CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority to U.S. Provisional Application Serial No. 61/984,502, filed April 25, 2014 and US Non-provisional Application Serial No. 14/691,502, filed April 21, 2014 , the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[002] The present invention relates generally to engine ignition systems and more particularly to a high speed capacitor discharge ignition system.

BACKGROUND

[003] It is well known in the prior art that capacitor discharge ignition (hereinafter referred to as "CDI") is the acknowledged solution for automotive enthusiasts wanting a high energy ignition circuit. CDI gave a really hot spark which would fire virtually any spark plug no matter how fouled it was. Tens of thousands of enthusiasts installed them on their cars and hence forward swore by them.

[004] More specifically, capacitor discharge ignition systems provide ignition sparking which is effective over the entire speed range of any engine, right from cranking speed to well beyond the maximum speed of even higher performance engines. There is a linear power consumption increase with engine speed from stall to maximum engine speed. The power characteristics are very different as compared to the inductive ignition system where the power consumed is highest at low speed and then decreases with increasing speed. The effectiveness of the capacitor discharge system is such that the available secondary voltage is higher than for any of the inductive systems and it remains approximately constant over the whole speed range at approximately 27 kilovolts (kV). Therefore, the sparks produced have relatively large and desirable energy content. Because the discharge of the storage capacitor is so rapid, the voltage rise is extremely fast. Thus, even when the spark plug electrodes and insulator have conducting deposits over their surfaces, the secondary voltage surge is so rapid that sparking is not hindered.

[005] However, an inherent limitation with the conventional capacitor discharge ignition is the duration of the spark, which is extremely short (0.1 to 0.2 milliseconds (ms)), therefore it is desirable to produce many sparks in a short period of time (which the conventional capacitor discharge ignition is unable to do). Also, the large surplus in secondary voltage of CDI permits much wider spark-plug electrode gaps to be used, compared with other ignition systems and, as a result, partially compensates for the short time available to ignite the air-fuel mixture.

[006] Ultimately, CDI fell into disuse for mainstream cars because of the introduction of lean fuel mixtures in an attempt to meet rising anti-pollution standards. The very fast and very short spark of CDI was not all that good at igniting lean mixtures. Car manufacturers introduced transistor-assisted ignition with long spark durations to ensure that lean mixtures did burn properly. There was one CDI design which attempted to overcome the lean mixture drawback and that was the so-called "multiple spark discharge" system. However, it was a complex and expensive design which never really caught on in production cars.

[007] Because the 12V to 44 V DC inverters of the time used relatively slow transistors, the inverter frequency was typically only 2 kilohertz (kHz). This sets an upper limit on the maximum of 3 sparks per ignition event, as the inverter needs a couple of cycles of operation after each discharge in order to recharge the capacitor. An ignition event is defined as the number of additional sparks after the first spark is needed for ignition. [008] Current CDls used an SCR (silicon controlled rectifier) to discharge the capacitor and these are typically rated for an AC supply frequency of 400 Hz maximum. This too set a limit on the maximum number of sparks per ignition event. A rather serious drawback was that most systems would not operate when the battery was low. This meant that while the battery might be able to slowly crank the engine, the CDI's inverter would not start and hence there would be no spark. It is very difficult to design an 8 Volt DC to 300 Volt DC converter that does the job. Another factor which limited the inverter operating frequency was the speed of the rectifier diodes.

[009] High speed, fast recovery diodes were expensive and so, even if the inverter could have run much faster, the standard rectifier diodes could not have handled the high frequency output. Referring now to FIGURE 1 there is shown a diagram of a basic conventional Kettering ignition system. The primary 100 is a single winding and the dwell is normally several milliseconds due to considerable primary inductance. The cam 103 opens the points 102 causing the spark in the spark plug by way of the high voltage secondary 101. FIGURE 4 is a graph illustrating the operation of the Kettering ignition system shown in FIGURE 1. More particularly, FIGURE 4 illustrates the long dwell time 402, the charge 401 building up in the coil, and the high voltage 400 produced in the secondary winding to fire the spark plug.

