CA1326178C - Dual schedule ignition system - Google Patents

Abstract

Abstract of the Disclosure An ignition system for an internal combustion engine, such as an outboard marine engine, which includes an advanced timing schedule, a normal timing schedule, and a circuit for switching between the two schedules or disabling both schedules based upon engine operating conditions. The ignition system includes an opto-electronic time base generator which produces two sets of timing pulses relative to crankshaft position which are normal timing pulses and advanced timing pulses. The time base generator comprises a LED-phototransistor pair and an encoder disk attached to the crankshaft with slots to interrupt the emission path between LED-phototransistor pair. The normal pulses are generated based upon the trailing edge of each slot while the advanced pulses are generated based up the leading edge, wherein the width of the slots indicate the degree of advancement of the advanced schedule over the normal schedule. Both schedules are inhibited based on a high overspeed condition and a low overspeed condition when the engine is overheated, wherein there is a smooth transition between the two conditions.

Description

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.

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; `` -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 .
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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 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 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.

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 ... . ,: . . - . ~ .
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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.

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:: ' 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 `. - ' .. :
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- 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.

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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 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~

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 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 '' ', ` ''`', . ' .
.

. . .

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.

Claims (71)

1. An ignition system for an internal combustion engine of the type which has an ignition capacitor means, means for charging the ignition capacitor means, and means for discharging the ignition capacitor means in response to trigger pulses, the system comprising:
trigger pulse generating means for producing trigger pulses related to crankshaft position, said trigger pulse generating means being adapted to provide a first timing characteristic, and a second timing characteristic which is advanced a predetermined time with respect to said first timing characteristic;
said trigger pulse generating means including a time base generator comprising an encoder disk having a generally cylindrical encoding portion and an end support, said end support being connected to the crankshaft of the engine for rotating said encoder disk synchronously therewith, said encoding portion including timing features of a predetermined width;
means for sensing the beginning of each timing feature and producing a trigger pulse indicative thereof to generate said advanced timing characteristic; and means for sensing the ending of each timing feature and producing a trigger pulse indicative thereof to generate said normal timing characteristic;
whereby the width of said timing features correspond to the degree of advance of said second timing characteristic over said first timing characteristic;
means for generating an advance signal or a normal signal based upon at least one operating condition of the engine;
said trigger pulse generating means providing trigger pulses with said second timing characteristic in response to an advance signal being applied thereto and providing trigger pulses with said first timing characteristic in response to a normal signal being applied thereto.

2. An ignition system as set forth in Claim 1 wherein said predetermined timing features are relatively transparent and said sensing means include:
emitting means positioned on one side of said encoding portion and detecting means positioned on the other side of said encoding portion, said detecting means generating one logic level when detecting said emitted radiation and generating another logic level when not detecting said emitted radiation.

3. An ignition system as set forth in Claim 1 wherein said sensing means further include:
an advance monostable triggered by the leading edge of said cylinder signal to output pulses with said second timing characteristic; and a normal monostable triggered by the trailing edge of said cylinder signal to output pulses with said first timing characteristic.

4. An ignition system as defined in Claim 3 wherein:
said advance signal enables said advance monostable; and said normal signal disables said advance monostable.

5. An ignition system as defined in Claim 3 wherein:
said advance signal disables said normal monostable; and said normal signal enables said normal monostable.

6. A time base generator for an ignition system of an internal combustion engine having a crankshaft, said time base generator comprising:
an encoder disk which rotates synchronously with the crankshaft of the engine and includes a plurality of timing features of a predetermined width which are at fixed locations relative to the crankshaft and includes at least one synchronizing feature which is at a fixed location relative to the crankshaft and to at least one of said timing features;
detector means for detecting the presence or absence of said timing features and said at least one synchronizing feature and for generating digital signals representative thereof; and pulse generating means for generating a first pulse train from the trailing edge of each timing feature represented in said digital signal and for generating a second pulse train from the leading edge of each timing feature represented in said digital signal whereby the pulses of said second pulse train are advanced from the pulses of said first pulse train by a predetermined angular rotation of the crankshaft determined by the width of each timing feature.

