Perforated Tolerance Ring Wave Stiffness Control
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Solution Overview
Problem
Tolerance rings used in hard disk drives exhibit variations in stiffness, leading to performance issues such as resonance and alignment problems due to differences in wave stiffness, which can be compromised by optimizing gap location for one parameter, affecting overall performance.
Innovation Solution
Incorporating a plurality of holes or perforations in the tolerance ring to create controlled weaknesses in waves, ensuring consistent resonant frequency and stiffness around the circumference, preventing rocking of the post within the bore under operational loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap location in the tolerance ring is optimized for one performance parameter, then that specific parameter is improved, but other performance parameters are compromised
Solution Approach 1:
The patent applies local quality by introducing perforations at specific locations within the tolerance ring to create controlled weaknesses in wave regions. This localized modification allows different parts of the ring to have different stiffness characteristics, enabling optimization of both alignment accuracy and overall performance consistency simultaneously
Solution Approach 2:
The patent changes the physical parameters of the tolerance ring by adding perforations that modify the stiffness distribution. This parameter change creates controlled weaknesses that reduce sensitivity to gap location variations, allowing the ring to maintain consistent performance across different installation configurations
2Strength
If the tolerance ring uses waves to provide interference fit, then the interference fit and torque transmission are improved, but variations in wave stiffness cause resonance and alignment problems
Solution Approach 1:
The patent introduces perforations in specific wave regions to create controlled local weaknesses. This allows the wave structures to maintain their overall strength for interference fit while reducing their stiffness variability that causes resonance and alignment issues
Solution Approach 2:
The patent converts the harmful effect of wave stiffness variations into a benefit by strategically placing perforations to create controlled weaknesses. These controlled weaknesses reduce the stiffness variations that cause resonance, while the remaining wave structure maintains sufficient strength for torque transmission
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 tolerance ring maintains alignment and prevents rocking, providing consistent radial stiffness and resonant frequency, thereby enhancing the overall performance and reliability of the hard disk drive assembly.
Implementation Method 1
Incorporating a plurality of holes or perforations in the tolerance ring to create controlled weaknesses in waves, ensuring consistent resonant frequency and stiffness around the circumference
Implementation Method 2
The modified tolerance ring maintains alignment and prevents rocking, providing consistent radial stiffness and resonant frequency
Implementation Method 3
Tolerance rings may be used to provide an interference fit between parts required to transmit torque
Implementation Method 4
A tolerance ring generally comprises a strip of resilient material, for example a metal such as spring steel
Implementation Method 5
Each protrusion acts as a spring and exerts a radial force against the shaft and the surface of the bore, providing an interference fit between the shaft and the housing
Data Source
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AI summary
A tolerance ring (122) is disclosed and can include a generally cylindrical body (302) that can include a side wall (304). The sidewall can define a top and a bottom. Further, the sidewall can include a plurality of wave structures (322) that can extend from the sidewall, a plurality of unformed sections (340), and a gap (314) that can extend along the entire length of the body. Each unformed section can be located between a pair of adjacent wave structures. Further, the gap can establish a split in the body. The tolerance ring can also include at least one hole (342) intersecting at least one of the wave structures to establish a perforated wave structure.