U.S. patent number 3,738,339 [Application Number 05/205,186] was granted by the patent office on 1973-06-12 for electronic ignition spark advance system.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Gerald O. Huntzinger, Byron W. Johnson, Leonard J. Sheldrake.
United States Patent |
3,738,339 |
Huntzinger , et al. |
June 12, 1973 |
ELECTRONIC IGNITION SPARK ADVANCE SYSTEM
Abstract
An electronic ignition spark advance system for use with
internal combustion engine transistor ignition systems having an
ignition coil primary winding switching transistor. A reference
pulse, produced a selected number of degrees before the top dead
center position of each engine piston, enables an ignition spark
advance gate to gate a series of crankshaft position pulses, each
indicating one degree of crankshaft rotation, to a counter circuit.
When the counter circuit has counted the number of crankshaft
position pulses equal to the number of selected degrees before top
dead center the reference pulses are produced, an ignition signal
is produced which extinguishes the ignition coil primary winding
switching transistor and operates circuitry which produces a signal
which may disenable the ignition spark advance gate. To provide
speed ignition spark advance, however, delay circuitry responsive
to each ignition signal provides two consecutive delay periods
during which the disenabling of the ignition spark advance gate is
delayed. Consequently, the counter circuit continues to count
crankshaft position pulses during the delay periods, thereby
providing a speed ignition spark advance in degrees equal to the
number of crankshaft position pulses counted during the delay
periods at any engine speed. To provide two speed ignition spark
advance limits, the first delay period is terminated with a first
selected crankshaft position pulse count if it occurs before the
end thereof and the second delay period is terminated with a second
greater selected crankshaft position pulse count if it occurs
before the end thereof. To provide vacuum ignition spark advance, a
vacuum spark advance signal is provided at the conclusion of the
delay periods for the number of crankshaft position pulses equal to
the degrees of vacuum ignition spark advance required which enables
the ignition spark advance gate to gate the crankshaft position
pulses to the counter circuit after the delay periods.
Inventors: |
Huntzinger; Gerald O.
(Anderson, IN), Sheldrake; Leonard J. (Noblesville, IN),
Johnson; Byron W. (Anderson, IN) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
22761161 |
Appl.
No.: |
05/205,186 |
Filed: |
December 6, 1971 |
Current U.S.
Class: |
123/406.63;
123/609 |
Current CPC
Class: |
F02P
5/15 (20130101); F02P 5/1551 (20130101); Y02T
10/46 (20130101); Y02T 10/40 (20130101) |
Current International
Class: |
F02P
5/15 (20060101); F02P 5/155 (20060101); F02P
5/145 (20060101); F02p 005/04 (); F02p
001/00 () |
Field of
Search: |
;123/148E,117R,117A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Assistant Examiner: Cox; Ronald B.
Claims
What is claimed is:
1. An electronic ignition spark advance system comprising in
combination with an internal combustion engine and an associated
transistor ignition system having an ignition coil primary winding
switching transistor, means for producing a series of crankshaft
position pulses, each corresponding to one degree of rotation of
the crankshaft of said internal combustion engine, means for
producing a reference pulse a selected number of degrees before the
top dead center position of each piston of said internal combustion
engine, a counter circuit having an input terminal and a plurality
of output terminals, each corresponding to a binary code bit for
counting said crankshaft position pulses and producing upon said
output terminals thereof the binary code representation of the
number of said crankshaft position pulses counted thereby, an
ignition spark advance gate circuit which, when enabled, gates said
series of crankshaft position pulses to said input terminal of said
counter circuit, means responsive to the binary code
representation, upon said output terminals of said counter circuit,
of the number of said crankshaft position pulses counted by said
counter circuit equal to said selected number of degrees before the
top dead center position of each piston of said internal combustion
engine at which each said reference pulse is produced for producing
an ignition signal, means responsive to each of said reference
pulses for producing a start count signal and to each of said
ignition signals for producing a full count signal, first delay
circuit means responsive to each of said ignition signals for
producing a first engine speed ignition spark advance signal of a
preselected duration, second delay circuit means responsive to the
end of each of said first engine speed ignition spark advance
signals for producing a second engine speed ignition spark advance
signal of a predetermined duration, a first count limit circuit
means responsive to the binary representation, upon said output
terminals of said counter circuit, of a first selected number of
crankshaft position pulses counted by said counter circuit for
producing a first engine speed ignition spark advance limit signal
which terminates said first engine speed ignition spark advance
signal if said counter circuit counts said first selected number of
crankshaft position pulses prior to the end thereof, a second count
limit circuit means responsive to the binary representation, upon
said output terminals of said counter circuit, of a second selected
greater number of crankshaft position pulses counted by said
counter circuit for producing a second engine speed ignition spark
advance limit signal which terminates said second engine speed
ignition spark advance signal if said counter circuit counts said
second selected number of crankshaft position pulses prior to the
end thereof, circuit means responsive to the end of said second
engine speed ignition spark advance signal for producing an engine
vacuum ignition spark advance signal, an enabling gate circuit
responsive to said start count signals, said first and second
engine speed ignition spark advance signals and said engine vacuum
ignition spark advance signals for producing an enabling signal for
said ignition spark advance gate circuit and to said full count
signals for producing a disenabling signal for said ignition spark
advance gate circuit in the absence of said first and second engine
speed and engine vacuum ignition spark advance signals, and dwell
circuit means responsive to a preselected number of said crankshaft
position pulses for initiating the operation of said transistor
ignition system to trigger said ignition coil primary winding
switching transistor conductive and to each of said ignition
signals for initiating the operation of said transistor ignition
system to extinguish said ignition coil primary winding switching
transistor.
2. An electronic ignition spark advance system comprising in
combination with an internal combustion engine and an associated
transistor ignition system having an ignition coil primary winding
switching transistor, means for producing a series of crankshaft
position pulses, each corresponding to one degree of rotation of
the crankshaft of said internal combustion engine, means for
producing a reference pulse a selected number of degrees before the
top dead center position of each piston of said internal combustion
engine, a counter circuit having an input terminal and a plurality
of output terminals, each corresponding to a binary code bit for
counting said crankshaft position pulses and producing upon said
output terminals thereof the binary code representation of the
number of said crankshaft position pulses counted thereby, an
ignition spark advance NOR gate which, when enabled, gates said
series of crankshaft position pulses to said input terminal of said
counter circuit, an ignition signal AND gate responsive to the
binary code representation, upon said output terminals of said
counter circuit, of the number of said crankshaft position pulses
counted by said counter circuit equal to said selected number of
degrees before the top dead center position of each piston of said
internal combustion engine at which each said reference pulse is
produced for producing an ignition signal, means responsive to each
of said reference pulses for producing a start count signal and to
each of said ignition signals for producing a full count signal,
first delay circuit means responsive to each of said ignition
signals for producing a first engine speed ignition spark advance
signal of a preselected duration, second delay circuit means
responsive to the end of each of said first engine speed ignition
spark advance signals for producing a second engine speed ignition
spark advance signal of a predetermined duration, a first count
limit circuit means responsive to the binary representation, upon
said output terminals of said counter circuit, of a first selected
number of crankshaft position pulses counted by said counter
circuit for producing a first engine speed ignition spark advance
limit signal which terminates said first engine speed ignition
spark advance signal if said counter circuit counts said first
selected number of crankshaft position pulses prior to the end
thereof, a second count limit circuit means responsive to the
binary representation, upon said output terminals of said counter
circuit, of a second selected greater number of crankshaft position
pulses counted by said counter circuit for producing a second
engine speed ignition spark advance limit signal which terminates
said second engine speed ignition spark advance signal if said
counter circuit counts said second selected number of crankshaft
position pulses prior to the end thereof, circuit means responsive
to the end of said second engine speed ignition spark advance
signal for producing an engine vacuum ignition spark advance
signal, an enabling NOR gate responsive to said start count
signals, said first and second engine speed ignition spark advance
signals and said engine vacuum ignition spark advance signals for
producing an enabling signal for said ignition spark advance gate
circuit and to said full count signals for producing a disenabling
signal for said ignition spark advance gate circuit in the absence
of said first and second engine speed and engine vacuum ignition
spark advance signals, and dwell circuit means responsive to a
preselected number of said crankshaft position pulses for
initiating the operation of said transistor ignition system to
trigger said ignition coil primary winding switching transistor
conductive and to each of said ignition signals for initiating the
operation of said transistor ignition system to extinguish said
ignition coil primary winding switching transistor.
