Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AN IMPROVED UNDER THE
FLYWHEEL IGNITION SYSTEM
1 The present invention generally relates to
2 capacitive discharge ignition systems, and more specif-
3 ically relates to an improved capacitive discharge
4 ignition system for a two cylinder engine, such as a
marine engine and particularly an outboard marine engine.
6 Ignition systems for two cylinder engines of
7 the type used in outboard marine engines that are
8 typically within the range of about 20 to about 55
9 horsepower, are capacitive discharge ignition systems.
Such systems utilize the engine ~lywheel by using magnets
11 embedded within the flywheel and which pass in magnetic
12 proximity with coils for the purposa o~ generating power
13 for operating the engine and perhaps auxiliary equipment,
14 and for triggering the ignition timing for the engine.
In the past, the various coils were located under the
16 flywheel in position to magnetically interact with the~;
17 magnets, but the ignition circuitry was located in a
18 black box that was generally mounted on the side of the
19 engine and electrical leads extended to the various coils
and to the spark plugs. While such an arrangement worked
21 satisfactorily, there was always the possibility that~the
22 black box could be damaged because of its relakive ex-
23 posed location, and of course the electrical leads had to
24 be connected to the coils beneath the flywheel and to~the
spark plugs, and had to be positioned so that they would
26 not be exposed to damage.
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1 The space beneath the flywheel was not large,
2 and conventional coils have heretofore occupied nearly
3 all of this space. In this regard, the flywheel typical-
4 ly has most of its weight located at its outer periphery,
has a bridging portion extending from the periphery to
6 the hub and the hub is connected to the crankshaft of the
7 engine. The space that is available for receiving the
8 various coils is located between the periphery and the
9 hub and the interior surface of the outer periphery is
generally parallel to the crankshaft and the magnets are
11 embedded in this interior surface and adapted to magneti-
12 cally interact with the coils that may be mounted on an
13 armature plate or ignition plate assembly that is mounted
14 on the engine. The ignition plate assembly is capable of
limited rotational movement relative to the engine block,
16 for the purpose of providing ignition timing adjustments
17 in the manner that is well known in the art.
18 As previously alluded to, the space beneath the
19 flywheel was not large, and there was generally a rela-
tively large charge coil for charging the capacitor of
21 the capacitive discharge ignition system, in addition to
22 two coils for providing auxiliary power for powering
23 lighting for the boat, the charging battery and the like.
24 These coils have generally occupied approximately three
quarters of the angular space beneath the flywheel, and
26 the other quarter was occupied by the trigger coil that
27 is used to provide the proper timing for the capacitive
28 discharge ignition system.
29 While this arrangement functioned quite well,
it was necessary to provide the black box containing the
31 electrical circuitry for the ignition system at a loca-
32 tion elsewhere on the engine and have electrical leads
33 extending from the coils to the black box and then to the
34 spark plugs, as has been described.
~ccordingly, it is an object o~ the present
lL3~
1 invention to provide an improved ignition system for a
2 two cylinder engine of the foregoing typs wherein the
3 circuitry of the ignition system is packaged in a single
4 unit that can be mounted beneath the flywheel without
sacrificing the desirable Eunctional features that have
6 been otherwise provided.
7 It is another ob,ect of the present invention
8 to provide such an improved ignition system that has cir~
9 cuitry that provides overheat and overspeed protection
for the engine, with the vast bulk of the circuitry con-
11 tained within the single unit.
12 It is still another object of the present in-
13 vention to provide the trigger coil as well as a power
14 supply coil for powering the circuitry of the ignition
system within the unit, except for the charging coils,
16 thereby minimizing the number of leads and external con-
17 nectors that are needed for the ignition system.
18 A more detailed object of the invention is to
19 provide a uni~ue and improved core and bobbin assembly as
well as the trigger and power supply coils which provide
21 the desired power characteristics for both the trigger
22 and power supply signals.
