U.S. patent number 3,595,212 [Application Number 04/799,688] was granted by the patent office on 1971-07-27 for sparking circuit for an ignition system for internal combustion engines.
This patent grant is currently assigned to Rolls-Royce Limited. Invention is credited to Leslie Barnes.
United States Patent |
3,595,212 |
Barnes |
July 27, 1971 |
SPARKING CIRCUIT FOR AN IGNITION SYSTEM FOR INTERNAL COMBUSTION
ENGINES
Abstract
The invention concerns a sparking circuit for an ignition system
for internal combustion engines comprising first and second
discharge circuits, the first circuit being operatively associated
with said second circuit via delay circuit means, discharge of the
first circuit causing said second circuit to discharge after said
first circuit but at less than 1 millisecond thereafter.
Inventors: |
Barnes; Leslie (Littleover,
Derby, EN) |
Assignee: |
Rolls-Royce Limited (Derby,
EN)
|
Family
ID: |
9844254 |
Appl.
No.: |
04/799,688 |
Filed: |
February 17, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Feb 19, 1968 [GB] |
|
|
8020/68 |
|
Current U.S.
Class: |
123/637;
315/180 |
Current CPC
Class: |
F02P
3/08 (20130101); H01R 39/60 (20130101); F02C
7/266 (20130101) |
Current International
Class: |
F02C
7/26 (20060101); H01R 39/60 (20060101); F02P
3/00 (20060101); F02C 7/266 (20060101); F02P
3/08 (20060101); H01R 39/00 (20060101); F02p
003/06 () |
Field of
Search: |
;123/148E
;315/180,182 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Claims
I claim:
1. A sparking circuit for use in the ignition system of an internal
combustion engine, said circuit comprising:
a first discharge circuit means for producing a leader spark used
to blast liquid fuel away from sparking electrodes in a combustion
chamber of said engine,
a second discharge circuit means for producing a main spark used to
ignite fuel in said chamber while it is set in motion by said
leader spark thereby setting up a travelling flame in said
combustion chamber,
said first and second discharge circuit means each comprising a
rectifier, a condenser and a discharge tube, and
a third circuit means including delay means and operatively
connected between said first and second circuit means for
triggering discharge of said second circuit, after a time delay,
from the discharge of said first circuit wherein discharge of said
first circuit energizes said third circuit which, in turn, causes
said second circuit to discharge between approximately 250 and 750
microseconds after said first circuit.
2. A sparking circuit as claimed in claim 1 in which first and
second charging means are provided for effecting separate charging
of the first and second discharge circuits, whereby, when desired,
one only of the said circuits may be charged.
3. A sparking circuit as claimed in claim 2 in which the first and
second charging means are such that the discharge pulses produced
thereby are of substantially equal energy.
Description
This invention, which relates to a sparking circuit for an ignition
system for internal combustion engines, is an improvement in or
modification of the invention disclosed in our British Pat. No.
994,712.
In British Pat. No. 994,712 there is disclosed a sparking circuit
for an ignition system for internal combustion engines which
comprises first and second discharge circuits, said first discharge
circuit being operatively associated with said second circuit via
delay circuit means, so that in operation when said first circuit
discharges it causes said second circuit to discharge between 1 and
40 milliseconds after said first circuit. In use, both said first
and second circuits are connected to a sparking fuel igniter, such
as a sparking plug, so that, in operation, said first and second
circuits discharge between electrodes of said igniter.
The purpose of discharging the first circuit before the second
circuit was to rupture any liquid fuel layer on the electrodes of
the igniter, so that when the second circuit discharges, most of
its energy is used in forming a spark between said electrodes. By
arranging that the first circuit only discharges sufficient energy
to rupture the liquid fuel layer normally found in operation on the
igniter electrodes, the total energy dissipated per "spark" (i.e.
the total energy dissipated by the first and second circuits), can
be less than with a conventional sparking system in which a single
electrical power pulse is applied between the igniter
electrodes.
In the case of the sparking circuit of British Pat. No. 994,712,
however, the "leader spark" produced by the first discharge circuit
merely blasted fuel off the electrodes so that the "main spark"
produced by the second discharge circuit could subsequently effect
ignition of fuel supplied to the combustion chamber in the normal
way.
We have now found, however, that significantly improved results are
obtained if the second circuit discharges less than one millisecond
after the first circuit, since the fuel blasted off by the leader
spark will then be immediately ignited by the main spark, thus
setting up a "travelling flame" which ignites the fuel supplied to
the combustion chamber.
According therefore to the present invention, there is provided a
sparking circuit for an ignition system for internal combustion
engines comprising first and second discharge circuits, the first
circuit being operatively associated with said second circuit via
delay circuit means, so that in operation when said first circuit
discharges, it causes said second circuit to discharge after said
first circuit but at less than 1 millisecond thereafter.
Preferably the second circuit discharges between 250 and 750
microseconds after said first circuit.
First and second charging means may be provided for effecting
separate charging of the first and second discharge circuits,
whereby, when desired, one only of the said circuits may be
charged.
