Note: Descriptions are shown in the official language in which they were submitted.
1062326
1 The present invention relates to a contactless
ignition system for a.n internal combustion engine wherein
the same generating coils of a magneto-alternator are
used as an ignition power source as well as a.n ignition
signal power source and the output of the generating
coils is converted through two signal conversion
circuits having different impedances to provide a.n
ignition signal.
The conventional capacitor charge and discharge
type contactless ignition systems employing a magneto
generator as a capacitor charging power source as well
as an ignition signal power source are designed so that
the positive going output of a capacitor charging coil
disposed in the magneto generator is used to charge a
capacitor and at least part of the subsequently generated
negative going output is applied through a signal
conversion circuit to the gate of a thyristor for
controlling the stored cha.rge on the capacitor so that
. the thyristor is turned on and the stored charge on the
. 20 capacitor is rapidly discharged through the ignition
., coil in a discharging circuit to provide the desired
ignition spark. A disadvantage of this type of ignition
` system is tha.t the range of spark advance patterns that
~ can be designed is limited by the waveforms of generated
25 output.
Recently, particula.rly with the two-cycle
internal combustion engines of the type which is run
. at high speeds for racing purposes or the like~ there
has been a demand for an ignition system which is
. 30 capable of compa.ratively rapidly reta.rding the spark
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1062326
1 at speeds near the maximum usable number of revolutions
to improve the engine efficiency. On the other hand,
with the four-cycle internal combustion engines there
has been a demand for an ignition system which is
capable of ra.pidly a.dvancing the ignition timing at
speeds near the idling speed. There also ha.s existed a
need for an ignition system which is deslgned for other
purposes, namely, one which is designed so that at
speeds near the ma.ximum usable number of revolutions
the ignition timing is ra.pidly changed to one which
reduces the power output of the engine so as to prevent
danger due to an abnormally high speed opera.tion of
the engine. However, if the ignition timing is rapidly
retarded as mentioned earlier, when the engine is not
under loa.d, such as, when the vehicle jumps over a. gap
while running on the road, there is the danger of the
. engine speed becoming excessively high thus retarding
the ignition timing excessively and causing the engine
to fail to operate satisfa.ctorily. Also the ignition
system of the cha.ra.cteristic which a.dvances the ignition
timing of four-cycle engines is disadva.ntageous in that
there is the danger of the engine being operated at
abnormally high speeds.
Ignitions systems of the type capable of
providing the desired complicate spark advancing
characteristics are shown, for example, in the Japanese
Patent Application Publication No. 48-44698 and Japanese
: Laid Open Patent Application Publication No. 48-45721
wherein the capacitor charge controlling thysitor is
30 controlled according to the combined output of the two
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~06Z3Z6
signal coils of an alternator having different numbers of turns and adapted
for generating outputs which are in phase or out of phase with each other.
A disadvantage of this type of ignition system is that it is possible to
provide only specified positive spark advances (negative spark advances
cannot be provided) and moreover the ignition timing is controlled in ac-
cordance with the generated outputs of the signal coils per se thus making
the setting of the spark advances difficult and requiring the use of different
signal coils.
It is therefore an object of the present invention to provide a
contactless ignition system for an internal combustion engine wherein any
desired spark advance characteristic can be easily obtained.
It is another object of the invention to provide a contactless
ignition system for an internal combustion engine which is simple in con-
struction and in which both an ignition power source and an ignition signal
power source can be provided by the same generating coils of a magneto-
alternator.
It is still another object of the invention to provide a contact-
less ignition system for an internal combustion engine which is capable of
providing not only positive spark advance characteristics but also negative
spark advance characteristics, whereby at high speed operation of a two-
cycle racing internal combustion engine the ignition timing is rapidly
retarded to improve the efficiency of the engine and prevent the overspeed-
-1 ing of the engine as well.
According to the present invention then, there is provided a
contactless ignition system for an internal combustion engine comprising; a
capacitor charging coil connected to a magneto generator driven by an internal
combustion engine for generating alternating current in synchronism with ro-
tation of said internal combustion engine, said alternating current having
positive and negative half waves; a capacitor connected in series with said
capacitor charg~g coil for storing said positive half waves; an ignition
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B
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lO~;Z3Z6
coil having a primary winding connected in series with said capacitor and
a secondary winding;
a spark plug connected to said secondary winding and mounted in
said internal combustion engine; a switching element having a control gate
and connected to said capacitor, said switching element, said capacitor and
said primary winding forming a capacitor discharging circuit; a timing
signal generating circuit having an input and an output; said input being
connected to said capacitor charging coil so that said negative half wave
is supplied to said timing signal generating circuit to generate a timing
signal at said output for each of said negative half waves, said output
being connected to said control gate of said switching element, whereby
when said timing signal is supplied thereto the stored charge of said posi-
tive half waves on said capacitor is discharged through said capacitor dis-
charging circuit to produce an ignition spark at said spark plug; and a
timing signal control circuit including a transformer having a primary coil
and a secondary coil, said primary coil being connected to said capacitor
. charging coils to produce at said secondary coil an output in proportion to
- said alternating current, said secondary coil being connected to said
timing signal generating circuit through a Zener diode to supply said out-
put at said secondary coil thereto when said output exceeds a predetermined
value so as to control the timing of said timing signal, whereby the igni-
tion timing of said ignition spark can be appropriately controlled.
These and other objects ~f the invention will
B - 3a -
~062326
1 be apparent from reference to the description~ taken
in connection with the accompanying drawings.
Fig. 1 is a circuit diagram showing a first
embodiment of a contactless ignition system according
to the present invention.
Fig. 2 is a waveform diagram useful for
explaining the operation of the system shown in Fig. 1.
Fig. 3 is an ignition timing characteristic
diagram of the system shown in Fig. 1.
Fig. 4 is a circuit diagram showing a second
embodiment of the system of the invention.
