Ignition system (original) (raw)
June 20, 1967 4. A. HAWTHORNE 3,327,165
IGNITION SYSTEM Filed Oct. 26, 1964 I INVENTOK for? fl. fi awiizmwe United States Patent 3,327,165 IGNITION SYSTEM John A. Hawthorne, 92 Alton Road, Stamford, Conn. 06906 Filed Oct. 26, 1964, Ser. No. 496,286 2 Claims. (Cl. 315223) The present invention relates to ignition systems for internal combustion engines. More particularly, it relates to improvements in the Kettering or inductive ignition system used exclusively in present-day automobiles. The Kettering system has enjoyed virtually exclusive use in automobiles since 1914. The basic components of this system are a battery, a transformer coil, a cam-driven mechanical switch (distributor points), an attendant capacitor and a current limiting ballast resistor. The secondary winding of the transformer coil develops the requisite high voltage to fire the spark plugs of the internal combustion engine.
Practical efforts to improve or supplant this system have failed, and it has remained virtually unchanged through the years. However, the present trend toward higher performance automobile engines threatens to render this tried and true system obsolete. The principal limitation of the Kettering system is, as typically applied, the inability to develop adequate levels of spark plug gap energy without sacrificing longevity of the ignition points or the transformer coil. The inherent inefiiciency of the system is particularly apparent at higher engine speeds.
Recent efforts to develop an ignition system overcoming the principal limitations of the Kettering system have resulted in exotic electronic ignition systems. Such ignition systems have proven to be quite complex and expensive. Moreover, they are of questionable reliability and virtually unserviceable by anyone other than a highly skilled electronics technician. Since these electronic ignition systems are typically designed to replace conventional ignition system components, considerable expense is required for their installation in existing automobiles.
It is accordingly an object of my invention to provide an improved automobile ignition system of the inductive type.
An additional object is to provide an ignition system of the above character which is capable of developing increased spark gap energy, and hence, higher gap temperature, at all engine speeds. This is accomplished notwithstanding conditions normally causing spark gap fouling. A related object is to provide an ignition system of the above character which will substantially inhibit the fouling of spark plugs.
A still further object is to provide an ignition system of the above character which is more efiicient, and thus capable of providing improved engine performance and operating economy.
A still further object is to provide an ignition system of the above character which may be constructed by readily modifying conventional automobile ignition systems.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:
The sole figure of the drawing is a detailed schematic circuit diagram of an embodiment of my invention.
Broadly stated, my invention is directed to an improved ignition system for internal combustion engines comprising the incorporation in a conventional inductive ignition system of added circuit components functioning to decrease the effective operating impedance of the ignition primary circuit to an absolute minimum. This being achieved, energy losses are substantially reduced and the increased energy at the spark plug gaps produces a hotter, fatter spark. To this end, a capacitor is connected across the battery source to provide a low impedance return path at all engine speeds for the fiyback energy developed in the induction coil. Moreover, a threshold discharge device, connected in the primary circuit of the induction coil, conducts wit-h minimum D.C. resistance to enhance the development of this flyback energy.
Turning to the drawing, a
storage battery
10 is shown with its negative side grounded to the automobile chassis and its positive side connected to an
ignition switch
12. It will be understood that, in certain automobile models, this battery polarity is the reverse of that shown. The
ignition switch
12 connects one side of the
battery
10 through a
ballast resistor
14 to a
Winding
16 constituting the primary winding of an induction coil, generally indicated at 18. A
secondary winding
20 of the induction coil .18, magnetically coupled to the
primary winding
16, is connected in common with the primary winding at
terminal
22. The other side of the
secondary winding
20 is connected in conventional fashion, through a distributor 24 sequentially to the individual spark plugs, one being shown at 26.
Terminal
22 is periodically grounded through distributor breaker points, indicated at 28. A
condenser
30 is normally connected across the
breaker points
28 to absorb reflected primary energy and to suppress breaker contact arcing.
The ignition circuit thus far described conforms to the conventional inductive ignition circuit employed in present day automobiles. In operation, with the
ignition switch
12 and
breaker points
28 closed, current flows through the primary 'winding 16 of the
induction coil
18. This current develops a magnetic field about both induction coil windings. When the breaker points 28 open, current flow is interrupted and this established magnetic field suddenly collapses. The collapsing magnetic field induces a high voltage pulse in the
secondary winding
20 for distribution to the
spark plugs
26. Reversed current flow, termed fiyback pulse, resulting tfIOlTl this collapsing magnetic field, is developed in the
primary winding
16. A portion of the energy associated with this flyback pulse is absorbed by the primary winding in discharging it. However, a significant portion of this energy is dissipated in the
ballast resistor
14 and thus cannot aid the development of the high voltage pulse in the
secondary Winding
20. Since, in the conventional system, the resistance value of the
ballast resistor
14 is generally chosen to be substantially equal to the cold resistance value of the
primary winding
16 of the
induction coil
18, it will be seen that the energy losses of this system are indeed substantial.
