JPS5831662B2 - Head positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a helad positioning device that is small and lightweight and has little leakage magnetic flux.

Conventionally, when positioning a magnetic head on a recording track of a magnetic disk or the like, an oscillating head positioning device as shown in FIG. 1 has been used.

That is, the head positioning device 1 is moved along the arrow A by the shaft 2.
A magnetic head 4 is mounted on one end of a head arm 3 supported so as to be rotatable in a direction, a rectangular moving coil 5 is fixedly attached to the other end, and a permanent magnet 6 is fixedly attached to the rectangular moving coil 5. By passing a current through the coil 5, a complete magnetic circuit is formed through the yoke 1, and thereby the herad arm 3
The magnetic head 4 is positioned by driving the magnetic head 4 by one swing.

However, in such an oscillating head positioning device 1, when the current supplied to the rectangular moving coil 5 is increased in order to position the magnetic head 4 at high speed, the temperature of the rectangular moving coil 5 increases excessively. Furthermore, in order to increase the amount of magnetic flux generated in the coil 5, the yoke 7 must be made thicker, which has the disadvantage of increasing the size of the entire device.

Furthermore, in the substantially C-shaped yoke 1 as shown in FIG. 1, leakage magnetic flux increases, which has an adverse effect on the recording and reproducing operations of the magnetic head 4.

The present invention has been made in view of the above-mentioned drawbacks of the conventional art, and its object is to provide four fan-shaped yokes on the opposing surfaces of a pair of yokes disposed opposite to each other. permanent magnets are arranged axially symmetrically, two each facing each other,
By inserting and arranging a Nohira coil with a narrow coil width into the gap between these permanent magnets, a swing type head positioning device is provided which is small and lightweight and capable of reducing leakage magnetic flux.

Hereinafter, the present invention will be described in detail with reference to the drawings.

2 is a longitudinal sectional view of a magnetic circuit portion showing an embodiment of the head positioning device according to the present invention, FIG. 3 is a perspective view of the magnetic circuit portion shown in FIG. 2, and FIG. 4 is a view of the magnetic circuit portion shown in FIG. It is an I-I line arrow view.

In these figures, the structure in which the head arm 3 on which the magnetic head 4 is mounted is rotatably supported by the shaft 2 in the direction of the arrow A is the same as the conventional structure described above, but in the present invention, the conventional moving coil is a flat coil 20 with a narrow coil width, and this coil 20 is fixed to the shaft 2 via a coil frame 21.

On the other hand, flat yokes 25 and 26 forming a magnetic circuit section are arranged on the inner surfaces of a pair of upper and lower support plates 23 and 24 that are integrally connected by four pillars 22 so as to face each other. .

These pair of yokes 25 and 26 are formed into a substantially fan shape,
In addition, shallow grooves 2γ are formed in the centers of the surfaces facing each other.

Furthermore, four flat, approximately fan-shaped magnets 28a t 28 are attached to the end portions of the opposing surfaces of the pair of yokes 25° 26.
b and 29a t 29b are fixedly installed.

These fan-shaped magnets 28a, 28b t29 a t2
9b all have the same shape and magnets 28a, 29a and 28
b and 29b are facing each other, and magnets 28a and 29
Magnet a is magnetized so that the opposing surfaces are S and N poles, and the opposite surfaces are N and S poles, and magnet 2
The magnets 8b and 29b are magnetized in the opposite direction to the magnets 28a and 29b.

In the flat coil 20, the winding portions 20a and 20b in the direction intersecting the swinging direction are located at the gap portions 30 between the sector magnets 28a and 29a and between 28b and 29b.
These sector magnets 2 are placed at a t 30 b.
It is inserted between 8a, 28b, and 29at29b.

Note that the sector magnet 28 a t 28 b t 29
a.

A pole piece 31 is fixedly installed on the surface of each of the pole pieces 29b.

This pole piece 31 transfers the magnetic flux between the sector magnets 28a and 29a and 28b and 29b to the gap portion 30a t.
30b to make the magnetic flux uniform, but if the magnetic flux distribution is sufficiently uniform, it is not necessarily necessary and can be omitted.

Moreover, the sector magnets 28a j 28b and 29a. 2
In order to reduce the thickness of the magnet 9b, it is desirable to use a magnet with as large an energy product as possible, such as a rare earth magnet.

Thus, in such a configuration, the flat coil 20
When a current is passed through the pair of flat yokes 25 and 26, a magnetic circuit is formed that passes through the magnetic pole surfaces (opposing surfaces of the pole piece 31) forming the gap portions 30a and 30b.

