Fluid Dynamic Bearing Sleeve Radial Thrust Pressure Generation
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Solution Overview
Problem
Fluid dynamic bearing devices face challenges in downsizing while maintaining thrust direction supporting force due to reduced thickness of the bearing sleeve, which decreases the thrust dynamic pressure generating portion and buffering capacity.
Innovation Solution
A fluid dynamic bearing device with a porous body positioned radially inside the thrust dynamic pressure generating portion, allowing for reduced thickness without sacrificing thrust load capacity, and incorporating axial through-holes to maintain pressure balance and prevent negative pressure generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the bearing sleeve is reduced to downsize the device, then the total amount of lubricating fluid is reduced and sealing device capacity can be decreased, but the area of the end surface is reduced which decreases the thrust dynamic pressure generating portion and reduces supporting force in the thrust direction
Solution Approach 1:
The invention relocates the thrust dynamic pressure generating portion from the end surface of the bearing sleeve to the outer peripheral surface of the porous body. This spatial repositioning allows the thrust load-bearing area to be maintained even when the bearing sleeve thickness is reduced, as the dynamic pressure generation occurs on the cylindrical outer surface rather than the circular end surface.
Solution Approach 2:
The bearing sleeve is constructed as a porous body that allows lubricating fluid to penetrate and generate dynamic pressure on its outer peripheral surface. This porous structure enables the thrust dynamic pressure generating portion to be formed on the outer cylindrical surface, providing adequate thrust support area independent of the bearing sleeve thickness.
2Quantity of substance
If the thickness of the bearing sleeve is reduced to downsize the device, then the total amount of lubricating fluid is reduced allowing smaller sealing device, but the thrust dynamic pressure generating portion is reduced leading to insufficient buffering function
Solution Approach 1:
By forming the thrust dynamic pressure generating portion on the outer peripheral surface of the porous body rather than the end surface, the invention creates a cylindrical pressure generation zone that maintains adequate lubricating fluid volume for buffering even when overall device size is reduced.
Solution Approach 2:
The invention changes the geometric parameters of the thrust dynamic pressure generating portion by relocating it to the outer peripheral surface with appropriate radial and axial dimensions, ensuring sufficient lubricating fluid retention for thermal expansion buffering while maintaining compact overall size.
3Area of stationary object
If the area of the end surface is reduced due to reduced thickness, then the device size is decreased, but the thrust dynamic pressure generating portion is reduced which leads to reduction in supporting force
Solution Approach 1:
The invention transitions the thrust dynamic pressure generation from a two-dimensional end surface to a three-dimensional outer peripheral surface of the porous body. This allows the thrust load-bearing area to be distributed around the circumference, maintaining sufficient pressure generation area independent of the bearing sleeve thickness.
Solution Approach 2:
The porous structure of the bearing sleeve enables the thrust dynamic pressure generating portion to be effectively formed on the outer peripheral surface, utilizing the porous matrix to generate and sustain dynamic pressure in the thrust direction across a sufficient area despite reduced end surface dimensions.
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
Enables downsizing of the bearing device while maintaining thrust direction supporting force and reducing the volume of the sealing device, effectively preventing lubricating oil leakage and maintaining stable lubrication.
Implementation Method 1
a thrust dynamic pressure generating portion facing the thrust bearing gap, for exerting a dynamic pressure effect of a lubricating fluid
Implementation Method 2
a porous body provided with the shaft portion which is disposed along an inner periphery thereof
Data Source
AI summary
An outer peripheral surface (8d) of a bearing sleeve (8) is formed on a radially inside with respect to a first dynamic pressure generation portion (B1). In this case, it is possible to reduce a thickness of the bearing sleeve (8) while securing a first thrust dynamic pressure generating portion (B1) which has a thrust load capacity equivalent to that in a conventional case where a thrust dynamic pressure generating portion is formed in an end surface of the bearing sleeve. Accordingly, it is possible to reduce the thickness of the bearing sleeve (8) without sacrificing a bearing performance in a thrust direction. With this structure, a total amount of a lubricating oil sealed in a bearing device can be reduced, thereby reducing a capacity of a buffering function so as to downsize a sealing portion (9), and by extension, downsizing a fluid dynamic bearing device (1).