3. An electronic ignition spark advance system comprising in
combination with an internal combustion engine and an associated
transistor ignition system having an ignition coil primary winding
switching transistor, means for producing a series of crankshaft
position pulses, each corresponding to 1.degree. of rotation of the
crankshaft of said internal combustion engine, means for producing
a reference pulse a selected number of degrees before the top dead
center position of each piston of said internal combustion engine,
a counter circuit having an input terminal and a plurality of
output terminals, each corresponding to a binary code bit for
counting said crankshaft position pulses and producing upon said
output terminals thereof the binary code representation of the
number of said crankshaft position pulses counted thereby, an
ignition spark advance NOR gate which, when enabled, gates said
series of crankshaft position pulses to said input terminal of said
counter circuit, an ignition signal AND gate responsive to the
binary code representation, upon said output terminals of said
counter circuit, of the number of said crankshaft position pulses
counted by said counter circuit equal to said selected number of
degrees before the top dead center position of each piston of said
internal combustion engine at which each said reference pulse is
produced for producing an ignition signal, a bi-stable
multivibrator circuit responsive to each of said reference pulses
for producing a start count signal and to each of said ignition
signals for producing a full count signal, a first monostable
multivibrator circuit responsive to each of said ignition signals
for producing a first engine speed ignition spark advance signal of
a preselected duration, a second monostable multivibrator circuit
responsive to the end of each of said first engine speed ignition
spark advance signals for producing a second engine speed ignition
spark advance signal of a predetermined duration, a first count
limit AND gate responsive to the binary representation, upon said
output terminals of said counter circuit, of a first selected
number of crankshaft position pulses counted by said counter
circuit for producing a first engine speed ignition spark advance
limit signal which terminates said first engine speed ignition
spark advance signal if said counter circuit counts said first
selected number of crankshaft position pulses prior to the end
thereof, a second count limit AND gate responsive to the binary
representation, upon said output terminals of said counter circuit,
of a second selected greater number of crankshaft position pulses
counted b said counter circuit for producing a second engine speed
ignition spark advance limit signal which terminates said second
engine speed ignition spark advance signal if said counter circuit
counts said second selected number of crankshaft position pulses
prior to the end thereof, circuit means responsive to the end of
said second engine speed ignition spark advance signal for
producing an engine vacuum ignition spark advance signal, an
enabling NOR gate responsive to said start count signals, said
first and second engine speed ignition spark advance signals and
said engine vacuum ignition spark advance signals for producing an
enabling signal for said ignition spark advance gate circuit and to
said full count signals for producing a disenabling signal for said
ignition spark advance gate circuit in the absence of said first
and second engine speed and engine vacuum ignition spark advance
signals, and dwell circuit means responsive to a preselected number
of said crankshaft position pulses for initiating the operation of
said transistor ignition system to trigger said ignition coil
primary winding switching transistor conductive and to each of said
ignition signals for initiating the operation of said transistor
ignition system to extinguish said ignition coil primary winding
switching transistor.
4. An electronic ignition spark advance system comprising in
combination with an internal combustion engine and an associated
transistor ignition system having an ignition coil primary winding
switching transistor, a crankshaft position sensor for producing a
series of crankshaft position pulses, each corresponding to
1.degree. of rotation of the crankshaft of said internal combustion
engine, a reference pulse generator for producing a reference pulse
a selected number of degrees before the top dead center position of
each piston of said internal combustion engine, a counter circuit
having an input terminal and a plurality of output terminals, each
corresponding to a binary code bit, for counting said crankshaft
position pulses and producing upon said output terminals thereof
the binary code representation of the number of said crankshaft
position pulses counted thereby, an ignition spark advance NOR gate
having input terminals and an output terminal for gating said
series of crankshaft position pulses to said input terminal of said
counter circuit, an ignition signal AND gate having input terminals
and an output terminal for producing an ignition signal, means for
connecting said output terminals of said counter circuit upon which
appear the binary code representation of the number of said
crankshaft position pulses counted by said counter circuit equal to
said selected number of degrees before the top dead center position
of each piston of said internal combustion engine at which each
said reference pulse is produced to respective input terminals of
said ignition signal AND gate, a bi-stable multivibrator circuit
having two input terminals and an output terminal for producing a
start count signal in response to said reference signals and a full
count signal in response to said ignition signals, means for
applying said reference signals and said ignition signals to
respective input terminals of said bi-stable multivibrator circuit,
a first monostable multivibrator circuit having an input, an output
and a reset terminal responsive to each of said ignition signals
for producing a first engine speed ignition spark advance signal of
a preselected duration, means for applying said ignition signals to
said input terminal of said first monostable multivibrator circuit,
a second monostable multivibrator circuit having an input, an
output and a reset terminal responsive to the end of each of said
first engine speed ignition spark advance signals for producing a
second engine speed ignition spark advance signal of a
predetermined duration, means for differentiating the trailing edge
of each of said first engine speed ignition spark advance signals,
means for applying said differentiated trailing edge of each said
first engine speed ignition spark advance signals to said input
terminal of said second monostable multivibrator circuit, a first
count limit AND gate having input terminals and an output terminal
for producing a first engine speed ignition spark advance limit
signal, means for connecting said output terminals of said counter
circuit upon which appear the binary representation of a first
selected number of crankshaft position pulses counter by said
counter circuit to respective said input terminals of said first
count limit AND gate, means for applying said first engine speed
ignition spark advance limit signal to said reset terminal of said
first monostable multivibrator circuit, a second count limit AND
gate having input terminals and an output terminal for producing a
second engine speed ignition spark advance limit signal, means for
connecting said output terminals of said counter circuit upon which
appear the binary representation of a second selected greater
number of crankshaft position pulses counted by said counter
circuit to respective said input terminals of said second count
limit AND gate, means for applying said second engine speed
ignition spark advance limit signal to said reset terminal of said
second monostable multivibrator circuit, means for differentiating
the trailing edge of said second engine speed ignition spark
advance signals, engine vacuum sensitive circuit means having an
input and an output terminal for producing an engine vacuum
ignition spark advance signal, means for applying said
differentiated trailing edge of said second engine speed ignition
spark advance limit signal to said input terminal of said engine
vacuum sensitive circuit means, an enabling NOR gate having input
terminals and an output terminal for producing an enabling signal
for said ignition spark advance NOR gate, means for applying both
said start count and said full count signals, both said first and
second engine speed ignition spark advance signals and said engine
vacuum ignition spark advance signal to respective input terminals
of said enabling NOR gate, means for applying said crankshaft
position pulses and said enabling signal to respective input
terminals of said ignition spark advance NOR gate, dwell circuit
having two input circuit means responsive to a preselected number
of said crankshaft position pulses for initiating the operation of
said transistor ignition system to trigger said ignition coil
primary winding conductive and to each of said ignition signals for
initiating the operation of said transistor ignition system to
extinguish said ignition coil primary winding switching transistor,
and means for applying said crankshaft position pulses and said
ignition signals to respective said input terminals of said dwell
circuit means.
