Note: Descriptions are shown in the official language in which they were submitted.
~235~
FIELD OF T~E IN~ENTION
. _
This invention relates to control systems for
the protection of internal combustion engines.
BACRGROUND TO THE INVENTION
The need to protect internal combustion en-
gines from damaging or destructive operating conditions
is well known. Such need can become particularly impor-
tant in the case of high performance engines which not
only themselves may be costly and expensive to maintain,
repair or replace, but which may also be used to operate
sophisticated and costly equipment, the downtime and
repair of which is preferably kept to a minimum.
Various devices or systems for the protection
of internal combustion engines are known in the prior
art. Some of such devices are essentially dedicated to
a single task; for example, the tilt detector disclosed
in U.S. Patent No. 3,882,957 (Fritz) entitled "Vehicle
Roll-Over Protection Device", granted on May 13, 1975.
Here, a tilt detecting apparatus was designed to effect
vehicle engine shutdown if the vehicle rolled over or
tilted more than a predetermined amount.
Other known sensing or detecting devices which
may be used to monitor and sense engine operating condi-
tions or its immediate environment include devices for
monitoring and sensing conditions or parameters such as
engine or other temperatures, oil pressures, rpms,
water, fuel (fuel leakage), fluid levels (water or other
coolant), fire, and so forth. Signalling from such de-
vices may readily be utilized to effect engine shutdown
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~Z3577~
based upon the presence or absence of a signal having a
magnitude above or below a predetermined threshold
value.
In contrast to devices or systems dedicated to
a single task, some known engine protection devices or
systems are designed to effect engine shutdown if any
one of more than one of the previously described devices
or systems, operating concurrently to control a particu-
lar engine, produces a signal that dictates engine shut-
down. An example of such a system is disclosed in U.S.
Patent No. 4,429,670 (Ulanet) entitled "Engine Protec-
tion systems~, granted on February 7, 1984. As describ-
ed in the patent to Ulanet, his system includes visual
and audible signals responsive to operative conditions
of at least a coolant level, engine temperatures, high
and low oil pressures, and air intake pressures. If an
operative condition endures for a period of time deter-
mined by the passage of current through a circuit break-
er, engine shutdown is effected by tripping current to
the solenoid of an engine fuel valve.
The ability of an engine protection system to
respond to more than one sensed operating or environmen-
tal condition is a desirable feature. In practical
terms, any one of such conditions may represent a threat
to an engine or its associated equipment. To afford
protection against only one condition is limiting and
may be considered inadequate for many applications.
However, known systems that are designed to respond to
any one of a plurality of sensed operating conditions
generally fail to distinguish any one threatening
~Z35771~3
condition from the next, and generally fail to recognize
that the control and response of the system may prefer-
ably or advantageously depending upon the character of
particular threatening conditions. For example, in the
case of the system disclosed by Ulanet, there is essen-
tially a series connection of switches, the opening of
any one of which will initiate the same control regime
leading up to engine shutdown, viz. current through a
circuit breaker which, if not manually overridden and
allowed to endure for a predetermined period of time,
will ultimately trip the breaker and current to a fuel
valve as noted above. The timing of engine shutdown
control is essentially fixed.
SUMMARY OF TH~_INVE_TION
The present invention recognizes that the
response of a control system for engine protection to
different threatening conditions should not always be
the same. At the same time, the present invention
recognizes that the facility to respond differen~ly to
different conditions should not detract from the object
of an integrated system which may be made compact, which
is flexible in its application, and which is relatively
easy to instal and maintain.
To such ends, the present invention provides a
control system for protecting an internal combustion
engine, the system comprising input receiving means for
receiving a plurality of warning signals, each of which
warning signals represents the presence or absence of a
fault condition causing or which may cause damage to the
engine, and signal processing means operatively
:~2;~5778
connected to the input receiving means for conditionally
producing an engine shutdown command signal, The signal
processing means includes means for classifying any such
warning signal as one requiring generation of the engine
shutdown command in relatively fast respone to the
warning signal or as one requiring generation of the
engine shutdown command only in delayed response to the
warning signal.
For example, fast response may be dictated if
a warning signal represents a fire, the presence of
combustible gas or fuel, roll-over or excessive tilt.
