Note: Descriptions are shown in the official language in which they were submitted.
1326178
6 Field of the Invention
7 T~e present invention pertains generally to an
8 electronic ignition system for an internal combustion
engine, such as an outboard marine engine or the like, and
is more particularly directed to a dual schedule ignitlon
11 system having normal and advanced timing schedules with a
12 time base generator for generating two trains of pulses
13 where the first pulse train is advanced a predetermined
14 nu~ber of degrees of engine rota~ion with respect to the
second pulse train.
16 BackgLrou~d~a_~he Inventi~n
17 Previously, outboard marine engines have often
18 utilized various means for accomplishing easier starting.
19 ~or example, such engines may engage a "warm-up`' lever
which -manually advances the ignition timing and partially
21 opens the carburetor throttle plates. The function of such
22 arrangement is to increase the idle speed and the air/fuel
23 ratio of t~e engine when it is started. These conditions
24 ~ allow the engine to start easier and run more smoothly
until it has warmed up to its standard operating
26 temperature.
2~ While many other engine ignition systems have utilized
28 ~arious means to selectively advance the ignition timing
29 characteristic during operation, none of these systems has
been adapted to selectively change the engine timing
31 characteristic as a function of the temperature of the
32 engine during its waxm-up phase, as well as during a
33 predetermined time period regardless of the temperature of
34 the engine, and as a function of the operating speed of the
engine, particularly when operated at a relatively high
36 speed.
' ,:, ,
.~
; `` -2- ~3~6178
A multi-variable ignition system for outb~ard marine
; engines or the like, which selectively adapts ignition
scheduling on this basis is illustrated in applicant's U.S.
Patent No. 4,858,585, issued August 22, 1989, identifying
Gregry Remmers as inventor.
~ he system of Remmers provides an improved ignition
system which utilizes a signal proportional to the speed of
the engine and couples such speed signal with other signals
representing additional engine operating conditions to
selectively modify the ignition timing characteristic of
the engine to accomplish the functional operational
characteristics of: (1) providing protection against engine
damage that may be caused by a runaway speed condition; (2)
; providing a desirable ignition advance during the warm-up
- 15 period of the engine; (3) providing a desirable ignition
advance during the initial engine start up period,
irrespective of the temperature of the engine (i.e., even
when the engine is warm as a result of having been
previously operated); and (4) providing protection against
damage that may be caused by advancing the timing
characteristic while operating the engine above a
predetermined operating speed.
The system as taught in Remmers, while advantageous
in the adjustment of ignition timing in dependence on a
variety of engine operating conditions, does not exhibit
the most advantageous time base generator or means for
distributing the ignition pulses. The time base for that
system is derived from two sets of coils, each of which is
associated with a particular cylinder and crankshaft
position. One set of coils is physically advanced with
respect to the other set to generate two sets of timing
pulses: one a normal pulse train and the other an advanced
pulse train. Nagnets on the flywheel or crankshaft fire
each coil in succession to generate the two pulse trains,
kb:ycc
.
.
1326178
3 _
1 and engine operating conditions are combined to determine
2 which set of pulses is used to ignite the engine.
3 Such ti e base generator is simple and easy to use in
4 small engines, but with higher displacement engines two
ignition coils per cylinder becomes somewhat more difficult
6 to package. Further, for multiple cylinder engines, those
7 with four or more cylinders, it is desireable to produce a
8 schedule of ignition advance based on a plurality of engine
9 operating conditions, most typically, one that varies with
throttle position. This scheduling is difficult to
11 accomplish with a dual ignition coil time base generator.
12 MoreoYer, in Remmers, when inhibiting ignition pulses
13 relative to overspeed and overheated engine conditions, an
14 overspeed threshold is switched immediately from one level
to another level when an overheated condition occurs. For
1~ small displacement outboard marine anqines, an overheated
17 engine condition many times results when the engine i5
18 under considerable load, usually pushing a boat along at a
19 high rate of speed. Inhibiting the ignition pulses without
any transition between the threshold levels under these
21 conditions can cause a rapid and disconcerting
22 deceleration~ Therefore, it would be advantageous to
23 provide a slower transition between the threshold levels so
24 that, if an overheated condition occurs during such a high
load condition, a slower and more acceptable deceleration
26 will occur.
27 Summary of the Invention
28 Accordingly, it is an object of the invention to
29 provide an improved electronic ignition system for an
internal combustion engine.
31 Another ob~ect of the invention is to provide an
32 improved ignition ~ystem which includes an advanced timing
33 schedule, a normal timing schedule and a circuit for
34 switching between the two schedules, or disabling both
schedules, based upon different combinations of engine
36 operating conditions.
37 Yet another object of the invention is to provide a
38 time base generator for an ignition system which has an
- 4 - 1~26178
1 optical encoder rotating synchronously with crankshaft
2 position and generating pulses based upon physical timing
; 3 features of the encoder, wherein the width of a timing
4 feature is determinative of an ignition advance.
Still another object of the invention is to provide an
6 improved iqnition system which disables the ignition
7 schedules based on a high overspeed condition and a low
8 overspeed condition when the engine is overheated, wherein
9 there is a smooth transition between the two conditions.