5. An electronic ignition spark advance system comprising in
combination with an internal combustion engine and an associated
transistor ignition system having an ignition coil primary winding
switching transistor, a crankshaft position sensor having output
circuit means for producing a series of crankshaft position pulses,
each corresponding to 1.degree. of rotation of the crankshaft of
said internal combustion engine, a reference pulse generator having
output circuit means for producing a reference pulse a selected
number of degrees before the top dead center position of each
piston of said internal combustion engine, a counter circuit having
an input terminal, a plurality of output terminals, each
corresponding to a binary code bit, and a reset terminal for
counting said crankshaft position pulses and producing upon said
output terminals thereof the binary code representation of the
number of said crankshaft position pulses counted thereby, an
ignition spark advance NOR gate having input terminals and an
output terminal for gating said series of crankshaft position
pulses to said input terminal of said counter circuit, an ignition
signal AND gate having input terminals and an output terminal for
producing an ignition signal, means for connecting the said output
terminals of said counter circuit upon which appear the binary code
representation of the number of said crankshaft position pulses
counted by said counter circuit equal to said selected number of
degrees before the top dead center position of each piston of said
internal combustion engine at which each said reference pulse is
produced to respective input terminals of said ignition signal AND
gate, a bi-stable multivibrator circuit having two input terminals
and an output terminal, for producing a start count signal in
response to said reference signals and a full count signal in
response to said ignition signals, means for connecting said output
circuit means of said reference pulse generator to one of said
input terminals of said bi-stable multivibrator circuit, means for
connecting said output terminal of said ignition signal AND gate to
the other said input terminal of said bi-stable multivibrator
circuit and to said reset terminal of said counter circuit, a first
monostable multivibrator circuit having an input, an output and a
reset terminal responsive to each of said ignition signals for
producing a first engine speed ignition spark advance signal of a
preselected duration, means for connecting said output terminal of
said ignition signal AND gate to said input terminal of said first
monostable multivibrator circuit, a second monostable multivibrator
circuit having an input, an output and a reset terminal responsive
to the end of each of said first engine speed ignition spark
advance signals for producing a second engine speed ignition spark
advance signal of a predetermined duration, means including a
differentiator circuit for connecting said output terminal of said
first monostable multivibrator circuit to said input terminal of
said second monostable multivibrator circuit, a first count limit
AND gate having input terminals and an output terminal for
producing a first engine speed ignition spark advance limit signal,
means for connecting said output terminals of said counter circuit
upon which appear the binary representation of a first selected
number of crankshaft position pulses counted by said counter
circuit to respective said input terminals of said first count
limit AND gate, means for connecting said output terminal of said
first count limit AND gate to said reset terminal of said first
monostable multivibrator circuit, a second count limit AND gate
having input terminals and an output terminal for producing a
second engine speed ignition spark advance limit signal, means for
connecting said output terminals of said counter circuit upon which
appear the binary representation of a second selected greater
number of crankshaft position pulses counted by said counter
circuit to respective said input terminals of said second count
limit AND gate, means for connecting said output terminal of said
second count limit AND gate to said reset terminal of said second
monostable multivibrator circuit, engine vacuum sensitive circuit
means having an input and an output terminal for producing an
engine vacuum ignition spark advance signal, means including a
differentiator circuit for connecting said output terminal of said
second monostable multivibrator circuit to said input terminal of
said engine vacuum sensitive circuit means, an enabling NOR gate,
having input terminals and an output terminal for producing an
enabling signal for said ignition spark advance NOR gate, means for
connecting said output terminal of said bi-stable multivibrator
circuit, said output terminals of both said first and second
multivibrator circuits and said output terminal of said engine
vacuum sensitive circuitry to respective said input terminals of
said enabling NOR gate, means for connecting said output circuit
means of said crankshaft position sensor and said output terminal
of said enabling NOR gate to respective input terminals of said
ignition spark advance NOR gate, and dwell circuit having two input
circuit means responsive to a preselected number of said crankshaft
position pulses applied to one said input circuit means for
initiating the operation of said transistor ignition system to
trigger said ignition coil primary winding switching transistor
conductive and to each of said ignition signals applied to the
other one of said input circuit means for initiating the operation
of said transistor ignition system to extinguish said ignition coil
primary winding switching transistor.
Description
This invention is directed to an internal combustion engine
electronic ignition spark advance system and, more specifically, to
an electronic ignition spark advance system which provides for both
engine speed and engine vacuum ignition spark advance, as
determined by engine speed.
In conventional ignition systems for internal combustion engines,
the ignition breaker contacts are mounted upon a rotatable breaker
plate. To obtain engine speed ignition spark advance, the breaker
cam is revolved by weights which are rotated by the distributor
shaft and to obtain engine vacuum ignition spark advance, the
breaker plate is revolved by a vacuum motor in response to engine
intake manifold vacuum. As systems of this type are subject to
mechanical wear and failure, the desirability of an electronic
ignition spark advance system which obviates the disadvantage of
mechanical wear and failure is apparent.
It is, therefore, an object of this invention to provide an
improved internal combustion engine ignition spark advance
system.
It is another object of this invention to provide an improved
internal combustion engine ignition spark advance system which
provides ignition spark advance electronically.
It is another object of this invention to provide an improved
electronic ignition spark advance system for internal combustion
engines which electronically provides engine speed and engine
vacuum ignition spark advance.
It is an additional object of this invention to provide an improved
electronic ignition spark advance system for internal combustion
engines which electronically provides engine speed and engine
vacuum ignition spark advance and ignition dwell time to provide
for the energization of the ignition coil primary winding for the
required duration.
In accordance with this invention, an electronic ignition spark
advance system for use with internal combustion engine transistor
ignition systems having an ignition coil primary winding switching
transistor is provided wherein a series of crankshaft position
pulses, each indicating one degree of crankshaft rotation, are
gated through an ignition spark advance gate, enabled in response
to a reference signal produced a selected number degrees before the
top dead center position of each piston, to a counter circuit and
an ignition signal is produced when the counter circuit has counted
the number of crankshaft position pulses equal to the number of
selected degrees the reference signals are produced before top dead
center which extinguishes the ignition coil primary winding
switching transistor and operates circuitry which disenables the
ignition spark advance gate after two consecutive delay periods in
the absence of an engine vacuum spark advance signal produced at
the end of the delay periods for enabling the ignition spark
advance gating circuitry after the delay periods for the number of
crankshaft position pulses which produce the number of degrees of
engine vacuum ignition spark advance required.
