JPH06237565A - Moving-coil actuator - Google Patents

Abstract

PURPOSE:To provide a moving-coil actuator which is small in the number of constituent members, and is easy of assembly, and can sharply reduce the manufacture cost. CONSTITUTION:In a moving-coil actuator, which comprises a yoke consisting of ferromagnetic material and made in the shape of an E through a center yoke 2 out of a center yoke 2 and a pair of side yokes 3, permanent magnets 5 being fixed to the insides of the side yokes 3 so that the same poles may oppose to each other, and a moving-coil set in the magnetic space made between these permanent magnets 5 and the center yoke 2, and the mobile coil of which is constituted shiftably along the surfaces of the permanent magnets 5, the yoke constituent member or the yoke constituent member and the permanent magnet 4 are molded integrally by thermosetting resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk actuator, that is, a movable coil type in which a functional member such as a magnetic head is moved by a movable coil so as to draw an arc locus or a linear locus. The present invention relates to an actuator, and more particularly, to a moving coil actuator improved so that the number of constituent members is small, the assembly is easy, and the cost can be reduced.

[0002]

2. Description of the Related Art FIG. 2 is a partially sectional front view showing an example of a conventional moving coil actuator, and FIG.
FIG. 4 is a cross-sectional view taken along the line A, and FIG. 4 is an exploded perspective view of the magnetic circuit constituent members in FIGS. 2 to 4, reference numerals 1, 2 and 3 are a yoke piece, a center yoke and a side yoke, respectively, which are made of a ferromagnetic material such as soft iron into a quadrilateral plate shape, and have bolts and other fastening members (not shown). No.) to form an E-shaped yoke.

Reference numeral 4 denotes a short ring, which is made of a conductive material such as a copper plate in the shape of a hollow prism and is fitted into the outer periphery of the center yoke 2. Next, 5 is a permanent magnet, which is formed into a quadrilateral plate shape and is magnetized in the thickness direction.
The same poles are made to face each other and fixed to the inner surface of the side yoke 3. 6
Is an arm, and a movable coil 7 formed in the shape of a hollow square tube is fixed to one end, and a functional member (not shown) such as a magnetic head is fixed to the other end, and the movable coil 7 is formed by the permanent magnet 5. The movable coil 7 is located in the magnetic gap 8 along the surface of the permanent magnet 5 so as to be rotatable or swingable via the shaft 9. Reference numeral 10 is a counter yoke, which is formed in the shape of a quadrilateral plate from the same material as the E-shaped yoke, and is fixed to the open end of the E-shaped yoke via bolts and other fastening members (not shown).

When a signal current is applied to the movable coil 7 with the above-described structure, a driving force around the shaft 9 acts on the movable coil 7 according to Fleming's left-hand rule, causing the arm 6 to rotate or swing to move. For example, a magnetic head provided at the other end of 6 can be positioned on a predetermined recording track on the magnetic disk. The switching of the swing direction is
This is performed by reversing the direction of the current passed through the movable coil 7.

[0005]

In assembling the magnetic circuit as shown in FIGS. 2 and 3, the yoke piece 1, the center yoke 2 and the pair of side yokes 3 are first machined as shown in FIG. After processing, an E-shaped yoke is formed through these fastening members. Next, the permanent magnet 5 is fixed to the inner surface of the side yoke 3 with an adhesive. In this case, a heating and drying process is required to cure the adhesive, and it takes time and man-hours to fix the permanent magnet 5. Therefore, there is a problem that the cost becomes high. Further, when the adhesive is heated and dried, harmful adhesive outgas may be generated from the adhesive, which may contaminate the work environment.

On the other hand, in recent years, demands for thinning and cost reduction of this type of oscillating actuator have become increasingly strict, and in the above-mentioned conventional structure, the number of constituent members is large and the assembling cost is high. Since it is bulky, the above requirements cannot be satisfied.

The present invention solves the above-mentioned problems existing in the prior art, provides a movable coil actuator which has a small number of constituent members, is easy to assemble, and is capable of significantly reducing the manufacturing cost. The purpose is to do.