Accordingly, the invention provides an improved
11 ignition system for internal combustion engines, such as
12 outboard marine engines, or the like. The ignition system
13 includes a time base generator for providing a first train
14 of pulses advanced in time from a second train of pulses.
Each train of pulses is variable according to a schedule
16 with respect to various engine operating parameters, most
17 particularly throttle position.
1~ The time base generator operates by rotating an
19 encoder disk with ti~ing features past an illumination
source which is optically coupled to a photo-sensitive
- 21 element. The timinq fRatures are positioned on the disk
22 such that each feature is a predetermined number of degrees
23 of engine rotation in duration~ A digital waveform is
24 generated indicating the presence or absence of a
particular feature and two pulse trains are derived from
26 the waveform, where the first is indicative of the leading
27 edge of the feature and the second is indicative of the
28 trailing edge of the feature.
29 When the encoder disk is rotated in synchronism with
the engine crankshaft, two trains of pulses forming a time
31 base are generated where one pulse train is advanced over
32 the second pulse train by the duration of each timing
33 feature. The timing of the pulse trains relative to actual
34 crankshaft position is varied by movement of the
illumination source and photo-sensitive element relative to
36 the encoder disk and is scheduled based upon various engine
3? operating parameters.
~ 5 ~ 1326178
1 The first train of pulses provides an advanced
2 ignition timing schedule while the second train of pulses
3 provides a normal ignition timing schedule. An electrical
4 pulse generator and distributor receives the two pulse
trains and selects between the two based upon receiving an
6 advance signal or a normal signal. Alternatively, both
7 schedules arP inhibited by an inhibit signal. The selected
8 pulse schedule is distributed to the correct cylinders in
9 the firing sequence of the engine to iqnite the engine.
A control circuit generates the advance, normal, and
11 in~ibit signals ~ased upon time, engine temperature, and
12 starting condition. Preferably, the advance signal is
13 generated during the starting of the engine and for a short
14 predetermined period thereafter. If the engine is not then
operating above a warm up temperature, the advance signal
16 is continued until this condition occurs. Regardless of
17 the warm-up status and time of running, if the engine is
18 being operated in excess of a first engine speed, the
19 normal signal is generated. In addition, if a third engine
speed is exceeded, the inhibit signal is generated
21 disabling ignition pulses from both schedules. The inhibit
22 signal is also generated if the engine exceeds a second
23 speed and an overheated engine temperature exists. The
24 first speed is, in general, lower than the second speed,
which is lower than the third speed. The overheat
26 temperature is, in general, higher than the warm-up
27 temperature.
28 In a preferred embodiment, the inhibit signal for
29 engine overspeed is generated from a comparator circuit
which compares an engine speed signal against an overspeed
31 threshold. The overspeed threshold is smoothly lowered to
32 a lower overspeed threshold when an overheated condition of
33 the engine occurs, thus preventing rapid deceleration. A
34 threshold generating means is utilized to produce the
thresholds and is implemented by a voltage divider which
36 provides a first threshold voltage which is representative
37 of a high overspeed condition, for example, approximately
38 6,700 RPM. The voltage divider is shunted by an optically
- 6 - 1326178
1 coupled device upon closure of a temperature sensor in the
2 engine to produce a second threshold voltage representative
3 of a low overspeed condition, for example, approximately
4 2500 RPM. A delay means, comprising a capacitor, is
couplcd to the output of the threshold generating means and
6 is generally charged to ~he first threshold. When the
? temperature sensor operates, for example at approximately
8 212' ~., a discbarge path through the optically coupled
9 device is provided which produces a smooth relatively long
decay of the first threshold voltage to the second
11 threshold voltage. A rapid charging path for the delay
12 means is provided to ensure that, when the engine is turned
13 off and then immediately restarted, the delay feature is
14 present~ T~e rapid charging path is disabled by another
optically coupled device upon operation of the temperature
16 sensor.
17 Brief Description of the Drawings
18 ~hese and other objects, features, and aspects of the
19 invention will be better understood and more fully
described upon reading the following detailed description
21 in conjunction with the appended drawings wherein:
22 FIG. 1 is a partially-broken, pictorial perspective
23 view of ~n internal combustion engine of the outboard
24 marine type illustrating a time base generator constructed
in accordance with the invention:
26 FIG. 2 is a cross-sectional view of a first position
27 of the time base generator illustrated in FIG. 1 taken
28 along ~ection line 2-2 of that figure:
29 FIG. 3 is a cross-sectional view of a second position
of the time base generator illustrated in FIG. 1 taken
31 ~long section line 2-3 of that figure:
32 FIG. 4 is a pictorial representation of various timing
33 waveforDs output from the time base generator illustrated
34 in FIG. 1 and the pulse generator and distributor
illustr~ted in FIG. 5;
36 FIG. 5 is system ~lock diagram of an ignition system
37 constructed in accordance with the invention;
- 7 - ~ 3 2 6 17 8
1 FIG. 6 is a graphical representation of the dual
2 ignition schedules as a function of a plurality of engine
3 operating parameters for the system illustrated in FIG. 5;
4 FIG. 7 is a detailed electrical schematic diagram of
S the control circuit illustrated in FIG. 5;
6 FIG. 8 is a detailed electrical sc~ematic diagram of
7 the pulse generator and distributor circuit illustrated in
8 FIG. 5, and
9 FIG. 9 is a detailed electrical schematic diagram of
the capacitive discharge circuits illustrated in FIG. 5
11 Detailed Description of the Pref~rred Embodiment
12 The time base generator 8 of t~e invention is shown to
13 advantage in FIG. 1 w~ere the mechanism for the generation
14 of two timing characteristics or pulse trains is
illustrated. The time base generator 8 includes a
16 generally cylindrically shaped encoder disk 10 which is
17 bolted onto a shaft extension 12 of the crankshaft of an
18 internal combustion engine so as to cause the disk to
19 rotate synchronously therQwith. The crankshaft extension
12 includes a notch 14 wbich is received in a reciprocally
21 shaped hub 13 of the encoder disk 10. The notch 14
22 positions t~e encoder disk 10 and those timing features
23 included thereon at a known crankshaft position, i.e., at
24 an angle relative to top dead center of a particular
cylinder, for example, cylinder 1. To assist in timing the
26 engine, this reference point 0- can be inscribed on the
27 encoder disk 10 so that it can be aligned with a stationary
28 mark on the engine casing by the common strobe light
29 technique. Rotation of the crankshaft is clockwise when
viewed from the top (front) of the engine, as is
31 conventional with most internal combustion engines.
