U.S. patent number 3,870,028 [Application Number 05/352,362] was granted by the patent office on 1975-03-11 for ignition system for internal combustion engines.
This patent grant is currently assigned to Diamond Electric Mfg. Co., Ltd.. Invention is credited to Yoshio Ishida.
United States Patent |
3,870,028 |
Ishida |
March 11, 1975 |
Ignition system for internal combustion engines
Abstract
An ignition system of capacitor discharge type for internal
combustion engines having a DC source, an ignition transformer, a
thyristor, a capacitor, a transistor and an oscillator. With all
the elements in the system, the capacitor is discharged through the
thyristor, transistor and primary winding of transformer when the
transistor and thyristor are simultaneously rendered conductive in
response to the appearance of a pulse from the oscillator. The
capacitor is then charged by a counter electromotive force produced
in the primary winding of the transformer in response to subsequent
cut-off of the transistor.
Inventors: |
Ishida; Yoshio (Osaka,
JA) |
Assignee: |
Diamond Electric Mfg. Co., Ltd.
(Osaka, JA)
|
Family
ID: |
23384819 |
Appl.
No.: |
05/352,362 |
Filed: |
April 18, 1973 |
Current U.S.
Class: |
123/598;
315/209CD; 123/640 |
Current CPC
Class: |
F02P
3/093 (20130101); F02P 3/0884 (20130101) |
Current International
Class: |
F02P
3/09 (20060101); F02P 3/08 (20060101); F02P
3/00 (20060101); F02p 003/06 () |
Field of
Search: |
;123/148E |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Antonakas; Manuel A.
Assistant Examiner: Cranson; J. W.
Attorney, Agent or Firm: Sughrue, Rothwell, Mion, Zinn &
Macpeak
Claims
What is claimed is:
1. An ignition system for internal combustion engines comprising an
ignition transformer means having a primary and a secondary
winding, and said primary winding being grounded at one end thereof
through a transistor and connected at the other end thereof to a DC
source through a diode, said the other end of said primary winding
being further grounded through a thyristor and a capacitor
connected in series, and said secondary winding being connected at
one end thereof to an ignition plug, an oscillator means for
generating at least one pulse having a predetermined pulse width
every predetermined ignition timing of the engine in synchronism
with the rotation of the engine, means for coupling the output
pulse of said oscillator means to the base of said transistor,
means for coupling the output pulse of said oscillator means to the
gate of said thyristor, said thyristor, said transistor and said
primary winding of said transformer means providing a discharge
circuit for said capacitor when both said transistor and said
thyristor are rendered conductive substantially simultaneously in
response to the application of the output pulse from said
oscillator means, and means for charging said capacitor by a
counter electromotive force produced in said primary winding of
said transformer means when said transistor in the conducting state
is rendered non-conductive.
2. An ignition system for internal combustion engines as claimed in
claim 1, wherein said oscillator means generates at said
predetermined ignition timing at least two pulses having a
predetermined pulse width with a relatively short time interval
therebetween.
3. An ignition system for internal combustion engines as claimed in
claim 2, wherein only one of the output pulses of said oscillator
means is coupled to the gate of said thyristor at said
predetermined ignition timing.
4. An ignition system for internal combustion engines as claimed in
claim 1, further comprising a second oscillator means and a second
transformer means having a primary and a secondary winding, said
primary winding of said second transformer means being grounded at
one end thereof through a second transistor and connected at the
other end thereof to said DC source, while said secondary winding
of said second transformer means being connected at one end thereof
to said capacitor through another diode and grounded directly at
the other end thereof, and said second oscillator means being
operative in such a manner that an output pulse, which appears
substantially simultaneously with the appearance of the output
pulse from said first oscillator means and disappears after the
disappearance of the output pulse from said first oscillator means,
is generated from said second oscillator means to be applied to
said second transistor for maintaining said second transistor
conductive during such period of time.
5. An ignition system for internal combustion engines as claimed in
claim 2, further comprising a second oscillator means and a second
transformer means having a primary and a secondary winding, said
primary winding of said second transformer means being grounded at
one end thereof through a second transistor and connected at the
other end thereof to said DC source, while said secondary winding
of said second transformer means being connected at one end thereof
to said capacitor through another diode and grounded directly at
the other end thereof, and said second oscillator means being
operative in such a manner that an output pulse, which appears
substantially simultaneously with the appearance of the first
output pulse from said first oscillator means and disappears after
the disappearance of the second output pulse from said first
oscillator means, is generated from said second oscillator means to
be applied to said second transistor for maintaining said second
transistor conductive during such period of time.
