JPH0436228Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an actuator for magnetic disks, and particularly to a rotary (swing type) actuator in which a magnetic head swings in a circular arc trajectory. .

[Conventional technology]

Conventionally, to position a magnetic head on a recording track such as a magnetic disk, a swinging or rotating actuator as shown in FIGS. 3 and 4 has been used. In both figures, permanent magnets 2 are fixed to a yoke 1, and the permanent magnets 2 have different polarities and are arranged opposite to each other, and are assembled by columns 3 to form a magnetic circuit via a hollow part 4. Reference numeral 5 designates an arm, to which a flat moving coil 6 is fixed at one end and a magnetic head (not shown) at the other end. It is arranged so that it can rotate and swing freely. When a signal current is applied to the moving coil 6, a driving force around the shaft 7 acts on the moving coil 6 according to Fleming's left-hand rule, causing the arm 5 to rotate and swing, thereby releasing the magnetic field fixed to the arm 5. The head is positioned on a predetermined recording track on the magnetic disk. Note that the rotation direction is switched by reversing the direction of the current flowing to the coil. In the actuator having the above structure, when position control is performed by detecting the swing speed of the arm 5, if the magnetic disk serving as the recording medium is large, such as 5 inches, 8 inches, or 14 inches, the magnetic head may also be multi-staged. Therefore, the detection means can be independently installed. However, a small magnetic disk with a diameter of 3.5 inches, for example, has a problem in that it is not possible to secure a space for separately installing a detection means. In order to solve this problem, attempts have been made to manufacture a compact actuator at low cost by using the movable coil 6 that drives the arm 5 also as a coil for detecting the swing speed.

[Problem that the invention attempts to solve]

Although the above-mentioned improved actuator for magnetic disks has the characteristics of being compact and inexpensive, it has many problems such as noise being extracted at the same time as the detection signal, malfunctions occurring, and reliability being slightly low. In addition, it is relatively difficult to control, and there is still room for improvement in terms of accuracy.

It is an object of the present invention to solve the above-mentioned problems and to provide a magnetic disk actuator that is compact and capable of high-precision control.

[Means for solving problems]

In order to solve the above problems, in this invention,
A magnetic circuit is formed by fixing a yoke to one side of permanent magnets with different polarities, with the permanent magnet surfaces facing each other, and a swingable arm is formed by fixing a moving coil to one end and a magnetic head to the other end. It consists of
In the magnetic disk actuator configured by disposing a moving coil in the empty part of the magnetic circuit,
Another permanent magnet is fixed to the other side of the one yoke, and a detection coil is provided to cross the magnetic flux of the permanent magnet so as to be able to swing freely in cooperation with the arm.
This technical method was adopted.

[Effect]

With the above configuration, it is possible to achieve a highly accurate and highly reliable control effect by providing the detection coil and the movable coil separately, and at the same time, it is possible to achieve miniaturization of the actuator as a whole. In other words, since the permanent magnet for detection does not require a very large magnetic flux density, the yoke is used in common with the magnetic circuit for driving, and a thin magnetic circuit is formed using, for example, ferrite magnets, etc. The aim is to reduce the size in the horizontal direction.

〔Example〕

1 and 2 are an enlarged sectional view and a partially omitted bottom view of essential parts showing an embodiment of the present invention, respectively, and the same parts are designated by the same reference numerals as in FIGS. 3 and 4. . In both figures, 8 is a housing, which is made of a non-magnetic material such as an aluminum alloy and has a fan-shaped planar shape. Reference numeral 9 denotes a bearing, which rotatably holds the shaft 7 fixed to the arm 5. Next, in the housing 8, permanent magnets 2, 2 made of, for example, rare earth magnets each having a fan-shaped or trapezoidal planar shape are arranged with different poles facing each other, via yokes 1a, 1b made of soft magnetic material. hand,
Form a magnetic circuit. Next, on one side of the housing 8 is a yoke 10 made of a soft magnetic material such as an iron plate.
and a permanent magnet 11 made of, for example, a ferrite magnet.
are arranged to face each other, and a detection coil 12 is interposed therebetween.
That is, a permanent magnet 11 formed into a substantially trapezoidal shape is fixed to the lower surface of the yoke 1b, and a yoke 10 fixed to the housing 8 is disposed facing each other to form a magnetic circuit. An arm 13 made of a non-magnetic material such as resin is fixed to the lower end of the shaft 7, and a detection coil 12 is embedded in the free end.
It is interposed so as to cross the magnetic flux of the permanent magnet 11.

With the above configuration, when the arm 5 rotates or swings around the shaft 7 by energizing the movable coil 6, the arm 13 also rotates in cooperation with the arm 5, so that a signal current is generated in the detection coil 12. This allows the speed and position of the arm 5 to be detected, and the positioning and other controls of the arm 5 to be performed via the control system.

In this embodiment, an example is shown in which the housing is made of an aluminum alloy, but it may be made of other materials as long as they are non-magnetic. Note that molding by die casting means is advantageous for mass production. Although the detection coil and other detection means may be provided on either one of the housings, the thickness of the entire actuator can be reduced by providing a recessed portion in a part of the housing. Furthermore, since the magnetic flux density that should act on the detection coil does not need to be very high, for example, a permanent magnet made of ferrite magnet with surface magnetization and a magnetic circuit formed by opposing yokes are sufficient. .

[Effect of idea]

Because the magnetic disk actuator of the present invention has the configuration and function described above, it is small, thin, and inexpensive. This has the effect of enabling control.

[Brief explanation of the drawing]

1 and 2 are an enlarged sectional view of the main part and a partially omitted bottom view of the main part showing an embodiment of the present invention, respectively. The figure is a view taken in the direction of arrow A in FIG. 3. 1, 1a, 1b... Yoke, 2, 11... Permanent magnet, 5, 13... Arm, 6... Moving coil, 12... Detection coil.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A magnetic circuit formed by fixing a yoke to one side of permanent magnets with different polarities and making the permanent magnet surfaces face each other, a moving coil at one end and a magnetic head at the other end. In the actuator for a magnetic disk, the arms are fixedly fixed to each other and are swingable, and a movable coil is disposed in the hollow part of the magnetic circuit. 1. An actuator for a magnetic disk, characterized in that a magnet is fixed thereto, and a detection coil is provided to cross the magnetic flux of the permanent magnet and is swingable in cooperation with the arm. (2) The actuator for a magnetic disk according to claim 1, wherein the permanent magnet is a rare earth magnet and the other permanent magnet is a ferrite magnet.