JPH0265647A - Voice coil motor for magnetic disk device - Google Patents

Abstract

PURPOSE:To generate a constant driving force by placing permanent magnets forming a voice coil motor so as to generate parallel magnetic flux from all over the surface and by forming both ends thicker than the center section in the direction where a coil moves. CONSTITUTION:A voice coil motor is formed in arranging a yoke 9, an outside permanent magnet 10 installed to inside the yoke 9, an inside permanent magnet 11 and a coil 4 in the void formed by both magnets 10 and 11. The permanent magnets 10 and 11 are placed so that the magnetizing direction in all the faces may be parallel and directed in a fixed direction as shown by the arrow 13 and so that the direction of magnetization of the center section of the coil 4 may be directed toward an axial center 12. The permanent magnets 10 and 11 and also arc-shaped in cross section and the thickness of both ends of them is made thicker than that of their center sections. Thus, the quantity of flux interlinking with the coil 4 is made constant without regard to the position of the coil 4, so that the driving force generating to the coil 4 will be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voice coil motor for a magnetic disk drive, and particularly to a rotary voice coil motor that facilitates control of the seek system of a magnetic disk drive.

[Prior Art] As a conventional technology regarding a rotary type voice coil motor used in a magnetic disk device, for example, Japanese Patent Laid-Open No. 61-2
A technique described in Japanese Patent No. 73163 and the like is known.

This type of prior art is capable of making the generated torque uniform by determining the direction of magnetization of the permanent magnet so that the magnetic flux density in the air gap housing the instant-acting coil is uniformly distributed.

Hereinafter, an example of a voice coil motor according to this kind of conventional technology will be explained with reference to the drawings.

FIG. 4 is a plan view showing a schematic configuration of an example of the prior art. In Fig. 4, 4 is a coil, 9 is a yoke, 10 is an outer permanent magnet, 11 is an inner permanent magnet, 12 is an axis center, and 13
is the magnetic flux.

The rotary type voice coil motor according to the prior art shown in FIG. 4 has an outer permanent magnet 10 and an inner permanent magnet 11 attached within a yoke 9.

The coil 4 is disposed within the gap formed by the coil 11. The coil 4 is coupled to an actuator (not shown) for immediate movement of the magnetic head.

In the voice coil motor shown in FIG. 1, by immediately moving this coil 4 with current, a driving force is generated in the coil 4 with the shaft center 12 as a fulcrum, which immediately moves the actuator and moves the magnetic head to a predetermined position on the magnetic disk. Controls seeking to.

In the voice coil motor configured in this manner, it is necessary to ensure that the driving force generated in the coil 4 does not change depending on the position of the coil 4 within the gap formed by the permanent magnets 10 and 11.

Therefore, it is necessary to uniformly distribute the magnetic flux density within the air gap formed by the permanent magnets 10.11 so that the magnetic flux across the coil 4 does not change depending on the position of the coil 4. Therefore, the permanent magnet used in the conventional voice coil motor is formed to have a constant thickness in the radial direction.

The magnetic flux 13 is magnetized so that the direction of magnetization is in the radial direction, as shown by the arrows in FIG. That is, the permanent magnet 10.11 is magnetized so that its magnetic flux is directed toward the axial center 12 no matter which part of the permanent magnet 10.11 is taken. Due to this.

The magnetic flux distribution within the gap formed by the permanent magnets 10 and 11 can be made uniform, and the driving force for the coil 4 can be made constant regardless of the position of the coil 4.

[Problems to be Solved by the Invention] In the prior art, in order to make the magnetic flux density distribution uniform in the air gap in which the coil is arranged, the magnetization direction of the permanent magnet must be oriented in the radial direction. It is difficult to set the conditions for
Further, the magnetizing device also had the problem of being complicated and expensive.

An object of the present invention is to solve the problems of the prior art described above, and to easily set conditions for magnetizing a permanent magnet.

To provide a voice coil motor for a magnetic disk device in which the magnetic flux density distribution in the radial direction of the air gap in which the coil is arranged is uniform and the driving force applied to the coil is constant regardless of the position of the coil. be.

[Means for Solving the Problem] According to the present invention, the object is to change the magnetization direction of the permanent magnet to
Make all parts of the permanent magnet parallel so that they are in the same direction, make sure that the magnetization direction of the center of the permanent magnet points toward the center of the axis, and change the shape so that the center of the permanent magnet is thinner than the surrounding area. This is achieved by making the distribution of the magnetic flux density component in the radial direction uniform within the gap formed by these two permanent magnets.

[Function] The outer and inner permanent magnets housed in the yoke can be magnetized using a simple magnetizing device. In this case, if the thickness of the permanent magnet is kept constant, the magnetic flux distribution density in the radial direction within the gap formed by the two magnets cannot be made uniform. Therefore, in the present invention, the thickness of both permanent magnets is made thinner in the center than in one peripheral part.

This makes the magnetic flux distribution density in the radial direction uniform within the air gap. That is, in the present invention, when the actuator seeks the head toward the outer circumference or the inner circumference,
The thickness of the right or left side of the permanent magnet, where the driving coil is located, is thicker than that of the center. This makes it possible to uniform the magnetic flux distribution within the gap formed by the permanent magnet, and to reduce the driving force generated in the coil. , can be constant regardless of the position of the coil, that is, the seek position n of the head.

