JP4154524B2 - Rotary magnetic sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary magnetic sensor, and more particularly to a rotary magnetic sensor used for rotational position detection and speed detection of a machine tool, an automobile, and the like.
[0002]
[Prior art]
This type of magnetic sensor normally constitutes one magnetic sensor by setting two magnetoelectric transducers as a set. A multi-phase sensor that includes a plurality of magnetic sensors and detects rotation detection signals having different phases output from the respective magnetic sensors is known.
[0003]
By the way, in the multiphase sensor, a plurality of magnetoelectric transducers are arranged along the rotation direction of the gear. For example, FIG. 6 is an enlarged view showing four magnetoelectric conversion elements 2a, 2b, 3a, 3b of the two-phase rotating magnetic sensor and a part of the gear 20 that is a detected object. In FIG. 6, reference numeral 10 denotes a substrate on which the magnetoelectric conversion elements 2 a to 3 b are formed, reference numeral 13 denotes a magnet, reference numeral 21 denotes a convex portion (tooth) of the gear 20, and reference numeral 22 denotes a concave portion of the gear 20. . The magnetoelectric conversion elements 2a and 2b constitute one magnetic sensor 2, and the magnetoelectric conversion elements 3a and 3b constitute one magnetic sensor 3. The gear 20 rotates in the direction of arrow K. When the magnetoelectric conversion element 2 a faces the tooth 21 of the gear 20, the magnetoelectric conversion element 2 b is installed so as to face the recess of the gear 20. Magnetoelectric conversion elements 3a and 3b are similarly installed.
[0004]
At this time, if the intensity of the magnetic field applied to each of the two magnetoelectric conversion elements 2a and 2b constituting one magnetic sensor 2 is equal, an ideal waveform rotation detection signal without waveform distortion is output. However, since a plurality of the magnetoelectric conversion elements 2a to 3b are arranged, for example, one magnetoelectric conversion element 2a and the other magnetoelectric conversion element 2b constituting the magnetic sensor 2 are arranged apart from each other. Accordingly, the distance R1 from the gear 20 to the magnetoelectric conversion element 2a and the distance R2 from the gear 20 to the magnetoelectric conversion element 2b differ depending on the arrangement position of the magnetoelectric conversion element. As a result, the strength of the magnetic field applied to each of the magnetoelectric conversion elements 2a and 2b differs, and the rotation detection signal waveform deviates from an ideal sine wave.
[0005]
The distances R1 and R2 do not mean the distance from the actual gear 20 to the magnetoelectric conversion elements 2a and 2b, but the teeth 21 of the gear 20 are arranged at positions closest to the magnetoelectric conversion elements 2a and 2b. It means the distance (shortest distance). Therefore, more specifically, the distances R1 and R2 are distances between the imaginary line L connecting the tops of the teeth 21 of the gear 20 and the magnetoelectric transducers 2a and 2b. Furthermore, since the resistances of the magnetoelectric conversion elements 2 a and 2 b change depending on the magnetic flux passing vertically, the distances R <b> 1 and R <b> 2 must be perpendicular to the substrate 10.
[0006]
When the magnetoelectric conversion element 2b closer to the gear 20 is connected to the ground and the magnetoelectric conversion element 2a far from the gear 20 is connected to the power source, the magnetic field applied to the magnetoelectric conversion element 2b is applied to the magnetoelectric conversion element 2a. Since the magnetic field is stronger than the applied magnetic field, as shown by the dotted line in FIG. 7, the rotation detection signal has a sine wave peak (0 ° to 180 ° portion) and a valley ( Waveform narrows at 180 ° to 360 °).
[0007]
Therefore, as one method for solving this problem, a rotation detection device described in Patent Document 1 has been proposed. This rotation detection device is attached to the outer peripheral side of the rotor magnet of the surface facing motor and is generated by rotation of the rotation detecting magnet having a plurality of magnetic poles magnetized with the same width along the circumferential direction. And a plurality of magnetoelectric transducers for detecting a change in the magnetic field. And the magnetoelectric conversion element is arrange | positioned on the circumference of the same center as a magnet, and all the gaps of each magnetoelectric conversion element and a magnet are made the same. Thereby, since the magnetic field of a magnet acts uniformly on each magnetoelectric conversion element, an output waveform with small waveform distortion can be obtained.