7. A time base generator as defined in Claim 6 wherein:
said timing features are all of the same width.

8. A time base generator as defined in Claim 6 wherein:
said timing features are not all of the same width.

9. A time base generator as defined in Claim 6 wherein the internal combustion engine is a two-cycle engine and wherein:
each timing feature corresponds to one cylinder of the engine.

10. A time base generator as defined in Claim 6 wherein the internal combustion engine is a four-cycle engine and wherein:
each timing feature corresponds to two cylinders of the engine.

11. A time base generator as defined in Claim 9 wherein:
said synchronizing feature indicates a predetermined point in the firing order of the engine.

12. A time base generator as defined in Claim 11 wherein:
every other of said synchronizing features indicates a predetermined point in the firing order of the engine.

13. A time base generator as defined in Claim 6 which further includes:
means for mounting said detector means and for following movement of said detector means relative to the crankshaft and said fixed positions of said timing features.

14. A time base generator as defined in Claim 13 wherein said means for mounting include:

a mounting ring concentric to the crankshaft which is adapted to rotate about the crankshaft to vary the position of the detector means relative thereto.

15. A time base generator as defined in Claim 14 wherein said mounting means further include:
means for rotating said mounting ring dependently upon at least one operating parameter of the engine.

16. A time base generator as defined in Claim 15 wherein:
said at least one operating parameter of the engine is the detected throttle position.

17. A time base generator as defined in Claim 6 wherein:
said encoder disk is substantially cylindrical in shape and includes a timing portion having said timing features implemented as timing slots about its periphery.

18. A time base generator as defined in Claim 17 wherein:
said detector means includes a first emitter and first receiver of optical radiation coupled through an optical path and located such that said timing features make or break said optical path as said encoder disk rotates.

19. A time base generator as defined in Claim 18 wherein:
said detector means further includes:
a second emitter and second receiver of optical radiation coupled though an optical path and located such that said at least one synchronizing feature makes and breaks said optical path as said encoder disk rotates.

20. An ignition system for an internal combustion engine having multiple cylinders driving a crankshaft, each cylinder having at least one spark plug to ignite an air/fuel mixture therein, said ignition system comprising:
a plurality of cylinder discharge means, each corresponding to one of the cylinders and including ignition capacitor means, means for charging said ignition capacitor means, means for discharging said ignition capacitor means in response to trigger pulses, and step-up transformer means for generating a high tension voltage pulse to the spark plug of the cylinder in response to the discharge of said ignition capacitor means;
means for generating an advance signal or a normal signal based upon at least one operating parameter of the engine:
a time base generator including an encoder disk which rotates synchronously with the crankshaft of the engine and includes a plurality of timing features of a predetermined width which are at fixed locations relative to the crankshaft and at least one synchronizing feature which is at a fixed location relative to crankshaft position and to at least one of said timing features;
detector means for detecting the presence or absence of said timing features and said at least one synchronizing features and for generating digital signals representative thereof;
trigger pulse generating means for generating a first pulse train from the trailing edge of each timing feature represented in said digital signal and for generating a second pulse train from the leading edge of each timing feature represented in said digital signal whereby the pulses of said second pulse train are advanced from the pulses of said first pulse train by a predetermined angular rotation of the crankshaft as determined by the width of each timing feature;
said trigger pulse generating means providing said second pulse train to said cylinder discharge means in response to said advance signal being applied thereto and providing said first pulse train to said cylinder discharge means in response to said normal signal being applied thereto; and means for generating sequential enabling signals in the firing order of the engine based upon said synchronizing feature, each of said enabling signals being applied to corresponding cylinder discharge circuits to discharge said ignition capacitor on the coincidence of a respective said enabling signal and a trigger pulse.

21. An ignition system as defined in Claim 20 wherein said means for generating an advance signal or a normal signal includes:
means for generating said advance signal during engine start up.

