JPH03225807A - Yoke and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a low-cost yoke excellent in the controllability of an actuator by constituting the yoke so that said yoke is composed of a molded body combining granular magnetic materials and a seizing condition exists between the materials. CONSTITUTION:The title yoke is composed of a molded body made by the combination of granular magnetic materials and a seizing condition exists between the materials. Any magnetic material such as soft magnetic iron, common steel, etc., and iron-nickel alloy, iron-cobalt alloy, etc., can be used as the granular magnetic material. Also, it is possible to use these granular magnetic materials with any shape such as sphere, ellipsoid, cylinder, polygonal pillar and shapes approximating these ones. Further, it is possible to use not only one kind of the granular magnetic materials but also the combination of two kinds or more of these materials and that with linear and plate magnetic materials. Thus, it is possible to obtain a yoke involving no problem in shape, magnetic circuit characteristics and cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a yoke used in a small motor, etc., and a method for manufacturing the same.

[Prior Art] The more magnets are used for the field in a small motor, the more a yoke is used to make the field distribution appropriate.

Recently, with the advancement of OA equipment and FA equipment, the small motors used in these equipment are required to have a structure suitable for the purpose of use, and the yokes used are also becoming smaller and more complicated. There is a growing demand for shapes. In particular, in motors for driving magnetic heads of HDDs and FDDs, and actuators for optical pickups of CDs, etc., miniaturization of the yoke and a yoke shape suitable for an optimum magnetic circuit have become important issues. Controllability is also important for these actuators, and one of the properties required of the yoke is low electrical resistance.

In order to miniaturize the yoke and make it into an arbitrary shape, complicated machining is required. Methods for manufacturing such a yoke include the lost wax method and powder metallurgy, but it is difficult to obtain a yoke with optimal magnetic circuit characteristics at low cost.

On the other hand, one way to obtain an arbitrary shape is to use laminated steel plates, but this requires mechanical strength as the field yoke of the actuator, which poses a problem.

In order to relatively easily provide a yoke with an excellent magnetic circuit and low electrical resistance at low cost, we have developed a method of laminating and baking plate-shaped magnetic materials such as conductive plated silicon steel plates. There is a method of obtaining an arbitrary shape, and a method of obtaining an arbitrary shape by laminating plate-shaped magnetic materials such as conductive plated silicon steel plates and baking them. However, with the yoke obtained by this method, it is difficult to obtain a yoke with a three-dimensionally very complex shape.

In this way, with conventional yokes, the shape, magnetic circuit characteristics,
There are many problems in terms of cost and it is not sufficient.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above, makes it possible to obtain an optimal field magnetic flux distribution by making a magnetic material into an arbitrary shape, and furthermore, it is possible to use this magnetic material. The purpose of this invention was to provide an inexpensive yoke with excellent controllability of an actuator, and a method for manufacturing the same.

[Means for Solving the Problems] The present invention is characterized by: A yoke that is made of a molded body made by combining granular magnetic materials, and is characterized in that the materials are stuck together.

A yoke in which the granular magnetic material has a plating layer of a conductive material.

A method for manufacturing a yoke, which comprises combining granular magnetic materials, forming them into a predetermined shape, and then annealing them under pressure to eliminate seizure between the materials.

A method for manufacturing a yoke in which annealing under pressure is performed in a reducing atmosphere.

A method for manufacturing a yoke in which a granular magnetic material is plated with a conductive material on its surface.

A yoke that is a combination of granular magnetic material, linear magnetic material, and plate-shaped magnetic material.

A method for manufacturing a yoke that is a combination of granular magnetic material, linear magnetic material, and plate-shaped magnetic material.

It is in.

The present invention will be explained in detail below.

First, as the granular magnetic material used in the yoke of the present invention, any magnetic material such as electromagnetic soft iron, common steel, iron-nickel alloy, iron-cobalt alloy, etc. can be used.

The shape of the granular magnetic material is not limited to a sphere, an ellipsoid, a cylinder, a polygonal prism, or anything close to these shapes. Furthermore, the number of types of granular magnetic materials is not limited to one type, but two or more types may be used in combination, or they may be combined with linear magnetic materials or plate-shaped magnetic materials.

After forming the combination, the surface of the granular magnetic material must be clean and free from oil or foreign matter, and the surface roughness must be high in order to sufficiently bake between the materials and create a yoke with high mechanical strength. It is necessary to have a small amount of To clean the surface of granular magnetic material, pickling or oil washing may be performed.

In order to form a yoke made of granular magnetic material into a predetermined shape, molding may be performed if necessary. This molding process is effective in increasing the contact area and increasing the yield rate of magnetic materials in order to sufficiently bake between the materials after combination molding. 6 of the final yoke
In order to increase the performance rate, it is effective to use a combination of granular magnetic materials with different particle sizes.

Annealing is performed at the temperature and time necessary to release the distortion of the molded granular magnetic material combination molded product, and to provide sufficient mechanical strength in a predetermined shape without causing seizure between the materials. must be carried out. In this annealing process, in order for the molded granular magnetic material combination molded product to maintain a predetermined shape and promote seizure between the materials, annealing is necessary to process the molded granular magnetic material combination molded product. Must be carried out under pressure conditions.

