Note: Descriptions are shown in the official language in which they were submitted.
CROSS-REFERENCES TO RELA~ED APP~ICATIONS
This invention is related to the following prior
applications which define inventions by the same inventor:
S.N. 157,608 filed 11/27/72
S.N. 165,988 filed 03/13/73 now Pat. 997,824 09/28/76
S.N. 169,583 filed 04/26/73 now Pat. 1,000,501 11/30/76
S.N. 191,913 filed 02/06/74 now Pat. 1,010,946 0~/27/77
BACKGROUND OF THE INVENTION
Field of the Invention
This invention concerns ignition systems in gen-
eral. More specifically, it relates to an improved ignition
system for internal combustion engines, which employs a
continuous-wave high-frequency spark generator. The in-
vention is particularly related to improvements for the ~
foregoing type of high-frequency spark-generating system. ~-
Description of the Prior Art
: .
While there are a considerable number of known
systems for developing continuous-wave spark signals that
are for use in internal combustion engines, and such sys-
tems sometimes include the use of photoelectric engine-
timed controls for introducing the spark signals, they
have been found to have a drawback in that the photo-
electric control introduces a substantial time delay in
the initial response. Such a time delay is especially
detrimental as high speeds are introduced in the engine,
because the delay is relatively constant and, consequently,
involves greater crank-angle engine-timing delays as the
speed is increased.
Consequently, it is an object of this invention
to provide an improvement for the control portion of a -
high-frequency sparks system that involves photoelectric
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engine-timed controls. The improvement acts to greatly
reduce delays caused by response o~ the photoelectric ele-
; ments.
Another ob~ect of the invention is to provide asystem for use with high-frequency continuous-wave spark
generators, particularly of the type that employs square-
wave oscillators. Such a system has been found to gene-
rate large amounts of radio-frequency signals~ and since
theæe tend to cause spurious actions in the control sys-
tem, the elimination of radio-frequency energies from the
control system becomes an important feature.
SoUMA~Y OF THE INVENTION
Briefly, the invention relates to an improve-
ment that is part of a combination with an ignition sys-
tem for internal combustion engines, wherein said system
employs controlled-du~ation continuous-wave high-frequency
spark energy. me said spark ener~y is generated by an
oscillator having an output transformer, and having a con-
trol winding thereon for starting and stopping the oscil- -
20 lator at the beginning and end of each spark interval. me ~ -
combination also includes electronic switch means connected
in series with said control winding for breaking and maklng
a loading circuit which includes said control winding. The
- said spark intervals are determined by photoelectric engine-
timed means including a phototransistor, and the said elec-
tronic switch means has a control circult therefor, in-
cluding said photoelectric engine-timed means. In rela-
tion to the foregoing combination, the invention concerns
an improvement which comprises means incorporated with said
control circult for minimizing the response time of said
phototransistor.
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Again, briefly, the invention concerns an im-
provement related to a combination with an ignltion system
for an internal combustion engine, wherein sald system em-
ploys controlled-duration continuous-wave high-frequency
spark energy. me said spark energy is created by a square-
wave oscillator having an output transformer, and having
a control winding thereon for starting and stopping oscll-
lation of said oscillator at the beginning and end of each
spark interval. me combination also comprises electronic
switch means connected in series with said control winding
for breaking and making a loading circuit which includes
said control winding. me said spark intervals are de-
termined by photoelectric engine-timed means compriqing a
light-emitting diode and a phototransistor. The said elec-
tronlc switch means has a control circuit therefor which
includes said phototranslstor. In combination with the
foregoing system, this invention concerns the improvement
which comprises first circuit means for connecting said
phototransistor in a common collector con~iguration rela- - -
tive to said control circuit, and second circuit means for
connecting the emitter of said phototransistor to the emit-
ter of an input transistor of said control unit. me said
second circuit means includes a radio-frequency ~ er for
blocking radio-frequency signals generated by said spark
energy. The improvement also comprises third circuit means
including a temperature-sensitive resistor for energizing
said light-emitting diode, in order to compensate for
changes in ambient temperature at the engine-timed means.