[0008]
[Patent Document 1]
JP-A-6-261524
[Problems to be solved by the invention]
Therefore, when the technique of Patent Document 1 is applied to the two-phase rotating magnetic sensor shown in FIG. 6 and a curved substrate 10 ′ is used as shown in FIG. All distances up to 20 are equal. However, the formation of the magnetoelectric conversion elements 2a to 3b on the curved substrate 10 ′ requires a high level of technology as compared with the case where the magnetoelectric conversion elements 2a to 3b are formed on a flat surface, and the yield is low and the cost is high. There is. Furthermore, since the distance from the magnetoelectric conversion elements 2a to 3b to the magnet 13 is different and the magnetic field strength of each of the magnetoelectric conversion elements 2a to 3b is not uniform, the same problem, that is, the problem that the output waveform is greatly distorted eventually occurs. It will be.
[0010]
Therefore, an object of the present invention is to provide a rotating magnetic sensor in which a magnetic field of a magnet is uniformly applied to each magnetoelectric conversion element even when a plurality of magnetoelectric conversion elements are formed on a plane.
[0011]
[Means and Actions for Solving the Problems]
In order to achieve the above object, a rotary magnetic sensor according to the present invention includes a nonmagnetic substrate having a plurality of magnetoelectric conversion elements provided on the surface, a magnet disposed on the back surface of the nonmagnetic substrate, and a magnetoelectric conversion element. And a rotating magnetic sensor that detects a rotating state of the rotating body based on a rotation detection signal output from the magnetoelectric conversion element, wherein the rotating body is rotated by the rotation of the rotating body. Is magnetized so that the magnetic field from the magnet is applied to each of the magnetoelectric conversion elements with the same intensity when placed at the position closest to the magnetoelectric conversion element.
[0012]
More specifically, the magnetic flux density distribution on the surface of the magnet is perpendicular to the nonmagnetic substrate from each of the magnetoelectric conversion elements, with reference to the case where the rotating body is disposed at the position closest to the magnetoelectric conversion element. The magnet is magnetized so as to have a magnetic flux density distribution proportional to the square of the distance to the rotating body.
[0013]
With the above configuration, even when a plurality of magnetoelectric conversion elements are formed on a plane, a uniform magnetic bias is applied to each of the magnetoelectric conversion elements, and an output waveform with small waveform distortion is obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a rotary magnetic sensor according to the present invention will be described below with reference to the accompanying drawings.
[0015]
FIG. 1 is an external perspective view of a sensor body 1 of a two-phase rotational magnetic sensor, FIG. 2 is a schematic configuration diagram of the two-phase rotational magnetic sensor, and FIG. 3 is an electric circuit diagram of the two-phase rotational magnetic sensor. The two-phase rotating magnetic sensor is roughly composed of a sensor main body 1 and a gear 20 that is an object to be detected. The sensor body 1 includes a nonmagnetic substrate 10 having magnetoresistive elements 2a, 2b, 3a, 3b formed on the surface, a magnet 13 disposed on the back surface of the nonmagnetic substrate 10, a nonmagnetic protective case 16, and the like. It is configured.
[0016]
The magnetoresistive elements 2a to 3b are configured by linear magnetoresistive patterns in order to obtain a predetermined magnetic resistance. These magnetoresistive elements 2a to 3b are arranged at a predetermined pitch so that the passing direction K of the tooth 21 of the gear 20 and the longitudinal direction have a vertical relationship. The magnetoresistive elements 2a and 2b constitute one magnetic sensor 2, and the magnetoresistive elements 3a and 3b constitute another magnetic sensor 3.
[0017]
The magnetoresistive elements 2a to 3b are arranged side by side in the passing direction K of the teeth 21 of the gear 20, and the pitch interval between the magnetoresistive elements 2a and 2b and the pitch interval between the magnetoresistive elements 3a and 3b are respectively It is set to ½ of the pitch interval of the teeth 21.
[0018]
The magnetoresistive elements 2a to 3b are formed by, for example, providing a compound semiconductor such as InSb, InAs, or GaAs in a thin film form on the nonmagnetic substrate 10 by vapor deposition or sputtering, and then forming In, TiAl on the surface of the compound semiconductor thin film. , NiCr, Au, Ag, Cu, Al, etc. are formed at a predetermined pitch by a method such as vapor deposition or sputtering. Alternatively, the magnetoresistive pattern may be one in which a metal film such as In, TiAl, NiCr, Au, Ag, Cu, and Al is formed at a predetermined pitch on the surface of the single crystal semiconductor substrate 10 such as InSb.
[0019]
The non-magnetic substrate 10 is formed by depositing an InSb film or the like on an insulator substrate by vapor deposition or the like, a single crystal semiconductor substrate such as InSb, or a semiconductor thin film or single crystal substrate formed separately, as an insulating substrate such as glass or alumina. A composite substrate obtained by pasting with an adhesive is used. In the conventional case, a magnetic substrate is normally used for concentrating the bias magnetic field of the magnet 13 on the substrate. However, in the present invention, when the bias magnetic field of the magnet 13 is concentrated, the rotation detection signal Do not use because waveform distortion increases.
