Ignition system with power boosting arrangement

An ignition system for internal combustion engines employing two coordinated power sources which, together, provide a spark of much increased intensity and with extended duration. The first of the coordinated power sources is generally similar to the conventional ignition system employing an ignition coil with a primary and secondary winding, the secondary winding generating a high voltage impulse of very high voltage and low current value and of short duration. The second power source is a storage capacitor which is connected to a direct current power supply which, through a limiting resistor, charges the capacitor to a voltage which is too low to initiate a spark, but high enough to sustain an arc of a controlled high current value for increased duration, once a preliminary spark has been generated across the spark gap at the moment an energizing current in the primary winding of the ignition coil is interrupted. The two coordinated power sources may be connected to the spark plug in parallel connection through rectifiers, which provide separation between the power sources, or the two power sources may be connected with the spark plug in series connection again using rectifiers to separate them. Multiple sequentially firing spark plugs as used in engines with multiple cylinders may be driven by the present invention by incorporating a distributor which sequentially distributes either the preliminary spark or the combined sparking energy to the spark plugs.

BACKGROUND OF THE INVENTION 
Internal combustion engines with high voltage electrical ignition are 
usually provided with an ignition coil which provides the high voltage 
pulses that are needed to produce an electrical spark across the spark gap 
of a spark plug which, in turn, ignites the compressed fuel-air mixture in 
the combustion chamber of each cylinder at the start of the power cycle. 
There are essentially two (2) types of generators for such high voltage 
pulses, namely the conventional automotive ignition coil which has a 
primary circuit energized by the engine's low voltage primary power. 
Another generator for such high voltage pulses is the so-called magneto, 
which has a rotating armature revolving in a magnetic field, driven by the 
engine, and which is energized directly from the engine's camshaft or 
driveshaft. These types of ignition systems have been used successfully 
for many years, and are described in text books on automotive engineering. 
One such book is Basic Ignition and Electrical Systems by R. E. Petersen, 
published by Petersen Publishing Co. and has Library of Congress Catalog 
Card Number 73-79968. 
In those conventional systems using ignition coils or magnetos, the high 
voltage pulses are generated in a high impedance secondary winding 
consisting of many turns of fine wire having a resistance of 5 to 10 kilo 
ohms which produces a high voltage pulse of typically 10 to 15 thousand 
volts at the instant a current flowing in a primary winding magnetically 
coupled with the secondary winding is abruptly interrupted. The 
interruption of the primary current is often done by a set of mechanical 
contact points, the so-called breaker points which are opened by 
mechanical cams at precisely timed instants during the rotation of the 
engine. During recent years, many so-called electronic ignition systems 
have been developed where the interruption of the primary current is 
performed by solid state circuit components in order to attain longer life 
and improved engine performance. 
In recent years, there has been increased demand for improvement in engine 
performance, in regard to fuel efficiency and in regard to reduction of 
unwanted air-polluting exhaust gas emissions. 
In order to attain such improved engine performance, it is desirable to 
operate engines at a lower fuel to air ratio, a so-called leaner mixture. 
Ideally, an engine should be operated at a so-called stoichiometric ratio 
of fuel to air, at which ratio total combustion of the fuel will be 
attained. Such a ratio, however, is quite lean and is more difficult to 
ignite and has a decreased flame front velocity compared with the richer 
conventional fuel-air mixture. 
For the above reasons, engine designers have aimed at developing ignition 
systems that generate more powerful sparks of longer duration than the 
spark produced by the conventional secondary winding of the ignition coil 
which, due to its high resistance and high inductance, can only produce a 
spark of limited intensity and duration. The extended duration of the 
spark is desirable because combustion chambers are often designed such 
that a strong swirling motion is imparted to the fuel-air mixture in the 
combustion chamber, which provides for a more extended contact with the 
sustained arc of the spark gap. 
Many inventors have worked at devising ignition systems that provide such 
improved spark characteristics as described above. Some of those are 
listed in the references. One reference in particular, is U.S. Pat. No. 
