Internal-combustion engines – High tension ignition system – Using capacitive storage and discharge for spark energy
Reexamination Certificate
2000-10-06
2003-07-01
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
High tension ignition system
Using capacitive storage and discharge for spark energy
C123S620000
Reexamination Certificate
active
06584965
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to capacitive discharge (CD) ignition systems for internal combustion (IC) engines, and more particularly to improved CD ignitions with much higher efficiencies and much higher spark firing rates than achievable before for a given level and type of delivered spark energy. The invention is especially useful for the very efficient and rapid delivery of high energy spark discharges of the flow-resistant type which are preferred in advanced high efficiency IC engines with high in-cylinder airflows. The invention applies to both single coil distributor type ignition systems as well as to more modern one-coil-per-plug distributorless type ignition. In the case of the distributor version, the high efficiency and high spark firing rate make the system especially useful in high speed eight cylinder (V-8) engines operating at speeds up to and above 9,000 RPM and providing the more useful flow resistant, single polarity, triangular, arc discharge mode type spark with minimum heat dissipation. In the case of one-coil-per-plug ignition, the high efficiency of the system allows for delivery of more of the limited available energy associated with smaller ignition coils and/or lower electrical energy generating systems, as in a flying magnet system found in small engine applications. The invention relies, in part, on the use of ignition coils with improved side-by-side windings and with improved silicon-iron laminated cores for achieving the higher efficiencies, and in part on the use of IGBT and FET switches and high efficiency diodes for controlling and shaping the discharge of the energy storage capacitors (also referred to hereinafter as “discharge capacitors”) as well as the primary and secondary winding currents to insure good operation throughout a wide range of speeds, from cranking to very high speeds or high firing rates.
BACKGROUND OF THE INVENTION AND PRIOR ART
Current capacitive discharge (CD) ignition systems are very inefficient, with typically 15% to 25% efficiency, and deliver typically only 20 to 30 millijoules (mJ) of spark energy per single spark pulse (into an industry standard 800 volt Zener load). On the other hand, evidence points to a requirement of over 100 mJ of spark energy for best engine performance of a standard automobile engine. In addition, CD ignition coils are typically wound with concentric primary and secondary windings to give relatively low leakage inductance for a given number of primary wire turns, which contributes to the low efficiency of the ignition system, versus the three times and higher efficiency of 60% to 70% achieved in the present invention.
Current CD systems also typically use silicon control rectifiers (SCRs) which discharge all the capacitively stored energy upon ignition firing. This results in slower recharging of the discharge capacitors to a potentially lower energy and peak voltage, as well as poorer use of the power source. This can be a particular problem when lower energy is available for delivery to the capacitor, as in the case of engines running at very high speeds (less charging time) or flying magnet systems under engine cranking conditions. On the other hand, the present system uses switches that can be turned off, preferably insulated gate bipolar transistors (IGBTs), and a discharge circuit design and control which allows for the capacitor charging during ignition spark firing.
Modern ignition coils use laminations which are butt-welded and have mounting holes punched in the laminations. Such designs reduce the coil discharge efficiency and increase coil heat dissipation. Moreover, they use relatively thick laminations, i.e. 14 mil (thousands of an inch) or thicker, which results in lower coil efficiency when applied to the present, more optimal, preferred side-by-side winding coil topology which is more sensitive to certain aspects of lamination design, as was discovered, requiring alternative designs for the laminations, geometry, and mounting.
In the present application, segmented secondary coil windings are provided to limit coil output capacitance Cs (to help insure voltage doubling), as well as inductive suppressor wire to reduce electromagnetic interference (EMI), where applicable. However, to improve the spark's ignitability, capacitive spark plug boots, or improved spark plugs with built-in capacitance, are preferred for the present application.
In the case of high speed engines with single coil distributor ignitions, high circuit efficiency along with use of the preferred triangular, versus sinusoidal, primary and secondary winding spark current distribution leads to problems at high engine speeds when a coil may be fired well above 200 Hertz (Hz). This problem occurs because of the imperfect coupling between the primary and secondary windings (k<1), resulting in a residual primary current after the secondary current has dropped to zero. The residual primary current then decays at a much lower rate dictated by the ignition coil primary circuit losses alone so that at high coil firing rates there may be a non-zero primary current when the ignition refires, reducing the secondary spark current at high speeds. While this problem may be largely off-set by designing the discharge circuit for the sinusoidal current distribution, this has several drawbacks, including and not limited to not allowing charging of the discharge capacitor during spark firing. In the present invention is disclosed improved and optimized methods of handling this problem.
In the automotive case where battery power is used (12, 24, or future 42 volt), the power converters which are used to step-up the voltage to the typical 200 to 600 volts are generally inefficient and electrically noisy, with efficiencies between 35% and 70%, and up to 85% in practice in my U.S. Pat. No. 5,558,071. In the present application is disclosed improvements to increase power converter efficiency to between 90% and 94%, important in minimizing heat dissipation in the high temperature engine environment, especially where small, lightweight packaging of the parts is preferred.
By careful and innovative design of the entire system, from the power stage, to the discharge circuit, to the ignition coil, to the spark plug wires and spark plug itself, one can achieve a very high efficiency and a high spark discharge energy. In the case of a single coil distributor ignition system one can have a more optimized system for very high speeds with much higher energy density (spark energy per unit weight) with minimum heat dissipation, and in the case of one-coil-per-plug ignition systems one can have very small, low cost parts, producing high spark energy very efficiently.
SUMMARY OF THE INVENTION
The system of the present invention is applicable to single coil distributor and one-coil-per-plug distributorless CD ignition systems. The system uses controllable coil primary winding circuit main switch means Si (S for distributor systems) which can be turned-off prior to the discharge of the energy storage capacitor, and diode means Di (D for distributor systems) shunting the coil primary winding of high efficiency coils with side-by-side windings producing an essentially triangular distribution of primary current Ip and secondary current Is. The system is designed to provide the highest efficiency as a complete system as well as in terms of individual parts and sub-systems. It delivers maximum spark energy for a given stored energy, produces low component and system heat dissipation, and provides the most rapid and efficient recharging of the discharge capacitors, especially at very high switching speeds as occurs in single coil distributor ignition systems found in high speed multi-cylinder engines.
In a preferred embodiment, the discharge capacitor is not fully discharged by the main discharge switch S or Si, which is preferably an IGBT, which operates to leave a significant voltage on the capacitor, e.g. 20% to 40% of the initial voltage, or approximately 130 volts for the high firing rate distributor ignition case of prefe
Castro Arnold
Cohen Jerry
Perkins Smith & Cohen
Yuen Henry C.
LandOfFree
High efficiency high energy firing rate CD ignition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High efficiency high energy firing rate CD ignition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High efficiency high energy firing rate CD ignition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3022811