For a better understanding of the present invention, together with
additional objects, advantages and features thereof, reference is
made to the following description and accompanying drawings in
which:
FIG. 1 sets forth the electronic ignition spark advance control
system of this invention in block form;
FIG. 2 sets forth the dwell circuit partially in schematic and
partially in block form;
FIG. 3 sets forth in schematic form, circuitry suitable for use
with the electronic ignition spark advance system of this invention
for producing an engine vacuum ignition spark advance signal;
FIG. 4 sets forth a typical engine speed ignition spark advance
curve; and
FIG. 5 sets forth, partially in schematic and partially in block
form, ignition spark advance "cut-in" circuitry suitable for use
with the electronic ignition spark advance system of this
invention;
As the point of reference or ground potential is the same point
electrically throughout the system, it has been represented in the
drawing by the accepted schematic symbol and referenced by the
numeral 5.
The electronic ignition spark advance system of this invention is
designed for use in combination with an internal combustion engine
and an associated transistor ignition system having an ignition
coil primary winding switching transistor. In the interest of
reducing drawing complexity, and since internal combustion engines
are old and well known in the automotive art and, per se, forms no
part of this invention, the engine has not been shown in the
drawing.
One example, and without intention or inference of a limitation
thereto, of an internal combustion engine transistor ignition
system suitable for use with the electronic ignition spark advance
system of this invention is disclosed and described in U.S. Pat.
No. 3,605,713, Sept. 20, 1971, Le Masters et al, which is assigned
to the same assignee as is this application.
The electronic ignition spark advance system of this invention
employs conventional AND gates, NOR gates, bi-stable multivibrator
circuits, monostable multivibrator circuits, differentiating
circuits, counter circuits and an operational amplifier. As these
circuit elements are commercially available items well known in the
art, and per se, form no part of this invention, each has been
illustrated in block form in the drawing. Furthermore, these
devices are only examples of circuit elements suitable for use with
the system of this invention, consequently, there is no intention
or inference of a limitation thereto as other circuit elements
having similar electrical characteristics may be substituted
therefor without departing from the spirit of the invention.
In accordance with logic terminology well known in the art,
throughout this specification, the logic signals will be referred
to as "high" or logic 1 or "low" or logic 0 signals. For purposes
of this specification, and without intention or inference of a
limitation thereto, the "high" or logic 1 signals will be
considered to be of a positive polarity potential and the "low" or
logic 0 signals will be considered to be of zero or ground
potential.
The NOR gates require a logic 0 signal upon all input terminals to
produce a logic 1 output signal and the AND gates require a logic 1
signal upon all input terminals to produce a logic 1 output
signal.
Referring to the drawing, a crankshaft position sensor and a
reference pulse generator are provided for producing a series of
crankshaft position electrical pulses, each corresponding to one
degree of rotation of the engine crankshaft, and a reference
electrical pulse at a predetermined number of degrees before the
top dead center position of each engine piston, respectively. These
items may comprise a circular disc member 2 of magnetic material
having 360 teeth about the periphery, that is, a tooth for each
degree. In the drawing, only a few representative teeth have been
shown in the interest of reducing drawing complexity. Disc member 2
is preferably mounted upon and rotated by the engine crankshaft but
may be mounted upon and rotated by any other engine or vehicle
shaft which is rotated at a speed equal to engine crankshaft speed.
Carried upon and rotated with disc member 2 is a pole piece 3 of
magnetic material having a salient pole tip corresponding to each
two engine cylinders. For an eight cylinder engine, therefore, pole
piece 3 has four salient pole tips 3a, 3b, 3c and 3d, as shown in
FIG. 1. a permanent magnet 4 having a crankshaft position sensor
pickup coil 6 wound thereupon is located in magnetic coupling
relationship with the teeth about the periphery of disc member 2
and another permanent magnet 7 having a reference pulse generator
pickup coil 8 wound thereupon is located in magnetic coupling
relationship with the salient pole tips 3a, 3b, 3c and 3d of pole
piece 3. As disc member 2 and pole piece 3 are rotated at engine
crankshaft speed, therefore, a series of crankshaft position
electrical pulses, each corresponding to one degree of engine
crankshaft rotation and hereinafter referred to as crankshaft
position pulses, are induced in pickup coil 6 and appear upon the
output circuit which may be a terminal 6a and reference electrical
pulses, hereinafter referred to as reference pulses, are induced in
pickup coil 8 and appear upon the output circuit which may be a
terminal 8a. Pole piece 3 is so oriented that, when each salient
pole tip thereof is adjacent permanent magnet 7, the reference
pulse is induced in pickup coil 8 a predetermined number of degrees
before the top dead center position of the engine piston of the
cylinder to which it corresponds. That is, the reference pulse
generator produces a reference pulse at a selected number of
degrees before the top dead center position of each engine piston.
For purposes of this specification, and without intention or
inference of a limitation thereto, the selected number of degrees
before the top dead center position of each engine piston will be
60. It is to be specifically understood that optical sensors or any
other type sensor or any combination thereof may be substituted for
the magnetic crankshaft position sensor and reference pulse
generator without departing from the spirit of the invention.
A counter circuit 10, having an input terminal, a plurality of
output terminals, each corresponding to a binary code bit, and a
reset terminal is provided for counting the crankshaft position
pulses and producing upon the output terminals thereof the binary
code representation of the number of crankshaft position pulses
counted thereby. As counter circuit 10 must count the number of
crankshaft position pulses equal to the number of degrees the
reference pulses are produced before the top dead center position
of each engine piston, 60 for purposes of this specification,
counter 10 must have six stages and six output terminals, 10a, 10b,
10c, 10d, 10e and 10f. A logic 1 signal upon these output terminals
represent the decimal values 1, 2, 4, 8, 16 and 32, respectively,
as is well known in the binary arithmetic art. That is, each output
terminal of counter circuit 10 corresponds to a binary code
bit.
The crankshaft position pulses induced in pickup coil 6 are applied
to counter circuit 10 through an ignition spark advance gate
circuit, NOR gate 12 which, when enabled, gates the crankshaft
position pulses to the input terminal of counter circuit 10. The
ungrounded end of pickup coil 6 is connected to the 12a input
terminal of NOR gate 12 and the output terminal of NOR gate 12 is
connected to the input terminal of counter circuit 10.
as counter circuit 10 must begin counting crankshaft position
pulses upon the occurrence of each reference pulse, NOR gate 12
must be enabled to gate crankshaft position pulses to counter
circuit 10 with each reference pulse. Consequently, circuitry
responsive to each of the reference pulses for producing a start
count signal and a gate circuit for producing an enabling signal in
response to the start count signals for enabling NOR gate 12 are
provided. One example, of a circuit for producing the start count
signals is a conventional bi-stable multivibrator circuit,
illustrated in FIG. 1 in block form and referenced by the numeral
14, having two input terminals 15 and 16 and an output terminal 17.
The enabling gate circuit may be a three input NOR gate 18. To
enable NOR gate 12 to gate crankshaft position pulses to the input
terminal of counter circuit 10, a logic 0 enabling signal must be
present upon the output terminal of enabling NOR gate 18.
Therefore, each reference pulse is applied to input terminal 15 of
bi-stable multivibrator circuit 14 for triggering this device to
the state in which a logic 1 start count signal appears upon output
terminal 17 thereof, which is connected to input terminal 18a of
NOR gate 18. With a logic 1 start count signal present upon the
input terminal 18a of NOR gate 18, a logic 0 enabling signal is
present upon the output terminal thereof which is connected to
input terminal 12b of NOR gate 12, a condition which enables NOR
gate 12.