SUMMARY

[010] An engine ignition system comprising an ignition coil, an energy storage device, and switching circuitry is disclosed. The ignition coil comprises a plurality of primary windings connected in parallel and a secondary winding in a spaced relationship to the plurality of primary windings wherein the secondary winding is electrically connectable to a spark plug. The energy storage device consists of a combination of a vehicle battery electrically connected in parallel with a capacitor. The energy storage device is also electrically connected to the plurality of primary windings to selectively produce an electrical current simultaneously through each of the plurality of primary windings. In use, the switching circuitry selectively turns on and off the electrical current from the energy storage device through the plurality of primary windings. Turning off the electrical current from the energy storage device through the plurality of primary windings collapses a stored magnetic field thereby inducing an electrical current through the secondary winding causing the spark plug to produce a spark.

[Oil] The electrical current from the energy storage device through the plurality of primary windings may be turned on and off in a predetermined variable time period at a maximum engine RPM of 15,000 at which an average of the electrical current from the vehicle battery through the plurality of primary windings is approximately one (1) amp and no more than ten (10) amps. In another preferred embodiment, by selecting a number of windings, a number of turns for each winding, and/or a wire gauge for the plurality of primary windings, the electrical current from the energy storage device through the plurality of primary windings are at least 20 amps wherein the primary windings are turned on for no more than 50 microseconds.

[012] In yet another preferred embodiment, the switching circuitry selectively turns off the electrical current delivered from the energy storage device to the plurality of primary electrical windings in less than one (1) microsecond. In still yet another preferred embodiment, the switching circuitry selectively turns off the electrical current delivered from the energy storage device to the plurality of primary electrical windings in less than one hundred (100) nanoseconds.

[013] The switching circuitry may comprise a solid state switch and a gate driver. The solid state switch has a turn-off time of less than 1 microsecond, and is electrically connected to the plurality of primary electrical windings such that electrical current flows through the plurality of primary electrical windings when the solid state switch is on and electrical current does not flow through the plurality of primary electrical windings when the solid state switch is off. The gate driver turns the solid state switch on and off in response to a control signal from a computer. The control signal can vary as to pulse spacing and number of pulses per ignition event. An ignition event is the exact time or angle in a crankshaft rotation where a spark is needed to initiate combustion. The energy storage device may comprise one or more batteries, one or more capacitors, or combinations thereof. The plurality of primary electrical windings may comprise four or five windings each having less than 100 turns (and typically 5-20 turns).

BRIEF DESCRIPTION OF THE DRAWINGS

[014] The foregoing summary, as well as the following detailed description of the disclosure, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[015] FIGURE 1 is a diagram of a basic conventional Kettering ignition system.

[016] FIGURE 2 is a schematic diagram of a high speed capacitor discharge ignition system, in accordance with an embodiment of the invention.

[017] FIGURE 3 is an isometric diagram of a high speed capacitor discharge ignition system, in accordance with an alternative embodiment of the invention.

[018] FIGURE 4 is a graph illustrating the operation of the Kettering ignition system shown in FIGURE 1.

[019] FIGURE 5 is a diagram in accordance with embodiments of the invention showing the number of sparks per ignition event as a function of RPM compared with existing capacitor discharge ignition systems.

[020] FIGURE 6 is a diagram in accordance with embodiments of the invention showing the current build up in the total primary windings as a function of microseconds short of the time one of the sparks occurs. [021] FIGURE 7 is an oscilloscope trace in accordance with embodiments of the invention showing the total voltage across the primary windings as a function of microseconds starting with solid state switch on and ending with solid state switch off and the occurrence of one of the sparks.

DETAILED DESCRIPTION

[022] The present invention is directed to a high speed capacitor discharge ignition system and is intended to be used in the coil-on-plug configuration. In accordance with the preferred embodiments of the present invention, the high speed capacitor discharge ignition system is capable of producing a much greater number of sparks per ignition event than prior art ignition systems and multi spark capacitor discharge ignitions systems and may be used to provide ignition for any suitable engine, including but not limited to two-stroke and four-stroke motors on cars, trucks, buses, motor bikes, outboards, go-karts and the like.

[023] The high speed capacitor discharge ignition system of the present invention may be used to provide ignition for older cars which don't have lean mixtures and which may be particularly hard, if not impossible, to start when an engine's ignition system gets wet and may also be used to provide ignition for racing applications where multiple spark discharge systems are desirable. The high speed capacitor discharge ignition system is particularly desirable to be used to provide ignition for high RPM (revolution per minute) Wankel engines.