Likewise, manual actuation of an operator's key or
shut-off switch may equated as a warning signal
dictating a fast response. On the other hand, delayed
response may be desirable in some situations - for
example, if the warning signal represents low oil
pressure or low coolant level, engine overheating, or
engine overspeed. In such situations, a delayed
response enables the opportunity for operator
intervention.
Preferably, a control system in accordance
with the present invention includes means for manually
overriding the generation of an engine shutdown command
during a period of delayed response to a warning signal.
Typically, the period of a delayed response may be of
the order of about 15 seconds thereby enabling a reason-
able opportunity for operator intervention ~which is in
contrast to a typical fast response that may be of the
order of 2 seconds or less). The fact that a delayed
~2;~S~78
response period is in progress may be indicated to an
operator by visible and audible warnings.
In a preferred embodiment of the present
invention, the input receiving means includes means for
producing a latched signal representing the occurence of
a fault condition if a received warning signal endures
for a preselected period of time. In situations of fast
or delayed response to the occurence of such a latched
signal, depending on the classification of the warning
signal, the signal processing means produces the engine
shutdown command. This feature is a debounce feature
designed to guard against the possibility of false warn-
ing signals. It requires the warning signal to endure
for a minimum time before the system will recognize the
signal as a true warning signal. Typically, this mini-
mum time may be of the order of 1/2 to 1 1/2 seconds.
Advantageously, fast and delayed response to
warning signals may be achieved by a timing means which
not only serves to generate an engine shutdown command
signal in fast or delayed response to a received (true)
warning signal, but also to sustain the command signal
for a predetermined period of time thereafter~ A sus-
tained shutdown command signal is considered desirable
in some applications - particularly those where complete
engine shutdown may not be achieved by a momentary com-
mand signal~ For example, in some applications, the
closure of a fuel valve ror a short period of time may
not reliably ensure complete shutdown. Fuel leakage
through the valve may cause the engine to continue to
run for a significant period of time. In such
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situations, it is considered that an engine shutdown
command signal should endure for a relatively lengthy
period of time, for example, of the order of 40
seconds.
The fast or delayed response of such timing
means to a received warning signal is preferably achiev-
ed by timing means which has selectable first and second
starting conditions, the first of which is operatively
selected in response to a received warning signal re-
quiring immediate engine shutdown, the second of which
is operatively selected in response to a received warn-
ing signal not requiring immediate engine shutdown.
Such selectable control may readily be achieved with the
use of a digital clock and counter (or shift register)
the latter of which is loaded or preset to commence
counting from a selected count, the selected count being
the starting condition determined by classification of
the warning signal.
A control system in accordance with the pre-
sent i~vention may include controlled switching means
for connecting and disconnecting the system with an
external source of electrical power. Advantageously,
the foregoing timing means is operatively interconnected
with such switching means so as to effect electrical
disconnsction of the system upon termination of an
engine shutdown command signal. Such a feature is con~
sidered desirable because continuing energization of the
system following engine shutdown may itself present a
hazard in some situations - for example, where an elec-
trical short may ignite fuel.
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Various features may be implemented in con-
junction with a control system in accordance with the
present invention. For example, in vehicular applica-
tions, the control system may include a tilt detector as
a built in part of the system. Also, in vehicular
applications, the system may include an input for
receiving a signal that will automatically cause an
engine shutdown command to be overridden if the vehicle
is in motion. Vehicle motion detectors are well known
(for example, in cruise control applications) and their
utilization to provide a control input to the present
invention may be desired especially in situations where
the consequence of engine shutdown during vehicle motion
could be more serious than any damage to the engine per
se that might otherwise occur.
The particular means for producing various
kinds of warning signals are not considered to be a part
of the present invention. Likewise, the particular
means and methods of utilizing the engine shutdown com-
mand signal to effect engine shutdown is not considered
to be a part of the present invention. The engine shut-
down command signal is itself an electrical signal, but
how it is used to cause engine shutdown will depend on
the application. For example, in the case of a diesel
engine, the signal may be utilized to control a fuel
shut-off, either by the fuel rack or governor of an
engine, or by placing an electro-mechanical switch in
the fuel supply line. Alternately, the signal may be
utilized to activate an air flow restrictor or gate
~23577~
valve often found mounted between the air filter and air
intake manifold of the engine.
BRIEF DESCRIPTION OF THE DRAWI~TGS
FIGU~E 1 is a system flow diagram for an engine protec-
tion system in accordance with the present
invention.
