JP2009222426A - Magnetic detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic detection device capable of detecting the movement of a member being an object to be detected with high accuracy, and moreover capable of detecting the direction of the movement. <P>SOLUTION: On a substrate 30, a plurality of magnetoresistive elements (MRE) 34 are formed so as to be mutually parallel, and moreover wiring patterns 35, 36 and terminals 37, 38 for independently acquiring electric signals representing resistance changes in the individual MREs 34 are formed. As a result, it becomes possible to perform high-accuracy detection of the rotation movement of a rotor 20 and detection of its rotation direction, from the electric signals representing the resistance changes by the individual MREs 34. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic detection device that detects a movement such as rotation of a member to be detected based on a resistance change of a magnetoresistive element.

As a conventional magnetic detection device, for example, one described in Patent Document 1 is known. The magnetic detection device described in Patent Document 1 forms a magnetic sensor (magnetic detection element) by arranging a plurality of plate-like magnetic thin films in parallel and connecting the plurality of magnetic thin films in series. At this time, the impedance change of the magnetic sensor with respect to the externally applied magnetic field changes linearly by narrowing the width of the magnetic thin film at the center.
JP 2005-291863 A

  In the above conventional magnetic detector, a plurality of plate-like magnetic thin films are arranged in parallel, but they are connected in series to form a magnetic sensor, so that the impedance of each (one by one) magnetic thin film is Even if it changes, it cannot grasp | ascertain how much the impedance of which magnetic thin film changed from the output of the magnetic sensor. Therefore, it is impossible to detect the movement of the detection target member with high accuracy and to detect the movement direction.

  The present invention has been made in view of the above-described points, and provides a magnetic detection device capable of detecting the movement of a detection target member with high accuracy and further detecting the movement direction thereof. Objective.

In order to achieve the above object, the magnetic detection device according to claim 1 comprises:
A magnet that generates a bias magnetic field toward a detection target member made of a magnetic material;
A magnetoresistive element that is placed in the bias magnetic field so that the bias magnetic field intersects and changes the direction of the bias magnetic field due to the movement of the member to be detected; Have
The magnetoresistive element is formed of a plurality of rectangular thin films formed on the substrate so as to be parallel to each other, and wiring for independently taking out an electrical signal indicating a resistance change in each thin film is provided on the substrate. It is characterized by being formed.

  As described above, in the magnetic detection device according to claim 1, the magnetoresistive element is composed of a plurality of rectangular thin films formed in parallel to each other on the substrate, and further, the resistance change in each thin film is formed on the substrate. Wiring for independently taking out the electrical signal indicating is formed. For this reason, the electric signal which shows the resistance change by each thin film can be taken out independently, respectively. As a result, it is possible to detect the movement of the detection target member with high accuracy from these electrical signals and to detect the movement direction of the detection target member.

As described in claim 2, the substrate is provided with an inclined portion on the surface of the substrate, and the plurality of rectangular thin films forming the magnetoresistive element are formed on the inclined portion,
The member to be detected is a disk-shaped rotor provided rotatably, and an outer peripheral surface thereof is inclined with a predetermined angle with respect to a direction parallel to the rotation axis, Is formed,
The bias magnetic field attracted to the crests formed on the outer peripheral surface of the rotor changes its direction in the thickness direction of the substrate as the rotor rotates, so that a plurality of rectangular elements forming the magnetoresistive element are formed. It is preferable that the crossing angle between the shape thin film and the bias magnetic field is changed to cause a resistance change in each rectangular thin film.

  A plurality of rectangular thin films that form magnetic sensing elements are formed on the inclined portion formed on the substrate surface, and the bias magnetic field changes its direction in the thickness direction of the substrate when the rotor rotates. Thus, the bias magnetic field and each rectangular thin film intersect each other in an intersecting angle range in which the resistance change monotonously increases (or monotonously decreases). For this reason, the magnitude | size of resistance change of each rectangular thin film when a rotor rotates can be enlarged.

  According to a third aspect of the present invention, it is preferable that the peak portion formed on the outer peripheral surface of the rotor is formed so that the tip side is narrower than the root side. As a result, the bias magnetic field is easily concentrated on the mountain portion, so that the magnetic field density of the bias magnetic field can be increased.

