CA2253571A1 - Magnetic core-coil assembly for spark ignition systems - Google Patents

Abstract

A magnetic core-coil assembly generates an ignition event in a spark ignition internal combustion system having at least one combustion chamber. The assembly comprises a magnetic core of amorphous metal having a primary coil for low voltage excitation and a secondary coil for a high voltage output to be fed to a spark plug. A high voltage is generated in the secondary coil within a short period of time following excitation thereof. The assembly senses spark ignition conditions in the combustion chamber to control the ignition event. The assembly is constructed from sub-assembly parts that can be manufactured with existing machines at reasonable cost. The assembly is then potted in a housing consisting of a high temperature polymer.

Description

CA 02253~71 1998-10-29 W O 97/41576 PCTrUS97/07069 MAGNETIC CORE-COIL ASSEMB~Y
FOR SPARK IGNITION SYSTEMS

- CROSS REFERENCE TO RELATED APPLICATIONS
This is a continl'~tion-in-part of United States application Serial No.
08/639,498, filed April 29, 1996.

BACKGROUND OF T~IE INVENTION
1. Field Of The Invention:
This invention relates to spark ignition systems for internal combustion e~ginec; and more particularly to a spark ignition system which improves performance of the engine system and reduces the size of the m~etic components in the spark ignition ~lan~ro~ er in a col,ul~ cially producible manner.

15 2. Descri~tion Of The Prior Art:
In a spark-ignition internal combustion engine, a flyback transformer is commonly used to generate the high voltage needed to create an arc across the gap of the spark plug igniting the fuel and air mixture. The timing of this ignition spark event is critical for best fuel econo",~ and low exhaust emission of environmPnt~lly 20 hazardous gases. A spark event which is too late leads to loss of engine power and loss of efflciency. A spark event which is too early leads to detonation, often called "ping" or "knock", which can, in turn, lead to detrimental pre-ignition and subsequent engine damage. Correct spark timing is dependent on engine speed and load. Each cylinder of an engine often requires di~rent timing for optimum 25 pe,ro,."ance. Different spark timing for each cylinder can be obtained by providing a spark ignition ~lansrullller for each spark plug.
.
To improve engine effici~ncy and alleviate some of the problems associated with h1appl op, ;ate ignition spark timing, some engines have been equipped withmicroprocessor-controlled systems which include sensors for engine speed, intake CA 022~3~71 1998-10-29 air temperature and pressure, engine tempel ~L-Ire, exhaust gas oxygen content, and sensors to detect"ping" or "knock". A knock sensor is ecsenti~lly an electro-mechanical tr~n~d~cer whose sensitivity is not sufficient to detect knock over the whole range of engine speed and load. The microprocessor's determination of 5 proper ignition spark timing does not always provide optimum engine performance. A better sensing of "knock" is needed.
A disproportionately greater amount of exhaust emission of hazardous gases is created during the initial operation of a cold engine and during idle and off-idle operation. Studies have shown that rapid multi-sparking of the spark plug 10 for each ignition event during these two regimes of engine operation reduces hazardous exhaust ernissions. Accordingly, it is desirable to have a spark ignition transformer which can be charged and discharged very rapidly.
A coil-per-spark plug (CPP) ignition arrangement in which the spark ignition transformer is mounted directly to the spark plug terminal, elimin~ting a 15 high voltage wire, is gaining acceptance as a method for improving the spark ignition timing of internal combustion engines. One example of a CPP ignition arran~mPnt is that disclosed by US Patent No. 4,846,129 (hereinafter "the Noble patent"). The physical ~i~meter of the spark ignition transformer must fit into the same engine tube in which the spark plug is mounted. To achieve the engine 20 diagnostic goals envisioned in the Noble patent, the patentee discloses an indirect method l,ltili7ing a ferrite core. Ideally the m~gnPtic ~. ~l mance of the sparkignition transformer is s..fficient throughout the engine operation to sense thesparking condition in the combustion challlber. Clearly, a new type of ignition transÇul,ner is needed for accurate engine diagnosis.
Engine misfiring increases hazardous exhaust emissions. Numerous cold starts without adequ~te heat in the spark plug insulator in the combustion chamber can lead to misfires, due to deposition of soot on the insulator. The electrically conductive soot reduces the voltage increase available for a spark event. A spark CA 022~3~71 1998-10-29 ignition transforrner which provides an e~ e.l~ely rapid rise in voltage can ~ ..;,e - the misfires due to soot fouling.
To achieve the spark ignition pc.fu""ance needed for succescfill operation - of the ignition and engine diagnostic system disclosed by Noble and, at the same 5 time, reduce the in-iderl~e of engine misfire due to spark plug soot fouling, the spark ignition tran~Çu""e-'s core material must have certain rragnP~ic permeability, must not m~n~tic~lly saturate during operation, and must have low m~gn~tic losses. The co",binaLion of these required p~ ùpe. Lies narrows the availability of suitable core materials. Considering the target cost of an automotive spark ignition 10 system, possible c~n~ tes for the core materiai include silicon steel, ferrite, and iron-based amorphous metal. Conventional silicon steel routinely used in utilityl,ah~fu-lner cores is inexpensive, but its m~gnetic losses are too high. Thinnergauge silicon steel with lower m~etic losses is too costly. Ferrites are in~"~pe.lsive, but their saturation inductions are normally less than 0.5 T and Curie 15 temperatures at which the core's m~n~tic induction becomes close to zero are near 200 ~C. This te.l,~elal,lre is too low considering that the spark ignition ~nsfo.l..er's upper Op~alillg tclll~tlaLLlre is acc~med to be about 180 ~C. Iron-based amorphous metal has low m~gnetic loss and high saturation induction excee~ina 1.5 T, however it shows relatively high permeability. An iron-based 20 amorphous metal capable of achieving a level of ma~netic permeability suitable for a spark ignition llarl~follller is needed. Using this material, it is possible to construct a toroid design coil which meets required output specifications and physical dimension criteria. The d;..,~ ol-~l requiltll,~,lts ofthe spark plug well limit the type of configurations that can be used. Typical ~limencional requirements for inc~ ted coil assemblies are c 25 mm di~me~r and are less than 150 mm in iength. These coil assemblies must also attach to the spark plug on both the high voltage terminal and outer ground coMc~,Lion and provide S~l~';iPnt insulation to preveM arc over. There must also be the ability to make high current connectionsto the primaries typically located on top of the coil.

