U.S. patent number RE31,709 [Application Number 06/168,624] was granted by the patent office on 1984-10-23 for ignition systems for internal combustion engines.
This patent grant is currently assigned to Lumenition Limited. Invention is credited to Eric H. Ford.
United States Patent |
RE31,709 |
Ford |
October 23, 1984 |
**Please see images for:
( Certificate of Correction ) ** |
Ignition systems for internal combustion engines
Abstract
The advance and retard of the spark ignition in an ignition
system of an internal combustion engine is achieved electronically
by generating two series of pulses in synchronism with the engine
using one series as a reference for maximum advance and the other
series to operate a counter to count down the requisite number of
pulses beyond the maximum advance point before the spark is
initiated, the count of the counter being varied from a computer in
accordance with speed and/or load on the engine.
Inventors: |
Ford; Eric H. (London,
GB2) |
Assignee: |
Lumenition Limited (London,
GB2)
|
Family
ID: |
26237431 |
Appl.
No.: |
06/168,624 |
Filed: |
September 18, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
321660 |
Jan 8, 1973 |
03981282 |
Sep 21, 1976 |
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Current U.S.
Class: |
123/406.63;
123/613 |
Current CPC
Class: |
F02P
5/15 (20130101); F02P 7/073 (20130101); F02P
3/0554 (20130101); F02D 41/009 (20130101); F02P
5/1502 (20130101); Y02T 10/40 (20130101); Y02T
10/46 (20130101) |
Current International
Class: |
F02P
3/02 (20060101); F02P 3/055 (20060101); F02P
7/00 (20060101); F02P 7/073 (20060101); F02P
5/15 (20060101); F02D 41/34 (20060101); F02P
005/04 () |
Field of
Search: |
;123/486,487,415,416,613,477 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cox; Ronald B.
Attorney, Agent or Firm: Michael, Best & Friedrich
Claims
What I claim and desire to secure by Letters Patent is:
1. An electronic device for controlling the advance and retard of
the ignition timing of an internal combustion engine in accordance
with engine requirements, including means for generating a first
series of square-wave voltage pulses in synchronism with the engine
revolutions to provide a series of alternate first and second
voltage levels; means for generating a second series of square-wave
voltage pulses also in synchronism with the engine revolutions and
at a fixed multiple of the first series of square-wave voltage
pulses, so that the frequency of the second series of voltage
pulses is greatly in excess of the frequency of the first series of
voltage pulses; means for counting a .Iadd.predetermined
.Iaddend.number of the second series of voltage pulses from a
.[.predetermined.]. point .[.in relation to the first series of
voltage pulses,.]. .Iadd.at which the logic level of the first
series of pulses changes to the first voltage level.Iaddend., the
number of said pulses counted depending on the engine requirements;
means for producing an output at the first voltage level from said
counting means after said count has been completed; means for
detecting the presence of both an output at the first voltage level
from the first pulse generating means.[.,.]. and an output at the
first level from the counting means .[.in order to initiate.].
.Iadd.and, upon such occurrence, initiating .Iaddend.the production
of a spark .Iadd.and causing spark duration to begin .Iaddend.for
the combustion of the fuel, .Iadd.the outputs from both the
counting means and the first pulse generating means remaining at
the first voltage level until the logic level of the first pulse
generating means changes to a second voltage level at a given
engine crankshaft position and causes termination of spark
duration.Iaddend.; and means for continuously varying the count of
the counting means, so as to advance and retard the ignition timing
in accordance with the requirements of the engine.
2. An electronic device according to claim 1, including an ignition
coil having primary and secondary windings, wherein the counting
means starts to count from a position equivalent to the maximum
advance for any given running condition of the engine, a high
voltage level output from the first pulse generating means,
representing said first voltage level, initiating the start of the
count, the counting means then counting down the predetermined
number set therein before giving a high voltage level output, which
together with the high voltage level output of the first pulse
generating means, causes the de-energization of the primary winding
of the ignition coil in order to induce a voltage in the secondary
winding of the ignition coil sufficient to produce a spark.
3. An electronic device according to claim 1, wherein the counting
means is a frequency divider.
4. An electronic device according to claim 3, wherein the means for
varying the count of the frequency divider is a computer whose
digital output is modified in accordance with digital information
fed thereto as regards the speed and load conditions on the
engine.
