Effect of Lubricant on Lifetime of Au-Plated Slip-Ring and Ag-Pd-Cu Brush System for Small Electric Power

Koichiro SAWA  Yasunori SUZUKI  Noboru MORITA  Kaoru ENDO  Takahiro UENO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E95-C   No.9   pp.1465-1472
Publication Date: 2012/09/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E95.C.1465
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Development of Electro-Mechanical Devices - Papers selected from International Session on Electro-Mechanical Devices 2011 (IS-EMD2011) and other recent research results -)
Category: 
Keyword: 
slip ring,  Au plating,  Ni base plating,  Ag-Pd brush,  lifetime,  lubricant,  

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Summary: 
The authors have been investigating degradation process of Au plated slip ring and Ag-Pd-Cu brush system. In almost all cases the lifetime of the sliding system ends, when Au plating layer is worn out, the ring surface is oxidized to be black in color and contact resistance becomes very high. Further, the lifetime is very short without lubricant. So, the lubricant is very effective to make the lifetime longer. However, even with lubricant the lifetime is varied from about 1000 hours to almost 7000 hours in the past experiments. It is an important issue how the lubricant works on the lifetime of the system. In this paper the effect of lubricant on the degradation process of contact resistance is focused on. In the past tests the lubricant is supplied only once before the test. In this test the lubricant is regularly supplied almost every 900 operation hours. Consequently, the operation more than 8000 hours is realized, which is the longest among tests so far. In addition the contact voltage drop increase gradually until 2600 hours and after that it stays almost constant around 70 mV. According to the Element Analysis after the test the Ni base plating layer is totally exposed in many tracks. It means that the Au plating layer is gradually worn out probably at the stage of increasing voltage drop. In the previous tests the lifetime ended even when the Ni plating layer remained. So, the reason of long operation in this test is guessed to be that the lubricant not only decreases wear of ring and brush, but also suppresses oxidation of the Ni layer.