Needle Roller Cage With Relief Portions For Lubrication
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Solution Overview
Problem
The existing needle roller and cage assemblies for planetary gear mechanisms face issues with complex assembly processes due to multiple roller rows, stress concentration leading to edge stress, inadequate lubrication, and friction between the cage and pinion surfaces, which shorten the bearing's life and complicate lubricant distribution.
Innovation Solution
A needle roller and cage assembly with needle rollers arranged in a single row and a cage width larger than its diameter, featuring annular sections, pillar sections with oblique relief portions, and rectangular pockets with extended second relief portions to improve lubrication and reduce assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If multiple roller rows are arranged to extend bearing life, then the bearing life is improved, but the assembly complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The invention transitions from increasing bearing life through multiple roller rows (radial dimension) to using a single roller row with increased roller length (axial dimension). The cage width is made larger than its diameter, creating a wide-flange structure that accommodates longer rollers in a single row, thereby extending bearing life without increasing assembly complexity.
Solution Approach 2:
The invention changes the geometric parameters of the cage and rollers: the cage width B is made larger than the cage diameter D (B>D), creating a wide-flange structure. The roller length L is increased relative to the roller diameter. These parameter changes allow a single roller row to provide the bearing life equivalent to multiple rows without the associated assembly complexity.
2Duration of action of stationary object
If roller length is increased to extend bearing life, then bearing life is improved, but skew and edge stress increase
Solution Approach 1:
The invention provides lateral support for the long rollers by increasing the cage width in the radial direction (creating wide flanges). This dimensional change in the cage structure prevents roller skew and maintains roller strength despite the increased roller length, thereby extending bearing life without compromising structural integrity.
3Strength
If relief portions are formed with arc shape through drilling or milling, then stress concentration is relieved, but the lubrication capability to roller end portions is insufficient
Solution Approach 1:
The invention changes the geometry of the relief portions from arc-shaped (formed by drilling/milling) to rectangular shapes with extended dimensions. The second relief portions extend in the axial direction of the cage, creating larger openings that improve lubricant flow to the roller end portions while still relieving stress concentration at the pocket corners.
4Duration of action of stationary object
If cage width is increased to accommodate longer rollers, then bearing life is extended, but friction between cage and pinion surfaces increases
Solution Approach 1:
The invention applies local quality by creating rectangular relief portions at specific locations (cage corners and pocket openings) that allow lubricant access. This localized modification reduces friction at critical contact points between the cage and pinion surfaces, enabling the wider cage design to extend bearing life without excessive friction increase.
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 life of the needle roller and cage assembly by simplifying assembly, reducing skew, enhancing lubrication, and forming an oil film to reduce friction, thereby improving the bearing's performance and longevity.
Implementation Method 1
The needle roller and cage assembly utilizes an outer circumferential surface of the pinion shaft 8a as an inner raceway surface and an inner circumferential surface of the pinion 6 as an outer raceway surface... The planetary gear mechanism often has structure of lubricating in the needle roller and cage assembly 10 by drawing-in the lubricating oil through the oil lubrication hole 8b formed in the pinion shaft 8a
Data Source
AI summary
A needle roller and cage assembly include a cage having a width larger than a diameter thereof. Pillar sections of the cage each include roller retaining portions on radially inner and outer sides with respect to a roller pitch circle diameter and an oblique portion through which the roller retaining portions are continuous with each other. The oblique portion includes a first relief portion formed therein, for avoiding interference with a needle roller. The adjacent pillar sections form a pocket having a rectangular shape therebetween. The pocket includes a second relief portion in each of four corners thereof. The second relief portion extends in the axial direction of the cage from a position at which a short side of the pocket is elongated in a circumferential direction of the cage to an outer end of the roller retaining portion on the radially outer side.