FIGURE 2 consisting of parts Al to A3, Bl to B3, Cl, C2
and Dl, is a circuit diagram showing input
receiving means and signal processing means in
accordance with the present invention.
DETAILED DESCRIPTION
-
The system flow diagram of Figure 1 is a
substantially self-contained description of an engine
protection system in accordance with the present inven-
tion, such diagram illustrating a system for receiving a
plurality of input warning signals and for producing in
controlled response thereto an engine shutdown command
signal. As will be apparent, the system illustrates
many of the features discussed above.
As can be seen in Figure 1, the input warning
signals are received by a contol block 101 of an input
sensing means generally designated lOOo Block 101
determines whether a fault condition exists. If a fault
is sensed, and if the fault has endured for a selected
period of time as determined by control block 102, then
the system flow passes to block 202 of signal processing
means generally designated 200. If no fault is sensed,
or if any fault sensed has endured for less than the
selected period of time, then the system flow passes to
block 201 of signal processing means 200.
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The selected period of time determined by
block 202 is relatively short - for example, 1.5
seconds. This provides the debounce feature discussed
above and guards against the possibility of false
warning signals.
When system flow passes to block 201, then
normal operations are maintained, including a continuing
determination of whether any fault condition exists.
This is indicated in Figure 1 by system flow from block
201 back to block 101.
As can be seen in Figure 1, when system flow
passes to block 202, it also passes to control block 212
to activate visible and/or audible annunciators.
Obviously, the purpose is to provide suitable warning to
an operator that a fault has occurred.
If control block 202 determines that a fault
is one requiring a fast response, then timing means 205
if preset by control block 203 to initiate engine shut-
down in fast response to the warning signal. As indi-
cated above, a typical fast response may be 2 seconds or
less. On the other hand, if control block 202 deter-
mines that a fault condition is one not requiring a fast
response, then timing means 205 is preset by control
block 204 to initiate engine shutdown in delayed res-
ponse to the warning signal. Here, and again as
indicated above, a typical delayed response may be of
the order of 15 seconds.
Control block 206 itself performs a timing
function and determines whether the time delay (fast or
delayed) preset in timing means 205 has elapsed. If it
12357~8
has, then system flow proceeds to block 209 which
generates an engine shutdown command as an output.
Control block 210 likewise performs a timing function
and determines whether an engine shutdown command has
endured for a period of time controlled by the timing
means. To better ensure complete engine shutdown, this
period of time is relatively lengthy, for example 40
seconds. As indicated by contol block 211, the engine
shutdown command is terminated after the controlled
period and, at the same time, the system is electrically
disconnected.
During the time delay preceding an engine
shutdown commandl control block 207 determines whether
an override to block an engine shutdown command has been
activated. If there is an overrida, then system flow
passes to block 208 which resets the system to normal
operations - passing flow back to block 201 and then to
block lO1. If the fault that initiated the overridden
shutdown command is still present as an input warning
signal, then the cycle will begin once again.
The circuit diagram of Figure 2 consists of 9
parts, namely parts Al to A3, Bl to B3, Cl, C2 and Dl.
In appreciating the composite diagram represented by
these parts, it may assist the reader to align the parts
in a gridwork formed by four horizontal rows Al-A3,
Bl-B3, Cl-C2 and Dl, and three vertical columns Al-Dl,
A2-C2 and A3-B3.
The circuit of Figure 2 consists of commer-
cially available circuit components and will be readily
understood by those skilled in the art. Standard
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~235778
nomenclature is used wherein cornponents labelled alpha-
numerically beginning with the letter "A" are integrated
circuit components for performing the function repre-
sented by the nomenclature, or the function described
below in more detail. In many cases, it will be noted
that there are repetitions of components bearing the
same alphanumeric nomenclature -- for example, four
occurences of gate A20. According to convention, this
simply indicates that the components are a part of the
same integrated circuit chip. However, so as to differ-
entiate such parts, differing one or two digit numerals
representing pin connections of the chip appear at the
input and output connections of the parts.
~here a circuit line bears a label such as
A18-6 or A26-5 this simply means that the line connects
to or frorn component A18, pin 6 or component A26, pin 5,
as the case rnay be.
