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Registered Member #54278
Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367
...sort of a reverse coilgun. A movable flat coil in a strong permanent magnetic field is swung on that axis by controlling the current through the coil. A quick look would say it all...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
extrct from Wikipedia HARD DISK DRIVE article
"The actuator is a permanent magnet and moving coil motor that swings the heads to the desired position. A metal plate supports a squat neodymium-iron-boron (NIB) high-flux magnet. Beneath this plate is the moving coil, often referred to as the voice coil by analogy to the coil in loudspeakers, which is attached to the actuator hub, and beneath that is a second NIB magnet, mounted on the bottom plate of the motor (some drives only have one magnet)."
to me it is a (curvi)linear motor I used to service mainframes in the '80s and a trolley carrying 19 heads was moved in and out of the spinning disks by a HUGE voice coil assembly, just like a loudspeaker voice coil on steroids.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
I think it fits into the category of "voice coil motor" or "voice coil actuator", and the moving-coil subcategory (as opposed to moving magnet).
VCAs with moving coils are ideal for many limited-angle rotary applications that require high acceleration. The fast acceleration capability is achievable by minimizing the moving mass, in this case, the moving coil. Since it is separate from the magnet, it is customizable to be more lightweight than the heavy permanent magnet field assembly, allowing extremely fast speeds.
A limitation of moving-coil designs is the need for flexible coil connecting wires (or brushes). The flexible connections in hard drives must be designed for some number of elastic bending cycles, as are the flexible connections to cylindrical voice coils in loudspeaker elements.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Always wondered why they don't use some variant of an acoustic drive, similar to a caterpillar focus on a camera. Would make a lot more sense than voice coils, and draw less power with the head(s) the only thing connected.
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Hard Drive Components.
