JP2982468B2 - Magnetized body and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetized body of a magnetic linear encoder used as a linear position sensor for accurately detecting, for example, the position of a lens of an autofocus camera in units of microns, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A linear position sensor detects the position of a movable part of a machine, and is also called a linear sensor. This linear sensor is used to control the lens position of an autofocus camera, industrial machines such as feed axes of machine tools, XY tables, and assembly robots, and OA such as recorders, plotters, and magnetic disks.
Widely used for equipment. The detection principle of a linear sensor can be roughly classified into two types, a digital type and an analog type. The digital linear sensor reads a regular pattern recorded on a scale and outputs a position signal. Further, digital linear sensors can be classified into three types: an optical type, a magnetic type, and an electromagnetic induction type based on the principle of recording and reading scale patterns.

[0003] A magnetic linear position sensor, which is one of the typical digital types, is also called a magnetic linear encoder. This magnetic linear encoder is manufactured as follows. First, the coercive force (coercivity) H _c, the residual stress B _r, is ferromagnetic or plastic magnet such as squareness ratio R are both large FeCo and NiCo, is applied or plated on the surface of the flat substrate, 10 A magnetic film having a thickness of 15 μm is formed on the surface of the flat substrate. Next, a scale (magnetized body) is formed by magnetizing the magnetic film at a constant interval. A magnetic flux response type magnetic head is used for reading the magnetic pole of the magnetized body.

Meanwhile, a method of manufacturing a magnetized body has conventionally been performed using a pulse magnetizing method or the like. The pulse magnetization method is
This is a method performed by a magnetizing jig having an iron rod whose tip is processed into a protruding shape, and a coil wound around the iron rod. For example, an iron bar is held close to and above a magnetic film deposited to a uniform thickness over the entire upper surface of the base, and a pulse current is applied to the coil. As a result, a portion of the magnetic film, that is, a portion close to the rod, has a surface, for example, of N
The poles are magnetized. Further, the rod is moved to a position away from the magnetized portion by a predetermined distance to supply a pulse current. As a result, the portion of the magnetic film adjacent to the N-pole magnetized portion is magnetized so that its surface becomes the S-pole. By repeating this operation at regular intervals on the magnetic film, the magnetic film is alternately magnetized at regular intervals.

[0005]

However, in the conventional method for manufacturing a magnetized body using the pulse magnetizing method, the radius of curvature of the projection at the tip of the iron rod of the magnetizing jig is 100 μm.
It could only be processed to the finest degree. As a result, there is a problem that the magnetic film can be magnetized only up to the interval of the magnetization width of 200 μm.

Accordingly, the present invention is not affected by the processing accuracy of the iron rod of the magnetizing jig, and it is possible to increase the position resolution as, for example, a magnetic linear encoder by making the magnetizing width smaller than that. It is an object of the present invention to provide a magnetized body that can be manufactured and a manufacturing method thereof.

[0007]

According to a first aspect of the present invention, there is provided a magnetized body in which a magnetized portion is discontinuously located on a base made of a non-magnetic material.

In the method for manufacturing a magnetized body according to a second aspect of the present invention, a discontinuous magnetic body is formed on a base made of a non-magnetic material, and the magnetized jig is moved closer to form the discontinuous magnetic body. It is magnetized.

[0009]

In the magnetized body and the method of manufacturing the same, the magnetic body is divided into a discontinuous film, for example, the magnetic film is divided into a plurality of portions, and the non-magnetic portion is interposed between the divided portions. Exists. Therefore, when a part of the magnetic film is magnetized, it does not magnetize to an adjacent film part. Therefore, the magnetization width can be reduced by reducing the interval between the divided portions of the magnetic film.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a magnetized body and a method of manufacturing the same according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view schematically showing an apparatus for manufacturing a magnetized body according to one embodiment of the present invention.

First, as shown in FIG. 1, a silicon wafer 1 having a plurality of grooves formed on its surface is prepared. These grooves are formed to have a width of 50 μm and a depth of 50 μm. The interval between these grooves is 50 μm, and the pitch of the grooves is 100 μm. These grooves may be formed by, for example, an etching method using a well-known resist process, or may be formed by mechanical processing such as cutting. Next, a resist is applied to the upper surface of the silicon wafer 1 (the portion excluding these grooves).
Then, a magnetic film of a plastic magnet is applied to the entire upper surface of the silicon wafer 1 to a predetermined thickness. Then, the magnetic film deposited on the resist is lifted off together with the resist. As a result, the interval between the magnetic films 2 is formed to be 50 μm on the silicon wafer 1, and the magnetic films 2 can be discontinuously applied. This method may be a thick film method such as plating or a thin film method such as an ion plating method.

