Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/12—Ignition, e.g. for IC engines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
  • F02P3/00—Other installations
  • F02P3/01—Electric spark ignition installations without subsequent energy storage, i.e. energy supplied by an electrical oscillator
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
  • H01F27/324—Insulation between coil and core, between different winding sections, around the coil; Other insulation structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/10—Composite arrangements of magnetic circuits
  • H01F3/14—Constrictions; Gaps, e.g. air-gaps
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
  • H01T13/00—Sparking plugs
  • H01T13/40—Sparking plugs structurally combined with other devices
  • H01T13/44—Sparking plugs structurally combined with other devices with transformers, e.g. for high-frequency ignition
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/12—Ignition, e.g. for IC engines
  • H01F2038/122—Ignition, e.g. for IC engines with rod-shaped core
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/24—Magnetic cores
  • H01F27/26—Fastening parts of the core together; Fastening or mounting the core on casing or support
  • H01F27/263—Fastening parts of the core together
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
  • H01F27/346—Preventing or reducing leakage fields

Definitions

• This invention relates to transformers, a core for a transformer and an ignition system for a vehicle comprising a transformer.
• a known vehicle ignition system transformer comprises a unitary solid or laminated core, such as a pencil core, of a magnetic material. Primary and secondary windings of the transformer are wound around the core.
• the transformer must comply with a number of requirements.
• the solid core must provide good magnetic coupling between the primary and secondary windings, so that energy can be transferred from the primary winding to the secondary winding during a single pulse.
• the primary and secondary inductances must be large enough so that sufficient energy can be stored in the magnetic core, so that the maximum primary current is not too high and so that the spark duration is long enough for a stable spark.
• the large secondary inductance requires a large number of turns. This results in the secondary winding having a resistance of several kilo-ohm.
• the transformer must provide for sufficient heat transfer from the windings to the outside of the transformer.
• the magnetic design must be such as to prevent core saturation during high voltage generation.
• enough magnetic material is required to store sufficient energy in the magnetic field.
• Very good electrical isolation is required between the secondary windings and the magnetic core.
• the maximum secondary voltage is normally larger than 30 kV and the magnetic core is normally conductive.
• the isolation between the core and windings must be able to withstand the maximum voltage. Sufficient isolation between the windings is also required. Because most magnetic materials meeting these requirements are conductive or have a low dielectric strength, a relatively thick isolation layer is required between the core and the secondary winding, which is undesirable.
• a transformer suitable for use in an automobile engine must be able to operate at temperature between about
• a transformer comprising a core, a primary winding and a secondary winding, the core comprising an elongate limb having a main axis, a plurality (n) of segments of a magnetic material and gaps between segments arranged in alternating relationship along the main axis, each gap having a linear segment separating extent which is parallel to the main axis, n being larger than 3 and the gaps being filled with an isolation medium.
• Each segment may comprise a cylindrical body having a main axis and comprising a side wall extending between opposed first and second end walls.
• the gap between first and second adjacent segments may extend between the second end wall of the first segment and the first end wall of the second segment.
• the main axes of the segments may be aligned with the main axis of the limb.
• At least respective centre regions of the first and second end walls of a segment may extend parallel to one another. Edges between the end walls and the side wall may be rounded.
• the body may be circular in transverse cross section or generally rectangular. In the latter case corner regions of the side wall may also be rounded.
• n may be larger than any one of 4, 5, 6, 7, 8, 9 and 10.
• the segments may be solid or laminated and arranged linearly.
• the segments may have the same length and may be equi-spaced, so that the widths of the gaps are equal. In other embodiments, at least some of the segments may have different lengths and at least some of the gaps may have different widths.
• the primary and secondary windings may be wound concentrically around the core.
• the secondary winding may be located concentrically closer to the core than the primary winding.
• the primary and secondary windings may be wound concentrically around the core from one end of the core to the other. Both of these windings may be wound concentrically around a part of the linearly arranged segments.
• the windings may be wound linearly along the linear arrangement of segments, so that each winding comprises a plurality of linearly arranged and abutting turns.
• the primary and secondary windings may overlap with one another or may not overlap.
• the transformer may comprise an outer jacket of a magnetic material housing the core, the primary winding and the secondary winding.
• the outer jacket may comprise a single elongate hollow cylindrical body.
• the outer jacket may comprise a plurality of jacket segments.
• Each jacket segment may be hollow cylindrical in configuration and the jacket segments may be linearly arranged.
• the isolation medium may comprise at least one of a liquid and a solid.
• All voids may be filled with the isolation medium.
• the invention also includes within its scope a core comprising an elongate limb having a main axis, a plurality (n) of segments of a magnetic material and gaps between segments arranged in alternating relationship along the main axis, each gap having a linear segment separating extent which is parallel to the main axis, n being larger than 3 and the gaps being filled with an isolation medium.