Description
This invention relates to ignition systems for internal combustion
engines and more particularly to an ignition system of the kind
utilizing discharge of a capacitor for the ignition of fuel.
In conventional ignition systems for internal combustion engines
employing an ignition coil, a DC source is connected to the primary
winding of the ignition coil through an interrupter contact for
causing flow of current through the primary winding of the ignition
coil while the interrupter contact is in the closed position, and
this current flow is interrupted by opening the interrupter contact
in synchronism with the ignition timing of the internal combustion
engines so that a high voltage induced in the secondary winding of
the ignition coil as a result of the opening of the interrupter
contact can be utilized for causing spark discharge in an ignition
plug connected to the secondary winding of the transformer thereby
igniting fuel. However, the conventional ignition system of the
type above described has been defective in that the duration of the
spark discharge is relatively short and the conditions of ignition
tend to be adversely affected by variations of the load on the
engine due to the fact that the quantity of energy supplied for the
ignition is relatively small. The conventional ignition system has
further been defective in that, when the electrode portion of the
ignition plug is excessively fouled, a spark is difficult to occur
and this results in failure of proper ignition or incomplete
combustion of fuel which gives rise to undesirable contamination of
atmospheric air.
An ignition system of the type utilizing discharge of a capacitor
has been developed recently. This ignition system is advantageous
in that the ignition is substantially free from the contamination
of the electrode portion of the ignition plug due to the fact that
the secondary voltage rises to a predetermined level relatively
quickly. However, this ignition system is disadvantageous in that
the duration of spark discharge and the energy supplied by the
spark discharge have a certain limit. Another disadvantage of this
ignition system resides in the fact that complex and expensive
means such as an osicllator and a converter are required and the
overall size and weight of the ignition system are inevitably
increased.
With a view to eliminate such prior art disadvantages, it is an
object of the present invention to provide a novel and improved
ignition system of the capacitor discharge type for internal
combustion engines which can reliably generate sparks without being
substantially adversely affected by contamination of the ignition
plug or load conditions of the engine.
Another object of the present invention is to provide an ignition
system of the type above described in which the spark discharge
lasts for an extended period of time and the energy supplied for
the ignition can be increased for attaining reliable ignition of
fuel.
A further object of the present invention is to provide an ignition
system of the type above described which is relatively small in
size, light in weight and compact in construction.
Other objects, features and advantage of the present invention will
be apparent from the following detailed description of preferred
embodiments thereof taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a circuit diagram of an embodiment of the present
invention with a part shown by a block; and
FIG. 2 is a circuit diagram of another embodiment of the present
invention with parts shown similarly by blocks.
Referring to FIG. 1 showing a preferred embodiment of the present
invention, a DC source V.sub.B of, for example, 12 volts is
connected to a resistor r.sub.1 through a main switch MS. This
resistor r.sub.1 is grounded through an interrupter contact K which
is opened and closed in synchronism with the rotation of an intenal
combustion engine. The main switch MS is connected through a diode
D.sub.1 to one end of a primary winding N.sub.1 of an ignition
transformer TR and to one end of a secondary winding N.sub.2 of the
transformer TR.
The primary and secondary windings N.sub.1 and N.sub.2 of the
ignition transformer TR are relatively closely coupled to each
other as in, for example, an ignition coil for an automotive
vehicle. The other end of the primary winding N.sub.1 is grounded
through the collector-emitter path of a transistor Q.sub.1. The
other end of the secondary winding N.sub.2 is grounded through an
ignition plug P as is customary in the art. The connection point or
node 10 between the resistor r.sub.1 and the interrupter contact K
is connected to an input terminal of an oscillator OSC which has
two output terminals. The first output terminal of the oscillator
OSC is connected to the base of the transistor Q.sub.1, and the
second output terminal of the oscillator OSC is connected through a
capacitor C.sub.2 to one end of a resistor r.sub.2 and to one of
the electrodes of a diode D.sub.2. The other end of the resistor
r.sub.2 is connected to the main switch MS.
A thyristor Q.sub.2 and a capacitor C.sub.1 are connected in series
between ground and the node 12 between the diode D.sub.1 and the
ignition transformer TR, and the thyristor Q.sub.2 is disposed in a
direction opposite to the forward direction of the diode D.sub.1.
