U.S. patent number 3,620,200 [Application Number 04/839,886] was granted by the patent office on 1971-11-16 for booster circuit for ignition systems.
This patent grant is currently assigned to AMBAC Industries Incorporated, Columbus, MS. Invention is credited to Joe B. Stephens, Joel N. Ashcraft.
United States Patent |
3,620,200 |
|
November 16, 1971 |
BOOSTER CIRCUIT FOR IGNITION SYSTEMS
Abstract
A booster circuit is employed with an ignition system for an
internal combustion engine to assure that sufficient energy is
supplied to engine ignition means for igniting fuel in the engine
at predetermined engine speeds.
Inventors: |
Joe B. Stephens (Columbus,
MS), Joel N. Ashcraft (Columbus, MS) |
Assignee: |
AMBAC Industries Incorporated,
Columbus, MS (N/A)
|
Family
ID: |
25280895 |
Appl.
No.: |
04/839,886 |
Filed: |
July 8, 1969 |
Current U.S.
Class: |
123/620;
123/179.5; 123/149A |
Current CPC
Class: |
F02P
7/03 (20130101); F02B 1/04 (20130101) |
Current International
Class: |
F02P
7/03 (20060101); F02P 7/00 (20060101); F02B
1/04 (20060101); F02B 1/00 (20060101); F02p
003/06 () |
Field of
Search: |
;123/148A,148AC,148C,148D,148E,148DC,149,149A,179B-179G
;315/209 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Laurence M. Goodridge
Attorney, Agent or Firm: Howson and Howson
Claims
We claim:
1. In a booster circuit for use with an ignition system for an
internal combustion engine, the ignition system including a voltage
source, ignition means for igniting fuel in the engine in
synchronism with engine operation, controllable switch means for
selectively completing a circuit with the voltage source and the
ignition means to ignite fuel in the engine, the switch means
having a control terminal responsive to a control signal to actuate
the switch means to complete the circuit, and a trigger pulse
generator for generating a control signal applied to the control
terminal for actuating the switch means, the combination therewith
of: a booster power circuit having electronic circuitry including
at least two outputs for providing booster energy at the outputs,
first means for connecting one of the outputs of the booster
circuit power with the circuit completed by the controllable switch
means to assure producing of a suitable voltage applied to the
ignition means to ignite fuel in the engine, and second means for
connecting another output of the booster power circuit with the
trigger pulse generator to provide an increased intensity control
signal to assure actuation of the switch means.
2. The booster circuit of claim 1 in which the trigger pulse
generator includes a magnetogenerator having a magnetic circuit,
and the second means for connecting another output of the booster
power circuit with the trigger pulse generator includes a booster
coil connected in the magnetogenerator to which the booster energy
is applied for increasing the magnetic energy in the magnetic
circuit to provide an increased intensity control signal.
3. The booster circuit of claim 2 in which the first means connects
the booster power circuit with the circuit of the voltage source to
increase the electrical energy from the voltage source applied to
the ignition means.
4. The booster circuit of claim 3 in which the booster power
circuit is connected with the voltage source and the trigger pulse
generator upon starting the engine.
5. The booster circuit of claim 1 in which the voltage source
includes capacitive means and a magnetogenerator for charging the
capacitive means, the switch means completing the circuit with the
capacitive means and the ignition means for discharging the
capacitive means through the ignition means, and the first means
connects the booster power circuit to the circuit to charge the
capacitive means.
6. The booster circuit of claim 5 in which the trigger pulse
generator includes a magnetogenerator having a magnetic circuit,
and the second means for connecting another output of the booster
power circuit with the trigger pulse generator includes a booster
coil in the trigger pulse generator to which the booster energy is
applied for increasing the magnetic energy in the magnetic circuit
to provide an increased intensity control signal by the trigger
pulse generator.
7. The booster circuit of claim 1 in which the second means
connects the booster power circuit with the trigger pulse generator
by circuitry in the trigger pulse generator which increases the
intensity of the control signal to actuate the switch means.
8. The booster circuit of claim 7 in which the circuitry in the
trigger pulse generator includes a booster coil responsive to the
booster energy from the booster power circuit.
9. The booster circuit of claim 1 in which the trigger pulse
generator includes a magnetic circuit with a magnet pole and a
conductor rotated past each other in synchronism with engine
operation to generate the control signal in the conductor, and the
second means for connecting another output of the booster power
circuit with the trigger pulse generator includes a booster coil
which is interposed in the magnetic circuit of the trigger pulse
generator for increasing the energy in the magnetic circuit to
provide an increased intensity control signal in the conductor to
actuate the switch means.
10. The booster circuit of claim 9 in which the voltage source
comprises a magnetogenerator and the first means connects one of
the outputs of the booster power circuit to the output of the
magnetogenerator.
11. The booster circuit of claim 9 in which the magnet pole is
rotated relative to the conductor, and the booster coil is
positioned coaxial with the axis of rotation of the magnet
pole.
12. The booster circuit of claim 9 in which the magnet pole is
supported by and rotates with a shaft, and the booster coil
encircles the shaft and creates a magnetic flux which increases the
magnetic flux of the magnet pole.
13. The booster circuit of claim 12 in which the booster coil is
supported by a nonrotatable structure.
14. The booster circuit of claim 1 in which the booster power
circuit includes a source of voltage, oscillator means responsive
to the source of voltage for generating a series of pulses and
rectifier means for providing output pulses of one polarity.
15. The booster circuit of claim 14 in which the oscillator means
comprises a blocking oscillator.
16. The booster circuit of claim 14 in which the rectifier means
includes an electronic switch having a control element responsive
to a predetermined voltage and means connected in the circuit of
the control element for permitting passage of current to the
control element in response to a voltage in excess of a
predetermined level, and energy storage means responsive to the
output of the oscillator means for charging to a voltage in excess
of the predetermined level applied to the means connected in the
circuit of the control element for actuating the electronic switch
by the predetermined voltage to permit discharge of the energy
storage means through the electronic switch to provide pulses of
booster energy.
17. In a booster circuit for use with an ignition system for an
internal combustion engine, the ignition system including a voltage
source, ignition means for igniting fuel in the engine in
synchronism with engine operation, controllable switch means for
selectively completing a circuit with the voltage source and the
ignition means to ignite fuel in the engine, the switch means
having a control terminal responsive to a control signal to actuate
the switch means to complete the circuit, and a trigger pulse
generator for generating a control signal applied to the control
terminals for actuating the switch means and including a magnetic
circuit with a magnet pole and a conductor rotated past each other
in synchronism with engine operation to generate the control signal
in the conductor, the combination therewith of: a booster power
circuit having electronic circuitry including at least one output
for providing booster energy at the output, and means for
connecting the output with the trigger pulse generator to increase
the intensity of the control signal to assure actuation of the
switch means, the means for connecting the output of the booster
power circuit with the trigger pulse generator including a booster
coil which is interposed in the magnetic circuit of the trigger
pulse generator for increasing the energy in the magnetic circuit
to provide an increased intensity control signal in the conductor
to actuate the switch means.
18. The booster circuit of claim 17 in which the magnet pole is
rotated relative to the conductor, and the booster coil is
positioned coaxial with the axis of rotation of the magnet
pole.
19. The booster circuit of claim 17 in which the magnet pole is
supported by and rotates with a shaft, and the booster coil
encircles the shaft and creates a magnetic flux which increases the
magnetic flux of the magnet pole.
Description
The present invention relates to a booster circuit for use with an
ignition system employed with an internal combustion engine, and,
particularly, to an improved booster circuit for an ignition system
to provide suitable energy to engine ignition means for assuring
the igniting of fuel in the engine at predetermined engine
speeds.
In one type of conventional ignition system, combustible fuel is
ignited during sequentially timed intervals synchronized with the
phase of engine operation by means of breaker and associated
breaker points employed with a battery, together with a mechanical
rotating distributor in a well-known manner. Another type of
conventional ignition system employs a magnetogenerator as a source
of power which is employed with a breaker and associated breaker
points, together with a mechanical rotating distributor, as is well
known in the art. In recent years, ignition systems have been
designed in which the breaker apparatus is replaced by electronic
circuitry for performing similar functions in response to
electrical timing pulses produced in synchronism with engine
operation. Many of these systems have employed electronic switches
and a trigger generator to actuate the switches to a conductive
state for connecting voltage pulses to engine ignition means, which
includes a spark plug for each cylinder of the engine.