Figs. 5 and 6 are ignition timing character-
istic diagrams of the system shown in Fig. 4.
Figs. 7 and 8 are circuit diagrams showing
respectively third and fourth embodiments of the system
of this invention.
Fig. 9 is a waveform diagram useful for
explaining the operation of the system shown in Fig. 8.
Fig. 10 is an ignition timing characteristic
diagram of the system shown in Fig. 8.
Figs. 11~ 12, 13 and 14 are circuit diagrams
showing fifth~ sixth, seventh and eighth embodiments
of the system of this invention.
Fig. 15 is a waveform diagram useful for
explaining the operation of the system shown in Fig. 14.
Fig. 16 is a circuit diagram showing a ninth
embodiment of the system of the invention.
Fig. 17 is a waveform diagram useful for
explaining the operation of the system shown in Fig. 16.
Fig. l& is an ignition timing characteristic
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:
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1062326
1 diagram of the system shown in Fig. 16.
Fig. 19 is a circuit diagram showing a tenth
embodiment of the system of the invention.
Fig. 20 is a waveform dia.gra.m useful for
explaining the opera.tion of the system shown in Fig. 19.
Fig. 21 is an ignition timing characteristic
diagram of the system shown in Fig. 19.
Fig. 22 is a. circuit dia.gra.m showing an
eleventh embodiment of the system of the invention.
The present invention will now be described
in greater detail with reference to the illustra.ted
embodiments.
Referring first to Fig. 1 showing a first
embodiment of the invention, numerals 1 and 2 designate
the known capacitor charging coils of a permanent
magnet type alternator (hereinafter referred to as a
magneto genera.tor)~ namely, numeral 1 designates high-
speed capacitor charging coil having a small number
: of winding turns for generating a large output at high
engine speeds and numeral 2 designa.tes a low-speed
capacitor charging coil ha.ving a large number of
winding turns for generating a. large output at low
engine speeds and the capacitor charging coils 1 and
2 are connected in series with each other. Numeral 3
. 25 designates a diode connected in series with the capacitor
:~ charging coils 1 and 2, ~ a capacitor, 5 a diode
connected in series with the capacitor 4. Numeral 6
designates an ignition coil comprising a primary winding
6a connected in pa.rallel with the diode 5 and a
secondary winding 6b connected to a spark plug 7 mounted
106Z326
1 in the cylinder head of the engine, 8 a thyristor or
a semiconductor switching element having its anode
connected to the capacitor 4, 9 a transformer comprising
a primary winding 9a connected in parallel with the low-
speed capacitor charging coil 2 through a diode 10
and a secondary winding 9b connected between the ga.te
and cathode of the thyristor 8. Numera.1 12 designates a
diode connected between the low-speed ca.pacitor charging
. coil 2 and the ground, 11 and 13 diodes connected between
the high-speed capacitor charging coil 1 and the ground.
A juncture between diodes 11 and 13 is connected to one
side of the secondary winding 9b as well as the gate
of the thyristor 8. Numeral 14 designa.tes a transformer
- comprising a primary winding 14a connected between the
diode 3 and the capacitor 4 and a secondary winding
14b connected between the gate and cathode of the
thyristor 8, 15 and 16 a Zener diode and a diode
: connected in series between the secondary winding 14b
of the transformer 14 and the gate of the thyristor 8,
17 and 18 a temperature compensating thermistor a.nd a
resistor connected in series between the gate and
cathode of the thyristor 8. In the Figure, the dots on
the transformers 9 and 14 indicate their positive
pola.rity sides.
With the construction described above, the
operation of the first embodiment will now be described.
~1 In this embodiment, the permanent magnet type alternator
(magneto generator) is of the two-pole type which
generates one cycle Or the AC output for every revolu-
tion Or the AC volta.ge is~ therefore, generated in not
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.
106Z3Z6
1 only the high-speed capacitor charging coil 1 having a
rela.tively small number of winding turns and adapted
for chiefly cha.rging the capacitor 4 at high engine
speeds but also the low-speed capacitor charging coil
2 having a relatively large number of winding turns and
adapted for chiefly charging the capacitor 4 at low
engine speeds. Consequently, at low engine speeds,
when a. positive going voltage begins to develop in
the capacitor charging coils 1 and 2, the capa.citor 4
is charged as shown by a solid line in (a) of Fig. 2
by current flowing from the capacitor charging coils
1 and 2 through a circuit comprising the low-speed
capacitor cha.rging coil 2, the high-speed capacitor
charging coil 1, the diode 3, the primary winding 14a
. . 15 of the transformer 14, the capa.citor 4, a parallel
circuit of the diode 5 and the primary winding 6a, the
ground and the diode 12 in this order. In Fig. 2,
the abscissa. represents the rotational angle ~ of
the ma.gneto generator (i.e. the engine). Supposed that
the voltage across the secondary winding 14b is
measured under no-load conditions, the voltage shown
by a solid line in (c) of Fig. 2 appears thereacross.
. When the negative going voltage of the a.bove no-load
~ voltage exceeds a predetermined value at which the
Zener diode 15 becomes conductive, the voltage shown
by a solid line in (d) of Fig. 2 appears across the
. secondary winding 14b and thereby the voltage shown by
the broken line L in (b~ of Fig. 2 appears between the
gate and cathode of the thyristor 8. However, this
voltage has no influence on conduction of the thyristor
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lO~Z3Z6
1 8 due to a reverse bias voltage in the negative direction.
When the generated voltage in the capa.citor cha.rging
coils 1 and 2 reverses its direction from the positive
to the negative, the generated voltage in the low-speed
capacitor charging coil 2 is short-circuited through
the prima,ry winding 9a of the transformer 9 and the
diode 10 and the output of the secondary winding 9b
of the transformer 9 ca.uses the volta.ge between the
gate and cathode of the thyristor 8 to become as shown
by a solid line in (b) of Fig. 2. W~len the gate voltage
of the thyristor 8 attains the trigger level of the
: thyristor 8~ the thyristor 8 is turned on and the stored
charge on the capacitor 4 is discharged through a.
