JPH02130419A - Manufacture of magnetic scale - Google Patents

Abstract

PURPOSE:To achieve a higher accuracy of a magnetization pattern at a magnetic scale by irradiating a surface of a magnetizing magnetic material with a laser beam at a specified interval to make a magnetic field leak at a point affected with thermal demagnetization thereof. CONSTITUTION:C-type magnetic head 2 is arranged facing near to a magnetic body 1. Current is supplied to the magnetic heads 2 with a gradual increase thereof in a fixed direction turning the magnetic body 1 and then, done with a gradual decrease thereof to magnetize a surface part of the magnetic body 1 circumferentially. Then, the magnetic body 1 is mounted on a rotating shaft of the motor 3 and the surface of the magnetic body 1 is irradiated with a laser beam through a condenser lens 5 from a laser oscillator 4 of YAG, Co2 or the like to demagnetize a magnetized part of the surface of the magnetic body 1. The entire surface of the magnetic body 1 is irradiated with the laser beam at a specified interval to form a specified demagnetization pattern. This causes a leak magnetic field from the part demagnetized to form a specified magnetic pattern on the surface of the magnetic body 1 thereby producing a magnetic scale.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is a linear or rotary magnetic encoder that is used in a linear or rotary magnetic encoder to generate magnetic changes according to rotational speed, position, etc. The present invention relates to a method for manufacturing a magnetic scale.

"Prior Art" In recent years, linear or rotary magnetic encoders are required to be small and have high resolution, and there is a strong demand for improved accuracy of the magnetization pattern of the magnetic scale used therein.

Conventionally, a magnetic scale is magnetized by placing a magnetic head facing a recording magnetic medium. In the case of this magnetization, if the magnetic head is brought into contact with the recording magnetic medium, sufficient magnetizing magnetic field strength can be obtained, but mechanical vibrations caused by unevenness on the surface of the recording magnetic medium may affect the recording pitch. Errors tend to occur, and in mass production, the magnetic head wears out and changes in characteristics.

Furthermore, if a small gap is provided between the magnetic head and the recording magnetic medium for magnetization, the strength of the magnetizing magnetic field decreases a little, but since the magnetization does not vibrate as described above, the magnetization precision can be improved. Therefore, when high recording accuracy is required, this method is used for magnetization.

The non-contact magnetization method involves heat-treating the recording magnetic medium in a magnetic field to impart a predetermined magnetic anisotropy, and then spot-irradiating a predetermined portion of the recording magnetic medium with a laser beam to heat it above the Curie temperature. A predetermined non-magnetic pattern is formed. Then, by applying a magnetic field to the entire recording magnetic medium,
A magnetization method is known in which a pattern of strong and weak magnetization is created on the surface of a recording magnetic medium (Japanese Unexamined Patent Publication No. 129-1298).
Publication No. 704).

Another known method is to manufacture a magnetic scale by creating a recording magnetic medium from graphite, irradiating the recording magnetic medium with a laser beam to form recesses in a predetermined pattern, and fixing a magnetic material to the recesses (especially Kaisho 62-25900
Publication No. 1).

[Problem to be solved by the invention] Conventionally, a magnetized pattern is created using a laser beam in order to improve the accuracy of the magnetized pattern of a magnetic scale. A magnetic field is applied to the entire surface to form areas of strong and weak magnetization.
The production efficiency is low due to the large number of manufacturing steps, and since the magnetization pattern is created using differences in the strength of magnetization, the clarity of magnetic changes is reduced. Furthermore, the method of forming recesses in a recording magnetic medium using a laser beam and fixing magnetic material to the recesses has low production efficiency, and also makes it difficult to fix the magnetic material with high precision, resulting in errors. Easy to occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve the accuracy of the magnetized pattern of a magnetic scale, and to also improve production efficiency.

"Means for Solving the Problems" The method for manufacturing a magnetic scale of the present invention is carried out through the following steps.

First, the surface of the magnetic material, which is the main body of the magnetic scale, is magnetized in a certain direction.The surface of the zero-order magnetized magnetic material is thermally demagnetized or demagnetized using a laser beam at predetermined intervals. A predetermined magnetic pattern was formed by leaking a magnetic field from the demagnetized locations.

The method of first magnetizing the surface of a magnetic material is to place a C-type magnetic head close to the surface of the magnetic material and face it, and then supply current to the C-type magnetic head while rotating or linearly moving the magnetic material. It is done by changing.