• an ignition system for a vehicle comprising a transformer as herein defined and/or described and wherein one end of the secondary winding is connected to at least one spark plug and wherein the transformer is driven resonantly by an oscillating circuit connected to the primary winding.
• the oscillating frequency of the oscillating circuit may be between 10OkHz and 3MHz.
• figure 1 is a longitudinal section through a transformer according to the invention
• figure 2 is a block diagram of relevant parts of an ignition system comprising the transformer.
• a transformer according to the invention is generally designated by the reference numeral 10 in the figures.
• the transformer may find particular application in vehicle ignition systems.
• the transformer 10 comprises a core 12, a primary winding 14 and a secondary winding 16.
• the core comprises an elongate limb 13 having a main axis 15, a plurality (n) of segments (12.1 to 12.n) of a magnetic material and gaps (18.1 to 18.n-1) between segments arranged in alternating relationship along the main axis 15.
• the main axis 15 is parallel to a direction of a magnetic field in the limb.
• Each gap has a linear segment separating extent g which is parallel to the main axis.
• the value of n is larger than three (3) and the gaps are filled with an isolation medium 20.
• the isolation medium is required to have a large dielectric strength, preferably higher than 9kV/mm, more preferably higher than 20kV/mm over the temperature range of -40°c to +140 0 C There are many plastic materials available that meet this requirement.
• the isolation material must preferably also have a low relative permittivity ⁇ r , typically lower than 4 and preferably lower than 3.
• the magnetic material is required to have a high permeability, high saturation flux density and low loss over a -40 0 C to +140 0 C temperature range and DC to 1 MHz frequency range.
• An example of such a material is the soft ferrite TSC-50ALL having a relative permeability higher than 3000 for flux densities lower than 3000 Gauss, for frequencies up to 1 MHz and temperatures between -30°c and +200°c.
• This ferrite's core loss is less than 10 mW/cm 3 at a frequency of 500 kHz, a flux density of 100 Gauss and a temperature of 70 0 C
• the segments 12.1 to 12.n are arranged linearly and adjacent segments are separated by the gaps 18.1 to 18.n-1.
• the primary winding 14 and the secondary winding 16 are wound concentrically around the core. Each winding comprises a plurality of turns. More particularly secondary winding 16 comprises turns 16.1 to
• a concentric outer jacket 22 of a magnetic material provides a magnetic return path.
• the jacket may comprise a single hollow cylindrical body or may comprise two or more hollow cylindrical segments. The segments may be linearly arranged.
• the magnetic material of the core segments and the jacket may be the same or may be different materials.
• the core has a length
• the diameter of the core is d.
• the isolation annulus has a volume of 4.3cm 3 .
• the capacitance between the secondary winding and the core is 0.56pF/mm or 31 pF for the whole length J.
• the capacitance between the first 5mm of turns and the last 5mm of turns is given by the capacitance of the first
• the inductance was measured to be about 64nH per turn squared when using TSC-50ALL ferrite.
• the length of wire per turn is about 40mm, giving an inductance of 36pH/mm squared of wire.
• This requires a segment to winding distance h filled by the isolation material 20 of at least 0.44mm.
• the capacitance between segments is 4.5pF and between the winding 16 and a segment 2pF/mm.
• the capacitance between the first 5mm of turns from turn 16.1 and the last 5mm of turns to turn 16. m is 0.45pF.
• the inductance was measured to be about 27nH per turn squared.
• the length of wire per turn 16.1 to 16. m is 31mm, giving an inductance of 28pH/mm squared for a certain length of wire.
• the inductance is less for a given number of turns (64nH/mm compared to 27nH/mm), it is presently believed that more energy can be stored in the magnetic material due to the number of gaps.
• the segmented core 10 therefore would require a shorter length of winding wire, which would have a lower winding resistance than the corresponding winding of a solid core transformer.
• segmented core need 1.1cm 3 compared to 4.3cm 3 isolation material for the solid core. This is significant when compared to the core's volume of 3.5cm 3 .
• segmentation of the core 12 would reduce the total isolation requirement over the whole length i of the core 12.
• Turns 16.1 to 16. m may be wound closer to the core 12.
• the resulting smaller radius of the turns reduces the winding wire length and resistance.
• the shorter segments 12.1 to 12.n may give rise to lower thermal-mechanical stresses, and the distributed gaps between segments may provide higher saturation energy.
• the capacitance of the secondary winding between the first and last 5mm of turns is significantly reduced from 1.4pF to 0.45pF.
• the transformer may find particular application in an ignition system 30 (shown in figure 2) for a vehicle (not shown).
• the transformer may be driven resonantly, similarly to a Tesla coil, by an oscillating circuit 32 at an oscillating frequency f 0 of about 10OkHz - 3MHz, where energy is transferred from the primary winding 14 to the secondary winding 16 during each cycle of several cycles. It is expected that the requirement for good coupling between the primary winding 14 and secondary winding 16 would not be as strict as with a conventional transformer comprising a conventional unitary core.
• Turn 16.1 is normally connected to a spark plug 34 and turn 16.m may be grounded or connected to an energy (voltage or current) source.
• the magnetic core 12 may be designed to saturate when energy is transferred directly through the secondary winding 16 for fast energy transfer.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Composite Materials (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Coils Of Transformers For General Uses (AREA)
• Ignition Installations For Internal Combustion Engines (AREA)
• Coils Or Transformers For Communication (AREA)
• Transformers For Measuring Instruments (AREA)