~- circuit comprising the capacitor 4, the thyristor 8,
the ground and the prima.ry winding 6a of the ignition
coil 6, resulting in a generation of a high voltage in
the secondary winding 6b of the ignition coil 6, io
thereby cause an ignition spa.rk at the spa.rk plug 7.
The diode 5 serves to keep the current flow in the
; 20 primary winding 6a of the ignition coil 6 to elongate
the arc duration of the ignition spark at the spark
plug 7. At high engine speed operation, the capacitor
4 is charged as shown by a dot-and-dash line in (a) of
Fig. 2 chiefly by a current flowing from the high-
speed capacitor charging coil 1 through a circuit
comprising the high-speed capacitor charging coil 1,
. the diode 3, the primary winding 14a of the transformer
', 14~ the capa.citor 4~ a pa.rallel circuit of the diode 5
and the primary winding 6a of the ignition coil 6,
the ground~ the diode 13 and the diode 11. During this
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10623Z6
1 charging period, the output generated in the secondary
winding 14b of the tra.nsformer 1~ under no-load
conditions becomes as shown by a dot-and-da.sh line in
(c) of Fig. 2, whereas the output generated under load
conditions becomes as shown by a dot-and-dash line in
(d) of Fig. 2. When the output of the capacitor
charging coils 1 and 2 reverses~ the secondary winding
9b generates the output volta.ge as shown by a. dot-and-
dash line in (b) of Fig. 2 when messured under no-load
conditions. However, a pa.rt of the negative half wave
of the output voltage at the secondary winding 1
shown by the dot-and-dash line in (d) of Fig. 2
overlaps a part of the output voltage at the secondary
winding 9b, whereby the output voltage shown by a.
broken line H in (b) of Fig. 2 is finally supplied to
the gate of the thyristor 8, thus retarding the ignition
timing In this case, depending on the Zener voltage
value (breakdown voltage) of the Zener diode 15 and
.,
the number of diode(s) 16 used, the ignition timing at
high engine speeds may be varied as shown by the curves
a through e in Fig. 3. For instance, in Fig. 3 the
curve a indicates the ignition timing characteristic
obtained when the Zener volta.ge of the Zener diode 15
. is 12 volts and the single diode 16 is.used, while the
curves b, c, d and e are respectively the ignition timing
characteristics when the Zener voltage of the Zener
diode 15 is 6 volts and using three units, two units and
single unit of the diode 16, respectively, and the
ignition timing characteristic obtained when the Zener
:j 30 diode 15 is eliminated and the single diode 16 is used.
.
10623Z6
l Further, the curve f indicates the ignition timing
characteristic obtained when the seconda.ry winding
14b of the transformer 14 is open-circuited.
Referring to Fig. ~, there is illustrated
a second embodiment of the invention which differs from
the first embodiment of Fig. l in that the priminary
winding 9a of the transformer 9 is connected in series
with the prima.ry winding 14a of the transformer 14 wnich
çontrols the ignition timing at high engine speeds,
the resulting series circuit is connected in parallel
with the capacitor charging coils 1 and 2 and a
resistor 40 is connected between the secondary winding
14b of the transformer 14 and the gate of the thyristor
8. In this second embodiment, the output of the high-
speed capacitor charging coil 1 having a. relativelysmall number of winding turns is ma.inly a.pplied to
the transformers 9 and 14 so that the degree of spark
advance at low engine speeds can be increased and the
degree of spark retard at intermediary engine speeds
can be decreased than in the case of the first embodi-
ment. Further, since, as shown in (e~ of Fig. 2, the
secondary output of the transformer 14 in the second
-i embodiment lags in phase behind the secondary output
: of the transformer 14 of the first embodiment shown in
(d) of Fig. 2 so that the relatively early rising
portion of the waveform is used to produce an ignition
: signal as shown in (f) of Fig. 2 and the resulting
ignition timing characteristic shows tha.t if the Zener
voltage is decreased by the Zener voltage of the Zener
: 30 diode 15, it is possible to cause the spark retard to
- 10 --
.. . .
.:
1062326
1 commence at lower engine revolutions as shown in Figs.
5 and 6. Namely, in Fig. 5 showing the ignition timing
chara.cteristics obtained without the resistor 40 of
the embodiment shown in Fig. 4, the curve a indicates
5 the ignition timing characteristic obta.ined when the
secodndary winding 14b of the transformer 14 is open-
circuited, the curves b, c, d, e and f indicate the
ignition timing characteristics obta.ined when the Zener
volta.ge of the Zener diode 15 is selected 30, 24, 18,
10 12 and 6 volts~ respectively, and the curve z indicates
the ignition timing characteristic obtained when the
Zener diode 15 is elimina.ted and the diode 16 alone is
connected to the secondary winding 14b of the tra.nsform2r
14. In Fig. 6, the curves a and b are the ignition
15 timing characteristics when the Zener voltage of the
Zener diode 15 is selected 12 and 18 volts~ respectively,
and the resistor 40 is not used, the curves a' and a"
are the ignition timing characteristics when the Zener
voltage of the Zener diode 15 is 12 volts and the
20 resistance va.lue of the resistor 40 is selected 180
and 470 ohms, respectively, and the curves b' and b"
- are the ignition timing characteristics when the Zener
voltage of the Zener diode 15 is selected 18 volts and
the resistance value of the resistor 40 is selected 180
25 and 470 ohms, respectively. The broken line curve c
in Fig. 6 is the ignition timing chara.cteristic when
the secondary winding 14b of the tra.nsformer 14 is
open-circuited. On the other hand, in (e) of Fig. 2
the solid line is the no-load output voltage generated
30 in the seconda.ry winding 14b of the transformer 14 at
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1 low engine speeds~ the dot-and-da.sh line is the no-load
output voltage generated in the secondary winding 14b
of the transformer 14 a.t high engine speeds, and the
broken line is the output voltage of one direction
genera.ted in the secondary winding 14b of the transformer
14 at load, high engine speed operation with its waveform
having the same shape as the no-load output voltage
shown by the dot-and-dash line since the output voltage
of the other direction at load is blocked by the diode
: 10 16. In (f) of Fig. 2, the solid line is the voltage
applied between the gate and cathode of the thrystor 8
at low engine speeds, the dot-and-da.sh line is the
voltage applied between the gate and cathode of the
thyristor 8 at high engine speeds with the seconda.ry
winding 14b of the transformer 14 being open-circuited,
and the broken line H is the voltage applied between
the gate and cathode of the thyristor 8 at high engine
speeds with the secondary winding 14b of the transformer
14 being connected as shown in Fig. 4 and in addition
to tha.t shown by the broken line H the voltage of the
same waveform as the voltage indica.ted by the dot-and-
dash line and generated with the secondary winding
14b of the transformer 14 being open-circuited is
applied between the gate and ca.thode of the thyristor 8.
