Spindle Motor Seal Gap Design for Helium Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In spindle motors used in disk drive apparatuses, the leakage of low-density gases like helium from the interior of the HDD is a challenge due to their small molecules, which complicates the sealing of the base and shaft interface, leading to vibration and precision issues.
Innovation Solution
The spindle motor design incorporates a seal gap between the inner circumferential portion of the base and the shaft, which gradually decreases in radial width with increasing height, and is filled with adhesive over its entire circumference, along with a press-fitting region and a recessed portion to enhance sealing, preventing gas leakage and improving perpendicularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shaft is fixed in a through hole defined in the base, then the motor structure is simple and easy to manufacture, but sealing of the region where the base and shaft are fixed is insufficient, leading to gas leakage
Solution Approach 1:
The fixing region is divided into two distinct regions: a press-fitting region for mechanical fixation and an adhesion region for sealing. This segmentation allows each region to perform its specific function optimally - the press-fitting region provides structural support while the adhesion region with the tapered seal gap ensures gas tightness.
Solution Approach 2:
Different regions of the shaft and base are given different properties: the press-fitting region has a cylindrical shape for mechanical interference fit, while the adhesion region has a tapered shape that gradually decreases in radial width to create a seal gap. This local differentiation of geometric properties enables both fixation and sealing functions.
2Reliability
If the interior of the HDD is filled with low-density gas like helium, then resistance against the disk and head during rotation is reduced, but the small molecules of helium easily leak out through the shaft-base interface
Solution Approach 1:
An adhesive is introduced as an intermediary substance in the seal gap between the shaft and base. The adhesive fills the tapered gap and cures to form a sealing barrier that prevents helium gas molecules from passing through the interface, while still allowing the mechanical fixation function to operate.
Solution Approach 2:
The sealing solution transitions from a two-dimensional surface contact to a three-dimensional volume filling. The tapered seal gap creates a volumetric adhesive bond that blocks the path of gas molecules, utilizing the third dimension (radial depth) to prevent leakage rather than relying solely on surface sealing.
3Reliability
If a seal gap is defined between the inner circumferential portion and shaft lower portion, then gas leakage is prevented, but manufacturing precision requirements increase due to the tapered geometry
Solution Approach 1:
The seal gap geometry is designed with a gradual taper rather than an abrupt change. The radial width decreases progressively along the height, which reduces stress concentrations and allows for more relaxed manufacturing tolerances compared to a sharp-edged seal, while still achieving effective sealing when filled with adhesive.
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
This design effectively prevents gas leakage and enhances the precision and reliability of the disk drive apparatus by ensuring a secure seal between the shaft and the base, maintaining the integrity of the internal gas and improving the motor's operational stability.
Implementation Method 1
the seal gap is arranged to include an adhesive arranged therein over an entire circumference thereof
Data Source
AI summary
A spindle motor includes a shaft arranged to extend in an axial direction, and a base portion arranged to define a portion of a housing, and including a through hole in which the shaft is inserted. A fixing region is defined between an inner circumferential portion of the base portion and a lower portion of the shaft. The fixing region includes a press-fitting region and an adhesion region defined on a lower side of the press-fitting region and in which a seal gap is defined between the inner circumferential portion of the base portion and the lower portion of the shaft. The seal gap is arranged to gradually decrease in radial width with increasing height. The seal gap is arranged to include an adhesive arranged therein over an entire circumference thereof.