Fluid Dynamic Bearing Surface for Bidirectional Low-Speed Support
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Solution Overview
Problem
Existing fluid dynamic bearing devices have limited rotation direction adaptability, small bearing area, and insufficient dynamic pressure at low rotation speeds, leading to operational complexity and potential shaft contact issues.
Innovation Solution
The use of polygonal hill and groove patterns on the bearing member's inner and shaft member's outer surfaces increases the bearing area and dynamic pressure, allowing for adaptable rotation direction and efficient lubrication, even at low speeds, through optimized groove and hill configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If herringbone pattern dynamic pressure generating grooves are used, then dynamic pressure is generated, but the bearing area is small and surface pressure is high
Solution Approach 1:
The bearing surface is segmented into multiple hill portions and groove portions arranged in a specific pattern. This segmentation increases the total bearing area by creating multiple contact zones (hill portions) distributed across the bearing surface, thereby reducing surface pressure while maintaining dynamic pressure generation capability.
Solution Approach 2:
The invention transitions from a two-dimensional herringbone groove pattern to a three-dimensional structured surface with hill portions protruding radially inward. This dimensional change creates additional bearing area through the radial protrusions, increasing the effective contact area between the shaft and bearing surface.
2Force
If herringbone pattern grooves are used, then dynamic pressure is generated, but rotation direction is limited to one direction
Solution Approach 1:
The hill portions are arranged asymmetrically with respect to the groove portions, creating a configuration that generates dynamic pressure effectively in both forward and reverse rotation directions. This asymmetric yet balanced arrangement allows the bearing to adapt to bidirectional rotation while maintaining sufficient dynamic pressure generation.
Solution Approach 2:
The bearing surface structure is designed to perform the same dynamic pressure generation function regardless of rotation direction. The hill and groove portions are configured to work effectively whether the shaft rotates clockwise or counterclockwise, making the bearing universal for bidirectional applications.
3Force
If conventional grooves are used, then dynamic pressure is generated at high speed, but sufficient dynamic pressure cannot be obtained at low rotation speed
Solution Approach 1:
Different regions of the bearing surface (hill portions and groove portions) are designed with specific local characteristics optimized for low-speed operation. The groove portions are configured to effectively trap and retain lubricant, creating a lubricant reservoir effect that maintains dynamic pressure generation even at low rotation speeds where conventional grooves fail.
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 enhances operability by allowing bidirectional rotation, improves wear resistance, and ensures non-contact support of the shaft, even at low speeds, thereby reducing the risk of contact and extending the bearing's service life.
Implementation Method 1
a radial dynamic pressure generating portion configured to support the shaft member in a relatively rotatable and non-contact manner with pressure of a fluid film formed in a radial bearing gap
Implementation Method 2
it is difficult to obtain a sufficient dynamic pressure effect, and it is difficult to support the shaft member in a non-contact manner
Data Source
AI summary
Provided is a fluid dynamic bearing device, including: a shaft member; a bearing sleeve (18) having the shaft member inserted along an inner periphery thereof; and dynamic pressure generating grooves (26) configured to support the shaft member in a relatively rotatable and non-contact manner with pressure of an oil film formed in a radial bearing gap defined between an outer peripheral surface of the shaft member and an inner peripheral surface (24) of the bearing sleeve (18). The dynamic pressure generating grooves (26) include: the large number of polygonal hill portions (27) arranged in a pattern on the inner peripheral surface (24) of the bearing sleeve (18) ; and polygonal groove portions (28) formed in such a manner as to surround the polygonal hill portions (27).