MOVING RAMP SYSTEM FOR HDD LOAD/UNLOAD
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-18
Described is a system that incorporates a moving head load/unload ramp to improve data reliability in a hard disk drive. Head load/unload is a system designed to lift the recording heads off the disk surfaces in a hard disk drive when the disks are not spinning. The most common implementation of load/unload in today's hard disk drives uses a fixed comb of ramps that is positioned at the outer periphery of the disk stack. When the motor stops, the actuator is pushed outwards so that specially designed hook levers attached to the heads will engage the ramps, thereby lifting the heads off the disks. When the motor starts, the actuator is pushed inward so that these levers slide down the ramps and allow the heads to fly freely on the disk surfaces. The head load/unload system has numerous reliability advantages over the older contact start/stop system, where heads actually land on the disk surface when the motor stops. Tribological problems such as stiction, durability and fragility are eliminated by head load/unload. For this reason load/unload has been rapidly growing in popularity as a design feature among all market segments of hard disk drives. The current implementation of head load/unload does contain some risks, however. With today's fixed-comb design it is imperative to have tight control over the velocity of the actuator at all times. During the head loading and unloading events, if the actuator is moving too fast, the corners of the heads will contact and damage the disks, including possibly the area where customer magnetic data is stored. On the other hand, if the actuator is moving too slowly, the heads will spend too much time in the transition between the lifted and flying states-- during this time the heads are susceptible to scratching the disk surface because of edge contact. Also, a loss of servo control when the actuator is moving outward could cause both a too-fast load and a too-fast unload event after the bounce against the outer crashstop. These problems can be resolved by using a system where the ramps move during head load/unload and the crashstop can be switched between an inner and outer position. A motor attached to the ramp comb pushes the ramp toward or away from the disk edge at a controlled velocity during load/unload. To load the heads, the crashstop is first pushed into its inner position. The ramp comb is then moved outward while the actuator is biased against the crashstop. To unload the heads, the actuator is first biased against the crashstop. Then, the ramp comb is pushed toward the disk edge. Once the ramp comb lifts the heads, the crashstop retracts to its outer position.