  Further, as described in claim 4, a magnetic film is formed on a crest formed on the outer peripheral surface of the rotor, or a crest formed on the outer peripheral surface of the rotor as described in claim 5. However, even if it is magnetized to a polarity that attracts the bias magnetic field generated by the magnet, the same effect as in the case of claim 3 can be obtained.

  According to a sixth aspect of the present invention, the plurality of rectangular thin films constituting the magnetoresistive element are preferably formed at equal intervals on the substrate. Thereby, when detecting the motion of the member to be detected from the resistance change of the plurality of rectangular thin films, the detection accuracy can be evenly increased, and the timing deviation when detecting the motion direction can be reduced. Can do.

  As described in claim 7, a Ni alloy having an anisotropic effect of magnetoresistance can be used as a material for forming a plurality of rectangular thin films constituting the magnetoresistive element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a main part of a magnetic detection device 10 according to the present embodiment.

  As shown in FIG. 1, the magnetic detection device 10 is formed with a substantially disk-shaped rotating body (rotor) 20 rotatably provided as a detection target member, and a magnetoresistive element (MRE) 34 as a magnetic detection element. It is comprised by the board | substrate 30 and the bias magnet 40 which generate | occur | produces a bias magnetic field. The outer surface of the rotor 20 is opposed to the bias magnet 40, and the magnetic center axis of the bias magnet 40 is disposed so as to face the rotation axis of the rotor 20. For example, when the bias magnet 40 is formed in a cylindrical shape, the cylindrical central axis is a magnetic central axis of the bias magnet 40. The bias magnet 40 may have a hollow cylindrical shape. Then, the end face of the columnar or hollow cylindrical bias magnet 40 is magnetized so that the face close to the rotor 20 has N pole and the far face becomes S pole. However, the surface close to the rotor 20 may be magnetized so that the south pole is the south pole and the far surface is the north pole.

  The rotor 20 is made of a magnetic material such as iron. As shown in FIGS. 2 and 3, the outer peripheral surface of the rotor 20 is inclined at a predetermined angle with respect to a direction parallel to the rotation axis of the rotor 20. And troughs 22 are alternately formed. As shown in FIG. 2, the mountain portion 21 is formed so that its thickness becomes thinner from the root to the tip. In addition, the interval between the peaks 21 with the valleys 22 in between is constant.

  Thus, since the crests 21 and the troughs 22 are alternately formed on the outer peripheral surface of the rotor 20, the crests facing the MRE 34 formed on the substrate 30 when the rotor 20 rotates. The position of 21 changes periodically in the thickness direction of the rotor 20 as indicated by the dotted arrows in FIG. For this reason, the bias magnetic field from the bias magnet 40 toward the outer peripheral surface of the rotor 20 is attracted to the peak portion 21, so that the bias magnetic field is represented by a dotted arrow in FIG. 2 according to the change in the position of the peak portion 21. The direction of the substrate 30 is changed in the thickness direction.

  The substrate 30 is disposed between the rotor 20 and the bias magnet 40 so that a bias magnetic field from the bias magnet 40 toward the outer peripheral surface of the rotor 20 acts. When the bias magnet 40 has a hollow cylindrical shape, the substrate 30 (a part thereof) may be disposed in the hollow portion. The configuration of the substrate 30 will be described in more detail with reference to FIG.

  As shown in FIG. 2, the substrate 30 includes a semiconductor substrate 31 formed of, for example, silicon. On the semiconductor substrate 31, a structure 32 such as polysilicon is formed. The structure 32 is for forming an inclined portion on the semiconductor substrate 31. That is, when an insulating film 33 such as a BPSG film is deposited on the semiconductor substrate 31 on which the structure 32 is formed, the height of the insulating film 33 at the formation position of the structure 32 is the highest and is directed toward the periphery. It is possible to form a sloping portion that falls gently.

  The MRE 34 is formed of a Ni alloy having an anisotropic effect of magnetoresistance such as Ni—Co or Ni—Fe, and is disposed on the inclined portion described above. That is, when forming the MRE 34, first, a thin Ni alloy is vapor-deposited on the insulating film 33 having the inclined portion by sputtering or CVD. Thereafter, patterning is performed so that only the rectangular Ni alloy thin film remains in the inclined portion.

  Here, the MRE 34 has a rectangular shape having a long side and a short side, and a plurality of Ni alloy thin films (that is, a plurality of MREs 34) are arranged at equal intervals so as to be parallel to each other in the inclined portion of the substrate 30. It is formed. Each MRE 34 has a longitudinal direction along a bias magnetic field from the bias magnet 40 toward the rotor 20.