Next, a magnetizing jig 5 is prepared. The magnetizing jig 5 includes an iron rod 3 having a protrusion at the tip thereof having a radius of curvature of 100 μm, and a coil 4 wound around the iron rod 3 in three turns. Both ends of the coil 4 are connected to a pulse generating power supply (not shown). Then, the magnetizing jig 5 is moved above the silicon wafer 1 and is positioned above each magnetic film 2 with a predetermined distance therebetween so that the magnetizing directions of the magnetic films 2 alternately change. Then, a pulse current of a pulse generating power supply is supplied to the coil 4. As a result, each magnetic film 2 has 100
It can be magnetized at intervals of μm. Arrows in the figure indicate the directions of magnetic lines of force from the north pole to the south pole. This is because, since each magnetic film 2 is formed as a discontinuous film, when one magnetic film 2 is magnetized, the adjacent magnetic film is hardly affected by the magnetization. The magnetic film may be magnetized by a magnetizing jig using a permanent magnet.

The magnetized body thus manufactured is used, for example, for a magnetic linear encoder. In the magnetic linear encoder, the magnetic pole of the magnetized body is read by a read head. This read head has M
An array of R elements (magnetic resistance elements) is used.
The MR element can read its position even when the lens of the autofocus camera is stationary.

Next, the position signal read by the MR element is subjected to an interpolation process capable of obtaining a resolution higher than the pitch of 100 μm of the magnetized body of each magnetic film 2. This interpolation processing is performed by processing the position signal by a digital circuit. More specifically, a signal of a constant frequency is given to the MR element, the position information is converted into phase information by utilizing the fact that the frequency of the signal changes depending on the position, and the converted value is digitally divided. In this embodiment, since the magnetization pitch is set to half of the conventional pitch, the position resolution can be further improved.

In forming the magnetic film on the surface of the silicon wafer, the magnetic film 6 may be formed on a portion other than the groove of the silicon wafer 1 as shown in FIG. Or
As shown in FIG. 3, the magnetic films 8 may be formed on the upper surface of the silicon wafer 7 at equal intervals without forming a groove on the upper surface of the silicon wafer 7. Furthermore, if the radius of curvature of the protruding portion of the iron bar can be reduced to less than 100 μm, a higher positional resolution can be obtained by shortening the pitch of the discontinuous magnetic film accordingly. The pitch of the discontinuous magnetic film is shortened, and the thickness (groove depth) of the magnetic film is increased, so that the magnetic field generated by the magnetized body is increased in the same manner as when the width of the magnetized body is increased. In addition to maintaining strength, it is also possible to reduce the influence of an external magnetic field.

Similarly, a rotary drum of a magnetic rotary encoder can also produce a scale (magnetized body) that is discontinuously magnetized on the outer periphery of a disk-shaped substrate, as shown in FIG. As a result, the resolution of the magnetic rotary encoder can be increased. Further, the present invention can be applied to a rotor of a step motor and applied to a micro motor.

Further, the magnetized body of the present invention can be formed in a portion other than the device forming region of the silicon wafer for manufacturing an VLSI. By using the magnetized body at this time as an alignment mark used in a lithography process such as light, X-ray, electron beam, or ion beam, the mark can be measured magnetically.

[0018]

As described above, according to the magnetized body and the method of manufacturing the same according to the present invention, the magnetized width can be further reduced without being affected by the processing accuracy of the iron rod of the magnetized jig. Thereby, for example, the position resolution as a magnetic linear encoder can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a magnetized body manufacturing apparatus according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a step of forming a magnetic body according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a step of forming a magnetic body according to one embodiment of the present invention.

FIG. 4 is a perspective view showing a magnetized body of a rotary drum of the magnetic rotary encoder according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Magnetic film 3 Iron rod 4 Coil 5 Magnetization jig

Claims (2)

(57) [Claims] 1. A magnetized body characterized in that a magnetized portion is discontinuously located on a base made of a nonmagnetic material. 2. A method for manufacturing a magnetized body, comprising forming a discontinuous magnetic body on a substrate made of a nonmagnetic material, and magnetizing the magnetic body by approaching a magnetizing jig.