[0020]
A surface (back surface) opposite to the mounting surface of the magnetoresistive elements 2a to 3b of the nonmagnetic substrate 10 is bonded to the magnet 13 with an adhesive. The magnet 13 may be a permanent magnet or an electromagnet.
[0021]
After the magnet 13 is mounted on the holder 14, the magnet 13 is accommodated in the nonmagnetic protective case 16. The holder 14 is made of a thermosetting resin such as epoxy or phenol, a thermoplastic resin such as nylon, PBT, or PPS, a liquid crystal polymer such as LCP, or alumina. Each of the four lead terminals 18 a to 18 d is inserted through a through hole 14 a provided in the holder 14. The head 19 of each lead terminal 18a-18d and the magnetoresistive elements 2a-3b are connected via a wire 17 (or lead frame).
[0022]
Thereafter, molten resin is injected from the opening of the nonmagnetic protective case 16 to form the casting resin 15. As the casting resin 15, an epoxy resin having excellent moisture resistance and relatively high mechanical strength is used. The nonmagnetic protective case 16 is made of a nonmagnetic material such as beryllium copper, phosphor bronze, brass, white, nonmagnetic stainless steel, aluminum, ceramic, or resin.
[0023]
The gear 20 faces the sensor body 1 such that the teeth 21 face the magnetoresistive elements 2a to 3b. The gear 20 is made of a ferromagnetic material.
[0024]
Next, the effect of the rotary magnetic sensor having the above configuration will be described. FIG. 3 is an electric circuit diagram of the rotating magnetic sensor. Magnetoresistive elements 2a to 3b are connected in series and parallel between the power lead terminal 18a and the ground lead terminal 18d.
[0025]
The magnetic flux emitted from the N pole of the magnet 13 returns to the S pole of the magnet 13 through the gear 20. At this time, the magnetic flux emitted from the N pole of the magnet 13 is concentrated on the tooth 21 of the gear 20 that is closest to the N pole of the magnet 13. Accordingly, when the gear 20 rotates in the direction indicated by the arrow K, the position where the magnetic flux concentrates also moves as the gear 20 rotates. Thereby, the magnetic flux which permeate | transmits magnetoresistive element 2a-3b changes with the movement of the tooth | gear 21 of the gearwheel 20. FIG. The resistance values of the magnetoresistive elements 2a to 3b increase as the transmitted magnetic flux increases. Accordingly, the resistance values of the magnetoresistive elements 2a to 3b change due to the change of the magnetic flux.
[0026]
When the resistance values of the magnetoresistive elements 2a to 3b change as the teeth 21 of the gear 20 move, sine wave rotation detection signals S1 and S2 are output to the output lead terminals 18b and 18c, respectively. The rotation detection signals S1 and S2 have a phase difference of 90 °.
[0027]
Here, when the rotation detection signals S1 and S2 deviate from the ideal sine wave as shown by the dotted lines in FIG. 7, it is difficult to accurately detect the angle with the voltage values of the rotation detection signals S1 and S2. .
[0028]
Therefore, in the present embodiment, the magnetic flux density distribution on the surface of the magnet 13 is represented by the magnetoresistive elements 2a to 3b with reference to the time when the teeth 21 of the gear 20 are disposed at positions closest to the magnetoresistive elements 2a to 3b. The magnet 13 is magnetized so as to have a magnetic flux density distribution proportional to the square of the distance R from each of the gears 20 to the gear 20.
[0029]
In general, since the strength of the magnetic field is inversely proportional to the square of the distance, the magnetic field becomes weaker as the distance R to the gear 20 increases. Therefore, the magnetic flux density is differentiated in advance so as to cancel the change in the magnetic field strength due to the distance.
[0030]
Thereby, when the gear 20 rotates and the tooth 21 of the gear 20 is disposed at a position closest to the magnetoresistive elements 2a to 3b, the magnetic field from the magnet 13 is equal to each of the magnetoresistive elements 2a to 3b. Apply with intensity. As a result, rotation detection signals S1 and S2 with small waveform distortion can be obtained.
[0031]
The distance R does not mean the distance from the actual gear 20 to the magnetoelectric conversion elements 2a to 3b, but the teeth 21 of the gear 20 are arranged at positions closest to the magnetoelectric conversion elements 2a to 3b. It means the distance (shortest distance). Therefore, more specifically, the distance R is the distance from the phantom line L connecting the tops of the teeth 21 of the gear 20 to the magnetoelectric transducers 2a to 3b. Further, since the resistance of the magnetoelectric conversion elements 2 a to 3 b changes depending on the magnetic flux passing vertically, the distance R must be a distance taken in the vertical direction with respect to the nonmagnetic substrate 10.
