JPH10325738A - Magnetization method - Google Patents

Abstract

(57) [Problem] To provide a method of forming a magnetic pattern by irradiating a laser beam and heating it to a temperature higher than the Curie point, thereby forming a high-precision magnetic pattern without breaking the shape of a magnetic material. . SOLUTION: A sintered magnet encoder plate 1 is irradiated with a laser 4 and partially heated to a Curie point or higher to form a magnetic pattern, thereby forming a high-precision magnetic pattern without losing its shape. can do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetizing method for forming a magnetized portion of a motor.

[0002]

2. Description of the Related Art In recent years, as control motors have become smaller and more precise, there has been a demand for improved resolution of encoders used for speed and position detection. In particular, there is an increasing demand for high-resolution magnetic encoders that are resistant to shocks and low in cost. In addition, it is required to develop the magnetic pattern forming method of the magnetic encoder to magnetize a driving magnet of a micro motor.

Conventionally, a method for forming a magnetic pattern of a magnetic encoder is disclosed in Japanese Patent Application Laid-Open No. 7-239246.

FIG. 3 shows the structure of a magnetic encoder. The magnetic encoder includes an encoder plate 31 on which a magnetic pattern is formed at a pitch 33 and a magnetoelectric conversion element 32.

FIG. 4 shows a conventional method of forming a magnetic pattern on the encoder plate. Reference numeral 41 denotes an encoder plate coated with a resin magnetic material on the outer periphery of which the entire outer periphery is previously magnetized to the N pole (or S pole), and 2 denotes an encoder plate 1 which is magnetized to the polarity opposite to the N pole (or S pole). An external magnetic field generator for generating a possible DC external magnetic field 3, a laser 44 focused on a minute spot, and a rotary device for the encoder plate 41.

Hereinafter, a method for forming a magnetic pattern will be described. First, the entire outer periphery must be N-pole (or S-pole) in advance.
S-pole (or N-pole) by an external magnetic field generator 2 on an encoder plate 41 coated with a resin magnetic material on the outer periphery magnetized on
In the state where the external magnetic field 3 is applied, the laser 44 is irradiated to partially heat the Curie point or higher (several hundred degrees Celsius). As a result, only the heated portion is magnetized to the N-pole (or S-pole), and is magnetized to the S-pole (or N-pole) by the external magnetic field 3.

Next, the encoder plate 41 is rotated by a predetermined amount by the rotating device 5 to irradiate the encoder plate 41 with a laser 44 and similarly magnetize the S pole (or N pole). By repeating the above method, a magnetic pattern is formed on the encoder plate 41.

[0008]

In the conventional method, a material coated with a resinous material is used as a magnetized material for irradiating a laser. In this case, if the resin material is to be heated to a Curie point or higher as shown in the Curie point list in FIG. 5, the melting point of the resin material is about 200 ° C.
Since the shape of the magnetized material collapses, it has been difficult to form a magnetized pattern with high accuracy. In particular, when such a magnetic pattern forming method is used for a magnetic encoder, there is a problem that a magnetic pattern with high accuracy cannot be formed.

Accordingly, an object of the present invention is to provide a magnetizing method capable of forming a highly accurate magnetic pattern.

[0010]

In the magnetizing method of the present invention, a laser is applied to a sintered magnet to which an external magnetic field is applied, and the magnet is partially heated to a temperature above the Curie point to form a magnetic pattern. Even if the temperature rises to the Curie point,
Since the shape of the sintered magnet does not collapse, a highly accurate magnetic pattern can be formed.

Further, since the width of the magnetized portion is determined by the laser diameter, a fine magnetic pattern can be formed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a method for forming a magnetic pattern by irradiating a laser to a sintered magnet on which an external magnetic field is applied so as to partially exceed the Curie point. Even if the temperature rises to the Curie point, the sintered magnet has a melting point of 1000 ° C. or more, so the sintered magnet does not melt and does not lose its shape, so a highly accurate magnetic pattern is formed. can do. further,
According to the method of the present invention, the magnetization width is determined by the laser diameter, so that if the optical system is devised and the laser spot diameter is reduced, a fine magnetic pattern can be formed.

According to a second aspect of the present invention, there is provided a magnetizing method in which a cast magnet on which an external magnetic field is applied is irradiated with a laser to form a magnetic pattern partially at or above the Curie point. Even if the temperature rises to the Curie point, since the melting point of the cast magnet is equal to or higher than the Curie point, the cast magnet does not melt and does not lose its shape, so that it has an effect that a highly accurate magnetic pattern can be formed.

According to a third aspect of the present invention, there is provided the magnetizing method according to the first or second aspect, wherein an external magnetic field having a coercive force or less acts thereon. By focusing on the fact that the magnetic field becomes zero, the external magnetic field is set to a weak magnetic field less than the coercive force, so that the peripheral portion irradiated with the laser is not demagnetized by the external magnetic field and a magnetic pattern with a high SN ratio is formed. It has the effect of being able to.

According to a fourth aspect of the present invention, there is provided the magnetizing method according to the first aspect, wherein a ferrite magnet is used as the sintered magnet. Since the temperature characteristic of the holding force of the ferrite magnet is positive, the Curie point Even after cooling, the magnetized state is maintained at a high temperature up to room temperature without thermal demagnetization even when cooled.
This has the effect that a magnetic pattern having a high ratio can be formed.