CA 022~3~71 1998-10-29 SUMMARY OF T~E INVENTION
The present invention provides a m~gnetiC core-coil assembly for a coil-per-plug (CPP) spark ignition transformer which ~,ne.~les a rapid voltage rise and a signal that accurately portrays the voltage profi1e of the ignition event.
5 Generally, stated, the m~n~tic core-coil comprises a m~ etic core composed of a f~ .l.apn~tic a,l~oll~hous metal alloy. The core-coil assembly has a single primary coil for low voltage excitation and a secondary coil for a high voltage output. The assembly also has a secondaly coil comprising a plurality of core sub-assemblies that are cim~llt~neQusly enl,.g~ed via the common primary coil. The 10 coil sub-assemblies are adapted, when energized, to produce secondary voltages that are additive, and are fed to a spark plug. As thus constructed, the core-coil assembly has the capability of (i) ge,l~.dlh~g a high voltage in the secondary coil within a short period of time following ~Xçit~tiQn thereof, and (ii~ sensing spark ignition conditions in the combustion chamber to control the ignition event.
More spe~ific~ly~ the core is composed of an amorphous ferromagnetic material which exhibits low core loss and a permeability (ranging from about 100to 700). Such magnetic prope. lies are especially suited for rapid firing of the plug during a combustion cycle. Misfires of the engine due to soot fouling are ;7ed. Moreover, energy transfer from coil to plug is carried out in a highly 20 Pffici~nt manner, with the result that very little energy remains within the core after discharge. The low secondary resi.ct~nce of the toroidal design (< 100 ohms) allows the bulk of the energy to be diccirated in the spark and not in the secondary wire. This high effif~ioncy energy transfer enables the core to monitor the voltage profile of the ignition event in an accurate manner. When the magnetic core 25 material is wound into a cylinder upon which the primary and secondary wire windings are laid to form a toroidal L~ sro~ er, the signal generated provides amuch more accurate picture of the ignition voltage profile than that produced bycores exhibiting higher m~gnetic losses. A multiple toroid assembly is created that allows energy storage in the sub-assemblies via a common primary governed by the W O 97/41576 PCT~US97/07069 ind~lct~nce of the sub-assembly and its m~gnetic properties. A rapidly rising secondary voltage is induced when the primary current is rapidly decreased. The individual secondary voltages across the sub-assembly toroids rapidly increases and adds sub-assembly to sub-assembly based on the total m~gn~tic flux change of the5 system. This allows the versatility to combine several sub-assembly units wound via existing toroidal coil winding techniques to produce a single assembly with superior performance. The single assembly that consisted of a single longer toroid could not be easily and economically m~nuf~t~lred via common toroidal winding machmes.
In a p.ere-led embodiment ofthe core-coil assembly, the unit is potted (encapsulated) inside a housing to prevent high voltage arcing. In operation, the assembly is required to hold offthe open circuit voltage internally for a prolonged period of time over widely varying environment~l conditions. The open circuit voltage is the highest voltage encountered by the system. Such voltage must be 15 held off during operation over a s~lbst~nti~l number of years at which temperatures variations range from -40~C to +150~C. It is also desired that the unit be relatively resistant to cll~m:,~lc typically found in an automotive application.
There are numerous potting and housing materials that have been used by automotive m~m~f~cturers in the past. For automotive applications, the potting 20 compound, housing material and items to be enc~rs~ ted were thermally matched(roughly the same coefficient~ of thermal e Apansion CTE) by adding fillers such as glass fiber and/or minerals to the potting and houcin~ materials. The purpose was to reduce the stress and strain between the various materials in the system over the ope.~ling te~llpelaLure extremes encountered. The addition ofthe glass fiber 25 and/or minerals typically raised the dielectric constant of the material. Typical potting compounds are two component anhydrous epoxy formulations that exhibit excellent adhesion to the housing and its internal components, high temperature electrical p~,rullnance and good therrnal shock re~ ce. In order to match the CTE's of the materials over a wide tellli)elalllre range, the epoxy is form.-l~ted to have a glass transition temperature (Tg) set as high as practical to the maximumoperating temperature. An example of such an epoxy would be EP-697 m~nllf~ctllred by Thermoset. The housing material is typically made of a rugged therrnoplastic polyester which is glass fiber filled, has a high Tg and a CTE m~t~hed 5 to the epoxy. One housing material found suitable is sold by Hoescht Celanese under the trade name Vandar. The glass and/or mineral filling in such a thermoplastic polyester creates a harder, stiffer material.
The '~pencil" coil geometry is di~l~,nl than current coil geometry's in that it has a small ~ metçr and is long compared to the usually squat core-coils. This 10 large aspect ratio can lead to a great deal of internal stress being built up inside the coil if the CTE match isn't nearly perfect over the entire telllpelalLlre range. That match is difficult to achieve with differing materials over a nearly 200 ~C operating range. In a typical design, the outer section of the active components (toroidalcups) is located very close to the inner wall of the housing. The potting compound 15 effectively solidifies the parts together pinning the outer area of the components to the wall due to the large surface area of the cups and the inner wall of the housing.
In a ~oroidally wound unit, there is a long section of potting compound that fills the void between the bottom and top of the core-coil assembly up through the center of the core-coil assembly. The cli~meter of that column is related to the design of 20 the toroid and winding equipment. Due to the long length of that column and the sealed bottom of the core-coil assel"bly, a large shear force can exist between this column of potting compound and the toroidal cups. Typical two part epoxy potting compounds are very hard and inf~exible and adhere very well to the housing plastic. In this situation, a large shear stress can de-l~min~te the housing material 25 outer skin from the main body of the material, forming a crack that can bridge the primary and secondary. This occurs since the skin is resin rich and has an underlying layer with glass fiber and or mineral content. Both components are very stiff, but the toroidal cups, composed of housing material typically exhibit a lower yield strength, so they de-l~min~tes first. This can result in an internal CA 022~3~71 1998-10-29 WO 97/41S76 PCT/[1S97/07069 voltage arc that shorts the primary and seconda~y before useful voltage output can be obtained from the core-coil. The stress that creates this probl-,... is typically due to the very large thermal ~pe~alillg range ofthe core coil (~-40 ~C to +150 ~C )and large thermal gradients that can occur from therrnal shock.
A solution to this problem is to use alternative potting and housing materia}s that are more co...p~ These types of materials create far less shear stress since the materials yield and deform. A potting compound that satisfies this criteria is a two part elastomeric polyurethane system such as Epic S7207. This is a two component elaslo...c.ic polyurethane system design~od for potting electrical 10 components. It features high dielectric strength and a hardness in the mid Shore A
range and has a low dielectric constant. The Tg for this material is about -25 ~C
and the CTE is 209x10~ cm/cml~C . This material is so~, compliant and el~ctic~lly deforms. Materials ofthis type typically exhibit low Tg's co.l.paled to t~,vo component epoxies and have much larger CTEs since they are used above the TB
15 point. Another potting material is a two part silicone rubber compound such as S-12~4 sold by Castall. One housing material that possesses good therrnal characteristics and is co~ is r ern~l~oy PX603Y produced by Mitsubishi Fntgineering Plastics. T ern~lloy iS a PPE/PP (Polyphenylene ether/Polypropylene) blend that is flexible, has a low dietectric constant, good electrical properties, good 20 chemical reci~t~nce and is injection moldable. The material is only very slightly crystalline, but exhibits good and stable mec.h~nie~l properties. Such material and other materials like it, inrlll~in~ Polymethylpentene/Polyolefin blends and Polycylcolefin/Polyolefin blends, are high use tc."~o, a~lre polymers. The Lemalloy material and potting compound bond together very well under conditions 25 wherein the surfaces have been propt,ly pl~,a,~d and plasma cleaned prior to potting. Core-coil assemblies made from these materials have survived many thermal shock cycles forrn ~0 ~C to +~50 ~C in the pencil coil arrangement even though there is a very large CTE mis-match between components.