. 25 Referring now to Fig. 7, there is shown a
third embodiment of the invention which differs from
; the first embodiment of Fig. 1 in that instead of using
the ignition transformer 9, the gate of the thyristor
8 is directly connected to the ca.thode of the diode 12
. 30 and the non-charging direction output from the low-speed
- 12 _
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1 capa.citor cha.rging coil 2 is directly applied across
the gate and cathode of the thyristor 8 through the
diode 11. The third embodiment operates practically
in the same manner as the first embodiment.
Fig. 8 is a fourth embodiment of the invention
which differs from the second embodiment of Fig. 4 in
that the polarities of the seconda.ry winding 14b of
the transformer 14, the Zener diode 15 and the diode 16
are reversed and the resistor 40 is eliminated. The
opera.tion of the fourth embodiment is as follows.
One cycle of the AC voltage is generated for every
revolution of the engine in the high-speed capacitor
charging coil 1 having a relatively small number of
winding turns and adapted for charging the capacitor
4 chiefly a.t high engine speeds and the low-speed
capacitor charging coil 2 having a relatively large
number of winding turns and adapted for cha.rging the
capacitor 4 chiefly a.t low engine speeds. With the
engine operating at a low speed~ when a positive going
voltage begins to develop in the capacitor charging
coils 1 and 2, the capacitor 4 is cha.rged a.s shown by
the solid line in (a) of Fig. 9 by current flowing
from the capa.citor cha.rging coils 1 and 2 through a
circuit comprising the low-speed capacitor charging
coil 2, the high-speed capacitor charging coil 1,
the diode 3, the capacitor -4, a parallel circuit of the
diode 5 and the prima.ry winding 6a of the ignition coil
6 and the ground. When the generated voltage in the
capacitor charging coils 1 and 2 reverses its direction
from the positive to the negative~ the output of the
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1 low-speed capacitor charging coil 2 is short-circuited
through the diode 11, however the output of the high-
speed capa.citor cha.rging coil 1 is short-circuited
through a circuit comprising the high-speed capacitor
charging coil 1~ the low-speed capacitor charging coil
2, the ground, the primary winding 9a of the transformer
9, the primary winding 14a of the transformer 14 and
the diode 10. Consequently, the output shown by the
solid line in (b) of Fig. 9 is generated in the secondary
winding 9b of the transformer 9 a.nd it is then applied
across the gate and cathode of the thyristor 8. When
this occurs, the thyristor 8 is turned on and the stored
ch&rge on the capacitor 4 is discharged through a
circuit comprising the capacitor 4, the thyristor 8,
the ground and the prima.ry winding 6a of the ignition
coil 6 thus generating a. high volta.ge in the secondary
: winding 6b of the ignition coil 6 and causing an
ignition spark at the spa.rk plug 7. On the other hand,
; although the output shown by the solid line in (c) of
Fig. 9 is generated in the secondary winding 14b of
the transformer 14 simultaneously with the generation
of the output in the secondary winding 9b of the trans-
former 9~ the magnitude of this output is small when
.~ the engine is operating at a low speed and consequently
. 25 the Zener diode 15 is not rendered conductive with the
result that no current flows through a circuit comprising
the secondary winding 14b of the transformer 14~ the
Zener diode 15, the diode 16, and the gate and cathode
of the thyristor 8, and thereby the thyristor 8 is
not affected by the output a.t the secondary winding 14b
- 14 _
106Z3Z6
1 in any way. The cha.rging of the capacitor 4 at high
engine speeds is accomplished by current flowing from
the high-speed capacitor cha.rging coil 1 through a
circuit comprising the high-speed capa.citor charging
coil 1, the diode 3, the capacitor 4, a parallel
circuit of the primary wlnding 6a of the ignition coil
6 and the diode 5, the ground a.nd the diode 11 thus
charging the capacitor 4 as shown by the dot-and-dash
line in (a) of Fig. 9.
When the output of the capacitor charging
coils 1 and 2 reverses eventually, the voltage shown
by the dot-and-da.sh line in (b) of Fig. 9 would be
applied across the gate and cathode of the thyristor 8
by the output from the secondary winding 9b of the
transformer 9 in the similar manner as at low engine
speeds when the secondary winding 14b of the transformer
14 is open-circuited. However, as the engine speed
increases, the seconda.ry output of the transformer
14 increases as shown by the broken line in (c) of
Fig. 9 and becomes sufficiently la.rge to render the
Zener diode 15 conductive, and thereby current begins
to flow from the secondary winding 14b through a circuit
comprising the secondary winding 14b of the transformer
. 14, the Zener diode 15, the diode 16, a parallel
circuit of the gate and cathode of the thyristor 8
and the secondary winding 9b of the transformer 9 and
. to the ground. Consequently~ the combined input applied
across the gate and cathode of the thyristor 8 becomes
higher as a result of a combination of the output of
the transformer 9 and the output of the transformer 14
~06Z326
1 as shown by the broken line in (b) of Fig. 9, whereby
the firing position of the thyristor 8 is advanced,
namely, the ignition timing is advanced. Similarly
as at low engine speeds, the conduction of the
thyristor 8 causes an ignition spark at the spark plug
7. The resulting ignition timing characteristics will
become a.s shown in Fig. 10.
