JP2004340669A - Rotary magnetometric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary magnetometric sensor wherein the magnetic field of a magnet is uniformly impressed on respective magnetoelectric conversion elements even if the plurality of conversion elements are formed on a plane. <P>SOLUTION: This two-phase rotary magnetometric sensor substantially comprises a sensor body and a gear which is an object under detection. The sensor body comprises a nonmagnetic substrate with magneto-resistive elements 2a to 3b formed on its front surface, a magnet 13 disposed on the rear surface of the nonmagnetic substrate, a nonmagnetic protective case, etc. The magnet 13 is magnetized so as to have a magnetic flux density distribution in which magnetic flux density is distributed on a surface of the magnet 13 proportional to the square of distance R to the gear taken along a vertical direction to the nonmagnetic substrate from each of the elements 2a to 3b relative to the gear disposed in a position most contiguous to the elements 2a to 3b as the reference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotating magnetic sensor, particularly to a rotating magnetic sensor used for detecting a rotational position and a speed of a machine tool, an automobile, and the like.
[0002]
[Prior art]
This type of magnetic sensor usually constitutes one magnetic sensor by setting two magnetoelectric conversion elements 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 polyphase sensor, a plurality of magnetoelectric conversion elements 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, which is an object to be detected. 6, reference numeral 10 denotes a substrate on the surface of which the magnetoelectric conversion elements 2a to 3b are formed, reference numeral 13 denotes a magnet, reference numeral 21 denotes a convex portion (teeth) of the gear 20, and reference numeral 22 denotes a concave portion of the gear 20. . One magnetic sensor 2 is constituted by the magneto-electric conversion elements 2a and 2b, and one magnetic sensor 3 is constituted by the magneto-electric conversion elements 3a and 3b. The gear 20 rotates in the direction of arrow K. When the magnetoelectric conversion element 2 a faces the teeth 21 of the gear 20, the magnetoelectric conversion element 2 b is installed so as to face the concave portion of the gear 20. The magneto-electric conversion elements 3a and 3b are installed similarly.
[0004]
At this time, if the strengths of the magnetic fields applied to the two magnetoelectric conversion elements 2a and 2b constituting one magnetic sensor 2 are equal, a rotation detection signal having an ideal waveform without waveform distortion is output. However, since a plurality of magneto-electric conversion elements 2a to 3b are arranged, for example, one magneto-electric conversion element 2a and the other magneto-electric conversion element 2b constituting the magnetic sensor 2 are arranged apart from each other. Therefore, 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 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 waveform of the rotation detection signal deviates from an ideal sine wave.
[0005]
Note that the distances R1 and R2 do not mean the actual distance from the gear 20 to the magneto-electric conversion elements 2a and 2b, and the teeth 21 of the gear 20 are arranged at positions closest to the magneto-electric conversion elements 2a and 2b. It means the distance at the time (the shortest distance). Therefore, more specifically, the distances R1 and R2 are the distances between the virtual line L connecting the tops of the teeth 21 of the gear 20 and each of the magnetoelectric conversion elements 2a and 2b. Further, since the resistance of the magnetoelectric conversion elements 2a and 2b changes due to the magnetic flux passing vertically, the distances R1 and R2 must be distances taken in the vertical direction with respect 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 farther from the gear 20 is connected to the power supply, the magnetic field applied to the magnetoelectric conversion element 2b is applied to the magnetoelectric conversion element 2a. Since the applied magnetic field is stronger than the applied magnetic field, as shown by the dotted line in FIG. 7, the waveform of the rotation detection signal swells at the peak (0 ° to 180 °) of the sine wave and the valley ( The waveform narrows at a portion between 180 ° and 360 °).
[0007]
Therefore, as one method for solving this problem, a rotation detecting device described in Patent Document 1 has been proposed. This rotation detecting device is mounted on the outer peripheral side of a rotor magnet of a surface-facing motor, and has a rotation detecting magnet having a plurality of magnetic poles magnetized at the same width along a circumferential direction, and is generated by rotation of the magnet. A plurality of magneto-electric conversion elements for detecting a change in a magnetic field. Then, the magnetoelectric conversion elements are arranged on the same circumference as the magnet, and the gaps between each magnetoelectric conversion element and the magnet are all the same. As a result, the magnetic field of the magnet uniformly acts on each magneto-electric conversion element, so that 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 technology of Patent Document 1 is applied to the two-phase rotating magnetic sensor shown in FIG. 6 and the curved substrate 10 ′ is used as shown in FIG. 8, the gears are surely removed from each of the magnetoelectric conversion elements 2 a to 3 b. The distances to 20 are all equal. However, forming the magnetoelectric conversion elements 2a to 3b on a curved substrate 10 'requires a higher 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 magneto-electric conversion elements 2a to 3b to the magnet 13 is different and the magnetic field strength of each of the magneto-electric conversion elements 2a to 3b is not uniform, the same problem, that is, a problem that the output waveform is greatly distorted occurs. 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 magneto-electric conversion element even when a plurality of magneto-electric conversion elements are formed on a plane.