  On the insulating film 33 of the substrate 30, as shown in FIG. 2, wiring patterns 35 and 36 that are electrically connected to both ends in the longitudinal direction of the MRE 34 are formed. The wiring patterns 35 and 36 are made of a metal thin film having good conductivity such as aluminum. As shown in FIG. 5, the wiring patterns 35 and 36 are connected to individual output terminals 37, and the other wiring pattern 36 is a common terminal (power supply terminal or GND terminal) 38. It is connected to the. In this way, when one wiring pattern 35 is connected to each individual output terminal 37, when a magnetic field acts on each MRE 34 and a resistance change occurs, an electrical signal indicating a resistance change in each MRE 34 is generated. It can be taken out independently.

  As shown in FIG. 6, a power supply terminal or a GND terminal may be formed as an individual terminal 39, and the wiring patterns 35 and 36 may be connected to the individual terminals 37 and 39.

  Next, the operation of the magnetic detection device 10 having the above-described configuration will be described.

  In the magnetic detection device 10 according to the present embodiment, when a current is applied to each MRE 34 formed on the substrate 30 through the terminals 37 and 38 (39), if a bias magnetic field acts on each MRE 34, In the MRE 34, a resistance change occurs according to the crossing angle between the longitudinal direction of each MRE 34 and the bias magnetic field.

  Here, in this embodiment, as described above, when the rotor 20 rotates, the direction of the bias magnetic field from the bias magnet 40 toward the rotor 20 periodically changes in the thickness direction of the substrate 30. Therefore, the electrical signal indicating the resistance change of each MRE 34 also changes periodically.

  In this embodiment, since at least one end of each MRE 34 is connected to the individual output terminal 37 via the wiring pattern 35, an electric signal indicating a resistance change in each MRE 34 can be taken out independently. it can.

  However, the resistance change in each MRE 34 differs from each other because the crossing angle with the bias magnetic field differs depending on the position of each MRE 34. FIG. 4 is a diagram illustrating an example of a state of resistance change of each MRE 34.

  Therefore, it is possible to detect the rotation of the rotor 20 with high accuracy in accordance with the difference in resistance change of each MRE 34. That is, each time the rotor 20 rotates by an angle corresponding to the arrangement interval of the MREs 34, the combination of the MREs 34 that output a resistance change pattern as shown in FIG. For this reason, the detection resolution of the rotation angle of the rotor 20 can be set to an angle corresponding to at least the arrangement interval of the MREs 34 on the substrate 30. In this embodiment, since each MRE 34 is formed in a rectangular shape on the substrate 30, it is easy to narrow the arrangement interval. In other words, the detection accuracy of the magnetic detection device 10 can be arbitrarily set according to the arrangement region, interval (density), and size of the MRE 34 on the substrate 30.

  Furthermore, as shown in FIG. 4, the resistance value of each MRE 34 faces the resistance value of the MRE 34 facing the vicinity of the starting point of the peak portion 21 in the rotation direction of the rotor 20 and the vicinity of the end point of the peak portion 21. The difference between the MRE 34 and the resistance value is the largest. Furthermore, the resistance value of the MRE 34 arranged in the direction opposite to the rotation direction of the rotor 20 gradually decreases from the resistance value of the MRE 34 facing the vicinity of the starting point of the peak portion 21. By utilizing such a resistance change pattern, the rotational direction of the rotor 20 can also be detected.

  The electrical signal extracted from each MRE 34 may be monitored as an analog signal or may be converted into a digital signal for monitoring. When converting to a digital signal, for example, the resistance value of each MRE 34 may be compared with a predetermined value and a signal indicating the magnitude may be output. In this way, it is possible to reduce the influence due to processing variations of each MRE 34.

  In the present embodiment, an inclined portion is formed on the surface of the substrate 30, and each MRE 34 is arranged on the inclined portion. Furthermore, as shown in FIG. 2, when the rotor 20 rotates, the bias magnetic field is configured to change its direction in the thickness direction of the substrate 30. For this reason, the bias magnetic field and each MRE 34 intersect in a crossing angle range in which the resistance change of the MRE 34 monotonously increases (or monotonously decreases). Thereby, the magnitude | size of resistance change of each MRE34 when the rotor 20 rotates can be enlarged.