Difficulties have been experienced with the conventional and more
recent ignition systems during cranking or starting of the engine
and at low engine speeds. This is due to the failure of the
ignition system to provide sufficient energy to the ignition means
to enable proper combustion in the engine cylinders while starting
the engines and at low engine speeds. With battery-powered ignition
systems, for example, in cold weather, the voltage of the battery
is decreased and the parasitic load on the engine is increased
caused by such factors as less efficient operation of oil and other
pumps and of the starter mechanism. Furthermore, in ignition
systems employing a magnetogenerator as a main source of power, at
starting and low engine speeds, these generators have not provided
sufficient energy for easy starting of the engine and proper
performance at low engine speeds. In ignition systems employing
magnetogenerators, these problems arise since the generator has its
rotor geared to the engine crankshaft and the ignition system is
designed to operate at optimum performance at normal
engine-operating speeds. Thus, a sacrifice in performance is made
at low engine speeds, such as encountered during starting of the
engine.
To compensate for unsatisfactory performance of the ignition system
during starting and at low engine speeds, it is desirable to
provide energy booster apparatus to increase the energy delivered
to the spark plugs for igniting the fuel mixture in the engine
cylinders.
In the prior art, energy booster apparatus has been designed for
use with ignition systems to provide increased energy delivered to
the spark plugs during starting and at low engine speeds to assure
appropriate firing of the fuel for easy starting and better engine
performance. For the most part, these energy booster systems have
employed a source of voltage and circuits with movable parts, such
as a solenoid or coil operating a vibrating contact switch or
breaker contacts connected in the circuit with the source of
voltage, to provide increased energy in the ignition system. These
energy booster systems have not been as compact and inexpensive as
desirable and have not had a long operating life without
malfunction. Particularly, such systems employing vibrating or
breaker contacts are undesirable and cause problems since the
contacts frequently burn, pit and corrode and require periodic
setting. Also, since arcing occurs at the contacts during
operation, the apparatus must be shielded to prevent unwanted radio
frequency interference.
In accordance with the present invention, a new and improved
booster circuit with novel features is provided which cooperates to
provide a compact, economical and reliable arrangement for
improving the firing of the engine ignition means to ignite fuel in
the cylinders at predetermined engine speeds, such as when starting
the engine and at low engine speeds. The present booster circuit is
provided for use with an ignition system for an internal combustion
engine. The ignition system may include voltage means for
developing voltage pulses and for applying the pulses to ignition
means in synchronism with engine operation to ignite fuel in the
engine. The booster circuit preferably comprises pulse-generating
means having electronic circuitry for generating pulses of energy
and for applying the pulses to the ignition system for providing
suitable pulses to the ignition means for igniting fuel in the
engine at predetermined engine speeds.
The pulse-generating means of the booster circuit preferably
includes a source of voltage, oscillator means responsive to the
source of voltage for generating a series of pulses and coupling
means responsive to the series of pulses for applying the pulses of
energy to the ignition system. The source of voltage in the booster
circuit may be provided by a battery and means may be provided for
alternatively connecting the battery to the oscillator means or to
the output of the voltage means of the ignition system for applying
voltage of one polarity to the battery for charging the battery
after the engine is operating at normal engine-operating
speeds.
The booster circuit of the present invention is particularly suited
for use with capacity-discharge ignition systems, which usually
comprise a voltage source provided by a magnetogenerator charging a
capacitor, controllable switch means for selectively completing a
circuit with the capacitor and the engine fuel ignition means. The
controllable switch means usually has a control terminal responsive
to a suitable control signal to actuate the switch means to
complete the circuit and trigger means is provided for producing
the control signal applied to the control terminal for actuating
the controllable switch means. One such capacity-discharge ignition
system is shown and described in U.S. Pat. No. 3,311,783, of Gibbs
et al. and of common assignee herewith. In such capacity-discharge
ignition systems, the booster circuit is preferably connected to
the capacitor to increase the energy stored by the capacitor for
providing sufficient energy when the capacitor is discharged to
properly ignite the fuel in the engine for easy starting and good
performance of the engine.
Furthermore, the booster circuit of the present invention may be
coupled to the trigger means of ignition systems that employ
trigger means to generate a control signal to actuate electronic
switches which complete circuits from a voltage source to the
engine fuel ignition means, as described above. The trigger means
in such ignition systems are usually provided by magnetogenerators
which have their rotors geared to the engine crankshaft. In this
arrangement, the booster circuit aids in providing a suitable
signal from the trigger pulse-generating means for assuring proper
actuation of the electronic switches upon starting of the engine
and at low engine speeds. Preferably, the booster circuit with this
type of ignition system provides pulses of energy in the magnetic
circuit of the trigger-generating means to assure that a suitable
control signal is generated by the trigger-generating means to
actuate the electronic switch.
For a better understanding of these and other features and
advantages of the present invention, reference is made to the
following description, taken in connection with the accompanying
drawings, in which:
FIG. 1 is a block diagram illustrating an overall ignition system
and booster circuit in accordance with one form of the present
invention;
FIG. 2 is a block diagram illustrating another overall ignition
system and booster circuit in accordance with another form of the
invention;
FIG. 3 is an electrical schematic diagram illustrating an ignition
system employed with one embodiment of the booster circuit in
accordance with the form of the present invention shown in FIG.
1;
FIG. 3a is an electrical schematic diagram illustrating an
alternative form for a portion of the circuit of FIG. 3;
FIG. 4 is a schematic diagram illustrating another overall ignition
system employed with the booster circuit in accordance with the
form of the present invention shown in FIG. 10;
FIG. 5 is an electrical schematic diagram illustrating another
overall ignition system and booster circuit in accordance with the
form of the invention shown in FIG. 2;
FIG. 6 is a planned view of an apertured plate trigger
pulse-generating apparatus preferably employed with the ignition
system of FIG. 5;
FIG. 7 is a sectional view taken along line 7--7 of FIG. 6; and
FIG. 8 is a schematic diagram illustrating still another overall
ignition system employed with the booster circuit in accordance
with the form of the present invention shown in FIG. 2.
Referring now to the embodiment of the invention illustrated by way
of example in FIG. 1, there is represented therein an ignition
system and booster circuit in use in conjunction with an engine 10
which may be a conventional gasoline engine. For purposes of
illustration, it will be assumed that the engine 10 has four
cylinders, each with an associated spark plug for igniting
combustible fuel in the corresponding cylinder, and that the engine
is of the usual four cylinder type. The proper timing relation for
firing fuel in the engine cylinders is provided by engine ignition
means 12, which will ordinarily comprise circuitry including four
spark plugs, one for each cylinder of engine 10. The ignition
system is provided with voltage means 14 which is connected to
engine ignition means 12. The function of the voltage means is to
provide voltage pulses to the engine ignition means in sequence
with engine operation so that each voltage pulse fires an
appropriate spark plug at the proper time.
There is shown employed with the ignition system of FIG. 1 a
booster circuit 16 which is connected to voltage means 14.
Preferably, when the engine 10 is being started and until it
reaches a predetermined speed, the booster circuit generates pulses
of energy, which may be pulses of voltage or current, and applies
them to the voltage means for providing suitable pulses to the
ignition means for assuring the proper ignition of the fuel in the
engine. Depending on the particular type of the voltage means
employed, the booster circuit 16 may be connected directly to the
line between voltage means 14 and engine ignition means 12 to apply
pulses directly to the engine ignition means for assuring ignition
of the fuel in the engine cylinders. In this manner, the booster
circuit assures easy starting of the engine and proper operation of
the engine at predetermined engine speeds. Since most ignition
systems are developed to operate for optimum performance of the
engine at normal engine-operating speeds, the predetermined engine
speeds at which it is desirable to employ the booster circuit are
governed by the particular operation of the engine and the normal
range of engine-operating speeds, the booster circuit being
particularly useful at speeds below the range of normal
engine-operating speeds, as when starting the engine and at low
engine speeds.