"Function" In the magnetic scale manufacturing method of the above means, when the surface of the magnetic material is magnetized, if the magnetic material is disk-shaped, the surface layer portion will be magnetized in the circumferential direction, and if the magnetic material is strip-shaped, the surface layer will be magnetized in the circumferential direction. The surface layer is magnetized in the longitudinal direction and forms an apparent closed magnetic circuit within the range of use, so no magnetic poles are formed on the surface. However, when it is demagnetized or demagnetized by a laser beam, the demagnetized or demagnetized area A leakage magnetic field is generated, resulting in a magnetic scale having a predetermined magnetic pattern.

Since the magnetic pattern of the magnetic material is formed without contact with a laser beam, its accuracy is high, and production efficiency can be improved because the magnetic material that has been magnetized in advance is simply demagnetized or demagnetized with the laser beam.

"Example" An embodiment of the present invention will be explained with reference to FIG. 1.2.

The magnetic body 1 serving as the main body of the magnetic scale is formed into a disk shape, and the surface or the entirety thereof is made of a magnetic material. As the magnetic material, hard magnets and semi-hard magnets are arbitrarily selected and used, for example, C.

rI Few Os type, Ba ferrite type, SmCo type, FeCrCo type, NaFeB type, and other magnetic materials can be used, and these magnetic powders may be mixed and fixed in a binder such as epoxy resin.

First, as shown in FIG. 2, a C-shaped magnetic head 2 is placed close to and facing the magnetic body 1, and a current is gradually applied to the magnetic head 2 in a fixed direction while rotating the magnetic body 1. The current is increased and supplied, and then the current is gradually decreased and supplied to magnetize the surface portion of the magnetic body I in the circumferential direction. In this case, the magnetic material L apparently forms a closed magnetic path, so no magnetic poles appear on its surface.Also, even when the magnetic material L is formed into a strip, when its surface is magnetized, the surface of the magnetic material It is magnetized in the long plane direction, and also forms an apparent earthen floor magnetic path. Note that the magnetization of the magnetic material I is not limited to the method described above, and if it is desired to obtain a magnetic pattern having axial magnetic poles as a magnetic scale, it may be magnetized in the axial direction.

Next, as shown in FIG. 1, the magnetic body 1 is attached to the rotating shaft of the motor 3, and a laser oscillator 4 such as YAG or CO□ irradiates the surface of the magnetic body 1 with a laser beam through a condenser lens 5.
The surface magnetized portion of the magnetic body 1 is thermally demagnetized or demagnetized. In this case, the rotation of the motor 3 and the generation of the laser beam from the laser oscillator 4 are controlled to be synchronized by the control device 6, and the surface of the magnetic body 1 is irradiated with the laser beam in pulses at predetermined intervals. When a laser beam is irradiated on the entire surface of the EFi magnetic material at predetermined intervals to form a predetermined demagnetization or demagnetization pattern, a leakage magnetic field is generated from the demagnetized or demagnetized portion, and the la magnetic material surface A predetermined magnetic pattern is formed and becomes a magnetic scale.

When using the magnetic scale manufactured as described above in a magnetic encoder, a magnetic sensor such as a Hall element or a magnetoresistive element is placed opposite the magnetic scale to detect magnetic changes in the magnetic scale. Rotation speed and position can be measured.

"Effects of the Invention" According to the method for manufacturing a magnetic scale of the present invention, a magnetic pattern is formed on the surface of the magnetic material that forms the main body of the magnetic scale using a laser beam, so a highly accurate magnetic scale can be manufactured. In addition, the manufacturing process is very efficient, as the magnetic material is first magnetized in a certain direction, and then the surface of the magnetic material is irradiated with a laser beam to demagnetize or demagnetize. A magnetic scale with high resolution can be obtained since the magnetic scale and the demagnetizing part or the demagnetizing part are provided alternately.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a demagnetizing step in the method for manufacturing a magnetic scale of the present invention, and FIG. 2 is an explanatory diagram showing a magnetizing step of a magnetic body. 1: Magnetic material 2: Magnetic head

Claims (2)

[Claims] (1) The surface of the magnetic material that forms the main body of the magnetic scale is magnetized in a certain direction in advance, and the surface of the magnetized magnetic material is irradiated with a laser beam at predetermined intervals to thermally demagnetize or demagnetize it. A method for manufacturing a magnetic scale, comprising forming a predetermined magnetic pattern by leaking a magnetic field from a demagnetized portion. (2) Claim (1) wherein a C-type magnetic head is placed opposite to the surface of the magnetic body, and the current supplied to the C-type magnetic head is changed while moving the magnetic body to magnetize the surface of the magnetic body.
A method of manufacturing a magnetic scale.