Asymmetrical Thrust Bearing Relief for Crankshaft Lubrication
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Solution Overview
Problem
The reduction in size of oil pumps for internal combustion engines leads to decreased lubrication oil supply, causing increased crankshaft deformation and vibration, which results in potential seizure issues at the sliding surface of half thrust bearings due to reduced lubrication and increased axial forces.
Innovation Solution
A thrust bearing design featuring a pair of semi-annular half thrust bearings with asymmetrical thrust reliefs, where the rear-side thrust relief is longer than the front-side relief, enhancing lubrication oil retention and distribution to prevent direct contact with the crankshaft's thrust collar, thus maintaining high load capability and reducing seizure risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the oil pump size is reduced, then the overall engine size and complexity are reduced, but the lubrication oil supply amount decreases causing insufficient lubrication and increased seizure risk
Solution Approach 1:
The invention applies local quality by creating asymmetrical thrust reliefs with different lengths at the front and rear of the sliding surface. The rear thrust relief is designed longer than the front thrust relief to specifically address the lubrication deficiency in the rear region where lubrication oil naturally flows away. This localized structural modification ensures adequate lubrication oil retention at the critical rear sliding surface area without requiring an increase in overall oil pump size.
Solution Approach 2:
The invention directly applies asymmetry by designing thrust reliefs with unequal lengths - the rear thrust relief extends further than the front thrust relief. This asymmetrical configuration matches the natural flow direction of lubrication oil, allowing the longer rear relief to capture and retain oil that would otherwise escape, thereby maintaining reliable lubrication with reduced oil pump capacity.
2Weight of moving object
If the crankshaft diameter is reduced to decrease weight, then the engine weight is reduced, but the crankshaft rigidity decreases causing increased deformation and vibration
Solution Approach 1:
The invention converts the harmful effect of crankshaft deformation and vibration into a beneficial outcome by designing the asymmetrical thrust relief configuration to accommodate and compensate for these deformations. The longer rear thrust relief specifically compensates for the increased vibration and deformation in the rear region, ensuring that even with reduced crankshaft diameter, the sliding surface maintains adequate lubrication and prevents seizure.
3Reliability
If the thrust relief length is increased to improve lubrication retention, then the lubrication oil supply to sliding surface is improved, but the load-bearing area of the bearing is reduced
Solution Approach 1:
The invention applies local quality by selectively extending only the rear thrust relief while keeping the front thrust relief shorter. This localized extension focuses the lubrication retention enhancement specifically where needed (rear sliding surface) without unnecessarily reducing the load-bearing area across the entire bearing surface, thus maintaining an optimal balance between lubrication retention and load-bearing capacity.
Solution Approach 2:
The asymmetrical thrust relief design allows differential optimization - the rear thrust relief is extended to improve lubrication retention in the critical rear region, while the front thrust relief maintains a shorter length to preserve load-bearing area. This asymmetrical approach achieves improved lubrication without proportionally sacrificing load-bearing capacity.
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
The asymmetrical thrust relief configuration ensures adequate lubrication oil supply to the sliding surface, preventing direct contact with the crankshaft's thrust collar and maintaining high load-bearing capacity even under deformation and vibration, thereby reducing the risk of seizure and ensuring reliable operation.
Implementation Method 1
The asymmetrical thrust relief configuration ensures adequate lubrication oil supply to the sliding surface, preventing direct contact with the crankshaft's thrust collar
Data Source
AI summary
A thrust bearing for receiving an axial force of a crankshaft of an internal combustion engine. The thrust bearing includes a pair of half thrust bearings having a semi-annular shape that form an annular shape by abutting their circumferential end surfaces. Each half thrust bearing include thrust reliefs formed adjacent to both circumferential end portions of a sliding surface receiving the axial force so that a wall thickness is thinner toward the circumferential end surface. A thrust relief length L2 at an inner end portion of the thrust relief positioned on a rear side of one of the half thrust beings in a rotational direction is larger than a thrust relief length L1 at an inner end portion of the thrust relief positioned on a front side of the other of the half thrust bearing in the rotational direction.