Through optical isolating and debounce cir-
cuitry represented by components Al to A7, the circuit
of Figure 2 is designed to receive a plurality of input
warning signals corresponding to sensed TEMPERATURE,
HEAT, OVERSPEED, ENGINE OIL, FIRE, TILT, GAS, and KEY,
the KEY input being an operator key, switch or the
like. As well, the system includes provision for
receiving input signals corresponding to sensed MOTION,
OVERRIDE and START, the OVERRIDE and START inputs being
controlled externa]ly by an operator switch or the like.
These input paths may be seen in parts Al, Bl, Cl and Dl
of Figure 2. Typically, all such inputs may be sensed
from an engine operated vehicle.
~2357';~8
Devices and componentry for providing such
input signals are not shown because the various signals
indicated may be generated in various known ways. In
Figure 2, the particular input signals that appear are
basically intended to shown the variety of input signals
that may be utilized with an engine protection system in
accordance with the present invention. However, in
particular applications, it will be readily appreciated
that engine shutdown control may be achieved with only
some of the indicated signals or other signals represen-
tative of external parameters or functions that are not
indicated in Figure 2.
As may seen in parts A3 and B~ of Figure 2,
the circuit of Figure 2 provides a plurality of output
signals designated as MOTION, TEMPERATURE, HEAT,
OVERSPEED, ENGINE OIL, FIRE, TILT, GAS, HYDRAULIC OIL,
BUZZER, SHUTDOWN, ELEC. SOL., RIG SAVER and GOV. FUEL
SOLENOID, each of such outputs being taken through
transistor output driver stages.
When they occur, the outputs for TEMPERATURE,
HEAT, OVERSPEED, ENGINE OIL, FIRE, TILT, GAS, HYDRAULIC
OIL, BUZZER and SHUTDOWN will be intermittent signals
pulsed by clock signal CLKl. As such, they may be used
to drive a visual display and, in the case of the BUZZER
output, audible annunciators. The pulsating character
of these signals will indicate an abnormal status. The
output for MOTION may likewise be used to drive a visual
annunciator However, since motion is not necessarily
representative of abnormal status, the output is
constant (it is not pulsed by CLKl).
~235~7B
The outputs identified as ELEC. SOL., RIG
SAVER and GOV. FUEL SOL~NOID are solenoid drivers used
to drive external solenoids (not shown).
The output identified as LOGO is an uncontrol-
led line which may serve as a grounding path whenever
the system is energized - for example as a path in a
circuit to illuminate a fixed display or indicator that
the system is energized.
The structure and function of the circuitry
and circuit elements shown in Figure 2 will now be
described in more detail.
(1) Diodes D4 to D8, D50 (see parts Al, B1, C1, and D1
of Figure 2)
These are blocking diodes included to protect
optical isolators in the event that an excessive reverse
voltage is connected to an input terminal.
(2) Resistors R24, R25, R26, R27, R29, R30, R31, R33,
R34, R36, R70 (see parts Al, Bl, Cl and Dl of
Figure 2)
These are resistors utilized to limit input
current to a level that is safe and commensurate with
the requirements of the optical isolating circuitry
shown in Figure 2 that will carry input current.
(3) Resistors R28, R32, R35 (see parts Bl, Cl and D1 of
Figure 2)
These are current limiting resistors to be
utilized in series connection with resistors R297 R33
and R36, respectively, in the event that the system
voltage used to generate input current is relatively
high. ~~n o~her words, as shown in Figure 2, one of two
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~Z35 ~
input configurations may be selected for sensed inputs
corresponding to FIRE, TILT and START. The selected
configuration will depend upon whether the external
driving voltage is relatively low or relatively high.
(4) Optical Isolating and Bounce Eliminating Circuitry
Al to A6, A7; timing capacitors Cl, C2 (see parts
Al, Bl, Cl and Dl of Figure 2)
The purpose of this circuitry is to isolate
the circuit inputs from transient voltages and to
elil~inate false triggering due to contact bounce or
vibration. Timing capacitor C2 also provides clock
signal CLK~.
(5) Inverter A26 and Jumper Jl (see FIRE input in
Figure 2(Bl)).
This circuitry allows selection for normally
open or normally closed contacts at the sensed input
corresponding to FIRE. Typically, current will flow at
this input if terminal T8 is grounded ~y an external
contact closure (not shown).
(6) Flip Flops A8 to All (see parts Al, Bl and Cl of
Figure 2)
These flip flops provide latched output status
signals in response to corresponding sensed input sig-
nals from the optical isolating and debounce circuitry.