[024] The high speed capacitor discharge ignition system of the present invention provides both a very low cost capacitor discharge ignition system and a high energy "multiple spark discharge" to cope with engines which have very high RPM rates. More particularly, it is intended for use with two stroke engines, high performance four strokes, older vehicles and high RPM Wankel engines in the coil-on-plug mode, although it may also be used on any suitable engine wherein the engine uses a distributor as part of its ignition system. [025] In some embodiments of the invention, the high speed capacitor discharge ignition system of embodiments of the invention is capable of producing multiple spark output at 15,000 RPM for a V8 or greater. In other words, the the high speed capacitor discharge ignition system of embodiments of the invention is capable of producing sparks with spacings less than 100 micro seconds apart at 15,000 RPM and as far apart as desirable at 500 RPM.

[026] It should be understood that the high speed capacitor discharge ignition system of the present invention utilizes simple low cost circuitry chosen for high efficiency (above 90%) having minimum heat generation. Moreover, the high speed capacitor discharge ignition system of the present invention has many advantages over prior art ignition systems, including but not limited to the following:

1. No high voltage power supply as required by prior art capacitor discharge systems resulting in simplification of the circuitry thereby reducing circuit cost while improving its efficiency.

2. No expensive high voltage bipolar capacitor as required by prior art capacitor discharge systems wherein low cost electrolytic capacitors are used instead.

3. No need for a long dwell time as required by prior art coil-on-plug transistorized Kettering based ignition systems.

[027] More, specifically, a long dwell time can preclude rapid repetitive multiple sparks at high engine RPM and is also a problem for vehicles having an electronic fuel injection system. In such vehicles, a vehicle computer software system is employed which must know the RPM and use that information to calculate the correct ignition times. Also, the computer software must anticipate the correct crank angle adjusting for the 2 millisecond delay to fire the spark plugs. This two (2) millisecond delay translates into many different crankshaft degrees when a two cycle engine is running at 7500 RPM with a single revolution time of eight milliseconds.

[027] Moreover, a long dwell time complicates the needed computer software which in turn consumes more processor time. In contradistinction, the high speed capacitor discharge ignition system of the present invention is capable of firing the spark plug within thirty (30) microseconds or less (short dwell time) only when it is needed. More specifically, by providing a short dwell time this means that the spark plug is fired only when it is needed and therefore no calculations are required to compensate for a long dwell time, as explained above. The computer software is now modified and improved in that it has the option of firing the plugs every few crankshaft degrees providing for a more complete combustion, resulting in less fuel burn and lower emissions being produced from the engine.

[028] Referring now to FIGURE 2, there is shown and illustrated the high speed capacitor discharge ignition system of the present invention. It should be noted that the major difference applicant's invention and the prior art Kettering system shown in FIGURE 1 is the plurality of primary windings connected in parallel 200 as shown in FIGURE 2 as opposed to the single primary wiring 100 in FIGURE 1. The secondary winding 201 and associated core 207 are similar or identical to the prior art Kettering system shown in FIGURE 1. In one preferred embodiment of the present invention, the secondary winding 201 has 9600 turns. In another embodiment of the invention, the secondary winding 201 has 12,000 turns. Other numbers of turns may be used ranging from 500 to 20,000 turns for secondary winding plurality of primary windings connected in parallel. [029] The ignition device 207 of the present invention may be fabricated using a laminated steel core, or a ferrite core, wherein the solid state switch 203 is conventional and bought off the shelf. A 20,000 micro farad capacitor 202 is used in one embodiment and enables the high speed capacitor discharge ignition system of the present invention to avoid using a large gage wire from the battery to coil 207. It should be understood that eighteen (18) gage wire is normally used to power the prior art Kettering ignition system and can only draw up to six (6) amps. However, by using that gage wire in the high speed capacitor discharge ignition system of the present invention would present a significant voltage drop as the peak primary windings 200 current in applicant's invention is up to one hundred (100) amps. The standard 12 volt lead acid battery provide in almost all vehicles is more than able to supply this current as that is typical of starter motor use wherein the use of capacitor 202 makes this unnecessary. In one preferred embodiment of the present invention, five turns of eighteen (18) gage wire 208 is used in each of the primary windings 200.

