Mercury free xenon HID lamps have matured over the last years. Beyond the basic mercury free concepts, several innovative solutions have been implemented to make today's mercury free lamps reliable and high-performing light sources. Mercury free xenon HID lamps began to replace mercury containing lamps in the automotive industry in 2004. This transition process started in Japan using the D4, continued in the US with the introduction of the D3 in 2006 and finally reached Europe in 20O7 when the first car model was equipped with mercury free HID lamps. Previous lamp generations (D1 and D2) contained approximately 0,5 mg Mercury. Environmental concerns in Japan kicked off a worldwide industry effort to eliminate mercury from xenon HID resulting in a major win for environmental sustainability. The mercury free alternatives have matured over the last years and the trend towards environmentally friendly discharge lamps has gained additional momentum. - Ignition reliability: Paschen's law describes electrical breakdown voltage of gases as a function of the pressure and distance between electrodes. Accordingly, the increased xenon pressure of xenon HID lamps leads to an increased breakdown voltage. - Pinch stability: The higher lamp current of mercury free lamps exposes the seal area and the electrodes to a higher thermal load. While the electrodes can be made thicker to withstand the current load, the thickness of the molybdenum sealing foil is limited. The thermal expansion of molybdenum and quartz is very different and only when the foil is very thin an airtight seal can be created and maintained. - Arc stability: A stable arc attachment at the electrode tip requires a stable electrode tip shape with edges or protrusions that define the attachment point Though this is generally true it poses a challenge for mercury free lamps with an inrush current increased from 2,6 A to 3,2 A and a steady state current increased from 0,4 A to 0,8A. - Mercury free xenon HID lamp; product performance: Today's mercury free lamps achieve the same performance level and reliability as previous mercury containing lamps. The lumen maintenance of the mercury free alternative outperforms mercury containing lamps up to 2000 h and has an equivalent overall performance. Future development efforts will target prolonging lamp lifetime and improving beam maintenance through thermal bulb and electrode optimization. Some key contributions are expected from progress in material research and electrode modelling. The unleashed transition from mercury containing lamps to environmentally friendly alternatives in the automotive industry is more than a valuable contribution to environmental sustainability. It shows that environmental consciousness is a driving force for technical innovation and progress.
Mercury free xenon HID lamps - from feasibility to reliability
Quecksilberfreie Xenon HID Lampen - von der Machbarkeit bis zur Realisierung
2007
8 Seiten, 6 Bilder, 9 Quellen
Conference paper
English
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