32 The encoding disk 10 has an encoding portion with
33 several timing features located at spaced positions around
34 its periphery. The timing features in the illustrated
implementation are provided as slots 16, 18 and 20,
36 although many other geometric features would suffice~ In
37 the preferred embodiment, the number of slots is equal to
38 the number of cylinders of the engine and they are equally
- 8 - 1326178
1 spaced around the periphery of the encoder disk lo. For a
2 six-cylinder, two cycle engine this means 8iX equally
3 spaced slots at 60- intervals. It is evident that for a
4 six-cylinder, four cycle engine, the slots would be spaced
S at 120- intervals and there would be three in number.
6 Each of the slots 16, 18 and 20 has a width which is
7 a particular angular rotation of the crankshaft, in the
8 preferred implementation, 15-~ Tha encoder disk 10 further
9 includes a synchronizing portion having a timing feature,
slot 22, to indicate the relative position of the disk 10
11 with respect to overall crankshaft position, thus
12 associating each slot 16, 18, and 20 with a particular
13 cylinder. In the illustration, slot 22 is placed in
14 advance of cylinder 1 top dead center and slots 16, 18, and
20 correspond to cylinders 6, 1 and 2, respectively.
16 As ~etter shown in FIGs. 2 and 3, the timing features
17 of the encoder disk 10 make and break the optical
18 illumination path between an LED 26 and two
19 phototransistors 28 and 30 which are mounted in an optical-
coupler block 32. The optical-coupler block 32 is mounted
21 on a timing ring 15 which slidably rotates on the shoulder
22 of a raisad boss 17 of the engine. Spring clips 19, 21, 23
23 retain the ring 15 in the boss 1~ without preventing its
24 rotation. An extension arm 40 of the timing ring 15 is
used to rotate the ring 15 and thus optical-coupler block
26 32 with respect to the fixed relationship of the encoder
27 disk 10 and the crankshaft.
28 Normally, the ring 15 is biased to a setable position
29 by sprinq 43 where it abuts an adjustable stop 45. An
ignition advance assembly 41 including a roller 42 can be
31 used to apply force against a cam surface 47 of the arm 40
32 in order to rotate the optical-coupler block 32 in
33 dependence upon a plurality of engine operating conditions
34 to schedule ignition timing. Such engine operating
conditions could be such things as speed, airflow, water
36 or engine temperature, humidity, manifold pressure,
37 altitude, throttle position, etc.
- 9 - 1326178
1 From FIG. 2, it should be evident that during the
2 rotation of the encoder disk 10 by the crankshaft,
3 illuminating radiation from the LED 26 to the
4 phototransistor 28 is normally blocked until a slot, for
example, the one indicated as 18, rotates between the LED
6 26 and the phototransistor 28. At t~is time, the optical
7 transmission path is open, and the phototransistor 28
8 conducts current producing an electrical signal indicating
9 the presence of the slot. During this time the optical
transmission path to the upper phototransistor 30 is
~1 blocked by the encoder casing. However, during those times
12 when the slot 22 rotates into a position between the LED 26
13 and the phototransistor 30 as shown in FIG. 3, the open
14 transmission path causes phototransistor 30 to conduct
current and produce an electrical siqnal indicating the
16 presence of the synchronizing slot 22 at the position of
17 the optical-coupler block 32.
18 In general, the timing signals generated from the time
19 base generator are shown in FIG. 4. The first signal is a
SYNCH siqnal (FIG. 4A) from slot 22 which is approximately
21 10' in duration and occurs once for every 360~ of engine
22 cranks~aft rotation. The leading edge of the SYNC~ signal
23 occurs some advance~ent before top dead center of a
24 particular cylinder, in the illustrated example, cylinder
1. From this leading edge reference point, all o~her
26 timing pulses and signals for the system can be measured.