As will be apparent, in order to achieve a latched
warning signal from the output of one of the segments of
flip flops A8 to All a sensed input warning signal must
endure for a length of time sufficient to trigger the
~egment. When such latching occurs, the flip flop
~0
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~2:~5778
output is taken as a "true" warning that a fault condi-
tion exists.
(7) Gate A13 (see Figure 2(A2))
This gate provides an output active low upon
the occurence of a true warning signal.
(8) Gate combination A14 and A15 providing SH~TUOWN
signal as shown in Figure 2(B2)
This circuitry is designed to provide for
immediate engine shutdown if a sensed input signal cor-
responds to FIRE, TILT, GAS or KEY. The output at
A14-10 will be active high. Typically, with the possi-
ble exception of a sensed input signal corresponding to
KEY, any one of these signals will represent a serious
and immediate hazard. A KEY signal, being manually
controlled by an operator may or may not represent the
presence of some hazard, but it nevertheless indicates
an immediate desire for engine shutdown. In effect,
this circuitry is performing a classification function
by distinguishing warning signals requiring immediate
engine shutdown from those that do not.
(9) Gate A14 receiving inputs SOL and CLK2 as shown in
Figure 2(B2)
When enabled, this gate provides clock signal
CLK2 to control the clocking and loading of shift regis-
ter (counter) A22.
(10) Gates A29 as shown in Figure 2(A2)
The output at A29-11 provides an enabling sig-
nal to count loading (flip flops A16) and counting
(counter A22) circuits. Engine shutdown sequence will
3~
1~3S~78
be initiated only if gate A13 described above is
activated and vehicle is not in MOTION or TILTed.
(11) Flip Flops A16 as shown in Figure 2(B2)
The output at A16-8 is a command to load
counter A22 with the count determined by the output at
A14-10.
(12) Shift Register (Counter) A22 as shown in Figure
2(B2)
Counter A22 provides a clock signal at A22 - 15
on line L4 to pins 3 and 5 of A17 (flip flops shown in
Figure 2(C2). It provides time delays of about 15
seconds for delayed shutdown response and about 40 for
sustaining a shutdown command.
The particular counter A22 utilized in the
circuit of Figure 2 is an integrated circuit commercial-
ly available from Motorola (Motorola MC14161BCP).
(13) Gate A23 receiving KEY input as shown in Figure
2(A2)
The signal output at A23-4 acts to disable the
BUZZER output (F'igure 2(B3)) on a KEY input.
(14) Flip Flop A17 (section comprising pins 1 to 6)
As may be seen from Figures 2(C2) and 2(B3),
this section of A17, receiving an input from counter A22
on line L4, provides an output to the SHUTDO~N display
output through a flip flop section of A28 (viz. on line
A28-9). It also provides an output at A17-6 to energize
the FUE~, SOLENOID output shown in Figure 2(B3) and an
input to a second flip flop section of A17 described
below for the next step in an engine shutdown sequence.
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~23S778
The FUEL SOLENOID output may be utilized to operate a
variety of known fuel shut-off mechanisms.
(15) Flip Flop A17 (section comprising pins 8 to 13)
On the second pulse from counter A22, this
flip flop provides the signal SOL shown in Figure 2(C2)
which disables clock signal CLK2 at A14-11 (input to
counter A22). Also, this flip flop disables the clock
to flip flops A8 to A11. Further, this flip flop pro-
vides a clock input at A21-12 (for direction to an Elec-
trical Disconnect Solenoid via the ELEC. SOL. output).
As will be appreciated, the entire engine system may
have a source of DC power such as a battery. As a safe-
ty measure, the power source may be electrically discon-
nected at the end of a shutdown sequence utilizing the
ELEC. SOL. output to trip a high current breaker or
relay (not shown).
(16) Gate A21 (section comprising pins 11 to 13) and
Flip Flop A28 (section comprising pins 1 to 6) as
shown in Figure 2(C2)
When engaged, gate A21 at pin 11 provides an
input signal to flip flop section A28, pin 3. Jumpers
are to allow non-immediate shutdown inputs to allow
option of not disconnecting external Electrical Solenoid
and visual display (the latter of which are external to
the circuit of Figure 2 and are not shown).