23 These and other objects and advantages will
24 become apparent upon reading the ensuing speci fication,
while referring to the attached drawings, in which:
26 FIGURE 1 is a top plan view of an ignition
27 plate as~embly and illustrating the auxiliary power
28 coils, the charging coil and the unit comprising one
29 e~bodiment of the present invention;
FIG. 2 is a perspective view of the unit com-
31 prising one embodiment of the present invention;
32 FIG. 3 is a top plan view of one embodiment of
33 the present invention, shown with the protective enclo-
34 sure and filling material removed, and shown with a por-
tion of the flywheel of the engine;
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l FIG. 4 is a side Vi2W of the structure shown in
2 FIG. 3;
3 FIG. 5 is an end view of the structure shown in
4 FIG. 3;
FIG. 6 is a graph illustrating the waveform of
6 the voltage induced in the trigger coil of the present
7 invention;
8 FIG. 7 is a graph illustrating the waveform of
9 the voltage induced in the power supply coil of the
prasent invention;
11 FIG. 8 is an electrical schematic diagram of a
12 portion of the circuitry of the preferred embodiment of
13 the present invention; and,
14 FIG. 9 is an electrical schematic diagram of
another portion o~ the circuitry o~ the preferred
16 embodiment of the present invention.
17 Detailed Description
18 Broadly stated, the preferred embodiment of the
l9 present invention is directed to an improved capacitive
discharge ignition system for a two cylinder internal
21 combustion engine, such as an outboard marine engine.
22 While the preferred embodiment is for a two cylinder
23 engine, it is not limited to a two cylinder engine, and
24 other embodiments that would be useful for engines having
more than two cylinders is within the contemplation of
26 the present invention.
27 The ignition system of the present invention
28 provides overspeed and overheat protection to prevent
29 damage to the engine in the event it experiences a run-
away speed condition or becomes overheated.
31 The ignition system of the present invention is
32 adapted to be contained in a modular unit that can be
33 located beneath the flywheel of the engine, and the s~s-
34 tam includes a printed circuit board to which the vast
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1 bulk of the electrical components are mounted. The igni-
2 tion system has a power supply coil for powering the
3 ignition circuitry and a trigger coil for triggering the
4 discharge of the capacitor for producing the sparking of
the spark plugs. The power supply coil and trigger coil
6 are positioned adjacent one another and are wound on a
7 common bobbin structure and utilize a single core that is
8 configured to provide the proper characteristics for the
9 respective voltages that are needed for triggering the
ignition system and for providing power for operating the
11 circuitry of the ignition system.
12 The charging coil for charging the charge
13 capacitor for the system is not provided in the modular
14 unit, nor is the temperature switch for providing the
overheat signal for limiting the speed of the angine if
16 it has become overheated.
17 Turning now to the drawings, an ignition plate
18 assembly, indicated generally at 10, is shown in FI~. 1,
19 and includes the ignition system unit indicated generally
at 12, embodying the present invention, a charging coil
21 14 for charging the charge capacitor of the present
22 invention, and two coils 16 for providing auxiliary power
23 for lights, battery charging and the like on a boat on
24 which the ~otor may be used. The ignition system unit
12, as shown in FIGS. 1 and 2, includes a housing having
26 extensions 18 with apertures 20 therein for mounting the
27 unit 12 to the ignition plate assembly 10 with screws 22
28 or the like. The housing is preferably made of a plastic
29 or plastic-like material, such as Rynite~ made by DuPont.
After the circuitry is assembled and placed within the
31 housing, it is then filled with a potting compound,
32 preferably a polyurethane or other suitable material, to
33 seal the circuitry, protecting it from vibration, mois-
34 ture and corrosive elements.
As is shown in FIGS. 2 and 3, a magnetically
~3c~
1 conductive core, indicated generally at 24, has its outer
2 end 26 axtending through the outer curved surface 28 of
3 the housing so as to be in close proximity to a flywheel
4 30 which has magnet elements 32 and 34 embedded within
the interior face 36 of the flywheel. For the two cylin-
6 der engine e~bodiment specifically described herein, the
7 flywheel contains two sets of magnets, one set of which
8 is shown in FIG. 3. The magnet element 32 has its front
9 face comprising a north magnetic pole, while the element
34 has a front face comprising a south magnetic pole.
11 Another set of magnetic elements is provided
12 but is not shown, and is diametrically opposite those
13 shown in FIG. 3. The second set has the poles r~versed,
14 so that during rotation of the flywheel, there is an
alternation of magnetic pole transitions as the sets of
16 magnetic elements pass the core 24, so as to induce
17 opposite going voltages in the coils that are wound
18 around the core 24, as will be hereinafter described.
19 Stated in other words, if the rotation of the flywheel is
as shown by the arrow 38, the illustrated magnetic
21 elements will provide a north-to-south pole transition,
22 while the other set of magnetic elements will provide a
23 south-to-ncrth pole transition. The distance bPtween the
24 core end 26 and the surface of the magnetic elements as
they pass the core end 26 is preferably about 0.015
26 inches.
