Importance

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Abstract

A method of vaporising fuel in a spark-ignition engine using the supply of heat into the cylinder to wholly or partly vaporise the fuel, the heat being supplied by operation of a spark plug. One or more engine conditions can be sensed, such as engine temperature, coolant temperature, the cumulative amount of fuel supplied, engine speed or the time elapsed since start-up, and the spark plug operated to supply heat in response to such condition(s). The heat can be supplied by operating the spark plug more than once in an engine cycle or by operating the spark plug to form a spark over a time period determined in response to the engine condition. An AC circuit can be used to produce a substantially continuous spark over a defined time period or suitable angular duration. The heat can be supplied by operating the spark plug prior to engine cranking, to generate heat in the cylinder at engine start-up. A method of reducing spark plug fouling is also disclosed. This method operates the spark plug outside the period required for fuel ignition in order to supply additional heat to the spark plug terminals. Heat can be supplied by operating the spark plug more than once in an engine cycle. Heat can be supplied by operating the spark plug so as to form a spark over a time period representing at least 90° of crank angle. An AC circuit can be used to produce a substantially continuous spark over a defined time period or a suitable angular duration. The heat energy supplied by the spark during a single engine cycle can be in the order of 1000 mJ. These methods can be applied to air-assisted direct fuel injection systems.

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First Claim