Abstract: A spark plug (20) includes an insulator seat angle (?i) of 35° to 50° and an increased insulator thickness (ti) in selected areas around the insulator seat (28). The insulator seat angle (?i) is greater than or equal to a boundary value provided by the equation: 90°?a cos [1?(R1?R2)÷(R4+R5)], and preferably not greater than 150% of the boundary value. The radii (R1, R2, R3, R4, R5) can be adjusted to maximize R4 while maintaining an acceptable R2. A gasket is compressed between the insulator (22) and shell (58), and the inner gasket thickness (tg2) is greater than or equal to 70% of the outer gasket thickness (tg1).

Abstract: A corona igniter (20) includes an ignition coil (26) providing a high voltage energy to an electrode. The coil (26) is disposed in a housing (34) and electrically isolated by a coil filler (36) and a capacitance reducing component (38) which together improve energy efficiency of the system. The coil filler (36) includes an insulating resin permeating the coil (26). The capacitance reducing component (38) has a permittivity not greater than 6, for example ambient air, pressurized gas, insulating oil, or a low permittivity solid. The capacitance reducing compound (38) surrounds the coil (26) and other components and fills the remaining housing volume. The coil filler (36) has a filler volume and the capacitance reducing component (38) has a component volume greater than the filler volume.

Abstract: 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. The intermediate part (36) is typically attached to a lower ledge (52) of the insulator outer surface (50) prior to inserting the insulator (26) into the shell (34). The shell firing end (56) is typically aligned with the lower edge and the intermediate firing end. The conductive inner diameter (Dg) is less than an insulator outer diameter (Dio) directly below the lower ledge (52) such the insulator thickness (ti) increases toward the electrode firing end (40).

Abstract: A spark plug (20) includes an insulator seat angle (?i) of 35° to 50° and an increased insulator thickness (ti) in selected areas around the insulator seat (28). The insulator seat angle (?i) is greater than or equal to a boundary value provided by the equation: 90°?a cos [1?(R1?R2)÷(R4+R5)], and preferably not greater than 150% of the boundary value. The radii (R1, R2, R3, R4, R5) can be adjusted to maximize R4 while maintaining an acceptable R2. A gasket is compressed between the insulator (22) and shell (58), and the inner gasket thickness (tg2) is greater than or equal to 70% of the outer gasket thickness (tg1).

Abstract: A corona igniter 20 with improved temperature control at the firing end is provided. The corona igniter 20 comprises a central electrode 24 include a core material 30, such as copper, surrounded by a clad material 32, such as nickel. The core material 30 extends longitudinally between an electrode terminal end 34 and an electrode firing end 36. The core material 30 is disposed at the electrode terminal end 34 and has a core length Ic equal to at least 90% of an electrode length Ie of the central electrode 24. At least 97% of the core length Ic is surrounded by an insulator 26. The electrode diameter is increased, such that a clad thickness tcl of the central electrode 24 is equal to at least 5% of an insulator thickness ti, and a core diameter Dc is equal to at least 30% of the insulator thickness ti.

Abstract: A corona igniter 20 includes an insulator 28 surrounding a central electrode 24 and a shell 30 surrounding the insulator 28. The shell 30 presents a shell gap 38 having a shell gap width ws between a shell lower end 34 and a shell inner surface 90 or shell outer surface 92. The shell 30 has a shell thickness is decreasing toward the shell lower end 34 allowing the shell gap width ws to increase toward the shell lower end 34. The shell gap 38 is open at the shell lower end 34 allowing air to flow therein, and the shell gap width ws is greatest at the shell lower end 34. The increasing shell gap width ws enhances corona discharge 22 along the insulator 28 between the central electrode 24 and shell 30.

