JPH0595663A - Voice coil motor - Google Patents

Abstract

PURPOSE:To reduce the variations of the torque constant of a voice coil motor, which drives the magnetic head of a magnetic disc, etc., and improve its accuracy, by absorbing the variations of the magnetic performance of a permanent magnet. CONSTITUTION:A voice coil motor, wherein a yoke part 2, on which a permanent magnet 21 is mounted opposing to a voice coil part 11 of an oscillating arm 1, is formed with a movable yoke part 22 and a fixed yoke part 23, and the permanent magnet 21 fastened on the movable yoke part 22 is made movable by the yoke part 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice coil motor for driving a magnetic head in a magnetic disk device or the like.

In manufacturing the voice coil motor,
The performance and dimensions of the permanent magnets are factors that determine the torque constant, but since the permanent magnets have variations in their magnetic performance, the torque constants also vary and do not vary. If it is troublesome and the variation is large, when driving the head of the magnetic disk device,
Since a seek error occurs, variations in the performance of the permanent magnets cause a decrease in yield.

Under such circumstances, there is a demand for a voice coil motor which can be easily manufactured in response to variations in magnetic performance of permanent magnets and has high accuracy.

[0004]

2. Description of the Related Art Conventionally, a voice coil motor used for driving a magnetic head of a magnetic disk apparatus is mounted with a magnetic head 20 in order to move the magnetic head 20 on the magnetic disk 10, as shown in FIG. Swing arm 3
0, the voice coil portion 310 is provided at the end opposite to the magnetic head 20, and the yoke portion 40 provided with the permanent magnet 410 is formed so as to surround the swinging arcuate path of the voice coil portion 310. It is configured to obtain a constant rotational torque by controlling the current to the voice coil unit 310.

[0005]

However, in the conventional configuration, even if the voice coil portion 310 and the yoke portion 40 are manufactured to have constant positions and sizes, the permanent magnet 410 itself has a variation in magnetic performance. In order to obtain a constant rotating torque for a constant current, the permanent magnet 4
It is necessary to correct the magnetic circuit and the like so as to absorb the variation in the performance of No. 10, which makes the manufacturing process troublesome.

Therefore, an object of the present invention is to provide a highly accurate voice coil motor in which variations in magnetic performance of permanent magnets are easily corrected and variations in torque constant are reduced.

[0007]

SUMMARY OF THE INVENTION The above object is to realize a voice having a voice coil portion 11 provided at an end portion of a swing arm 1 and a yoke portion 2 provided with a permanent magnet 21 facing the voice coil portion 11. In the coil motor, the movable yoke portion 22 formed by fixing the yoke portion 2 to the permanent magnet 21 and the movable yoke portion 22 are connected to the voice coil portion 11.
This is achieved by using a voice coil motor composed of a fixed yoke portion 23 that is displaceably held.

[0008]

That is, in the present invention, the relative position between the permanent magnet 21 and the voice coil portion 11 is displaced by configuring the yoke portion 2 to which the permanent magnet 21 is attached with the movable yoke portion 22 and the fixed yoke portion 23. Can be made The strength of the magnetic force of the permanent magnet 21 is distributed more in the central portion. Therefore, by moving the position of the permanent magnet 21 with respect to the voice coil portion 11, the apparent magnetic strength and the voice coil are increased. Change the length of
The torque constant can be adjusted.

Therefore, it is possible to easily set the predetermined torque constant without correcting the magnetic circuit by merely adjusting the movement of the movable yoke portion 22.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. 1 and 2 show a voice coil motor provided at an end portion of a swing arm 1 for driving a magnetic head of a magnetic disk device. The swing arm 1 is a conventional magnetic disk shown in FIG. Similar to the vibrating arm 10 of the apparatus, a magnetic head 20 is provided on the tip end side, and an intermediate portion between the magnetic head 20 and the voice coil portion 11 of the voice coil motor is swingably supported by the pivot shaft 4. ..