27 In general, the SY~C signal is used to reset the
28 distribution sequence of the ignition pulses. ~he second
29 timing signal CYL is a group of pulses forming a square
wave which is generated from the encoder slots 16, 18, 20,
31 etc. (shown in FIG. 4B~. There is a pulse, CYLl-CYL6,
32 respectively, for each cylinder of the engine. The pulses
33 are 15' of engine rotation in duration and separated by
34 equal angular increments of the crankshaft at 60-
intervals.
36 From the pulses of FIG. 4B, two sets of ignition
37 pulses are generated by the pulse generator and distributor
38 70 as shown in FIG. 4C. The leading edge of each cylinder
... . ,: . . - . ~ .
- . ,... : .
1326178
-- 10 --
1 pulse, CYLl-CYL6, is used to generate one train of advanced
2 pulses A, and the trailing edge of each cylinder pulse is
3 used to generate a second train of normal pulses N. The
4 Advanced pulse train A is used in an advanced timing
schedule and the normal pulse train N is used for a normal
6 timing schedule as will be more fully described
7 hereinafter.
8 In the preferred embodiment, the normal pulses at idle
9 are at top dead center of each associated cylinder, while
the advanced pulses are advanced over the normal pulses a
11 predetermined increment, 15'. It is seen that the width of
12 the encoder slots 16, 18 and 20 determines the
13 predetermined advancement of the advanced schedule over the
14 normal schedule. Further, the position of the optical-
coupler block 32 relative to the fixed relationship of the
16 encoder disk 10 and crankshaft determines the variance of
17 timing with respect to engine operating variables and, thus
18 the actual timing schedule.
19 An i~proved ignition system using the time base
generator 8 illustrated in ~IGS. 1-4 is more fully shown in
21 the block diagram with reference to ~IG. 5. The ignition
22 ~ystem includes a pulse generator and distributor 70 which
23 produces a trigger pulses TRG to a number of capacitive
24 disch~rge circuits 71-76, wherein each capacitive discharge
circuit is associated with a particular cylinder. When
26 enabled fro~ the pulse generator and distributor 70 by
27 individual enable lines ENl-EN6, a trigger pulse TRG will
28 cause a capacitive discharge circuit 71-76 to provide a
29 high current, low voltage pulse of approximately 300V
tbrough the primary of a step-up transformer 77-82,
31 respectively. The step-up transformers 77-82 step up the
32 voltage of the current pulses from the capacitive discharge
3~ circuits into hig~ tension pulses which fire spark plugs
34 83-88, respectively, of an associated cylinders of the
engine. The spark plugs 83-88 are ignited sequentially in
36 the firing order of the engine by their respective
37 connection in that order relative to the sequence of
38 firings of the capacitive discharge circuits.
... .
!
:: '
32~ 78
1The time base generator 89 is shown generating the
2pulse trains SYNC and CYL to the pulse generator and
3distributor 70, which are the signals as sbown in FIG. 4A
4and 4B. The trigger pulses TRG which are derived from
5these signal ~y the pulse generator and distributor 70 are
6those as shown in FIG. 4C. They are distributed by
7generating the enable signals ENl-EN6 based on crankshaft
8position and tbe firing order of the engine. Whether the
9trigger pul~es TRG are the advanced schedule A or the
10 `normal schedule N, depends upon a control circuit 90.
11~he control circuit 90 determines from the engine
12operating conditions including means for sensing RPM 92,
13means for sensing an overheat condition 94, means for
14sensing a warmup condition 96, and means for sensing a
15starting condition 98 wbether the advanced timing schedule,
16the normal timing schedule, or no timing schedule should be
17used. This selection information is delivered to the pulse
18generator and distributor 70 via an ADVANCE/NORNAL signal
19on line 99. Alternatively, the control circuit 90
20generates an INHIBIT signal on line 101 to completely stop
21any ignition pulses from being generated to the engine.
22FIG. 6 is a graphical representation of the advanced
23timing schedule 91 and the normal timing schedule 93
~4illustrating an + advance angle before top dead center
25~TDC) as a function of an engine operating parameter, or
26combination of parameters. In tbe preferred embodiment,
27the schedules are a similar function of throttle position.
28Nhile more complex scbedules can be used, outboard marine
29engines advantageously advance ignition timing based on
30throttle position.
31Tbe advanced timing schedule 91 is used during
32starting and warmup durations, while the normal timing
33schedule 93 is used at all other times, except in those
34instances when both ignition schedules are inhibited. It
35is seen that there is always a +15- advance between the
36advanced scbedule and the normal schedule which is
37dependent upon the spacing between pulse trains A and N
38from the time base generator 8. The spacing between the
- 12 - 1 32~i 78
1 pulses is due to the slot widths of the optical e~coder
2 disk 10. The variation in advance angle as a function of
3 engine operating parameters (schedule) is developed by the
4 rotation of the optical-coupler block 32 relative to the
fixed position of the optical encoder disk 10 on the
6 crankshaft. The functions or schedules shown in FIG. 6 are
7 generally the same for the advanced timing schedule and the
8 normal timing schedule and monotonically increase with
9 increase in throttle position. However, these can be very
complex schedules depending upon the shape of the cam
11 surface which displaces the arm 40 to cause the rotation of
12 the timing ring 15 and the relative movement of the
13 optical-coupler block 32 with respect to the encoder
14 disk 10.