In Fig. 10, the curve a is the ignition
timing characteristic when the seconda.ry winding 14b
of the transformer 14 is open-circuited, the curves
- b, c, d and e show respectively the ignition timing
chara.cteristics when the Zener voltage of the Zener
. diode 15 is selected, 12, 6, 4 and 2 volts, respectively,
. and the curves f and ~ demonstrate the ignition timing
15 characteristics when eliminating the Zener diode 15 and
instead employing two units and single unit of the diode
16, respectively. As noted from Fig. 10, the spark
advance can be freely selected depending on variations
of the Zener diodes.
Fig. 11 illustrates a fifth embodiment of the
invention wherein the transformer 9 is replaced with
a signal conversion circuit 30 including resistors
31, 32, 33 and 34~ a Zener diode 35, a thyristor 36
and a capa.citor 37. In this fifth embodiment, when -
a negative going output is generated in the low-speed
capacitor charging coil 2, current flows from the low-
speed capacitor charging coil 2 through a circuit
comprising the low-speed capa.citor charging coil 2,
the resistors 34 and 33, the capacitor 37, the diode 10
30 and the prima.ry winding 14a of the transformer 14 and
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1 thus the capacitor 37 is charged in the polarity
shown. When the voltage across the capacitor 37
(which is a.pplied across the Zener diode 35) becomes
higher than a predetermined value, the Zener diode 35
is rendered conductive so that the thyristor 36 is
turned on and the stored charge on the ca.pacitor 37 is
discharged through the capacitor 37, the resistor 33,
the gate and cathode of the thyristor 8 and the thyristor
36 thus turning on the thyristor 8. As mentioned
earlier~ volta.ge is genera.ted in the secondary winding
14b of the tra.nsformer 14 by the current flowing
through the primary winding 14a. during the charging of
the capa.citor 37. While the magnitude of this voltage
is sma.ll at low engine speeds thus having no effect on
the control of the thyristor 8~ when the engine is
operating at an intermediate speed~ voltage genera.ted
in the secondary winding 14b of the transformer 14
becomes high er than the Zener voltage of the Zener diode
15 to render the Zener diode 15 conductive resulting in
that positive voltage generated a.t the secondary winding
~b is app~ied to a junction point o~ the capacitor
37 and the cathode of the thyristor 36, and thereby
the voltage across the terminals of the capacitor 37
is decreased by an amount corresponding to this applied
positive voltage. When this occurs, the rate of charging
the capacitor 37 is decreased so that the firing timing
of the thyristor 8 at the intermediary engine speed is
retarded.
Fig. 12 illustrates a sixth embodiment of
the invention wherein the negative going output of the
- 17 -
106Z3Z6
1 low-speed capacitor charging coil 2 is used to produce
an output in the secondary winding of the transformer
9 and the nega.tive going output of the high-speed
capacitor charging coil 1 is used to produce an output
in the seconda.ry winding of the transformer 14.
Fig, 13 illustrates a seventh embodiment
of the invention wherein the capacitor charging coils
1 and 2 are respectively connected through diodes 3a
and 3b to the capacitor 4, Each of the negative going
ha.lf cycles of the outputs of the ca.pa.citor charging
coils 1 and 2 is applied to the same prima.ry winding
9a of the transformer 9 respectively through the Zener
diode 10 and a circuit of the resistor 40, the Zener
diode 15 and the diode 16, In this seventh embodiment,
the capacitor 4 is cha.rged through the diodes 3a and
3b with the positive going outputs of the capacitor
charging coils 1 and 2, At low engine speeds only the
negative going output of the low-speed capacitor charging
coil 2 is applied to the transformer 9 to control the
thyristor 8 because the Zener diode 15 is not ma.de into
: conduction. At intermediate engine speeds the Zener
diode 15 is rendered conductive to apply to the
transformer 9 the both negative going outputs of the
` capacitor charging coils 1 and 2 resulting in control
', 25 o~ the thyristor 8, and in this way the ignition timing
is advanced.
Fig. 14 illustrates an eighth embodiment of
the invention wherein the transformer 14, the diodes
-10 and 19~ the Zener diode 15~ a thyristor 16a and a
resistor 41 constitutes.a signa.l conversion circuit~
- 18
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1 whereby when the voltage genera.ted in the secondary
winding 14b of the transformer 14 exceeds a predetermined
value for rendering the Zener diode 15 conductive, the
thyristor 16a is turned on and the Zener diode 15 and
the resistor 41 are short-circuited to thereby more
rapidly retarding the ignition timing a.t high engine
speeds. The ignition timing cha.ra.cteristics obtained
by this embodiment are shown in Fig. 15, namely,
assuming that the curves a and b are the ignition timing
characteristics when the Zener voltage of the Zener
diode 15 is selected 12 and 18 volts, respectively, and
the resistor 40 is elimina.ted, the curves a', a", b'
and b'' are the ignition timing characteristics when
the resistance value of the resistor 40 is selected
15 180 a.nd 470 ohms, respectively. The broken line
curve is the ignition timing cha.racteristic when the
secondary winding 14b of the transformer 14 is open-
circuited.
Fig. 16 illustrates a ninth embodiment of
the invention which differs from the second embodiment
. of Fig. 4 in that a series circuit of a resistor 21
and a thyristor 20 is connected across the terminals of
the seconda.ry winding 14b of the transformer 14~ a
series circuit of a diode 22 and a Zener diode 23 is
further connected between the gate of the thyristor 20
and the secondary winding 14b of the transformer 14 and
the resistor 40 is eliminated.