The first and second charging means are preferably such that the
discharge pulses produced thereby are of substantially equal
energy.
The invention is illustrated merely by way of example, in the
accompanying drawings, in which:
FIG. 1 shows two successive electrical current pulses produced by a
sparking circuit according to the invention,
FIG. 2 shows a circuit diagram of a sparking circuit according to
the invention, and
FIG. 3 shows a circuit diagram of a modified sparking circuit.
The two pulses 5, 6 of FIG. 1, when they pass between the
electrodes of a sparking fuel igniter, serve respectively to
produce a leader spark which blasts off any liquid fuel on the
igniter electrodes, and a main spark which effects immediate
ignition of this blasted off fuel and therefore sets up a
travelling flame which ignites the fuel supplied to the combustion
chamber. The pulse 6 occurs after the pulse 5 but at less than 1
millisecond (and preferably between 250 and 750 microseconds
thereafter) and the maximum amplitude of the pulse 5 as illustrated
is smaller than and approximately half that of pulse 6.
In one case using an igniter of the recess gap type, (i.e. an
igniter having a hollow outer electrode, an inner electrode which
is flush with the end of the outer electrode, and semiconductor
material which is disposed in a recess between the electrodes)
liquid fuel was displaced satisfactorily from the igniter
electrodes when the energy of pulse 5 had a minimum value of 0.4
joules. For a flush fire type of igniter (i.e. an igniter in which
both the electrodes and the semiconductor material are flush) less
energy would be necessary for displacing liquid fuel satisfactorily
from the igniter electrodes.
The invention is particularly applicable, however, to the recess
gap type igniter since the recess of the latter holds more fuel
than collects on a flush fire type of igniter, and a bigger
travelling flame can therefore be produced.
The sparking circuit shown in FIG. 2 comprises a first spark
generating circuit which includes a rectifier 8, a condenser 9 and
a low pressure gas discharge tube 10, and a second spark generating
circuit which includes a rectifier 11, a condenser 12 and a low
pressure gas discharge tube 13. The breakdown voltage of the tube
13 is preferably greater than that of tube 10. The rectifier 8 is
connected to an H.T. alternating or pulsating supply 14, and
between a circuit point 15 and an earth connection 16 is connected
condenser 9. The rectifier 11 is connected between circuit points
15 and 26, while the condenser 12 is connected between circuit
point 26 and the earth connection 16. Both the first and second
circuits are connected together at circuit point 17, which is
connected in turn to an electrode 18 of a sparking fuel igniter 19,
the igniter 19 having a second electrode 20 which is connected to
earth, and also the electrode 18 via means 21 providing a very high
resistance, such as a semiconductor.
The first circuit is operatively associated with the second circuit
via delay circuit means comprising an electromagnetic coupling in
the form of a transformer 23, and a delay circuit 22. The circuit
22 is connected to an electrode 24 of the gas discharge tube 13,
the electrode 24 being arranged externally of the tube and
intermediate its two other electrodes which are connected in the
second circuit.
In operation, when the H.T. supply is switched on, both condensers
9, 12 charge through the rectifier 8, the condenser 12 in addition
charging through the rectifier 11. Condenser 12 has a considerably
greater capacity than the condenser 9. The voltages at circuit
points 15 and 26 progressively rise, and when the voltage across
the gas discharge tube 10 reaches the breakdown voltage thereof,
the condenser 9 discharges through the tube 10, the primary winding
of transformer 23, and across the electrodes 18, 20 of the igniter.
This pulse is the pulse 5 (FIG. 1) and serves to produce the said
leader spark which blasts off fuel on the electrodes 18, 20. It
will be noted that the rectifier 11 prevents the condenser 12
discharging through the tube 10 when the latter is conducting. The
current pulse flowing through the primary winding of the
transformer 23 causes a voltage pulse to appear on the electrode 24
after a delay determined by the transformer 23 and the delay
circuit 22, the transformer 23 contributing to the delay which is
less than 1 millisecond. This voltage pulse causes the tube 13 to
become conducting, and the condenser 12 discharges through the tube
13 and forms the said main spark between the electrodes 18, 20 of
the igniter. The current pulse occurring in the second circuit when
the main spark is formed is the pulse 6 (FIG. 1).
The modified sparking circuit shown in FIG. 3 is generally similar
to that of FIG. 2 and for this reason will not be described in
detail, like reference numerals indicating like parts.
In the FIG. 3 sparking circuit, however, the condenser 12, instead
of being charged from the H.T. supply 14 through the rectifiers 8
and 11, is charged from a separate H.T. supply 30 through a
rectifier 31. Thus the said first and second circuits are charged
by separate charging means, the arrangement being such that both
the sparks produced thereby are of equal energy, e.g. 6 joules.
Accordingly, in the case of the FIG. 3 construction, both the H.T.
supplies 14, 30 are employed for normal starting. For continuous
starting, however, e.g. starting in flight and with the engine
warm, only the H.T. supply 14 is employed.
* * * * *