The gate of the thyristor Q.sub.2 is connected to the other
electrode of the diode D.sub.2. Another diode D.sub.3 is connected
between the node 14 between the thyristor Q.sub.2 and the capacitor
C.sub.1 and the node 16 between the primary winding N.sub.1 of the
ignition transformer TR and the collector of the transistor
Q.sub.1. Obviously, the forward directions of these diodes and
thyristor should be determined to suit the operation of the system
described below. The oscillator OSC may be of any suitable type
provided that it can generate a pulse having a predetermined pulse
width T.sub.1 every ignition timing, i.e., each time the contact K
is urged to the open position.
The ignition system of the present invention having a structure as
shown in FIG. 1 operates in a manner as described below. For
convenience of description, it is assumed that the main switch MS
is turned on when the interrupter contact K is in the closed
position. The voltage drop across the contact K is negligible, and
therefore, the oscillator OSC is in the deenergized state and the
transistor Q.sub.1 remains non-conductive. Current is supplied from
the DC source V.sub.B to the capacitor C.sub.1 through the route
including the main switch MS, diode D.sub.1, primary winding
N.sub.1 of transformer TR, diode D.sub.3 and capacitor C.sub.1,
with the result that the capacitor C.sub.1 is charged up to
substantially the power supply voltage level in the illustrated
polarity.
Although the power supply voltage is applied at the same time from
the DC source V.sub.B to the gate of the thyristor Q.sub.2 through
the resistor r.sub.2 and diode D.sub.2, this voltage is inactive
against the thyristor Q.sub.2 due to the fact that the potential
difference across the thyristor Q.sub.2 is opposite to that in the
normal direction. Further, the capacitor C.sub.2 is charged in the
illustrated polarity by the current which is supplied from the DC
source V.sub.B through the route including the resistor r.sub.2,
capacitor C.sub.2 and oscillator OSC.
The engine starts to rotate in the state in which the capacitors
C.sub.1 and C.sub.2 are charged in the manner above described. When
the interrupter contact K is urged to the open position in
synchronism with the rotation of the engine, a pulse having a
predetermined pulse width T.sub.1 as above described appears at the
first output terminal of the oscillator OSC and the transistor
Q.sub.1 conducts in response to the application of the oscillator
output to the base thereof. Thus, current flows from the DC source
V.sub.B through the route including the diode D.sub.1, primary
winding N.sub.1 of transformer TR and transistor Q.sub.1 for
energizing the transformer TR. The output pulse appearing at the
second output terminal of the oscillator OSC is applied at the same
time to the capacitor C.sub.2 so that a control signal voltage is
applied to the gate of the thyristor Q.sub.2 through the diode
D.sub.2. However, the thyristor Q.sub.2 remains still
non-conductive due to the fact that the potential difference there
across is opposite to that in the normal direction.
Upon terminaion of the generation of the first pulse from the
oscillator OSC, the transistor Q.sub.1 is rendered non-conductive
thereby interrupting the flow of current through the primary
winding N.sub.1 of the transformer TR. Thus, a high voltage is
induced in the secondary winding N.sub.2 of the transformer TR and
spark discharge occurs in the ignition plug P as in the
conventional ignition system. At the same time, counter
electromotive force is produced in the primary winding N.sub.1 due
to a leakage inductance and current flows through the diode D.sub.3
to charge the capacitor C.sub.1 up to a level of, for example, 200
volts, thereby inverting the direction of the potential difference
across the thyristor Q.sub.2. Further, the capacitor C.sub.2 is
charged again in the illustrated direction.
