It was on September 15, 1909 that Charles Franklin Kettering filed a patent on his new ignition system, ushering in an automotive revolution and igniting a career that ultimately ended with 140 patents, including other notable inventions such as the electric starter motor, leaded gasoline and the air conditioning refrigerant known as Freon.
The ignition system that Kettering patented was the first current-interrupted system driven from battery voltage. Introduced in the 1910 Cadillac, development of the system was handled by Kettering's company, Dayton Engineering Laboratories Co., which later became a subsidiary of General Motors Corporation known as Delco Electronics Corporation. Delco later became part of Hughes Electronics Corporation, with the commercial portion of that business now known as Delphi Corporation.
The system revolutionized the automotive industry by supplanting the use of magneto based ignition systems. With it, many of the reliability concerns with automobiles of the day, most notably troublesome starting of the engine, also subsided. Components of this new system included a single coil, a set of points, a capacitor and a distributor:
- The coil primarily served as a step-up transformer to convert the 6- or 12-volt battery voltage into a voltage high enough to generate a spark across the spark plug gap.
- The points, when closed, allow the coil to become magnetically charged. When the points are mechanically opened, the magnetic field in the coil collapses, generating a high-voltage pulse of 20,000 volts or greater.
- This pulse is then carried to the appropriate spark plug through the distributor, creating an arc (“spark”) across the gap of the plug.
- The capacitor, also commonly referred to as a condenser, is used to absorb or “condense” the back electromagentic field which is created when the magnetic field in the coil collapses. This minimizes burning of the point contacts and maximizes the life of the points.
The reduced cost and increased reliability of Kettering's ignition system became widely popular and served as the basis of the mechanically timed ignition system that was used on the majority of automobiles through the late 1970s.
Happy Motoring!
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