Voice Coil Shape for Disk Drive Torque and Noise Reduction
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Solution Overview
Problem
Conventional voice coils in magnetic disk drives face challenges in generating strong rotating torque while minimizing out-of-plane forces that cause oscillation and noise, due to the limitations of magnetic flux distribution and the resulting weight and cost constraints.
Innovation Solution
A voice coil with a modified shape where the coil spacing on the rear end side is equal to or narrower than on the front end side, reducing the out-of-plane force and weight, and optimizing the coil design to position the center of gravity on the pivot shaft, thereby reducing oscillation and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional sectorial voice coil shape is used, then the voice coil can maintain torque characteristic for pivotal position, but the coil side lengths create unnecessary out-of-plane forces and increased weight
Solution Approach 1:
The patent applies asymmetry by inverting the conventional sectorial shape to a shape where the coil spacing on the rear end side is equal to or narrower than on the front end side. This asymmetric modification eliminates the projecting portions that generate out-of-plane forces while maintaining the necessary torque characteristic for pivotal position movement.
Solution Approach 2:
The patent extracts and removes the projecting portions (coil sides a and b) from the conventional sectorial voice coil design. By taking out these unnecessary portions that extend beyond the magnetic field boundaries, the patent eliminates the source of out-of-plane forces while preserving the essential torque-generating functionality.
2Weight of moving object
If the voice coil is made light-weight, then the moment of inertia decreases and positioning improves, but the torque generation capability may be reduced
Solution Approach 1:
The patent changes the geometric parameters of the voice coil by modifying the coil spacing distribution along the radial direction. By adjusting the coil spacing parameter to be narrower on the rear end side and wider on the front end side, the patent optimizes the balance between weight reduction and torque generation capability.
3Force
If the coil spacing is increased to generate stronger torque, then the torque efficiency improves, but the out-of-plane force and oscillation increase
Solution Approach 1:
The patent applies local quality by varying the coil spacing locally different regions of the voice coil. The coil spacing is designed to be narrower on the rear end side (where it contributes less to out-of-plane force) and wider on the front end side (where it contributes more to torque), creating an optimized local distribution that balances torque efficiency with oscillation control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified voice coil design achieves a 25% improvement in torque efficiency, decreases out-of-plane force by one-third, and reduces the moment of inertia by 15%, enhancing the positioning accuracy and reducing noise in magnetic disk drives.
Implementation Method 1
a voice coil motor (hereinafter referred to as 'VCM') drives an actuator assembly... a voice coil mounted on an actuator assembly, a voice coil magnet supported by a base
Data Source
AI summary
Embodiments of the invention provide an actuator head suspension assembly having an efficient voice coil. In one embodiment, a voice coil is formed in a circular or any other shape than the conventional sectorial shape to increase the efficiency of the voice coil and diminish oscillation and noise of an actuator head suspension assembly. The voice coil shape is selected such that the proportion of an out-of-plane force becomes smaller than that in the conventional sectorial voice coil and the proportion contributing as weight to the oscillation energy also becomes smaller.