It also comprises fourth circuit means including saidlight-
emitting diode having a predetermined forward voltage drop,
and connecting said diode to the base of said input `~-
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transistor, all whereby said ignition system has improved
response to the engine-timed spark-control means in
giving temperature compensation and radio-frequency
signal rejection.
BRIEF DESCRIPTION OF THE DR~WINGS
The foregoing and other objects and benefits
of the invention will be more fully set forth below in
Z connection with the best mode contemplated by the in-
ventor of carrying out the invention, and in connection
with which there are illustrations provided in the
drawings, wherein:
Figure 1 is a schematic circuit diagram illustrat-
ing a complete system according to one modification of
the invention;
Figure 2 is another circuit diagram illustrating
a different modification of the control-circuit portion
of a system like that illustrated in Figure l; and
Figure 3 is yet another circuit diagram illustrat-
ing only the engine-timed photoelectric portion of a
third modification of the system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, it will be noted that
the complete ignition system illustrated includes the
basic elements like those shown in one or more of the
above-noted copending applications. It will be suf-
ficient to note that the system illustrated in Figure
1 includes an oscillator 11 that is enclosed within a
dashed-line box 12, and which employs an output trans-
former 13 with a control winding 14 thereon.
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Similarly, the system includes a conventional
ignition switch 17 which is shown in a dashed-line box
18 that includes a battery 19 therein. It will be under-
stood that the physical locations of the battery and
ignition switch are usually quite widely separated on an
automobile. The battery 19 supplies power to the
oscillator 11 via a permanent circuit connection 22. Also,
when the ignition switch 17 is turned on, the battery
19 supplies DC power (via a circuit connection 23) to
parallel circuits. One includes a connection 24 for
energizing the control winding 14, and the other includes
a connection 25 that is for energizing a relay 26 that is
shown enclosed in a dashed-line box carrying that re_
ference number.
The control winding 14 is in series with an
electronic switch, i.e., a transistor 29, which deter-
mines whether the winding 14 is AC-short-circuited or
not. At the same time, when the transistor 29 is con-
ducting, the circuits include application of a DC bias
for creating a core set on the transformer 13. The
transistor 29 is controlled for determining whether it
is conducting or nonconducting by means of a control
circuit 32 that includes all of the circuit elements
between the base connection of transistor 29 and the
output circuit of a control-circuit-input transistor
35.
The input transistor 35 is controlled by a
photoelectric engine-timed unit 38 that includes a
light-emitting diode 39 and a phototransistor 40. It
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1038444
will be appreciated that in the system as illustrated
in Figure l, the unit 38 will be physically located
on the distributor unit of the engine, and there will -~
be included a shutter (not shown) which is driven by
a timing shaft (not shown) from the engine so as to
determine the engine-timed intervals for producing
spark energy.
It will be observed that the phototransistor
40 is connected in a common collector configuration
relative to the control circuit 32. Thus, while a
"common collector" circuit designation often connotes
a grounded collector, in this instance the common cir- :~
cuit to which the collector of phototransistor 40 is
connected, is a positive DC circuit that is a common
circuit of the control circuit 32. On the other hand,
the emitter of phototransistor 40 is connected via a
circuit connection 43 to the base of the transistor 35.
Transistor 35 has a DC bias applied to it such that it
is just below the cut-off point in the absence of any
signal from the emitter of phototransistor 40. Such
bias is obtained by having a pair of resistors 46 and 47
connected in series from the common DC supply (DC
potential on a circuit connection 50) to ground. The
midpoint between resistors 46 and 47 (which, together,
: act as a potentiometer1 is connected to the base of the
transistor 35. In this manner, the response time of tran-
sistor 40 to the receipt of radiant energy from the light-
emitting diode 39, is greatly reduced since only a small
voltage rise is needed to cause transistor 35 to conduct.
