Sealed Bearing Lip Protrusions for Low-Torque Sealing
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Solution Overview
Problem
Sealed bearings in automotive transmissions and differentials experience high rotational resistance and excessive temperature rise due to sliding contact between seal lips and inner races, which affects transmission efficiency and fuel efficiency.
Innovation Solution
The sealed bearing design features seal lips with circular arc-shaped protrusions that generate a wedge film effect, reducing rotational resistance and frictional heat by introducing lubricating oil into sliding contact areas, thereby creating a fluid lubrication condition and minimizing direct contact between seal lips and inner/outer races.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If seal lips are in sliding contact with the inner race to prevent foreign matter entry, then sealing performance is improved, but rotational resistance (seal torque) increases and temperature rises excessively
Solution Approach 1:
The seal lip is segmented into multiple protrusions (at least three) circumferentially spaced apart, each with a circular arc-shaped cross-section. This segmentation creates multiple lubrication zones that reduce rotational resistance while maintaining sealing effectiveness through the combined action of all protrusions.
Solution Approach 2:
Each protrusion has a circular arc-shaped cross-section with a specific radius (0.4 mm or more and less than 9.0 mm), creating a curved surface that effectively introduces lubricating oil into the sliding contact portion. This curvature generates a wedge film effect that reduces friction and seal torque while maintaining the sealing function.
2Reliability
If seal lips are in sliding contact with the inner race to maintain sealing, then foreign matter prevention is improved, but frictional heat generation increases causing excessive temperature rise
Solution Approach 1:
The seal lip is divided into multiple protrusions that create distributed lubrication zones, reducing concentrated frictional heat generation. The segmented structure allows lubricating oil to be introduced at multiple points, effectively cooling the sealing interface.
Solution Approach 2:
A lubricating oil film is introduced as an intermediary between the protrusions and the inner race surface. This fluid mediator reduces direct metal-to-metal or rubber-to-metal contact, thereby reducing frictional heat generation and preventing excessive temperature rise while maintaining sealing effectiveness.
3Reliability
If protrusions are arranged at small circumferential pitches to ensure oil film thickness, then fluid lubrication is improved, but manufacturing cost increases
Solution Approach 1:
The invention specifies optimal parameter ranges: circumferential pitches of 0.2 mm or more and 3.0 mm or less, and protrusion radii of 0.4 mm or more and less than 9.0 mm. These parameter optimizations ensure effective fluid lubrication while keeping the mold design manageable and manufacturing costs reasonable.
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 significantly reduces seal torque and prevents excessive temperature rise, allowing for higher peripheral speeds and improved bearing performance, while also preventing foreign object entry and reducing manufacturing costs.
Implementation Method 1
due to the wedge film effect, it is possible to generate fluid lubrication condition between the sliding portions
Data Source
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AI summary
A sealed bearing is provided of which the seal torque is small, and of which the temperature is less likely to rise excessively. The sealed bearing includes an inner race (2); and seal members (7) each including a seal lip (10) made of rubber. Each seal lip (10) includes a plurality of protrusions (15) circumferentially spaced apart from each other, and kept in sliding contact with the inner race (2) with fluid lubrication condition generated between the protrusions (15) and the inner race (2). Each protrusion (15) has a circular arc-shaped cross section along the circumferential direction, and the circular arc-shaped cross section has a radius (R) of 0.4 mm or more and less than 9.0 mm.