Double Row Ball Bearing Shield for Foreign Object Protection
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Solution Overview
Problem
Double row ball bearings in differential gear mechanisms face reduced service life due to foreign objects from lubricant getting caught between balls and raceway grooves, leading to surface exfoliation and increased torque loss.
Innovation Solution
A double row ball bearing design featuring an annular portion that covers the second balls radially outward, reducing lubricant flow and preventing foreign objects from entering the bearing, combined with a 'flow-rate reducer' clearance to minimize lubricant volume and centrifugal discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pitch circle diameter of the second ball row is made larger than the first ball row to reduce torque loss, then bearing efficiency is improved, but the inner peripheral surface of the outer ring becomes tapered which generates lubricant flow that carries foreign objects into the bearing
Solution Approach 1:
A shield member is introduced as an intermediary component between the lubricant flow path and the second balls. The shield member has a shield surface that faces the lubricant flow and blocks foreign objects contained in the lubricant from reaching the second balls and raceway grooves, while allowing the lubricant flow pattern to remain unchanged for torque reduction purposes.
Solution Approach 2:
The shield member utilizes the existing lubricant flow generated by the tapered outer ring surface (which causes the harmful effect) and redirects it beneficially by allowing clean lubricant to reach the bearing while blocking only the foreign objects. The same flow that carries contaminants is now used to deliver clean lubricant to the bearing surfaces.
2Reliability
If more lubricant flows through the internal space of the bearing to ensure proper lubrication, then lubrication quality is improved, but the likelihood of foreign objects being caught between balls and raceway grooves increases
Solution Approach 1:
The shield member acts as a filter intermediary that separates clean lubricant from foreign objects. It allows the lubricant to flow freely to ensure proper lubrication while intercepting and blocking foreign objects before they can enter the bearing's internal space and cause damage.
3Duration of action of stationary object
If the annular portion covers the second balls to prevent foreign object contamination, then bearing service life is extended, but lubricant flow to the second balls is reduced
Solution Approach 1:
The shield member is positioned specifically at the location where foreign object contamination occurs (facing the lubricant flow path), providing protection only where needed. The shield's extent and positioning are optimized to block foreign objects while maintaining adequate lubricant flow to the second balls through the spaces around the shield.
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 configuration extends the bearing service life by preventing foreign objects from being stuck between the balls and raceway grooves, reducing lubricant flow, and enhancing the 'flow-rate reducer' effect to hinder lubricant discharge, thus improving the overall performance and longevity of the bearing.
Implementation Method 1
minimize lubricant volume and centrifugal discharge
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A double row ball bearing includes: an outer ring (16); an inner ring (15); a plurality of first balls (11) disposed between the outer ring and the inner ring to form a first ball row; a plurality of second balls (12) disposed between the outer ring and the inner ring to form a second ball row having a pitch circle diameter larger than that of the first ball row; an annular first cage (21) having a plurality of first pockets (23) in which the first balls are held; an annular second cage (22) having a plurality of second pockets (24) in which the second balls are held; and an annular portion (30) that covers, together with the outer ring, a portion of each second ball held in the second pocket from the radially outside, the portion being exposed on the outside of the second pocket and oriented radially outward.