FIG. 2 illustrates another form of an overall ignition system which
may be employed with the booster circuit of the present invention.
The ignition system is shown in use with an engine 20, which may be
a conventional gasoline engine having six cylinders, for example.
The proper timing relation for firing the fuel in the engine
cylinders is provided by ignition means 22 which includes circuitry
having a spark plug for each cylinder of engine 20. The function of
the remainder of the ignition system of FIG. 2 is to provide the
appropriate voltage pulses to engine ignition means 22 in sequence
so that each voltage pulse fires the proper spark plug at the
proper time. To provide the proper voltage pulses, a voltage source
24 is employed which may be a conventional DC battery or a voltage
generator which is driven from engine crankshaft 26 by way of
appropriate gearing 28, as shown in FIG. 2, so as to produce at
output terminal 30 of the voltage source a train of pulses in
synchronism with rotation of the crankshaft 26. The gearing 28 is
such as to provide the desired integral multiple relationship
between the frequency of rotation of crankshaft 26 and the
frequency of recurrence of pulses at output 30 of voltage source
24.
The voltage output from voltage source 24 is supplied to
controllable switch means 32. The switch means 32 has, in this
example, six output connections 34, 36, 38, 40, 42 and 44, each of
which is effective to connect the output voltage from voltage
source 24 to a different particular one of the spark plugs in the
engine ignition means 12, depending upon which of input lines 46,
48, 50, 52, 54 and 56 is supplied with a trigger control signal for
triggering a particular switch means connection. More specifically,
input lines 46, 48, 50, 52, 54 and 56 conduct trigger control
signals from trigger means 58 to different ones of six
solid-state-switching circuits in the switch means, for example, to
actuate a particular one of the solid-state-switching circuits to
connect the output voltage of voltage source 24 to fire one of the
six spark plugs connected to one of the output lines 34, 36, 38,
40, 42 and 44. The six solid-state-switching circuits are
preferably provided by six silicon-controlled rectifiers.
Therefore, to produce firing in any one of the six cylinders
associated with engine ignition means 22, it is only necessary to
apply a trigger control signal to the appropriate one of the
trigger input lines 46-56 to render conductive the appropriate one
of the solid-state-switching circuits in switch means 32, thereby
permitting current to flow from the voltage source to the
appropriate one of the spark plugs in the engine ignition
means.
To generate the necessary trigger control signals at the desired
times in relation to the phase of engine operation for which fuel
combustion is desired, trigger means 58 having output leads 46-56
is provided, as previously stated. The trigger means preferably
comprises a magnetogenerator having a number of conductors equal to
the number of cylinders of the engine, spaced from each other
circumferentially around the center, and a rotor having
flux-generating means, which is rotatable about its center so as to
induce pulses sequentially in the several conductors, as will be
explained more fully hereinafter in connection with detail
schematic circuit diagrams. The rotor of the trigger generator may
be geared to crankshaft 26 of engine 20 by way of gearing 28 so
that trigger control signals are produced by the generator at a
rate in sequence with engine operation to actuate the switch means
to connect the voltage source to fire the appropriate spark plug.
The trigger means is arranged so that trigger control signals are
produced at its output lines on the proper lines for effecting the
desired sequence of the spark plug firing, this sequence being
selected in appropriate fashion for the particular engine
application according to principles well known in the art.
In other embodiments of the invention, as will be explained in
regard to the detailed schematic diagrams, a distributor may be
provided in the engine ignition means. In this instance, the
ignition means will have the output terminals of the distributor
connected to different ones of the spark plugs. Also, in a system
employing a distributor, the switch means need include only one
switching device connected to the voltage source and adapted to
connect the voltage source to the single input terminal of the
distributor. More specifically, the switching device, which
preferably is provided by silicon-controlled rectifier, would be
effective to connect the output voltage of voltage source 24 to the
input terminal of distributor in engine ignition means 22. In this
system, only one input line would be employed to conduct control
signals from trigger means 58 to the switching device in switch
means 32. The trigger means 58 in this arrangement would preferably
comprise circuit means including a coil supported by a stator and a
rotor having magnetic flux-generating means, which is rotated about
its center so as to have its magnetic field generate control
signals in the coil for triggering the switch means 32. The rotor
of the trigger means would be geared to the crankshaft of the
engine by way of gearing so that the trigger control signals are
produced by the trigger means at a rate in sequence with engine
operation to actuate the switch means to connect the voltage source
to the distributor, which has its rotor geared to the engine
crankshaft.
Ignition systems of the types schematically represented in FIG. 2
are preferably employed with a booster circuit generally designated
60, which preferably comprises pulse-generating means having
electronic circuitry for generating pulses of energy and for
applying the pulses to the voltage source or the trigger means or
both, as indicated in FIG. 2. The ignition booster circuit is
provided to apply pulses of energy, which may be current or voltage
pulses or pulses of magnetic energy, to the ignition system for
assuring igniting of fuel in the engine for optimum performance of
the engine. Preferably, the booster circuit provides voltage pulses
to the voltage source to assure that the output pulses on line 30
are of sufficient magnitude to fire the spark plugs of the engine
at low engine speeds. As shown in FIG. 2, the booster circuit is
coupled to the trigger means, which, as previously described,
preferably includes a magnetogenerator having a magnetic circuit.
In this arrangement, the booster circuit preferably includes a coil
to which pulses are applied to generate magnetic energy for
increasing the magnetic energy in the magnetic circuit of the
trigger generator, thereby assuring the production of suitable
signals by the trigger means applied to the control switch means to
properly actuate the switch means to permit the voltage source to
be connected to the ignition means.
Referring to FIG. 3, a detailed schematic diagram of a conventional
battery-type ignition system is shown employed with one form of a
booster circuit, generally designated 70, in accordance with the
present invention. The ignition system of FIG. 3 is of the general
type represented in FIG. 1. In FIG. 3 the ignition system includes
a storage battery 72 having its negative terminal connected to
electrical ground and its positive terminal connected to an
ignition switch 74. The ignition switch 74 connects one side of the
battery to one side of a timer circuit 76, which includes the usual
cam 78 and breaker points 80. A condenser 84 is normally connected
across the breaker points 80 to absorb reflected primary energy and
to suppress breaker contact arcing. The other side of breaker
points 80 is connected to primary winding 88 of an ignition
transformer 90. Secondary winding 92 of ignition transformer 90 is
magnetically coupled to the primary winding 88 and is connected
with the primary winding at terminal 94. The other side of the
secondary winding is connected in a conventional fashion through a
distributor, generally designated 96. Distributor contact arm 98 is
geared to rotate in synchronism with engine operation to
sequentially connect the voltage pulses from the secondary winding
to the output terminals 100, 102, 104 and 106 of the distributor to
fire each spark plug, generally designated 108, four spark plugs
being shown by way of example, one spark plug being connected to
each of the output terminals of the distributor in a conventional
manner.
The ignition system thus far described conforms to a conventional
battery-type ignition system employed in automobiles. In operation,
when the ignition switch 74 and breaker points 80 are closed,
current flows through the primary winding 88 of ignition
transformer 90. This current developes a magnetic field about both
induction transformer windings. When the breaker points 80 are
opened by cam 78, current flow is interrupted in primary winding 88
and the established magnetic field suddenly collapses. The
collapsing magnetic field induces a high-voltage pulse in secondary
winding 92 which is conducted through distributor 96 to fire the
appropriate one of the spark plugs 108.
In battery ignition systems of the type described above, these
systems function satisfactorily over normal working speeds of the
engine. However, difficulties have been experienced with these
systems in producing adequate ignition at relatively slow starting
speeds of the engine and, particularly, under unfavorable
conditions, such as cold weather which may cause partial deplete of
the battery charge and increased parasitic loads on the engine. In
order to provide increased energy for adequate ignition to start
the engine and to insure dependable operation of the engine at low
speeds, the booster circuit 70 is provided.