5. An electronic device according to claim 1, wherein the first and
second series of generated pulses are each applied to respective
trigger circuits, each trigger circuit comprising a plurality of
cascaded transistors arranged to switch in inverse relation to one
another so that at any one time one transistor is fully saturated
while the immediately neighboring transistors are fully cut
off.
6. An electronic device according to claim 1, including a power
transistor stage; and a pre-amplifier stage the pre-amplifier stage
being arranged to be turned on only in the presence of both a high
voltage level pulse from the first pulse generating means and a
high voltage level pulse from the counting means, the transistors
of the pre-amplifier stage and the power transistor stage switching
in inverse relation to one another.
7. An electronic device according to claim 6, wherein the power
transistor stage comprises a darlington pair having a commoned
collector electrode, a zener diode and series resistor being
connected between the commoned collectors and the base electrode of
the first transistor of the pair, the collector electrode of the
transistor of the pre-amplifier stage being connected to the base
electrode of the first transistor of the darlington pair by way of
a diode.
8. An electronic device according to claim 1, including: an opaque
disc driven in synchronism with the engine; 68 equi-spaced slits
around the disc near the periphery thereof; n equi-spaced apertures
near the center of the disc, where n is related to the number of
cylinders in the engine; a pair of infra-red sources positioned on
one side of the disc, in line with the slits and apertures; a pair
of infra-red detectors positioned on the other side of the disc for
generating said first and second square-wave voltage pulses as
"high" and "lows" representing the first and second voltage levels
respectively, the count of the counting means commencing at the
instant that the infra-red radiation is cut off from the first
detector.
9. An electronic device for controlling the advance and retard of
the ignition timing of an n cylinder internal combustion engine,
having an ignition coil with primary and secondary windings, said
device including an opaque disc driven in synchronism with the
engine; a series of equi-spaced slits around the disc; n
equi-spaced apertures in the disc; a pair of infra-red radiation
sources and a pair of infra-red radiation detectors arranged on
opposite sides of the disc, .[.the.]. .Iadd.a .Iaddend.first
element of each pair being arranged to cooperate with said n
apertures and .[.the.]. .Iadd.a .Iaddend.second element of each
pair .Iadd. being arranged to cooperate .Iaddend.with the slits,
.[.one.]. .Iadd.a first one of said .Iaddend.infra-red
.[.detector.]. .Iadd.detectors .Iaddend.generating a first series
of square-wave voltage pulses in synchronism with the engine
revolutions, to provide a series of alternate first and second
voltage levels; .[.the other.]. .Iadd.a second one of said
.Iaddend.infra-red .[.detector.]. .Iadd.detectors
.Iaddend.generating a second series of square-wave voltage pulses
also in synchronism with the engine revolutions, and at a fixed
multiple of the first series of square-wave voltage pulses, so that
the frequency of the second series of voltage pulses is greatly in
excess of the first series; a .[.frequency divider circuit.].
.Iadd.counter .Iaddend.for counting .[.the pulses generated from
the second infra-red detector at a starting point determined when
said respective first series of pulses change from the second to
the first voltage level.]. .Iadd.a predetermined number of the
second series of voltage pulses from a point at which the logic
level .Iadd.of the first series of voltage pulses changes to the
first voltage level, the number of said pulses counted depending on
engine requirements; means for producing an output at the first
voltage level from said counter after said count has been
completed.Iaddend.; a computer connected to receive .[.analogue.].
.Iadd.analog .Iaddend.information from a pair of inputs regarding
the requirements of the engine, and providing a corresponding
digital output, in accordance with that information for changing
the count of the .[.frequency divider, the frequency divider
producing an output after the predetermined count.]. .Iadd.counter;
logic circuitry for detecting the presence of both an output at the
first voltage level from the first detector and an output at the
first voltage level from said counter.Iaddend.; a transistorized
power stage in series with the primary winding of the ignition
coil, the power stage being rendered non-conductive .[.at the
instant when there is a first voltage level output from the
frequency divider and the first detector thereby initiating the
spark for ignition, the advance and retard of the ignition timing
being continuously adjusted in accordance with engine
requirements.]. .Iadd.in response to the logic circuitry detecting
the presence of both outputs and thereby initiating the production
of a spark and causing spark duration to begin for the combustion
of the fuel, the outputs from both said counter and the first
detector remaining at the first voltage level until the logic level
of the first detector changes to a second voltage level at a given
engine crankshaft position.Iaddend..