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An ignition system according to this invention
may be made operative over a full range of te~perature
conditions that might be encountered with internal combus-
tion engines, by including in the circuit for energizing
the light-emitting diode 39 a temperature~sen~itive resis-
tor 53. mis is because of the characteristics of light-
emitting diodes and phototransistors. mus, the radlant
energy emitted by a light-emitting diode is a ~unctlon of
the current passed through the ~unction. If too much cur-
rent is passed through the ~unction, it will overheat, andthe diode will be destroyed. The safe current level of
the diode will be determined by the ability of the ~unction
to dissipate heat. merefore, the safe current at high
; ambient temperatures is much lower than when the ambient
temperature is low. Also, the light-emittlng efficiency
of the light-emitting dlode lncreases as the junction tem-
perature decreases, so that at low ambient temperatures
more radlation will be emitted for the same ~unction cur-
rent than when the ambient temperature is increased. In
20 addition, a phototransistor becomes less sensitive as the ~ ~ -
temperature is decreased, and more sensitive as the tem-
perature rises, which tends to partially compensate for the
opposite changing amount of radiation from the light-emit-
ting diode. However, in practice it is found that the
total effect is not exactly offsetting, and at low ~mbient
temperatures it is necessary to increase the light-emitting
diode's output to compensate sufficiently for the lack of
sensitivity of the phototransl~tor. Similarly, at high
ambient temperatures, the phototransistor increases in gain
faster than the light-emltting diode loses efficiency. Con-
sequently, the ~unction current of the light-emltting diode
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may be reduced at higher temperature while still maintain- -
ing the total or combined sensitivity. At the same time,
the reduced current tends to keep the junction cooler
which contributes to maintaining the emitting efficienoy
high.
It has been found that the system using the tem-
perature-sensitive resistor 53 will operate satisfactorily
within an ambient temperature range of ~rom about -45 F.
to about ~237.5 F.
It has been discovered that in the type of con-
tinuous-wave high-frequency ignition system according to
this invention, largely because the oscillator is square-
wave in nature, a large amount of radio-frequency energy
is generated at the park gaps during each of the sparking
intervals. Such radio-frequency energies are radiated and
tend to be applied at various points in the whole circuit.
Consequently, there is a tendency to introduce undesired
signals after each starting of the oscillator, and these
tend to cause reenergization, or continuation of the 08-
cillation beyond the normal stopping thereof. mis tends
to cause untimed spark ignitions in additon to overload-
ing, and thus tending to burn out various elements of the
system, e.g., the electronic switch (transistor) 29.
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In order to avoid the foregoing undesired condi-
tions, there is included in the circuits with the input
transistor 35 a radio-~requency choke coil 56 located be-
tween the emitter of transistor 35 and ground. mis pre-
vents radio-frequency signals from reaching the base of a
transistor 64. Also, there is a capacitor 68 connected
~rom the collector o~ transistor 35 to ground which shunts
radio-frequency signals ard, in addition, there is another
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1038~44 .,
capacitor 67 connected from the collector of input tran- -
sistor 35 to the base thereof, which causes a substantial
amount of negative feedback to the radio-frequency signals.
In addition to the radio-frequencv blocking
effects, there is a coil 57 connected in the output circuit
of the transistor 35, which is designed to improve the
response of the control system to the desired signal fre-
; quency, e.g., to be resonant at about 20,000 Hertz. There
is a resistor 60 connected across the coil 57 so as to
critically damp the resonant effects in order to prevent
` any undesired ringing.
Figure 2 illustrates a modification of the con- ;
trol-unit portion of the system, and for the purpose of
ade~uate orientation, the same basic control circuit 32
as is illustrated in Figure 1, is shown again in Figure -
2. Thus, the transistor 29 is illustrated at the out-
put end of the control circuit 32 and, of course, it con~
trols the starting and stopping of the oscillator 11
(see Figure 1) by means of controlling AC-short-circuit
conditions for the control winding 14 (see Figure 1) in
the same manner as indicated above in connection with
Figure 1. Also, the relay 26 and circuit connections 25
and 23 which were indicated in Figure 1, are shown again
in Figure 2.