CA 022~3~71 1998-10-29 BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages will become apparent when reference is made to the following detailed description of the pre~l~ed embodiments ofthe invention and the acco,llpa"ying drawings, in S which:
FIG. I is an assembly procedure ~-ide~ine drawing showing the assembly method and connections used to produce the stack arrangement, coil assembly of the present invention;
Fig.2A is an assembly drawing illustrating side and top views of the stack 1 0 arrangement;
Fig. 2B is an assembly illustrating side and top view of the encapsulated stack arr~ment; and Fig. 3 is a graph showing the output voltage across the secondary for the Ampere-turns on the primary coil of the assembly shown in Fig. 1.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Referring to Figure 1 of the drawings, the m~gnetic core-coil assembly 34 comprises a m~enetic core 10 composed of a ferrom~gnetic amorphous metal alloy. The core-coil assembly 34 has a single primary coil 36 for low voltage 20 excitation and a secondary coil 20 for a high voltage output. The core-coil assembly 34 also has a secondary coil 20 comprising a plurality of core sub-assemblies (toroidal units) 32 that are s~ lt~neously energized via the common primary coil 36. The core-coil sub-assemblies 32 are adapted, when energized, toproduce secondary voltages that are additive, and are fed to a spark plug. As thus 25 constructed, the core-coil assembly 34 has the capability of (i) gen~ ing a high voltage in the secondary coil 20 within a short period of time following excitation thereof, and (ii) sensing spark ignition conditions in the combustion chamber tocontrol the ignition event.