[030] Turning once again to FIGURE 2, current off the shelf solid state switches 203 are capable of pulse currents of three hundred (300) amps or more. A solid state switch trigger 204 provides the high pulse current to provide the considerable input capacitance charge of solid state switches. The first pulse 206 in the pulse train from the control of the vehicle computer software occurs at about twenty (20) degrees before top dead center. The second pulse 205 occurs one revolution later in a two cycle and Wankel engine and two (2) revolutions later in a four cycle engine.

[031] Turning yet once again to FIGURE 2, the high speed capacitor discharge ignition system utilizes a low inductance primary winding in association with a high voltage secondary winding 201 having by way of example, several thousand turns (in one embodiment of the invention, the secondary winding 201 has 10,000 turns of 36 gage wire). Additionally, a high speed solid state switch (which may be, for example, a 250V, 60A MOSFET with a 50 nanosecond turn off time), a high speed gate driver (which may be, for example, model TC4428 as illustrated), and a capacitor (which may be, for example, a 20,000 micro farad, 25V electrolytic capacitor) may be used in accordance with the present invention.

[032] It should be understood that the low inductance of the plurality of primary windings 200 of the high speed capacitor discharge ignition system of the present invention allows for a maximum current in 30 microseconds or less which is about seventy 70 times faster than the prior art Kettering ignition system (the exact inductance and therefore the exact dwell time may vary, depending on the desired spark rate capability, number of turns, and the wire size.) In some embodiments of the invention, the dwell time may be about 20 microseconds. In any event, the high speed capacitor discharge ignition system of embodiments of the invention generally has a dwell time of thirty (30) microseconds or less, which is still about seven (70) times shorter than prior art Kettering ignition systems at (2) milliseconds. The low inductance primary 200 consists of multiple low inductance windings connected in parallel and may have in one preferred embodiment four windings, each winding having ten turns as shown in FIGURE 2.

[033] Additionally, it should be understood that the high speed capacitor discharge ignition system of the present invention may have roughly the same total number of turns as the prior art Kettering system, but the primary is broken into several independent, parallel windings as shown in FIGURE 2. The total or final DC resistance is defined as one divided by the sum of all the independent winding resistances, each individual winding resistance divided into one. In the four winding case illustrated as described above, each winding would have a DC resistance of 2 ohms divided by 4, which is 0.5 ohms. The formula for resistors in parallel is one (1) over the sum of each resistor divided into one (1) or (1/Rfmai resistance = 1/ri + l/r ₂ + l/r ₃ + l/r ₄ .) In this example, using four windings would be two (2) times four (4), which is eight (8). Eight (8) divided into one (1) is 0.125 Ohms. Therefore, in this example using four windings as defined would result in a max primary current of 96 amps. Accordingly, this combination of current and number of turns would be more than enough to saturate the core 207 with magnetic flux. One of the major benefits and improvements over the prior art of using multiple or a plurality of primary windings 200 is that the inductance of each winding is drastically reduced thereby allowing the current to reach the max possible current allowed by the DC resistance in mere microseconds. This is graphically illustrated in FIGURES 6 and 7 wherein the core flux saturation is shown as a spike in the current just prior to the spark. The formula for inductances in parallel is the same as for resistors in parallel.

[034] A characteristic or definition of core flux saturation is when the magnetism of the core does not increase with increased current. It should be understood that core flux saturation is not part of applicant's invention. The core material and size are chosen such that saturation never occurs or if it does occur it does not affect the outcome as it only last for several microseconds. It is inconsequential to waste a little extra current by moving into the core flux saturation region. What limits the maximum current in applicant's invention is the DC resistance of the primary windings.

[035] In still yet another preferred embodiment of the invention, different numbers of windings and turns may be used for primary 200, as long as the primary 200 is constructed to allow current to build up in the desired time to achieve the desired spark rate during an ignition event. By way of example but not of limitation, the primaries 200 of the high speed capacitor discharge ignition system shown in FIGURE 2 each comprise four windings 200, each winding 200 having ten turns and use eighteen (18) gage wire.

[036] Referring now to FIGURE 3 there is shown an isometric view of one preferred embodiment of a high speed capacitor discharge ignition system in accordance with the present invention. Part 300 is the connector post for the spark plug wire. Part 301 is an insulator for said post. Part 302 is a printed circuit board with wide copper traces consistent with the high currents involved. Part 303 is a solid state switch driver as described above. Part 304 is the solid state switch as described above. Part 305 is the primary coil bobbin showing five separate primary windings. Part 306 is the high voltage coil located concentric with the primary windings and magnetic core 309. Part 307 and 308 are 10,000 micro-farad electrolytic capacitors (together providing the 20,000 micro farad capacity as described above).