3,919,993, issued Nov. 18, 1975 to J. G. Neuman. That referenced patent 
describes an ignition system where the spark is generated and sustained by 
means of two generally parallel connected coordinated power sources such 
that one of the power sources is very high voltage secondary winding of an 
ignition coil of generally conventional nature which produces an initial 
spark across the spark gap at a voltage of sufficient value to safely 
bridge to spark gap but of a relatively low intensity coordinated with the 
spark from another ignition coil having a secondary winding which is 
constructed so as to generate a voltage inpulse of much lower voltae but 
of a much higher current value. The impulse from the latter ignition coil 
is timed by appropriate means to happen at a time slightly later than the 
first initial impulse in a precisely controlled timing sequence. 
The present invention discloses an ignition system constructed so as to 
provide a spark of much increased intensity and increased duration, and 
such that both the intensity and the duration of the spark can be 
controlled within wide limits by judicial choice of the controlling 
components, using two coordinated power sources such that one power source 
is the secondary winding of a generally conventional ignition coil which 
produces an initial impulse of voltage high enough to bridge the spark gap 
with a spark which is generally of low intensity and of short duration 
coordinated with another power source which will sustain the spark in the 
form of an electrical arc of high intensity as determined by current 
limiting circuit elements, and of a duration which is determined by the 
product of the resistance of the current limiting circuit element and the 
capacitance of the storage capacitor. Means are provided as required, to 
ensure that the arc is extinguished after the elapse of such time that it 
is no longer needed to sustain the combustion in the combustion chamber. 
The present invention shows how the two coordinated power sources described 
above, may be either parallel or series connected. 
It is, therefore, a major object of the present invention to provide an 
improved ignition system for internal combustion engines. 
It is an additional object of the present invention to provide an improved 
ignition system for internal combustion engines which combines a high 
voltage inductively generated initial impulse of short duration and low 
current value with a capacitive power source of relatively low voltage, 
but high current value such as to produce an electric arc of high 
intensity and extended duration. 
It is an additional object of the present invention to provide an improved 
ignition system for internal combustion engines which combines a high 
voltage inductively generated initial impulse of short duration and low 
current value with a capacitive power source of relatively low voltage, 
but of a high current value such that the two power sources are 
coordinated in generally parallel connection utilizing high voltage 
rectifiers such that the high current from the capacitive power souce 
bypasses the spark distributor. 
It is still another object of the present invention to provide an improved 
ignition system for internal combustion engines which combines a high 
voltage inductively generated initial impulse of short duration and low 
current value with a capacitive power source of relatively low voltage, 
but of a high current value such that the two power sources are combined 
in generally series connection with at least one high voltage rectifier 
separating the two power sources. 
It is a further object of the present invention to provide an improved 
ignition system that is generally of simple construction and which 
provides a spark of such intensity that fouling conditions around the 
spark gap electrodes will tend to be burned away and in this way 
contribute to a more reliable ignition system.

The reference numerals shown on all the drawings correspond to each other, 
so that in different embodiments, the same numeral always represents the 
same element. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 5a which shows, in simplified form, the basic elements of 
the ignition system of the present invention, and more particularly, the 
embodiment which employs two coordinated, generally parallel, connected 
power sources. The first power source is shown generally at 7, which shows 
two windings of an ignition coil having a primary low resistance winding 
8, consisting of relatively few turns of heavy wire and a secondary high 
voltage winding 9, consisting of many turns of thin wire wound 
concentrically on a magnetic core, and where the two windings have a turns 
ratio such that a high voltage impulse of typically 10-15 thousand volts 
is generated between the terminals of that winding when an energizing 
current in the primary winding is abruptly interrupted. Of the two 
terminals of the high voltage winding, one terminal, the low voltage 
terminal, is shown grounded in this simplified diagram, but as shown in 
other diagrams, this terminal is not always grounded, but is always at a 
lower potential than the high voltage terminal, which, at the instant of 
the interruption of the current in the primary winding, reaches a high 
voltage potential which strikes a spark across the spark gap of the spark 
plug 1. This spark striking potential which is of negative polarity, is 
connected to the spark plug through a rectifier 6. Negative potential is 
used most commonly in modern ignition systems, although the polarity 
whether negative or positive is immaterial for the present invention. 
