U.S. patent number 3,926,165 [Application Number 05/440,996] was granted by the patent office on 1975-12-16 for multiple spark discharge system.
This patent grant is currently assigned to Autotronic Controls Corporation. Invention is credited to James Walter Merrick.
United States Patent |
3,926,165 |
Merrick |
December 16, 1975 |
Multiple spark discharge system
Abstract
A multiple spark discharge ignition system having a high energy
capacitative discharge ignition current which provides multiple
striking at the spark gap of a combustion chamber. The timing of
the firing can be retarded relative to the power stroke. The
duration of the time interval during which the strikes occur is
also controlled. In its preferred form, the present invention
utilizes the ignition points of an internal combustion engine for
its timing signal and the distributor for distributing the high
voltage current to the spark gap associated with each of the
combustion chambers.
Inventors: |
Merrick; James Walter (El Paso,
TX) |
Assignee: |
Autotronic Controls Corporation
(El Paso, TX)
|
Family
ID: |
23751063 |
Appl.
No.: |
05/440,996 |
Filed: |
February 11, 1974 |
Current U.S.
Class: |
123/636;
123/637 |
Current CPC
Class: |
F02P
3/0861 (20130101); F02P 15/10 (20130101) |
Current International
Class: |
F02P
15/10 (20060101); F02P 15/00 (20060101); F02P
3/08 (20060101); F02P 3/00 (20060101); F02P
001/00 () |
Field of
Search: |
;123/148E,148OC |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Cangelosi; Joseph
Attorney, Agent or Firm: Bates; Marcus L.
Claims
I claim:
1. In an internal combustion engine having a combustion chamber
within which an ignition spark is to be provided with the spark
occuring in timed sequence respective to engine rotation, said
engine having means providing a timing signal, a DC current source,
and a distributor connected to deliver high voltage current for the
spark; the improvement comprising:
a multiple spark discharge apparatus for delivering current to the
distributor in response to said timing signal; said discharge
apparatus including means forming a multiple spark discharge
control circuit connected to deliver multiple strikes for said
spark when said circuit is energized;
means, including circuitry, forming a DC/DC converter for
increasing the voltage of said DC current source, and connected to
supply current to said multiple spark discharge control
circuit;
a firing duration control circuit means connected to said multiple
spark discharge control circuit for controlling the duration of
firing each time said timing signal is received;
an engine timing control circuit means for changing the time of
firing respective to engine rotation; said engine timing control
circuit means divides the firing interval between successive firing
pulses into first and second intervals, means by which the ratio of
said first and second intervals is made proportional to a first and
second current source, and means for adjusting one said current
source to thereby provide an adjustable ignition timing signal;
an engine timing signal conditioning circuit means connected to
said engine timing control circuit for conditioning the timing
signal, to thereby provide a signal for driving said engine timing
control circuit;
so that a spark of multi-strikes is provided for initiating
combustion each stroke of the internal combustion engine with the
duration and time of the multi-strikes being controlled.
2. The multiple spark discharge apparatus of claim 1 wherein said
firing duration control circuit means includes a duty cycle
controlled single shot that divides the firing interval between
successive firing pulses into first and second intervals, circuit
means by which the ratio of said first and second intervals is made
proportional to a first and second current source, means for
adjusting one said current source to thereby provide an adjustable
firing duration control signal.
3. In an internal combustion engine having a combustion chamber
within which an ignition spark is to be provided with the spark
occuring in timed sequence respective to engine rotation, said
engine having means providing a timing signal, a DC current source,
and a distributor connected to deliver high voltage current for the
spark; the improvement comprising:
a multiple spark discharge apparatus for delivering current to the
distributor in response to said timing signal;
said discharge apparatus including means forming a multiple spark
discharge control circuit connected to deliver multiple strikes for
said spark when said circuit is energized;
means, including circuitry, forming a DC/DC converter for
increasing the voltage of said DC current source, and connected to
supply current to said multiple spark discharge control circuit; a
discharge capacitor connected to be charged by said DC/DC
converter; circuit means including a high-tension coil connected to
provide said spark, said circuit means being connected to cause
said discharge capacitor to discharge into said high-tension coil
when the capacitor has been substantially charged;
a firing duration control circuit means connected to said multiple
spark discharge control circuit for controlling the duration of
firing each time said timing signal is received;
an engine timing control circuit means for changing the time of
firing respective to engine rotation;
an engine timing signal conditioning circuit means connected to
said engine timing control circuit for conditioning the timing
signal, to thereby provide a signal for driving said engine timing
control circuit;
so that a spark of multi-strikes is provided for initiating
combustion for each power stroke of the internal combustion engine,
with the duration and time of the strike being controlled.