With the construction described a.bove, the
system of this embodiment is one which employs a two-
pole permanent magnet type alternator for generating
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1 one cycle of the AC output for every one revolution of
the engine (i.e. the generator).
In operation, one cycle of the AC voltage is
genera.ted for every one revolution of the engine in the
high-speed capacitor charging coil 1 having a. relatively
small number of winding turns a.nd adapted far charging
the capa.citor 4 chiefly a.t high engine speeds and the
low-speed ca.pacitor charging coil 2 ha.ving a. relatively
large number of winding rurns and adapted for cha.rging
the ca.pa.citor 4 chiefly at low engine speeds. With the
engine operating at a low speed, when a positive going
volta.ge starts to develop in the ca.pacitor cha.rging
coils 1 and 2, current flows from the capacitor charging
coils 1 and 2 through a circuit comprising the low-speed
capacitor charging coil 2, the high-speed capacitor
; charging coil 1, the diode 3~ the capa.citor 4, a parallel
circuit of the diode 5 and the prima.ry winding 6a. of
the ignition coil 6 and to the ground, whereby the
capacitor 4 is charged a.s shown by the solid line in (a.)
of Fig. 17. In Fig. 17, the abscissa represents the
; rotationa.l angle ~ of the ma.gneto generator i.e. the
engine. When the generated volta.ge in the capacitor
charging coils 1 and 2 reverses its direction from the
positive to the nega.tive, the generated voltage in the
low-speed capacitor charging coil 2 is short-circuited
by the diode 11, while the-generated ou~put of the
hlgh-speed ca.pa.citor charging coil 1 is short-circuited
through a circuit comprising the low-speed capacitor
: charging coil 2, the ground~ the primary winding 9a
of the transformer 9, the prima.ry winding 14a of the
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1 transformer 14 and the diode 10 so tha.t the output is
generated at the secondary winding 9b of the transformer
9, which would be applied a.cross the gate and ca.thode
of the thyristor o as shown by the solid line in (c)
of Fig. 17. At the low-speed running of the engine,
the output from the seconda.ry winding 14b of the trans-
former 14 is small as shown by the solid line in (b) of
Fig. 17, and lower than the Zener volta.ge of the Zener
diode 15, and therefore, it has no effect on the ignition
position. When the gate voltage of the thyristor 8
eventually rea.ches the trigger level (TL) of the thyristor
8, the thyristor 8 is turned on and the stored charge on
! the ca.pacitor 4 is discharged through a. circuit comprising
the capacitor 4, thyristor 8, the ground and the primary
winding 6a of the ignition coil 6 thus generating a high
voltage in the seconda.ry winding 6b of the ignition
coil 6 and causing an ignition spark at the spa.rk plug
- 7. In this embodiment, the diode 5 serves to maintain
, the current flow through the primary winding 6a of the
ignition coil 6 to elongate the arc duration of the
: ignition spark at the spark plug 7. When the running
: speed of the engine is increased, the charging of the
capacitor 4 is accomplished chiefly by current flowing
from the high-speed capacitor charging coil 1 by way
, 25 of a circuit comprising the high-speed capacitor
. charging coil 1, the diode 3~ the capa.citor 4, a parallel
i circuit of the diode 5 and the primary winding 6a of
the ignition coil 6~ the ground and the diode 11, as
shown by the dot-and-dash line in (a) of Fig. 17.
30 When the output from the capacitor charging coils 1
~ .. .
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.
, ' '
106Z326
1 and 2 reverses its direction, the no-load output of
the transformer 14 becomes higher than the Zener voltage
of the Zener diode 15 as shown by the dot-and-dash
line in (b) of Fig. 17 and consequently the voltage
shown by the broken line (which shows the voltage under
the load) in (b) of Fig. 17 is applied across the gate
and cathode of the thyristor 8 from the transformer 14.
Thus, when the output from the capacitor charging coils
1 and 2 reverse its direction, while the voltage shown
by the dot-and-dash line in (c) of Fig. 17 is applied
across the gate and cathode of the thyristor 8 by the
output of the secondary winding 9b of the transformer
9 when the secondary winding 14b of the transformer 14
is open-circuited (under no-load conditions), the
rising portion of the applied voltage is cancelled
as shown by the broken line H in (c) of Fig. 17 by
the output of the transformer 14 generated as shown
by the broken line in (b) of Fig. 17 when the secondary
winding 14b is connected and in this way the ignition
timing is retarded.
When the engine speed increases further so that
the service engine speed is exceeded, the Zener diode 23
is rendered conductive by the positive going voltage of
`the output from the secondary winding 14b of the
~,25 transformer 14 shown in (b) of Fig. 17, resulting in
that the thyristor 20 is turned on by the current flowing
~;from the trnasformer 14 through a circuit comprising the
Zener diode 23~ the diode 22, the gate and cathode of
the thyristor 20 and the ground and the output of the
secondary winding 14b of the transformer 14 which is
., .
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106Z326
1 directed in one direction is short-circuited through
a circuit comprising the resistor 21 and the thyristor
20. This short-circuiting reta.rds the phase of the
output from the transformer 14 and the output of the
transformer 1~ in the opposite direction is also affected
thus delaying the phase of this oppositely directed
output and also decreasing its ma.gnitude. Consequently,
the signa.l volta.ge shown by the dot-and-dash line in (c)
of Fig. 17 is cancelled in a. reduced degree by the output
of the transformer 14 and the resulting ignition timing
characteristic becomes as shown in Fig. 18 depending on
the resistance va.lue of the resistor 21. In Fig. 18, as
for example, the curve (e) is the ignition timing
characteristic when there is no rapid spark retard
(when the transformer 14 is eliminated), the curve (d)
is the rapid spark retard ignition timing chara.cteristic
when the transformer 14 is used, the curves (a), (b)
and (c) are the ignition timing characteristics when
the high-speed control means for cancelling rapid spark
retard is used and the resistance value of the resistor
21 is selected high (100 ohms), medium (32 ohms) and
zero, respectively. The operating position P (rpm)
of the high-speed control means may be adjusted as
desired depending on the Zener volta.ge of the Zener
diode 23.