The booster circuit 70 in FIG. 3 comprises a battery 120, which has
its positive terminal connected to electrical ground and its
negative terminal connected to one terminal 122a of switch 122. The
other terminal 122b of switch 122 is electrically connected to a
transformer oscillator circuit, generally designated 124, which is
adapted to provide high-voltage output pulses to coupling circuit
126. The coupling circuit 126 in response to the pulses from the
oscillator circuit applies pulses of energy to the ignition system
to increase the energy delivered to the distributor 96 by the
voltage means of the ignition system. The coupling circuit 126
includes a rectifier circuit means, as will be explained more fully
hereinafter. The output of the coupling circuit is connected by
electrical line 128 to the ignition system between breaker points
80 and ignition transformer 90, as shown in FIG. 3.
The transformer oscillator circuit 124 comprises a transformer,
generally designated 134, having a primary winding 136 and two
secondary windings 138 and 140. Primary winding 136 has one end
connected to terminal 122b of switch 122 and its other end
connected to the collector of transistor 142, which has its emitter
connected to electrical ground. Also, there is connected between
terminal 122b of switch 122 and electrical ground a voltage divider
circuit comprising resistors 144 and 146. One end of secondary
winding 138 is connected between resistors 144 and 146, and the
other end of secondary winding 138 is connected to the base of
transistor 142. Secondary winding 140 of the transformer has one
end connected to electrical ground and its other end connected to
the coupling circuit 126. A zener diode 148 is connected between
the collector and emitter of transistor 142 to protect the
transistor from high transient voltages.
The coupling circuit comprises a diode 127 having its anode
connected to the output of secondary winding 140 of transformer 134
and having its cathode connected to the anode of silicon-controlled
rectifier 129, which has its cathode connected to output line 128.
The coupling circuit also includes a capacitor 130 which has one
plate connected to the cathode of diode 127 and its other plate
connected to electrical ground. Control terminal 129a of
silicon-controlled rectifier 129, which is responsive to a control
signal for actuating the rectifier to its conductive state, is
connected through biasing resistor 131 and zener diode 132 to the
cathode of diode 127 and capacitor 130, as shown in FIG. 3. The
zener diode 132 is so poled that it is normally nonconductive until
capacitor 130 is charged to a predetermined potential by the output
of transformer oscillator 124. Preferably, a resistor 133 is
connected between the control terminal and cathode of
silicon-controlled rectifier 129. Resistor 133 provides a
desensitizing resistance to make the rectifier less susceptible to
transient voltages which might turn on the silicon-controlled
rectifier at undesired times. The desensitizing of the
silicon-controlled rectifier may be provided internally so that
resistor 133 may be unnecessary.
In operation of booster circuit 70 of FIG. 3, when switch 122 is
closed, energizing the booster circuit to produce pulses for the
ignition system, transistor 142 is initially biased to its
conductive state by the potential applied to its base through
resistor 144 and secondary winding 138. With the transistor in its
conductive state, current flows through primary winding 136 and the
transistor and this results in a voltage pulse being induced in
secondary windings 138 and 140. The voltage pulse induced in
secondary winding 138 causes the transistor 142 to become
nonconductive. The transformer 134 steps up the voltage of battery
120 and the voltage is applied to the coupling circuit, which
applies pulses to the ignition system for assuring an ignition
pulse of adequate energy applied to the ignition transformer for
causing firing of the spark plugs. When the voltage induced in
secondary winding 138 by primary winding 136 drops below the
potential required to bias the transistor to its nonconductive
state, then the transistor returns to its conductive state to
permit current to flow through primary winding 136 and the
transistor, repeating the cycle to produce another high-voltage
pulse in secondary winding 140.
The high-voltage positive pulses induced in secondary winding 140
are conducted through diode 127 to charge capacitor 130. When the
voltage stored in capacitor 130 has reached a predetermined value
sufficient to cause breakdown of zener diode 132 rendering it
conductive, the control terminal 129a of silicon-controlled
rectifier 129 will have a positive potential applied thereto from
capacitor 130 so that rectifier 129 is actuated to its conductive
state to pass current. When silicon-controlled rectifier 129 is
actuated to its conductive state, capacitor 130 is suddenly
discharged through rectifier 129 and line 128 producing a pulse
applied to primary winding 88 of ignition transformer 90. The
high-voltage pulses thereby induced in secondary winding 92 are
applied to the appropriate one of the spark plugs through the
distributor to assure adequate firing of the spark plugs.
The arrangement of the booster circuit and ignition system of FIG.
3 comes within the overall block diagram arrangement shown in FIG.
1. Although the booster circuit is not connected to the voltage
means for the ignition system directly, it is connected between the
voltage means, which is provided by battery 72 and timer 76, and
the ignition transformer 90 so that the pulses from the booster
circuit are applied directly to the ignition transformer for firing
the appropriate spark plug through the distributor. The frequency
at which the oscillator in the booster circuit operates is
preferably sufficient to permit the occurrence of several
oscillations or pulses across each spark plug during the
appropriate firing interval for each particular spark plug. Thus,
the booster circuit with the ignition system of FIG. 3 provides
multiple sparks to the spark plug to assure easy starting of the
engine and optimum performance of the engine at low speeds. If a
good air-fuel mixture is not available at the time of the first
firing of the spark plug, there is now an opportunity for a second
or third spark to ignite a fresh portion of the charge in the
engine cylinder, thereby assuring complete combustion and easy
starting of the engine. The transformer oscillator 124 of the
booster circuit oscillates at a frequency, which preferably is on
the order of 3,000 cycles per second, to provide the multiple
pulses to each spark plug during each combustion stroke in the
engine cylinders. Of course, the pulse produced by the battery 72
and timer circuit 76 of the ignition system is still supplied to
the spark plug. After the pulse created by the ignition system
occurs, when breaker points 80 are opened, pulses are still
conducted to the ignition transformer from the booster circuit.
The switch 122 in booster circuit 70 may be provided by a switch
which is adapted to be operated manually so that upon starting the
engine and up to a desired engine speed, the operator can close
switch 122 to have the booster circuit provide multiple sparks to
the spark plugs. After the engine reaches a desired or
predetermined speed, or after the engine has had an opportunity to
warm up, the booster circuit can be deenergized by opening switch
122. Of course, switch 122 could be adapted to be opened and closed
automatically by a speed-sensitive coupling arrangement, for
example, so that switch 122 would be closed wherever the engine is
operating at a speed below a predetermined engine speed.
FIG. 3a illustrates an alternative form for a portion of the
booster circuit of FIG. 3. In the modified arrangement of FIG. 3a,
parts similar to those in the structure of FIG. 3 are identified by
the same number designator with the addition of primes thereto. The
primary difference between the circuits of FIGS. 3 and 3a lies in
the use of the battery of the ignition system to provide the power
for the booster circuit, rather than employing a separate battery
in the booster circuit. As shown in FIG. 3a, a separate battery for
the booster circuit has been eliminated and the battery 72' of the
ignition system is connected across the voltage divider circuit,
which comprises resistors 144' and 146'. Battery 72' has its
negative terminal connected by lead 160 to the grounded terminal of
resistor 146' in the booster circuit and has its positive terminal
connected by lead 162 to terminal 122a' of switch 122'. In this
arrangement, transistor 142' must be of the NPN type as shown in
FIG. 3a, rather than the PNP type as shown in FIG. 3, but the
oscillator circuit of FIG. 3a operates in the same manner as
described in regard to the oscillator circuit of FIG. 3. This
arrangement saves the use of a separate battery in the booster
circuit, and, otherwise, the booster circuit and ignition system
operate in the same manner as described in regard to the booster
circuit and ignition system of FIG. 3.
Referring to FIG. 4, there is shown a conventional magneto-type
ignition system with which a booster circuit, generally designated
200, is employed. The ignition system of FIG. 4 is of the general
type represented in FIG. 1 and includes a magnetoinduction
generator generally designated 202 for providing the pulses of
voltage to fire the spark plugs of the engine. The magnetoinduction
generator is of the conventional type having a rotor 204 with a
permanent magnet having north and south poles, the rotor being
driven through appropriate gearing by the engine crankshaft. The
magnetogenerator also includes two coils forming a transformer
having a primary winding 206 and a secondary winding 208. The
primary winding at one end is connected to electrical ground and at
its other end is connected to electrical ground through breaker
points 210, which are actuated open at appropriate times by cam
212, which is geared to the engine crankshaft, in a conventional
manner. A condenser 214 is connected across the breaker points to
absorb reflected primary energy and to suppress contact arcing at
the breaker points. Secondary winding 208 has one end connected to
electrical ground and its other end connected to a distributor,
generally designated 216. The distributor 216 is of the usual type
having a rotatable contact arm 220 geared to rotate in synchronism
with engine operation and adapted to sequentially contact its four
output terminals 222, 224, 226 and 228. A spark plug is connected
to each of the output terminals of the distributor, each spark plug
being designated 230.