22. An ignition system as defined in Claim 21 wherein said means for generating said advance signal further includes:
means for generating said advance signal for a first predetermined period of time after engine start up.

23. An ignition system as defined in Claim 22 wherein said means for generating said advance signal further includes:
means for generating said advance signal until the engine temperature exceeds a first predetermined level.

24. An ignition system as defined in Claim 23 wherein said means for generating an advance signal or a normal signal includes:
means for generating said normal signal if the speed of the engine exceeds a first predetermined level, regardless of said first period and first temperature.

25. An ignition system as defined in Claim 24 which further includes:
means for disabling said trigger pulse generating means when the engine is operating above a third predetermined speed which is greater than said first speed.

26. An ignition system as defined in Claim 25 which further includes:
means for disabling said trigger pulses when the engine is operating above a second predetermined speed and above a second predetermined temperature; and wherein said second temperature is greater than said first temperature and said second speed is greater than said first spaced, but less than said first speed.

27. An ignition system as defined in Claim 26 which further includes:
means for delaying the disablement of said trigger pulse generating means at said second speed for a predetermined period of time after the engine reaches said second predetermined temperature.

28. An ignition system as defined in Claim 27 wherein said means for delaying includes:
means for providing said third speed as a high threshold;
means for providing said second speed as a low threshold; and moving said high threshold to said low threshold as a function of time after said engine reaches said second predetermined temperature.

29. An ignition system as defined in Claim 20 wherein:
said timing features are all of the same width.

30. An ignition system as defined in Claim 20 wherein:
said timing features are not all of the same width.

31. An ignition system as defined in Claim 20 wherein the internal combustion engine is a two-cycle engine and wherein:
each timing feature corresponds to one cylinder of the engine.

32. An ignition system as defined in Claim 20 wherein the internal combustion engine is a four-cycle engine and wherein:
each timing feature corresponds to two cylinders of the engine.

33. An ignition system as defined in Claim 31 wherein:
said synchronizing feature indicates a predetermined point in the firing order of the engine.

34. An ignition system as defined in Claim 32 wherein:
every other of said synchronizing features indicates a predetermined point in the firing order of the engine.

35. An ignition system as defined in Claim 20 which further includes:

means for mounting said detector means and for allowing movement of said detector means relative to the crankshaft and said fixed positions of said timing features.

36. An ignition system as defined in Claim 35 wherein said means for mounting include:
a mounting ring concentric to the crankshaft which is adapted to rotate about the crankshaft to vary the position of the detector means relative thereto.

37. An ignition system as defined in Claim 36 wherein said means for mounting further include:
means for rotating said mounting ring dependently upon at least one operating parameter of the engine.

38. An ignition system as defined in Claim 37 wherein:
said at least one operating parameter of the engine is the detected throttle position.

39. An ignition system as defined in Claim 20 wherein:
said encoder disk is substantially cylindrical in shape and includes timing portion including said timing features implemented as timing slots about its periphery.

40. An ignition system as defined in Claim 39 wherein:
said detector means includes a first emitter and first receiver of optical radiation coupled through an optical path and located such that said timing features make or break said optical path as said encoder disk rotates.

41. An ignition system as defined in Claim 40 wherein said detector means further includes:
a second emitter and second receiver of optical radiation coupled though an optical path and located such that said at least one synchronizing feature makes and breaks said optical path as said encoder disk rotates.

42. An ignition system for an internal combustion engine of the type which has an ignition energy storage means, means for charging the ignition energy storage means, and means for discharging the ignition energy storage means in response to trigger pulses, the system comprising:
trigger pulse generating means for producing trigger pulses related to crankshaft position; and means for inhibiting the generation of said trigger pulses as a function of at least one engine operating condition, said inhibiting means including means for inhibiting said trigger pulses when the engine is operating in excess of a first predetermined speed, means for inhibiting said trigger pulses when the engine is operating in excess of a second predetermined speed and in excess of a predetermined temperature wherein said second predetermined speed is less than said first predetermined speed, and means for delaying the inhibition of said trigger pulses at said second predetermined speed for a period of time after the engine reaches said predetermined temperature.

