the prior art, and (B) is SV−. It is a graph which shows each differential output at the time of GMR element use.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soft magnetic gear 2 Convex part 5 Bias magnet R1, R2, R3, R4 SV-GMR element

Claims (5)

A magnetic material moving body having at least one convex portion or concave portion;
A bias magnet that generates a magnetic field, wherein the magnetic material moving body and the magnetic pole surface face each other, and the magnetic pole surface faces or does not face the convex portion or the concave portion as the magnetic material moving body moves. ,
A moving body detection device connected to form a bridge circuit and having at least one pair of spin-valve giant magnetoresistive elements located between the magnetic pole surface of the magnetic material moving body and the bias magnet ,
The moving body detection characterized in that the pin layer magnetization directions of the paired spin-valve giant magnetoresistive elements are arranged so as to be substantially forward and substantially opposite to the moving direction of the magnetic material moving body. apparatus. The movement according to claim 1, wherein the paired spin valve type giant magnetoresistive elements are arranged side by side in a direction substantially perpendicular to a moving direction of the magnetic material moving body and a height direction of the convex portion or the concave portion. Body detection device. The spin-valve giant magnetoresistive element pairs, the magnetic material moving member and claim 1 Symbol placement movement detection apparatus of arranged to overlap the gap direction between the bias magnet. There are two pairs of the spin-valve giant magnetoresistive elements arranged so as to overlap each other in the gap direction, and two pairs of the spin-valve giant magnetoresistive elements are arranged in the moving direction of the magnetic material moving body and the convex portion or concave portion. The moving body detection device according to claim 3, which is arranged side by side in a direction that is substantially perpendicular to the height direction. Moving object detection apparatus according to any one of claims 1 wherein the spin-valve giant magnetoresistive element in a pair and has a Daburumianda pattern consisting of two parallel meander patterns to each other as a magnetic resistance pattern 4.

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