27 In accordance with an important aspect of the
28 present invention, the ignition system has a printed
29 circuit board 40 on which the electrical components are
mounted and electrically connected. A plastic bobbin 42
31 is provided on which a power supply coil 44 for powering
32 the circuitry of the ignition system is wound, as is a
33 trigger coil 46 for triggering the ignition system. Th
34 core 24 i.s shown to comprise five laminations ak the
outer end 26 and these five laminations extend to the
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1 boundary portion 48 separating the two coils 44 and 46.
2 The center lamination 50 is shortened vertically a small
3 amount, as is illustrated in FIG. 5, and extends toward a
4 hub 52 of the flywheel as shown in FIG. 3. The distance
between the end of the center lamination and khe hub 52
6 is approximately 0.25 inches, which is sufficiently close
7 to complete the magnetic circuit to the hub and to the
8 crankshaft to which the flywheel is attached. The con-
9 figuration of the core and its spacial relationship to
the magnets in the periphery of the flywhe 1 and to the
11 hub permit a magnetic circuit to be completed from the
12 magnets, through the core, to the hub of the ~lywheel and
13 to the engine crankshaft. The arrangement is different
14 from prior cores which often completed the magnetic cir-
cuit in the core itself. The arrangement disclosed here~
16 in contributes to the efficient utilization of the avail-
17 able space inasmuch as the core is generally straight,
18 slender and elongated.
19 The e~fect of having five laminations of the
core 24 extending through the power supply coil 44 and
21 only one lamination extending through the trigger coil 46
22 is to provide narrow trigger pulses for triggering the
23 discharge of the charge capacitor 72. This is shown in
24 the waveform of FIG. 6 by the positive pulses 54 which
alternate with the negative pulses 56, only one of the
26 latter of which is shown in the drawing~ The single
27 laminate saturates sooner than the multiple laminates,
28 and produces a sharper voltage pulse during pole to pole
29 transitions. The narrow pulses are separated by smallar
amplitude positive and negative maverick pulses which are
31 produced when the leading and trailing edges of each
32 magnetic element pass by the core 24. The large ampli-
33 tude pulses 54 and 56 occur as a result of a transition
34 between magnetic pole elements. The trigger coil is
preferably approximately 650 turns of number 38 gauge
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1 wire. The broader width of the five laminations section
2 results in the power supply coil 44 producing broader
3 pulses 60 and 62, which produce more power ~or powering
4 the circuitry o~ the present invention.
The circuitry o~ the preferred embodiment is
6 conveniently separated into two portions, one of which is
7 shown in FIG. 8 and other shown in FIG. 9. The circuitry
8 of FIG. 8 is located on the printed circuit board 40, and
9 the circuitry of FIG. 9 is located on a smaller printed
circuit board 64 that is connected to the circuit board
11 40 by 9 connections identified by the numbered (1-9)
12 sguare blocks in FIG. 8 and the numbered circles ~1-9) in
13 FIG. 9.
14 Turning now to the specific schematic circuitry
illustrated in FIG. 8, the charging coil 14 has its
16 opposite ends connected across a two terminal bidirec-
17 tional switching means or Sidac 64 and across a full wave
18 recti~ying bridge 66, which has its positivs terminal
19 connected to line 68 and its negative terminal connected
to ground line 70. The line 68 is connected to charging
21 capacitor 72 for charging the same during operation. A
22 diode 74 is provided for damping purposes and a resistor
23 76 connected to the charging capacitor 72 via line 68 is
24 also connPcted to ground through a stop switch for turn-
ing the engine on and off~ When the stop switch is
26 closed, the capacitor 72 is discharged, and the engine
27 will decelerate and stop.
28 As previously mentioned, the embodiment illus-
29 trated is a two cylinder engine and has ignition coils #1
and #2~ each of which is connected to a spark plug 78.
31 The capacitor 72 is discharged through either one o~ the
32 ignition coils at the appropriate time by operation of
33 the trigger coil or sensor coil 46 in conjunction with
34 associated triggering circuitry. The trigger coil 46 has
one end connected to line 80, which is connected to diode
1 82, the cathode of which is connected via a line 84 to
2 the gate of an SCR 86 and to a capacitor 88. Similarly,
3 the other end of the trigger coil 46 is connected to line
4 81, which is connected to diode 100, the cathode o~ which
is connected via a line 102 to the gate of an SCR 104 and
6 to a capacitor 106. Capacitor 88 is connected by a line
7 9o to the cathode of SCR 86 and to diode 120, as well as
8 to the ignition coil ~1, while capacitor 106 is similarly
9 connected by a line 108 to diode 110, the cathode of SCR
104 and to ignition coil ~2.
