JP2520371Y2 - Actuator for magnetic disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an actuator for a magnetic disk, and more particularly to a rotary (swing) actuator in which a magnetic head oscillates to draw an arc locus. .

[Conventional technology]

Conventionally, an oscillating or rotary actuator as shown in FIGS. 3 and 4 has been used to position a magnetic head on a recording track of a magnetic disk or the like.
In both figures, the permanent magnets 2 are fixed to the yoke 1, and they are arranged opposite to each other with different polarities and assembled by the columns 3.
A magnetic circuit is formed through the space 4. Reference numeral 5 denotes an arm. A flat type movable coil 6 is fixed to one end and a magnetic head (not shown) is fixed to the other end, and a shaft 7 is provided so that the movable coil 6 is located in the space 4. It is arranged so that it can rotate and swing freely. When a signal current is applied to the movable coil 6, a driving force around the shaft 7 acts on the movable coil 6 according to Fleming's left-hand rule, causing the arm 5 to rotate and swing,
The magnetic head fixed to the arm 5 is positioned on a predetermined recording track on the magnetic disk. The rotation direction is switched by reversing the direction of the current flowing through the coil. In the actuator of the above structure,
When the rocking speed of the arm 5 is detected and position control is performed, the magnetic disk, which is a recording medium, is, for example, 5in, 8in,
In the case of a large type such as 14 inches, the detecting means can be interposed independently because the magnetic head has multiple stages. However, for example, a small magnetic disk having a diameter of 3.5 inches has a problem that a space for separately interposing the detecting means cannot be secured. In order to solve this problem, an attempt has been made to inexpensively manufacture a miniaturized actuator by using the movable coil 6 that drives the arm 5 as a coil for detecting the swing speed.

The improved magnetic disk actuator has the features of being small and inexpensive, but has many problems that noise is extracted at the same time as the detection signal, causing malfunctions and low reliability. Besides, the control is relatively difficult, and there is room for improvement in terms of accuracy.

As one of the means for improving the above, the present applicant has a magnetic circuit formed by fixing a yoke to one side of permanent magnets having different polarities, with the permanent magnet surfaces facing each other, and a movable coil at one end. In a magnetic disk actuator having a magnetic coil fixedly attached to each of the arms and swingably formed, and a movable coil is arranged in the gap of the magnetic circuit, the other side of the one yoke is provided. An application has already been filed for a device in which another permanent magnet is fixed and a detection coil provided so as to cross the magnetic flux of this permanent magnet is provided so as to be able to swing together with the arm (Japanese Patent Application No. 62-105668).

[Problems to be solved by the invention]

With the above configuration, the detection coil can be provided independently of the movable coil to achieve a highly accurate and reliable control action, while the actuator as a whole can be downsized. That is, since a permanent magnet for detection does not require a very large magnetic flux density, the yoke is shared with that which constitutes a magnetic circuit for driving, and a thin magnetic circuit is formed by, for example, a ferrite magnet or the like, and a thick magnetic circuit is formed. It is intended to reduce the dimension in the depth direction.

However, in the recent field of magnetic disk devices, there have been demands for miniaturization, thinning, and high functionality of devices.
The severity is increasing further, and there is a problem that the above-mentioned improvements still do not satisfy the requirements.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a magnetic disk actuator that is small and thin, and that enables highly accurate control.

[Means for solving problems]

In order to solve the above problems, in the present invention, a housing is provided with a magnetic circuit formed by fixing a yoke to one side of permanent magnets having different polarities, and facing the permanent magnet surfaces, and a movable coil at one end. And an arm formed by swinging a magnetic head fixed to the other end, and the arm is rotatable in a magnetic disk actuator configured by arranging a movable coil in the gap of the magnetic circuit. A bearing cylinder in which a bearing that is axially supported is fitted inside is fixed to the housing, and a transverse cross-sectional contour is formed in an arc shape on a part of the outer circumference of the bearing cylinder opposite to the permanent magnet through the axis. A technique in which another permanent magnet is fixed, a detection coil is fixed to a detection portion extending below the arm so as to face the other permanent magnet, and the detection portion is rotatably provided in the circumferential direction. Adopt a means Than it was.