According to my invention, a very
large capacitor
32, typically 5000 microfarads, or larger, is connected from the junction between the
ballast resistor
14 and the
primary winding
16 to ground. This capacitor provides a very low impedance return path to ground for the fiyback current pulse. Because of its large capacitance value,
capacitor
32 provides a genuinely low impedance path even at engine idling speeds when the
breaker points
28 are opening and closing at a relatively slow rate. This would effectively correspond to a low A.C. frequency. At faster speeds, this effective A.C. frequency increases and the impedance of the return path further decreases. Consequently, the
ballast resistor
14 is elfectively bypassed for all engine speeds, and the normal dissipation of fiyback energy in this resistive element is virtually eliminated. Substantially increased fiyback energy is absorbed by the
induction coil
18 during the spark interval and the energy output of the
secondary winding
20 is effectively doubled.
An additional structural feature of my invention resides in the inclusion of a
threshold discharge device
34 connected from
terminal
22 to ground. In order to derive maximum benefit, the
device
34 should have the characteristics of high current capabilities and a negligible D.C. resistance. It should fire when the voltage across it exceeds approximately 50 volts and should continue to conduct heavily until the voltage drops to approximately 18 to 20 volts. The
device
34 should be capable of absorbing, on a pulsed operational basis, upwards of 30 watts of power over a 10 to 20% duty cycle. This threshold discharge device may take the form of a commercially available NE42 gaseous discharge lamp or its equivalent. However, other forms of threshold discharge devices are contemplated.
When the magnetic field associated with the
primary winding
16 collapses causing the fiyback current pulse, the voltage at
terminal
22 swings positive rapidly. When the voltage at
terminal
22 reaches approximately 50 volts, the
device
34 fires to provide a low impedance path from ground for the fiyback current pulse. Thus the
device
34 in combination with the
large capacitor
32 provides low impedance circuit path continuity for the fiyback current pulse. The
device
34 will sustain fiyback current pulses of higher magnitude and with faster rise time, thus inducing higher spark gap voltages in the secondary winding 20 than can be attained in the conventional ignition system. Since, with my invention, the spark gap voltage is substantially increased, a hotter, fatter spark is achieved.
The voltage at
terminal
22 falls rapidly as the fiyback energy is absorbed by the
device
34 until at approximately 20 volts it extinguishes and ceases to conduct. Then the breaker points 28 will close and the ignition circuit will gradually assume steady state conditions awaiting the next opening of the breaker points.
It will be appreciated that the development of a hotter, fatter spark at the spark plug gaps throughout the engine speed range provides manifold benefits. The engine may be more readily started under adverse conditions, particularly in cold weather. Adequate spark will be developed notwithstanding the presence of a low shunting resistance existing in fouled spark plugs. Moreover the development of fouled spark plug gaps will be greatly impeded. Improved engine performance and operating economy are also achieved. With the
discharge device
34 connected across the breaker points 28, excessive voltages cannot be developed across the points. Point life is thus materially prolonged. Since very little energy is absorbed by the
capacitor
30 as compared to the
device
34, it may be omitted with negligible effect on the operation of my invention.
it will be further appreciated that some advantage in improved ignition system operation is derived from the use of the
capacitor
32 and the
device
34 separately rather than in combination. Since the
capacitor
32 and the
device
34 function individually at opposite sides of the primary winding to provide a low impedance path to ground, their individual incorporation in an automobile ignition system provides measurable improvement in operation.
It will be further appreciated that an additional important feature resides in the fact that the
capacitor
32 and the
threshold discharge device
34 can be readily incorporated in existing conventional automobile ignition systems by making a few simple circuit connections. No rewiring is required.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
Having described my invention, what I claim as new and desire to secure by Letters Patent is:
1. An attachment for improving the operation of a conventional ignition system for automotive internal combus tion engines wherein the ignition system includes primary and secondary induction coil windings, the secondary winding connected through a distributor to the various spark plugs, a battery having a first terminal grounded and a second terminal connected through a ballast resistor to a first terminal of the primary winding and breaker contacts connected between a second terminal of the primary winding and ground and periodically operating in timed relationship with the operating speed of the engine to interrupt current flow in the primary winding whereby to develop a fiyback current pulse effective to induce a high spark gap voltage in the secondary winding, the attachment including, in combination:
A. a capacitor for connection from the first terminal of the primary winding to ground, said capacitor (1) having a capacitance value in excess of 4000 microfarads so as to provide a low A.C. impedance path for the fiyback current pulse at all engine speeds,
(a) said low A.C. impedance path shunting the battery and ballast resistor; and B. a threshold device for connection across the breaker contacts, said device becoming conductive (l) at a predetermined elevated threshold voltage level occuring during the opening of the breaker points to provide, in conjunction with said capacitor, low A.C. impedance circuit continuity for the primary winding.
2. The attachment defined in claim 1 wherein B(2). said threshold device is a gaseous discharge lamp operating to conduct heavily when the voltage across it exceeds a predetermined threshold value in excess of 50 volts and continues to so conduct until the voltage across it falls below a predetermined minimum value less than 20 volts.
References Cited UNITED STATES PATENTS 2,032,743 3/1936 Evans 31711 2,353,527 7/1944 Touceda 315 209 2,963,624 12/1960 Meyer 3 15-209 JOHN W. HUCKERT, Primary Examiner.
D. O. KRAFT, A. M. LESNIAK, Assistant Examiners.