4. The multiple spark discharge apparatus of claim 3 wherein said
firing duration control circuit means includes a duty cycle
controlled single shot that divides the firing interval between
successive firing pulses into first and second intervals, circuit
means by which the ratio of said first and second intervals is made
proportional to a first and second current source, means for
adjusting one said current source to thereby enable the timing
signal to be adjusted.
5. In combination with an internal combustion engine having a
source of DC current, and a spark gap connected to ignite a
combustible mixture contained within a combustion chamber thereof
in timed relationship to the power stroke, means generating a
timing signal in timed relationship to the power stroke of the
engine; a multi-spark discharge system;
said system including means forming an engine timing control
circuit, a low voltage to high voltage DC converter circuit, and a
multi-spark discharge control circuit; circuit means connecting
said DC converter circuit to provide a source of power for said
discharge control circuit;
said engine timing control circuit includes means that divides the
firing interval between successive firing pulses into first and
second intervals, means by which the ratio of said first and second
intervals is made proportional to a first and second current
source, and means for adjusting one said current source to thereby
provide an adjustable timing signal;
circuit means connecting said timing signal to said engine timing
control circuit for producing an output signal in timed
relationship respective of said timing signal, circuit means by
which the timed relationship between said timing signal and said
output signal can be remotely controlled;
circuit means connecting said output signal to said discharge
control circuit for causing said discharge control circuit to
supply said spark gap with high-tension current during the time
interval of said output signal.
6. The combination of claim 5 wherein said circuit means connecting
said timing signal to said enging timing control includes a signal
conditioning circuit means for changing the timing signal into a
signal having a wave form of only spaced pulses with a pulse
occuring for each of the timing signals.
7. In combination with an internal combustion engine having a
source of DC current, and a spark gap connected to ignite a
combustible mixture contained within a combustion chamber thereof
in timed relationship to the power stroke, and means generating a
timing signal in timed relationship to the power stroke of the
engine; a multi-spark discharge system;
said system including means forming an engine timing control
circuit, a low voltage to high voltage DC converter circuit, and a
multi-spark discharge control circuit; circuit means connected to
said DC converter circuit to provide a source of power for said
discharge control circuit;
a firing duration control circuit means connected between said
engine timing control circuit and said multi-spark discharge
control circuit for controlling the duration of the output of the
last said circuit; said firing duration control circuit means
divides the firing interval between successive firing pulses into
first and second intervals, and further includes means by which the
ratio of said first and second intervals is made proportional to a
first and second current source, and means for adjusting one said
current source to thereby provide an adjustable timing signal;
circuit means connecting said timing signal to said engine timing
control circuit for producing an output signal in timed
relationship respective of said timing signal, circuit means by
which the timed relationship between said timing signal and said
output signal can be remotely controlled;
circuit means connecting said output signal to said discharge
control circuit for causing said discharge control circuit to
supply said spark gap with high-tension current during the time
interval of said output signal.
8. In combination with an internal combustion engine having a
source of DC current, and a spark gap connected to ignite a
combustible mixture contained within a combustion chamber thereof
in timed relationship to the power stroke, and means generating a
timing signal in timed relationship to the power stroke of the
engine; a multi-spark discharge system;
said system including means forming an engine timing control
circuit, a low voltage to high voltage DC converter circuit, and a
multi-spark discharge control circuit; circuit means connecting to
said DC converter circuit to provide a source of power for said
discharge control circuit;
said multiple spark discharge control circuit includes a discharge
capacitor connected to be charged by said DC converter, a
high-tension coil connected to the spark gap; circuit means,
including a unijunction transistor, connected to cause said
discharge capacitor to discharge into said high-tension coil when
said transistor senses that the capacitor has been substantially
charged;
circuit means connecting said timing signal to said engine timing
control circuit for producing an output signal in timed
relationship respective of said timing signal, circuit means by
which the timed relationship between said timing signal and said
output signal can be remotely controlled;
circuit means connecting said output signal to said discharge
control circuit for causing said discharge control circuit to
supply said spark gap with high-tension current during the time
interval of said output signal.