43. An ignition system as set forth in claim 42 wherein:
said first predetermined speed is approximately 6,700 RPM.

44. An ignition system as set forth in claim 43 wherein:
said second predetermined speed is approximately 2,500 RPM.

45. An ignition system as set forth in claim 44 wherein:
said predetermined temperature is approximately 212' F.

46. An ignition system as set forth in claim 45 wherein:
said period of time is at least approximately 4 seconds.

47. An ignition system as set forth in claim 42 wherein said means for inhibiting include:
means for generating an engine speed signal;
temperature sensor means for generating a temperature signal when the engine is operating in excess of said predetermined temperature;
threshold generating means for generating a high threshold representative of said first predetermined speed, if said temperature signal is not present, and for generating a low threshold representative of said second predetermined speed, if said temperature signal is present;
and comparator means being adapted to receive said engine speed signal at a comparing terminal and said high and low thresholds at a reference terminal, said comparator adapted to generate said inhibiting signal if the engine speed signal is in excess of the threshold signal being applied to the reference terminal.

48. An ignition system as set forth in claim 47 wherein said delay means includes:
a capacitor connected to said reference terminal which is initially charged to said high threshold and discharges to said low threshold over said predetermined period of time when said engine temperature signal is present.

49. An ignition system as set forth in claim 48 wherein:
said capacitor has a relatively slow discharging path which is enabled when said temperature signal is present and a relatively fast charging path which is disabled when said temperature signal is present.

50. An ignition system as set forth in claim 49 which further includes:
an optically coupled device comprising a light emitting diode connected to said temperature sensor which is adapted to switch into conduction and energize said light emitting diode when said sensed engine temperature exceeds said predetermined temperature, said light emitting diode being optically coupled to a light sensitive switching device to switch said discharging path into conduction when said light emitting diode is energized.

51. An ignition system as set forth in claim 49 which further includes:

an optically coupled device comprising a light emitting diode connected to said temperature sensor which is adapted to switch into conduction and energize said light emitting diode when said sensed engine temperature exceeds said predetermined temperature said light emitting diode being optically coupled to a light sensitive switching device to switch said charging path out of conduction when said light emitting diode is energized.

52. An ignition system for an internal combustion engine of the type which has an ignition energy storage means comprising:
means for charging the ignition energy storage means;
means for discharging the ignition energy storage means;
means for detecting an overheated engine condition;
and means for reducing the operating speed of the engine by inhibiting the discharging or charging of said ignition energy storage means, said reducing means reducing the operating speed to no greater than a predetermined speed in the event that said overheated engine condition is detected while the engine is operating above said predetermined speed, and including means for gradually reducing the engine operating spaced to said predetermined speed.

53. An ignition system as set forth in claim 52 wherein:
said predetermined speed is approximately 2,500 RPM.

54. An ignition system as set forth in claim 52 wherein:
said overhead engine condition is a temperature of approximately 212° F.

55. An ignition system as set forth in claim 52 wherein:
the period of time for the gradual reduction of engine operating speed is at least approximately 4 seconds.

56. An ignition system as set forth in claim 52 wherein said means for reducing engine operating speed include:

means for generating an engine speed signal;
threshold generating means for generating a high threshold representative of a second predetermined speed, in the event that said overheated engine condition is not detected, and for generating a low threshold representative of said predetermined speed, if said overheated engine condition is detected; and comparator means being adapted to receive said engine speed signal at a comparing terminal and said high and low thresholds at a reference terminal, said comparator adapted to generate a speed reducing signal if the engine speed signal is in excess of the threshold signal being applied to the reference terminal.

57. An ignition system as set forth in claim 52 wherein said means for gradually reducing engine operating speed includes:
a capacitor connected to said reference terminal which is initially charged to said high threshold and gradually discharges to said low threshold in the event said overheated engine condition is detected.

