Search Results

Higher pressure and higher precision are required for diesel fuel injection equipment in response to increasingly severe emissions control regulations. Market diesel fuels have become more diversified than in the past. Diesel fuel quality has also been changing, being affected by crude oil slate, extreme lowering of sulfur content, and diesel reformulated from heavy fuel oil, among other reasons. As a result of this, deposits thought to have a fuel origin have been observed within diesel fuel injectors in certain regions. Related changes in fuel injection quantity have also been observed. This paper determines injector deposit production mechanisms. It focuses on the structural changes of deposit causative substances by temperature as well as injector design change improvements to prevent deposits.

To comply with increasingly stringent emission regulations, there is a high demand for A/F sensors with shorter light-off time and higher accuracy. Improvement of sensor accuracy requires reduction in sensor output shift induced by unburned hydrogen in the exhaust gas. The sensor output shift can effectively be reduced by placing a catalyst at the gas inlet of the sensing element. However, this involves the challenging technical task of developing a catalyst material with high durability in the sensor operating environment. By using a theoretical analysis technique, we studied a new catalyst material with superior catalytic performance and high durability, and have successfully improved A/F sensor accuracy, as reported in the following paper.

We have been developing the mixed-potential type NOx sensor which can detect the total-NOX concentration directly in exhausts for automobiles. It has been confirmed that the sensor is capable of detecting wide concentrations of total-NOx from 20 to 1000 ppm under the condition from rich-burn (A/F=12) to lean-burn without any interference from reducing gases, such as HC and CO. In addition, it has been confirmed that the sensor output is correlated fairly well to NOx concentrations from the analyzer in the engine test at any rotations. The results obtained here indicate that the present sensor has great possibility of being utilized as an on-board NOx sensor for practical use.