9. The combination of claim 8 wherein said circuit means connecting
said timing signal to said engine timing control includes a signal
conditioning circuit means for changing the timing signal into a
signal having a wave form of only spaced pulses with a pulse
occuring for each of the timing signals.
10. Method of producing multiple spark discharges for the spark gap
of an internal combustion engine having a combustion chamber
comprising the steps of:
1. producing a timing signal representative of each time combustion
should occur in a combustion chamber of the internal combustion
engine;
2. adjusting the duration of the timing signal to a value
representative of the time in which the multiple sparks are to
occur within the combustion chamber;
3. connecting a source of high-tension current to the spark gap and
causing said high-tension current to flow across the spark gap each
time said source is energized, said high-tension current having a
frequency which imposes a multiplicity of sparks across the spark
gap during the time interval of the duration of the timing
signal;
4. energizing said source of high-tension current each time said
timing signal is produced;
5. converting the timing signal of step (1) into a first and second
electrical signal which represent first and second time intervals
and which jointly represent the firing interval between successive
firing pulses;
6. electrically making the ratio between said first and second
intervals proportional to a first and second current source;
7. adjusting one said current source to thereby change the timing
signal duration.
11. The method of claim 10, and further including the step of
adjusting the duration of the timing signal electrically so as to
enable the engine timing to be remotely controlled.
12. The method of claim 10 wherein said hi-tension current is
obtained according to the following steps:
5. connecting a discharge capacitor to a hi-tension ignition coil
and charging and discharging the capacitor at a rate to attain the
frequency recited in step (3);
6. carrying out step (5) for the duration of the timing signal so
that a plurality of sparks occur across the spark gap each time
ignition occurs in the combustion chamber.
13. Method of producing multiple spark discharges for the spark gap
of an internal combustion engine having a combustion chamber
comprising the steps of:
1. producing a timing signal representative of each time combustion
should occur in a combustion chamber of the internal combustion
engine;
2. adjusting the duration of the timing signal to a value
representative of the time in which the multiple sparks are to
occur within the combustion chamber;
3. connecting a source of high-tension current to the spark gap and
causing said high-tension current to flow across the spark gap each
time said source is energized, said high-tension current having a
frequency which imposes a multiplicity of sparks across the spark
gap during the time interval of the duration of the timing
signal;
4. energizing said source of high-tension current each time said
timing signal is produced;
5. connecting a discharge capacitor to a high-tension ignition coil
and charging and discharging the capacitor at a rate to attain the
frequency recited in step (3);
6. carrying out step (5) for the duration of the timing signal so
that a plurality of sparks occur across the spark gap each time
ignition occurs in the combustion chamber.
14. In an internal combustion engine having a combustion chamber
within which an ignition spark is to be provided with the spark
occuring in timed sequence respective to engine rotation, said
engine having means providing a timing signal, a DC current source,
and a distributor connected to deliver high voltage current for the
spark; the improvement comprising:
a multiple spark discharge apparatus for delivering current to the
distributor in response to said timing signal;
said discharge apparatus including means forming a multiple spark
discharge control circuit connected to deliver multiple strikes for
said spark when said circuit is energized;
means, including circuitry, forming a DC/DC converter for
increasing the voltage of said DC current source, and connected to
supply current to said multiple spark discharge control
circuit;
a firing duration control circuit means connected to said multiple
spark discharge control circuit for controlling the duration of
firing each time said timing signal is received;
said firing duration control circuit means includes a duty cycle
controlled single shot that divides the firing interval between
successive firing pulses into first and second intervals, circuit
means by which the ratio of said first and second intervals is made
proportional to a first and second current source, means for
adjusting one said current source to thereby provide an adjustable
firing duration control signal;
an engine timing control circuit means for changing the time of
firing respective to engine rotation; an engine timing signal
conditioning circuit means connected to said engine timing control
circuit for conditioning the timing signal, to thereby provide a
signal for driving said engine timing control circuit;
so that a spark of multi-strikes is provided for initiating
combustion with the duration and time of the strike being
controlled.
Description
BACKGROUND OF THE INVENTION
It is known that multiple strike ignition systems increase the
efficiency of internal combustion engines for the reason that the
combustion mixture in each of the combustion chambers is ignited
more often than would otherwise be realized when utilizing a single
strike ignition system. It is known that an internal combustion
engine often fails to have the gaseous mixture in all of the
combustion chambers thereof exploded on the power stroke, and
accordingly, this causes a significant increase in objectionable
emissions in the exhaust gases. Moreover, as the objectionable
emissions increase, the efficiency of the power plant decreases,
thereby causing increased cost of operation.