In operation of the ignition system of FIG. 4, as the permanent
magnet rotor 204 rotates, an alternating magnetic flux is created
causing a buildup and collapse of flux lines within primary winding
206, resulting in an induced voltage within the primary winding. At
the point where flux reversal occurs in primary winding 206, the
maximum voltage is induced in the primary winding of the magneto.
At that instant, the breaker contacts 210 are actuated open by cam
212 and current flow is interrupted in primary winding 206. When
this occurs, the fast collapse of the magnetic field in the primary
winding 206 will induce a high voltage in secondary winding 208.
The voltage induced in secondary winding produces current which is
conducted through distributor contact arm 220 to fire the
appropriate one of the spark plugs in a conventional manner.
Usually, with a magneto-type ignition system as shown in FIG. 4,
the starter motor or cranking means is adapted under optimum
conditions to turn the engine, and hence the rotor 204 of the
magneto, at a speed sufficient to produce voltage pulses to fire
the spark plugs. However, under unfavorable conditions, such as
during cold weather when the parasitic load on the engine being
increased, the rate of turning the engine crankshaft may be greatly
reduced. Thus, it may be difficult to provide adequate ignition at
the relatively low starting speeds and until the engine reaches
normal operating speeds. Thus, it is desirable to employ the
booster circuit of the present invention with magnetoignition
system to provide additional energy to the spark plugs when
starting the engine.
The booster circuit 200 of FIG. 4 is schematically shown in a block
form and is preferably identical to the booster circuit 70 shown in
FIG. 3. Since the booster circuit 200 is preferably the same as
booster circuit 70 of FIG. 3, its operation will not be described
again in detail. As shown in FIG. 4 the booster circuit is
electrically connected to the ignition system between the breaker
points 210 and the primary winding 206 of the magnetogenerator. The
booster circuit 200 operates independent of the engine to provide
pulses of energy, voltage pulses, to the engine spark plugs. When
the breaker points 210 of the ignition system of FIG. 4 are closed,
the pulses generated by the booster circuit are connected directly
to ground. When the breaker points are opened by cam 212 and one of
the spark plugs is ready to be fired, the series of pulses from the
booster circuit is applied to primary winding 206, and, as a
result, a series of pulses is induced in the secondary winding and
conducted to the appropriate spark plug to be fired through the
distributor. When the breaker points are closed, the booster
circuit is again connected to electrical ground through the breaker
points 210. After the engine has started and reached a desired
speed or operating condition, the booster circuit can be
deenergized by opening the switch in the booster circuit, as
explained in regard to the booster circuit 70 in FIG. 3.
The ignition system shown in FIG. 4 is known in the art as a
high-tension ignition system. In high-tension ignition systems, the
high voltage sufficient to fire the spark plug is generated in a
secondary winding of the magneto and is conducted directly to the
spark plug. It should be appreciated that the booster circuit of
the present invention will work equally well with a low-tension
type of magnetoignition system, which has a voltage step-up
transformer located near the spark plug. In the low-tension type of
the magnetoignition system, the booster circuit would preferably be
connected to the winding of the magnetogenerator.
FIG. 5 is a schematic circuit diagram illustrating a
capacity-discharge ignition system with which a preferred
embodiment of a booster circuit 300 is employed in accordance with
the present invention. The capacity-discharge ignition system shown
in FIG. 5 is of the type shown in block diagram form in FIG. 2. The
ignition system portion of the circuit of FIG. 5 is of the type
shown and described in detail in U.S. Pat. No. 3,311,783, entitled
"Ignition System With Electronic Distribution and Control," of
Gibbs et al. and of common assignee herewith. To provide an
understanding of the ignition system with which the booster circuit
may be employed, the following brief description of the ignition
system is set forth. In the capacity-discharge ignition system of
FIG. 5, the engine spark plugs are divided into two sets, a first
set 302, 304, 306, 308, 310 and 312 and a second set 314, 316, 318,
320, 322 and 324, each set being fired from two capacitor pulsing
circuits. Of course, the number of spark plugs may vary and a
capacity-discharge ignition system with only one capacitor can be
employed, as described in U.S. Pat. No. 3,311,783, with the booster
circuit. It should be appreciated that each of the 12 spark plugs
shown in FIG. 5 is associated with a different cylinder of the
engine, and each responds to a voltage pulse applied across it
during the combustion stroke in the cylinder to ignite the fuel
therein. In FIG. 5, the pulses to fire the spark plugs are
generated in output winding, generally designated 325. The pulses
from output winding 325 are stored in capacitive means 328 and
capacitive means 330, the polarities of the voltages developed
across the respective capacitive means preferably being the same
polarity with respect to a reference potential, as will be
explained more fully hereinafter. The capacitive means 328 and 330
are discharged through individual spark plugs of the associated
first and second sets in synchronism with engine operation.
More specifically, spark plug 302, for example, has one of its
terminals grounded and its other terminal connected to one terminal
of secondary winding 332 of a voltage step-up transformer 334, the
other terminal of the secondary winding being connected to
electrical ground. Primary winding 336 of transformer 334 is
connected between electrical ground and the cathode of
silicon-controlled rectifier 338. A trigger coil 340a of a trigger
pulse generator (which will be described hereinafter) is connected
in series with diode 342 between the control terminal and the
cathode of silicon-controlled rectifier 338. The polarity of diode
342 is such that only the positive-going portion of a trigger
control signal generated in trigger coil 340a is applied to the
control terminal and this positive pulse serves to actuate the
silicon-controlled rectifier to its conductive state. A resistor
344 is connected between the cathode and control terminals of the
silicon-controlled rectifier and serves to maintain a relatively
low impedance between these terminals to stabilize the
silicon-controlled rectifier.
Capacitive means 330 is connected to the anode of
silicon-controlled rectifier 338 in ignition circuit 346 and each
of the anodes of the silicon-controlled rectifiers associated with
spark plugs 304, 306, 308, 310 and 312, as shown in FIG. 5. The
corresponding anode of each of the silicon-controlled rectifiers
associated with spark plugs 314, 316, 318, 320, 322 and 324 are
similarly directly connected to capacitive means 328. Each of the
11 other ignition circuits has the same construction and operation
as ignition circuit 346, and therefore only ignition circuit 346 is
described in detail.
The charging of capacitive means 328 and 330, which may be provided
by ordinary capacitors, is provided by output winding 325, which is
part of a conventional magnetoinduction generator (not shown). The
generator may have a rotating magnet armature which is driven in
rotation through appropriate gearing by the crankshaft of the
engine in the usual manner. In this arrangement, there is produced
across output winding 325 a voltage wave form of alternatingly
opposite polarity. Opposite ends of output winding 325 are
connected in a split-bridge rectifier circuit, generally designated
348. The split-bridge rectifier circuit comprises a first diode 350
having its anode grounded and its cathode connected to one end 325a
of winding 325, a second diode 354 having its anode connected to
end 325a of winding 325 and its cathode connected to capacitor 328,
a third diode 356 having its anode grounded and its cathode
connected to the other end 325b of winding 325 and a fourth diode
360 having its anode connected to end 325b of winding 325 and its
cathode connected to capacitor 330. The function of the
split-bridge rectifier circuit is to apply pulses to capacitors 328
and 330 to charge them alternatively to a positive voltage. Means
is provided for limiting the maximum amplitude of pulses stored by
each of the capacitors, comprising resistor 362 and zener diode 364
connected in parallel with capacitor 328, and resistor 366 and
zener diode 368 connected in parallel with capacitor 330.