Two points should be noted in this connection. In the first place,
although a relatively high voltage of, for example, 15 kilovolts is
required in order to initiate the spark discharge at the ignition
plug P, the voltage required for maintaining the spark discharge
after initiation of such discharge may be relatively low or of the
order of, for example, 2 kilovolts. Secondly, in the arrangement in
which the primary winding N.sub.1 is short-circuited
unidirectionally and the DC source V.sub.B is connected
there-across, the spark discharge is maintained until the DC source
V.sub.B is electrically disconnected from the circuit once the
spark discharge takes place. It is considered that the spark
discharge can be maintained for the following reasons:
Minute oscillatory variations (of such an extent which will not
cause inversion of the polarity) in the magnitude of the spark
discharge current or current flowing through the secondary winding
N.sub.2 are reflected in the primary current flowing through the
primary winding N.sub.1 due to corresponding variations in the
magnetic flux in the iron core, and such primary current coacts
with the number of magnetic flux lines in the iron core again to
induce a secondary voltage against thereby providing the voltage
required for maintaining the spark discharge. As a result, the
current supplied from the DC source V.sub.B can effectively
maintain the spark discharge at the ignition plug P. Further, in
such an arrangement, the input impedance of the transformer TR when
locked from the side of the DC source V.sub.B is remarkably reduced
upon initiation of the spark discharge at the ignition plug P
resulting in an increase in the energy supplied from the DC source
V.sub.B through the transformer TR to be released at the ignition
plug P. Because of the fact that the discharge route for the
capacitor C.sub.1 includes the primary winding N.sub.1 of the
transformer TR, these elements constitute an LC oscillation
circuit. However, a portion of the oscillatory electromotive force
produced in the primary winding N.sub.1 is absorbed by the circuit
including the thyristor Q.sub.2 and diode D.sub.3, and the
capacitor C.sub.1 would not be charged in the reverse direction
after the discharge of the previously stored charge. Therefore, no
natural oscillation is produced by this LC combination.
With the above description in mind, the operation of the system of
the present invention at the second ignition timing will now be
described. At this second ignition timing, the ignition system
behaves in a manner somewhat different from the behavior in the
preceding operation.
This is due to the fact that the capacitor C.sub.1 has been charged
up to a voltage level considerably higher than the power supply
voltage V.sub.B by the charging action carried out in the last
stage of the preceding operation. In response to the opening of the
interrupter contact K, a second pulse appears from the oscillator
OSC, and the transistor Q.sub.1 and thyristor Q.sub.2 are rendered
conductive substantially simultaneously in response to the
appearance of the pulse from the oscillator OSC.
As a result, the charge stored in the capacitor C.sub.1 is
discharged through the primary winding N.sub.1 of the transformer
TR. A steeply rising high voltage is thereby applied to the
ignition plug P for initiating the spark discharge at the ignition
plug P. The current from the DC source V.sub.B is additionally
supplied to the ignition plug P in the manner above described so
that the spark discharge can be maintained over a period of time
corresponding to the duration T.sub.1 of the pulse. Further, a
large quantity of energy is supplied for igniting fuel as above
described. Upon completion of the discharge of capacitor C.sub.1,
thyristor Q.sub.2 is rendered nonconductive. Therefore, upon
disappearance of this pulse, the transistor Q.sub.1 is rendered
non-conductive to interrupt the flow of current through the primary
winding N.sub.1 of the transformer TR. As a result, a portion of
the magnetic energy stored in the iron core of the transformer TR
is subsequently released at the ignition plug P as ignition energy
to cause spark discharge in a reverse direction for a short period
of time. (This corresponds to the spark discharge in the
conventional system described in the preface of this
specification.). The remaining portion of the magnetic energy
produces a counter electromotive force in the primary winding
N.sub.1 and this counter electromotive force is supplied to the
capacitor C.sub.1, as described previously, to be held in the
capacitor C.sub.1 until the next ignition takes place.
It will be understood from the above description that the present
invention provides such an advantage that the ignition can be
attained by a large quantity of energy supplied in the form of
electrical power from the DC source V.sub.B and maintained over a
relatively long period of time corresponding to the pulse width
T.sub.1 of the pulse output of the oscillator OSC, in addition to
the advantage pertinent to the initiation of spark discharge
utilizing the capacitor discharge.
The preferred embodiment of the present invention above described
has been so arranged that the oscillator OSC generates a pulse
having a pulse width T.sub.1 each time the interrupter contact K is
urged to the open position. In a modification of this embodiment,
the oscillator OSC may generate two or more pulses T.sub.1 having a
short time interval T.sub.2 therebetween.
According to this modification, the transistor Q.sub.1 is turned on
and off twice or more every ignition timing and the capacitor
C.sub.1 is charged and discharged each time the transistor Q.sub.1
is turned on and off. Further, discharge in one direction due to
conduction of the transistor Q.sub.1 and discharge in the opposite
direction due to non-conduction of the transistor Q.sub.1 occur
repeatedly at the ignition plug P as described previously.
