Sintered Bearing Composition Using Flat Copper and Liquid Phase Sintering
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Solution Overview
Problem
Existing sintered bearings face challenges in achieving a balance between sliding characteristics, wear resistance, and strength, particularly due to insufficient neck strength between the iron and copper phases, leading to fretting wear and deformation issues when used in applications like automobile starters and vibration motors.
Innovation Solution
A method of manufacturing a sintered bearing using a composition of iron, copper, and a low-melting point element like tin, zinc, or phosphorus, with a surface layer of sintered flat copper powder and a base part formed by partially diffusion-alloyed powder, which enhances bonding strength and prevents fretting wear through liquid phase sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If copper-iron-based sintered bearing with copper-covered iron powder is used, then sliding characteristics are improved, but neck strength between iron phase and copper phase is insufficient causing early wear
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific low-melting point elements (Bi, Pb, Zn, Sn, or Ag in controlled amounts) to the copper-iron powder mixture. This modifies the sintering process and creates a eutectic structure that simultaneously improves sliding characteristics through lubricating elements and neck strength through enhanced bonding, resolving the contradiction between ease of operation and strength.
Solution Approach 2:
The invention creates a composite material system combining iron powder, copper powder, and low-melting point element powder. The low-melting point elements form eutectic structures at the interfaces between iron and copper phases, creating a multi-phase composite that provides both excellent sliding characteristics (from the low-melting point elements) and high neck strength (from the eutectic bonding structure).
2Strength
If iron-based sintered bearing with large Fe content is used, then strength is improved, but fretting wear increases due to oxidation and surface structure escape
Solution Approach 1:
The low-melting point elements (Bi, Pb, Zn, Sn, or Ag) act as intermediary substances between the iron phase and the environment. During sintering, these elements form protective surface layers and eutectic structures that prevent direct oxidation of the iron phase. This intermediary layer reduces fretting wear by preventing surface structure escape while maintaining the high strength provided by the iron phase.
3Reliability
If copper-based sintered bearing is used, then fretting wear is prevented, but bearing strength is insufficient causing deformation under vibration
Solution Approach 1:
The invention creates a composite material system combining iron powder (for strength), copper powder (for fretting wear resistance), and low-melting point element powder (for bonding enhancement). The resulting multi-phase composite simultaneously achieves high bearing strength from the iron phase, excellent fretting wear resistance from the copper and low-melting point elements, and improved neck strength from the eutectic structures formed during sintering.
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 method results in a sintered bearing with improved sliding characteristics, wear resistance, and strength, reducing fretting wear and deformation, while maintaining cost-effectiveness for various applications.
Implementation Method 1
a sintered bearing formed by sintering raw material powder which comprises partially diffusion-alloyed powder, in which a number of grains of copper powder is partially diffused on a surface of an iron powder
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
A sintered bearing (1) contains as main components iron, copper, a metal having a lower melting point than copper, and a solid lubricant. The sintered bearing (1) includes a surface layer (S1) and a base part (S2). The surface layer (S1) is formed mainly of flat copper powder arranged so as to be thinned in a thickness direction. In the base part (S2), an iron structure (33) and a copper structure (31c) brought into contact with the iron structure are formed of partially diffusion-alloyed powder in which copper powder is partially diffused in iron powder. Thus, a sintered bearing which achieves a balance between wear resistance of a bearing surface and strength of the bearing, and realizes low cost can be provided.