Integrated Magnet / Pole Piece Assembly
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-12
Integrated Magnet Pole Piece Assembly This is a novel design of a voice coil motor assembly (VCM) for a data storage disk drive. This design has significant advantages for a disk drive configuration known as a "Split" or "Dual" actuator configuration, in which multiple disk drive rotary actuators are stacked vertically. In a more typical implementation of a VCM, the permanent magnets are bonded to the outside surface steel polepieces. This approach is acceptable for a voice coil motor configured to power a single disk drive rotary actuator. However, when a device is configured with multiple actuators stacked vertically to improve the data throughput performance of the disk drive device, the traditional approach cannot be well extended to serve multiple actuators. Extending the traditional approach results in very thin magnets, which are subject to thermal self-demagnetization. The performance of the magnetic circuit, when assessed in terms of the flux density in the operating gap, is poor. The proposed configuration addresses these challenges through the use of a "Picture Frame" pole piece. This pole piece would be manufactured from a non-magnetic material, such as aluminum or molded plastic. The Picture Frame opening in the pole piece is designed to accept and retain a magnet. With this approach the magnet can be significantly thicker than can be realized using the configuration shown as Prior Art. The substantial increase in magnet thickness eliminates the thermal self-demagnetization problem. It also significantly increases the flux density in the operating gap of the magnetic circuit. This is the primary performance metric for a VCM.