Naruhiko Inayoshi

Development of New In Situ Observation System for Dynamic Study of Lubricant Molecules on Metal Friction Surfaces by Two-Dimensional Fast-Imaging Fourier-Transform Infrared-Attenuated Total Reflection Spectrometer

To observe the time-dependent two-dimensional (2D) images of spatial distribution of chemically/physically modified lubricant molecules on the metal surface during friction motion, a new in situ technique has been developed by combining the 2D fast-imaging Fourier-transform infrared-attenuated total reflection spectrometer with the temperature-controlled friction equipment containing lubricant agent. Using this new instrument, the time-dependent changes in lubricant molecules, for example, cis-trans isomerization, stress-induced molecular deformation, etc., can be detected successfully. The characteristic features of this instrument have been demonstrated in a detailed and concrete manner by demonstrating the experimental data measured for oleic acid and tricresyl phosphate.

Relationship between electrical-tribological behavior and properties of sliding surfaces of copper containing diamond-like carbon nanocomposite coated plate and brass ball

Reducing the electrical contact resistance (ECR) and the coefficient of friction (CoF) are major technological requirements for sliding contacts. This report provides electrical-tribological characteristics of a Copper containing Diamond-like Carbon (Cu-DLC) nanocomposite coating deposited on a brass plate, investigated by using a ball/plate reciprocating tribometer. The counterpart was a brass ball. While the initial ECR was hundreds of milliohms, it gradually decreased with cycles and reached approximately 2 milliohms after 600 cycles. CoF started below 0.35 and decreased progressively, and stabilized around 0.25 after 600 cycles. The good electrical-tribological characteristics lasted up to approximately 7500 cycles and CoF increased rapidly after. Sliding surfaces at different cycles were analyzed by optical microscope, laser-scanning microscope, EDX, TEM and nanoindentation. The results of analyses revealed that a copper-rich tribofilm was built up on the ball, which grew with cycles. The Cu-DLC wore gradually and its substrate was exposed after less than 1000 cycles. Nevertheless, detrimental effects were not observed either on ECR or on CoF up to 7500 cycles. The unique structures and properties of the tribofilm and the worn Cu-DLC surface are discussed, attempting to account for their key roles on the good characteristics.

Development of the lead-free brush material for the high-load starter

Carbon brushes for automotive starters are used under severe conditions of high electrical current density, high contact pressure and high sliding velocity. Lead has traditionally been added to carbon brushes to improve their performance and durability. Because lead is an environmental hazardous substance, after January 2005 the EU has prohibited adding lead to carbon brushes for electric motors installed in new vehicles. This paper reports the development of the lead-free brush material for the high-load starter. Those brushes are used in much more extreme conditions - at a PV-value (the product of brush contact pressure and sliding velocity) approximately three times that of other starter brushes, and double the electrical current density. The major technical requirement of this development was to decrease the electrical wear in brushes caused by commutation sparking. We developed the brush material that reduces electrical wear by adding a phosphorous compound. Because the phosphorous compound can improve the lubricity at high-temperature and the contact stability of brushes, the developed brush reduces commutation sparks. The life of the developed brush is about 1.5 times longer than that of conventional brushes containing lead.

The Development of the Lead Free Carbon Brush for Starters

Carbon brushes for automotive starters are used under severe conditions of high electric current density, high contact pressure and high sliding velocity. Therefore lead has traditionally been added to brushes to improve performance and durability. Lead is an environmental hazardous substance. In the EU, the law prohibits adding lead to brushes for electric motors which is installed on new automobiles in and after January 2005. In order to develop the lead free carbon brush for starters, we analyzed the effect and selected substitutive substance of lead. Adding lead to the brush reduces the electric resistance increase of the brush in high-temperature and high-humidity atmosphere and in high-temperature atmosphere. Furthermore lead reduces the wear amount of brush. We developed the lead free brush surpassing the lead addition brush in performance and durability by addition of lead alternatives silver and zinc.

Development of the Lead-Free Carbon Brush Material for Starters

Carbon brushes for starters are used under severe conditions of high electric current density, high contact pressure and high sliding velocity. Lead has traditionally been added to carbon brushes to improve their performance and durability. Because lead is an environmentally hazardous substance, after January 2005 the EU will prohibit adding lead to carbon brushes for electric motors installed in vehicles. The purpose of our current study is to develop materials of lead-free carbon brushes for starters. Analyzing the effects of adding lead has shown that lead inhibits the brush resistance from increasing under high temperatures, or a combination of both high temperature and high humidity. This is because corrosion of lead precedes that of copper, which is one of the materials comprising the brush, and this prevents the copper from corroding. Moreover, lead functions as a solid lubricant and reduces brush wear. We developed the leadfree brush material, by adding soft metallic substances that corrode prior to copper and are also oxidation-resistant, as well as possessing low hardness and solid lubricant properties. The developed lead-free brush surpasses the conventional lead-added brush in durability and permanence. key words: carbon brush, lead free, starter, wear, corrosion