The control cixcuit 90 will now be more fully
16 described with respect to the detailed electrical schematic
17 of FIG. 7. The power supply of the present ignition
18 system, indicated generally at 64, includes lines 66 and 68
19 which are connected to a stator coil 71 of an alternator
and to a full-wave rectifier bridge 70. Several magnets on
21 the engine flywheel ~not shown) induce a voltage in the
22 stator coil 71 as the flywheel turns, which voltage is
23 rectified by the bridge 70. Overvoltage protection is
24 provided by the connection of a triac 72 between lines 66
and 68. The power supply 64 generally provides
26 approximately a ~20V output on line 74. The +20V output is
27 further regulated by NPN transistor 76 having a Zener
28 diode 78 and bias resistor 79 connected to its base. The
29 transistor 76 provides a +15V regulated supply on line 80.
This ~15 volt regulated supply line 80 is additionally
3~ coupled to the power supply line of the capacitive
32 discharge circuits 71-76.
33 The stator coil 71 produces six pulses for every
34 revolution of the flywheel and thereby provides tachometer
pulses on line 86 which are coupled through a capacitor 82
36 and resistor 84 to the freguency input (F/I) of a frequency
37 to voltage converter 88. The freguency to voltage
38 converter 88 has an output OUT which generates a voltage
- 13 - 1~26178
1level on line 90 that is directly proportional to the
2frequency of the pulses, and hence RPM of the engine. A
3variable resistor ~2 and a fixed resistor 94 define a
4voltage divider that is adjustable to vary the level of the
5output voltage produced on the output line 90 for a
6particular voltage.
7one feature of the control circuit 90 provides
8protection against a runaway speed condition occurring
gduring oper~tion of the engine. This is accomplished by
10utilizing the voltage level generated by converter 88 on
11line 90 to inhibit the iqnition pulses. The voltaqe on
12line 90 is connected to the inverting input of a
13comparator g6 through reæistor 98 and line 100. The
14nonin~erting input of the comparator 96 receives a
15reference voltage on line 102 against which the voltage on
16line 100 is compared. The output line 104 of the
17comparator 96 makes a transition to a low logic level
18(approximatèly 0 volts) when the voltage on the input
19line 100 is greater than tha reference voltage on line 102.
20For an operating condition that does not represent an
21overheated condition of the engine, the voltage level on
22line 102 is designed to be approximately +5 volts. The
23+S volts on line 102 is supplied by the power supply from
24line 80 through voltage dividing circuitry. Line 80 is
25connected through a resistor 106 to a line 108 that is
26connectad to a 2ener diode 110 to provide a regulated
27voltage of approxi~ately +9V on line 108. Line 108 is
28connected to resistors 112 and 114 which function as a
29voltage divider to provide a voltage of approximately +5
30volts on a line 116. The line 116 is connected to the
31line 102 through a resistor 118 and applies the reference
32+5V to the noninverting input of the comparator 96. A low
33logic level on line 104 is inverted by an invertor 105
34(FIG. 8) to produce a high logic level disabling signal,
3Sthe INHIB~T signal, to the pulse generator and distributor
36circuit 70.
37During operation, the converter 88 produces a voltage
38on the output line 90 which is supplied to the inverting
`. - ' .. :
., .
.
- 14 ~ 1 3 2 6 1 7 8
1 input of comparator 96. When the speed reaches
2 approximately 6,700 RPM, the comparator 96, after comparing
3 t~e voltage output to the reference voltage of
4 approximately +5V, produces a low logic level on the output
line 104 that results in the disa~ling INHIBIT signal.
6 Protection against ~ runnway speed condition is thereby
7 provided by a relatively few number of circuit components.
8 ` It should be understood that the disabling of the
9 ignition pulses may occur for an incremental short period
of time and on a cyclic basis. If the speed is close to
11 the over speed condition, as soon as an overspeed condition
12 is detected, the inhibiting will occur and the speed will
13 quickly drop ~ecause of the lack of ignition pulses. When
14 the opera~ing speed falls below the threshold, the INHIBIT
1~ signal will be switched off and the ignition pulses will no
1~ longer be disabled. Thus, as a practical matter, the
17 engine speed may be ~odulated around the threshold speed
18 that triggers the comparator 96.
19 In accordance with another aspect of the control
circuit 90, the maximum speed of operation is reduced from
21 approximately 6,700 RPM to approximately 2,500 RPM when an
22 overheated engine condition is detected. This is
23 accomplished using the same comparator 96 in combination
24 with temperature sensing circuitry for the engine. In this
regard, light emitting diodes (LEDs) 124 and 126 are
26 optically coupled to phototriacs 125 and 127, respectively.
27 The LEDs 124 and 126 are connected to the +20V supply on
28 line 74 through resistor 128, and to ground through a
29 diode 130 and an overheat temperature switch 132. The
overheat temperature sw~tch 132 is a bimetallic switch
31 positioned in the head of the engine to sense the engine
32 temperature. The switch 132 is adapted to close at a
33 temperature of approximately 212-F, and when closed
34 provides a conduction patb through LEDs 124 and 126 placing
the phototriacs 125 and 127 into conduction.