Since winding 9 has high resistance typically, 5-10 thousand ohms and high 
selfinductance, the current in the resulting spark is of a low value, 
typically a few milliamperes, and the duration of the spark is typically a 
small fraction of a millisecond. Thus, the initial spark is not well 
suited for igniting a lean fuel-air mixture due to its low intensity and 
short duration. However, the initial spark provides a path of conductive 
ionized gas molecules across the spark gap. This conductive path, as soon 
as it is established, provides also a path of current flow for the second 
power source consisting of storage capacitor 4, which is charged to a 
potential, typically 2-4 thousand volts, from direct current power supply 
3 through first limiting resistor 15. As a result an arc of high 
intensity, sustained by the energy stored in the capacitor is established 
immediately following the initial spark. The current in the arc is limited 
by second limiting resistor 17, and decays exponentially as the capacitor 
discharges, until the current value is too low to sustain the arc. 
The voltage generated by the power supply 3 is of lower potential than that 
required to initiate a spark, but high enough to sustain the arc at a high 
current value for a predetermined length of time. The electrical 
parameters of the arc, its current value and duration and their 
relationship to the circuit elements will be shown later in this 
description. 
As described above, the two power sources, namely the high voltage source, 
winding 9, and the high current source, the storage capacitor 4, are in 
parallel connection through the two rectifiers 6 and 5, which serve to 
provide separation between them. Rectifier 5 prevents the current for the 
initial spark from high resistance winding 9 from being dissipated in the 
low impedance circuit consisting of resistor 17 and storage capacitor 4. 
Similarly, rectifier 6 prevents the storage capacitor 4 from being 
discharged through winding 9 during the intervals between sparks. 
During the discharge of the capacitor 4, the voltage across the capacitor 
terminals decreases at an exponential rate as a function of the elapsed 
time, the value of the capacitor and the value of second limiting resistor 
17. The product of the resistor value in ohms and the capacitor value in 
Farads is called the time constant of the discharge circuit which has the 
dimension of seconds. After the elapse of a time which is equal to one 
time constant, the current and voltage will have decayed to a value of 
.epsilon..sup.-1 =0.368 of the original value. The voltage and current 
will decay in accordance with the function: 
EQU e.sub.c (t)=E/{.epsilon..sup.(t/R17C) }, 
where 
e.sub.c=voltage across capacitor terminal as a function of t 
t=elapsed time from initial spark in seconds 
E=the initial voltage stored on the capacitor, which also equals the open 
circuit voltage of power supply 3 
.epsilon.=base of the natural logarithm=2.718 
R17=the resistance of second limiting resistor 17 in ohms 
c=capacitance of storage capacitor 4 in farads. 
While the capacitor normally discharges rapidly while expending its stored 
energy partly in the arc and partly in the resistances in the circuit, it 
is also being charged by the power supply 3 through first limiting 
resistor 15. The rate of charging is exponential as expressed by the 
function: 
EQU e.sub.c (t)=E(1-(1/.epsilon.).sup.(t/R15C).sub.) 
In an experimental ignition system which was found to work well, the 
following values were used: R15, 1000 ohms, R17, 50 ohms, capacitor 4,0.1 
micro farad; power supply 3,300 volts. 
The rectifiers 5 and 6 were each constructed from four series connected 
Motorola type MR250-5 rectifier diodes. The direct current power supply 3 
may be of the dc-dc converter type obtaining its primary power from the 
engine's low voltage power system. Such converters are well known, and 
widely used for many applications. 