CA 022~3~71 1998-10-29 The magnetic core 10 is based on an amorphous metal with a high m~gn-otic induction, which includes iron-base alloys. Two basic forms of a core 10 are noted. They are gapped and non-gapped and are both referred to as core 10. The gapped core has a discontinuous m~ençtic section in a magnetically continuous S path. An example of such a core l O is a toroidal-shaped m~netic core having asmall slit commonly known as an air-gap. The gapped configuration is adopted when the needed permeability is considerably lower than the core's own permeability as wound. The air-gap portion of the magnetic path reduces the overall permeability. The non-gapped core has a m~enetic permeability similar to10 that of an air-gapped core, but is physically continuous, having a structure similar to that typically found in a toroidal m~enetic core. The apparent presence of anair-gap uniformly distributed within the non-gapped core 10 gives rise to the term "distributed-gap-core" . Both gapped and non-gapped designs function in this core-coil assembly 34 design and are interchangeable as long as the effective 15 permeability is within the required range. Non-gapped cores 10 were chosen for the proof of principle of this modular design, however the design is not limited to the use of non-gapped core material.
The non-gapped core lO is made of an amorphous metal based on iron alloys and processed so that the core's m~enetic permeability is between 100 and20 500 as measured at a frequency of approximately I kHz. Leakage flux from a distributed-gap-core is much less than that from a gapped-core, em~n~tine less undesirable radio frequency inte~rerence into the surro~m~inee Furthermore, because of the closed m~enetic path associated with a non-gapped core, signal-to-noise ratio is larger than that of a gapped-core, making the non-gapped core 25 especially well suited for use as a signal transformer to di~nose engine combustion processes. An output voltage at the secondary winding 20 greater than 10 kV for spark ignition is achieved by a non-gapped core l O with less than 60 Ampere-turns of primary 36 and about 110 to 160 turns of secondary winding 20.