[Embodiment 1] An embodiment of a voice coil motor for a magnetic disk device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view showing a schematic configuration of an embodiment of a voice coil motor according to the present invention, FIG. 2 is a perspective view showing the shape of a permanent magnet, and FIG. 3 is an exploded view of a magnetic disk device to which the present invention is applied. FIG. In FIGS. 1, 2, and 3, 1 is a main base, 2 is an actuator, 3 is a bobbin, 5 is a voice coil motor, 6 is a sub-base, 7 is a disc, and 8 is a spindle assembly. Other symbols are the same as in FIG. 4.

As shown in FIG. 3, a magnetic disk drive to which the present invention is applied is composed of a main base 1, a spindle assembly 8 on which a disk 7 is mounted, an actuator 2, etc., and a sub-base 6. A spindle assembly 8 is attached to the main base 1, and an actuator 2 is attached to which a bobbin 3 around which a magnetic head and a coil 4 are wound is attached. Furthermore, a voice coil motor 5, which is a part of the actuator 2, is assembled and sealed by a sub-base 6.

As shown in FIG. 1, the voice coil motor according to the present invention used in the magnetic disk device configured as described above has the same features as the prior art described with reference to FIG.
It is composed of a yoke 9, an outer permanent magnet 10 and an inner permanent magnet 11 attached within the yoke 9, and a coil 4 disposed within the gap formed by both magnets.

The voice coil motor 5 according to this embodiment of the present invention is different from the prior art in the shape of the magnets 10, 11 and the direction of magnetization thereof. That is, in the permanent magnets 10° 11 of the voice coil motor used in the present invention, the direction of magnetizing force on all surfaces thereof is constant and parallel, as shown by the arrow 13 in FIG. The magnetization direction of the part is configured to face the center of the axis. As shown in FIG. 2, the permanent magnets 10.11 also have an arc-shaped cross section, and are formed so that the thickness at the center is thinner than at both ends, that is, at the left and right ends.

If the permanent magnet 10.11 is magnetized so that its entire surface is parallel as described above, and its thickness is constant as in the prior art, the force generated in the coil 4 will depend on the position of the coil 4 with respect to the permanent magnet. - If the coil 4 is located at the left and right ends of the permanent magnet, the force will be smaller than if the coil 4 is located at the center of the permanent magnet. This is because as the coil 4 moves toward the left and right ends of the permanent magnets 10 and 11, the magnetic flux that intersects the coil 4 has an angle with respect to the coil 4, so the magnetic flux that intersects the coil 4 decreases as a whole. It is.

In the embodiment of the present invention, in order to avoid such a phenomenon, the coil 4
In order to make the magnetic flux that intersects the same regardless of the position of the coil 4, the shape of the permanent magnet 10.11 is
As shown in FIG. 2, the center portion was formed to be thinner than the left and right ends.

According to the embodiment of the present invention described above, the permanent magnet 10°11
The magnetic flux density component in the radial direction, that is, directed toward the axial center 12, in the air gap formed by can be made constant, and the magnetic flux that intersects the coil 4 can be made the same regardless of the position of the coil 4. Therefore, the force generated in the coil 4 can be made constant regardless of the position of the coil 4.

FIG. 5 is a perspective view showing the shape of a permanent magnet in another embodiment of the present invention.

The shape of the permanent magnet according to this embodiment is such that the thickness of the magnet changes in the horizontal and vertical directions, and the entire magnet has a concave lens shape. The direction of magnetization is the same as in the embodiment described in FIGS. 1 and 2.

In such an embodiment, since the thickness of the permanent magnet is thicker at the peripheral portion thereof, even with such a shape, the same effect as in the embodiment shown in FIG. 1 can be achieved.

[Effects of the Invention] As explained above, according to the present invention, by using permanent magnets magnetized in parallel to a certain direction, the component of magnetic flux density directed toward the axial center within the gap formed by the permanent magnets is This makes it possible to create a low-cost, highly reliable magnetic disk drive in which the driving force generated in the coil does not change depending on the position of the coil shank. A voice coil motor can be provided.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a perspective view showing the shape of a permanent magnet, and FIG. 3 is an exploded perspective view of a magnetic disk device to which the present invention is applied. FIG. 4 is a plan view showing a schematic configuration of the prior art, and FIG. 5 is a perspective view showing the shape of a permanent magnet in another embodiment of the present invention. 1... Main base, 2... Actuator. 3...Bobbin, 4...Coil 55...
...Voice coil motor, 6...Sub base, 7...Disk, 8...Spindle assembly, 9...Yoke, 10... ...Outer permanent magnet, 11...Inner permanent magnet, 12...
center of axis. Rice) Figure 4 Figure 2 Figure 5

Claims (1)

[Scope of Claims] 1. A voice coil motor for a magnetic disk device comprising a permanent magnet, a yoke to which the permanent magnet is attached, and a coil disposed in a gap formed by the permanent magnet. A voice coil motor for a magnetic disk device, wherein the permanent magnet is magnetized to generate parallel magnetic flux from the entire surface, and both ends in the direction in which the coil moves are formed thicker than the center part. . 2. The voice coil motor for a magnetic disk drive according to claim 1, wherein the permanent magnet is thicker at the left and right end portions and upper and lower end portions of the periphery thereof than at the center portion.