JPH0572304A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To obtain a displacement from an extremely low speed to a high speed by extracting magnetization characteristics of a magnetic fiber positively or a magnetic sensor which is extremely effective for a rotary measurement by using first and second coils where a magnetic material and a material with a high permeability which cause a rapid inversion of magnetization at a position of coercive force for a core. CONSTITUTION:A first coil 13a is wound around a core 12a of an amorphous magnetic fiber where a rapid inversion of magnetization occurs at a position of a coercive force and a second coil 13b is wound around a core 12b of the highpermeability type amorphous fiber and these two elements are held by a member 16 which is made of a high-permeability material and is sealed, thus enabling a magnetic sensor 11 to be produced. The coils 13a and 13b are connected in series and a magnetic rotor 14 is placed opposite to the sensor 11 and then an output of the sensor 11 when the rotar 14 is rotated is measured, thus enabling a pulse 15a to be generated at a low-speed region and a sinusoidal wave 15b to be generated at a high-speed region so that a displacement or a rotation fully covering low to high speed where an output can be obtained can be measured in both cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention takes out the magnetization change of a magnetic core magnetized by an external magnetic field as a terminal voltage of a coil wound around the magnetic core, thereby displacing a magnetic field generator that causes the magnetic change of the magnetic core. The present invention relates to a magnetic sensor that detects the number of rotations.

[0002]

2. Description of the Related Art A magnetic sensor is one of the sensors that occupies an important position for detecting a position or the number of revolutions. As shown in FIG. 7A, a coil 3 wound around a magnetic core 2 is externally connected. The magnetic field 4 is moved in the direction of, for example, an arrow A in a state of being close to the magnetic field 4 to generate a pulse 5 as shown in FIG. 8 (b) in the coil 3, and as shown in FIG. Amorphous metal magnetic fiber that causes a large magnetization reversal
In the one used in, the number of rotations and the like is detected by counting the number of voltage pulses generated in the coil 3. Generally, there is also a magnetic sensor 1'where a coil 3 is wound around a magnetic core 2'as shown in FIG. 10 (a) by using a high magnetic permeability material as shown in FIG.

In order to generate a large pulse voltage in response to a weak and inhomogeneous magnetic field, a Wiegand wire in which an outer skin portion having a high coercive force characteristic and a core portion having a high magnetic permeability characteristic are formed of an integral material is used. A magnetic sensor has been invented, and in JP-A-56-72368, a Wiegand wire is provided with a coil for resetting the magnetization direction, and local reversal is caused to enable reversal even in a weak magnetic field. It is shown. Also, JP-A-64-35283
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a structure in which a plurality of Wiegand wires are bundled and a plurality of pulses generated in a coil are superposed and filtered to counter noise.

[0004]

The magnetic sensor 1 shown in FIG. 7 (a) follows a low-speed magnetic field change, but attempts to measure a high-speed changing displacement or a high-speed rotation speed.
There is a limit to the magnetization reversal speed of the magnetic core 2, 100 Hz
If the value exceeds the value, the number of voltage pulses cannot be accurately counted. For example, as shown in FIG. 7A, the Fe-Si-B is separated from the magnet rotor 4 forming the external magnetic field with a gap of 5 mm.
An amorphous fiber having a diameter of 100 μm and a length of 10 mm is used as the magnetic core 2, and a conductive wire coil having a diameter of 50 μm is provided around the magnetic core 2.
The magnetic sensor 1 wound 00 times has a problem in that only a weak output of approximately 5 mV or less can be obtained, which makes it impossible to detect the rotation speed.

On the other hand, as shown in FIG. 9, when a magnetic core is formed by using a Co--Fe--Si--B type amorphous high-permeability material through which a magnetic flux easily passes, and a coil is wound to change the external magnetic field H. , The magnetic flux density B in the material changes according to the change,
Unlike the material in which the magnetization reversal abruptly occurs at the position of the coercive force Hc, it does not show a steep change characteristic, and therefore, even if the external magnetic field H is changed, a pulsed output is not generated. That is, FIG.
The magnetic sensor 1'shown in (a) merely obtains an output of a sine wave 5'having a small amplitude as shown in FIG. 9 (b), and the electromotive force due to the interlinkage magnetic flux is generated by the law of electromagnetic induction. , E = −n (dφ / dt) (n is the number of turns of the coil,
Since dφ / dt is the magnetic flux change speed), there is a problem that the output hardly appears in the low speed region where the change of the external magnetic field H is gentle.

