Half Thrust Bearing Profile for Crankshaft Bending Relief
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Solution Overview
Problem
Crankshafts in internal combustion engines have reduced axial diameter and lower rigidity, leading to increased bending and vibration, which causes the slide surface near the circumferential center of the half thrust bearing to contact the thrust collar surface, resulting in damage (fatigue).
Innovation Solution
A half thrust bearing with an approximately semi-annular shape, featuring a constant bearing wall thickness, an approximately flat center region, and two end regions with curved slide surfaces. The axial distance between the slide surface and a reference surface increases from the center to the circumferential ends, with a difference of 10 to 60 μm, and includes two thrust reliefs and at least one oil groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the crankshaft axial diameter is reduced to decrease engine weight, then the engine weight is reduced, but the crankshaft rigidity decreases and bending deformation increases
Solution Approach 1:
The slide surface is designed with non-uniform thickness distribution, creating different local properties: the circumferential end regions have larger axial distances to accommodate crankshaft bending, while the center region maintains smaller axial distance for optimal load bearing. This local differentiation allows the bearing to adapt to crankshaft deformation while maintaining overall lightweight design.
2Weight of moving object
If the crankshaft rigidity is reduced due to smaller axial diameter, then the engine weight is reduced, but the slide surface near the circumferential center contacts the thrust collar surface causing damage
Solution Approach 1:
The bearing structure proactively compensates for anticipated crankshaft bending by incorporating larger axial distances in the circumferential end regions. This preliminary design feature prevents contact between the slide surface and thrust collar surface before damage can occur, counteracting the harmful effect of reduced crankshaft rigidity.
Solution Approach 2:
Different regions of the slide surface have different axial distances from the reference surface. The circumferential end regions have larger axial distances to prevent contact under bending conditions, while the center region maintains smaller axial distance for efficient load bearing. This local differentiation resolves the contradiction between lightweight design and reliability.
3Stress or pressure
If a crowning surface with curved shape is provided on the outer diameter side of the slide surface, then local contact stress is reduced, but the slide surface near the circumferential center still contacts the thrust collar surface when vibration is great
Solution Approach 1:
The axial distance from the reference surface is made non-uniform across different circumferential positions. The circumferential end regions have larger axial distances to prevent contact under vibration and bending, while the center region maintains smaller axial distance. This local differentiation effectively prevents contact damage while distributing contact stress.
Data Source
AI summary
There is provided a half thrust bearing having a constant bearing wall thickness between a slide surface and a back surface, and including an approximately flat center region and two end regions on both circumferential sides of the center region. Each end region extends from each circumferential end of the half thrust bearing toward a circumferential center over a circumferential angle of 5° or more and 35° or less. A reference surface is defined as an imaginary plane which is perpendicular to an axial direction of the half thrust bearing, parallel to the slide surface in the center region, and located away from the slide surface. An axial distance between the slide surface and the reference surface is minimum in the center region, and continuously increases circumferentially from a center region side toward a circumferential end side at any radial position in each end regions.