The voice coil section 11 is provided in a magnetic field formed by a permanent magnet 21 which is connected to a magnetic circuit (not shown) and which surrounds the swing path of the voice coil section 11. By supplying a predetermined current to the voice coil section 11 by a magnetic circuit, a turning force is applied to the rocking arm 1 to rock it by a predetermined amount.

The permanent magnet 21 is fixed to the yoke portion 2 which is erected so as to form the swing path 5 of the voice coil portion 11. Further, the yoke portion 2 includes a movable yoke portion 22 to which the permanent magnet 21 is adhered and fixed, and the movable yoke portion 22.
Fixed yoke part 23 for holding the slidable and adjustable position
It is composed of

The movable yoke portion 22, as shown in FIG.
The holding frame 24 opened in the fixed yoke portion 23 is fitted in a state in which the width direction is restricted, and a slidable gap 25 is vertically arranged in the vertical direction (the length direction of the swing arm 1). Formed and adjustably attached by an adjusting screw 26.

That is, both ends of the adjusting screw 26 are rotatably inserted in the fixed yoke portion 23, and the adjusting screw 26 is shown in FIG.
As shown in, the screw hole 2 formed in the movable yoke portion 22
The screw portion of the adjusting screw 26 is screwed into the screw 21. Therefore, by rotating the head of the adjusting screw 26, the movable yoke 22 restricted in the width direction by the holding frame 24 moves in the up-down direction, that is, the length direction of the swing arm 1, and the movable yoke portion 22 moves. The relative position between the fixed permanent magnet 21 and the voice coil portion 11 of the swing arm 1 can be displaced.

The magnitude of the force generated by the voice coil motor per constant current is determined by the BL value, that is, a constant obtained by multiplying the strength of the magnetic force of the magnet (B) and the length of the coil in the magnetic field (L). However, the strength of the magnetic force of the permanent magnet is
It is not uniform throughout, and as shown in FIG. 3, it is distributed so as to become stronger in the central portion.

Therefore, the permanent magnet 21 and the voice coil 11
The BL value can be changed by displacing the relative position with respect to, and the BL value can be adjusted to the set value by performing the position adjustment according to the variation in the performance of the permanent magnet 21 to correct the magnetic circuit. A constant torque constant can be obtained without performing.

In the case of the voice coil motor of this embodiment, the voice coil 1 is adjusted by adjusting the position of the permanent magnet 21 in the outward direction away from the pivot shaft 4 of the swing arm 1.
A larger magnetic force can be applied to the outer peripheral side of No. 1 to increase the torque constant. On the contrary, when the torque constant is smaller than the set value, the permanent magnet 21 is adjusted by shifting it inward.

FIG. 4 shows a modification of this embodiment, in which the N pole portion 221 and the S pole portion 221 of the permanent magnet 21 are arranged in parallel on the movable yoke portion 22.

[0019]

As is apparent from the above description, according to the voice coil motor of the present invention, it is possible to easily correct the variation of the magnetic force performance of the permanent magnets with a slight position adjustment, and to make the torque constant uniform. And a highly accurate voice coil motor can be provided at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an explanatory diagram showing a modified example of the embodiment of the present invention and magnetic force distribution.

FIG. 4 is an explanatory diagram showing a magnetic disk device.

FIG. 5 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

 1 Swing Arm 11 Voice Coil 2 Yoke 21 Permanent Magnet 22 Movable Yoke 23 Fixed Yoke

Claims (1)

[Claims] 1. A voice coil portion (11) provided at an end of a swing arm (1), and a yoke portion (2) provided with a permanent magnet (21) facing the voice coil portion (11). In the voice coil motor, the yoke (2) is the permanent magnet.
A movable yoke portion (22) formed by fixing (21), and a fixed yoke portion (23) that holds the movable yoke portion (22) so as to be displaceable with respect to the voice coil portion (11). And voice coil motor.