At this time, the magnetic flux passing between the magnetic pole faces changes in accordance with the amount of current supplied to the flat coil 20, and in response to this magnetic flux change, the flat coil 20 receives the driving force, and It is rotated in direction A.

Therefore, the head arm 3 also rotates and swings, and the magnetic head 4 is properly positioned.

In this case, the fan-shaped magnets 28a, 28b, and 29at29b face each other only through the extremely thin pole piece 31, forming a gap 30a and 30b, so most of the magnetic flux is generated in the gaps 30a and 30b. , leakage magnetic flux is extremely small.

Moreover, by making the magnetic circuit symmetrical with respect to the center line that passes through the center O of the magnetic circuit section and is perpendicular to the plane of the paper as shown in FIG. 2, there is no leakage magnetic flux on the center line.
Furthermore, the leakage magnetic flux near the center line is smaller than that at other locations.

In addition, in the above configuration, the magnetic circuit goes around the flat yokes 25 and 26 through almost the shortest distance of the magnetic circuit, so the yokes 25 and 26 can be made smaller, and leakage magnetic flux is reduced. Since it is extremely small, a highly efficient magnetic circuit can be constructed.

Therefore, the gap portion 30a can be made small and lightweight.

A strong and uniform magnetic field can be obtained at 30b.

Therefore, even if a flat coil 20 having a coil width narrower than the magnetic pole surface is used instead of the conventional moving coil as shown in FIGS. 2 and 4, it is possible to generate sufficient driving force for high-speed head positioning. Can be done.

The coil 20 with such a narrow coil width has a smaller moment of inertia during oscillation than the conventional wide moving coil shown in Fig. 1, and also requires less coil wire length and number of turns. , is effective in enabling high-speed positioning with low power.

FIG. 5 is a perspective view of a magnetic circuit portion showing another embodiment of the present invention.

In this embodiment, two plates 40 and 41 made of a sector-shaped electrically conductive material having a sufficient size to cover the entire area in which the flat coil 20 (see FIG. 4) swings are attached to the sector-shaped magnets 28a and 41, respectively. >28b and 29a, 29
A gap portion 30 is formed fixedly facing b.
All other structures are the same as those of the above embodiment.

According to such a configuration, the inductance of the flat coil 20 can be reduced to about 1/2, and the rise of the coil current can be made faster.

Therefore, even higher speed driving is possible.

In this case, the two plates 40 made of the electrically conductive material
．． 41 is a fan-shaped magnet 28a sandwiching the flat coil 20.
, 28b and 29a, 29b, but only one fan-shaped magnet on one side, for example 28
It is clear that a considerable effect can be obtained even if the head positioning device is installed on the a and 28b sides. and four crow-flat fan-shaped magnets are placed on the opposing surfaces of these yokes.
By arranging two fan-shaped magnets facing each other, and inserting a flat moving coil with a narrow coil width into the gap between these fan-shaped magnets, it is possible to reduce the size and weight of the magnetic circuit and minimize leakage magnetic flux. Furthermore, since a movable coil with a coil width narrower than the magnetic pole surface can be used, high-speed positioning with low power is possible.

Furthermore, by simply installing a fan-shaped plate made of a good electrical conductor on the magnetic pole surface that covers the entire swinging area of the moving coil,
The inductance of the moving coil can be significantly reduced, and even higher speed driving is possible, so the effects are very large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a conventional swing type head positioning device, FIG. 2 is a vertical sectional view of a magnetic circuit portion showing an embodiment of the head positioning device according to the present invention, and FIG. A perspective view of the magnetic circuit shown in the figure, FIG. 4 is a perspective view of the magnetic circuit shown in FIG.
5 is a perspective view of a magnetic circuit portion showing another embodiment of the present invention. 1...Head positioning device, 2...Axis, 3...Head arm, 4...Magnetic head, 20...Flat coil , 21...
・Coil frame, 25, 26...Flat yoke, 2
8a, 28b, 29a, 29b... sector magnet,
3L30a, 30b... Gap part, 40, 4
1... A plate that is a good electrical conductor.

Claims (1)

[Claims] 1. In an oscillating head positioning device in which a head arm carrying a magnetic head is rotatably supported around an axis, a pair of first half yokes are arranged facing each other, and four yokes of the same shape are arranged. Fancy fan-shaped magnets are disposed on opposing surfaces of the pair of first half yokes, two each facing each other, to form a round ventilation circuit through the pair of yokes, and to be rotatable about the shaft. A head positioning device characterized in that a first half coil having a narrow coil width is disposed on a coil frame supported by a coil frame, and this coil is inserted into a gap between two of the four fan-shaped magnets facing each other.