Priority Applications (11)

Applications Claiming Priority (2)

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Citations (9)

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• 2010
  • 2010-06-15 MY MYPI2011006026A patent/MY155185A/en unknown
  • 2010-06-15 US US13/377,728 patent/US8354911B2/en not_active Expired - Fee Related
  • 2010-06-15 CN CN201080026820.8A patent/CN102460607B/zh not_active Expired - Fee Related
  • 2010-06-15 RU RU2012101256/07A patent/RU2526371C2/ru not_active IP Right Cessation
  • 2010-06-15 KR KR1020117028674A patent/KR101439166B1/ko not_active Expired - Fee Related
  • 2010-06-15 BR BRPI1010687A patent/BRPI1010687A2/pt not_active Application Discontinuation
  • 2010-06-15 JP JP2012514588A patent/JP2012530356A/ja active Pending
  • 2010-06-15 WO PCT/IB2010/052679 patent/WO2010146538A1/en not_active Ceased
  • 2010-06-15 ES ES10730853T patent/ES2411093T3/es active Active
  • 2010-06-15 EP EP10730853A patent/EP2443637B1/en not_active Not-in-force
  • 2010-06-15 AU AU2010261352A patent/AU2010261352B2/en not_active Ceased
• 2011
  • 2011-11-14 ZA ZA2011/08339A patent/ZA201108339B/en unknown
• 2015
  • 2015-07-10 JP JP2015139016A patent/JP6215266B2/ja not_active Expired - Fee Related

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