JPH01318537A - Magnetic circuit of voice coil motor - Google Patents

Abstract

PURPOSE:To reduce the cost by joining in solid phase a rare earth magnet with yokes where at least a kind of a rare earth element containing Y as a permanent magnet, at least a kind of transition metals and at least a kind of group IIIb elements is a fundamental composition. CONSTITUTION:A rare earth metal, a transition metal and boron are weighed so that the composition may be Pr17Fe76Cu3B4. They are melted and cast in an induction heater and a casting ingot (magnet) 101 thus obtained is covered with a sheath 102 of pure iron. Hot rolling is applied to it at 950 deg.C. The process rate is about 80%. By the hot rolling process the direction easy to magnetize the magnet becomes parallel with the direction of process. After that heat treatment is performed at 100 deg.C for 24 hours. Cutting and grinding are performed. A side yoke 103 and a facing yoke 104 are fitted. A voice coil motor magnetic circuit is thereby obtained where a back yoke 102 is jointed in solid phase to the magnet 101.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic circuit for a movable coil type voice coil motor.

[Prior art] In many conventional magnetic circuits of voice coil motors, a permanent magnet and a yoke are bonded together using an adhesive. I was doing the gluing.

Permanent magnets currently in use include alnico, hard ferrite, and rare earth-transition metal magnets. In particular, rare earths (hereinafter abbreviated as R).

)-transition metal (hereinafter abbreviated as TM) type magnet R-
Since Co-based permanent magnets and R-Fe-B-based permanent magnets provide high magnetic performance, much research and development has been conducted on them.

Conventionally, there are methods for manufacturing these R-TM-B permanent magnets as shown in the following documents.

(1) A sintering method based on powder metallurgy.

(Reference 1, Reference 2) (2) Using the melt spinning method, a quenched flake with a thickness of about 30 μm is made using a quenched thin body device used to produce amorphous alloys, and the flake is made into a magnet using a resin bonding method. Resin bonding method using quenched flakes.

(References 3 and 4) (3) A method of mechanically orienting the rapidly cooled flakes used in the method (2) above using a two-step hot press;
(Document 4, Document 5) Here, Document 1; JP-A-59-'46008 Document 2; M
, Sagawa, S., Fujimura, N.
Togawa.

H, Yamamoto and Y, Matu
ura; J, Appl, Phys.

Vol, 55(6)15 March 1984 p.
2083 Document 3; JP-A-59-211549 Document 4; R, W, Lee; Appl, Phys;
Lett, Vol, 46(8)15 April
1985 p790 document 5; JP-A-60-100402
No. Publication [Problem to be Solved by the Invention] By using the above-mentioned conventional technology, R-TM-B
Although permanent magnets can be manufactured, these manufacturing methods have the following drawbacks.

For the sintering method (1), it is essential to turn the alloy into powder, but R-TM-E alloys are very active against oxygen, and the powder process increases the surface area and prevents oxidation. In addition, when molding the powder, a molding aid such as zinc stearate must be used. Although this is removed during the pre-sintering process, the spherules remain in the magnet in the form of carbon.

This carbon is undesirable because it deteriorates the magnetic performance of the R-TM-B magnet.

The molded product after press molding with the addition of molding aids is extremely brittle and difficult to handle. Therefore, another major drawback is that it takes a considerable amount of effort to arrange them neatly in a sintering furnace.

Furthermore, in order to obtain an anisotropic magnet, press molding must be performed in a magnetic field, which requires large equipment such as a magnetic field power source and a coil.

Generally, manufacturing R-TM-B sintered magnets not only requires expensive equipment but also has low production efficiency.
The manufacturing cost of the magnet increases, and therefore, it is difficult to say that the advantages of the R-TM-B magnet, which uses relatively cheap raw materials, can be utilized.

Next, there are methods (2) and (3), but these methods have very low productivity and require the use of expensive vacuum melt spinning equipment.

Since the magnet obtained by method (2) is isotropic in principle, the energy product is low, and the squareness of the hysteresis loop is not good, so the temperature characteristics are also poor.

Although method (3) yields an anisotropic magnet, since hot pressing is used in two stages, it cannot be denied that it will be extremely inefficient when considering mass production.

Further, the permanent magnet of the voice coil motor is rarely used alone, but is used together with a yoke made of soft magnetic material or the like. However, with conventional technology, magnets are manufactured individually;
Methods such as attaching a yoke to it have been used. In this method, the magnet must be processed with high precision,
This is a major constraint in the magnet manufacturing process. Particularly in motors, magnets are often used in the form of a ring, and machining the inner surface of this ring-shaped magnet is technically difficult and expensive.