Circuitry responsive to the binary code representation, upon the
output terminals of counter circuit 10, of the number of crankshaft
position pulses counted by counter circuit 10 equal to the selected
number of degrees before the top dead center position of each
piston of the internal combustion engine at which each reference
pulse is produced for producing an ignition signal is provided.
This circuitry may be an ignition signal AND gate 20 having an
input terminal corresponding to each logic 1 bit of this binary
code representation. As the number of degrees before the top dead
center position of each piston at which each reference pulse is
produced has been arbitrarily selected for purposes of this
specification as 60, a four input ignition signal AND gate 20 is
provided.
When counter circuit 10 has counted 60 crankshaft position pulses,
a logic 1 signal appears upon each of output terminals 10c, 10d,
10e and 10f thereof, the binary code representation of the numeral
60. These counter circuit 10 output terminals are connected to
respective input terminals of ignition signal AND gate 20 which,
with a logic 1 signal present upon each input terminal thereof,
produces a logic 1 output ignition signal upon the output terminal
thereof in response to a counter circuit count of 60 crankshaft
position pulses.
The output terminal of ignition signal AND gate 20 is connected to
the reset terminal of counter circuit 10, to input terminal 16 of
bi-stable multivibrator circuit 14 and to dwell time circuit 25.
Consequently, the logic 1 ignition signal appearing upon the output
terminal of AND gate 20 resets counter circuit 10 to zero, triggers
bi-stable multivibrator circuit 14 to the condition in which a
logic 0 full count signal appears upon output terminal 17 thereof
and operates the dwell circuit 25 to produce a logic 1 output
signal which initiates the operation of the transistor ignition
system 85 to extinguish the ignition coil primary winding switching
transistor, in a manner to be later explained. Bi-stable
multivibrator circuit 14, therefore, is also responsive to each
ignition signal for producing a logic 0 full count signal.
In the absence of any logic 1 signals upon any one of the input
terminals of enabling NOR gate 18 other than the input terminal
connected to the output terminal 17 of bi-stable multi-vibrator 14,
with a logic 0 full count signal present upon output terminal 17 of
bi-stable multivibrator 14, a logic 1 disenabling signal appears
upon the output terminal of enabling NOR gate 18 which is applied
to input terminal 12b of NOR gate 12. While a logic 1 disenabling
signal is applied to input terminal 12b of NOR gate 12, a logic 0
signal is maintained upon the output terminal thereof regardless of
the logic signal applied to the other input terminal 12a.
Consequently, the ignition signal operates circuitry which produces
a full count signal which may disenable NOR gate 12 as bi-stable
multivibrator 14 and NOR gate 18 produce a logic 1 disenabling
signal, in response to each ignition signal, which is applied to
one of the input terminals of NOR gate 12. With these conditions,
each cylinder would be fired when the piston is at top dead center
as the ignition spark advance NOR gate 12 would be enabled by each
reference pulse, produced 60.degree. before top dead center, to
gate crankshaft position pulses to counter circuit 10 and would be
disenabled 60.degree. later in response to the ignition signal
produced by AND gate 20 when counter circuit 10 has counted 60
crankshaft position pulses.
To obtain engine speed ignition spark advance, it is necessary that
delay circuitry responsive to each ignition signal be provided for
producing two consecutive delay periods during which the
disenabling of the ignition spark advance gate is delayed.
Consequently, a first delay circuit responsive to each of the
ignition signals produced by AND gate 20 for producing a first
engine speed ignition spark advance signal of a preselected
duration for delaying the disenabling of the ignition spark advance
NOR gate 12 for the duration thereof and a second delay circuit
responsive to the end of each of the first engine speed ignition
spark advance signals for producing a second engine speed ignition
spark advance signal of a predetermined duration for further
delaying the disenabling of spark advance NOR gate 12 for the
duration thereof are provided. These delay periods permit counter
circuit 10 to continue to count crankshaft position pulses during
the delay periods. The count of crankshaft position pulses during
the delay periods is retained by counter circuit 10. With the next
reference pulse, NOR gate 12 is again enabled to gate crankshaft
position pulses into counter circuit 10. However, as counter
circuit 10 already has a crankshaft position pulse count retained
therein, less than 60 crankshaft position pulses are now required
for the counter circuit 10 to count 60 by an amount equal to the
count retained therein. Consequently, the next ignition signal is
produced by AND gate 20 before the piston of the cylinder to be
fired has reached top dead center by a number of degrees of engine
speed ignition spark advance equal to the count of the crankshaft
position pulses retained in counter circuit 10. For example, if the
count of crankshaft position pulses retained in counter circuit 10
is 20, the engine speed ignition spark advance would be 20.degree..
This delay circuitry may be two conventional monostable
multivibrator circuits, illustrated in block form in FIG. 1 and
referenced by the numerals 21 and 22, each having an input, an
output and a reset terminal. The monostable multivibrator circuit
is normally in the stable state, in which a logic 0 is present upon
the output terminal thereof, and is triggered to the alternate
state, in which a logic 1 signal is present upon the output
terminal thereof, upon the application of a logic 1 signal to the
input terminal thereof. This device remains in the alternate state
for a selectable period of delay time as determined by the timing
circuitry, after which it spontaneously returns to the stable
state. In the alternate state, the output transistor is not
conductive but may be triggered conductive before the expiration of
the selected period of delay time by applying a logic 1 signal to
the base electrode thereof through the reset terminal. The logic 1
ignition signal produced by AND gate 20 is applied to the input
terminal of monostable multivibrator 21, connected to the output
terminal of AND gate 20, which produces the first logic 1 engine
speed ignition spark advance signal. That is, the logic 1 ignition
signal triggers monostable multivibrator 21 to the alternate state
for a delay period as determined by the timing circuitry thereof.
The logic 1 first engine speed ignition spark advance signal
appearing upon the output terminal of monostable multivibrator
circuit 21 while in the alternate state is applied to input
terminal 18b of NOR gate 18, connected to the output terminal of
monostable multivibrator 21, which produces a logic 0 enabling
signal upon the output terminal thereof. At the conclusion of the
delay period designed into monostable multivibrator 21, this device
spontaneously returns to the stable state in which a logic 0 signal
appears upon the output terminal thereof. The trailing edge of the
logic 1 first engine speed ignition spark advance signal present
upon the output terminal of monostable multivibrator 21 while in
the alternate state is differentiated to produce a logic 1 signal
by a conventional differentiating circuit, represented in FIG. 1 in
block form and referenced by the numeral 23. The logic 1 signal
produced by differentiating circuit 23 is applied to the input
terminal of monostable multivibrator circuit 22, connected to the
output terminal of differentiating circuit 23, which produces the
second engine speed ignition spark advance signal. That is, the
logic 1 signal produced by differentiating circuit 23 triggers
monostable multivibrator circuit 22 to the alternate state for a
delay period as determined by the timing circuitry thereof. The
logic 1 second engine speed ignition spark advance signal appearing
upon the output terminal of monostable multivibrator circuit 22
while in the alternate state is also applied to input terminal 18b
of NOR gate 18, connected to the output terminal of monostable
multivibrator circuit 22, which produces a logic 0 enabling signal
upon the output terminal thereof. At the conclusion of the delay
period designed into monostable multivibrator 22, this device
spontaneously returns to the stable state in which a logic 0 signal
appears upon the output terminal thereof.
