초록 ▼

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

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.

대표청구항 ▼

1. A corona igniter (20) for providing a radio frequency electric field to ionize a portion of a fuel-air mixture and provide a corona discharge (24) in a combustion chamber (22), comprising: a housing (34) including a plurality of walls (40, 42, 44) presenting a total housing volume therebetween,a

1. A corona igniter (20) for providing a radio frequency electric field to ionize a portion of a fuel-air mixture and provide a corona discharge (24) in a combustion chamber (22), comprising: a housing (34) including a plurality of walls (40, 42, 44) presenting a total housing volume therebetween,a coil (26) disposed in said housing (34) for receiving energy at a first voltage and transmitting the energy at a second voltage higher than the first voltage,an electrode electrically coupled to said coil (26) for receiving the energy and providing the radio frequency electric field,a coil filler (36) formed of a resin material disposed on said coil (26),said coil filler (36) having a filler volume being a portion of said total housing volume,a capacitance reducing component (38) having a relative permittivity of less than 6 disposed in said housing (34),said capacitance reducing component (38) having a component volume being a portion of said total housing volume and being greater than said filler volume. 2. The corona igniter (20) of claim 1 wherein said capacitance reducing component (38) is at least 20% of said total housing volume and said filler volume is at least 10% of said total housing volume. 3. The corona igniter (20) of claim 1 wherein said filler volume is 10 to 70% of said total housing volume. 4. The corona igniter (20) of claim 1 wherein said component volume is 20 to 90% of said total housing volume. 5. The corona igniter (20) of claim 1 wherein said component volume is at least two times greater than said filler volume. 6. The corona igniter (20) of claim 1 wherein said capacitance reducing component (38) extends continuously around said coil (26). 7. The corona igniter (20) of claim 1 wherein said coil (26) includes a plurality of windings (54) and a winding gap around said windings (54) and wherein said coil filler (36) is disposed in said winding gaps. 8. The corona igniter (20) of claim 7 wherein said windings (54) extend circumferentially around a coil center axis (ac) and said capacitance reducing component (38) extends continuously around said windings (54) along said housing (34). 9. The corona igniter (20) of claim 1 wherein said coil (26) has a length (I) extending from a coil low voltage end (28) receiving the energy to a coil high voltage end (30) transmitting the energy and said capacitance reducing component (38) extends along at least 50% of said length (l). 10. The corona igniter (20) of claim 9 wherein said coil filler (36) is disposed at said coil high voltage end (30). 11. The corona igniter (20) of claim 9 including a retainer (84) formed of an electrically insulating material separate from said coil filler (36) coupling said coil low voltage end (30) to said housing (34). 12. The corona igniter (20) of claim 1 wherein said capacitance reducing component (38) has a dielectric strength of at least 3 kV/mm. 13. The corona igniter (20) of claim 1 wherein said capacitance reducing component (38) includes at least one of a gas, an oil having a dielectric strength of at least 3 kV/mm, a liquid having a dielectric strength of at least 10 kV/mm, and a solid having a permittivity less than 6. 14. The corona igniter (20) of claim 13 wherein said gas includes at least one of ambient air and a gas having a pressure of not greater than 10 bar. 15. The corona igniter (20) of claim 1 wherein said coil filler (36) has a dielectric strength of at least 10 kV/mm and a relative permittivity of less than 8. 16. A corona igniter (20) for providing a radio frequency electric field to ionize a portion of a fuel-air mixture and provide a corona discharge (24) in a combustion chamber (22), comprising: a housing (34) having interior walls (40, 42, 44) presenting a total housing volume therebetween,a coil (26) disposed in said housing (34) for receiving energy at a first voltage and transmitting the energy at a second voltage being at least 15 times higher than the first voltage,said coil (26) extending longitudinally along a coil center axis (ac) and having a length (l) extending from a coil low voltage end (28) receiving the energy at the first voltage to a coil high voltage end (30) transmitting the energy at the second voltage,said coil (26) having an inductance of at least 500 micro henries,said coil (26) including a plurality of windings (54) horizontally aligned with one another and extending longitudinally along said coil center axis (ac) and a winding gap disposed around each of said windings (54),said windings (54) presenting a perimeter around said coil center axis (ac) and having a winding diameter (d) extending across said coil center axis (ac),a coil former (62) formed of electrically insulating resin material disposed along said coil center axis (ac) and spacing said windings (54) from said coil center axis (ac),a coil filler (36) formed of electrically insulating resin material different from said coil former (62) disposed in said housing (34) at said coil high voltage end (30) and disposed in said winding gap around windings (54),said coil filler (36) having a dielectric strength of at least 3 kV/mm, a thermal conductivity of at least 0.125 W/m.K, and a relative permittivity of at less than 6,said coil filler (36) having a filler volume of 10 to 70% of said total housing volume,an electrode electrically coupled to said coil (26) for receiving the energy from said coil (26),a gap region disposed between said coil (26) and said interior walls (40, 42, 44) of said housing (34),a capacitance reducing component (38) having a relative permittivity of less than 6 and a component volume filing said gap region of said housing (34),said capacitance reducing component (38) extending continuously around said coil (26) and along said interior walls (40, 42, 44) of said housing (34),said capacitance reducing component (38) disposed along at least 50% of said length (l) of said coil (26),said component volume being greater than said filler volume,said component volume being 20 to 90% of said total housing volume,said capacitance reducing component (38) having a dielectric strength of at least 3 kV/mm, andsaid capacitance reducing component (38) including at least one of a gas, an oil having a dielectric strength of at least 3 kV/mm, a liquid having a dielectric strength of at least 10 kV/mm, and a solid having a permittivity of less than 6. 17. A method of forming a corona igniter (20) for providing a radio frequency electric field to ionize a portion of a fuel-air mixture and provide a corona discharge (24) in a combustion chamber (22), comprising the steps of: providing a coil filler (36) attached to a coil (26), wherein the coil filler (36) includes a resin and has a filler volume and the coil (26) has an inductance of at least 500 micro henries,disposing the coil (26) and the attached coil filler (36) in a housing (34), andfilling the housing (34) with a capacitance reducing component (38) having a permittivity of less than 6 and having a component volume being greater than the filler volume. 18. The method of claim 17 wherein the step of filling the housing (34) with the capacitance reducing component (38) includes filling at least 20% of a total housing volume. 19. The method of claim 17 wherein the step of providing the coil filler (36) attached to the coil (26) includes disposing the resin on the coil (26) and curing the resin.