Grouped Wave Tolerance Ring for Hard Disk Drive Alignment
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Solution Overview
Problem
Tolerance rings used in hard disk drives exhibit varying stiffness and resonant frequency around their circumference, leading to performance issues such as resonance and alignment problems, which can be compromised by optimizing gap location for one parameter at the expense of others.
Innovation Solution
A tolerance ring design featuring a plurality of waves arranged in groups equally spaced around the circumference, with symmetric flanges and unformed sections, providing consistent axial stiffness and resonant frequency to maintain post alignment and prevent rocking under operational loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap location in the tolerance ring is optimized for resonant frequency, then resonant frequency performance is improved, but axial stiffness performance deteriorates
Solution Approach 1:
The tolerance ring is segmented into multiple wave groups (first wave group, second wave group, third wave group, fourth wave group) spaced around the circumference, with unformed sections between them. This segmentation creates multiple stiffness centers that balance the mechanical properties, allowing the ring to maintain consistent axial stiffness while achieving improved resonant frequency characteristics through the strategic placement of formed and unformed sections.
2Reliability
If the gap location is optimized for one performance parameter, then that parameter is improved, but alignment performance deteriorates
Solution Approach 1:
The tolerance ring employs an asymmetric design where wave groups are positioned at specific locations around the circumference rather than being uniformly distributed. The first and second wave groups are positioned on one side of the gap while the third and fourth wave groups are positioned on the other side, creating an asymmetric stiffness distribution that maintains post alignment while allowing optimization of other performance parameters.
3Ease of manufacture
If waves are uniformly distributed around the circumference, then manufacturing is simplified, but stiffness consistency deteriorates
Solution Approach 1:
The tolerance ring features local quality variations where specific regions have different properties. Wave groups are concentrated in certain circumferential locations while unformed sections are placed in other locations, creating local stiffness variations. This local quality approach allows the ring to maintain consistent overall axial stiffness while enabling optimization of resonant frequency and alignment characteristics through strategic placement of formed and unformed sections.
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 grouped wave arrangement ensures consistent resonant frequency and axial stiffness, maintaining post alignment and preventing rocking within the bore, thereby enhancing the overall performance and reliability of hard disk drive assemblies.
Implementation Method 1
A tolerance ring generally comprises a strip of resilient material, for example a metal such as spring steel, the ends of which are brought together to form a ring. A band of protrusions extend radially outwards from the ring... Each protrusion acts as a spring and exerts a radial force against the shaft and the surface of the bore, providing an interference fit
Data Source
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AI summary
A tolerance ring (122) is disclosed and can include a generally cylindrical body (302) having a sidewall. The sidewall can include a first unformed section (310, 312) and a gap (314) in the first unformed section. The gap can extend along an entire length of the body to establish a split in the body. The sidewall can also include a second unformed section opposite the first unformed section, a first wave bank (330) flanking the first unformed section with the gap, and a second wave bank (332) flanking the first unformed section with the gap. The wave banks can be equally spaced around a circumference of the body of the tolerance ring and the body of the tolerance ring can be symmetrical about a center axis that extends from a center of the tolerance ring and bisects the gap in the first unformed section.