To provide an engine vacuum ignition spark advance, engine vacuum
sensitive circuitry responsive to the end of the second engine
speed ignition spark advance signal for producing an engine vacuum
ignition spark advance signal is provided. This circuitry may
include a conventional staircase generator 30, FIG. 3, a vacuum
transducer 31 and a potential comparator circuit 32. Upon the
application of a logic 1 signal to the reset terminal 33 of
staircase generator 30, transistor 35 is triggered conductive to
place ground upon the inverting input terminal of operational
amplifier 34, thereby producing a maximum positive polarity
potential signal upon the output terminal thereof, as shown in FIG.
1. Transistor 40 is normally conducting to place substantially
ground potential upon the anode of diode 36. Upon each application
of a logic 1 crankshaft position pulse to input terminal 37 of
staircase generator 30, connected to the ungrounded end of pickup
coil 6 of FIG. 1, transistor 45 conducts to drain base current from
transistor 40 to extinguish this device. Each time transistor 45 is
extinguished by each crankshaft position pulse, a positive polarity
signal is applied to the inverting input terminal of operational
amplifier 34 through diode 36, to reduce the magnitude of the
potential upon the output terminal thereof by increments, as shown
in FIG. 1. That is, the positive polarity potential upon the output
terminal of operational amplifier 34 is stepped down by the
crankshaft position pulses. The vacuum transducer may be a
potentiometer 28 connected across a direct current supply potential
source, not shown. The movable contact 38 thereof is operated by
engine intake manifold vacuum in a manner well known in the
automotive art to produce a potential across the movable contact 38
and ground of a magnitude proportional to engine vacuum. The engine
vacuum transducer potential is applied to the junction between the
emitter electrode of transistor 50 and emitter resistor 51 and the
positive potential upon the output terminal of operational
amplifier 34 is applied to the base electrode of transistor 50.
While the output potential of operational amplifier 34 is of a
positive magnitude greater than the engine vacuum transducer
potential, type NPN transistor 50 and type PNP transistor 55
conduct. While transistor 55 is conductive, a logic 1 engine vacuum
advance signal is present upon the output terminal 41 of potential
comparator circuit 32. When the crankshaft position pulses have
stepped the output potential of operational amplifier 34 to a
magnitude substantially equal to or less than the vacuum transducer
potential, transistors 50 and 55 extinguish. With transistor 55 not
conducting a logic 0 signal is present upon output terminal 41 of
potential comparator circuit 32.
The trailing edge of the logic 1 second engine speed ignition spark
advance signal present upon the output terminal of monostable
multivibrator 22 while in the alternate state is differentiated to
produce a logic 1 signal by a conventional differentiating circuit,
represented in FIG. 1 in block form and referenced by the numeral
24, each time monostable multivibrator 22 returns to the stable
state. The logic 1 second engine speed ignition spark advance
signal produced by differentiating circuit 24 is applied to the
reset terminal 33 of staircase generator 30, connected to the
output terminal of differentiating circuit 24.
To provide two engine speed ignition spark advance limits, first
and second count limit circuits responsive to the binary
representation, upon the output terminals of counter circuit 10, of
a first selected number and a second selected greater number,
respectively, of crankshaft position pulses counted by counter
circuit 10 for producing, respectively, a first engine speed
ignition spark advance limit signal which terminates the first
engine speed ignition spark advance signal if counter circuit 10
counts the first selected number of crankshaft position pulses
prior to the end thereof and a second engine speed ignition spark
advance limit signal which terminates the second engine speed
ignition spark advance signal if counter circuit 10 counts the
second selected greater number of crankshaft position pulses prior
to the end thereof are provided. The output terminals of counter
circuit 10 upon which logic 1 signals representing the first
selected number of crankshaft position pulses and the second
selected greater number of crankshaft position pulses counted by
counter circuit 10 are applied to the input terminals of a first
count limit AND gate 46 and the input terminals of a second count
limit AND gate 47, respectively, each of which produces a logic 1
count limit signal upon the output terminal thereof when counter
circuit 10 has reached the first and second crankshaft position
pulse count limits, respectively. The logic 1 first count limit
signal produced by first count limit AND gate 46 is applied to the
reset terminal of monostable multivibrator circuit 21, connected to
the output terminal of first count limit AND gate 46, and the logic
1 second count limit signal produced by second count limit AND gate
47 is applied to the reset terminal of monostable multivibrator
circuit 22, connected to the output terminal of second count limit
AND gate 47.
Just prior to each reference pulse, a logic 0 full count signal is
present upon output terminal 17 of bi-stable multi-vibrator 14, and
a logic 0 signal is present upon the output terminal of each of
monostable multivibrator circuits 21 and 22 and voltage comparator
circuit 32. Consequently, a logic 1 disenabling signal is present
upon the output terminal of NOR gate 18 to disenable NOR gate
12.
Upon the occurrence of a reference pulse, bi-stable multivibrator
circuit 14 is triggered to the state in which a logic 1 start count
signal is present upon the output terminal 17 thereof, applied to
input terminal 18a of NOR gate 18, and a logic 0 signal is present
upon the output terminals of monostable multivibrator circuits 21
and 22 and potential comparator circuit 32. The logic 1 start count
signal upon input terminal 18a of NOR gate 18 produces a logic 0
enabling signal upon the output terminal thereof which is applied
to input terminal 12b of NOR gate 12 to enable this device to gate
crankshaft position pulses to the input terminal of counter circuit
10, consequently counter circuit 10 counts these pulses.
Upon a count of 60 crankshaft position pulses, AND gate 20 produces
a logic 1 ignition signal pulse which resets counter circuit 10,
initiates the operation of the transistor ignition system 85 to
extinguish the ignition coil primary winding switching transistor
in a manner to be later explained, triggers bi-stable multivibrator
14 to the state in which a logic 0 full count signal is present
upon output terminal 17 thereof and triggers monostable
multivibrator 21 to the alternate state in which a logic 1 first
engine speed ignition spark advance signal is present upon the
output terminal thereof which is applied to input terminal 18b of
NOR gate 18. The logic 1 first engine speed ignition spark advance
signal upon input terminal 18b of NOR gate 18 produces a logic 0
enabling signal upon the output terminal thereof which enables NOR
gate 12 to continue to gate crankshaft position pulses to the input
terminal of counter circuit 10, consequently, counter circuit 10
counts these pulses.
At the conclusion of the first delay period, unless earlier
terminated by first count limit AND gate 46, monostable
multivibrator circuit 21 reverts to the stable state in which a
logic 0 signal is present upon the output terminal thereof and
monostable multivibrator circuit 22 is triggered to the alternate
state in which a logic 1 second engine speed ignition spark advance
signal is present upon the output terminal thereof which is applied
to input terminal 18b of NOR gate 18. This logic 1 second engine
speed ignition spark advance signal upon input terminal 18b of NOR
gate produces a logic 0 enabling signal upon the output terminal
thereof which enables NOR gate 12 to continue to gate crankshaft
position pulses to the input terminal of counter circuit 10,
consequently counter circuit 10 counts these pulses.
At the conclusion of the second delay period, unless earlier
terminated by second count limit AND gate 47, monostable
multivibrator circuit 22 reverts to the stable state in which a
logic 0 signal is present upon the output terminal thereof and the
trailing edge of the logic 1 signal is differentiated by
differentiator circuit 24 to produce a logic 1 signal which is
applied to the reset terminal of staircase generator 30. This logic
1 signal resets the output potential of operational amplifier 34 to
a high positive magnitude, consequently, potential comparator
circuit 32 produces a logic 1 engine vacuum ignition spark advance
signal which is applied to input terminal 18c of NOR gate 18. This
logic 1 engine vacuum ignition spark advance signal upon input
terminal 18c of NOR gate 18 produces a logic 0 enabling signal upon
the output terminal thereof which enables NOR gate 12 to continue
to gate crankshaft position pulses to the input terminal of counter
circuit 10, consequently, counter circuit 10 counts these
pulses.