10. An electronic device according to claim 9, wherein the computer
has four outputs which are connected to four inputs of the
frequency divider circuit, the outputs from the computer
representing either a 1 or a 0, whereby a digital count of sixteen
can be fed into the frequency divider, in accordance with binary
notation, said computer providing a digital output to the frequency
divider in accordance with information fed thereto regarding the
engine requirements, and digital output being continuously modified
as these engine conditions change, so that the ignition timing is
appropriately controlled in sixteen steps between maximum and
minimum advance requirements.
Description
The present invention relates to .[.both.]. spark ignition systems
for internal combustion engines.
One such spark ignition system is disclosed in my Pat. No.
3,605,712. This prior art system employs the principle of fast
inverse switching a signal produced by a beam of infra-red
radiation which is chopped in synchronism with the engine
revolutions. The advance and retard of the spark was achieved by
utilizing the vacuum principle in accordance with speed or load.
This known method of achieving accurate control of the spark
ignition timing relied on mechanical devices such as spring biased
diaphragms, and whilst perfectly satisfactory they are liable to
failure or misadjustment.
It is therefore an object of the present invention to utilize an
electronic system for the control of the ignition system of an
internal combustion engine in accordance with engine requirements,
whereby the ignition system is substantially free from mechanical
defects.
According to the present invention there is provided an electronic
device for controlling the advance and retard of the ignition
timing of an internal combustion engine in accordance with engine
requirements, including means for generating a first series of
square-wave voltage pulses in synchronism with the engine
revolutions, to provide a series of alternate first and second
voltage levels; means for generating a second series of square-wave
voltage pulses also in synchronism with the engine revolutions and
at a fixed multiple of the first series of square-wave voltage
pulses, so that the frequency of the second series of voltage
pulses is greatly in excess of the frequency of the first series of
voltage pulses; means for counting a number of the second series of
voltage pulses from a predetermined point in relation to the first
series of voltage pulses, the number of said pulses counted
depending on the engine requirements; means for producing an output
at the first voltage level from said counting means after said
count has been completed; means for detecting the presence of both
an output at the first voltage level from the first pulse
generating means, and an output at the first level from the
counting means in order to imitate the production of a spark for
the combustion of the fuel; and means for continuously varying the
count of the counting means, so as to advance and retard the
ignition timing in accordance with the requirements of the
engine.
The counting means is preferably a frequency divider.
Preferably, the means for varying the count of the frequency
divider is a computer whose digital output is modified in
accordance with digital information fed into it as regards the
speed and/or load conditions on the engine.
The first and second series of generated pulses may be fast
switched and current amplified by a trigger circuit comprising a
plurality of cascaded transistors arranged to switch in inverse
relation to one another so that at any one time at least one
transistor is always fully saturated whilst its immediate
neighbours are hard off.
The outputs from the first trigger and the counting means
preferably operate a power transistor stage with one or more
pre-amplifying stages to effect the production of the spark by
interrupting the current through the primary winding of the
ignition coil or delivering the desired quantity of fuel by
energizing the solenoid of the fuel injector.
The power transistor stage may consist of a darlington pair having
a commoned collector electrode, a zener diode and series resistor
being connected between the commoned collectors and the base
electrode of the first transistor of the pair. The collector
electrode of the last transistor of the trigger is preferably
connected to the base electrode of the first transistor of the
darlington pair by way of a diode and iron cored inductor connected
in series, the function of the latter being to slow down the
switching rate of the darlington pair.
The present invention will now be described in greater detail by
way of example with reference to the accompanying drawings,
wherein:
FIG. 1 is a diagram (partly in block form) of one form of advance
and retard device for use with a spark ignition system of an
internal combustion engine;
FIG. 2 is a front view of the disc shown in FIG. 1;
FIG. 3 is a detailed circuit diagram of the electronic advance and
retard device shown in FIG. 1;
FIG. 4 is a first modified circuit arrangement of the
photo-transistor of FIG. 3;
FIG. 5 is a second modified circuit arrangement of the
photo-transistor of FIG. 3;
FIG. 6 is a set of waveforms which assist in explaining the
operation of the circuit shown in FIG. 3;
In the example relating to a spark ignition system for a four
cylinder internal combustion engine shown in FIGS. 1 to 3, the
device for achieving the electronic advance and retard of the
timing of the spark, includes a radiation chopper device generally
designated 1; a first fast inverse switching trigger circuit 11; a
second fast inverse switching trigger circuit 12; a frequency
divider 14; a computer 16; and an amplifier and power transistor
stage 18.