CA 022~3~71 1998-10-29 Open circuit outputs in excess of 25 kV can be obtained with c 180 Arnpere-turns.
Previously de.nonsLl~led coils were comprised of ribbon amorphous metal material that was wound into right angle cylinders with an ID of 12 mm and an ODof 17 mm and a height of 15.6 rnm stacked to form an effective cylinder height of 5 nearly 80 mm. Individual cylinder heights could be varied from a single height of near 80 mm to 10 mm as long as the total length met the system requirements. It is not a requirement to directly adhere to the dimensions used in this example. Large variations of design space exist according to the input and output requirements.The final constructed right angle cylinder formed the core of an elongated toroid.
10 Insulation between the core and wire was achieved through the use of high temperature resistant moldable plastic which also doubled as a winding form f~cilit~ting the winding of the toroid. Fine gauge wire was used to wind the required 110-160 secondary turns. Since the output voltage of the coil could exceed 25 kV which ~~ sents a winding to winding voltage in the 200 volt range, 15 the wires could not be significantly overlapped. The best pel~lllling coils had the wires evenly spaced over appro~il,.alely 300 degrees ofthe toroid. The remaining60 degrees was used for the primary windings. One of the drawbacks to this type of design was the aspect ratio of the toroid and the number of secondary turns required for general operation. A jig to wind these coils was required to handle20 very fine wire (typically 39 gauge or higher), not .cignific~ntly overlap these wires and not break the wire during the winding operation. Typical toroid winding m~.hines (Universal) are not capable of winding coils near this aspect ratio due to their h~he~e.lL design. Alternative designs based on shuttles that are pushed through the core and then brought around the outer perimeter were required and 25 had to be custom produced. Typically the time to wind these coils was very long.
The elongated toroid design, though functional would be difficult to mass produce at a sufficiently low cost to be co..~ne~,ially attractive.
An alternative design breaks the original design down into a smaller component level structure in which the components can be routinely wound using CA 022~3~71 1998-10-29 WO 97/41576 ~ I PCT/US97/07069 existing coil winding m~chin~s The concept is to take core sections of the same base amorphous metal core material of m~n~gç~ble size and unitize it. This is accomplished by forming an insulator cup 12 that allows the core 10 to be inserted into it and treating that sub-assembly 30 as a core to be wound as a toroid 32. The same number of secondary turns 14 are required as the original design. The finalassembly 34 can consist of a stack of a sllffirient number (1 or greater) of these structures 32 to achieve the desired output characteristics with one significantchange. Every other toroid unit 32 must be wound oppositely. This allows the output voltages to add. A typical structure 34 would consist of the first toroidal unit 16 being wound counterclockwise (ccw) with one output wire 24 acting as thefinal coil assembly 34 output. The second toroidal unit 18 would be wound clockwise (cw) and stacked on top of the first toroidal unit 16 with a spacer 28 to provide adequate insulation. The bottom lead 42 of the second toroidal unit 18 would attach to the upper lead 40 (rern~ining lead) ofthe first toroidal unit 16.
The next toroidal unit 22 would be wound ccw and stacked on top of the previous 2 toroidal units 16,18 with a spacer 28 for insulation purposes. The lower lead 46 of the third toroidal unit would connect to the upper lead 44 of the second toroidal unit. The total number of toroidal units 32 is set by design criteria and physical size requirements. The final upper lead 24 forms the other output of the core-coil assembly 34. These secondary windings 14 of these toroidal units 32 are individually wound so that appro~imalely 300 ofthe 360 degrees ofthe toroid is covered. The toroidal units 32 are stacked so that the open 60 degrees of each toroid unit 32 are vertically aligned. A comrnon primary 36 is wound through this core-coil assembly 34. This will be referred to as the stacker concept.
The voltage distribution around the original coil design resembles a variac with the first turn being at zero volts and the last tum is at full voltage. This is in effect over the entire height of the coil structure. The primary winding kept isolated from the secondary windings and is located in the center of the 60 degree free area of the wound toroid. These lines are eecenti~lly at low potential due to CA 022~3~71 1998-10-29 the low voltage drive conditions used on the primary. The highest voltage stresses occur at the closest points of the high voltage output and the primary, the secondary to secondary windings and the secondary to core. The highest electric field stress point exists down the length of the inside of the toroid and is field S çnh~n~ed at the inner top and bottom of the coil. The stacker concept voltage distribution is slightly di~rt.ll. Each individual core-coil toroidal unit 32 has the same variac type of distribution, but the stacked distribution of the core-coil assembly 34 iS divided by the number of individual toroidal units 32. If there are 3 toroidal units 32 in the core-coil assembly 34 stack, then the bottom toroidal unit 16 will range from V to 2/3 V, the second toroidal unit 18 will range from 2/3 V to 1/3 V and the top toroidal unit 22 will range from 1/3 V to 0 V. This configuration lessens the area of high voltage stress.
Another issue with the original coil design is capacitive coupling of the outputthough the insulator case to the outside world. The output voltage waveform has a short pulse component (typically 1-3 microseconds in duration with a 500 ns rise time) and a much longer low level output component (typically 100-150 microseconds duration). Some of the fast pulse output component capacitively couples out through the walls of the insulator. The variac effect can noted by observing corona on the outer shell. The capacitive coupling can rob the output 20 to the spark plug by partially .chllnting it through the case to ground. This effect is only a problem at the very high voltage ranges where it can reduce the open circuit voltage of the device by corona discharge. The stacker arrangement voltage distribution is di~renl and allows the highest voltage section to be located on the top or bottom of the core-coil assembly 34 depending on the grounding 25 configuration. The advantage in this design is that the high voltage section can be placed right at the spark plug deep in the spark plug well. The voltage at the top of the core-coil assembly 34 would maximize at only 1/3 V for a 3 stack unit.
Magnetic cores composed of an iron-based amorphous metal having a saturation induction e~ee~linp I . 5 T in the as-cast state were prepared. The cores CA 022~3~71 1998-10-29 had a cylindrical fomm with a cylinder height of about 15.6 mm and outside and inside diameters of about 17 and 12 mm, respectively. These cores were heat-treated with no external applied fields. Figure 1 shows a procedure guideline drawing of the construction of a three stack core-coil assembly 34 unit. These S cores 10 were inserted into high temperature plastic insulator cups 12. Several of these units 30 were m~hine wound cw on a toroid winding m~chine with 110 to 160 turns of copper wire forming a secondary 14 and several were wound ccw.
The first toroidal unit 16 (bottom) is wound ccw with the lower lead 24 acting as the system output lead. The second toroidal unit 18 is wound cw and its lower lead 42 is connected to the upper lead 40 of the lower toroidal unit 16. The third toroidal unit 22 is wound ccw and its lower lead 46 is connected to the upper lead 44 of the second toroidal unit 18. The upper lead 26 of the third toroidal unit 22 acts as the ground lead. Plastic spacers 28 between the toroidal units 16, 18, 22 act as voltage standoffs. The non-wound area of the toroidal units 32 are vertically 15 aligned. A common primary 36 is wound through the core-coil assembly 34 stackin the clear area. This core-coil assembly 34 is encased in a high temperature plastic housing with holes for the leads. This assembly is then vacuum-cast in an acceptable potting compound for high voltage dielectric integrity. There are many altemative types of potting materials. The basic requirements of the potting 20 compound are that it possess sufficient dielectric ~lcn~ , that it adheres well to all other materials inside the structure, and that it be able to survive the stringent en~,ho~ cnt requirements of cycling, tclllpelalllre~ shock and vibration. It is also desirable that the potting compound have a low dielectric constant and a low loss tangent. The housing material should be injection moldable, inexpensive, possess a 25 low dielectric constant and loss t~n~ent, and survive the same environm~ns~l conditions as the potting compound.
In Figure 2A there is shown a side and top view of the stacker assembly 34 prior to encapsulation. Figure 2B shows a side and top view of the stacker assembly 34 erlc~rs~ ted in the final assembly 100. The stacker assembly 34 is _.~

