Fluid Dynamic Bearing Cup-Shaped Thrust Washer Radial Stiffness
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Solution Overview
Problem
Conventional fluid dynamic bearing apparatuses face challenges in maintaining radial stiffness and preventing lubricating oil from coming under negative pressure, especially when the axial dimension of the shaft is reduced, leading to potential tilting of rotating members and leakage issues.
Innovation Solution
The design incorporates a shaft with a cup-shaped lower thrust washer and a rotating member with specific minute gaps filled with lubricating oil, featuring a tapered seal portion and dynamic pressure generating grooves to manage oil flow and prevent negative pressure, while maintaining a reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the axial dimension of the shaft is reduced to make the fluid dynamic bearing apparatus thinner, then the size and thickness of the apparatus is reduced, but the length of the radial dynamic pressure bearing portion is reduced causing a reduction in radial stiffness
Solution Approach 1:
The invention introduces a new structural dimension by adding a cup-shaped member that extends radially outward, creating a multi-dimensional support structure. This allows the radial dynamic pressure bearing portion to maintain sufficient length for stiffness while the overall axial dimension of the shaft is reduced, effectively resolving the contradiction between thickness reduction and radial stiffness maintenance
Solution Approach 2:
The bearing structure is segmented into distinct functional portions: the radial dynamic pressure bearing portion, the cup-shaped member, and the rotating member with recess. This segmentation allows each component to be optimized independently - the radial bearing portion maintains length for stiffness, while the cup-shaped member provides structural support without increasing axial dimension
2Strength
If a substantially cup-shaped member is adopted to maintain a sufficient length of the radial dynamic pressure bearing portion, then radial stiffness is maintained, but the lubricating oil held in the minute gap may come under negative pressure
Solution Approach 1:
The invention introduces an intermediary communication path through the cup-shaped member structure that connects the minute gap to the external environment. This intermediary structure allows pressure equalization, preventing negative pressure buildup in the lubricating oil while maintaining the radial stiffness provided by the cup-shaped geometry
Solution Approach 2:
The minute gap is strategically positioned and dimensioned with specific local characteristics - it is located between the rotating member and cup-shaped member with controlled clearance. This local quality optimization ensures sufficient radial stiffness while preventing negative pressure conditions through proper gap design
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 configuration enhances radial stiffness, prevents lubricating oil from coming under negative pressure, and effectively manages air bubbles, ensuring reliable operation and extended lifespan of the fluid dynamic bearing apparatus.
Implementation Method 1
dynamic pressure grooves provided in each of the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion produce a pumping action to induce a fluid dynamic pressure on the lubricating oil filling a minute gap
Implementation Method 2
The third minute gap includes a tapered seal portion where a radial width of the third minute gap gradually decreases in a downward direction. The lubricating oil has a liquid interface located within the tapered seal portion.
Data Source
AI summary
A fluid dynamic bearing apparatus includes a first minute gap, a second minute gap, a third minute gap, a fourth minute gap, and a fifth minute gap. A flow of a lubricating oil from the fifth minute gap to the fourth minute gap is caused by a plurality of dynamic pressure generating grooves arranged within the fluid dynamic bearing apparatus. This flow causes air bubbles mixed in the lubricating oil within the fifth minute gap to flow toward the third minute gap and be discharged to an outside through the third minute gap. In addition, a flow of the lubricating oil into the third minute gap caused by a centrifugal force accompanying rotation is inhibited.