Two additional circuit elements, 18 and 19, may be included with the 
system. Circuit element 18 is a current disconnect element, which is 
introduced in the current loop for the high current source. In one 
preferred embodiment of the present invention, this element is a 
mechanical switch with heavy duty metallic contacts and operated in timed 
relationship with the engine by rotating a cam, such that the contacts are 
opened at some predetermined time or angle of rotation after the initial 
spark has been struck, and such that the discharge current from storage 
capacitor 4 is interrupted, and the sustained arc is extinguished at a 
time earlier than the time at which the arc would have been extinguished, 
due to the gradual discharge of capacitor 4. At the further rotation of 
the cam, the contacts of 18 will again be closed at a time immediately 
prior to the next initial spark. 
The current disconnect element 18 may, at the option of the designer, serve 
to shorten the duration of the sustained arc, and further, to ensure that 
the storage capacitor 4 is fully recharged at the beginning of the next 
initial spark in case spark plug fouling should have created a current 
leakage across the spark gap which would prevent capacitor 4 from being 
recharged to the full potential of power supply 3. In this manner, circuit 
element 18 will serve to increase the ignition reliability. 
It should be understood that the current disconnect device 18 need not be 
of mechanical construction, but may be designed using solid state type 
current controlling elements and that the rotating cam drive may be 
replaced with appropriate electronic timing circuit elements that operate 
to disconnect the current, sustaining the arc after a predetermined lapse 
of time after the initial spark, and such that the current source is again 
connected at the time the initial spark is struck. 
Circuit element 19 is an inductor, disposed in the current loop in series 
with second limiting resistor 17. This inductor, when included in the 
circuit, will operate to slow down the otherwise very rapid increase of 
current in the current loop. Further, the inductor will coact with the 
capacitor 4, so that they, together, operate as a series resonant circuit 
that, depending upon the values of the inductor, the capacitor and 
limiting resistor 17, will create a current pulse generally of the form of 
a damped single sinusoidal halfwave of current in the loop. The duration 
of the halfwave will be 
##EQU1## 
where L=selfinductance of the inductor 19 in henrys 
C=capacitance of capacitor 4 in farads. 
If the series resonant circuit is less than critically damped, the 
rectifier 5 will prevent the halfwave of current from continuing into the 
second halfwave, and in this way, at the end of the halfwave, the arc will 
be extinguished. The presence of the inductor 19 will provide a more 
efficient transfer of energy from the storage capacitor to the arc, since 
less energy will be lost in the resistor 17. 
FIG. 5b is a simplified drawing of another preferred embodiment of the 
present invention. It contains the same elements as shown in FIG. 5a, but 
in this case, the two coordinated power sources are combined in series 
connection. The method of operation is similar. Upon interruption of an 
energizing current in winding 8 of ignition coil 7, secondary winding 9 
generates a pluse of high voltage, but low current which in turn creates 
an initial spark of low intensity and short duration across the spark gap 
of spark plug 1. The initial spark creates a conducting path of ionized 
gas across the spark gap. This path enables the high current source 
consisting of storage capacitor 4, which is charged to a voltage which is 
too low to initiate a spark, but high enough to generate and sustain an 
arc of high intensity and extended duration in the path established by the 
initial spark. 
A rectifier 6 is connected across the terminals of high voltage winding 9, 
such that the high current, once the arc is established, may bypass the 
high impedance of winding 9. The storage capacitor 4 is charged by a 
direct current power supply 3 through first limiting resistor 15, and the 
capacitor discharges through second limiting resistor 17. The two series 
connected power sources are connected in mutually aiding connection and 
such that a negative potential is applied to the spark plug. 
The two optional circuit elements, current disconnect element 18 and 
resonating inductor 19, serve the same functions as they do in FIG. 5a, 
and to avoid prolixity, shall not be explained again. 
FIG. 6a, b and c, which applies to both FIG. 5a and 5b, shows in graphic 
form, as a function of time, the voltage and current across the spark gap. 