[037] In operation, the high speed capacitor discharge ignition system receives an ignition pulse input (from either a vehicle computer system for mass produced vehicles that have engine computers or from custom computer circuitry used with carburetor-equipped engines received by utilizing the high speed gate driver 204. Based on the ignition pulse input, the gate driver 204 turns the solid state switch 203 on and off. When the solid state switch 203 is on, current from the capacitor 202 (which may be, for example, a 20,000 micro farad, 25V capacitor capable of producing a 100 amp current pulse through the primary, or may be two 10,000 micro farad capacitors) flows through the primary winding 200. As described above, the low inductance of the primary 200 enables the desired current to build up in the primary 200 in about 30 microseconds, as shown in FIGURES 6 and 7. After the desired current has built up in the primary 200 (and at the desired spark time), the solid state switch 203 is turned off which causes a high current spark to be generated in the secondary 201. The operation of the high speed capacitor discharge ignition system of the present invention is similar to the operation of the prior art or conventional Kettering systems, only much faster.

[038] Turning once again to FIGURE 6, there is graphically illustrated the current build up in the total primary windings as a function of microseconds prior to the time the spark occurs wherein 600 indicates the start of the coil charge and 601 indicates the time the current is shut off and the spark occurs. Turning once again to FIGURE 7, there is graphically illustrated an oscilloscope trace showing the total voltage across the primary windings over time (in microseconds) starting with solid state switch being turned on 700 and ending with solid state switch being turned off 701 and the occurrence of the spark. Referring to FIGURE 5, there is graphically illustrated the number of sparks per ignition event 500 as a function of RPM compared with existing capacitor discharge ignition systems 501.

[039] In summary, the high speed capacitor discharge ignition system of the present invention has several advantageous or features not present in conventional ignition systems. The high speed capacitor discharge ignition system may be produced at low cost, especially the computer controlled ignition system for mass produced vehicles which utilizes only two solid state devices— one solid state switch and one gate driver. The high speed capacitor discharge ignition system has low average current drain, typically approximately one (1) amp for six (6) sparks per ignition event at 9000 RPM and fourteen (14) volts from the vehicle electrical system. The high speed capacitor discharge ignition system can function down to eight (8) volts and down to zero (0) engine RPM and generates very little heat. In one specific embodiment of the invention, the solid state switch temperature is 120 F at 9000 RPM with six (6) sparks per ignition event and without the need or use of a heat sink.

[040] The high speed capacitor discharge ignition system of embodiments of the invention utilizes two low voltage (25 volts) large capacitance (10,000 uF) electrolytic capacitors to supply a hundred amps for brief periods of time (30 uSec) and to store energy during starting. The high speed capacitor discharge ignition system of embodiments of the invention utilizes a short, low inductance, direct connection of the capacitor to the low inductance primary windings (typically the capacitors are mounted within 0.2 inch of the primary windings) on the printed circuit board (see FIG.3).

[040] The example illustrated in FIGURE 2 utilizes direct control by vehicle computer software for controlling the spark timing and duration of the charging current. Typically the computer software is used to generate a 30 uSec wide pulse for each spark. In contrast to prior art Kettering systems, the high speed capacitor discharge ignition system of the present invention utilizes a low primary winding coil inductance, very rapid buildup in magnetic flux to allow multiple sparks at high engine RPM, and high primary coil current (on the order of a hundred amps for several microseconds (and typically at least about 20 amps); in contrast with typical transistorized Kettering system currents that are typically only several amps for 2 milliseconds or longer).

[041] Embodiments of the invention could utilize various other different components in various other different configurations and still fall within the scope of the present invention as long as the embodiments provided the desired high spark rate. Certain terminology is used in the following description for convenience only and is not limiting. The words "lower", "bottom", "upper", and "top" designate directions )in the drawings to which reference is made. The words "inwardly", "outwardly", "upwardly" and "downwardly" refer to directions toward and away from, respectively, the geometric center of the device, and designated parts thereof, in accordance with the present disclosure. Unless specifically set forth herein, the terms "a,"an" and "the" are not limited to one element, but instead should be read as meaning "at least one". The terminology includes the words noted above, derivatives thereof and words of similar import.

[042] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[043] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.