The trigger control pulses for actuating each of the
silicon-controlled rectifiers to their conductive state for
permitting discharge of the associated capacitor for firing the
spark plugs in sequence are generated in the trigger coils
340a-340l, shown in FIG. 5. The twelve coils, one for each spark
plug of the engine, are provided in a trigger pulse generator which
has the twelve coils spaced circumferentially from one another
about a center. FIGS. 6 and 7 show a suitable preferred physical
form for a trigger pulse generator. In FIGS. 6 and 7 trigger pulse
generator, generally designated 400, has a magnetic rotor assembly,
generally designated 402, arranged to rotate about the axis of
shaft 404 in response to engine operation, that is, shaft 404 of
the rotor is geared to the crankshaft of the engine through
appropriate gearing (not shown).
Each of the 12 trigger coils 340a-340l is wound on a bobbin which
surrounds a core of magnetic material, such as coil 340a wound on
bobbin 406 which surrounds a core 408, shown in FIG. 7. Each of the
coil assemblies is supported by a U-shaped member of magnetic
material, such as U-shaped members 410 and 412 around coils 340a
and 340d, one U-shaped member being provided for each coil
assembly, each of which members extends from an apertured plate 414
around the remote end of the coil assembly and back to the plate
414. Each such U-shaped member provides an individual, separate,
short, low-reluctance path for magnetic flux from the core assembly
back to the apertured plate 414, by way of the two opposite sides
of the U-shaped member. Each of the coil and U-shaped member
assemblies is supported by the circular apertured plate 414 of
magnetic material. A circular aperture, such as aperture 416 for
coil 340a and its assembly, is provided in plate 414 in alignment
with each of the coil assemblies, each aperture preferably having a
diameter somewhat greater than that of the corresponding core for
each coil assembly.
As shown in FIGS. 6 and 7, the trigger coil assemblies, such as
associated with coil 340a, are mounted in line with the apertures
in the apertured plate 414 and electrical connection is provided by
way of leads, such as leads 418 and 420 for coil 340a, which are
connected in the ignition system circuit as shown in FIG. 5. The 12
apertures in apertured plate 414, one for each coil assembly, are
divided into two sets of six each, each set being disposed along a
circle of different radius. The shaft 404 provides an input drive
shaft which is mechanically coupled to the crankshaft to provide
rotating input for the rotor assembly 402. The rotor arm 422 is
double-ended in that the rotor arm extends in opposite directions
from the axis of rotation thereof, so as to provide two poles 424
and 426, pole 424 being positioned so as to pass closely over the
outer circle of apertures and pole 426 being arranged to pass
closely over the inner circle of apertures. The rotor assembly
includes a disc-shaped magnet 428 surrounding the rotor shaft 404
and supported for rotation about the axis of the shaft and is
located between the rotor arm 422 and aperture plate 414, as shown
in FIG. 7. The disc-shaped permanent magnet is faced polarized as
indicated thereon in FIG. 7. The two poles 424 and 426 of rotor arm
422 and the apertures in plate 414 are arranged so that they induce
pulses alternatively in the coils placed behind the two sets of
apertures, that is, first in a coil in the outer circle and then a
coil in the inner circle. A more detailed description of the
circuitry and construction of a trigger pulse generator as shown in
FIGS. 6 and 7 is disclosed in detail in the above-mentioned patent
of Gibbs et al.
In operation of the trigger pulse generator in FIGS. 6 and 7, when
the rotor arm 422 is rotated so as to move the poles 424 and 426
over the region of the apertured plate 414 between successive
apertures, the low magnetic reluctance of the plate 414 causes the
magnetic flux generated by magnet 428 to pass substantially
entirely from one pole, through plate 414 and back to a magnet 428
without substantial fringing of the magnetic flux through the coil
assemblies aligned with the apertures. However, when the pole 424
reaches the edge of one of the apertures, magnetic flux formerly
passing through the aperture plate begins to be transferred to a
path extending through the core, such as core 408 and thence
through the U-shaped member 410 back to the apertured plate and
magnet 428. As the pole 424 rotates further toward exact alignment
with the aperture, this flux through the core of the coil assembly
increases rapidly and thereafter decreases rapidly as the pole
passes from the center of the aperture to the trailing edge of the
aperture. The result is the generation of a positive pulse and a
negative pulse of voltage in sequence across the trigger coil.
When the positive and negative voltage waveform is produced across
each trigger coil, such as trigger coil 340a, the positive pulse is
applied to the control terminal of silicon-controlled rectifier
338, in this example, to render it conductive, thereby permitting
the associated capacitor 330 to discharge through rectifier 338 and
primary winding 336 of the ignition transformer to fire spark plug
302. The same action occurs in sequence in the 11 other ignition
circuits to fire each of the other 11 spark plugs in synchronism
with engine operation. Thus, the normal and desired order of events
with respect to any spark plug and its associated ignition circuit
is that first the associated capacitor should be charged to the
full value of the charging pulse applied thereto, then a trigger
pulse will render one of the silicon-controlled rectifiers
connected to that capacitor conductive to permit the capacitor to
discharge and fire the associated spark plug, and then the
silicon-controlled rectifier will become nonconductive so that the
next capacitor-charging pulse can be effective to charge the
capacitor again.
This type of high-frequency ignition system, that is, the
capacity-discharge ignition system, has proved to be very
advantageous and it is desirable to use such ignition systems for
replacement of conventional magnetoignition systems employing
breaker point apparatus and distributors. Under optimum conditions
the starting motor used to start the engine, with which the
capacity-discharge ignition system is employed, will turn the
engine at a rate to provide firing of the spark plugs. However, in
cold weather, the rate of turning of the engine crankshaft is
reduced so that the pulses produced in the magneto-output winding
325 may not be sufficient to provide proper firing of the spark
plugs and the trigger pulses produced in the trigger coils may not
be sufficient to properly actuate the silicon-controlled
rectifiers. In order to provide easy starting of the engine and
good operation up to normal engine operating speeds, booster
circuit 300 is preferably employed, the booster circuit operating
independent of engine speed to provide increased energy in the
ignition system to produce adequate ignition even under unfavorable
conditions.
The booster circuit 300 shown in FIG. 5 has some parts similar to
those of the booster circuit of FIG. 3 but is provided with further
circuitry to provide additional features. In the present instance,
the booster circuit comprises a battery 480 which has its negative
terminal connected to the common terminal of double-throw
single-pole switch 482 and its positive terminal connected to the
common terminal of double-pole single-throw switch 484. The
switches 482 and 484 are mechanically ganged to operate together so
that they connect the battery in the booster circuit, either as
shown by the solid line positions of the switches or the dotted
line positions of the switches in FIG. 5. In the solid line
position of switch 482, the negative terminal of the battery is
connected to one terminal 486a of switch 486, the other terminal
486b of switch 486 being electrically connected to a transformer
oscillator circuit, generally designated 488. The transformer
oscillator circuit is adapted to provide high-voltage pulses
through diodes 490 and 492 to charge capacitors 330 and 328,
respectively, of the ignition system. More specifically, diodes 490
and 492 are connected in parallel to the output of the transformer
oscillator circuit to conduct positive pulses of voltage to the
capacitors 330 and 328 in the ignition system circuit through lines
494 and 496, respectively.
The transformer oscillator circuit 488 comprises a transformer,
generally designated 500, having a primary winding 502 and two
secondary windings 504 and 506. The primary winding 502 has one end
connected to terminal 486b of switch 486 and its other end
connected to the collector of transistor 508, which has its emitter
connected to electrical ground. Also, there is connected between
terminal 486b of switch 486 and electrical ground, a voltage
divider circuit comprising resistors 510 and 512. One end of
secondary winding 504 is connected between resistors 510 and 512,
and the other end of secondary winding 504 is connected to the base
of transistor 508. Secondary winding 506 of the transformer has one
end connected to electrical ground and its other end connected to
the anodes of diodes 490 and 492, as shown in FIG. 5.