58. An ignition system as set forth in claim 57 wherein:
said capacitor has a relatively slow discharging path which is enabled in the event said overheated engine condition is detected and a relatively fast charging path which is disabled in the event an overhead engine condition is detected.

59. An ignition system as set forth in claim 58 which further includes:
an optically coupled device comprising a light emitting diode connected to said means for detecting an overheated engine condition which is adapted to switch into conduction and energize said light emitting diode in the event an overheated engine condition is detected, said light emitting diode being optically coupled to a light sensitive switching device to switch said discharging path into conduction when said light emitting diode is energized.

60. An ignition system as set forth in claim 58 which further includes:
an optically coupled device comprising a light emitting diode connected to said means for detecting an overhead engine condition which is adapted to switch into conduction and energize said light emitting diode in the event an overheated engine condition is detected, said light emitting diode being optically coupled to a light sensitive switching device to switch said charging path out of conduction when said light emitting diode is energized.

61. An ignition system for an internal combustion engine for use in powering a boat or other water vehicle, the ignition system being of the type which has an ignition energy storage means, said system comprising:
means for charging the ignition energy storage means;
means for discharging the ignition energy storage means;
means for detecting an overheated engine condition;
means for reducing the operating speed of the engine by inhibiting the discharging or charging of said ignition energy storage means, said reducing means reducing the operating speed to no greater than a predetermined speed in the event that said overheated engine condition is detected while the engine is operating above said predetermined speed, and including means for reducing the engine operating speed to said predetermined speed at a predetermined rate thereby resulting in a gradual reduction in engine operating speed and in a gradual slowing of the boat or other water vehicle when an overheated engine condition occurs and the engine is operating above said predetermined speed.

62. An ignition system as set forth in claim 61 wherein:
said predetermined rate is substantially constant.

63. An ignition system as set forth in claim 61 wherein:
said predetermined rate causes an exponential decay of the operating speed.

64. An ignition system as set forth in claim 61 wherein:
said predetermined speed is approximately 2,500 RPM.

65. An ignition system as set forth in claim 61 wherein:
said overheated engine condition is a temperature of approximately 212' F.

66. An ignition system as set forth in claim 61 wherein:
said predetermined rate causes a gradual reduction of engine operating speed over at least approximately 4 seconds.

67. An ignition system as set forth in claim 61 wherein said means for reducing engine operating speed include:
means for generating an engine speed signal;
threshold generating means for generating a high threshold representative of a second predetermined speed, in the event that said overheated engine condition is not detected, and for generating a low threshold representative of said predetermined speed, if said overheated engine condition is detected; and comparator means being adapted to receive said engine speed signal at a comparing terminal and said high and low thresholds at a reference terminal, said comparator adapted to generate a spaced reducing signal if the engine speed signal is in excess of the threshold signal being applied to the reference terminal.

68. An ignition system as set forth in claim 67 wherein said means for gradually reducing engine operating speed include:
a capacitor connected to said reference terminal which is initially charged to said high threshold and gradually discharges to said low threshold in the event said overheated engine condition is detected.

69. An ignition system as set forth in claim 68 wherein:

said capacitor has a relatively slow discharging path which is enabled in the event said overheated engine condition is detected and a relatively fast charging path which is disabled in the event an overheated engine condition is detected.

70. An ignition system as set forth in claim 69 which further includes:
an optically coupled device comprising a light emitting diode connected to said means for detecting an overheated engine condition which is adapted to switch into conduction and energize said light emitting diode in the event an overheated engine condition is detected, said light emitting diode being optically coupled to a light sensitive switching device to switch said discharging path into conduction when said light emitting diode is energized.

71. An ignition system as set forth in claim 69 which further includes:
an optically coupled device comprising a light emitting diode connected to said means for detecting an overheated engine condition which is adapted to switch into conduction and energize said light emitting diode in the event an overheated engine condition is detected, said light emitting diode being optically coupled to a light sensitive switching device to switch said charging path out of conduction when said light emitting diode is energized.