Each crankshaft position pulse applied to input terminal 37 of
staircase generator 30 steps the output potential of operational
amplifier 34 lower until it is of a magnitude equal to the output
potential of vacuum transducer 31. At this time transistors 50 and
55 extinguish to place a logic 0 signal upon output terminal 41 of
potential comparator circuit 32 which is applied to input terminal
18c of NOR gate 18, FIG. 1. This logic 0 signal upon input terminal
18c of NOR gate 18, along with the logic 0 signals present upon
input terminal 18a from output terminal 17 of bi-stable
multivibrator 14 and upon input terminal 18b from the output
terminals of monostable multivibrator circuits 21 and 22 produces a
logic 1 disenabling signal upon the output terminal thereof which
disenables NOR gate 12, consequently, NOR gate 12 gates no more
crankshaft position pulses to the input terminal of counter circuit
10.
From this description, it is apparent that the enabling gate
circuit, NOR gate 18, is responsive to the start count signals, the
first and second engine speed ignition spark advance signals and
the engine vacuum ignition spark advance signals for producing an
enabling signal for the ignition spark advance gate circuit, NOR
gate 12, and to the full count signals for producing a disenabling
signal for the ignition spark advance NOR gate 12 in the absence of
the first and second engine speed ignition spark advance signals
and the engine vacuum ignition spark advance signals.
The crankshaft position pulses counted by counter circuit 10 during
both delay periods and the period of the logic 1 engine vacuum
spark advance signal is retained by counter circuit 10 until the
next reference pulse and this number of crankshaft position pulses
is the number of degrees of ignition spark advance.
For proper operation of a transistor ignition system, it is
necessary that the ignition coil primary winding switching
transistor be turned "on" for a sufficient dwell time period in
advance of the ignition signal to provide for sufficient
energization of the ignition coil primary winding to produce the
required high energy ignition potential.
Consequently, dwell circuitry responsive to a preselected number of
crankshaft position pulses for initiating the operation of the
associated transistor ignition system to trigger the ignition coil
primary winding switching transistor conductive prior to the
ignition signal and to each of the ignition signals for initiating
the operation of the associated transistor ignition system to
extinguish the ignition coil primary winding switching transistor
is provided.
In FIG. 2, an electronic dwell time circuit which anticipates the
next ignition signal and initiates the operation of the transistor
ignition system 85 to trigger the ignition coil primary winding
switching transistor to conduction before the next ignition signal,
suitable for use with the electronic ignition spark advance circuit
of this invention, is set forth in schematic form. Between each
ignition signal at any engine speed, there are ninety degrees of
engine crankshaft rotation. Therefore, the crankshaft position
pulses are counted by a conventional dwell time counter circuit 60
having an input terminal and a plurality of output terminals, each
corresponding to a binary code bit, as explained in regard to
counter circuit 10. As dwell time counter circuit 60 may be
required to count as many as eighty-eight crankshaft position
pulses, it must have seven stages and seven output terminals 60a,
60b, 600c, 60d, 60e 60f and 60g. For purposes of this
specification, it will be assumed that dwell time counter circuit
60 counts 80 crankshaft position pulses between ignition signals,
consequently, output terminals 60e and 60g thereof, a logic 1
signal on both indicating in binary form the numeral 80, are
connected to respective input terminals of AND gate 62. At a
crankshaft position pulse count of 80, there are 10.degree. of
engine crankshaft rotation remaining before the next ignition
signal. To insure that at least the minimum dwell time is obtained
before each ignition signal, a predetermined minimum dwell time is
provided by a conventional monostable multivibrator 65, for example
2.0 milliseconds.
With monostable multivibrator 65 in the stable state transistor 66
is not conducting, transistor 67 is conducting and transistor 68 is
conducting. Upon the application of a logic 1 ignition signal to
input terminal 70b of NOR gate 70 through input terminal 71(2),
connected to the output terminal of the ignition signal AND gate 20
of FIG. 1 through point 71(1), a logic 0 signal is produced upon
the output terminal thereof. With a logic 0 signal upon the output
terminal of NOR gate 70 and transistor 67 conducting, a logic 0
signal is applied to input terminals 72a and 72b of NOR gate 72,
connected to the output terminals of monostable multivibrator
circuit 65 and NOR gate 70, respectively, a condition which
produces a logic 1 signal upon the output terminal thereof which
triggers transistor 73 conductive. With transistor 73 conducting,
base current is drained from transistor 75 of the ignition circuit
85, FIG. 1, through diode 76 and the collector-emitter electrodes
of conducting transistor 73, connected to diode 76 through terminal
74, to extinguish transistor 75. With transistor 75 extinguished,
base current is supplied to transistor 77, consequently, transistor
77 conducts through the collector-emitter electrodes. Conducting
transistor 77 drains base current from transistor 78 to extinguish
transistor 78. With transistor 78 extinguished, base drive current
is not supplied through the collector-emitter electrodes thereof to
the base electrode of ignition coil primary winding switching
transistor 80, consequently, this device extinguishes to interrupt
the energizing circuit for ignition coil primary winding 81. The
resulting ignition coil primary winding collapsing magnetic field
induces a high energy ignition potential in ignition coil secondary
winding 82 which is directed to the spark plug of the engine
cylinder to be fired through the ignition distributor, not shown,
in a manner well known in the automotive art.
The logic 0 signal upon the output terminal of NOR gate 70 is also
applied to input terminal 86a of NOR gate 86, connected to the
output terminal of NOR gate 70, to enable NOR gate 86 to gate
crankshaft position pulses, applied to input terminal 86b thereof
through terminal 39(2) connected to terminal 39(1) of FIG. 1, to
the input terminal of dwell time counter circuit 60.
Upon a count of 80 crankshaft position pulses by dwell time counter
circuit 60, a logic 1 signal appears upon each of output terminals
60e and 60g thereof. These logic 1 signals are applied to
respective input terminals of AND gate 62 to produce a logic 1
signal upon the output terminal thereof. This logic 1 signal is
applied to the reset terminal of dwell time counter circuit 60 and
to the input terminal 63 of monostable multivibrator 65, both
connected to the output terminal of AND gate 62, to reset dwell
time counter circuit 60 to zero and to trigger monostable
multivibrator circuit 65 to the alternate state.
With monostable multivibrator circuit 65 in the alternate state,
transistors 66 and 68 are conductive and transistor 67 is not
conductive. With transistor 67 not conducting, a logic 1 signal is
present upon the output terminal 64 of monostable multivibrator 65
which is applied to input terminal 72a of NOR gate 72, connected to
the output terminal 64 of monostable multivibrator 65, to produce a
logic 0 signal upon the output terminal thereof. This logic 0
signal is applied to the base electrode of transistor 73, connected
to the output terminal of NOR gate 72, to extinguish transistor 73.
