Half Thrust Bearing Ridge Geometry for Crankshaft Seizure Prevention
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Solution Overview
Problem
Existing half thrust bearings for crankshafts in internal combustion engines suffer from seizure due to direct contact between the slide surface and the thrust collar surface, especially when crankshaft vibration increases, despite previous attempts to form high-pressure oil films using inclined surfaces and oil grooves.
Innovation Solution
A semi-annularly shaped half thrust bearing with radially extending oil grooves and symmetrical inclined surfaces, featuring ridge portions that vary in circumferential length and axial thickness, to enhance oil retention and pressure, preventing direct contact between the slide surface and the thrust collar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the crankshaft diameter is reduced for weight saving, then the weight of the crankshaft is reduced, but the rigidity of the crankshaft decreases and vibration increases
Solution Approach 1:
The slide surface is divided into multiple pad portions rather than being a single continuous surface. This segmentation allows the bearing to better accommodate crankshaft vibration while maintaining load-bearing capability, effectively addressing the rigidity issue without requiring increased crankshaft diameter.
Solution Approach 2:
Oil grooves and inclined surfaces are introduced as intermediary structures between the pad portions. These features generate high-pressure oil films that act as a mediator to prevent direct contact between the crankshaft and bearing surface, compensating for the reduced rigidity of the lightweight crankshaft.
2Device complexity
If the slide surface directly contacts the thrust collar surface, then the bearing structure is simple, but seizure occurs due to increased vibration and direct contact
Solution Approach 1:
The slide surface is segmented into multiple pad portions with oil grooves between them. This segmentation prevents direct contact over the entire surface, reducing the risk of seizure while maintaining a relatively simple overall bearing structure.
Solution Approach 2:
The bearing utilizes hydrodynamic lubrication through oil grooves and inclined surfaces to generate high-pressure oil films. This hydraulic mechanism separates the crankshaft from the bearing surface, preventing seizure without requiring complex mechanical structures.
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 design effectively maintains a high-pressure oil film, reducing the likelihood of seizure by ensuring sufficient oil flow and pressure distribution, even under increased crankshaft vibration.
Implementation Method 1
providing a plurality of pad portions on the slide surface of the half thrust bearing, and providing an oil groove and an inclined surface between the pad portions, thereby forming a high-pressure oil film in a clearance between the inclined surface and the thrust collar surface
Data Source
AI summary
In a half thrust bearing for a crankshaft, a slide surface includes at least two oil grooves extending in a radial direction, pad surfaces located on both circumferential sides of each oil groove, a first inclined surface formed on a forward side of the oil groove in a rotation direction of the crankshaft, and a second inclined surface formed on a backward side of the oil groove in the rotation direction. Each of the first and second inclined surfaces has a circumferential length which varies along the radial direction and includes a ridge portion at a radial position where the circumferential length is minimum. The axial thickness of each of the first and second inclined surfaces is maximum at the ridge portion in the radial direction and become smaller from the ridge portion toward a radially inner end and toward a radially outer end.