Toroidal Roller Bearing for Crankshaft Misalignment
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Solution Overview
Problem
Crankshaft assemblies supported by rolling element bearings face issues with increased friction, noise, and vibration due to misalignment and radial offsets, leading to reduced bearing life.
Innovation Solution
The use of toroidal roller bearings with a specific radius of curvature relative to the pitch circle diameter and logarithmically curved edge profiles on split outer ring halves minimizes edge stresses, reduces friction, and allows for self-alignment, accommodating radial offsets and misalignment, thereby reducing noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rolling element bearings are used to support the crankshaft, then friction is reduced, but misalignment and radial offsets lead to reduced bearing life
Solution Approach 1:
The bearing employs toroidal rollers with a specific radius of curvature (R between 1.5D and 2.5D, where D is the pitch circle diameter) that matches the curvature of the raceways. This curved geometry allows the rollers to conform to misaligned surfaces and accommodate radial offsets while maintaining smooth rolling contact, thereby preserving bearing life despite alignment variations.
Solution Approach 2:
The bearing design incorporates a maximum radial clearance of 0.03-0.08mm (specifically 0.045-0.065mm) and a specific toroidal curvature ratio, which are optimized parameters that enable the bearing to accommodate misalignment and radial offsets while maintaining low friction operation and extended service life.
2Ease of manufacture
If the outer ring is split into two halves for assembly, then installation is easier, but radial mismatch at the interface causes noise and vibration
Solution Approach 1:
The adjoining edges of the split outer ring halves are provided with a curved profile having logarithmic curvature formed by electrochemical machining. This curved transition eliminates sharp edges and creates a smooth rolling surface that prevents impact noise and vibration when rollers pass over the interface, while still allowing the halves to be assembled separately.
Solution Approach 2:
The logarithmically curved profile acts as an intermediary transition zone between the two outer ring halves. This curved interface serves as a mediator that smooths out the discontinuity at the joint, allowing rollers to transition smoothly from one half to the other without encountering abrupt edges that would generate noise and vibration.
Data Source
AI summary
The invention relates to an assembly providing a crankshaft having a shaft section that is rotationally supported by a rolling element bearing having an outer ring that is radially divided into two ring halves. To reduce friction and accommodate misalignment, the invention proposes that the bearing which supports the shaft section is a toroidal roller bearing.