[0011]
Means and action for solving the problem
In order to achieve the above object, a rotating magnetic sensor according to the present invention includes a non-magnetic substrate having a plurality of magneto-electric conversion elements provided on a front surface thereof, a magnet disposed on a back surface of the non-magnetic substance substrate, and a magneto-electric conversion element. A rotating magnetic sensor that detects a rotation state of the rotating body by a rotation detection signal output from the magnetoelectric conversion element, wherein the rotating body is rotated by rotation of the rotating body. Is arranged at a position closest to the magneto-electric conversion element, the magnet is magnetized such that a magnetic field from the magnet is applied to each of the magneto-electric conversion elements with equal strength.
[0012]
More specifically, the magnetic flux density distribution on the surface of the magnet is perpendicular to the non-magnetic substrate from each of the magneto-electric conversion elements with reference to when the rotating body is arranged at the position closest to the magneto-electric 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 magneto-electric conversion elements are formed on a plane, a uniform magnetic bias is applied to each of the magneto-electric conversion elements, and an output waveform with small waveform distortion can be obtained.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a rotating magnetic sensor according to the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is an external perspective view of a sensor main body 1 of a two-phase rotating magnetic sensor, FIG. 2 is a schematic configuration diagram of the two-phase rotating magnetic sensor, and FIG. 3 is an electric circuit diagram of the two-phase rotating magnetic sensor. The two-phase rotating magnetic sensor generally includes a sensor main body 1 and a gear 20 as an object to be detected. The sensor main 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]
Each of the magnetoresistive elements 2a to 3b is formed of a linear magnetoresistive pattern in order to obtain a predetermined magnetoresistance. These magnetoresistive elements 2a to 3b are arranged at a predetermined pitch so that the longitudinal direction has a vertical relationship with the passing direction K of the teeth 21 of the gear 20. One magnetic sensor 2 is constituted by the magnetoresistive elements 2a and 2b, and another magnetic sensor 3 is constituted by the magnetoresistive elements 3a and 3b.
[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 It is set to １ ／ of the pitch interval of the teeth 21.
[0018]
The magnetoresistive elements 2a to 3b are formed by providing a compound semiconductor such as InSb, InAs, or GaAs in a thin film on the nonmagnetic substrate 10 by a vapor deposition method, a sputtering method, or the like. , NiCr, Au, Ag, Cu, Al, etc. are formed at a predetermined pitch by a method such as an evaporation method or a sputtering method. Alternatively, the magnetoresistive pattern may be one in which a metal film such as In, TiAl, NiCr, Au, Ag, Cu, or 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 a substrate obtained by forming an InSb film or the like on an insulating 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 from an insulating substrate such as glass or alumina. For example, a composite substrate that is attached to the upper surface with an adhesive is used. In the conventional case, a magnetic substrate is usually used to concentrate the bias magnetic field of the magnet 13 on the substrate. However, in the case of the present invention, when the bias magnetic field of the magnet 13 is concentrated, the rotation detection signal is reduced. Not used because waveform distortion increases.
[0020]
The surface (back surface) of the nonmagnetic substrate 10 opposite to the surface on which the magnetoresistive elements 2a to 3b are mounted is adhered to the magnet 13 with an adhesive. This magnet 13 may be a permanent magnet or an electromagnet.
[0021]
After the magnet 13 is mounted on the holder 14, it is stored in the non-magnetic protective case 16. For the holder 14, 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 is used. Each of the four lead terminals 18a to 18d is inserted into a through hole 14a provided in the holder 14. The head 19 of each of the lead terminals 18a to 18d and the magnetoresistive elements 2a to 3b are connected via a wire 17 (or a lead frame).
[0022]
Thereafter, a molten resin is injected from the opening of the non-magnetic protective case 16 to form the cast resin 15. As the casting resin 15, an epoxy resin or the like having excellent moisture resistance and relatively high mechanical strength is used. The non-magnetic protective case 16 is made of a non-magnetic material such as beryllium copper, phosphor bronze, brass, nickel silver, non-magnetic stainless steel, aluminum, ceramic, and resin.
[0023]
The gear 20 faces the sensor main 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 operation and effect of the rotating magnetic sensor having the above configuration will be described. FIG. 3 is an electric circuit diagram of the rotating magnetic sensor. The magnetoresistive elements 2a to 3b are connected in series and parallel between the power supply lead terminal 18a and the ground lead terminal 18d.
[0025]
The magnetic flux from the N pole of the magnet 13 returns to the S pole of the magnet 13 via the gear 20. At this time, the magnetic flux emitted from the N pole of the magnet 13 is concentrated on the teeth 21 of the gear 20 that are closest to the N pole of the magnet 13. Therefore, 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 passing through the magnetoresistive elements 2 a to 3 b changes with the movement of the teeth 21 of the gear 20. The resistance values of the magnetoresistive elements 2a to 3b increase as the transmitted magnetic flux increases. Therefore, the resistance value of each of the magnetoresistive elements 2a to 3b changes due to the change of the magnetic flux.
