Fluid Dynamic-Pressure Bearing with Annular Oil Buffer
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Solution Overview
Problem
Conventional fluid dynamic-pressure bearing devices face issues with lubricant circulation and pressure differences between the shaft tip and thrust bearing, leading to potential leakage and increased resistance during high-speed rotation, especially in compact designs.
Innovation Solution
The design incorporates an annular gap with a larger dimension than the thrust gap, which serves as an oil buffer and facilitates lubricant circulation, with spiral grooves to stir and discharge air bubbles, and a communicating path to manage pressure differences, reducing shaft losses and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the thrust dynamic-pressure bearing is formed at the annular gap portion positioned radially outside the bearing, then the bearing structure is simplified, but shaft loss increases significantly
Solution Approach 1:
The patent applies local quality by creating a thrust dynamic-pressure bearing portion with a smaller gap dimension at a specific radial position (within the bearing) rather than uniformly across the entire annular gap. This localized modification reduces resistance and shaft loss in the critical bearing region while maintaining the simplified overall structure. The gap dimension is specifically controlled to be smaller than the annular gap dimension at the radially outer side, creating a localized low-resistance zone.
2Reliability
If redundant rows of grooves are provided for feeding lubricating liquid towards the bearing center, then lubricating liquid leakage is prevented, but resistance during rotation increases
Solution Approach 1:
The patent extracts and removes the redundant rows of grooves that were previously used to feed lubricating liquid toward the bearing center. Instead, it relies on the thrust dynamic-pressure bearing portion itself and the controlled annular gap to manage lubricating liquid circulation. This elimination of unnecessary grooves reduces rotational resistance while the patent compensates for leakage prevention through the pressure differential created by the gap dimension differences and the oil buffer function of the annular gap.
3Volume of moving object
If the bearing device is miniaturized to reduce size, then compactness is achieved, but lubricating liquid circulation between shaft tip end and thrust bearing is interrupted
Solution Approach 1:
The patent uses dimensionality change by creating a three-dimensional pressure differential structure through varying gap dimensions in different radial positions. The annular gap dimension is made larger than the thrust dynamic-pressure bearing portion gap dimension, creating a vertical pressure gradient that drives lubricating liquid circulation from the shaft tip end through the thrust bearing. This dimensional variation in the gap structure enables effective lubricant circulation in the miniaturized device without requiring additional circulation paths.
4Loss of energy
If the annular gap dimension is made larger than the thrust gap dimension, then resistance at the annular gap portion is reduced, but the bearing gap becomes smaller
Solution Approach 1:
The patent applies local quality by creating different gap dimensions at different radial positions: the annular gap dimension is made larger at the radially outer side to reduce resistance, while the thrust dynamic-pressure bearing portion gap dimension is kept smaller to maintain bearing performance. This localized differentiation allows the system to simultaneously achieve low resistance in the annular gap region and adequate bearing gap for load support.
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 effectively reduces resistance, prevents lubricant leakage, and increases the reliability of the bearing by ensuring consistent lubricant distribution and efficient air bubble discharge, making it suitable for compact and miniaturized applications.
Implementation Method 1
a thrust dynamic-pressure bearing portion (19) formed at a radially inner side of the bearing in cooperation with the upper end surface of the sleeve (10)
Implementation Method 2
the annular gap portion also serves as an oil buffer, thus easily maintaining the amount of oil
Implementation Method 3
grooves having a spiral shape or the like may be formed at the annular gap portion to stir up lubricating liquid in the inward direction of the bearing
Data Source
AI summary
Small-size, small-height fluid dynamic-pressure bearing device that causes a low shaft loss and is less prone to troubles such as shortage and leakage of lubricating liquid. A thrust dynamic-pressure bearing is formed at an inner position and a region having a slightly-widened gap is provided outside of the thrust dynamic-pressure bearing to retain the lubricating liquid therein. Further, an oil circulating path is communicated with the region having a slightly widened gap. The gap of this region is set to be greater than the gap at the thrust dynamic-pressure bearing portion by the value of the depth of dynamic-pressure generating grooves. The region having a widened gap may be provided with rows of grooves for stirring-up lubricating oil towards the center.