(17) Gate A21 (section comprising pins 8 to 10) and Gate
A23 (section comprising pins 2, 9 and 10) as shown
in Figure 2(C2)
The output at A23-10 activates the RIG SAVER
outpu'c shown in Figure 2(B3) in response to an output at
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A17-5, but, unlike the FUEL SOLENOID output, also
depends on the status of the KEY input.
(18) Gates A27 and A14 as shown in Figure 2(C2)
These gates form a logic circuit to disable
CLK0 on line Ll to flip flops A8 to All if any input has
been activated or the START input has not been activat-
ed.
(17) MOTION input and output circuits as shown in
Figures 2(Al) and 2(A3)
A signal at A7-11 indicates that the vehicle
is in motion. This signal is provided as an input at
A29-2 (Figure 2(A2)) referred to above and is also
provided as an input at A29-8,9 (Figure 2(A3)) for
visual display.
(18) Output Drive Circuitry (parts A3 and B3 of Figure
2).
Upon the occurence of any one of the inputs
MOTION through KEY as appear in part Al, Bl and Cl of
Figure 2, there will be an output drive through a
corresponding output transistor Ql to Q8, or Q14, as the
case may be. As can be seen these outputs are taken
through current limiting resistors. As noted above
(with the exception of the MOTION output?, these outputs
are pulsed by a clock signal CLKl. Such signal is
generated by the clock circuit comprising inverter A25,
resistor R42 and capacitor C8 shown in Figure 2(B3).
Thus, both a clock signal and a true warning signal must
be present at the input of a gate segment Al9, A20 in
order to drive the corresponding output transistor.
(19) Voltage Regulator (see Figure 2(B3)
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~Z3S7'i~
The regulator shown provides a stable supply
voltage Vcc (e.g. 8 volts from the indicated 12 volt
source) for operation of integrated circuits which form
part of the overall circuit of Figure 2. Diode D3 pre-
vents rapid discharge at the output of the regulator
when system power is shut off and provides protection to
A12 flip flop segments referred to below.
(20) Clock CLK2 (see Figure 2(A2))
The circuitry generating clock signal CLK2
controls shift register (counter A22) and the sequence
of shutdown.
(21) Flip Flop A12 (section comprising pins 1 to 6),
capacitor Cx, R37, R39, gates A27, all as shown in
Figure 2(Dl)
Generally, this section generates a pulse of
15 seconds duration when an OVERRIDE signal ceases (e.g.
when a manual override button providing an external
contact closure (not shown) is released). However, gate
circuitry A27 will OVERRIDE on an immediate engine
shutdown~
(22) Flip Flop A12 (section comprising pins 11 to 15),
capacitor Cy, R38 and R4n as shown in Figure 2(Dl)
I'his section generates a pulse of 15 seconds
duration when a START signal ceases (e.g. when a manual
star~ switch providing an external contact closure (not
shown) is released). Note that the output at A7-4 not
only provides an input at A12-11 through A25-11, but
also provides a reset signal (SOLSET) to A17-10.
(23) Gate A15 (pins 10 to 13), R47, C5, A15 (pins
12-13), R44 and LED Dl
- - 19 -
lZ35778
This section provides a visual indicator and a
reset signal when QVERRIDE is engaged to reset counter
A22, or on START for time during engine cranking plus 15
seconds to disarm all inputs to prevent any shutdowns.
(24) Flip Flop A18 (section comprising pins 8 to 13) as
shown in Figure 2(B2)
This section will allow a KEY shutdown to
activate the ELEC. SOL. output.
(25) Gate A25 (pins 1,2), R43 and C9 (see Eigure 2(B2))
Used to provide power to system via double
contact pushbutton (not shown).
(26) Gates A23 (pins 11 to 13), A15 (pins 3 to 6) and
A25 (pins 3,4) as shown in Figure 2(B2)
This circuitry provides a reset on line L2
when power is turned on or on reset from A18-5. A reset
from A15-6 is provided when power is turned on, or on
reset from A18-5, or signal from A16-9 that load
sequence is completed. A reset is provided at ~25-4 on
line L3 only when power is turned on.
It will be clear to those skilled in the art
that a wide variety of circuit structures may be devised
to implement the control functions performed by the
circuit of Figure 2, and to achieve the system functions
shown in the flow diagram of Figure 1. The particular
circuitry or other means that may be utilized to provide
an engine protéction system in accordance with the
present may vary considerably but remain within the
scope of the following claims.
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