36 This operation lowers the reference voltage applied to
37 the noninverting input of the comparator 96 to
38 approximately 2.0V. The lower reference voltage results in
- 15 - 1326~78
1 the INHIBIT signal being produced on line 104 at a lower
2 operating speed, as is ~ntended. In operation, when an
3 overheated condition is detected, the comparator 96
4 switches to a low logic level at an operating speed of
about 2,500 RPM and disables the ignition pulses to limit
6 the speed as previously described. ~he speed limiting,
7 however, takes plàce at a lower speed limit of 2,500 RPM
~ rather than t`he upper speed limit of 6,700 RPM.
9 The nature of the phototriac 125 i8 such that it will
not be turned off until power is removed from the circuit,
11 which will not occur until the engine is turned off. This
12 feature is desirable in that it prevents the circuitry from
13 cycling on and off at or about the critical overheat
14 temperature~ However, to prevent an abrupt c~ange in the
overspeed t~reshold when the overheat switch 132 closes,
16 there is provided a capacitor 129 connected to the
1~ noninverting input of comparator 96. Normally, the
18 capacitor 129 is charged up to ~he upper threshold voltage
19 of +5V. Nhen an overheat condition occurs, the capacitor
129 gradually discharges through phototriac 125 and
21 resistor 131 to ground. Preferably, the discharge path
22 lowers the voltage at a predQtermined rate which is
23 exponential in the illustration, but which could be any
24 function of time, for ~xample, linear. The time constant
of the discharge pat~ is long enough, about 4-10 secs., to
26 produce a smooth transition between the upper and lower
27 threshold speed limits and, as a consequence, a gradual
28 deceleration of a boat or other water vehicle powered by
29 the engine. The capacitor 129 is charged rapidly to the
upper threshold voltage at start-up by a resistor 135 and
31 diode 133. This current path is shunted to ground and
32 disabled by phototriac 127 during an overheat condition.
33 Another attribute of the present control circuit 90
34 includes the pro~ision of automatically providing an
advanced timing schedule or advanced ignition
36 characteristic when the engine i~ initially started and
37 until the engine reaches a predetermined minimum warm up
38 temPerature, unless a 6Pecific e w ine RPM is exceeded.
.
' '' '" '. ,, .;
- 16 - 1 32 6 1 78
1 With respect to the warm-up aspect of the circuit
2 operation, a line 134 is connected through a warm-up
3 switch 136 to ground. The switch 136, which is a
4 bimetallic sensor, closes when the sensed engine
temperature axceeds a warmup temperature, within the range
6 of about 90'F to lOO-F. The line 134 is no~mally high
7 ~open) but makes a transition to a low logic level (ground)
8 when the engine warms up sufficiently to close the
- 9 switch 136. The line 134 is connected to the +20V supply
through an LED 135 and resistors 137 and 139. The LED 135
11 is optically coupled to ~ phototriac 141 which is connected
12 to the noninverting input of a comparator 140 via a
13 resistor 142. The co~parator 140 provides a high logic
14 level output on line 144 when switch 136 i8 not closed.
The output line 144 of comparator 140 is connected to
16 the noninverting input of a comparator 148 which acts as an
17 AND gate. Another input line 152 to the comparator 148 is
18 normally ~iqh until a predetermined speed is reached by the
19 angine as will be sub~eguently dQscribsd. The comparator
148 provides a high logic level output on line 154 only
21 when the input lines 146 and 152 are both at a high logic
22 levels. W~en the line 154 is a high logic level, the
23 ADVANCE ~ignal is generat~d and the advanced timing
24 characteristic output to the capacitive disch~rge circuits.
When the output on line 154 is a low logic level, the
26 NORNAL signal is generated and the normal timing
27 characteristic output to the discharge circuits.
28 It will be understood from the foregoing that the
29 engine will be operated with the advanced timing
characteristic until the engine warms up to an operating
31 te~perature of about 90- to 100-. When warmup switch 136
32 closes, the output 144 will be pulled to a low logic level
33 thereby 6witching the comparator 148 to a low logic level
34 and producing operation by the normal ign~tion timing
characteristic.
36 However, the engine will also operate in its advanced
37 timing characteristic during start up and for a ~hort
38 predetermined period after initial start up, i.e., for
- 17 - 1326178
1 approximately 5 to lo seconds, regardless of the
2 temperature of t~e engine. This is accompl~shQd by having
3 the starter solenoid 155 apply the battery voltage B+ to a
4 capacitor 160 via line 162, a diode 164 and a line 166 when
the ignition switch is closed. Line 162 i8 connected to
6 the noninverting input of the comparator 140 via a
7 resistor 167. Upon starting of the engine, the battery
8 voltage B~ will charge the capacitor 160 and provide a high
9 logic level on the input line 1~8 to place the engine in
10 ` the advanced timing characteristic mode of operation during
11 the starting period of the engine and for the time period
12 required to discharqe the capacitor 160 to a level where
13 the comparator 1~0 switches to a low output. In the
14 illustrated embodiment, this is preferably about 7 seconds,
although t~e circuit co~ponents can be chosen to provide a
16 longer or shorter time period if desired.