With transistor 73 extinguished, a positive potential is present
upon output terminal 74 which reverse biases diode 76 of the
ignition circuit, FIG. 1. With diode 76 reverse biased, base
current is supplied to transistor 75, consequently, transistor 75
conducts through the collector-emitter electrodes. Conducting
transistor 75 drains base current from transistor 77 to extinguish
this device. With transistor 77 extinguished, base current is
supplied to transistor 78, consequently, transistor 78 supplies
through the collector-emitter electrodes. Conducting transistor 78
supplied base current to ignition coil primary winding switching
transistor 80, consequently, this device conducts through the
collector-emitter electrodes to complete the energizing circuit for
ignition coil primary winding 81.
At the conclusion of the designed delay period of monostable
multivibrator 65, for example 2.0 milliseconds, this device reverts
to the stable state with transistor 67 conducting. Upon the
conduction of transistor 67 after the delay period, the base
electrode of transistor 68 is substantially grounded through
capacitor 83 to extinguish transistor 68 until capacitor 83 has
become charged. While transistor 68 is extinguished, a logic 1
signal is applied to input terminal 87a of NOR gate 87, connected
to the collector electrode of transistor 68, to produce a logic 0
signal upon the output terminal thereof. This logic 0 signal is
applied to input terminal 70a of NOR gate 70, connected to the
output terminal of NOR gate 87, and the logic 0 signal present upon
the output terminal of the ignition signal AND gate 20, FIG. 1, is
applied to input terminal 70b of NOR gate 70 through terminals
71(1) of FIG. 1 and 71(2) of FIG. 2 to produce a logic 1 signal
upon the output terminal thereof which is applied to input terminal
72b of NOR gate 72 and input terminal 86a of NOR gate 86. This
logic 1 signal maintains a logic 0 signal upon the output terminal
of NOR gate 72 and produces a logic 0 signal upon the output
terminal of NOR gate 86 to disenable NOR gate 86. Consequently, the
ignition coil primary winding switching transistor 80 of FIG. 1
remains conductive and NOR gate 86 gates no more crankshaft
position pulses to dwell time counter circuit 60.
Upon the occurrence of the next logic 1 ignition signal ten degrees
later, the sequence of events hereinabove described are repeated to
extinguish the ignition coil primary winding switching transistor
80 of FIG. 1 to produce a high energy ignition potential to fire
the next spark plug and start the next counting sequence to
energize the coil to provide sufficient dwell time. This circuit
functions to energize the coil 10.degree. in advance of the
crankshaft position at which there is a minimum of 2.0 milliseconds
before the next ignition signal. Thus this dwell time circuit
produces a dwell time of 3.66 milliseconds at an engine speed of
1000 RPM and a dwell time of 2.27 milliseconds at an engine speed
of 6000 RPM.
The operation of first and second count limit AND gates 46 and 47
to terminate the respective first and second delay periods early
does not alter the operation of the electronic ignition spark
advance circuit as hereinabove described. These devices establish
the ignition spark advance curve over a range of engine speeds from
zero to maximum in a manner now to be explained.
A typical internal combustion ignition spark advance curve is set
forth in FIG. 4. For purposes of this specification and without
intention or inference of a limitation thereto, it will be assumed
that the internal combustion engine with which the electronic
ignition spark advance system of this invention is to be used
requires an ignition spark advance of 18.degree. at an engine speed
of 750 RPM, 36.degree. at engine speeds of 3000 RPM and higher and
a first limit of 24.degree. ignition spark advance at an engine
speed of 1000 RPM. To produce 18.degree. ignition spark advance at
an engine speed of 750 RPM, the total of the first and second delay
periods must be 18.degree. divided by 4.5.degree. per millisecond
which is 4 milliseconds. The points 18.degree. at 750 RPM,
24.degree. at 1000 RPM and 36.degree. at 3000 RPM are plotted. A
straight line is drawn through the 36.degree. and 24.degree. points
to the vertical axis and another straight line originating at zero
is drawn through the 18.degree. and 24.degree. points. The point at
which the first line intersects the vertical axis indicates the
first count limit, in this case 18. With a first count limit of 18,
to obtain 24.degree. ignition spark advance at an engine speed of
1000 RPM, the first count limit, 6.degree. more advance is
required. To count 6.degree. at 1000 RPM requires 6.degree. divided
by 6.degree. per millisecond or 1 millisecond. This is the second
delay period to be produced by monostable multivibrator circuit 22.
Therefore, the first delay period is the total delay of 4
milliseconds minus the first delay period of 1 millisecond or 3
milliseconds. This is the delay period produced by monostable
multivibrator circuit 21. The second count limit is 36 as no more
ignition spark advance is required at engine speeds of 3000 RPM and
higher. Consequently, upon the count of 36 crankshaft position
pulses by counter circuit 10, second count limit AND gate 47
terminates the second delay period, a condition which disenables
ignition spark advance NOR gate 12. Therefore, at engine speeds of
3000 RPM and higher, counter circuit 10 counts a maximum of 36
crankshaft position pulses which results in a maximum ignition
spark advance of 36.degree..
In the event it is desired that ignition spark advance begin at a
selected engine speed greater than zero, a "cut-in" circuit may be
employed. A "cut-in" circuit suitable for use with the circuit of
this invention is set forth in schematic form in FIG. 5. This
circuit operates to disenable ignition spark advance NOR gate 12
during a portion of the delay periods to reduce the number of
crankshaft position pulses counted during the delay periods. The
collector electrode of transistor 90 is connected to junction 91 of
FIG. 1 to place a logic 0 signal upon input terminal 18b of NOR
gate 18 while conducting during the delay periods. This results in
a logic 1 signal upon the output terminal of NOR gate 18 which
disenables the ignition spark advance NOR gate 12. Each logic 1
ignition signal produced by AND gate 20, FIG. 1, is applied to
input terminal 92 of a conventional bistable multivibrator circuit
95, connected to the output terminal of AND gate 20 through
terminals 71(5) of FIG. 5 and 71(1) of FIG. 1, to trigger bi-stable
multivibrator 95 to the state in which a logic 1 signal is present
upon output terminal 94 thereof. This logic 1 signal is applied to
the base electrode of transistor 90, connected to output terminal
94, to trigger transistor 90 conductive. Conducting transistor 90
applies a logic 0 signal to input terminal 18b of NOR gate 18 which
results in a logic 1 signal upon the output terminal thereof. This
logic 1 signal disenables ignition spark advance NOR gate 12,
consequently, counter circuit 10 does not count crankshaft position
pulses while transistor 90 is conducting. Crankshaft position
pulses are counted by conventional "cut-in" counter circuit 96,
being applied to the input terminal thereof through terminals 39(5)
of FIG. 5 and 39(1) of FIG. 1. When "cut-in" counter circuit 96 has
counted the number of crankshaft position pulses which will result
in the beginning of ignition spark advance at the selected engine
speed greater than zero, AND gate 97 produces a logic 1 output
signal which is applied to input terminal 93 of bi-stable
multivibrator 95, connected to the output terminal of AND gate 97.
This logic 1 signal triggers bi-stable multivibrator circuit 95 to
the condition in which a logic 0 signal is present upon output
terminal 94 thereof. This logic 0 signal extinguishes transistor
90. Consequently, counter circuit 10 counts crankshaft position
pulses for the remainder of the delay periods.
Although specific logic circuit devices and circuit elements have
been set forth in this specification, it is to be specifically
understood that alternate logic elements and circuit elements
having similar electrical characteristics may be substituted
therefor.
While a preferred embodiment of the present invention has been
disclosed and described, it will be obvious to those skilled in the
art that various modifications and substitutions may be made
without departing from the spirit of the invention which is to be
limited only within the scope of the appended claims.
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