Complete combustion of the mixture of air and fuel contained in the
combustion chamber of an internal combustion engine is seemingly
unattainable because of scavenging and cylinder pressures, and
moreover is undesirable because of the materials of construction
necessarily incorporated into the fabrication of the engine
components; however, complete burning of the gaseous mixture to a
predetermined resultant reactant product is attainable where proper
and sustained ignition of the combustion mixture is effected, and
where the flame velocity is of a magnitude to cause propagation of
the flame to extend throughout the combustion chamber so that an
optimum reaction occurs thereby realizing maximum work from the
expansion of the gases.
It is therefore desirable to lower the objectionable emissions from
the exhaust gases of internal combustion engines while at the same
time increasing the power output and economy of operation thereof.
Moreover, it is prepared to attain these desirable attributes at a
minimum of cost and in a simple and uncomplicated manner so that
this desirable expedient can be enjoyed by anyone who operates a
motor vehicle.
SUMMARY OF THE INVENTION
This invention relates to multiple spark discharge apparatus for
delivering current to the spark plug of a combustion chamber of an
internal combustion engine. The time of firing as well as the
duration of the discharge is electronically controlled to thereby
enhance the efficiency of combustion.
The apparatus in its preferred form includes a multiple spark
discharge control circuit connected to deliver multiple strikes
across the spark plug when energized by a proper timing signal. A
converter changes low voltage DC to high voltage DC and is
connected to the multiple spark discharge control circuitry.
The firing duration and timing retard control circuit is connected
to the multiple spark discharge circuitry so that the duration and
timing of firing can be controlled for each power stroke of a
cylinder.
Accordingly, a primary object of the present invention is the
provision of a multiple spark discharge apparatus for delivering
multiple strikes across a spark gap of a combustion chamber of an
internal combustion engine to thereby cause ignition of the
combustable mixture contained within the combustion chamber to
occur in a more efficient manner.
Another object of the invention is to provide improvements in
multi-strike ignition systems for use in providing ignition within
a combustion chamber.
A further object of this invention is to disclose and provide
improvements in multi-strike ignition systems which has
incorporated therewith means by which the duration of the strikes
can be controlled.
A still further object of this invention is to provide a
multi-strike ignition system having means by which the time of the
strikes can be controlled relative to the power stroke of the
engine.
Another and still further object is to provide improvements in
multiple strike discharge circuitry which enables a greater number
of strikes to occur within a finite time interval.
These and various other objects and advantages of the invention
will become readily apparent to those skilled in the art upon
reading the following detailed description and claims and by
referring to the accompanying drawings.
The above objects are attained in accordance with the present
invention by the provision of a combination of elements which are
fabricated in a manner substantially as described in the above
abstract and summary.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a multi-strike discharge apparatus
made in accordance with the present invention;
FIG. 2 discloses several curves illustrating the wave form of a
conventional ignition system contrasted with the wave form of a
multi-strike ignition system as might be viewed by observing the
wave form of the current at the spark plug of an internal
combustion engine;
FIG. 3 is a diagrammatical, part schematical illustration of
circuitry arranged in accordance with the teachings of this
invention;
FIG. 4 discloses several different wave forms produced by various
ones of the circuitry of FIG. 3;
FIGS. 5 and 6 disclose a schematical representation of circuitry
for carrying out one form of the present invention;
FIG. 7 is a schematical representation of another form of part of
the circuitry disclosed in the foregoing figures;
FIG. 8 discloses a series of curves which sets forth the wave form
observed at various locations within the circuitry of FIG. 7;
FIGS. 9 and 11 set forth another form of part of the circuitry
disclosed in the foregoing figures;
FIG. 10 sets forth curves depicting the wave form produced at
various locations within the circuitry of FIG. 9; and,
FIGS. 12 - 14 disclose a number of curves which enable a
theoretical discussion of the merits of the present invention to be
more precisely considered.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 there is disclosed one form of the present invention
indicated by the arrow at numeral 10. A mounting plate 11 enables
the main body portion 12 to be affixed in close proximity to an
internal combustion engine. Circuitry is housed within the main
body while heat radiating fins 13 dissipate heat therefrom. The
apparatus of the present invention can be connected into the
ignition system of a conventional engine by utilizing the
electrical connections or terminals 14 - 20 as will be discussed in
greater detail later on in this disclosure.