The surface of granular magnetic material is often covered with an oxide film, and if left as is, it is difficult to cause burn-in. When annealing is performed in a reducing atmosphere, the surface of the granular magnetic material is reduced, making it easy for seizure to occur between the materials. A process in which annealing is performed under a reducing atmosphere is effective.

On the other hand, before the annealing process causes seizing between materials,
If the surface of the granular magnetic material is plated with a conductive material,
The electrical resistance between the combined granular magnetic materials can be reduced, and if the plated conductive material is more likely to seize than the unplated granular magnetic material, annealing can reduce the galling between the materials. This will further promote Copper, aluminum, nickel, tin,
It is possible to use alloys of zinc and iron. The plating thickness is the thickness necessary to reduce the electrical resistance between the combined granular magnetic materials, promote seizure between the materials, and ensure sufficient mechanical strength of the granular magnetic material combination molded product. Must be. The type of conductive material to be plated on the surface of the granular magnetic material needs to be determined depending on the difficulty of plating and the required magnetic circuit characteristics. If it is necessary to flow as much magnetic flux as possible, it is preferable to select a material with excellent magnetization properties, such as nickel, as the conductive material. Conversely, if the spaces between the granular magnetic materials are required to be non-magnetic or may be non-magnetic,
It may be plated with a non-magnetic conductive material.

[Example] Fig. 1 shows a state in which a magnet yoke for a whirlpool coil motor is being molded. 1.2 is a mold for molding, 3
is a combination of copper-plated granular magnetic materials and molded to form a magnetic circuit. The granular magnetic material constituting 3 is iron powder with an average diameter of about 0.1 mm.
It is plated with 1 μm copper. After molding, between the mold 1.2 and the copper-plated iron powder molded body 3,
Alumina powder was applied to prevent seizure between these, and annealed in hydrogen at 1000°C for 2 hours under pressure.
The molded body of the granular magnetic material No. 3 was baked and a predetermined yoke shape could be obtained.

FIG. 2 shows a field magnet 5 attached to a magnet yoke 4 obtained by molding and baking copper-plated iron powder.

[Effects of the Invention] The yoke of the present invention is made by combining and molding granular magnetic materials with clean surfaces and small surface roughness into a predetermined shape, and then annealing them under pressure to prevent seizure between the materials. ,
Since it is made of a magnetic material with a predetermined shape, a yoke of any shape can be obtained, and a three-dimensional magnetic circuit can be realized.

Further, by combining and molding particulate magnetic materials along the magnetic flux flow of the magnetic circuit, a yoke having ideal magnetic circuit characteristics can be obtained.

Even though the yoke is made up of a combination of granular magnetic materials, it is possible to reduce the interlayer resistance by causing burn-in between the materials and by plating the grain surface with a conductive material. eddy currents are more likely to flow. Therefore, when used as a yoke for a field magnet of an actuator such as a motor, it is preferable in terms of control because it suppresses changes in magnetic flux due to armature current.

Furthermore, by sufficiently baking between the materials of the combined molded body, it is possible to ensure a predetermined shape and also to provide mechanical strength.

Further, by appropriately selecting the type of plating material applied to the surface of the granular magnetic material, the magnetic circuit characteristics can be controlled. For example, if a material with excellent magnetization properties is selected as the plating material, magnetic flux can be made easier to flow in all directions.

The granular magnetic material constituting the yoke of the present invention can be easily formed into a predetermined shape, reducing processing costs, and the yoke of the present invention can be mass-produced by performing plating and annealing in large quantities. It is.

[Brief explanation of drawings]

Figure 1 is a drawing showing the state in which a magnet yoke for a voice coil motor is being molded, and Figure 2 is a diagram showing a state in which a field magnet is attached to the yoke obtained by molding and burning copper-plated granular magnetic material. FIG. 1.2... Molding mold, 3... Molded body constituting a magnetic circuit, 4... Magnet yoke used in a voice coil motor, 5... Field magnet.

Claims (7)

[Claims] 1. A yoke consisting of a molded body made by combining granular magnetic materials, and characterized by a state of seizing between the materials. 2. The yoke according to claim 1, wherein the granular magnetic material has a plating layer of a conductive material. 3. A method for manufacturing a yoke, which comprises combining granular magnetic materials, forming them into a predetermined shape, and then annealing them under pressure to cause seizure between the materials. 4. 4. The method for manufacturing a yoke according to claim 3, wherein the annealing under pressure is performed in a reducing atmosphere. 5. 5. The method of manufacturing a yoke according to claim 3, wherein the granular magnetic material has a surface layer plated with a conductive material. 6. 3. The yoke according to claim 1, wherein the yoke is a combination of a granular magnetic material, a linear magnetic material, or a plate-like magnetic material. 7. 6. The method of manufacturing a yoke according to claim 3, wherein the yoke is a combination of a granular magnetic material, a linear magnetic material, or a plate-like magnetic material.