The operation of the transformer oscillator 488 is such that, when
switch 486 is closed and switches 482 and 484 are connected as
shown in solid lines in FIG. 5, transistor 508 is initially biased
to its conductive state by the potential applied to its base
through resistor 510 and secondary winding 504. With the transistor
in its conductive state, current flows through primary winding 502
and the transistor and results in voltage pulses being induced in
secondary windings 504 and 506. The voltage pulse induced in
secondary winding 504 causes the transistor to become
nonconductive. The high-voltage positive pulse induced in secondary
winding 506 passes through diodes 490 and 492 and charges
capacitors 330 and 328, respectively. The transformer 500 steps up
the battery voltage to a desired level for charging capacitors 328
and 330. When the voltage induced in secondary winding 504 by
primary winding 502 drops below the potential required to bias the
transistor to its nonconductive state, then the transistor returns
to its conductive state to permit current to flow through primary
winding 502 and the transistor, repeating the cycle to produce
another high-voltage pulse in secondary winding 506 for charging
the capacitors 328 and 330 to a desired level.
The booster circuit 300 provides pulses supplied through lines 494
and 496 to charge capacitors 328 and 330 to a sufficient energy
level to assure reliability of operation and optimum efficiency of
the engine during starting and at idling or low operating speeds of
the engine. The booster circuit thus provides pulses of energy, in
this case voltage pulses, having sufficient potential to adequately
charge the capacitors, independent of the operating condition of
the engine, to assure reliable operation of the engine up to a
desired or predetermined engine speed, at which time the booster
circuit can be deenergized by opening switch 486 in the booster
circuit.
In accordance with a further feature of the present booster circuit
of FIG. 5, means is provided by the booster circuit for increasing
the energy in the trigger pulse generator, which generates the
pulses in the trigger coils 340a-340l to actuate the associated
silicon-controlled rectifiers to their conductive state for
permitting discharge of the associated capacitor therethrough to
fire the associated spark plug. Thus, the booster circuit provides
means for increasing the energy in the trigger pulse generator to
assure the generation of a reliable trigger signal in the trigger
coils for efficient and reliable operation of the ignition
system.
The preferred means in the booster circuit for providing additional
energy in the trigger pulse generator comprises a coupling or
rectifier circuit, generally designated 520, and a booster coil 522
connected to the output of the coupling circuit. The coupling
circuit 520 comprises a diode 524 having its anode connected to the
output of secondary winding 506 of transformer 500 and having its
cathode connected to the anode of silicon controlled rectifier 526,
which has its cathode connected to output line 528. Output line 528
is connected to one side of booster coil 522, which has its other
side connected to electrical ground. The pulse-forming circuit 520
also includes a capacitor 530 which has one plate connected to the
cathode of diode 524 and its other plate connected to electrical
ground. Control terminal 526a of silicon-controlled rectifier 526,
which is responsive to a control signal for actuating the rectifier
to its conductive state, is connected through biasing resistor 532
and zener diode 534 to the cathode of diode 524 and capacitor 530,
as shown in FIG. 5. The zener diode 534 is so poled that it is
normally nonconductive until capacitor 530 is charged to a
predetermined potential by the output of transformer oscillator
488. Preferably, a resistor 531 is connected between the control
terminal and cathode of silicon-controlled rectifier 526. Resistor
531 provides a desensitizing resistance to make the rectifier less
susceptible to transient voltages which might turn on the
silicon-controlled rectifier at undesired times.
In operation of the coupling circuit 520 and booster coil 522, the
pulses which are generated in secondary winding 506 are conducted
through diode 524 to charge capacitor 530. When the voltage stored
in capacitor 530 has reached a predetermined value sufficient to
cause breakdown of zener diode 534 rendering it conductive, the
control terminal 526a of silicon-controlled rectifier 526 will have
a positive potential applied thereto from capacitor 530 so that
rectifier 526 is actuated to its conductive state to pass current.
When silicon-controlled rectifier 526 is actuated to its conductive
state, capacitor 530 is suddenly discharged through the
silicon-controlled rectifier and booster coil 522. The pulse
supplied to booster coil 522 creates a magnetic flux to provide
additional energy in the trigger pulse generator, as will be
explained more fully hereinafter. Capacitor 530 charges in response
to positive pulses generated in secondary winding 506 of
transformer 500 and discharges when a particular level of charge is
reached determined by zener diode 534.
The booster coil 522 in FIG. 5 is shown in detail in the trigger
pulse generator 400 of FIG. 7. In the trigger pulse generator of
FIG. 7, booster coil 522 is wound on a bobbin 550 of nonmagnetic
material, which encircles the permanent magnet 428 and is supported
by apertured plate 414. The booster coil 522 is positioned between
apertured plate 414 and rotor arm 422 and is wound on the bobbin in
a direction such that the pulses from the pulse-forming circuit
applied to the booster coil create a magnetic flux, which increases
or boosts the magnetic flux of permanent magnet 428 passing through
rotor arm 422 for inducing pulses in the trigger coils. As
indicated in FIG. 7, one end of booster coil 522 is grounded and
the other end is connected by line 528 to pulse-forming circuit
520, as schematically shown in FIG. 5. When the engine is started
and the rotor arm 422 is rotated, pulses are preferably applied to
booster coil 522 from the booster circuit to increase the magnetic
flux from the permanent magnet passing through rotor arm 422,
thereby increasing the magnetic energy-inducing pulses in the
trigger coils.
In this arrangement, the magnitude of the control signals generated
in the trigger coils is increased to assure that the associated
silicon-controlled rectifier is reliably triggered for having the
main storage capacitors of the ignition system discharged to fire
the spark plugs in synchronism with engine operation. Thus, the
booster coil provides pulses of energy to the magnetic circuit of
the trigger pulse generator for increasing the magnetic energy in
the magnetic circuit for assuring the production of a suitable
signal by the appropriate trigger coil applied to the control
terminal of its associated switch means when the engine is started
and during engine operation to a desired speed. The transformer
oscillator described in FIG. 5 oscillates at a frequency on the
order of 3,000 cycles per second to provide the desired frequency
of output pulses from the pulse-forming circuit applied to the
booster coil.
It should be understood that the booster coil associated with the
trigger pulse generator could be positioned in the generator at a
number of different locations, as long as the magnetic flux created
by current in the booster coil passes through the magnetic circuit
of the trigger pulse generator to increase the magnetic flux
created by the permanent magnet. Of course, in other arrangements
of trigger pulse generators, the booster coil would be positioned
differently but would perform the same function of providing
additional flux in the magnetic circuit of the generator to
increase the overall magnetic flux in the magnetic circuit.
In accordance with a further feature of the present invention,
means is provided for charging the battery of the booster circuit
from the ignition system, once the engine is operating
satisfactorily within its range of normal operating speeds. More
specifically, the charging circuit for the battery is provided by
having terminal 484b of switch 484 connected by line 560 to line
496, which is connected to capacitor 328 and one side of output
winding 325 through diode 354. The charging circuit is completed by
having terminal 482b of switch 482 connected to electrical ground
by way of the series circuit provided by diode 562, resistor 564
and zener diode 566. When the mechanically ganged switches 482 and
484 are placed in the dotted line, alternative positions of the
poles as shown in FIG. 5, the charging circuit is completed for
charging battery 480. In this arrangement, the pulses from the
ignition system are supplied to the battery for charging the
battery. The charging circuit for the battery is, of course,
optional. The battery might be charged from any external DC source
or a recharging circuit may be completely omitted. Further, the
direct current source needed for the booster circuit could be
provided by some other means than a battery, such as, a rectified
AC source of power.
It should also be appreciated that it may not be necessary to have
the booster circuit both charge the main storage capacitor of the
ignition system and provide additional energy to the trigger pulse
generator, as described in regard to FIG. 5. These features of the
booster circuit can both be provided or they may be employed
independently as required by the particular application and
operation of the ignition system and engine. Furthermore, after the
engine has been started and is operating as desired, the booster
circuit can be deenergized by opening switch 486 or by moving the
poles of switches 482 and 484 to the alternative position shown in
FIG. 5 for charging the battery. Moreover, after the engine has
been started and is operating as desired, the booster circuit can
be physically removed by disconnecting the booster circuit from
lines 494, 496 and 528 and the booster circuit can be employed in
another location with another ignition system, as desired.