11 During operation, as one or the other of the
12 magnetic pole transitions occurs during rotation of the
13 flywheel, the trigger coil 46 provides a positive voltage
14 in either line 80 or line 81, and assuming it is line 80
by way of example, current passes through diode 82 to the
16 gate of the SCR 86 to trigger it on. It th~n cond~cts
17 current from the capacitor 72 through line 68, SCR 86 and
18 line 90 to the ignition coil #1, producing a spark in the
19 associated spark plug 78. The subseguently occurring
opposite magnetic transition results in a spark being
21 produced in the other spark plug. A biasing network com-
22 prised of capacitor 92, resistor 94, and diodes 96 and 98
23 oparate to mask the maverick pulses previously described,
24 so that the spark is produced by either spark plug at the
desired point in time.
26 To control the sp~ed of the engine in the e~ent
27 of an overspeed condition, the circuitry of FIG. ~,
28 coupled with the circuitry of FIG. 9 operate to limit the
29 speed to a lower predetermined level. While the sensing
of an overspeed condition is performed by the circuitry
31 of FIG. 9, the sensed condition produces an electxical
32 signal that is used by the circuitry of FIG. 8. If an
33 overspeed condition is detected, a high voltage level is
34 applied on line 112 that is connected to a capacitor 114
and to the gate of an SCR 116, the latter of which is
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1 connected in series with a resistor 118 across line 68
2 and line 70. When current is applied to the gate of SCR
3 116, it is switched into conduction, which discharges the
4 charging capacitor 72, thereby inhibiting sparking of
either of the spark plugs 78. As soon as the speed is
6 reduced below the critical value, the high voltage on
7 line 112 is switched low, and the SCR 116 is switched
8 open, thereby enabling normal operation~ unless and until
9 it returns to an overspeed condition.
To control the speed of the engine in the event
11 of an overheat condition, the circuitry o~ FIG. 8 and
12 FIG. 9 also cooperate to limit the speed of the engine.
13 This is also accomplished by having a high voltage on
14 line 112, which is produced when a temperature switch 122
is closed as a result of an excessive running temperature
16 for the engine
17 To produce the high voltage on line 112, the
18 circuitry of ~IG. 9 utilizes a frequency to voltage con-
19 v~rter circuit, together with comparators that produce a
high output voltage on line 112 that extends to the cir-
21 cuitry of FIG. 8. Referring to FIG. 8, the power supply
22 coil 44 has its opposite ends connected to lines 124 and
23 126, which extend to (see FIG. 9) an unregulated diode
24 bridge comprised of diodes 128 through 134, producing an
output on line 136 that is applied through capacitor 138
26 and resistor 140 to input pin 1 of an integrated circuit
27 142, which is pref~rably a frequency to voltage converter
28 circuit, model No. CS2907-D8, made by the Cherry Semicon-
29 ductor Company, although other frequency to ~oltage con-
verters can be used. The voltage level on line 136 has a
31 ripple that is a function of the voltage induced in the
32 power supply coil 44 and whose frequency is therefore
33 proportional to the speed of the en~ine. The capacitor
34 138 differentiates this ripple voltage and produces
pulses which are applied to pin 1 of the integrated
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1 circuit 142. The frequency of the pulses in the voltage