17 In accordance with yet another aspect of the present
18 control circuit 90, provision is made to automatically
19 inhibit the advanced timinq characteristic when the
operating speed of the angine exceeds a predetermined level
21 of approximately 1,500 RPN. This characteristic is to
22 prevent operation of the enqine with an ignition advance
23 above this speed which could result in damage to the
24 engine.
~5 To inhibit the advanced timing charac~eristic, the
26 voltage from converter 88 on output line 90 is connected to
27 t~e inverting input 100 of a comparator 170 on line 100.
28 The noninverting input of the comparator 170 is connected
29 to the +5V reference supply line 116 via a resistor 174.
The reference voltage is chosen to cause the comparator to
31 have its output line 176 switched to a low logic level when
32 the speed voltaqe increases to level equal to an operatinq
33 speed of approximately 1,500 RPM. When the output line 176
34 is at a low logic level, it removes the high logic level
applied to the comparator 148 thereby causing it to switch
36 to a low loqic level and disabling the ADVANCE signal to
37 remove the enqine from its advanced timing characteristic
38 mode of operation. Thus, the circuitry always prohibit~
- 18 - 1326178
1 operation in an advanced timin~ mode above approximately
2 1,500 RPM, even if the engine i~ not warmed up or is stlll
3 within the start-up period of approximately 7 ~econds after
4 staring.
The power for operating the control circuit 90 is
6 obtained from a voltage induced in the stator coil 71 that
7 is regulated by the power circuitry. During the initial
8 start-up period, the cranking speed may not be sufficient
9 to provide reliable volt~ge levels to ensure correct
circuit operation. Provision is made to suppl~ment the
11 output of the power supply wi~h the battery voltage B+ from
12 the starter golenoid during cranXing. This i8 accomplished
13 by coupling the battery voltage B+ on line 166 to line 74
14 via diode 164, line 1~2 and diode 180.
FIG. 8 illustrates the detailed electrical schematic
16 of the pulse generator and distributor circuit 70. In
17 general operation the pulse generator and distxibution
18 circuit 70 performs three functions. Initially, it
lg generates the advanced pulse train A and the normal pulse
train N from the CYL waveform. Secondly, the circuit
21 selects ~tween the pulse train A and pulse train B, or
22 inhibits bo~h pulse trains, based on the input ~ignals
23 ADVANCE, NORMAL, and INHIBIT. Additionally, the circuit
24 generates the enabling 6ignals, ENl-EN6 based on the SYNC
waveforo and the CYL waveform to distribute the selected
26 pulse train as the TRG cignal to the correct cylinders in
27 the firing order of the enqine.
28 The LED 26 is shown as being always powered on by its
29 connection in a conductive path between +15V, the emitter-
collector path of NPN transistor 242, a resistor, and
31 ground. The transistor 242 regulates the current flow
32 through LED 26 by having a predetermined bias voltage on
33 its b~se. The bias voltage iB generated by the c~mbination
34 of Zener diode 238 and resistor 240 connected between the
+lSV supply and ground. Phototransistors 28 and 30
36 generate the previou~ly described signals CYL and SYNC when
37 illuminated by LED 26.
- lg - 1326178
1 The pulse generator and distributor circuit 70
2 comprises basically two monostable multivibrators 200 and
3 202 and a synchronous sequQntial counter 222. Generally,
4 the monostable 200 is configured to be triggered by the
positive going edge of a pulse to its TR+ input.
6 Application of an edge transition from a low logic level to
7 a high logic lavel at input TR+ will produce a positive
8 going pulse ~rom its Q output which becomes the advanced
9 pulse train A. Conversely, the monostable 202 i8
configured to produce a positive qoing pulse from its Q
11 output ~hen a negative going edge of a pulse is applied to
12 its TR- input, which results in the normal pulse train N.
13 Both the TR~ input of monostable 200 and the TR- input
14 of monostable 2Q0 are connected to the output of a NAND
gate 220 whic~ is configured as an invertor and driven by
16 the CYL signal. The CYL signal is generated by the
17 illumination of phototransistor 28 which is connected
18 across both inputs of the NAND gate 220. The NAND gate 220
19 has an open collector output connected to the ~unction of
a resistor 224 and a capacitor 226 which inverts the CYL
21 signal, thus providing a positive going transition on the
22 leading edge of the CYL signal and a negative going
23 transition on the trailing edge of the CYL signal. The
24 ADVAN OE and NORMAL signals are combined into a single
signal, ADVANCE/NORMAL, which is appliad to the negative
26 true reset terminal R of mono~table 200. The ADVANCE
27 signal is the high logic level of the combined signal while
28 the NORMAL signal is the low logic level.
29 With thiæ circuit, two pulses are generated for each
of CYL signal pulse and form two pulse trains, one based on
31 the leading edges of the CYL ~ignal from monostable 200 and
32 one based on t~e trailing edges of the CYL signal from
33 monostable 202. If the advanced pulses are selected, the
34 ADVANCE/NORMAL ~ignal is a high logic level and both pulse
trains are transmitted to the cylinders. Because the
36 ignition circuit is a capacitive discharge circuit, the
37 normal pulses which follow the advancQd pulses do not
38 perfor~ a retriggering of the ignition system as the
- 20 - 132 617 8
1 ignition capacitance has not yet recharged. If the normal
2 pulses are selected, the ADVANCE/NORMAL signal is a low
3 logic level which holds monostable 200 re8Bt 80 that only
4 the normal pulse train is generated.