The radiation chopper device 1 consists of a housing 2; a disc 3; a
shaft 4 carrying the disc 3; infra-red radiation sources 5 and 6;
and radiation detectors 7 and 8. The infra-red radiation sources 5
and 6 are preferably gallium arsenide lamps and the radiation
detectors are preferably photo-transistors, all these elements
being fixed to the housing 2. The shaft 4 is journalled in bearings
(not shown) in the housing 2 and is driven at cam shaft speed of
the engine.
The chopper disc 3 comprises two series of concentric apertures 9
and 10. There are four large apertures 9 in equi-spaced relation
and a large number of small apertures or slits 10 (e.g. sixty
eight). The apertures 9 permit infrared-red radiation for the lamp
5 to reach the phototransistor 7, and the slits 10 permit infra-red
radiation from the lamp 6 to reach the phototransistor 8. The lamps
5 and 6 are energized through a common stabilized voltage source
20.
The output from the respective phototransistors 7 and 8 is fed to
the inputs of respective fast inverse switching triggers 11 and 12.
The output of the second trigger 12 is fed to the frequency divider
14 which normally gives a 0 output, but which on completion of the
count down set into it from the computer 16 gives a 1 output. The
count set into the frequency divider 14 is controlled from the
computer 16 by means of four output lines 22a to 22d, each of which
is either at a high level of voltage to represent a 1 or a low
level of voltage to represent a 0 in accordance with the binary
notation. The computer 16 receives at two inputs 24a and 24b
information in digital form concerning the speed and load on the
engine, this information being obtained from any known analogue
type of measuring device and then converted into digital form so
that the computer can calculate the count down necessary before the
frequency divider 14 will give a 1 output so as to obtain the
correct advance or retard of the ignition timing. In this example,
the computer has a maximum count of sixteen. The amplifier and
power transistor stage 18 controls the current flow through the
primary winding of the ignition coil 26. When the outputs from the
stages 11 and 14 are either 0 and 1 or 1 and 0 or 0 and 0 current
flows through the primary winding of the ignition coil 26, but when
both outputs are at the high level 1, then the current through the
coil is interrupted, producing the collapse of the magnetic field
and the resultant high secondary voltage necessary for the
spark.
Referring now to FIG. 3, the first and second triggers 11 and 12
respectively include first transistors 30a and 30b, second
transistors 32a and 32b, first collector load resistors 34a and
34b, second collector load resistors 36a and 36b, and feedback
resistors 38a and 38b. The first and second transistors of each
trigger are connected in cascade to switch in inverse relation to
one another, so that when one is fully saturated (ON) the other is
fully non-conductive (OFF). Also the output from the
photo-transistors 7 and 8 is connected to the base electrodes of
the respective first transistors 30a and 30b such that when the
photo-transistors conduct, the first transistors switch off and
vice versa. Respective diodes 40a and 40b are connected across the
collector-emitter electrodes of the photo-transistors 7 and 8 to
ensure clean switching of these elements.
The gallium arsenide lamps 5 and 6 are connected in series with
respective resistors 42a and 42b and connected in parallel with one
another across the +12 volt battery supply through a resistor 43. A
zener diode 44 is connected across the paralleled gallium arsenide
lamps 5 and 6 in order to provide a stabilized voltage. The voltage
across the photo-transistors 7 and 8 is also stabilized by means of
the zener diode 44 the photo-transistors being connected in series
with respective resistors 46a and 46b.
The output from the collector electrode of the transistor 32a of
the first trigger 11 is applied direct to the base electrode of a
transistor 50 constituting the amplifier stage of the power
transistor stage 18 and also to the set/reset input of the
frequency divider 14. The output from the collector electrode of
the transistor 32b of the second trigger 12 is applied indirectly
to the base electrode of the transistor 50 through the frequency
divider 14. The transistor 50 will conduct only if the outputs from
the stages 11 and 14 are at the high level representing a 1. This
transistor is thus normally "off" under all the three conditions
except the double high when it becomes fully saturated. A resistor
52 is provided in series with its collector electrode.