In FIG. 2, the upper curve discloses a wave form of the voltage in
a conventional ignition system, while the lower curve illustrates
the wave form of the voltage which is attained by utilizing the
teachings of the present invention. In each curve, the breakdown
voltage V.sub.b is required to initiate a spark across the plug
gap, while V.sub.i is the ionizing voltage which is also the
voltage measured across a gap after current flow has been
initiated.
In FIG. 3 there is diagrammatically illustrated an electronics
ignition system made in accordance with the present invention. The
circuitry is connected to a low voltage source of current at 14, 16
and produces a high voltage current at 15 of a particular wave
form. The circuitry is comprised of an engine timing signal
conditioning circuit A having the input thereof connected to a
timing signal at 17, which for purposes of this embodiment is
illustrated as being in the form of a conventional set of ignition
points 21. The conditioned timing signal provides a signal for the
input of the engine timing control circuit B, which can be remotely
controlled at 18 so as to selectively retard the timing of the
ignition, as may be desired.
The output of the timing control provides a signal for the firing
duration control circuitry C. The last named circuitry has a remote
duration control 19 for controlling the duration of the firing
portion of the ignition cycle.
A converter D converts the low voltage DC supply into high voltage
DC to thereby provide the multi-spark discharge control circuitry E
with a high voltage supply. The firing duration control circuitry
output causes the circuitry E to impose high voltage upon the
transformer F to thereby provide the distributor 23 with a
plurality of high voltage sparks which is transferred to the spark
plug 24 of the illustrated internal combustion engine cylinder
chamber 25.
In FIG. 4 the various curves A - F, respectively, represent the
preferred input signal to each of the circuits, A - F,
respectively, of FIG. 3. Looking particularly to curve A of FIG. 4,
it is seen that the impulses are spaced 90.degree. apart for an
eight cylinder engine, and, are of a wave form such as may be
obtained with a magnetic pulse triggered distributor. In curve C,
each of the impulses have been converted to a square wave of about
0.1.degree. to 20.degree. in duration, respective to engine crank
shaft rotation. The impulses of Curve E is 1.degree. - 40.degree.
in duration. The multiple strikes of the impulse of curve F is of
the same duration and timing as curve E. Hence, it can be seen that
the timing signal A is conditioned by circuit A to provide a
cleaner signal B which in turn is converted into signal C, with the
latter being adjustable in time as noted. The signal E corresponds
in duration to that of signal F.
FIGS. 5 and 6 jointly represent circuitry for carrying out the
present invention, wherein various portions of the circuitry have
been isolated by dot-dash lines and provided with letters A - F,
respectively, which relate to the block diagram A - F,
respectively, of FIG. 3. As seen in FIG. 5, a terminal block is
provided, having connectors 14 - 20 which can be related to the
similar terminal block of FIG. 1.