2 on pin 1 of the integrated circuit 142 is converted to an
3 analog voltage on pin 3, so that output line 144 has a
4 voltage that varies in direct proportion to the speed o~
the engine. A reference voltage is applied to pin 7 o~
6 the integrated circuit 142 by a line 146, and the circuit
7 142 compares the values of pins 3 and 7 and provides a
8 high voltage on pin 4 ancl line 148 when the voltage on
9 pin 3 exceeds that on pin 7. ~ine 148 is connected to
diode 150 which is connected to line 112, and a high
11 voltage on line 112 operates to disable the ignition as
12 previously described with respect to the circuitry of
13 FIG. 8.
14 The power for the circuitry of FIG. 9 is pro-
vided by the diode bridge and line 136 has a voltaye
16 level of approximately 10 volts. Line 136 is connected
17 to resistor 152 which is connected to line 154, which in
18 turn is connected to ground line 70 through the Zener 164
19 and to pin 7 of the integrated circuit 142 through resis-
tor 156 and line 148. The voltage level on line 154 is
21 preferably approximately 5.6 volts. The voltage level on
22 line 146 determines the speed at which the speed limiting
23 operation occurs, and the speed at which the ignition is
24 cut out is determined, in the absence of an overheat con-
dition, by the value of one of the resistors 158, 160 or
26 162 one of which is selected by use of jumpers (not
27 shown). The values of these resistors is determined to
28 provide different maximum speed conditions for different
29 sized engines that the ignition system may be installed
in. Resistors 158, 160 and 162 are preferably chosen to
31 provide ignition cutout speeds of 5200 r.p.m., 5~00
32 r.p.m. and 6100 r.p.m., respectively
33 The cutout of the ignition is also provided in
34 the event of an overheat condition, and the circuitry
indicatecl generally at 166 accorplishes this. 'his
.
.,
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1 circuit operates to cutout the ignition when the tempera-
2 ture switch 122 (FIG. 8) closes, which pulls line 168
3 low. Line 168 is connected to the base of a transistor
4 170 via a resistor 171 and diode 173, and a low on line
168 switches transistor 170 into conduction, which then
6 switches a transistor 172 into conduction. This has the
7 effect of placing a resistor 174 in parallel with one of
8 the resistors 158, 160 or 162, which changes the refer-
9 ence voltage on pin 7 of t:he integrated circuit 142 to a
lower value. This resultc; in the ignition being cut out
11 at a lower speed, and is pre~erably at approximately 2500
12 r.p.m.
13 The overheat circuit 166 remains latched, in
14 the sense that transistor 172 remains in conduction, un-
til the overheat switch opens and the motor is slowed to
16 a low spead of preferably approximately 700 to 900 r.p.m.
17 This occurs as a result of the operator slowing the en-
18 gine speed to this lower speed and the inability of khe
19 power supply coil 44 to supply sufficient power to power
the circuitry of FIG. 9. When that happens, the transis-
21 tors 172 and 170 unlatch, and the engine can then be
22 controlled to increase its speed and it can exceed the
23 ~500 r.p.mO operating speed if the overheat switch 122 is
24 open. The 700 to 900 r.p.m. value for causing the cir-
cuitry of FIG. 9 to cease operating is primarily a func-
26 tion of the size and number of turns of the power supply
27 coil 44, which is preferably about 300 turns of number 36
28 gauge wire. Removing turns of the wire would increase
29 the speed at which the circuit would cease operating~
The 700 ko 900 r.p.m. value is above ~he
31 typical idling speed of the engine of approximately 60Q
32 r.p~m., so that the engine will still operate, and will
33 not have to be restarted. A safety benefit is also
74 obtained by khe operation of the circuit. The circuikry
3 166 remains latched and controls the speed of the engine
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1 at not greater than 2500 r.p.m. speed even if the tem-
2 perature switch 122 opens, which would occur when the
3 overheat condition has dissipated. However, if the
4 operator still has the throttle at a high speed setting,
the engine will not automatically return to the high
6 speed operation. The operator must return the speed to
7 below the 700 to 900 r.p.m. speed to unlatch the circuit,
8 at which time the operator can then adjust the speed to
9 that which is desired without any "surprise".
From the ~oregoing, it should be appreciated
11 that an improved ignition system has been described which
1~ provides desireable overspeed and overheat operating
13 limits for the engine that protects the same from damage.
14 The overheat protection has the desireable feature of
automatically unlatching without shutting off the engine,
16 but only when the operating speed is manually reduced to
17 a low value. The entire ignition system is comprised of
18 a relatively few number of components and is housed in a
19 small self-contained unit that is placed under the fly-
wheel of the engine. This has the efPect of reducing the
21 number of electrical leads and connectors and also pro-
22 vides a protected environment for the circuitry.
23 Although various embodiments of the invention
24 have been shown and described in ~ull herein, there is no
intention to limit the invention to the details of such
26 embodiments. On the contrary, it is the intention that
27 the invention cover all of the various modifications,
28 alternatives, substitutions and equivalents that may fall
29 within the spirit and scope of the invention as set forth
in the appended claims.
31 Various features of the present invention are
32 set forth in the following claims.
,
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