Abstract: A system and method for detecting arc formation in a corona discharge ignition system is provided. The system includes a driver circuit conveying energy oscillating at a resonant frequency; a corona igniter for receiving the energy and providing a corona discharge; and a frequency monitor for identifying a variation in an oscillation period of the resonant frequency, wherein the variation in the oscillation period indicates the onset of arc formation. The method includes supplying the energy to the driver circuit and to the corona igniter; obtaining the resonant frequency of the energy in the oscillating driver circuit; and identifying a variation in the oscillation period of the resonant frequency.

Abstract: A system and method for controlling an arc formation in corona discharge ignition system is provided. The system includes a corona igniter for receiving energy at a voltage and providing a corona discharge. An energy supply providing the energy to the corona igniter at a voltage. The system also includes a corona controller for initiating a decrease in the voltage of the energy provided to the corona igniter in response to the onset of arc formation. The voltage is decreased until the arcing is depleted, and then the voltage is increased again to resume the corona discharge.

Abstract: A corona igniter 20 includes a coil 24 with a plurality of copper windings 26 extending longitudinally along a coil center axis ac. A magnetic core 30 is disposed along the coil center axis ac between the windings 26 and includes a plurality of discrete sections 32. The discrete sections 32 are spaced axially from one another by a core gap 34 filled with a non-magnetic gap filler 78. The magnetic core 30 has a core length Im and the coil 24 has a coil length Ic less than the core length Im. A coil former 62 having a former thickness tf spaces the coil 24 from the magnetic core 30. A length difference Id between the core length Im and the coil length Ic is preferably equal to or greater than the former thickness tf.

Abstract: A corona igniter 20 includes an electrode gap 28 between the central electrode 22 and the insulator 32 and a shell gap 30 between the insulator 32 and the shell 36. The gaps 28, 30 are filled with a filler material 40 to prevent corona discharge 24 in the gaps 28, 30 and to concentrate the energy at a firing tip 58 of the central electrode 22. The filler material 40 may be electrically insulating or conductive. The shell gap width ws may be greatest at a shell lower end 92. The shell gap 30 may also be in a turnover region between a shell upper end 44 and the insulator 32, in which case the filler material 40 is injection molded around the turnover region. During operation of the igniter 20, the filler material 40 provides a reduced voltage drop across the gap 28, 30.

Abstract: A corona ignition system for providing a corona discharge (24) includes an igniter (20) having an electrode (26) with an asymmetrical firing tip (28) relative to an electrode center axis (ae). The firing tip (28) includes a first surface area (A1) facing the fuel injector (42) which is greater than a second surface area (A2) facing a cylinder block (32). The first surface area (A1) presents a projection (60) having a sharp edge, and the second surface area (A2) presents a round outward surface (62). Accordingly, a radio frequency electric field emitted from the first surface area (A1) provides a robust corona discharge (24) in a flammable area at an outside edge (30) of the fuel spray. No electric field is emitted from the second surface area (A2), and no power arcing occurs between the second surface area (A2) and the cylinder block (32).

Abstract: A corona igniter 20 includes an electrode gap 28 between the central electrode 22 and the insulator 32 and a shell gap 30 between the insulator 32 and the shell 36. An electrically conductive coating 40 is disposed on the insulator 32 along the gaps 28, 30 to prevent corona discharge 24 in the gaps 28, 30 and to concentrate the energy at a firing tip 58 of the central electrode 22. The electrically conductive coating 40 is disposed on an insulator inner surface 64 and is spaced radially from the electrode 22. The electrically conductive coating 40 is also disposed on the insulator outer surface 72 and is spaced radially from the shell 36. During operation of the igniter 20, the electrically conductive coating 40 provides a reduced voltage drop across the gaps 28, 30 and a reduced electric field spike at the gaps 28, 30.