There is shown in FIG. 8 a schematic circuit diagram illustrating
another overall ignition system with which a booster circuit in
accordance with the present invention is employed. In this example
of FIG. 8, the booster circuit employed is preferably generally the
same as the booster circuit shown in FIG. 5 so that the booster
circuit in FIG. 8 is shown in block diagram form. In FIG. 8, parts
of the booster circuit, similar to those of the booster circuit of
FIG. 5, are identified by the same number designators with the
addition of primes thereto. The only difference between the booster
circuit 300' employed in FIG. 8 and the booster circuit 300 of FIG.
5 is that the battery charging portion of the booster circuit of
FIG. 5 is not needed in the FIG. 8 arrangement and that diode 492
and line 496 of FIG. 5 are not needed in the FIG. 8 arrangement
since only one line (494' in FIG. 8) connecting the output of the
transformer oscillator to the ignition system is required, as
shown.
The overall ignition system represented in FIG. 8 is of the type
shown and described in detail in U.S. Pat. No. 3,034,018 of M. I.
Rosenberg, entitled "Transistorized Breakerless Ignition System,"
and of common assignee herewith. To provide an understanding of the
ignition system of FIG. 8, the following brief description is set
forth. The ignition system comprises a magnetic pulse generator,
generally designated 600, having a rotor 602, which has a
face-polarized permanent magnet positioned between plates 604 and
606. Each of the plates provide pole pieces having radially
extending portions which provide pole faces of one polarity around
the rotor, the pole faces of pole piece 604 being staggered around
the rotor with the pole faces of pole piece 606 to provide pole
faces of alternate polarity around the rotor, as shown in FIG. 8.
The pole faces of alternate polarity are located in pairs around
the rotor, one pair being provided for each cylinder of the
engine.
The rotor of the pulse generator has associated therewith a
distributor, generally designated 610, which has eight output
terminals, designated 612a-612h, one for each cylinder of the
engine. Each output terminal of the distributor is connected to one
of the eight spark plugs 614-628. Distributor rotor arm 630
alternately contacts each of the output terminals to conduct pulses
to the spark plugs to fire the spark plugs in synchronism with
engine operation.
Adjacent the periphery of the magnetic rotor 602 there is provided
a control coil 632 wound on the center leg of a generally E-shaped
stator member 634 fixedly positioned in close proximity to the
projections providing the pole faces of the rotor to complete a
magnetic circuit for each of the pairs of alternate polarity poles
once each revolution of the rotor. The spacing of the legs of the
generally E-shaped stator generally corresponds to the spacing
between each of the pairs of pole faces provided by the rotor.
The distributor contact arm which rotates with the rotor structure
of magnetic pulse generator 600 is connected to secondary winding
636 of voltage step-up transformer 638, the primary winding 640 of
the transformer being connected to a switching circuit, generally
designated 642.
The ignition system further includes a source of voltage, which may
be provided by a DC battery 644 having its negative terminal
connected to electrical ground through ignition switch 646. The
positive terminal of battery 644 is connected to the anode of diode
648 which has its cathode connected to the switching circuit
642.
The switching circuit 642 comprises a power transistor 650, which
has its emitter connected to the cathode of diode 652, the anode of
diode 652 being connected to the cathode of diode 648. The
collector of transistor 650 is connected to primary winding 640 of
voltage step-up transformer 638. Biasing resistor 654 is connected
between the anode of diode 652 and the base of transistor 650 to
stabilize the power transistor. The base of transistor 650 is
connected to the emitter of triggering transistor 656, which has
its collector connected to electrical ground. The base of
triggering transistor 656 is connected to one side of control coil
632, the other side of control coil 632 being connected to the
emitter of triggering transistor 656. A zener diode 658 is
connected between the base and emitter of transistor 656.
In operation of the ignition system of FIG. 8, when ignition switch
646 is closed, the starting motor for the engine, with which the
ignition system is employed, turns the engine crankshaft, which in
turn rotates the pulse generator rotor 602. The rotating trigger
rotor 602 induces a pulsating voltage in control coil 632. The
voltage induced in control coil 632 causes trigger transistor 656
to rapidly switch to its conductive state, which, in turn, causes
power transistor 650 to rapidly switch to its conductive state.
With transistor 650 in its conductive state, a current transient is
supplied to the primary winding 640 of transformer 638 from battery
644, the current transient causing a voltage transient in the
primary of the transformer which induces a high voltage in
secondary winding 636 which is conducted through distributor rotor
arm 630 to the appropriate one of the spark plugs in synchronism
with engine operation.
Upon starting the engine and at slow engine speeds, the ignition
system of FIG. 8 may not initially provide adequate energy to fire
the spark plugs under unfavorable conditions. In addition, the
voltage generated in control coil 632 by the distributor rotor,
which is geared to the engine crankshaft, may not be sufficient to
reliably actuate the switching circuit. In order to provide
sufficient energy in the ignition system of FIG. 8 for reliable
operation upon starting the engine and at low engine speeds, the
booster circuit 300' is preferably employed. As shown in FIG. 8,
output line 494' from booster circuit 300' is connected in the
ignition system between the cathode of diode 648 and the anode of
diode 652. Diode 648 prevents the battery from absorbing the pulses
of energy supplied from the booster circuit for firing the spark
plug.
In this arrangement, when the switching circuit is conductive, that
is transistor 650 is conductive, the pulses from the booster
circuit are supplied to the primary winding of transformer 638 and
to the spark plug of the engine through distributor rotor arm 630
for firing the spark plug. Since the output of the booster circuit
300' provides a series of high-frequency pulses, more than one
pulse will be supplied to the spark plug during each firing
interval so that a series of sparks is obtained at the spark plug
for having better and reliable combustion in the engine cylinders
for starting and operating the engine.
Further, in accordance with the present booster circuit, output
line 528' from the booster circuit, which is connected in the
booster circuit to the output of the coupling circuit as described
in regard to the booster circuit of FIG. 5, is connected to booster
coil 522' wound on a bobbin supported by rotor 602, as shown in
FIG. 8. More specifically, line 528' is connected to an insulated
conductive ring 670 through an appropriate brush and ring 670 has
one end of coil 522' connected thereto. Ring 670 is supported by
plate 604. The other side of booster coil 522' is connected to
insulated ring 672, which is supported by plate 604 and is
connected through an appropriate brush to electrical ground as
indicated in FIG. 8. Booster coil 522' is wound on a bobbin and
positioned between the disc-shaped permanent magnet of the rotor
and plate 604. The pulses from the booster circuit supplied to the
booster coil, which is wound in an appropriate direction, produces
in the booster coil a magnet flux to increase or boost the magnetic
flux in the magnetic circuit of the pulse-generating rotor, thereby
increasing the magnitude of the pulses induced in control coil 632
to assure switching of the switching circuit 642. Hence, booster
coil 522' serves to improve the trigger signal induced in the
control coil to assure reliable operation of the ignition system at
desired predetermined engine speeds.
As indicated in regard to FIG. 3a, since the ignition system of
FIG. 8 employs a battery, the battery 644 may be connected to the
booster circuit in a manner similar to the battery in FIG. 3a for
providing the power to the booster circuit, so that a separate
power source would not be required in the booster circuit.
It should be appreciated that the booster circuit of the present
invention can be employed with a wide variety of ignition systems
to assure reliable operation of the ignition system. The present
booster circuit can be employed to provide multiple sparks for
firing the spark plugs of the engine cylinders and can boost the
energy of a capacity-discharge ignition system for adequate firing
of the engine spark plugs. Furthermore, the present invention can
be employed to increase the energy in the magnetic circuit of a
trigger pulse generator in ignition systems which employ such an
arrangement. Furthermore, the booster circuit can be provided with
means for permitting charging of the power source in the booster
circuit, as illustrated in regard to the capacity-discharge
ignition system of FIG. 5. The present booster circuit eliminates
the conventional vibrator apparatus which is employed in previous
booster systems to increase the energy in the ignition system. The
booster circuit of the present invention is compact and reliable
and employs a few simple circuit components providing an
inexpensive system capable of trouble-free operation.
While the present invention has been described with particular
reference to specific embodiments thereof in the interest of
complete definiteness, it will be understood that it may be
embodied in a large variety of forms diverse from those
specifically shown and described without departing from the scope
and spirit of the invention as defined by the appended claims.
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