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article imageA Bright Idea Turns 100 - The Spark Plug

By Heiko Haupt     Jan 17, 2002 in Technology
STUTTGART (dpa) - It was a truly electrifying idea which German engineer Robert Bosch decided to patent on January 7, 1902.

The combination of an electrode and a ceramic insulator combined with a high-tension ignition system was revolutionary at a time when car electrical systems were primitive devices unable to cope with more powerful engines.

Bosch is regarded as the father of the sparking plug, or spark plug as the British call his invention, but there had been experiments along the same lines in early 19th century France. Most of these produced a spark mechanically though and this method proved unreliable at higher engine revolutions.

The job of the spark plug is more or less the same as it was 100 years ago. The ignition system produces electrical tension which triggers a spark across the gap between the electrodes of the sparking plug fitted to the engine's combustion chambers.

The petrol and air mixture in the chamber is ignited as the pistons reach the top of their stroke and the force of the explosion sends them back down again - the movement is turned into forward motion and that is what makes a vehicle move.

Until the 1980s research into sparking plugs was low-key but since then technology has been forced to keep pace with more sophisticated engine design. Scientists began to think about the way a spark behaves and that certain spark types led to less wear and fewer soot deposits which could inhibit performance, as Hans-Peter Vater, spokesman for Germany's Beru works in Ludwigsburg explained.

Companies have also been experimenting with different materials for the electrode tips of a sparking plug - the heart of the device. Nickel was first used followed by silver and even platinum.

This has led to sparking plugs capable of performing flawlessly and without misfirings for 60,000 kilometres and more, while 100,000 kilometres can be achieved with high quality versions. "In the old days a plug would last for between 15,000 and 20,000 kilometres and you had to clean the plugs more often," said Vater.

Early spark plugs were designed to be dismantled, adjusted and cleaned. These days the all-important gap is often set at the factory and does not need to be changed.

Sparking plug innovation has been even more important since the introduction of the fuel-cleaning catalytic converter. If a plug fails, hot, unburned mixture could find its way into the exhaust system and destroy the complicated catalyst. Replacement is expensive.

Recently designers of high-performance engines have paid closer attention to the sparking plug.

"There is now an amazing selection. Often a particular type of engine has its own, tailor-made sparking plug," said Helmut Schmaler of the German ADAC motoring organization. Drivers who just screw in "any old sparking plug" will soon notice the difference. "The wrong plug can actually shorten the life of an engine," said Schmaler.

Future spark plugs are likely to be even more sophisticated. Experts believe that as an increasing number of engines are fitted with electronic fuel injection, "smarter" plugs will be needed and that the introduction of sulphur-free fuels will probably extend the life of the plugs still further.
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