Half Thrust Bearing with Inclined Surface Portions
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Solution Overview
Problem
The reduced diameter of modern crankshafts in internal combustion engines leads to lower rigidity, causing deflection and increased vibration, resulting in damage (seizure) and high friction loss due to uneven contact between the thrust collar surface and the half thrust bearing, especially when misalignment occurs during assembly.
Innovation Solution
A half thrust bearing with a semi-annular shape featuring a flat surface portion parallel to a reference plane and inclined surface portions on both sides, where the axial distance is maximum at the central portion and reduces towards the circumferential ends, preventing continuous contact between the sliding surface and the thrust collar surface, and maintaining a suitable circumferential length of the flat surface portion to minimize friction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the crankshaft diameter is reduced to decrease engine weight, then the engine weight is reduced, but the crankshaft rigidity decreases causing deflection and vibration
Solution Approach 1:
The sliding surface of the half thrust bearing is designed with non-uniform thickness, being thickest at the circumferential center and thinner toward the end surfaces. This local variation in geometry compensates for the reduced overall crankshaft rigidity by providing enhanced load-bearing capacity at the critical contact region, allowing the crankshaft to be lighter while maintaining sufficient local strength to resist deflection and vibration.
2Ease of operation
If the crankshaft rigidity is low causing deflection, then the crankshaft can rotate more freely, but the thrust collar surface becomes inclined causing uneven contact and seizure
Solution Approach 1:
The sliding surface incorporates thrust reliefs at the end surfaces that create a localized thinning pattern. This allows the central portion of the sliding surface to maintain optimal contact with the thrust collar surface even when the crankshaft deflects, while the relieved end portions accommodate the inclination caused by deflection, preventing seizure and ensuring reliable operation.
Solution Approach 2:
The thrust relief geometry is designed in advance to anticipate and compensate for the inclination that will occur during crankshaft operation. By pre-shaping the sliding surface with appropriate thickness variations, the bearing ensures uniform contact distribution even when the crankshaft experiences deflection and vibration during operation.
3Force
If the sliding surface contacts the thrust collar surface continuously, then the axial force is supported, but friction loss increases and damage occurs
Solution Approach 1:
The sliding surface is designed with spatially varying thickness, creating regions of different contact pressure. The thickest region at the circumferential center provides primary axial force support, while the progressively thinner regions toward the end surfaces reduce contact pressure and friction, allowing the bearing to support the required load with minimized energy loss.
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 prevents damage (seizure) by ensuring the sliding surface does not continuously contact the thrust collar surface and reduces friction loss by avoiding direct contact with the circumferentially central portion during axial vibration, effectively managing the inclination of the thrust collar surface.
Implementation Method 1
the sliding surface comes into direct contact with the thrust collar surface of the crankshaft
Implementation Method 2
a sliding surface for receiving the axial force
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
A half thrust bearing (8) having a semi-annular shape includes a sliding surface (81) for receiving an axial force (f) of a crankshaft of an internal combustion engine, and a rear surface (84a) on an opposite side of the sliding surface, and defines a reference plane (84) on the rear surface (84a) side that is perpendicular to an axial direction. The sliding surface includes a flat surface portion (81a) near a circumferentially central portion (85) and in parallel with the reference plane (84), and inclined surface portions (81b) on both sides of the flat surface portion in a circumferential direction. At any radial positions of the half thrust bearing, an axial distance between the reference plane and the sliding surface is maximum at the flat surface portion, and is reduced in the inclined surface portions toward both circumferential end portions (86) of the half thrust bearing.