Oil-Impregnated Sintered Bearing Pore Distribution
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Solution Overview
Problem
Oil-impregnated sintered bearings used in electric motors, especially those used intermittently like window regulators, tend to produce squealing noises due to insufficient lubrication, as the fluid permeability necessary for smooth operation often leads to oil leakage, and the existing methods struggle to balance open porosity and fluid permeability to prevent both noise and lubrication issues.
Innovation Solution
The solution involves an oil-impregnated sintered bearing with a specific pore size distribution, including middle-sized and large-sized pores, and a production method using porous iron powders with controlled particle size distributions to maintain sufficient lubrication without increasing fluid permeability, ensuring a reliable oil film is formed between the shaft and the bearing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fluid permeability is increased by increasing the density of an oil-impregnated sintered bearing, then the lubrication supply is improved, but the open porosity is decreased and oil-retaining characteristics are degraded
Solution Approach 1:
The invention segments the pore structure into two distinct types: microscopic pores (0.1-10 μm) within iron powder particles for oil retention, and macroscopic pores (>10 μm) between particles for lubrication supply. This segmentation allows each pore type to fulfill its specific function optimally without compromising the other.
Solution Approach 2:
The invention applies local quality by creating different pore size distributions in different locations and contexts: microscopic pores are distributed throughout the iron phase for local oil storage, while macroscopic pores are positioned at the sliding surface for local oil supply. This spatial differentiation of pore qualities resolves the contradiction between retention and supply.
2Quantity of substance
If the open porosity is increased to improve oil-retaining characteristics, then the oil retention is improved, but the fluid permeability is increased causing oil leakage
Solution Approach 1:
The pore structure is segmented into microscopic pores for oil retention and macroscopic pores for controlled supply. The microscopic pores (0.1-10 μm) provide high surface area for oil holding, while the limited number of macroscopic pores (>10 μm) control the permeability to prevent excessive leakage.
Solution Approach 2:
The invention changes the pore size parameter distribution by introducing a bimodal distribution with most pores being microscopic (0.1-10 μm) and only a small fraction being macroscopic (>10 μm). This parameter change allows high open porosity (30-50%) while maintaining low fluid permeability through the dominance of fine pores.
3Ease of operation
If a high fluid permeability is used to ensure smooth operation, then the lubrication flow is improved, but squealing noises are produced during sliding in cold climates
Solution Approach 1:
The invention creates local quality differences in the pore structure: microscopic pores distributed throughout the bulk provide oil reservoirs, while a controlled number of macroscopic pores at the sliding surface provide localized oil supply paths. This ensures adequate lubrication flow to prevent squealing without creating excessive permeability that would cause oil loss.
4Object-generated harmful factors
If the number of pores is decreased to reduce fluid permeability, then the squealing noises are prevented, but the open porosity is decreased and oil-retaining characteristics are degraded
Solution Approach 1:
The pore population is segmented by size: numerous microscopic pores (0.1-10 μm) maintain high open porosity for oil retention, while the total number of macroscopic pores (>10 μm) is limited to control fluid permeability. This segmentation allows high porosity (30-50%) coexisting with low permeability, preventing squealing while retaining oil.
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 approach effectively prevents squealing noises by ensuring adequate lubrication at startup and during operation, even in cold climates, by controlling pore sizes and distributions to optimize oil retention and supply, thus enhancing the bearing's performance and reliability.
Implementation Method 1
by using a porous reduced iron powder as an iron powder, an enormous number of microscopic pores are arranged in an iron phase of the oil-impregnated sintered bearing, whereby the open porosity is increased
Implementation Method 2
the fluid permeability affects leakage characteristics of lubricating oil and oil pressure at a sliding surface
Data Source
AI summary
The oil-impregnated sintered bearing made of iron-copper sintered alloy consisting of 10-59% of Cu, 0.5-3% of Sn, and balance of Fe and impurities, includes pores in the iron-copper sintered alloy matrix of not less than 800 per mm2, has pores exposed at 20-50% by area ratio at the inner circumferential surface with diameters greater than 100 μm, not more than 0.5%, respectable to the total pores number. The pores number with diameters greater than 80 μm and not greater than 100 μm, not more than 0.1%, respectable to the total pores number with diameters greater than 60 μm and not greater than 80 μm is 0.5-1.5%, respectable to the total pores number, with diameters greater than 40 μm and not greater than 60 μm is 0.8-3% respectable to the total pores number, and the remainder pores are with diameters less than 40 μm.