Fig. 19 illustrat.es a tenth embodiment of the
invention which differs from the ninth embodiment of
Fig. 16 in that the polarities of the secondary winding
14b of the transformer 14, the Zener diode 15 and the
diode 16 are reversed and the ca.thode of the Zener diode
: - 23 -
-- -- , .
106Z326
1 23 is connected to the ground~ The tenth embodiment
operates as follows. One cycle of the AC voltage is
genera.ted for every one revolution of the engine in
the high-speed capacitor cha,rging coil 1 having a
relatively small number of winding turns and ada.pted
for charging the ca.pa.citor 4 chiefly a.t high engine
speeds and the low-speed capa.citor charging coil 2
having a relatively large number of winding turns
and adapted for cha.rging the capacitor 4 chiefly
at low engine speeds. When the engine is operating
at a low speed, current flows from the capacitor charging
coils 1 and 2 through a. circuit comprising the low-
speed capa.citor cha.rging coil 2, the high-speed capacitor
charging coil 1, the diode 3, the capacitor 4, a
parallel circuit of the diode 5 and the primary winding
: 6a of the ignition coil 6 and the ground and the
capacitor 4 is charged a.s shown by the solid line in
- (a) of Fig. 20. When the generated voltage in each of
the capacitor charging coils 1 and 2 reverses its
direction from the positive to the nega.tive, the output
of the low-speed ca.pacitor charging coil 2 is short-
: circuited by the diode 11. On the other hand, the
' output of the high-speed ca.pa.citor charging coil 1 is
:~ ' short-circuited through a circuit comprising the high-
speed capa.citor charging coil 1~ the low-speed capa.citor
charging coil 2~ the ground, the primary winding 9a of
'~ the transform 9, the primary winding 14a of the transform
.' 1~ and the diode 10 and the output shown by the solid
line in (b) of Fig. 20 is generated in the secondary
winding 9b of the transformer 9 a.nd applied across the
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1 gate and ca.thode of the thyristor 8. When this applied
voltage becomes higher than the trigger level (TL) of
the thyristor 8, the thyristor 8 is turned on and
the stored charge on the capacitor 4 is discharged
through a. circuit comprising the ca.pacitor 4, the
thyristor 8, the ground and the primary winding 6a of
the ignition coil 6, thus generating a high voltage
in the seconda.ry winding 6b of the ignition coil 6
and causing an ignition spark at the spark plug 7.
On the other hand, though the output shown by the solid
line in (c) of Fig. 20 is generated simultaneously
with the generation of the output in the secondary
winding 9b of the transformer 9, the magnitude of this
output is small at low engine speeds and consequently
the Zener diode 15 is not rendered conductive and the
output of the transformer 14 ha.s no effect on the
~; thyristor 8. The charging of the capacitor 4 at high
engine speeds is accomplished chiefly by current flowing
from the high-speed capacitor cha.rging coil 1 through . .
a circuit comprising the high-speed capacitor cha.rging
coil 1~ the diode 3, the capacitor 4~ a parallel circuit
of the diode 5 and the prima.ry winding 6a. of the ignition
. coil 6~ the ground and the diode 11 and the capa.citor 4
is charged as shown by the dot~and-dash line in (a) of
: 25 Fig. 20. When the output from the capa.citor charging
~ coils 1 and 2 reverses its direction~ similarly a.t low
~;; engine speeds, the voltage applied a.cross the ga.te and
cathode of the thyristor 8 by the output Or the secondary
winding 9b of the tra.nsform 9 becomes as shown by the
dot-and-dash line (b) of Fig. 20 when the secondary
- 25 -
106Z326
1 winding 14b of the transformer 14 is open-circuited,
whereas the no-load secondary output of the transformer
14 becomes sufficiently high as shown in (c) of Fig. 20
by the dot-and-dash line (the secondary output at load
is shown by the broken line) so that the Zener diode
15 is rendered conductive and a current flows from the
secondary winding 14b through a circuit comprising the
secondary winding 14b of the transformer 14, the diode
16, the Zener diode 15, the gate and cathode of the
thyristor 8 and the ground. Consequently, the combined
input applied across the gate and cathode of the thyristor
8 consists of the combination of the output of the
transformer 9 and the output of the transformer 14 as
shown by the broken line in (b) of Fig.. 20 and the firing
position of the thyristor 8 is advanced, namely, the
ignition timing is advanced. And, similarly at low
engine speeds, the thyristor 8 is turned on and an
ignition spark is caused at the spark plug 7.
When the engine speed increases further, the
Zener diode 23 is rendered conductive in response to the
negative going voltage in the secondary winding 14b of the
transformer 14 so that the th~-ristor 20 is turned on by
the current flowing from the secondary winding 14b of the
` transformer 14 through a circuit comprising the ground~
the Zener diode 23, the diode 22 and the gate and cathode
of the thyristor 20 and the negative going output from the
secondary winding 14b of the transformer 14 is short-
circuited through the resistor 21 and the thyristor 20.
. This short-circuiting retards the phase of the negative
: 30 going output of the transformer 14 thus also delaying the
- 26 -
,
,
10623Z6
1 phase of the positlve going output of the transformer 14
and decreasing its magnitude. Consequently, the spark
advancing signal voltage advanced in phase and shown by
the broken line in (b) of Fig. 20 is reduced and the
resulting timing lgnition characteristic will become as
shown in Fig. 21. In Fig. 21, as for example, the curve
(a) is the ignition timing characteristic when the trans-
former 14 is eliminated, the curve (b) is the ignition
timing characteristic when the transformer 14 is used and
the curve (c) is the ignition timing characteristic when
the cancelling high-speed control means is used. Further,
the inflection point P may be adjusted as desired depend-
ing on the Zener voltage of the Zener diode 23.