Those skilled in the art, having digested this entire disclosure,
will be able to comprehend the purpose and operation of the
circuitry depicted by FIGS. 5 and 6. The circuit values of the
various electrical components disclosed in FIGS. 5 and 6 are as
follows:
CIRCUIT VALUES OF FIGURES 5 AND 6
______________________________________ R1 .47 ohms R20 4.7K ohms
R39 2.2K ohms R2 .47 ohms R21 2K ohms R40 1K ohms R3 0.47 ohms R22
1K ohms R41 2.2K ohns R4 0.47 ohms R23 R42 2.2K ohms R5 1K ohms R24
1K ohms R43 15K ohms R6 1K ohms R25 4.7K ohms R44 4.7K ohms R7 220
ohms R26 10K ohms R45 1K ohms R8 47 ohms R27 1K ohms R46 4.7K ohms
R9 4.7K ohms R28 68 ohms R47 4.7K ohms R10 1K ohms R29 10K ohms R48
4.7K ohms R11 1K ohms R30 1K ohms R49 100 ohms R12 100 ohms R31 R50
100K ohms R13 1K ohms R32 1K ohms R51 10K ohms R14 220 ohms R33 22K
ohms R52 4.7K ohns R15 220 ohms R34 10K ohms R53 1K ohms R16 11K
ohms R35 4.7K ohms R54 R17 1K ohms R36 1K ohms R55 100 ohms R18 10K
ohms R37 22K ohms R56 1K ohms R19 1K ohms R38 1K ohms R55' 220 ohms
R56' 200 ohms C1 250 .mu.f D1 1N4001 C2 250 D2 1N4001 C3 D3 1N4001
C4 0.03 D4 1N4001 C5 .005 D5 1N4937 C6 .005 D6 1N4937 C7 .01 D7
1N4937 C8 .01 D8 1N4937 C9 35 D9 1N4937 C10 .01 D10 1N4154 C11 4.7
D11 1N4154 C12 2.2 D12 C13 .002 D13 1N5229 C14 .05 D14 1N4154 C15
.01 D15 1N4154 C16 .001 D16 1N4154 C17 .1 D17 1N4154 C18 1.0 D18
1N4154 D19 1N4001 D20 1N4001 Q1 T1P36A Q2 T1P36A Q3 T1P36A Q4
T1P36A Q5 2N3569 Q6 2N4355 Q7 T1597 Q8 T1597 Q9 2N6027 Q10 T1597
Q11 T1597 Q12 T1597 Q13 T1597 Q14 T1597 Q15 MJE710 Q16 2N4250 Q17
2N4250 Q18 T1597 Q19 T1597 Q20 2N4250 Q21 2N4250 Q22 T1597 Q23
T1597 Q24 T1597 Q25 T1597 Q26 T1597 Q27 2N4250 Q28 T1597
______________________________________
In the embodiment of FIGS. 7 and 8, there is disclosed a constant
and adjustable duty cycle single shot having an input 40 of a wave
form disclosed by numeral 40 in FIG. 8. The output 41 of the
circuitry of FIG. 7 has a wave form corresponding to the curve
indicated by the arrow at numeral 41 of FIG. 8. In FIG. 7, the
junctions 42 and 43, respectively, correspond to the wave forms 42
and 43, respectively, of FIG. 8. It will be noted that the time
interval between the impulses of the curves depends upon the number
of cylinders and firing cycle of the engine under
consideration.
Looking now to the details of FIG. 9, which discloses a simplified
embodiment of the discharge circuitry illustrated at E in FIGS. 3,
5, and 6, it will be noted that the high voltage from the converter
D of FIG. 3, for example, is connected at junction 50 of FIG. 9,
while the output from the control circuitry C of FIG. 3 forms an
input at junction 44 for the circuitry of FIG. 9. A high tension
ignition transformer T broadly corresponds to transformer F of FIG.
3. The wave form of the current at various locations 44 - 49
throughout the circuit of FIG. 9 is disclosed by curves 44 - 49 in
FIG. 10.
FIG. 11 shows one form of the invention which broadly corresponds
to the circuitry D of FIG. 3. The low voltage DC to high voltage DC
converter is comprised of a transformer T-1 having the illustrated
primary and a tapped secondary N-1, N-2, N-3, connected to
transformer windings T-2, having primary windings N-4, N-5, and
secondary windings N-6, N-7. Disconnect 53 is provided for
convenience. The output from transformer T-1 is connected into the
circuitry of FIG. 9 at numeral 50.
FIGS. 12 - 14 disclose the operational characteristics of the
present multi-spark ignition system. In FIG. 12, the amperage 55 is
plotted against the voltage 56. The voltage feedback is indicated
by curve 57 while curve 58 discloses the wave form obtained with a
typical current feedback converter made in accordance with the
present invention. Numerals 60, 62, 64, 66, 68, shows the curve as
its amplitude increases to 1 amp and discharges at 300 volts. Curve
57 continues as indicated at 70 or 72.
In FIG. 13 the amperage input 74 is plotted against the output
amperage 75. Curve 76 relates to voltage feedback while curve 77
relates to current feedback.
In FIG. 14, capacitor voltage 78 is plotted against time 77. Curve
82 is a plot of a converter made in accordance with the present
invention, while curve 84 is the wave form of a voltage feedback
converter. The curves commence at 80 and extend along line 16 and
88, with the design center being indicated by numeral 88'. The
normal recharge range is measured between 88' and 90. Numeral 92
indicates the excess voltage rise due to converter kickback spikes,
and is illustrated as being 40%, with 30 - 40% being typical.