[Action]

With the above configuration, since the portion where the permanent magnet and the detection coil that form the sensor are provided is separated from the movable coil and the permanent magnet that form the drive system, the magnetic field of the driving permanent magnet has no effect on the detection coil. Since it does not affect and noise is not extracted, highly accurate control is possible. Further, even if a sensor is additionally provided, the thickness of the magnetic disk actuator is not increased, and the performance of the drive permanent magnet is improved so that the actuator can be made thinner and more compact. And

〔Example〕

FIG. 1 is an enlarged longitudinal sectional view of an essential part showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line BB in FIG. 1, and the same parts are referred to the same as those in FIGS. 3 and 4 above. It shows with a code. In FIGS. 1 and 2, reference numeral 8 denotes a housing, which is made of a non-magnetic material such as an aluminum alloy.
Reference numeral 9 denotes a bearing, which is fitted in a bearing cylinder 10 made of a soft magnetic material fixed in a housing 8 to rotatably support a shaft 7 fixed to an arm 5. Next, a part of the outer circumference of the bearing cylinder 10 is fixed with a permanent magnet 11 formed of, for example, a ferrite magnet, the cross section of which is formed in an arc shape. A detection unit 5a is integrally provided below the arm 5 and a detection coil 12 is arranged to face the permanent magnet 11 in the detection unit 5a.
The detection coil 12 is arranged so as to cross the magnetic flux from.

With the above configuration, when the arm 5 is rotated or swung around the shaft 7 by energizing the movable coil 6, the detection coil 12 provided in the detection unit 5a integrated with the arm 5 causes the permanent magnet 11 to move.
Since it crosses the magnetic flux from, a signal current flows in the detection coil 12. Therefore, the speed and position of the arm 5 can be detected by this, and the positioning of the arm 5 and other controls can be performed via the control system.

In this embodiment, an example in which the housing is made of an aluminum alloy is shown, but any other non-magnetic material may be used. Forming by die casting means is advantageous for mass production. In addition, the detection coil and the permanent magnet can be made to face each other and be relatively movable,
That is, the magnetic flux from the permanent magnet may be provided so that the detection coil traverses, and the arrangement may be reversed to that of this embodiment. Further, a recess may be provided in a part of the bearing tube or the detection part so as to be embedded. Further, since it is not necessary to make the magnetic flux density acting on the detection coil too large, for example, a permanent magnet made of a ferrite magnet is surface-magnetized, and a magnetic circuit formed by facing the yokes is sufficient. .

[Advantages of the Invention] The magnetic disk actuator of the present invention, which has the configuration and operation as described above, is small and thin and inexpensive, but is independent of the drive system and independent of the detection means. By providing the above, there is an effect that highly accurate control can be performed. In particular, there is an effect that it is possible to completely meet the recent demand for thinning and further downsize the entire device.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line BB in FIG. 1, and FIG. 3 is a partially fragmented partially sectional plan view showing a conventional one. FIG. 4 is a view on arrow A in FIG. 1: Yoke, 2, 11: Permanent magnet, 5: Arm, 6: Moving coil, 12: Detection coil.

Claims (2)

(57) [Scope of utility model registration request] 1. A housing having a magnetic circuit formed by fixing a yoke to one side of permanent magnets having different polarities so that the surfaces of the permanent magnets face each other, a movable coil at one end and a magnetic head at the other end. A magnetic disk actuator comprising a fixed and swingably formed arm and a movable coil disposed in a gap of the magnetic circuit, and a bearing for rotatably supporting the arm is provided inside. While fixing the fitted bearing cylinder to the housing, another permanent magnet having a cross-sectional contour formed into an arc shape is fixed to a part of the outer circumference of the bearing cylinder on the opposite side of the permanent magnet through the axis, An actuator for a magnetic disk, wherein a detection coil is fixed to a detection portion extending below the arm so as to face the other permanent magnet, and the detection portion is provided so as to be rotatable in a circumferential direction. 2. A utility model registration claim in which the permanent magnet is a rare earth magnet and the other permanent magnets are ferrite magnets.
An actuator for a magnetic disk according to the item.