Abstract: A corona discharge ignition system comprising a plurality of corona igniters is provided. The system includes a control and drive electronics unit for directing the energy from a power supply toward the corona igniters; and a single transformer disposed between the control and drive electronics unit and the plurality of corona igniters. A plurality of igniter switching units is connected to the control and drive electronics unit and each igniter switching unit is connected to a separate one of the corona igniters. Each igniter switching unit allows current to travel from the transformer to the one connected corona igniter when activated and prevents current from traveling from the transformer to the one connected corona igniter and from the one connected corona igniter toward the transformer when deactivated. Only one of the igniter switching units is activated at any given time during operation of the system.

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. 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 (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). 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.

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) 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 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.

Abstract: A corona ignition system including a corona igniter, an energy supply, and a frequency detector is provided. The energy supply provides energy to the corona igniter during corona events which are spaced from one another by idle periods, during which no energy is provided to the corona igniter. During the idle periods, the frequency detector obtains the resonant frequency of the corona igniter from at least one of an output voltage and an output current of the energy stored in the corona igniter. The resonant frequency measured during this idle period is dependent only on the corona igniter, and not any other components of the system, and thus is very accurate. The drive frequency of future corona events can then be set based on this accurately measured resonant frequency to achieve a robust corona discharge.

Abstract: A corona ignition system for maintaining a drive frequency approximately equal to the resonant frequency of a corona igniter is provided. The system includes a current sensor, at least two cascaded timers which are electrically independent of a controller, and at least two switches. During operation, the current sensor measures the current at an input of the corona igniter. A conditioned current signal including information related to the zero crossings of the current ultimately activates a pair of the timers which in turn control and drive one of the switches. The conditioned current signal is not processed by the controller before driving the switch.

Abstract: A corona ignition system including a corona igniter, switches, and a programmable controller capable of rapidly adjusting to changes in resonant frequency is provided. Energy at a drive frequency and an output current is provided to the corona igniter. Switches provide energy to the corona igniter at the drive frequency and are activated at different times. The controller obtains the output current provided to the corona igniter, typically once every half cycle, and activates the first switch a predetermined amount of time after a first zero crossing of the output current, wherein the first zero crossing is a zero crossing of the most recent full cycle of the output current. The second switch is activated a predetermined amount of time after a second zero crossing occurring after the first zero crossing. The delay of the system is accounted for by the controller, rather than other components.

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 (el) 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 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 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 first main voltage. A fixed high voltage energy supply (54) provides extra energy to an extra energy storage (26) at a second extra voltage, which is greater than the first 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 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 ts 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 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 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 first main voltage. A fixed high voltage energy supply (54) provides extra energy to an extra energy storage (26) at a second extra voltage, which is greater than the first 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 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 lm and the coil 24 has a coil length lc less than the core length lm. A coil former 62 having a former thickness tf spaces the coil 24 from the magnetic core 30. A length difference ld between the core length lm and the coil length lc is preferably equal to or greater than the former thickness tf.

Abstract: The invention provides a system and method for controlling corona discharge. A driver circuit provides energy to the corona igniter and detects any arc formation. Optionally, in response to each arc formation, the energy provided to the corona igniter is shut off for a short time to dissipate the arc. Once the arc dissipates, the energy is applied again to restore the corona discharge. The driver circuit obtains information relating to the corona discharge, such as timing and number of arc formations. A control unit adjusts the energy provided to the corona igniter, shut-off time, or the duration of the corona event based on the information. The adjusted energy levels and duration are applied during subsequent corona events. For example, the voltage level could be reduced or the shutoff time could be increased to limit arc formations and increase the size of the corona discharge during the subsequent corona events.

Abstract: The invention provides a system and method for controlling corona discharge and arc formations during a single corona event, i.e. intra-event control. A driver circuit provides energy to the corona igniter and detects any arc formation. In response to each arc formation, the energy provided to the corona igniter is shut off for short time. The driver circuit also obtains information about the arc formations, such as timing of the first arc formation and number of occurrences. A control unit then adjusts the energy provided to the corona igniter after the shut off time and during the same corona event based on the information about the arc formations. For example, the voltage level could be reduced or the shut-off time could be increased to limit arc formations and increase the size of the corona discharge during the same corona event.

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. Controlling the arc formation provides improved energy efficiency during operation of the corona discharge ignition system.

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 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.