OPERATION
As indicated in FIG. 3, in conjunction with various other remaining
Figures, the present ignition system is comprised of various
combinations of functional blocks A - E. The input to the engine
timing signal conditioning block A can be the conventional breaker
points associated with an automotive type engine, or alternatively,
can be a magnetic pickup, photocell and window arrangement, or any
other signal generating means associated or indexed with the
rotating crank shaft of the engine, so long as the signal provides
a timed indication of piston position. The function of the timing
signal conditioning circuitry is to change the wave form A of FIG.
4 to that seen illustrated by curve B. This expedient provides
short negative electrical pulses which are suitable for driving the
retard control circuitry B, seen in FIGS. 3 and 6.
The engine timing control circuitry B, seen in FIGS. 3, 6, 7, and
8, is basically a duty cycle controlled single shot that divides
the firing interval T between successive firing pulses into two
intervals T-1 and T-2, the ratio of which is proportional to the
ratio of two current sources I-1 and I-2, according to the
relationship as follows: ##EQU1##
By making one or both current sources adjustable, a new timing
signal can be generated at the end of T-1, which can be adjusted
electronically without readjusting the distributor. This novel
expedient makes possible remote control of ignition timing
electronically without the requirement of mechanical linkage and
the like. One means by which this desirable expedient is carried
out is disclosed in the simplified circuitry of FIG. 7, and is
shown in detail in FIGS. 5 and 6.
Looking now to the details of the firing duration control circuitry
C disclosed in FIGS. 3, 5, and 6, it will be noted that this
circuit is essentially the same as the timing control circuit
previously discussed in conjunction with FIGS. 7 and 8, except that
the circuitry is used to control the firing duration of the
multi-spark discharge circuitry E rather than being used to control
the relationship of T.sub.1 and T.sub. 2. The circuit C is
triggered by the timing signal generated by the output of the
timing control circuit B. This signal generates a gate signal which
controls the firing duration. It may also be controlled
electronically and remotely as seen in FIGS. 5 and 6, so as to
enable selection of the most optimum engine operating
condition.
Looking now to the converter D of FIGS. 3, 5, 6, and 11, it will be
seen that this circuit converts the 12 volts DC, for example, of
the automotive electrical system into the 400 volts DC source
needed to charge the energy storage capacitor of the multi-spark
discharge circuit. The converter must have the capability of
recharging the energy storage capacitor in ample time to obtain the
required multiple discharges on each firing stroke of each of the
cylinders of the internal combustion engine, and at the same time,
the circuitry must be efficient in order to prevent excessive
heating beyond the limits which can be tolerated by the individual
components thereof.
Stated again, the simplified circuitry of FIG. 9 is a discharge
circuit with various wave forms produced therein being disclosed in
FIG. 10, wherein the curve 44 shows the firing duration for each
power stroke of one of the pistons of the engine. The curve 45 of
FIG. 10 shows a plurality of strikes for each successive cylinder
firing, with the individual strikes being characterized by the
discharge time TD and time of recharge TR. The sloped portion of
the time of recharge relates to the DC/DC converter recharging the
discharge capacitor.
Curve 46 illustrates the wave form of the voltage in the high
tension ignition transformer primary. Numeral 52 indicates the
discharge time TD which is determined by the inductance of the high
tension transformer and discharge capacitor. Numeral 52' is the
recharge time TR of the discharge capacitor.
The firing voltage is seen illustrated by curve 47, wherein +
V.sub.p is related to the VJT or Q.sub.2 firing voltage, which is
approximately equal to the source or battery voltage.
Curve 48 illustrates the VJT bias pulses, while curve 49
illustrates the SCR gate drive pulses.
The multi-spark discharge circuit of FIG. 9 repetitively discharges
the illustrated energy storage capacitor into the primary of the
high-tension ignition transformer T as fast as the DC/DC converter
(FIG. 2D, FIG. 5D, and FIG. 11) can recharge it during the firing
duration gate pulse. In this circuit, the unijunction transistor
senses when the energy storage capacitor is charged to an
appropriate level, preferably 90% of maximum, as determined by the
battery voltage. Those skilled in the art will readily understand
the remaining details of the current flow and wave forms in the
simplified circuit presented in the embodiment of FIGS. 9 and 10,
as well as the more specific embodiment of FIGS. 5 and 6.
