Pure torque voice coil motor

Details Pure torque voice coil motor Pure torque voice coil motor

2001-06-25

2004-08-10

Cao, Allen (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

For shifting head between tracks

Reexamination Certificate

active

06775105

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to data storage devices. More particularly, the present invention relates to voice coil motors for effecting movement of disc drive actuators.
BACKGROUND OF THE INVENTION
A typical disc drive comes with discs on which data can be recorded. Read/write devices for recording data and for reading back stored data are supported by an actuator for movement across the surfaces of the discs. Rotary actuators which can be caused to rotate about a pivot by a voice coil motor are often chosen for use in today's disc drives. Basically, the voice coil motor is made up of a coil of wire located near a magnet which generates a magnetic field. When a current is passed through the coil, the coil interacts with magnetic field so as to effect motion of the coil relative to the magnet.
Various voice coil motor designs have been proposed over the years. For example, some have produced voice coil motors of a type where the coil is coupled to the actuator such that the coil is perpendicular to a plane of rotation of the actuator. The coil is situated between two magnets which have like poles facing each other. When the coil is activated by a passing current, torque is generated in the same direction by the two portions of the coil that are parallel to the plane of rotation, resulting in the rotation of the actuator.
Others have used a bipolar magnet, in which the magnet has a direction of magnetization that is substantially perpendicular to its major surfaces. In these arrangements, half of the magnet has a front-to-back north-south magnetization and the other half has a back-to-front north-south magnetization. The coil is arranged so as to be perpendicular to the plane of rotation of the actuator and parallel to the plane of the major surfaces of the magnets.
Still others have arranged bipolar magnets with their major surfaces parallel to the plane of rotation with a coil which is also parallel to the plane of rotation. The active portions of the coil are again subject to magnetic fields of opposite direction so that torque is generated in the same direction by both active portions of the coil to move the actuator.
Different problems associated with the performance of the voice coil motor have been experienced in the prior art, including issues such as the linearization of the torque-to-angular displacement curve, and the improvement of torque constant to moment of inertia ratio. Room for improvement remains, and consideration needs to be given to factors such as cost and ease of manufacture. One problem to which a viable solution remains wanting is the contribution of the voice coil motor to the vibration of the actuator, which in turn has a significant impact on the performance of the disc drive.
What the prior art has been lacking is a voice coil motor which addresses these problems while maintaining low cost and ease of manufacture.
SUMMARY OF THE INVENTION
The present invention relates to an improved voice coil motor that provides mainly torque on an associated actuator intended for use in a disc drive.
In accordance with one embodiment of the invention, two lengths of a wire coupled to the actuator and configured to carry current in opposite directions are in perpendicular arrangement in magnetic field of the same direction. The magnetic fields are substantially the same. Both lengths of the wire are situated in magnetic fields having the same direction. The lengths of wire are of different radial distance from the pivot about which the actuator is designed to rotate.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.


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