The present invention relates generally to disc drives. More particularly, the present invention relates to a low cost voice coil motor for use in a disc drive.
Disc drives are used extensively for data storage in various applications. A typical disc drive includes discs on which data is written and heads to read data from and to write data to the discs. The heads are supported by an actuator assembly which allows the heads to be positioned at the desired locations relative to the data tracks on the discs.
Rotational movement of the actuator assembly is generally enabled by a voice coil motor. The voice coil motor is basically made up of a magnet fixed relative to the disc drive housing and a voice coil fixed relative to the actuator assembly. By providing an electric current through the voice coil, a force is exerted on the voice coil, causing the actuator assembly to rotate about a pivot. Pole plates are provided to maximize the magnetic field in the vicinity of the voice coil so as to improve the performance of the voice coil motor.
One important consideration in the production of disc drives is the need to reduce particulate contamination within the disc drive. Particulate contamination in a disc drive must be kept low in order to prevent physical damage to the heads as well as to the discs. Disc drives are required to operate with increasing precision, following the increase in the data densities. Not only are the heads being placed in increasing proximity to the disc surface, the number of data tracks per inch on the discs is also increasing significantly. This increased precision means that particulate contamination in the disc drive must be closely controlled, as the damage caused by contaminants is becoming correspondingly serious. For example, particulate buildup between the head and the disc can cause degradation in the readback signal, head crashes and damage to the disc surface.
The various components must therefore be designed with care so as to avoid the use of materials likely to contribute to particulate contamination. Pole plates are one potential source of particulate contamination, as they are known to outgas when they reach high temperatures. For this reason, pole plates are often coated with a nickel plating, using nickel with high potassium, to prevent the pole plates from outgassing and contaminating the interior environment of the disc drive. Although nickel plating is effective in reducing outgassing, it is a relatively expensive process.
A further potential source of contaminants is the adhesive typically used to mount the magnet to the pole plate. While adhesives are effective in rigidly securing the magnet to the pole plate, they are also prone to outgassing when subjected to the heat typically generated within a disc drive during operation.
What the prior art has been lacking is an easily assembled, low cost voice coil motor which is resistant to outgassing.
The present invention relates to a voice coil motor for a disc drive suitable for low cost production. In accordance with one embodiment of the invention, the voice coil motor includes an overmold encapsulating a voice coil motor assembly including a magnet and a pole. The overmold prevents outgassing by the pole and magnet.
These and other features and benefits will become apparent upon a review of the attached figures and the accompanying description.