While, in the ninth and tenth embodiments
described above, only the single high-speed control
means is used in one of the signal conversion circuits,
it is of course possible to provide more complex
ignition timing characteristics by providing such high-
` speed control means in each of the signal conversion
circuits or by using two or more high-speed control
` means which are operable at different engine speeds.
Further, while, in the above-described ninth
and tenth embodiments, of the output generated in the
secondary winding 14b of the transformer 14 the negative
going output which is not utilized for controlling the
gating of the thyristor 8 is short-circuited through the
resistor 21 and the thyristor 20 included in the high-
speed control means, the positive going portion of the
output from the secondary winding 14b of the transformer
14 which is not utilized for controlling the gating of
- 27 -
106Z3Z6
1 the thyristor 8 may be short-circuited through the
resistor 21 a.nd the thyristor 20 included in the high-
speed control means.
Still further, while in the above-described
ninth and tenth embodiments, the Zener diode 23 in the
high-speed control means detects the negative going
portion of the output from the secondary winding 14b
of the transformer 14 which is not utilized for
controlling the gating of the thyristor 8, the positive
going portion of the output from the secondary winding
14b of the transformer 14 which is utilized for control-
ling the ga.ting of the thyristor 8 may be detected
by the Zener diode 23 in the high-speed control means
or alternately the positive or negative going output of
the capacitor charging coils 1 and 2 may be detected
by the Zener diode 23 in the high-speed control means.
Fig, 22 illustrates an eleventh embodiment
of the invention wherein a generating coil 1 of a
ma.gneto generator is also utilized as the primary
winding of an ignition coil 6, a series circuit
including a diode 3, primary windings 14a and 9a of
~ transformers 14 and 9 and a transistor 8a constituting
: a semiconductor switching element is connected across
the terminals of the generating coil 1, the cathode
of the diode 3 is connected to the ground through a
resistor 41 and a thyristor 8, the anode of the
thyristor 8 is connected to the base of the transistor
8a through a diode ~3, a parallel circuit including a
secondary winding 9b of the transformer 9, a resistor
42 and a diode 13 is connected between the gate and
- 28 -
~06Z326
1 cathode of the thyristor 8, and a series circuit
including a resistor 40, a diode 16, a Zener diode 15
and a secondary winding 14b of the transformer 14 is
connected between the gate and cathode of the thyristor
8. With this eleventh e~bodiment, when a positive
going voltage is generated in the generating coil 1,
a base current flows to the transistor 8a from the
generating coil 1 through a circuit comprising the
generating coil 1, the diode 3, the resistor 41, the
diode 43, the base and emitter of the transistor 8a
and the ground and the transistor 8a is turned on.
This causes the flow of current from the generating
coil 1 through a circuit comprising the diode 3, the
primary winding 14a of the transformer 14, the primary
winding 9a of the transformer 9, the collector and
emitter of the transistor 8a and the ground. The
output then generated in the secondary winding 9b
of the transformer 9 is applied between the gate and
cathode of the thyristor 8 so that when this applied
voltage exceeds the trigger level of the thyristor 8,
the thyristor 8 is turned on and the base and emitter
section of the transistor 8a is short-circuited. When
this occurs, the transistor 8a is turned off and the
current flowing in the generating coil 1 is rapidly
interrupted thus generating a high voltage in the
secondary winding 6b Or the ignition coil 6 whose
primary winding is comprised of the generating coil 1
and causing an ignition spark at the spark plug. In
this case, although an output is also generated in the
secondary winding 14b o~ the transformer 14 which is
- 29 -
!
.
, '' , ' . ' ~ ' '~ . ' .
106Z3Z6
1 inserted in the closed circuit of the generating coil
1, the output voltage generated in the secondary
winding 14b at low engine speeds is small and the
Zener diode 15 is not rendered conductive. As a
result~ the thyristor 8 is controlled only by the
output generated in the secondary winding 9b of the
transformer 9 and consequently the ignition timing
characteristic is gradually advanced in accordance
with the engine speed or rpm. When the engine speed
exceeds a predetermined value so that the output generated
in the secondary winding 14b of the transformer 14
becomes higher than the Zener voltage of the Zener
diode 15, the Zener diode 15 is rendered conductive and
the generated output in the secondary winding 14b of
the transformer 14 is applied in the direction opposite
to the secondary winding 9b of the transformer 9 to
cancel the generated output in the secondary winding
9b. Consequently, the firing timing of the thyristor
8 is retarded and the ignition timing characteristic is
gradually retarded in accordance with the engine speed.
While, in the embodiments illustrated in
Figs. 4, 8, 14, 16, 19 and 22, the primary windings
9a and 14a of the transformers 9 and 14 are connected
in series with each other, these primary windings 9a
and 14a may be connected in parallel with each other
through a diode or without using a diode.
Further, while, in the embodiments illustrated
in Figs. 1, 4, 8, 12, 13, 14, 16, 19 and 22, the diode
13 is provided between the gate and cathode of the
thyristor 8 in inverse parallel connection therewith,
.,
- 30 -
,
106Z326
1 the diode 13 may be eliminated if a diode is inserted
in series with the gate circuit of the thyristor 8 or
if the gate and cathode of the thyristor 8 can withstand
a considerably high reverse voltage.
Still further, while, in the embodiments of
the invention described above, the Zener diode 15 is
mainly utilized to vary the impedance of one signal
conversion circuit relative to that of the other
signal conversion circuit, any other semiconductor
element such as a diac or varistor may be used in place
of the Zener diode 15 or alternately other element such
as a coil, capacitor or resistor may be used to vary
the impedance of the signal conversion circuit.
.
31
