Bellows-Shaped Grease Medium for Rolling Bearing Lubrication
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Solution Overview
Problem
Existing rolling bearing units with grease sealed lubrication mechanisms face issues with void formation due to thermal history, leading to interrupted base oil supply, especially in high-speed machine tools, where a narrow grease-filled space increases the likelihood of voids, causing insufficient lubrication.
Innovation Solution
A rolling bearing unit design incorporating a grease medium made of nonwoven fabric or similar materials, impregnated with base oil, that connects the grease reservoir to the bearing rings, ensuring continuous base oil supply even if voids form, using a bellows-shaped configuration to maintain contact and prevent void formation in critical clearances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If grease is filled in a narrow space between the outer ring spacer and outer ring, then the bearing unit can be compact, but void formation occurs more frequently leading to interrupted base oil supply
Solution Approach 1:
A grease medium (wiping member) is introduced as an intermediary component between the grease reservoir and the outer ring. This wiping member has a grease supply portion that contacts the grease reservoir and a grease wiping portion that contacts the outer ring, creating a reliable base oil supply path that is not affected by void formation in the narrow clearance space.
Solution Approach 2:
The grease medium is made of flexible material that can deform and maintain contact with both the grease reservoir and the outer ring. This flexibility ensures continuous base oil supply even when thermal expansion or contraction occurs, preventing interruption of lubrication.
2Length of stationary object
If the clearance between the outer ring spacer and outer ring is reduced, then the bearing unit size is minimized, but the frequency of void formation in grease increases
Solution Approach 1:
The grease medium serves as a mediator that bridges the gap between the grease reservoir and the outer ring, eliminating the need to rely on continuous grease filling in the narrow clearance. The wiping member maintains reliable contact and base oil supply even when the clearance is minimized.
3Device complexity
If grease is sealed in a fixed reservoir, then lubrication is simplified, but void formation interrupts base oil supply to the bearing
Solution Approach 1:
The grease medium acts as an intermediary that connects the sealed grease reservoir to the bearing surface. It has a grease supply portion that interfaces with the reservoir and a grease wiping portion that contacts the outer ring, ensuring continuous base oil supply while maintaining the simplicity of the sealed reservoir design.
Solution Approach 2:
The grease medium can be made of porous material that allows base oil to be absorbed from the grease reservoir and gradually released to the bearing surface, ensuring continuous lubrication supply even when voids form in the grease reservoir.
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
The solution ensures uninterrupted base oil supply to the bearing rings, maintaining a satisfactory lubricated state over a longer period, reducing the likelihood of voids and enhancing the bearing unit's lifespan by reliably connecting the grease reservoir to the bearing surfaces.
Implementation Method 1
a base oil supply path extending from the grease reservoir to the outer ring through which a base oil of the grease is guided to the outer ring under a capillary action
Implementation Method 2
a grease medium that connects a fixed ring out of the inner ring and the outer ring to the second inner wall (inner wall face of the side wall) located so as to be opposed to the fixed ring in the axial direction. The grease medium is able to be impregnated with a base oil contained in the grease.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A rolling bearing unit includes: a rolling bearing; a grease reservoir in which grease is reserved; an outer ring spacer disposed adjacent to an outer ring of the rolling bearing; and a bellows-shaped grease medium that connects a second side wall that defines the grease reservoir on the outer ring spacer side, to a step portion of the outer ring. The grease medium is disposed so as to be impregnated with a base oil contained in the grease.