FIG. 6a shows voltage accross the spark gap. Before time t.sub.1, the dc 
voltage is that of the storage capacitor shown on the vertical unit as 
V.sub.1. At time t.sub.1 the high voltage creating the initial spark 
commences and reaches a peak voltage V.sub.2, at which time the initial 
spark is created. At the time t.sub.2 the high current power source starts 
the sustained arc. Between t.sub.2 and t.sub.3 the storage capacitor 
discharges its energy, and the voltage decays to the voltage V.sub.3, at 
which point the voltage is too low to sustain the arc, which is then 
extinguished. The corresponding current-time relationships are shown in 
FIG. 6b. Before t.sub.1 no current flows. Between times t.sub.1 and 
t.sub.2, the current rises to the relatively low value of i.sub.1 and 
rises sharply to the high value i.sub.2 at time t.sub.2, when the high 
current power source starts to feed the sustained arc. The current decays 
exponentially between times t.sub.2 and t.sub.3, and drops to zero at time 
t.sub.3. 
The action of the current disconnect element 18, if included with the 
circuit, may take place at times t.sub.1 and t.sub.7. The element 18 
closes the circuit at or immediately prior to time t.sub.1, such that the 
voltage would be at zero value prior to t.sub.1, and it would open the 
circuit at t.sub.7 at which time both the voltage on FIG. 6a and the 
current on FIG. 6b would drop to zero. 
FIG. 6c shows the current through the spark gap with the resonating 
inductor 19 included in the circuit. The circuit is less than critically 
damped, and a half-wave is found between the times t.sub.2 and t.sub.7. 
Having above described, in abbreviated form, the method of operation of the 
present invention in two basic preferred embodiments, I shall proceed to 
describe in greater detail various preferred embodiments based on the 
above two basic embodiments. 
FIG. 1 shows the present invention in accordance with the first preferred 
embodiment described above in FIG. 5a, expanded to include multiple 
combustion chambers with a multiple cylinder engine, each combustion 
chamber equipped with at least one spark plug. 
The ignition coil 7 has a primary winding 8 and a secondary winding 9. The 
primary winding 8 is connected to an energizing circuit consisting of low 
voltage power source 12, which may be the engine's battery or any suitable 
power source and an interrupter contact 10. Interrupter 10 is connected to 
the engine's drive shaft through suitable mechanical means so that 10 is 
opened in a fixed timed relationship with the engine rotation at the 
instant a spark is to be struck. Capacitor 11 serves to resonate with the 
self-inductance of primary winding 8, so that a high voltage is generated 
in winding 9 when the interrupter contacts 10 are opened. The high voltage 
winding 9 is connected to a plurality of sets of spark plugs 1a, 1a' 
through 1d and 1d', through resistor 14, which represents the combined 
resistance of winding 9 and the lumped and distributed resistances of the 
connection to the distributor 13. Distributor 13 consists of a common 
rotating contact driven in a fixed rotational relationship with the 
engine's drive shaft, such that each successive high voltage impulse is 
connected in sequence to each set of spark plugs at the time a spark is to 
be struck in each spark plug. 
All the circuit elements combining to generate the initial spark and are 
described above are well known and described in the art, and may take 
various forms while all essentially performing the same function. For the 
purpose of the present invention, a rectifier 6 has been added in the 
connection from high voltage winding 9 to distributor 13. Rectifier 6 is a 
high voltage rectifier described above in connection with FIG. 5a. This 
rectifier prevents the charge on the storage capacitors 4 and 4' from 
being dissipated through the ignition coil 7 between successive sparks. 
FIG. 1 illustrates an engine with four (4) cylinders. For the purpose of 
the present invention, the number of cylinders and the number of spark 
plugs associated with each cylinder is immaterial. In the specific case 
where more than one spark plug is used with each cylinder, a dividing 
network consisting of resistors 16a through 16d and resistors 16a' through 
16d' are required to ensure that both spark plugs in each set of spark 
plugs fire simultaneously at the time an initial spark is to be struck. If 
no such resistors were provided, a minute difference between spark gaps of 
a set of spark plugs could cause only one of the spark plugs to fire. 
