A Supplement to Deterioration Process of AgPd Brush and Au-plated Slip-ring System with Lubricant

The authors have been investigating the deterioration process of Au-plated slip-ring and Ag-Pd brush system with lubricant to realize stable and long lifetime. Through the past tests, it can be made clear that lubricant is very important for long lifetime, and a simple model of the deterioration process was proposed. However, it is still an issue how the lubricant is deteriorated and also what the relation between lubricant deterioration and contact voltage change is. In this paper, the contact voltage waveforms were regularly recorded during the test, and analyzed to obtain the time diagram of peak voltage and standard deviation during one rotation. Based on these results, it is discussed what happens at the interface between ring and brush with the lubricant. The following results are made clear. The fluctuation of voltage waveforms, especially peaks of pulse-like fluctuation occur more easily on minus rings than on plus rings. Further, peak values of the pulse-like fluctuation rapidly decreases and disappear at lower rotation speed as mentioned in the previous works. In addition, it can be made clear that each peak of the pulse-like fluctuation is identified at each position of the ring periphery. From these results, it can be said that lubricant film between brush and ring surface has an important role for voltage fluctuation and electric conduction is realized mainly by tunnel effect. In other words, the fluctuation would be caused by the combination of lubricant layer and ring surface roughness. Finally, an electric conduction model is proposed and the above results can be explained by this model.