CA 022~3~71 1998-10-29 placed inside a hollow tubing housing 50 that is made from polymeric materials having high use temperature properties as previously described. A bottom section55 has a connector 70 that interfaces to the spark plug and seals to the housing 50.
Output lead 24 is connected to connector 70 to form an electrical path to the spark 5 plug. Output lead 26 can be brought out of the assembly l O0 and connected to the engine ground or the return of the sparkplug or similar point to form a closed electrical path for the secondary discha~ging through the spark gap. Potting compound 60 is poured into the housing 50 under m~n~f~ct lrer~s recommPnd~tions. Such potting compound plope~Lies were previously ~iccussed 10 Primary leads 36 extend beyond the body ofthe housing and potting so that they can be used as the primary ofthe core-coil. Toroidal cup 12, housing 50 and bottom section 55 are composed ofthe housing materials described hereinabove.
In order to promote adhesion of the potting compound 60 with housing 50, toroidal cup 12, bottom section 55 and other internal components, the parts are 15 plasma cleaned prior to potting, as prescribed by m~nllf~cturers of plasma cleaning m~chines A current was supplied in the primary coil 36, building up rapidly within about 25 to 100 ,usec to a level up to but not limited to 60 amps. Figure 3 shows the output ~tt~ined when the primary current is rapidly shut off at a given peak20 Ampere-turn. The charge time was typically < 120 microseconds with a voltage of 12 volts on the primary switching system. The output voltage had a typical shortoutput pulse duration of about 1.5 microseconds FWHM and a long low level tail that lasted appro,~;,.,~tely 100 microseconds. Thus, in the m~gnP.tic core-coil assembly 34, a high voltage, exceedin~ 10 kV, can be repeatedly generated at time 25 intervals of less than 150 ~sec. This feature is required to achieve the rapid multiple sparking action mentioned above. Moreover, the rapid voltage rise produced in the secondary winding reduces engine misfires resulting from soot fouling..