  Furthermore, since the plurality of MREs 34 are formed at equal intervals on the substrate 30, the detection accuracy can be increased evenly when the rotational motion of the rotor 20 is detected from the resistance change of the plurality of MREs 34. It is also possible to reduce a timing shift when detecting the direction.

  In the above-described embodiment, the peak portion 21 formed on the outer peripheral surface of the rotor 20 is formed so that the tip side is narrower than the root side. For this reason, the bias magnetic field is easily concentrated on the peak portion, and the magnetic field density of the bias magnetic field acting on each MRE 34 formed on the substrate 30 can be increased.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the detection target member is the rotor 20 that is a rotating body, and the rotational movement of the rotor 20 is detected. However, even if the detection target member reciprocates linearly, for example. The magnetic detection device according to the present invention can detect the distance and direction of movement of the linear motion.

  Further, in the above-described embodiment, the peak portion 21 formed on the outer peripheral surface of the rotor 20 is tapered to increase the magnetic field density of the bias magnetic field acting on each MRE 34. However, the same effect can be obtained by other configurations.

  For example, while the rotor 20 is made of a nonmagnetic material, the magnetic film is attached only to the ridges 21 formed on the outer peripheral surface of the rotor 20. Further, the peak portion 21 formed on the outer peripheral surface of the rotor 20 may be magnetized to a polarity that attracts the bias magnetic field generated by the bias magnet 40. In either case, the direction of the bias magnetic field can be concentrated on the peak portion 21.

  In the above-described embodiment, the example in which the seven MREs 34 are formed on the substrate 30 has been described. However, the number of the MREs 34 is not limited to this. However, in order to detect the above-described resistance change pattern, it is preferable to form at least three MREs.

It is a block diagram which shows the structure of the principal part of the magnetic detection apparatus by embodiment. It is explanatory drawing for demonstrating the structure of the rotor and board | substrate in a magnetic detection apparatus. It is a side view which shows the peak part and trough part which were formed in the outer peripheral surface of the rotor in the shape of a screw. It is a figure which shows an example of the mode of a resistance change of each MRE. It is a figure which shows an example of the wiring pattern in a board | substrate. It is a figure which shows the other example of the wiring pattern in a board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic detection apparatus 20 Rotor 21 Mountain part 22 Valley part 30 Substrate 34 Magnetoresistive element (MRE)
35, 36 Wiring pattern 40 Bias magnet

Claims (7)

A magnet that generates a bias magnetic field toward a detection target member made of a magnetic material;
A magnetoresistive element that is placed in the bias magnetic field so that the bias magnetic field intersects and changes the direction of the bias magnetic field due to the movement of the member to be detected; A magnetic detection device comprising:
The magnetoresistive element is formed of a plurality of rectangular thin films formed on the substrate so as to be parallel to each other, and a wiring for independently taking out an electric signal indicating a resistance change in each thin film, A magnetic detection device formed on a substrate. The substrate is provided with an inclined portion on the substrate surface, and a plurality of rectangular thin films forming the magnetoresistive element are formed on the inclined portion,
The member to be detected is a disk-shaped rotor provided rotatably, and an outer peripheral surface thereof is inclined with a predetermined angle with respect to a direction parallel to the rotation axis, Is formed,
The bias magnetic field attracted to the crests formed on the outer peripheral surface of the rotor changes its direction in the thickness direction of the substrate as the rotor rotates, so that a plurality of rectangular elements forming the magnetoresistive element are formed. The magnetic detection device according to claim 1, wherein the crossing angle between the shape thin film and the bias magnetic field changes to cause a resistance change in each rectangular thin film.   The magnetic detection device according to claim 2, wherein the peak portion formed on the outer peripheral surface of the rotor is formed with a tip end side narrower than a root side.   The magnetic detection device according to claim 2, wherein a magnetic film is formed as a magnetic material on a peak portion formed on an outer peripheral surface of the rotor.   4. The magnetic detection device according to claim 2, wherein a peak formed on an outer peripheral surface of the rotor is magnetized to a polarity that attracts a bias magnetic field generated by the magnet.   6. The magnetic detection device according to claim 1, wherein the plurality of rectangular thin films forming the magnetoresistive element are formed at equal intervals on the substrate.   7. The magnetic detection according to claim 1, wherein a Ni alloy having an anisotropic effect of magnetoresistance is used as a material for forming the plurality of rectangular thin films constituting the magnetoresistive element. apparatus.

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