Therefore, the present invention aims to solve these problems.
The purpose is to use permanent magnets that include R (where R is at least one rare earth element including Y), M (at least one transition metal), and X (however, III
The purpose of this invention is to provide a voice coil motor magnetic circuit at low cost by solid-phase bonding a rare earth magnet whose basic composition is at least one kind of group B elements to a yoke.

[Means for Solving the Problems] A voice coil motor magnetic circuit of the present invention includes a permanent magnet and a yoke made of a soft magnetic material. A rare earth magnet whose basic components are at least one rare earth element), M (but at least one transition metal), and It is characterized by a solid state bonding between the body and the yoke.

[Embodiment] FIG. 1 shows a side view of an embodiment of the voice coil motor magnetic circuit of the present invention.

Since the flat permanent magnet 101 having anisotropy in the thickness direction is solid phase bonded to the back yoke 102, the fixing strength is more than 10 times that of conventional adhesives.

Below, a method for manufacturing a voice coil motor magnetic circuit according to the present invention will be explained in detail.

Table 1 shows the alloy composition of the magnet produced according to the present invention.

However, the composition of the magnet is not limited to those shown in Table 1, and the rare earth metals include Y, La, Ce, Pr.
, Nd, Sm, Eu, Gd, Tb
, Dy, HOlEr, Tm, Yb, and Lu are listed as candidates, and one type or a combination of two or more of these can be used. The highest magnetic properties are P
Obtained by r. Transition metals include Fe, Ni,
CU and the like are listed as candidates, and one or a combination of two or more of these can be used.

Furthermore, small amounts of additive elements, such as heavy rare earth elements such as Dy and Tb, Al, Si, Mo, and Ga, are effective in improving the coercive force.

Rare earths, transition metals, and boron were weighed so as to have the composition shown in Table 1, and melted and cast in an induction heating furnace. It is covered with a pure iron sheath 102. This was hot rolled at 950°C. The processing rate is about 80%. Figure 1(b)
As shown in , the direction of easy magnetization of the magnet becomes parallel to the pressing direction due to hot rolling. Then 1000℃, 24
The side yoke 103 and the opposing yoke 104 are heated to the side yoke 103 and the opposing yoke 104 are
A voice coil motor magnetic circuit was obtained in which the pack yoke 102 was solid phase joined to the magnet 101 by attaching it as shown in Figure (d). In the conventional method, both the yoke and the magnet must be polished and bonded together, but in this embodiment, such a step is not necessary, and the number of steps is significantly reduced. Table 2 shows the magnetic properties of this yoke-integrated magnet.

It can be seen that a magnet that is sufficiently durable for practical use has been obtained.

Table 2 [Effects of the Invention] As described above, in the voice coil motor magnetic circuit of the present invention, the basic components of the permanent magnet are R (where R is at least one rare earth element including Y), M (however, Since the permanent magnet and yoke, which are made of at least one transition metal (at least one transition metal) and It has the effect shown.

(a) The bonding strength between the magnet and yoke is extremely high, so there is no worry that the magnet will move due to vibration and impact during use.

(b) Since there is no adhesive layer between the magnet surface and the yoke surface, magnetic circuit loss is reduced and the magnet is used more efficiently.

(c) Unlike conventional magnetic circuits, there is no need to finish the adhesive surfaces of the magnet and the yoke, so manufacturing costs can be kept low.

(d) Because the magnet does not undergo a powdering process when manufacturing the magnet, the oxygen temperature in the magnet is uneven, and a magnetic circuit with excellent corrosion resistance is obtained. For example, when used in a hard disk drive device, etc., the magnetic There is almost no dust generation, which was a problem in the circuit.

[Brief explanation of the drawing]

FIGS. 1(a), (b), (c), and (d) are manufacturing process diagrams of the voice coil motor magnetic circuit of the present invention. Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki 1 person (α) (b) (C) Figure 1

Claims (1)

[Claims] In a voice coil motor magnetic circuit composed of a permanent magnet and a soft magnetic yoke, the basic component of the permanent magnet is R (where R is at least one rare earth element including Y).
Species), M (at least one transition metal), and X (at least one group IIIb element), using a rare earth magnet obtained by casting and hot working,
A voice coil motor magnetic circuit characterized in that the rare earth magnet and the yoke made of the soft magnetic material are solid phase joined.