The first pulse train A and the second pulse traln N
6 are combined in a QR gate 204 before being inverted by
7 invertor 206. The output of invertor ~06 is fed through OR
8 gate 210 and finally inverted in invertor 212 before
9 becoming the trigger signal TRG. The INHIBIT signal is
provided through an invertor 105 and OR gate 208 to produce
11 a disabling signal at OR gate 210 during its presence.
12 When the INHIB~T signal is ~ low logic level, a high logic
13 level di~ables OR qate 210 and both pulse trains.
14 Anot~er inhibiting signal to OR gate 208 is provided
by a D-type bistable 214 which h~s its ~Q output connected
16 to one of the inputs of the gate. The reset input R of
17 bistable 214 is connected to the output of invertor 216
18 whose input is connected to a resistor-capacitor
19 combination connected between l15V and ground. The set
terminal S of the bistable 214 is connected to the SYNC
21 signal at the output of NAND gate 218. In operation, the
22 bistable 214 w~ich is reset on power up normally disables
23 the trigger pulses TRG until the first SYNC signal occurs.
24 This is to prevent misfiring of the ngine when initial
engine rotation beqins and the ignition system is not yet
26 synchronous with the crankshaft. The capacitor 234 is
27 generally c~arged up to 115V providing a normally low logic
28 level on the res~t input of the bi~table 214. This
29 produces a high logic level output from the *Q output and
thus dis~bles OR gate 210. When the first SYNC signal
31 occurs, the bistable 214 is set removing the disabling
32 signal from OR gat~s 208 and 210.
33 The count~r 222 generates the enabling siqnals ENl-EN6
34 sequentially from its Q0-Q5 outputs, respectively. The
enabling signals ENl-EN6 are generated in sequence and then
36 cycled in the same ~equence. The SYNC ~ignal cau~ed by the
37 illumination of phototransistor 30 is used to apply a high
38 logic level to the reset input RS~ of the counter 222. The
- 21 - ~32~78
1 SYNC signal is inverted by NAND gate 218, resistor 228 and
2 capacitor 230 in the same ~anner the CYL signal was
3 inverted. The SYNC signal causes the counter to reset nnd
4 generate the ENl signal thereby arming the respective
capacitive disch~rge circuit associated therewith. The
6 pulses A or N are then applied to the ~rmed circuit firing
7 the circuit in concert with its respective crankshaft
8 position. After the trigger pulse has been applied, the
9 trailing edge of the *Q output of the monostable 202 clocks
the counter 222 by application of the *N pulses to itR CLK
11 input. ~his advances the counter to the next enabling
12 signal, EN2, and so on in the sequence until the cycle
13 continues.
14 Wit~ reference to FIG. 9, the capacitive discharge
circuits ~1-76 operate identically with respect to each of
16 the cylinders which ~ay be present in the engine. In the
17 disclosed embodiment, there are six cylinders and six
18 discharge circuits, but only one of the circuits 76 for the
19 cylinders will be described in detail for the purpose of
clarity.
21 The six capacitive discharge circuits 71-76 are used
22 to disch~rge alternate ignition capacitors 330 and 326
23 which are charged by the rectification of charge coil
24 pulses. The charge coil pulses for one bank are rectified
by diode bridge 328 for capacitor 326 and the charge coil
26 pulse for the othQr bank are rectified by diode bridge 332
27 for capacitor 330.
28 When an ignition pulse TRG is passed through NAND
29 gate 300 from linQ 322, it will enable PNP transistor 302
to pass a pulse from a voltage source on line 318 through
31 diode 306. The voltage sourco on line 318 is t~e regulated
32 voltage +15V from the power supply as previously described.
33 NAND gate 300 i~ ar~ed by the pulse generator and
34 distributor 70 by the enable pulse, EN6. The resulting
pulse which i8 produced by the coincidence of the pulse
36 signal TRG and the enabling level EN6 iB directed to the
37 gate terminal of an SCR 316 to turn it on. The SCR 316
38 when triggered into conduction, discharges one of the
'' ', ` ''`', . ' .
.
. . .
- 22 - 1326178
1 previously charged ignition capacitors 326 through circuit
2 path from its anode, cathode, and line 320 attached to the
3 primary of the ignition coil for cylinder number 6.
4 To control the two timing whedules, the control
s circuit 90 either allows the advanced pulses and the normal
6 pulses to be applied to the NAND gates or inhibits the
7 advanced pulses so that only the normal pulses are applied
8 to the NAND gates. This is acco~plished by holding
9 advanced monostable reset with a low logic level, the
normal signal. In addition, for particular engine
11 conditions, both sets of pulses are inhibited. ~hus, an
12 ignition system has been shown which can provide an
13 advanced schedule, a noxmal schedule or an inhibition of
14 both schedules based upon engine operating conditions.
While a preferred embodiment of the invention has been
16 illustratedt it will be o~vious to those skilled in the axt
17 that various modifications and cbanges may be made thereto
18 without departing from the spirit and scope of the
19 invention as bereinafter d-fined in the appended claims.