In Figure 2, the fast-reaction circuit related to
the phototransistor 40 (see Figure 1) takes a modified form
over that illustrated in Figure 1. Thus, in Figure 2, the
emitter connection 43 (see Fig. 1) from transistor 40 (Fig.
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1) ls applied to a terminal 71 that has a circuit connec-
tion 72 leading therefrom to one end of a radio-frequency
choke coil 73. The other end of the coil 73 leads direct-
ly to the emitter of a PNP transistor 76. The base of
transistor 76 is connected to the midpoint between a re-
sistor 77 and a diode 78, which diode is one having a pre-
determined forward voltage drop in order to set the voltage
on the base of transistor 76 at a desired level. me out-
put of transistor 76 goes to the control circuit 32 and,
as illustrated, this ls via a circuit connection 81 that
goes to the base of another transistor 82.
It has been discovered that by making use of the
lllustrated circuit, including the PNP transistor 76, a
; greatly reduced response time from the phototransistor 40
(FIG. 1) may be had. Because of the characteristics of
translstors generally, and lncluding phototransistor~,
there has been a difficulty encountered in high-frequency
applications by reason of the load-dependent frequency re-
sp~nse in regard to the phototransistors. Since a photo-
transistor is a current ~ource, it is desirable to use a
` large-load resistance to develop maximum output voltage
or to have high sensitivity. However, large-load resis-`
tances limit the frequency range which would mean longer
response time for an ignition system. Thus, in the past,
it has been considered necessary to compromise, i.e., trade
voltage for speed, or Yice versa. ~ut, by applying the
illustrated circuit to a control ~ystem according to this
invention, a deslred reduction in response time ls created.
me coil 73 ls part of a radlo-frequency filter,
which includes a parallel re~istor ô5, along with a pair of
capacitors 86 and 87, which are connected to ground and to
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the ends of the coil 73 as well as to the ends of resistor
85.
FIG. 3 illustrates a modi~ication o~ the photo-
transistor circuit portion o~ the control circuit. It is
applicable particularly to a system like tha~ shown in FIG.
2. This arrangement permits elimination o~ a resistor,
along with making use of the light-emitting diode for two
purposes so that the diode 78 may also be elimin~ted.
mus, in FIG. 3, there is a llght-emitting diode
90 that is connected for energization from a circuit con-
nection 91 which corresponds to circult connection of FIGS.
1 and 2. Also, there is a temperature-sensitive reslstor ~: :
94 that corresponds to resistor 53 o~ FIG. l, and the radia- :
tion of light from diode 90 is directed toward a phototran-
sistor 95 in the same manner as was described in connectlon
with translstor 40 o~ FIG. l.
In this instance, phototransistor 95 has its emit-
ter connected directly to the emitter of a PNP transi~tor
: 98 that corresponds with transistor 76 of FIG. 2. In the
20 FIG. 3 modlfication, the base of transistor 98 is connected -
via a connector 99 to a ~unction between resistor 94 and .
diode 90. me collector of transistor 98 goes directly to
the base of another transistor 102 which corresponds to the
transistor 82 of FIG. 2.
- By making use of a circuit according to FIG. 3,
the resistor 77 (FIG. 2) as well as the diode 78 (FIG. 2)
may both be elimlnated slnce resistor 94 and the light~
emlttlng diode 90 take thair place. However, it should be
noted that wh~re the circuit as indicated in FIG. 3 i8 em-
ployed, the elements shown must be physically located on or
at the dlstrlbutor (not shown) o~ the engine, in the manner
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indicated in connection with FIG. 1. In other words, when
the FIG. 3 modificatlon is employed, there is a dlstributor- ~
located unlt 105 which i8 indicated by the dashed lines -
Y~ around the circuit elements illustrated in FIG. 3.
While the invention has been described above in
3 considerable detail and in accordance with the applicable
statutes, this is not to be taken as ln any way limiting
the lnvention, but merely as being descriptive thereof.
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