[0008]

In order to achieve the above object, in the present invention, a yoke made of a ferromagnetic material, in which a center yoke and a pair of side yokes are formed in an E shape through a yoke piece, is provided. , A permanent magnet fixed to the inner surface of the side yoke so that the same poles face each other, and a movable coil interposed in a magnetic gap formed between the permanent magnet and the center yoke. In a movable coil type actuator configured to be movable along the surface of a magnet, a technical means of integrally molding a yoke constituent member or a yoke constituent member and a permanent magnet with a thermoplastic resin material is adopted.

In the present invention, since the permanent magnet as a constituent member has a limited thickness, its operating point cannot be set high, so that a rare earth magnet having a large coercive force is preferably used. Further, in recent years, further thinning and higher performance are required. Therefore, in order to secure a high magnetic flux density in the magnetic gap, R-Fe-B system (R: Y, Nd, etc.) rare earth element It is more preferable to use one or more permanent magnets.

As the thermoplastic resin material in the present invention, for example, known resins such as polyphenylene sulfide resin, polybutylene terephthalate resin, polyamide resin, polyimide resin, polyamide imide resin, polyester resin (preferably heat resistance is preferable). Resin) can be used.

Among the above resins, the longitudinal elastic modulus (measurement method:
Those having an ASTM D-638) of 10 × 10 ⁴ kg / cm ² or more (preferably 13 × 10 ⁴ kg / cm ² or more) are preferable. In particular, it is preferable to use, as the thermoplastic resin, a liquid crystalline polyester resin (polyester having a rigid straight chain in the main chain) which is a kind of liquid crystal polymer (which exhibits liquid crystallinity in a molten state).

The liquid crystalline polyester resin includes (a) a copolymer of parahydroxybenzoic acid and polyethylene terephthalate, (b) a copolymer of poly-p-hydroxybenzoate and an aromatic dicarboxylic acid, an aromatic diol, ( c)
Although there are those having various basic compositions such as copolymers of poly-p-hydroxybenzoate and naphthoic acid, wholly aromatic compounds (b) and (c) are preferable in terms of strength and elastic modulus, The thing of (c) is more preferable. In particular, in the wholly aromatic polyester resin (c), since the rigid molecular chains are oriented in the flow direction at the time of molding, the longitudinal elastic modulus in that direction becomes large, and in addition, it has good vibration absorption characteristics and a linear expansion coefficient. It has the advantage of being small (close to a metallic material).

When the liquid crystal polymer is molded at a liquid crystal state temperature lower than the complete melting temperature, the fluidity is high and the molding is easy. Especially the longitudinal elastic modulus (tensile elastic modulus) is 16 × 10 ⁴ kg /
It is advisable to use a liquid crystal polymer of cm ² or more. Specific examples of such a liquid crystal polymer include Vectra A130 (1) which is a wholly aromatic thermotropic liquid crystalline polyester.
8 × 10 ⁴ ) (Unit: kg / cm ² , same hereafter), C130
(16 × 10 ⁴ ), A230 (30 × 10 ⁴ ), B23
0 (38 × 10 ⁴ ), A410 (21 × 10 ⁴ ), A4
22 (18 × 10 ⁴ ), C400 (17 × 10 ⁴ ), A
540 (16 × 10 ⁴ ) (above Celanese), XYD
AR RC-210 (16.2 × 10 ⁴ ), G-43C (1
6.1 × 10 ⁴ ) (above Dartco) and the like.

Incidentally, the longitudinal elastic modulus is steel: 220 × 10 ⁴ ,
Aluminum: 68 × 10 ⁴ , methacrylic resin: 4.2
× 10 ⁴ , polystyrene resin: 3.2 to 3.6 × 10 ⁴ , polyphenylene sulfide resin: 10 × 10 ⁴ (both units are kg / cm ² ), which is larger than that of general thermoplastic resin. The rigidity can be obtained. Further, as the liquid crystal polymer, in order to improve mechanical strength, heat resistance and the like, a material to which a filler such as glass fiber or carbon fiber is added can be used. Addition amount is 10
50% by weight is desirable, and more preferably 20-40% by weight.

