Hydrodynamic Bearing Roughness for Crankshaft Accommodation
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Solution Overview
Problem
Existing hydrodynamic bearings in internal combustion engines face stress and wear issues due to high oil pressure, particularly peak oil pressure, which affects their durability and reliability, especially in high-loaded engines, and prior solutions have not effectively addressed these challenges.
Innovation Solution
A hydrodynamic bearing with a sliding material having a higher average maximum roughness value (Rz) is designed to accelerate the accommodation of the crankshaft, reducing oil film pressure and increasing the useful life of the bearings by intentionally promoting accelerated wear in the first oil contact portion, allowing for the use of less stress-resistant, cheaper bearings without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrodynamic bearings are made with smooth sliding material surface, then direct contact between crankshaft and bearing is avoided, but accommodation of crankshaft is delayed and wear issues occur
Solution Approach 1:
The bearing surface is pre-conditioned with a specific roughness profile (Rz 3-10 μm) before operation to facilitate accelerated crankshaft accommodation during the run-in period, while maintaining smooth operation thereafter
Solution Approach 2:
Different surface quality requirements are applied to different regions: the sliding material has controlled roughness (Rz 3-10 μm) for accelerated accommodation, while the overlay layer maintains smoothness for low friction during normal operation
2Reliability
If hydrodynamic bearings use higher stress-resistant materials, then durability under high oil pressure is improved, but manufacturing cost increases
Solution Approach 1:
The bearing uses a composite structure with a sintered iron base material (providing mechanical strength and stress resistance) combined with a babbitt alloy overlay layer (providing low friction and wear resistance), achieving both durability and cost-effectiveness
Solution Approach 2:
The sliding material uses controlled porosity (20-40%) in the sintered iron structure to optimize both mechanical properties and lubricant retention, reducing the need for expensive high-strength materials
3Stress or pressure
If sliding material has higher roughness value, then crankshaft accommodation is accelerated and oil film pressure is reduced, but wear of sliding material increases
Solution Approach 1:
The bearing surface is pre-conditioned with a specific roughness profile (Rz 3-10 μm) before operation to facilitate accelerated crankshaft accommodation during the run-in period, while maintaining smooth operation thereafter
Solution Approach 2:
The babbitt overlay layer is designed as a sacrificial element that wears preferentially during the run-in period to accommodate the crankshaft, protecting the more expensive sintered iron substrate
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 solution reduces peak oil film pressure and stress on the bearings, enabling the use of bimetallic bearings in high-loaded engines, increasing their durability and extending their useful life while maintaining efficient operation.
Implementation Method 1
a higher average maximum roughness value (Rz) of its surface leads to an accelerated wear of the sliding material in the first oil contact portion (3)
Implementation Method 2
The hydrodynamic bearings are dynamic bearings wherein the fluid lubricant is a liquid (a lubricant oil), which avoid the direct contact between the surfaces of the rotatable axle and the support
Implementation Method 3
The axle 'floats' by the effect of the hydrodynamic pressure of the oil film, avoid touching the surface of the bearing
Data Source
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Figure 3
AI summary
The present invention describes a hydrodynamic bearing (1) for an internal combustion engine. More particularly, the present invention relates to a bearing composed of a sliding material which its average maximum roughness value leads an accelerated wear of the sliding material and an accelerated accommodation of a crankshaft during engine operation.