CA 022~3S71 1998-10-29 W O 97t41576 -15- PCT~US97107069 In addition to the advantages relating to spark ignition event described above, the core-coil assembly 34 of the present invention serves as an engine diagnostic device. Because ofthe low magnetic losses ofthe m~gnetic core 10 of - the present invention, the primary voltage profile reflects faithfully what is taking S place in the c~lm~ tive secondary windings. During each rapid flux change inducing high voltages on the secondary, the primary voltage lead is analyzed during the firing duration, for proper ignition characteristics. The resulting data are then fed to the ignition system control. The present core-coil assembly 34 thus elimin~tes the additional m~gnetic element required by the system disclosed in the 10 Noble patent, wherein the core is composed of a ferrite material.
The following example is presented to provide a more complete underst~n~iine of the invention. The specific techniques conditions, materials, proportions and reported data set forth to illustrate the principles and practice of the invention are exemplary and should not be construed as limiting the scope of15 the invention.

EXAMPLE
An amorphous iron-based ribbon having a width of about 15.6 mm and a thiçkness of about 20 ~m was wound on a machined stainless steel mandrel and 20 spot welded on the ID and OD to m~int~in tolerance. The inside di~meter of 12mm was set by the mandrel and the outside di~meter was sPlected to be 17 rnm.
The finished cylindrical core weighed about 10 grams. The cores were ~nne~led ina nitrogen atmosphere in the 430 to 450 ~ C range with soak times from 2 to 16 hours. The allnt~led cores were placed into insulator cups and wound on a toroid25 winding m~r.hine with 140 tums of thin gauge in.~ t~d copper wire as the secondary. Both ccw and cw units were wound. A ccw unit was used as the base and top units while a cw unit was the middle unit. Tn~ tor spacers were added between the units. Four turns of a lower gauge wire, foll.ling the primary, werewound on the toroid sub-assembly in the area where the secondary windings were CA 022~3~71 1998-10-29 not present. The middle and lower unit's leads were connected as well as the middle and upper units leads. The assembly was placed in a high temperature plastic housing and was potted. With this configuration, the secondary voltage was measured as a function of the primary current and number of primary turns, S and is set forth below in Figure 3.
Having thus desc- ;bed the invention in rather full detail, it will be understood that such detail need not be strictly adhered to but that further changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