Abstract: A corona igniter (20) for emitting a radio frequency electric field and providing a corona discharge (24) includes a central electrode (22) at a positive voltage, a grounded metal shell (30), and an insulator (28) with an abruption (34) extending radially outward relative to the central electrode (22). The abruption (34) is typically an increase of at least 15% of a local thickness (t) of the insulator (28) over less than 25% of a nose length (1) of an insulator nose region (74). The abruption (34) is typically one flank (82) of a protrusion or a notch, and the flank (82) faces the shell (30). The abruption (34) reverses the electric field and voltage potential gradient along the insulator outer surface (32), repels charged ions away from the insulator (28), and thus prevents the formation of a conductive path between the central electrode (22) and the shell (22).

Abstract: A corona discharge (24) ignition includes an electrode (38) emitting a radio frequency electric field and providing a corona discharge (24) to ignite a combustible mixture. The system includes a controlled high voltage energy supply (52) providing energy to a main energy storage (28) at a main voltage. A fixed high voltage energy supply (54) provides extra energy to an extra energy storage (26) at an extra voltage, which is greater than the main voltage. While the corona discharge (24) is being provided, the energy of the main energy storage (28), but not the extra energy storage (26), is provided to the electrode (38). When the corona discharge (24) switches to arc discharge, the extra energy of the extra energy storage (26) is provided to the corona igniter (22) to enhance the arc discharge and provide reliable ignition until the corona discharge (24) is restored.

Abstract: A corona igniter (20) includes an ignition coil (26) providing a high voltage energy to an electrode. The coil (26) is disposed in a housing (34) and electrically isolated by a coil filler (36) and a capacitance reducing component (38) which together improve energy efficiency of the system. The coil filler (36) includes an insulating resin permeating the coil (26). The capacitance reducing component (38) has a permittivity not greater than 6, for example ambient air, pressurized gas, insulating oil, or a low permittivity solid. The capacitance reducing compound (38) surrounds the coil (26) and other components and fills the remaining housing volume. The coil filler (36) has a filler volume and the capacitance reducing component (38) has a component volume greater than the filler volume.

Abstract: A corona discharge ignition system 20 includes an igniter 22 for receiving pulses of electrical energy each having a radio frequency. The igniter 22 emits pulses of electrical field ionizing a fuel-air mixture and providing pulses of corona discharge 24, rather than a continuous, un-pulsed corona discharge over the same period of time. The system 20 includes at least one power supply 48, 50 providing the electrical energy to a corona drive circuit 52 and ultimately to the igniter 22. The system 20 can include a variable high voltage power supply 50 and a local charge storage device 70 for providing pulses of the electrical energy to the corona drive circuit 52. The system 20 provides a robust ignition comparable to a single event corona discharge ignition system, with improved resistance to arc formation, while using a fraction of the energy.

Abstract: A corona ignition system 20 includes a corona drive circuit 26 and an auxiliary energy circuit 28. The energy circuit 28 stores energy during a standard corona ignition cycle. When arc discharge occurs or corona discharge switches to an arc discharge, the energy circuit 28 discharges the stored energy to the electrode 30 to intentionally maintain a robust arc discharge 29 and thus provide reliable ignition. The stored energy is transmitted to the electrode 30 over a predetermined period of time. The arc discharge is detected and an arc control signal 60 is transmitted to the energy circuit 28, triggering discharge of the stored energy to the electrode 30. The stored energy can be transmitted to the electrode 30 along a variety of different paths. The voltage of the stored energy is typically increased by an energy transformer 70 before being transmitted to the electrode 30.

Abstract: A glow plug has an annular metal shell and a heater assembly including a central electrode and a heater probe. The metal shell is configured to receive the heater assembly therein. The central electrode has an elongate body extending between a terminal end configured for electrical communication with a power source and an attachment end. The heater probe has an elongate body extending between a proximal end and a free distal end. Either the attachment end of the central electrode or the proximal end of the heater probe has a recessed pocket with a tapered inner surface converging axially extending axially therein. The other of the attachment end of the central electrode or the proximal end of the heater probe has a tapered outer surface configured for receipt in the recessed pocket.