[0026]
When the respective resistance values of the magnetoresistive elements 2a to 3b change with the movement of the teeth 21 of the gear 20, sinusoidal 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 an ideal sine wave as shown by a dotted line in FIG. 7, it becomes difficult to accurately detect an 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 determined based on the time when the teeth 21 of the gear 20 are arranged at positions closest to the magnetoresistive elements 2a to 3b. Are 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, the strength of the magnetic field is inversely proportional to the square of the distance, so that the farther the distance R to the gear 20, the weaker the magnetic field. Therefore, a difference is previously made in the magnetic flux density so as to cancel the change in the magnetic field strength due to the distance.
[0030]
Thereby, when the gear 20 rotates and the teeth 21 of the gear 20 are arranged at positions 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. It comes to be applied with intensity. As a result, rotation detection signals S1 and S2 with small waveform distortion can be obtained.
[0031]
Note that the distance R does not mean the distance from the actual gear 20 to the magnetoelectric conversion elements 2a to 3b, and the teeth 21 of the gear 20 are arranged at positions closest to the respective magnetoelectric conversion elements 2a to 3b. It means the distance at the time (the shortest distance). Therefore, more specifically, the distance R is the distance between the virtual line L connecting the tops of the teeth 21 of the gear 20 and each of the magnetoelectric conversion elements 2a to 3b. Further, since the resistance of the magnetoelectric conversion elements 2a to 3b changes due to 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]
Furthermore, since 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, the space between the gear 20 and the magnet 13 is uniform. And 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, one end of a rectangular ferromagnetic material which is a raw material of the magnet 13 is attached to one end of a magnetizing yoke 32 of a magnetizing device. Are brought into surface contact, a current is passed through the magnetizing coil 31 to generate a magnetic field, thereby magnetizing the ferromagnetic material. At this time, a so-called arc-shaped magnetizing method is adopted in which the number of turns of the magnetized coil 31 at the center of the magnetized yoke 32 is minimized, and the number of turns is increased toward the outside. FIG. 5 is a view of the magnet 13 as viewed from the short side.
[0034]
Further, since the magnetoresistive elements 2a to 3b of the two-phase rotating magnetic sensor of the present embodiment may be formed on the plane of the non-magnetic substrate 10, a normal pattern manufacturing technique can be used, and the yield is good.
[0035]
It should be noted that the rotating magnetic sensor according to the present invention is not limited to the above embodiment, but 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, a 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 clear from the above description, according to the present invention, the magnets are magnetized so that the magnetic field from the magnets is applied to each of the magneto-electric conversion elements with the same intensity. Even when formed, a uniform magnetic bias is applied to each of the magnetoelectric conversion elements, and a rotation detection signal with small waveform distortion is obtained. As a result, the rotational position and speed of a machine tool, an automobile, or the like can be accurately detected.
[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 cross-sectional view showing one embodiment of a rotating magnetic sensor according to the present invention.
FIG. 3 is an electric circuit diagram of the rotating magnetic sensor shown in FIG. 2;
FIG. 4 is a graph showing a magnetic flux density distribution of the magnet shown in FIG. 2;
FIG. 5 is a sectional view for explaining a method of magnetizing the magnet shown in FIG. 2;
FIG. 6 is an enlarged view showing a part of a magneto-electric conversion element and a gear as an object to be detected.
FIG. 7 is a graph showing a waveform of a rotation detection signal.
FIG. 8 is an enlarged view showing a part of a magnetoelectric conversion element and a gear as an object to be detected.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sensor main body 2, 3 ... Magnetic sensor 2a, 2b, 3a, 3b ... Magnetic resistance element 10 ... Non-magnetic substrate 13 ... Magnet 20 ... Gear

Claims (3)

A non-magnetic substrate having a plurality of magneto-electric conversion elements provided on a surface thereof,
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,
A rotation magnetic sensor that detects a rotation state of the rotator by a rotation detection signal output from the magnetoelectric conversion element,
When the rotating body is arranged at a position closest to the magnetoelectric conversion element by the rotation of the rotating body, the magnet is applied so that a magnetic field from the magnet is applied with equal intensity to each of the magnetoelectric conversion elements. Is magnetized,
A rotary magnetic sensor characterized by the above-mentioned. A non-magnetic substrate having a plurality of magneto-electric conversion elements provided on a surface thereof,
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,
A rotation magnetic sensor that detects a rotation state of the rotator by a rotation detection signal output from the magnetoelectric conversion element,
Due to the rotation of the rotator, the magnetic flux density distribution on the surface of the magnet is changed from each of the magneto-electric conversion elements to the non-magnetic based on when the rotator is arranged at the position closest to the magneto-electric 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;
A rotary magnetic sensor characterized by the above-mentioned. 3. The rotating magnetic sensor according to claim 1, wherein the rotation detection signal is at least two signals having different phases.

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