In view of the above problems, the present invention eliminates the use of a double-structured material such as Wiegand wire,
An object of the present invention is to provide a magnetic sensor capable of measuring displacement or rotation by reliably extracting the magnetization reversal characteristic of magnetic fiber and obtaining a stable output against changes in the external magnetic field from extremely low speed to high speed. is there.

[0007]

Means for solving the above problems are set forth in the appended claims. That is, an object of the present invention is to provide a magnetic sensor, which is composed of a magnetic core and a coil, for detecting a change in an external magnetic field as a terminal voltage of the coil. A magnetic sensor having a first coil and a second coil wound around a magnetic core made of a high-permeability material, and having a magnetic circuit in which the first coil and the second coil are connected in series. Or a first coil wound around a magnetic core made of a magnetic material that causes a rapid magnetization reversal at the position of the coercive force, and a second coil having no magnetic core, and the first coil and the second coil are provided. This is achieved by a magnetic sensor having a magnetic circuit in which coils are differentially connected.

[0008]

With the above structure, in the low speed range, a pulsed output from the first coil is obtained, while in the high speed range, a sine wave output from the second coil is obtained. A magnetic sensor that exhibits stable output with respect to changes in the external magnetic field is realized. That is, the inventors have found that the reason why the voltage level rises when the rate of change of the external magnetic field becomes high is that the coil wound around the magnetic fiber catches not only the change in the magnetization of the magnetic fiber but also the change in the external magnetic field itself. Also in the case of e = -n
The focus is on the fact that an electromotive force of (dφ / dt) is generated, and therefore the electromotive force of the coil increases as the changing speed of the magnetic field increases.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> A first embodiment of the magnetic sensor of the present invention is shown in FIG.
Shown in. Fe-Si-B system diameter 100 μm, length 10 m
m, a so-called pulse-generating amorphous magnetic fiber in which a rapid magnetization reversal occurs at the position of the coercive force, is used as the magnetic core 12a, and the first coil 13a having a wire diameter of 50 μm is formed around the magnetic core 12a.
I prepared the wound one. Next, a high permeability magnetic fiber of Co-Fe-Si-B system having a diameter of 100 μm and a length of 10 mm was used as a magnetic core 12b, and a second core having a wire diameter of 50 μm was formed around the magnetic core 12b.
The coil 13b was prepared by winding 1000 times.

Next, as shown in FIG. 1, these two elements were sandwiched and fixed by a member 16 of Fe--Ni type high magnetic permeability material to form a magnetic sensor 11. At this time, the coils 13a and 13b were connected in series so that the directions of the magnetic fields generated by the wound first and second coils 13a and 13b were the same. 5 mm in thickness and 4 in diameter facing the magnetic sensor 11.
The magnet rotor 14 magnetized with 60 poles was arranged on the outer periphery of an 8 mm disk with a gap of 5 mm, and the output of the magnetic sensor 11 when the magnet rotor 14 was rotated was measured.

As a result, the pulse 15a as shown in FIG.
In the high speed range over 00 Hz, a sine wave 15b as shown in FIG. 3 was generated. In each case, 60 pulses per one rotation of the magnet rotor 4 and an output exceeding 300 mV were obtained, and it was confirmed that displacement or rotation measurement capable of sufficiently covering from low speed to high speed was possible. In the case of the magnetic sensor 11 of the present embodiment, the one magnetic core 12a is not limited to amorphous as long as it is a material in which magnetization reversal rapidly occurs at the coercive force position, and crystalline, metal, or alloy may be applied. However, the other magnetic core 12b is not limited to an amorphous material, and any material having a high magnetic permeability can be applied.

