JPS6126976A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To make a force generating in the coil fixed within all regions of magnetic gap by cutting off the part having a large amount of a whole magnetic flux in the magnet composing a magnetic circuit of a linear voice coil motor. CONSTITUTION:In terms of a shape of a magnet 6 composing a magnetic circuit of a linear voice coil motor, a central part having a large amount of a whole magnetic flux is designed to be shaped partially cut off in upper and lower surfaces thereof. When such shaped magnet 6 is incroporated in the magnetic circuit, the central part is recessed in relation to the distribution of magnetic flux. Therefore, when a driving coil 5 comes near a center of magnetic gap, the generating power of a coil is decreased more than in case of using a magnet having no notch. The condition that generating power of both tip and rear edge of the magnet has usually been declined can be improved by fixing a proper amount of cutting off of the magnet in order that generating power of a coil may be fixed in the whole region of magnetic gap.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic head positioning mechanism in a magnetic disk device.

[Technical background of the invention and its problems] FIG. 7 shows a conventional example of a magnetic disk device that is closest to the present invention. This device has a coil 13 movable in the head seek direction disposed within the magnetic gap of a magnetic circuit 1 consisting of a yoke 5 and a magnet 14, and a current is passed through the coil to generate a magnetic force in the coil. The carriage 16 on which the head 10 is mounted is moved in the head seek direction. Generally, a drive device with this structure is a linear voice drive device.
It is called a coil motor.

FIG. 8 shows the magnetic circuit of this device t. As shown in Figure 9, in the magnetic circuit, various magnetic paths are formed, as shown by the arrows in the figure. The magnetic flux passing through other magnetic paths is unrelated to the drive of the carriage.0 Figure 10 shows the distribution of magnetic flux density in the magnetic gap of this magnetic circuit. The direction in which the magnetic flux flows shown here is the direction of arrow a in FIG. As shown in Figure 10, the actual magnetic flux density in the nitric gap is
Because of the magnetic path, the magnetic flux density suddenly decreases at the ends of the magnet, such as point A and point 0. The force generated in the coil is proportional to the total number of magnetic fluxes passing through the coil. Therefore, the coil is
When it is near the point or CA, the value is much smaller than when it is at other positions, as shown in FIG. 11, causing problems such as variations in the seek speed of the recording head.

In conventional devices, the coil is driven only in the region where the magnetic flux density is constant, and the region where the magnetic flux density decreases at the front and rear ends is not used, or the coil is controlled by current control that increases the current flowing through the coil at the front and rear ends. The generating force was kept constant. However, these solutions that do not use the front and rear of the magnetic gap or add an extra control circuit are disadvantageous in reducing the size and weight of the device. [Object of the Invention] The present invention solves the above-mentioned drawbacks. The head actuator is a magnetic disk using a linear voice coil motor, which is formed in the magnetic circuit and generates a constant coil force even if the entire magnetic gap is used to drive the coil. It provides equipment.

[Summary of the Invention] In this invention, in the magnetic gap of the magnetic circuit of the linear voice coil motor used in the Herad actuator, the total number of magnetic fluxes crossing the coil is the same regardless of the position of the coil. In order to do this, by removing the magnets in areas with a large amount of total magnetic flux, we were able to reduce the amount of magnetic flux in those areas and make the force generated in the coil constant throughout the entire magnetic gear tube.

[Effects of the Invention] According to the present invention, the region in which the force generated in the coil of the voice coil motor is constant can be made longer than that of the conventional Herad actuator even with a magnetic circuit having the same external dimensions. ,Wear. This is an advantageous condition when downsizing the device because even if it is small, a long stroke can be obtained, and the current flowing through the coil is not controlled to keep the force constant. The electric circuit can be simplified.Furthermore, the amount of expensive magnetic materials used, such as zamarium-cobalt magnets, can be reduced, resulting in material cost savings.

[Invention example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic diagram of a magnetic disk device according to the present invention. In detail, only the magnet 6 is shown in FIG. This ore 6 is 1
．． It has a shape with a notch in a part of 11'il'T+, and when actually manufactured, the magnetic material is placed in a mold and molded, so the manufacturing process is different from that of a conventional rectangular cross-section magnet. remains unchanged. When a magnet having such a shape is incorporated into a magnetic circuit, the magnetic flux density distribution in the vicinity of the upper and lower surfaces of the magnet becomes a shape with a hollow center as shown in FIG. Therefore, when the coil is near the center of the magnetic gap, the force generated by the coil is less than in the previous magnetic circuit without the notch. Therefore, by cutting out an appropriate amount, the same coil generation force can be obtained whether the coil is located at the front or rear ends of the magnetic gap or at the center.

In fact, the inventors found that h=1.5 in the shape shown in Figure 4.
w, W=6M, H=30ya, t=30#
By using a linear voice coil motor using a magnet with dimensions lJ, b = 5mm, a head actuator with a variation in the coil generated force (f/fIn) as shown in Fig. 5 within ±5mm was obtained. ing. However, it is fmu average coil generated force.

[Other embodiments of the invention] The shape of the magnet used in the present invention is shown in Figure 6 (a).

Even with the shapes shown in (b), (c), (d), and (e), the effects of the present invention can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a magnetic disk device according to the present invention, and FIG.
The diagram shows a magnet o*11 used in the magnetic circuit according to the present invention.
Fig. 13, No. 1 is a graph showing the magnetic flux density distribution in the magnetic gap of the magnetic circuit according to the present invention, 'jAfJ4
The figure is a schematic diagram specifying the dimensions of each part of the magnet used in the magnetic circuit according to the present investigation, and Figure 5 is a diagram of the ζb disk device most related to the invention of the coil for the linear voice coil motor according to the present invention. Figures 8 and 9 are block diagrams showing the flow of magnetic flux in a magnetic sheath circuit. FIG. 11 is a graph showing the magnetic flux density distribution, and FIG. 11 is a graph showing the coil generation force distribution of a linear voice coil motor of a conventional magnetic disk device. ], 9... Magnetic disk 2.10... Head 3.
11,19.22 River magnetic circuit 4.12... Gap for magnetic shielding 5.13... Drive coil 6 + 14+ 17+
20...Magnet 7, 1!5. 18. 21...
Yoke 8,16... Carriage agent Patent attorney Noriyuki Chika (one person) , ) (b) (e) (C) Figure 8 Figure 9

Claims (2)

[Claims] (1) In a magnetic disk device having a magnetic disk and a movable magnetic head that accesses the related surface of the magnetic disk, a container containing the magnetic head and magnetic disk rotates around a predetermined axis so as to access data. a rotary spindle that rotates the magnetic disk, a magnetic disk mounted on the spindle, a magnetic head that performs a conversion operation on the surface of the magnetic disk, a carriage that is coupled to the magnetic head and is movable, and a motor that drives the carriage. In the magnetic disk drive configured, the total magnetic flux of the magnetic gap at both ends of the movable range of the drive coil that moves within the magnetic gap of the magnetic circuit of the linear voice coil motor used as the motor. , in order to equalize the total magnetic flux of the magnetic gap at other positions in the movable range of the drive coil, the volume of the magnet near both ends of the movable range of the drive coil is larger than that at other positions in the movable range of the drive coil. A magnetic disk drive characterized in that the linear voice coil motor is equipped with a magnetic circuit using a magnet. (2) A magnetic disk device according to claim 1, characterized in that the magnet is an integrally molded body.