The power transistor 18 also includes two power-transistors 54 and
56 connected as a Darlington pair; diodes 58, 60 and 62; a zener
diode 64; resistors 66, 68 and 70. The power transistors 54 and 56
are fully protected by means of the zener diode 64 and the diode
62. The zener diode is arranged to conduct above a certain voltage
level so that if there are any positive going transients induced in
the circuit when the Darlington pair has switched off, these break
down the zener diode 64 which conducts them through the resistor 66
to the base electrode of the power transistor 54. The Darlington
pair is thus caused to turn on in a controlled manner for the
duration of these transients so that there is no risk of either of
the components of the Darlington pair being broken down in the
event of high positive going voltage surges. Negative going
transients which occur when the Darlington pair is switched off are
conducted on earth via the diode 62. The purpose of the diode 58 is
to prevent the voltage passed by the zener diode 64 from flowing to
earth via the transistor 50.
The secondary winding of the ignition coil is connected to the
spark plugs 72a to 72d via a distributor 74 in conventional
manner.
Instead of using a single photo-transistor 7 and 8, a Darlington
pair may be used instead for both the elements 7 and 8. Two
alternative circuit arrngements are illustrated in FIGS. 4 and 5.
The circuit shown in both alternatives includes a Darlington pair
comprising a photo-transistor 76 and an NPN transistor 78, the
emitter electrode of the photo-transistor 76 being connected to the
base electrode of the transistor 78. In each case the diode 40 is
connected in parallel with the collector-emitter path of the
transistor 78. In the first alternative form shown in FIG. 4, the
emitter electrode of the photo-transistor 76 is connected to earth
via a resistor 80, whereas in the second alternative form shown in
FIG. 5, said emitter electrode is connected to earth via a diode
82. This latter arrangement provides even cleaner switching than
the normal diode 40 as shown in FIG. 3.
The operation of the electronic advance and retard device will now
be described in greater detail with the aid of the three waveforms
shown in FIG. 6. As the disc 3 is rotated at crank shaft speed of
the engine, the infra-red radiation from the lamps 5 and 6 impinges
on the respective phototransistors 7 and 8 through the apertures 9
and slits 10. Accordingly, the photo-transistor 7 produces four
current pulses per revolution of the disc 3, whilst the
photo-transistor 8 produces a large number (e.g. 68) of pulses per
revolution. The two triggers 11 and 12 fast switch and amplify
these pulses to produce the waveforms (a) and (b) respectively.
During the time t0 to t1 the photo-transistor 7 is energized by
infra-red radiation and is therefore ON. The transistors 30a and
32a are respectively OFF and ON which means that the output from
the first trigger is at the low level representing a 0. At t1, the
infra-red radiation is cut off and the output of the first trigger
becomes high representing a 1. This output is applied to both the
frequency divider 14 and the transistor 50 of the stage 18. The
frequency divider 14 now counts the pulses from the second trigger
12 according to the number set into it from the computer 16. The
output of the frequency divider 14 is at the low level 0 from the
time t0 up to and beyond the time t1 unless the computer calls for
maximum advance of the ignition. Therefore when the trigger 11
produces a high level output, the power transistors are not
switched because of the continued presence of a low level output
from the frequency divider 14. In the example illustrated the
frequency divider 14 is set to count down a total of six pulses
before its output switches to the high level. Therefore at time t2
when the count of six has been completed, the output becomes high
at the seventh pulse and the transistor 50 switches ON. This in
turn switches the power transistor Darlington pair 54-56 OFF to
switch off the flow of current in the primary winding of the
ignition coil 26, and thus produce the spark through the high
induced secondary voltage on the collapse of the field in the
primary winding of the coil At time t3, the output of the first
trigger reverts to the low level which in turn resets the frequency
divider which also reverts to the low level, as shown by waveform
(c), these events both happening when the phototransistor 7 is
again energized by infra-red radiation.
As and when the load and/or speed of the engine varies, the
computer 16 re-calculates from the information fed to it, the new
value for the count which is applied to the output thereof in
digital form. The frequency divider 14 when started now counts
fewer or more pulses before giving a high level output thus varying
the timing of the ignition so as to achieve an advance or retard
over the previous position. In the example illustrated the computer
has a maximum digital output of sixteen so that the count of the
frequency divider can vary from zero up to fifteen, zero being the
count for maximum advance and fifteen for maximum retard.
The above described device thus provides the electronic control of
the advance and retard of the spark in an ignition system, the
relevant control being calculated in accordance with the speed
and/or load on the engine.
* * * * *