An ignition plug 10 comprises an elongate cylindrical body 12 of an electrically insulating material having a first end 12.1, a second end 12.2 opposite to the first end and a first face 14 at the first end. A first elongate electrode 16 having a first end 16.1 and a second end 16.2 extends longitudinally in the body. The first electrode terminates at the first end thereof a first distance d1 from the first end of the body in a direction towards the second end of the body. The body hence defines a blind bore 18 extending between the first end of the first electrode and the first end of the body. A second electrode is provided on an outer surface of the body and terminates at one of a) flush with the first face 14 of the body and b) a second distance d2 from the first end of the body in a direction towards the second end of the bod.

An ignition plug 10 comprises an elongate cylindrical body 12 of an electrically insulating material having a first end 12.1, a second end 12.2 opposite to the first end and a first face 14 at the first end. A first elongate electrode 16 having a first end 16.1 and a second end 16.2 extends longitudinally in the body. The first electrode terminates at the first end thereof a first distance d1 from the first end of the body in a direction towards the second end of the body. The body hence defines a blind bore 18 extending between the first end of the first electrode and the first end of the body. A second electrode is provided on an outer surface of the body and terminates at one of a) flush with the first face 14 of the body and b) a second distance d2 from the first end of the body in a direction towards the second end of the bod.

In an ignition apparatus, an ignition plug is provided. In the ignition plug, a tubular outer conductor surrounds an inner conductor, and a dielectric member is disposed in the tubular outer conductor to define a plasma formation region between the inner conductor and the dielectric member. The plasma formation region has opposing first and second ends in the axial direction of the tubular outer conductor, and the first end of the plasma formation region communicates with the combustion chamber. A power source is connected between the inner and tubular outer conductors. A controller causes a power source to apply electromagnetic power pulses with intervals therebetween across the inner and tubular outer conductors during an ignition cycle of an engine. Each of the electromagnetic power pulses forms at least a corresponding plasma in the plasma formation region.

In an ignition apparatus, an ignition plug is provided. In the ignition plug, a tubular outer conductor surrounds an inner conductor, and a dielectric member is disposed in the tubular outer conductor to define a plasma formation region between the inner conductor and the dielectric member. The plasma formation region has opposing first and second ends in the axial direction of the tubular outer conductor, and the first end of the plasma formation region communicates with the combustion chamber. A power source is connected between the inner and tubular outer conductors. A controller causes a power source to apply electromagnetic power pulses with intervals therebetween across the inner and tubular outer conductors during an ignition cycle of an engine. Each of the electromagnetic power pulses forms at least a corresponding plasma in the plasma formation region.

A corona comprises a central electrode surrounded by an insulator, which is surrounded by a conductive component. The conductive component includes a shell and an intermediate part both formed of an electrically conductive material. The intermediate part is a layer of metal which brazes the insulator to the shell. An outer surface of the insulator presents a lower ledge, and the layer of metal can be applied to the insulator above the lower ledge prior to or after inserting the insulator into the shell. The conductive inner diameter is less than an insulator outer diameter directly below the lower ledge such the insulator thickness increases toward the electrode firing end. The insulator outer diameter is also typically less than the shell inner diameter so that the corona igniter can be forward-assembled.

A corona comprises a central electrode surrounded by an insulator, which is surrounded by a conductive component. The conductive component includes a shell and an intermediate part both formed of an electrically conductive material. The intermediate part is a layer of metal which brazes the insulator to the shell. An outer surface of the insulator presents a lower ledge, and the layer of metal can be applied to the insulator above the lower ledge prior to or after inserting the insulator into the shell. The conductive inner diameter is less than an insulator outer diameter directly below the lower ledge such the insulator thickness increases toward the electrode firing end. The insulator outer diameter is also typically less than the shell inner diameter so that the corona igniter can be forward-assembled.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.