Looking now to the multi-spark discharge circuitry disclosed in
FIGS. 3, 5, 6, and 11, it will be seen that this circuit
repetitively discharges the energy storage capacitor into the
primary of the high tension ignition transformer as quickly as the
converter can recharge the capacitor during the firing duration
gate pulse. In this circuit, the unijunction transistor senses a
threshold voltage which preferably occurs when the energy storage
capacitor is charged to 90% of maximum as determined by the battery
voltage.
The present invention provides low dissipation and output current
when shorted by the SCR during the discharge pulse, thereby
preventing latch-up of the SCR and excessive heating of the
converter transistors. The present circuitry also provides a very
high output current from 30 to 90% of the output voltage, which
enables rapid recharging of the capacitor at the end of each
discharge pulse. The converter of the present invention draws
minimal current when the discharge capacitor is fully charged
between firing sequences, thereby minimizing battery drain and heat
buildup.
The advantage of a conventional prior art current feedback
converter for ignition systems is its high efficiency while
handling light to heavy loads because it employs a base drive which
is proportional to the load, therefore, its output voltage does not
rise appreciably at light loads. However, these prior art systems
suffer the disadvantage of an excessive heat dissipation and output
current during output short on the discharge pulse, thereby causing
possible SCR latchup and destruction of the converter transistors,
which renders conventional current feedback concepts unsuitable for
reliable ignition systems.
The use of a conventional prior art voltage feedback converter is
advantageous in a capacitor discharge electronic ignition circuitry
because of the simplicity of the circuit and beacuse it can be
designed for low dissipation and current drain when the output is
shorted during the discharge pulse. However, the disadvantages for
such a system is its poor efficiency at light loads due to the high
base drive to the transistors and because of the required base
current limiting resistors. Moreover, the output current drops
linearly with the decreasing output voltage thereby requiring more
time to recharge the discharge capacitor. Furthermore, high peak
collector currents at light loads cause high energy spikes of
voltage to occur at the collector of the transistors and output,
thereby causing the output voltage to rise above the design center
which results in excessive voltage stress on various circuit
components, especially at light loads between the firing
sequences.
The converter of the present invention enjoys all the advantages of
the voltage feedback and current feedback systems and avoids all of
the foregoing undesirable attributes. This desirable expedient is
accomplished in accordance with the present invention by the
provision of circuitry fabricated in a manner exemplified by the
present embodiments.
As seen in the hypothetical curves presented in FIGS. 12 - 14, when
the output voltage is of a value between the numerals 59 and 60,
the converter works as a voltage feedback inverter with very little
drive thereby minimizing the occurrence of stall current during
each discharge pulse of ignition. Temperature compensated forward
bias is provided by the resistors R1-4 and the diodes 5 and 6 of
FIG. 11, for example. This increased forward drop of the diodes at
cold temperature compensates for the increased base drive required
by Q1-Q4 at cold temperature. Positive current feedback occurs
through T-2, the current feedback transformer, but is shunted away
from the transistor bases by the presence of diodes D-1 and D-2
whenever the output falls below numeral 60. Whenever the output
goes above the value indicated by numeral 62 of FIG. 12, there is
sufficient voltage across the voltage feedback windings N-1 and N-2
to prevent the current feedback from being shunted away from the
transistor bases, and therefore, above numeral 62 the converter
works in the current feedback mode. The current feedback passes
from windings N-6 and N-7, through D-3 and D-4, and through the
current balancing resistors R-5, R-8 to the transistor bases
between the points indicated by numerals 64 and 66. Therefore,
essentially constant current is available along line 64 to recharge
the discharge capacitor. The available current above the value
indicated by numeral 66 quickly drops to zero thereby preventing
excessive voltage stress of the circuit components between the
firing sequences. Above point 66 a slight amount of voltage
feedback is provided to stabilize the circuitry through means of
R-1 and R-4, which stabilize the converter when there is no low
current to provide current feedback. In normal operation, there is
sufficient energy kickback from the high tension ignition
transformer to recharge the discharge capacitor above point 62,
thereby allowing rapid recharge along the time interval 64 between
numerals 62 and 66.
The output is at zero during the actual discharge pulse which is a
low current and dissipation point for the converter. A comparison
of the recharge time of the converter of FIGS. 5 and 6, for
example, with a conventional voltage feedback converter is shown in
FIG. 14. Those skilled in the art will now appreciate the novel and
heretofore unknown advantages of the present invention over the
prior art forms of ignition systems.
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