A corona igniter (20) comprises a central electrode (22) surrounded by an insulator (26), which is surrounded by a conductive component. The conductive component includes a shell (34) and an intermediate part (36) both formed of an electrically conductive material. An outer surface (50) of the insulator (26) presents a lower ledge (52), and the intermediate part (36) is typically attached to the insulator (26) above the lower ledge (52) prior to inserting the insulator (26) into the shell (34). The conductive inner diameter (D.sub.g) is less than an insulator outer diameter (D.sub.io) directly below the lower ledge (52) such the insulator thickness (t.sub.i) increases toward the electrode firing end (40). The corona igniter (20) can be reversed-assembled by inserting an upper end (42) of the insulator into a firing end (56) of the shell.

An ignition unit produces an ignition in a combustion chamber of a combustion engine in the following manner. The ignition unit comprises a radiofrequency resonator that radiates a plasma-creating radiofrequency field into the combustion chamber. The ignition unit further comprises a microwave resonator that radiates a plasma-boosting microwave field into the combustion chamber. In an embodiment, the microwave resonator has an output surface to which the combustion chamber is exposed when the ignition unit is fitted on the combustion engine. The radiofrequency resonator may comprise an electrode that is at least partially embedded in the microwave resonator. The electrode may have a tip that is located at a distance from the output surface so that the microwave resonator provides a barrier between the tip and the output surface.

Disclosed is an inventive method for controlling a corona ignition device of an internal combustion engine. A corona discharge, which ignites fuel in a combustion chamber of the engine, is generated by applying a voltage to the corona ignition device. An actual value that is characteristic of the nitrogen oxide concentration of the exhaust gas is compared with a setpoint value, and, if the actual value deviates from the setpoint value by more than a specified threshold value and the actual value is greater than the setpoint value, the voltage is reduced after the comparison.

Disclosed is an inventive method for controlling a corona ignition device of an internal combustion engine. A corona discharge, which ignites fuel in a combustion chamber of the engine, is generated by applying a voltage to the corona ignition device. An actual value that is characteristic of the nitrogen oxide concentration of the exhaust gas is compared with a setpoint value, and, if the actual value deviates from the setpoint value by more than a specified threshold value and the actual value is greater than the setpoint value, the voltage is reduced after the comparison.

An ignition coil for internal combustion engines is provided which includes magnetically coupled primary and secondary coils, a case, a high-voltage tower, a resistor, and resin packed in the case. The case has the primary coil and the secondary coil disposed therein. The high-voltage tower is attached to a tower mount formed on a front end of the case. The resistor is embedded in the high-voltage tower with a front and a base end surfaces thereof exposed from the high-voltage tower. The resin is packed in the case to seal the primary coil and the secondary coil. This structure enhances the productivity of an assembly of the high-voltage tower and the resistor.

An ignition coil for internal combustion engines is provided which includes magnetically coupled primary and secondary coils, a case, a high-voltage tower, a resistor, and resin packed in the case. The case has the primary coil and the secondary coil disposed therein. The high-voltage tower is attached to a tower mount formed on a front end of the case. The resistor is embedded in the high-voltage tower with a front and a base end surfaces thereof exposed from the high-voltage tower. The resin is packed in the case to seal the primary coil and the secondary coil. This structure enhances the productivity of an assembly of the high-voltage tower and the resistor.

An ignition coil includes a low voltage terminal for connection with a battery and a high voltage terminal for connection with a spark plug. An assembly of windings interconnects the terminals. The ignition coil further includes a case containing the windings and the terminals. The case is configured for use with a cylinder head cover having a cylindrical bore with a key projecting radially inward of the bore. A cylindrical portion of the case has a central axis, a rotational locator surface, and an insertion guide groove configured to receive the key in the bore. A helical section of the groove is configured to receive the key when the case is in a first rotational orientation. The helical section is further configured for the rotational locator surface to move into abutment with the key upon rotation of the case from the first rotational orientation to a second rotational orientation.

An ignition coil includes a low voltage terminal for connection with a battery and a high voltage terminal for connection with a spark plug. An assembly of windings interconnects the terminals. The ignition coil further includes a case containing the windings and the terminals. The case is configured for use with a cylinder head cover having a cylindrical bore with a key projecting radially inward of the bore. A cylindrical portion of the case has a central axis, a rotational locator surface, and an insertion guide groove configured to receive the key in the bore. A helical section of the groove is configured to receive the key when the case is in a first rotational orientation. The helical section is further configured for the rotational locator surface to move into abutment with the key upon rotation of the case from the first rotational orientation to a second rotational orientation.

In an internal combustion engine that causes a predetermined gas flow in a combustion chamber, discharge plasma generated by a discharge device is caused to effectively absorb energy of an electromagnetic wave emitted from an electromagnetic wave emission device. At a time when a discharge operation and an emission operation are simultaneously performed so as to ignite a fuel air mixture, an emitting position of the electromagnetic wave on an antenna during the emission operation is located downstream of the discharge gap in a direction of the gas flow at the discharge gap so as to face toward the discharge plasma that has been drifted due to the gas flow.

An ignition system for an internal combustion engine has a power source, a transformer having first and second primary windings and a secondary winding, a connector extending from the secondary winding and adapted so as to connect with a terminal of the spark plug of the internal combustion engine, and electronic spark timing circuit cooperative with the transformer so as to activate and deactivate voltage to the first and second primary windings. The first and second primary windings are connected to the power source such that the transformer produces an alternating voltage output from the secondary winding of between 1 kHz and 100 kHz and a voltage of at least 20 kV. A forced push-pull inverter is cooperative with the electronic spark timing circuit so as to fix a frequency of voltage to the first and second primary windings.