[0032]
Further, the magnetic flux density distribution on the surface of the magnet 13 has a magnetic flux density distribution proportional to the square of the distance R from each of the magnetoresistive elements 2a to 3b to the gear 20, so that the gear 20 and the magnet 13 are uniform. The rotation detection signals S1 and S2 having the same output voltage can be obtained.
[0033]
FIG. 4 is a graph showing the magnetic flux density distribution of the magnet 13 whose length in the short side direction is 10 mm. In order to obtain the magnet 13 having such a magnetic flux density distribution, as shown in FIG. 5, the tip of the magnetizing yoke 32 of the magnetizing device is attached to one end of a rectangular ferromagnetic material that is a raw material of the magnet 13. Then, the ferromagnetic material is magnetized by causing a current to flow through the magnetizing coil 31 to generate a magnetic field. At this time, a so-called arc-shaped magnetization method is employed in which the number of turns of the magnetizing coil 31 at the center of the magnetizing yoke 32 is minimized and the number of turns is increased toward the outside. FIG. 5 is a view as seen from the short side of the magnet 13.
[0034]
In addition, since the magnetoresistive elements 2a to 3b of the two-phase rotational magnetic sensor of the present embodiment may be formed on the plane of the nonmagnetic substrate 10, a normal pattern manufacturing technique can be used and the yield is also good.
[0035]
The rotary magnetic sensor according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist. For example, in the above-described embodiment, a magnetoresistive element is used as the magnetoelectric conversion element. However, the present invention is not limited to this, and a Hall element, Hall IC, a ferromagnetic thin film element made of NiFe or NiCo, or the like may be used.
[0036]
【The invention's effect】
As is apparent from the above description, according to the present invention, since the magnet is magnetized so that the magnetic field from the magnet is applied to each of the magnetoelectric transducers with equal strength, the magnetoelectric transducer is placed on a plane. Even when formed, a uniform magnetic bias is applied to each of the magnetoelectric transducers, and a rotation detection signal with small waveform distortion is obtained. As a result, it is possible to accurately detect the rotational position and speed of machine tools, automobiles, and the like.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing an example of a sensor main body of a rotary magnetic sensor according to the present invention.
FIG. 2 is a schematic sectional view showing an embodiment of a rotary magnetic sensor according to the present invention.
3 is an electric circuit diagram of the rotary magnetic sensor shown in FIG. 2. FIG.
4 is a graph showing the magnetic flux density distribution of the magnet shown in FIG.
5 is a cross-sectional view for explaining a magnetizing method of the magnet shown in FIG.
FIG. 6 is an enlarged view showing a part of a magnetoelectric conversion element and a gear as a detection object.
FIG. 7 is a graph showing a waveform of a rotation detection signal.
FIG. 8 is an enlarged view showing a part of a gear that is a magnetoelectric conversion element and an object to be detected.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sensor main body 2, 3 ... Magnetic sensor 2a, 2b, 3a, 3b ... Magnetoresistive element 10 ... Nonmagnetic board | substrate 13 ... Magnet 20 ... Gear

Claims (3)

A non-magnetic substrate having a plurality of magnetoelectric conversion elements provided on the surface;
A magnet disposed on the back surface of the non-magnetic substrate;
A rotating body that is an object to be detected facing the magnetoelectric conversion element,
In the rotating magnetic sensor that detects the rotation state of the rotating body by the rotation detection signal output from the magnetoelectric conversion element,
The magnet so that the magnetic field from the magnet is applied to each of the magnetoelectric conversion elements with equal strength when the rotary body is disposed at a position closest to the magnetoelectric conversion elements by the rotation of the rotary body. Is magnetized,
Rotational magnetic sensor characterized by A non-magnetic substrate having a plurality of magnetoelectric conversion elements provided on the surface;
A magnet disposed on the back surface of the non-magnetic substrate;
A rotating body that is an object to be detected facing the magnetoelectric conversion element,
In the rotating magnetic sensor that detects the rotation state of the rotating body by the rotation detection signal output from the magnetoelectric conversion element,
Based on the rotation of the rotating body, the magnetic flux density distribution on the surface of the magnet is changed from each of the magnetoelectric conversion elements to the non-magnetizing element with reference to the time when the rotating body is disposed at a position closest to the magnetoelectric conversion element. The magnet is magnetized so as to have a magnetic flux density distribution proportional to the square of the distance to the rotating body taken in a direction perpendicular to the body substrate;
Rotational magnetic sensor characterized by The rotary magnetic sensor according to claim 1, wherein the rotation detection signal is at least two signals having different phases.

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