Further, in the present invention, the above-mentioned thermoplastic resin is used.
Flexural modulus as fat (Measurement method: ASTM D-792)
Is 13 × 10^Fourkg / cm²The above can also be used effectively
It Examples of such a resin include the above-mentioned Vectra A.
130 (15 x 10^Four) (Unit is kg / cm², The same below
), C130 (14 x 10)^Four), A230 (29 x 1
0^Four), B230 (36 × 10^Four), A410 (18 ×
10^Four), A422 (17 × 10^Four), A540 (14
× 10^Four), XYDAR RC-210 (13.6 × 1)
0 ^Four), G-43C (14.9 × 10^Four) And Ryton R
-4 (14 x 10^Four) (Phillips Oil), DIC ・ P
PS FZ-1140 (14 x 10^Four), ASAHI
PPS RG-40JA (14.4 x 10^Four) (Asahi Glass),
Fortron 1140A1 (13 x 10^Four) (Polyplastic
Sticks), GS-40 (15 x 10)^Four), G-10
(20 x 10^Four), G-6 (18 × 10^Four), G-4F
(14 x 10 ^Four), FC-5 (16 × 10^Four) (Above East
Saw Sustil) and other polyphenylene sulphies
Do and the like.

[0016]

With the above construction, the number of constituent members can be reduced, and since the constituent members are integrally molded, the assembling work is facilitated and the manufacturing cost can be greatly reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional front view of a partial crushing essential part showing a magnetic circuit according to an embodiment of the present invention.
1 to 4 are designated by the same reference numerals. 11 in FIG.
Is a holding member and is made of, for example, glass-filled polyphenylene sulfide resin and is provided so as to embrace and integrate the outer peripheral surfaces of the yoke piece 1, the center yoke 2, the side yoke 3, and the permanent magnet 5.

In order to form the above magnetic circuit, an injection molding die is used, and the yoke piece 1, the center yoke 2, the side yoke 3 and the permanent magnet are provided at predetermined positions in the injection molding die. 5 is inserted in advance, a heated melt of a polyphenylene sulfide resin containing glass is injected, and after cooling and solidification, it may be taken out from a molding die. The holding member 11 is formed by injecting the heated melt, and the respective constituent members are integrally molded.

The permanent magnet 5 is, for example, Nd-Fe-B.
The magnet is formed into a flat plate shape using a magnetic material, magnetized in the thickness direction, and arranged so that the same poles appear opposite to each other. in this case,
The holding member 11 is formed so as to be able to hold at least the side surface of the permanent magnet 5, but it may be formed so that a part thereof extends to the surface of the permanent magnet 5.

In this embodiment, the example in which the peripheral edge of the holding member 11 is formed continuously has been described, but the same effect can be obtained even if the holding member 11 is formed in a discontinuous form or a form having a plurality of protrusions. It suffices to have a function capable of integrally holding the above-mentioned constituent members. The permanent magnet 5 may be magnetized after the magnetic circuit is constructed. Further, in the present embodiment, the actuator for the magnetic head is described, but the functional member to be provided at one end of the arm is not limited to the magnetic head, but the optical head or the like has the same operation. Further, the present invention is applicable not only to the swing type, but also to a mode in which the movable coil 7 (see FIG. 2) moves linearly along the center yoke 2.

[0021]

Since the present invention has the structure and operation as described above, the number of constituent members can be greatly reduced by integrally molding the constituent members of the magnetic circuit.
Assembling work becomes easy, and productivity can be greatly improved, resulting in a large reduction in manufacturing cost. Further, by integrating most of the constituent members, there is an effect that the moving coil actuator as a whole can be made smaller and thinner.

[Brief description of drawings]

FIG. 1 is a sectional front view of a partial crushing essential part showing a magnetic circuit in an example of the present invention.

FIG. 2 is a partially sectional front view showing an example of a conventional moving coil type actuator.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is an exploded perspective view of the magnetic circuit constituent member in FIGS. 2 and 3;

[Explanation of symbols]

 2 Center yoke 3 Side yoke 5 Permanent magnet 7 Moving coil 11 Holding member

Claims (1)

[Claims] 1. A permanent magnet, which is made of a ferromagnetic material and has a center yoke and a pair of side yokes formed in an E shape through a yoke piece, and a permanent magnet fixed to the inner surface of the side yoke so that the same poles face each other. And a movable coil interposed in a magnetic gap formed between the permanent magnet and the center yoke, the movable coil being movable along the surface of the permanent magnet. A movable coil type actuator characterized in that a yoke constituent member or a yoke constituent member and a permanent magnet are integrally molded with a thermoplastic resin material.