According to a fifth aspect of the present invention, there is provided the magnetizing method according to the first or second aspect, wherein an external magnetic field of 500 Oe or more acts.
Although it is about 000 Oe, it has an effect that it becomes possible to perform magnetization by laser irradiation by applying an external magnetic field of 500 Oe or more.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIG. 1, reference numeral 1 denotes an encoder plate made of a sintered magnet material whose outer periphery is magnetized in advance to an N pole (or S pole). And an external magnetic field generator 4 for generating an external magnetic field 3 that can be magnetized in a polarity opposite to that of the YA.
The G laser 5 is a rotating device for the encoder plate 1.

A method for forming the magnetic pattern configured as described above will be described. First, an external magnetic field 3 is applied to the encoder plate 1 by the external magnetic field generator 2 to irradiate the outer peripheral surface of the encoder plate 1 with the YAG laser 3 to partially raise the temperature to the Curie point or higher (several hundred degrees Celsius). Then, only this portion is magnetized to the N pole (or S pole), and the magnetism is extinguished to the S pole (or N pole) by the external magnetic field 3. In this case, since the magnetization width is determined by the laser spot diameter, it is theoretically about the wavelength (for example, YAG
(Laser wavelength: 1.06 μm). If the laser spot diameter is made to correspond to the pitch of the magnetic pattern, the encoder plate 1 is rotated by two pitches by the rotating device 5 to irradiate the encoder plate 1 with the laser 4 and similarly to the S pole (or N pole). Magnetize.

By repeating the above method, fine magnetic patterns at equal intervals can be formed on the encoder plate 1.

(Embodiment 2) In FIG. 2, reference numeral 21 denotes an encoder plate made of a sintered magnet material whose surface is not magnetized.
2 is an external magnetic field generator for generating an external magnetic field 23 whose polarity can be arbitrarily switched between N and S poles on the encoder plate 21, 4 is a YAG laser focused on a minute spot,
Reference numeral 5 denotes a rotation device for the encoder plate 21.

A method of forming the magnetic pattern configured as described above will be described. First, in a state where the encoder plate 1 is stationary, an external magnetic field 23 of the S pole (or N pole) is applied to the encoder plate 21 by the external magnetic field generator 22 to irradiate the YAG laser 3 and partially exceed the Curie point ( By heating to several hundred degrees Celsius), the S pole (or N pole) is magnetized by the external magnetic field 23.

Next, the encoder plate 21 is rotated by a predetermined amount by the rotating device 5, and the external magnetic field 2 is reversed in the direction opposite to the above-described method.
3 and irradiated with the YAG laser 3 in the same manner to heat the Curie point or higher, and the N pole (or S
Pole). By repeating this, a magnetic pattern can be formed on the encoder plate 21.

Although the case where a YAG laser is used as a method for heating a magnetic material to a temperature higher than the Curie point has been described, the same effect can be obtained when a CO2 laser, an excimer laser, a semiconductor laser, or an electron beam is used. Needless to say,

In the above-described embodiment, the method of forming the magnetic pattern of the encoder plate has been described. However, it is needless to say that the same effect can be obtained when the magnetic pattern is similarly formed on the magnetic scale and the motor driving magnet. No.

[0026]

As described above, according to the first and second aspects of the present invention, when forming a magnetic pattern by irradiating a laser to partially exceed the Curie point, even if the temperature rises to the Curie point, Since the shape of the sintered magnet is not lost, an advantageous effect that a highly accurate magnetic pattern can be formed can be obtained.

Further, according to the third aspect of the present invention, a magnetic pattern having a high NS ratio can be formed without demagnetizing a peripheral portion irradiated with a laser by an external magnetic field.

Further, according to the present invention, the magnetic pattern having a high NS ratio is maintained without being thermally demagnetized even when cooled after being magnetized at the Curie point. Can be formed.

[0029] Further, the invention according to claim 5 is 500 Oe
By applying the above external magnetic field, magnetization by laser irradiation is suitable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a method for forming a magnetic pattern according to a first embodiment of the present invention.

FIG. 2 is an explanatory view showing a method of forming a magnetic pattern according to a second embodiment of the present invention.

FIG. 3 is a structural diagram of a magnetic encoder.

FIG. 4 is an explanatory view showing a conventional magnetic pattern forming method.

FIG. 5 is a diagram showing a list of magnet Curie points.

[Explanation of symbols]

 Reference Signs List 1 encoder plate 2 external magnetic field generator 3 external magnetic field 4 YAG laser 5 rotating device 21 encoder plate 22 external magnetic field generator 23 external magnetic field

Claims (8)

[Claims] 1. A magnetizing method for irradiating a sintered magnet on which an external magnetic field is applied with a laser to partially form a magnetic pattern at a Curie point or higher. 2. A magnetizing method in which a cast magnet on which an external magnetic field acts is irradiated with a laser to partially form a magnetic pattern at a Curie point or higher. 3. An external magnetic field having a holding force or less acts on the external magnetic field.
Alternatively, the magnetizing method according to claim 2. 4. The magnetizing method according to claim 1, wherein a ferrite magnet is used as the sintered magnet. 5. The magnetizing method according to claim 1, wherein an external magnetic field of 500 Oe or more acts. 6. A magnetic encoder manufactured by the magnetizing method according to claim 1. 7. A magnetic scale produced by the magnetizing method according to claim 1. 8. A motor manufactured by the magnetizing method according to claim 1.