An ignition apparatus includes a spark plug and an ignition coil. The spark plug has a plug terminal protruding proximalward from an insulator. The ignition coil includes a coil main body, which includes a primary coil and a secondary coil, and a helical spring that electrically connects the secondary coil and the plug terminal. The plug terminal is made of a material that is both electrically conductive and magnetic. The plug terminal includes a terminal main body, which has an outer diameter greater than an inner diameter of the spring, and a terminal extension portion that has an outer diameter less than the inner diameter of the spring and extends proximalward from the terminal main body. A distal end portion of the spring abuts the terminal main body. The terminal extension portion is inserted and arranged in the spring. Between an outer circumferential surface of the terminal extension portion and an inner circumferential surface of the spring, there is interposed an insulating member.

An ignition system for an internal combustion engine has a power source, a transformer having a first primary winding and a second primary winding and a secondary winding, a connector extending from the secondary winding so as to connect with a terminal of a spark plug, and a multi-strike circuit cooperative with the electronic spark timing circuit so as to fire the transformer with multiple strikes between the falling edge and the rising edge. A booster circuit is cooperative at the electronic spark timing circuit so as to collect and store energy from the power source while the electronic spark timing circuit fires the transformer. A delay circuit fires the transformer at a time subsequent to the falling edge and before the rising edge.

An ignition system for an internal combustion engine has a power source, a transformer having a first primary winding and a second primary winding and a secondary winding, a connector extending from the secondary winding so as to connect with a terminal of a spark plug, and a multi-strike circuit cooperative with the electronic spark timing circuit so as to fire the transformer with multiple strikes between the falling edge and the rising edge. A booster circuit is cooperative at the electronic spark timing circuit so as to collect and store energy from the power source while the electronic spark timing circuit fires the transformer. A delay circuit fires the transformer at a time subsequent to the falling edge and before the rising edge.

An apparatus and a method for a circuit can include a voltage divider having a first and a second impedance in series, and having a voltage divider output. A switchable element is arranged in parallel with the first impedance and connected with the voltage divider output. The switchable element has an open state and a closed state. A spark gap device is configured to not generate a spark when the switchable element is in the open state and generate a spark when the switchable element is in the closed state.

A system and method for detecting resonant frequency of a corona igniter concurrent with operation of the corona igniter is provided. The method includes providing a plurality of pulses of energy to the corona igniter, each having a pulse duration and spaced from one another by a deadtime duration during which no energy is provided to the corona igniter. Each pulse duration is ceased before current flowing in the corona igniter crosses zero, and each zero crossing of the current occurs during one of the deadtime durations. The next pulse of energy is provided to the corona igniter in response to the zero crossing of the current. A resonant frequency value is then obtained based on a sum of the pulse and deadtime durations of two consecutive cycles, or the time between zero crossings. The resonant frequency values become more accurate over time, and the drive frequency is adjusted accordingly.

A system and method for detecting resonant frequency of a corona igniter concurrent with operation of the corona igniter is provided. The method includes providing a plurality of pulses of energy to the corona igniter, each having a pulse duration and spaced from one another by a deadtime duration during which no energy is provided to the corona igniter. Each pulse duration is ceased before current flowing in the corona igniter crosses zero, and each zero crossing of the current occurs during one of the deadtime durations. The next pulse of energy is provided to the corona igniter in response to the zero crossing of the current. A resonant frequency value is then obtained based on a sum of the pulse and deadtime durations of two consecutive cycles, or the time between zero crossings. The resonant frequency values become more accurate over time, and the drive frequency is adjusted accordingly.

An ignition device for igniting an air-fuel mixture in a combustion chamber, in particular an internal combustion engine, having a spark plug, which has a first electrode and a second electrode, and a high voltage source for generating an electrical high voltage pulse at an output of the high voltage source and having a high frequency voltage source for generating an electrical high frequency alternating voltage at an output of the high frequency voltage source, wherein the output of the high voltage source is electrically connected to the first electrode of the spark plug via a first electrical conductor path such that the high voltage pulse is applied to the first electrode, wherein the second electrode is electrically connected to an electrical ground potential, wherein the spark plug has a third electrode, wherein the output of the high frequency voltage source is electrically connected to the third electrode via a second electrical conductor path, such that the high frequency alternating voltage is applied to the third electrode.

A method is disclosed for producing a corona discharge for igniting an air/fuel mixture in an internal combustion engine. An igniter is provided having a discharge tip that protrudes into a combustion zone. During a first stage of a combustion process, a first primary winding of a RF transformer is driven at a first predetermined voltage level and at a first resonant frequency that is based on a first impedance in the combustion zone prior to onset of combustion, for generating a corona discharge at the tip of the igniter. During a second stage subsequent to the first stage, a second primary winding of the RF transformer is driven at a second predetermined voltage level and at a second resonant frequency that is based on a second impedance in the combustion zone at a time that is subsequent to onset of the combustion process.

A method is disclosed for producing a corona discharge for igniting an air/fuel mixture in an internal combustion engine. An igniter is provided having a discharge tip that protrudes into a combustion zone. During a first stage of a combustion process, a first primary winding of a RF transformer is driven at a first predetermined voltage level and at a first resonant frequency that is based on a first impedance in the combustion zone prior to onset of combustion, for generating a corona discharge at the tip of the igniter. During a second stage subsequent to the first stage, a second primary winding of the RF transformer is driven at a second predetermined voltage level and at a second resonant frequency that is based on a second impedance in the combustion zone at a time that is subsequent to onset of the combustion process.

An ignition system that uses a technique capable of restraining radiation of noise caused by discharge of a spark plug in the ignition system. The ignition system includes a spark plug and a power supply section. The spark plug is attached to an engine head. The power supply section has a battery having a ground terminal, and an ignition coil which transforms a voltage of the battery and supplies a transformed voltage to the spark plug. In the ignition system, a metallic shell of the spark plug is fixed to the engine head while being electrically insulated from the engine head through an insulator; an electrically conductive path is connected to the metallic shell; and the electrically conductive path is electrically connected to the ground terminal of the battery while being electrically insulated from the engine head.