Each spark plug is connected through rectifiers 5a through 5d and 5a' to 
5d' to storage capacitors 4 and 4', through limiting resistors 17 and 17'. 
Those storage capacitors are connected to power supply 3 through first 
limiting resistors 15 and 15'. The above circuit elements 4, 4', 15, 15', 
17, 17' cooperate in a manner similar to that described under FIG. 5a as 
the high current source, except their numbers are increased in order to 
accommodate a multiple cylinder engine and where each cylinder may be 
equipped optionally with more than one spark plug. The high voltage power 
source consisting of elements 6, 7, 10, 11, 12, 13 and 14 generates 
sequentially in each set of spark plugs an inital spark. The high current 
power source subsequently generates a high current sustained arc of high 
intensity and extended duration in the corresponding spark plugs. 
FIG. 2 shows the present invention in accordance with the second preferred 
embodiment described above under FIG. 5b, but expanded to a multicylinder 
engine with spark plugs 1a through 1d. The second preferred embodiment of 
the present invention employs two coordinated power sources combined in 
series connection. As in FIG. 1, elements 7, 8, 9, 10, 11, 12 and 14 in 
combination from the high voltage power source. For the purpose of the 
present invention, rectifier 6 is added so that the high current from the 
high current source consisting of elements 3, 4, 15, 17, 18 and 19 is not 
impeded during discharges by the high impedance of winding 9 and resistor 
14. As in FIG. 5b, the power sources are in mutually aiding connection, 
presenting a negative potential to the spark plugs. Since a plurality of 
spark plugs are required, a distributor 13 has been added as a new 
element. The distributor is described under FIG. 1, and operates, in the 
present embodiment, in a similar manner. 
The ignition coil 7, in this embodiment, is different from the iginition 
coil 7 used in FIG. 1, in that the primary winding 8 is not connected with 
the secondary winding 9. This difference is necessary, in order to prevent 
the high current power source from discharging its energy through the 
primary winding 8. The optional current disconnect element 18 and the 
optional resonating inductor 19 operate in a manner identical to that 
described under FIGS. 5a and 5b. 
FIG. 3 shows another preferred embodiment of the present invention in 
accordance with the second preferred embodiment described generally under 
FIG. 5b and in more detail under FIG. 2, and which again employs two 
coordinated series connected power sources. FIG. 3 shows a plurality of 
rectifiers 6a through 6d. One rectifier is provided for each spark plug in 
parallel connection with secondary winding 9, resistor 14 and distributor 
13, such that the high current from the high current source bypasses also 
the distributor. In this case, the voltage drop across the distributor 
does not reduce the intensity of the sustained arc, and the distributor 
contacts may be constructed for a current rating lower than that required 
to pass the entire current from the high current source. 
FIG. 4 shows another preferred embodiment of the present invention as 
described generally under FIG. 5b, and in more detail under FIG. 2 which 
employs two coordinated series connected power sources, and where all 
elements are similar to the same numbered elements in FIGS. 5b and 2. 
The only difference is that in FIG. 4, the two power sources, being series 
connected, have been reversed in their positions in the current loop, 
compared with their positions as described in FIG. 2, with the high 
current source consisting of elements 3, 4, 15, 17, 18 and 19 located 
close to the distributor, while the high voltage source is close to ground 
potential. The rectifier 6, in this case, bypasses the entire ignition 
coil 7. 
It should be understood that of the various circuit elements combining to 
form the embodiments of the present invention, several elements have a 
return path to a common ground, which is typically the metal mass of an 
engine or the chassis of an automobile. These return paths are marked by 
the standard ground symbol on the figures, but are, for the sake of 
brevity, not described in detail in this specification, other than by this 
reference. 
While preferred embodiments of the present invention have been described, 
various modifications and substitutions may be made within the scope and 
spirit thereof, by those skilled in the art.