The spark discharge can be substantially continuously carried out
when the time interval T.sub.2 between the pulses is relatively
short and the next supply of the primary current is started during
the period of time in which the spark discharge is sustained by the
release of the magnetic energy stored in the iron core after the
transistor Q.sub.1 is rendered non-conductive. It is thus not
necessarily required to cause discharge of the capacitor C.sub.1 in
response to each of these pulses T.sub.1. In such a case, the
thyristor Q.sub.2 is rendered conductive to cause discharge of the
capacitor C.sub.1 in response to the first pulse T.sub.1 supplied
from the oscillator OSC by suitably selecting the resistance value
of the charging resistor r.sub.2 for the capacitor C.sub.2 so that
the capacitor C.sub.2 can be insufficiently charged during the
period of time T.sub.2 between the pulses. Therefore, the charge in
the capacitor C.sub.1 is accumulated each time the primary current
is interrupted.
These modifications may be suitably employed depending on the
structure of the engine combustion chamber, manner of supplying
fuel and other conditions for attaining the desired object.
In FIG. 2 showing another preferred embodiment of the present
invention, like reference numerals are used to denote like parts
appearing in FIG. 1, and therefore, any detailed description as to
such elements is unnecessary. In the following description
therefore, those elements which are newly added or replace the
corresponding elements in FIG. 1 will be especially described.
Referring to FIG. 2, the node 10 between resistor r.sub.1 and an
interrupter contact K is connected to an input terminal of a
trigger pulse generator TRIG which has two output terminals. One of
the output terminals of the trigger pulse generator TRIG is
connected to an input terminal of a first oscillator OSC No. 1,
while the other output terminal of the trigger pulse generator TRIG
is connected to an input terminal of a second oscillator OSC No. 2.
In response to the application of a trigger pulse from the trigger
pulse generator TRIG to the first oscillator OSC No. 1, the
oscillator OSC No. 1 generates a pulse T.sub.1 having a relatively
small pulse width of, for example, 1 ms and this pulse is applied
to the base of a transistor Q.sub.1 from the first output terminal
of the oscillator OSC No. 1. In response to the application of the
trigger pulse from the trigger pulse generator TRIG to the second
oscillator OSC No. 2, the oscillator OSC No. 2 generates a pulse
T.sub.3 having a relatively large pulse width of, for example, 2
ms. A main switch MS is connected through a diode D.sub.1 to one
end of primary and secondary windings N.sub.1 and N.sub.2 of an
ignition coil IGC and to the cathode of a thyristor Q.sub.2.
Further, the main switch MS is grounded through a primary winding
N.sub.1 ' of a transformer TR' and a transistor Q.sub.3 which are
connected in series.
The base of this transistor Q.sub.3 is connected to an output
terminal of the second oscillator OSC No. 2. A secondary winding
N.sub.2 ' of the transformer TR' is grounded directly at one end
thereof and is connected at the other end thereof to the node 14
between the thyristor Q.sub.2 and a capacitor C.sub.1 through a
diode D.sub.4. A capacitor C.sub.2 is connected at one of the
electrodes thereof the gate of the thyristor Q.sub.2 through a
diode D.sub.2 and at the other electrode thereof to the second
output terminal of the first oscillator OSC No. 1 to receive the
pulse T.sub.1 therefrom. A protective resistor r.sub.3 may be
disposed in parallel with the transistor Q.sub.1.
In the operation of the second embodiment of the present invention
shown in FIG. 2 which will be now described, it is needless to
waste words for the operation of those parts which have been
described already with reference to FIG. 1. In response to the
turn-on of the main switch MS, the capacitor C.sub.2 is charged in
the illustrated polarity through the charging resistor r.sub.2. At
the same time, the capacitor C.sub.1 is charged up to substantially
the power supply voltage V.sub.B through the diode D.sub.1, primary
winding N.sub.1 of ignition coil IGC and diode D.sub.3. The
remaining parts of the circuit are still not in operation.
When the interrupter contact K is urged to the open position in
such a situation in synchronism with the rotation of the engine,
the trigger signal is applied from the trigger pulse generator TRIG
to the first and second oscillators OSC No. 1 and OSC No. 2. In
response to the application of the trigger pulse, the pulses of
predetermined duration, that is, the pulse T.sub.2 having a
relatively small pulse width and the pulse T.sub.3 having a
relatively large pulse width appear at the output terminals of the
first and second oscillators OSC No. 1 and OSC No. 2 respectively
so that the transistor Q.sub.1, thyristor Q.sub.2 and transistor
Q.sub.3 are rendered conductive almost simultaneously. As a result,
energizing current flows through the primary winding N.sub.1 of the
ignition coil IGC and through the primary winding N.sub.1 ' of the
transformer TR' and magnetic energy is accumulated in the iron core
of the ignition coil IGC and transformer TR'. However, no current
flows through the thyristor Q.sub.2.