<Second Embodiment> As shown in FIG.
An element in which a first coil 23a having a diameter of 50 μm is wound 1000 times around a magnetic core 22a of an amorphous magnetic fiber having a length of 30 mm and a diameter of 70 μm of Si-B system, and the element having a length of 30 mm and a diameter of 7 mm
Elements in which a second coil 23b having a diameter of 50 μm is wound 1000 times around a nylon fiber 22b having a diameter of 0 μm are bundled and fixed with silicon rubber 26 to be integrated. Then, by the magnetic field, the first
So that the directions of the magnetic fields generated by the second coil 23a and the second coil 23a cancel each other.
23b was connected to form the magnetic sensor 21. The "magnetic circuit in which the first coil and the second coil are differentially connected" described in claim 2 means, for example, the first coil 23a shown in this embodiment,
This indicates a circuit configuration connected so that the directions of the magnetic fields generated by the second coil 23b cancel each other out. The core material around which the second coil 23b is wound is not limited to the nylon fiber 22b as in the embodiment, and may be any non-conductive non-magnetic material. Further, after winding, the core material may be removed and used as an air core. It doesn't matter.

With this configuration, the voltage component due to the change in the external magnetic field picked up by the coil itself is eliminated as shown in FIG.
Only the pulse voltage component due to the magnetization reversal of the magnetic fiber can be extracted. Fig. 4 shows 3 with φ90mm and width 10mm.
FIG. 7 is a view in which a magnet rotor 24 magnetized with 0 poles and the magnetic sensor 21 are arranged to face each other with a gap of 5 mm therebetween.
Is a magnetic sensor 2 obtained by rotating the magnet rotor 24.
It is a figure showing the output voltage of No. 1 and the magnetic field change speed 10Hz.
It is shown that a high output can be stably obtained in each speed range from 1 to 1000 Hz.

Further, by appropriately selecting the distance between the first coil and the second coil, it is possible to stably take out a high-output signal even when facing the magnetic field generating means having a narrow magnetic pole magnetizing interval. Is.

[0015]

As shown in the above embodiments, the present invention is a magnetic sensor comprising a magnetic core and a coil for detecting a change in an external magnetic field as a coil terminal voltage, which has a double structure such as a Wiegand wire. It is possible to accurately detect a weak magnetic field change without using a material, reliably draw out the magnetization reversal characteristic of the magnetic fiber, and provide a magnetic sensor extremely effective for displacement or rotation measurement from extremely low speed to high speed.

[Brief description of drawings]

FIG. 1 is a schematic layout diagram of a first embodiment of a magnetic sensor according to the present invention.

FIG. 2 is an output characteristic diagram of the first embodiment.

FIG. 3 is an output characteristic diagram of the first embodiment.

FIG. 4 is an arrangement schematic diagram of a second embodiment of the magnetic sensor according to the present invention.

FIG. 5 is an output characteristic diagram of the second embodiment.

FIG. 6 is a magnetic field change detection characteristic diagram of the magnetic sensor of the second embodiment.

FIG. 7 is a schematic layout diagram and an output characteristic diagram of a conventional magnetic sensor.

FIG. 8 is a magnetization characteristic diagram of a magnetization reversal type magnetic material at the position of coercive force.

FIG. 9 is a magnetization characteristic diagram of a high magnetic permeability material.

FIG. 10 is a schematic layout diagram and output characteristic diagram of a conventional magnetic sensor.

[Explanation of reference numerals] 1, 11, 21 Magnetic sensor 12a, 22a Magnetic core 12b of material in which rapid magnetic reversal occurs 12b Magnetic core of high magnetic permeability material 22b Nylon fiber 13a, 23a First coil 13b, 23b Second coil 4, 14, 24 Magnet rotor 5, 15, 25 Pulse 16 High permeability member 26 Silicon rubber

Claims (2)

[Claims] 1. A magnetic sensor comprising a magnetic core and a coil for detecting a change in an external magnetic field as a change in a terminal voltage of the coil, the magnetic sensor being wound around a magnetic core which causes a rapid magnetization reversal at a coercive force position. It has a first coil and a second coil wound around a magnetic core made of a high magnetic permeability material, and has a magnetic circuit in which the first coil and the second coil are connected in series. Magnetic sensor to do. 2. A magnetic sensor comprising a magnetic core and a coil for detecting a change in an external magnetic field as a change in the terminal voltage of the coil, the magnetic sensor being wound around a magnetic core which causes a rapid magnetization reversal at a coercive force position. A magnetic sensor comprising: a first coil; a second coil having no magnetic core; and a magnetic circuit differentially connecting the first coil and the second coil.