Sealed Bearing Lip Structure for Low-Torque Contaminant Exclusion
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Solution Overview
Problem
Conventional sealed bearings with shot peened seal sliding surfaces face limitations in reducing torque and increasing speed due to high friction and wear, and struggle to prevent entry of foreign objects larger than a predetermined diameter, while also experiencing burr formation issues at the seal lip's distal edge.
Innovation Solution
A sealed bearing design featuring a seal lip with protrusions that gradually decrease in height toward the distal edge, creating oil passages and wedge-shaped gaps to facilitate fluid lubrication, reducing seal torque, and preventing foreign object entry by determining the minimum particle diameter that can pass through the oil passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the seal sliding surface is subjected to shot peening to form minute undulations, then the seal torque decreases due to reduced sliding contact area, but the seal torque cannot be significantly reduced and the bearing speed remains limited due to oil film formation difficulties at high temperatures
Solution Approach 1:
The seal sliding surface is divided into multiple circumferential sections with alternating high-roughness and low-roughness regions. The high-roughness portions (with Ry ≥ 3.0 μm) are segmented into discrete circumferential zones rather than covering the entire surface, allowing localized oil trapping while maintaining sealing contact. This segmentation enables the surface to simultaneously reduce seal torque through roughness-induced oil film formation and support high-speed operation by preventing excessive heat buildup across the entire contact area.
Solution Approach 2:
Different circumferential portions of the seal sliding surface are given different surface roughness qualities. Specifically, high-roughness regions (Ry ≥ 3.0 μm) are positioned at specific locations while low-roughness regions (Ry < 3.0 μm) occupy other circumferential zones. This local quality differentiation allows the high-roughness areas to effectively trap oil and reduce seal torque, while the low-roughness areas minimize friction and heat generation during high-speed rotation, thereby resolving the contradiction between torque reduction and speed capability.
2Ease of manufacture
If the seal lip is molded with the parting line at the distal edge, then manufacturing is simplified, but burrs form at the distal edge during operation
Solution Approach 1:
The parting line position is asymmetrically shifted from the distal edge of the seal lip to a location closer to the base of the seal lip. This asymmetric positioning ensures that the distal edge, which is the critical sealing surface, is formed by a single mold half rather than being at the mold parting line. Consequently, the distal edge does not generate burrs during molding or operation, while the asymmetric parting line location still allows for practical mold design and assembly.
3Force
If non-contact seal members are used to eliminate seal torque, then torque is reduced to zero, but foreign objects larger than a predetermined diameter cannot be effectively prevented from entering the bearing
Solution Approach 1:
The invention merges the characteristics of contact seals and non-contact seals into a hybrid approach. The seal lip maintains light contact with the seal sliding surface (providing sealing action against foreign objects), while the high-roughness portions of the seal sliding surface trap oil to form lubricating films that reduce seal torque. This combination allows the seal to simultaneously achieve foreign object prevention capability and reduced torque, resolving the contradiction between these two requirements.
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 achieves near-zero seal torque, reduces heat buildup, and allows for higher operational speeds while preventing burr formation and entry of foreign objects larger than 50 micrometers, enhancing the bearing's operational lifespan and efficiency.
Implementation Method 1
the protrusions are shaped and arranged such that fluid lubricating condition can be created between the seal lip and the seal sliding surface
Implementation Method 2
promoting the formation of oil film between the seal lip and the seal sliding surfaces by lubricating oil trapped in the recesses of the minute undulations
Data Source
Figure 1
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AI summary
A seal lip (151) has protrusions (152) which define, between the seal lip (151) and a seal sliding surface (112) that slides in the circumferential direction relative to the protrusions (152), oil passages (170) through which a bearing interior space communicates with the exterior of the bearing such that foreign objects having particle diameters larger than a predetermined value cannot pass therethrough. As the bearing rotates, lubricating oil in the oil passages (170) is pulled into spaces between the seal lip (151) and the seal sliding surface (112), so that oil film forms easily therebetween. To prevent burrs from being produced at the distal edge (153) of the seal lip (151), the seal lip (151) has a flat surface (155) between the protrusions (152) and the distal edge (153) of the seal lip.