The transistor Q.sub.1 is cut off before the transistor Q.sub.3 is
cut off due to the fact that the pulse width of the pulse T.sub.1
is smaller than that of the pulse T.sub.3. The cut off of the
transistor Q.sub.1 results in interruption of the flow of the
primary current in the ignition coil IGC and a portion of the
magnetic energy accumulated in the iron core of the ignition coil
IGC is released at an ignition plug P as spark producing energy.
The remaining portion of the magnetic energy provides a counter
electromotive force in the primary winding N.sub.1 of the ignition
coil IGC and the capacitor C.sub.1 is charged thereby through the
diode D.sub.3. Then, when the transistor Q.sub.3 is rendered
non-conductive, the magnetic energy accumulated in the iron core of
the transformer TR' connected thereto induces a voltage in the
secondary winding N.sub.2 ' of the transformer TR' and this voltage
is applied from the secondary winding N.sub.2 ' to the capacitor
C.sub.1 through the diode D.sub.4 for charging the capacitor
C.sub.1. The charge supplied to the capacitor C.sub.1 from the
primary winding N.sub.1 of the ignition coil IGC is subject to
slight variations depending on the condition of release of the
energy at the ignition plug P. However, the charge supplied from
the secondary winding N.sub.2 ' of the transformer TR' compensates
for such variations so that a voltage sufficient for initiating
spark discharge at the ignition plug P in the next ignition timing
is built up in the capacitor C.sub.1.
When the interrupter contact K is opened at the next ignition
timing and the trigger signal is applied to the first and second
oscillators OSC No. 1 and OSC No. 2, the pulses T.sub.1 and T.sub.3
are applied to the respective transistors Q.sub.1 and Q.sub.3 to
render these transistors conductive.
The gate control signal is applied to the gate of the thyristor
Q.sub.2 almost simultaneously with the result that the charge
stored in the capacitor C.sub.1 is discharged by way of the
discharge route including the thyristor Q.sub.2, primary winding
N.sub.1 of ignition coil IGC and transistor Q.sub.1. An abruptly
rising high voltage is thereby induced in the secondary winding
N.sub.2 of the ignition coil IGC to initiate spark discharge at the
ignition plug P. In this case, the natural oscillation that may
occur in the LC discharge route is absorbed by the circuit
including the diode D.sub.3 and thyristor Q.sub.2. Thus, spark
discharge with large energy is continued at the ignition plug P by
the electrical power supplied from the DC source V.sub.B during the
period of time in which the transistor Q.sub.1 remains conductive.
Upon completion of the discharge of the capacitor C.sub.1, the
thyristor Q.sub.2 is rendered nonconductive. Thereafter, the
capacitor C.sub.1 is re-charged upon disappearance of the pulses
T.sub.1 and T.sub.3 to prepare for the next ignition.
The second embodiment of the present invention has been described
with reference to the arrangement in which one pulse T.sub.1 of
predetermined duration and one pulse T.sub.3 of predetermined
duration apppear from the first and second oscillators OSC No. 1
and OSC No. 2 respectively every ignition timing. In a modification
of such embodiment, the first oscillator OSC No. 1 may generate two
or more pulses T.sub.1 having a time interval T.sub.2 therebetween
in response to the application of one trigger pulse input from the
trigger pulse generator TRIG, and the second oscillator OSC No. 2
may generate a pulse T.sub.3 whose duration is larger than the
total sum of these pulses T.sub.1 and time intervals T.sub.2.
Further, the relation between the time interval T.sub.2 and the
pulse width of the pulse T.sub.1 in such a case may be such as is
considered in the modifications of the first embodiment. Further,
although the transformer TR' in FIG. 2 is shown having a secondary
winding, it may have merely a primary winding wound around an iron
core so that a counter electromotive force produced in the primary
winding may be derived as magnetic energy for charging the
capacitor C.sub.1 as shown in FIG. 1.
The embodiments of the present invention above described have been
illustrated as the type provided with an interrupter contact K
which is mechanically opened and closed in synchronism with the
rotation of the engine. However, the system having such mechanical
on-off means is merely illustrative of one form of the present
invention and those skilled in the art can easily make
modifications in which electromagnetic, optical or any other
suitable means are employed in lieu of such mechanical on-off means
for controlling the oscillators or trigger signal generator. It
should be understood therefore that such modifications are also
included in the scope of the present invention in addition to the
preferred embodiments above described.
* * * * *