Claims (10)

What is claimed is:

1. A magnetic core-coil assembly for generating an ignition event in a spark ignition internal combustion system having at least one combustion chamber.
comprising:
a. a magnetic core composed of a ferromagnetic amorphous metal alloy.
said core having a primary coil for low voltage excitation and a secondary coil for a high voltage output;
b. said secondary coil comprising a plurality of core sub-assemblies that are simultaneously energized via said common primary coil, c. said coil sub-assemblies being adapted, when energized, to produce secondary voltages that are additive, and are fed to a spark plug;
d. said core-coil assembly having the capability of (i) generating a high voltage in the secondary coil within a short period of time following excitation thereof, and (ii) sensing spark ignition conditions in the combustion chamber to control the ignition event;
e. said core-coil assembly being potted inside a housing using a potting compound composed of an anhydrous, two component epoxy having strong adhesion to said core-coil assembly, high temperature electrical performance and good thermal shock resistance; and f. said housing being composed of a thermoplastic polyester that can be adhesively secured by said potting compound, is glass fiber filled, has a Tg near the maximum operating temperature of said assembly and a coefficient of thermal expansion matched to that of said epoxy and is injection moldable.

2. A magnetic core-coil assembly as recited in claim 1, wherein said magnetic core is fabricated by heat-treating said ferromagnetic amorphous metal alloy.

3. A magnetic core-coil assembly as recited in claim 1, wherein the magnetic core comprises segmented cores.

4. A magnetic core-coil assembly as recited in claim 1, wherein the output voltage in the secondary coil reaches more than 10 kV with a primary current of less than about 70 Ampere-turns and more than 20 kV with a primary current of 75 to 200 Ampere-turns within 25 to 150 µsec.

5. A magnetic core as recited in claim 2, wherein said ferromagnetic amorphous metal alloy is iron based and further comprises metallic elements including nickel and cobalt, glass forming elements including boron and carbon and semi-metallic elements, including silicon.

6. A magnetic core-coil assembly as recited in Claim 1, consisting of a plurality of individual sub-assemblies, each being comprised of a toroidally wound section with a secondary winding, said sub-assemblies being arranged so that theresulting assembly voltage is the sum of voltages from the individual sub assemblies upon actuation by said common primary.

7. A magnetic core-coil assembly as recited in Claim 1, said assembly having an internal voltage distribution that is segmentally stepped from bottom to top, the number of segments being determined by the number of sub-assemblies.

8. A magnetic core-coil assembly for generating an ignition event in a spark ignition internal combustion system having at least one combustion chamber, comprising:

a. a magnetic core composed of a ferromagnetic amorphous metal alloy, said core having a primary coil for low voltage excitation and a secondary coil for a high voltage output;
b. said secondary coil comprising a plurality of core sub-assemblies that are simultaneously energized via said common primary coil;
c. said coil sub-assemblies being adapted, when energized, to produce secondary voltages that are additive, and are fed to a spark plug;
d. said core-coil assembly having the capability of (i) generating a high voltage in the secondary coil within a short period of time following excitation thereof, and (ii) sensing spark ignition conditions in the combustion chamber to control the ignition event;
e. said core-coil assembly being potted inside a housing using a potting compound composed of a two part elastomeric polyurethane system having strong adhesion to said core-coil assembly, high dielectric strength, hardness in the mid Shore A range and a low dielectric constant; and f. said housing being composed of a flexible high use temperature plastic that can be adhesively secured by said potting compound, has a high dielectric strength, low dielectric constant, good electrical properties and chemical resistance.

9. A magnetic core-coil assembly as recited in claim 8, wherein said housing material is a member of the group consisting of Polyphenylene ether/Polypropylene blends, Polymethylpentene/Polyolefin blends and Polycylcolefin/Polyolefin blends.

10. A magnetic core-coil assembly as recited in claim 8, wherein said potting material is a silicone rubber based potting compound.