U.S. patent number 3,810,451 [Application Number 05/209,281] was granted by the patent office on 1974-05-14 for ignition spark vacuum advance system.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Douglas I. Fales.
United States Patent |
3,810,451 |
Fales |
May 14, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
IGNITION SPARK VACUUM ADVANCE SYSTEM
Abstract
An ignition spark vaccum advance system for use with motor
vehicle internal combustion engines. The collector-emitter
electrodes of a switching transistor are connected in series in the
energizing circuit of the operating coil of a two-way valve which
normally establishes a vacuum connection between the carburetor
vacuum spark advance port and the associated spark advance vacuum
unit vacuum port and, upon the energization of the operating coil,
vents the spark advance vacuum unit vacuum port to atmosphere. A
trigger circuit responsive to a reference potential signal of a
magnitude proportional to vehicle or engine speed produces a
control signal during vehicle acceleration until the vehicle has
accelerated to a speed of a selected magnitude and during vehicle
deceleration after the vehicle has decelerated to a speed less than
the selected magnitude which triggers the switching transistor
conductive to complete the energizing circuit for the valve
operating coil. The current carrying elements of a temperature
sensitive switch which are operated to the circuit closed condition
with engine temperatures less and greater than a selected engine
temperature range are connected across the base-emitter electrodes
of the switching transistor to provide for a normal ignition spark
vacuum advance at any engine speed with a cold engine or an engine
approaching over-heating.
Inventors: |
Fales; Douglas I. (Flint,
MI) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
22778136 |
Appl.
No.: |
05/209,281 |
Filed: |
December 17, 1971 |
Current U.S.
Class: |
123/406.55 |
Current CPC
Class: |
F02P
5/103 (20130101); F02P 5/1556 (20130101); F02P
5/14 (20130101); Y02T 10/40 (20130101); Y02T
10/46 (20130101) |
Current International
Class: |
F02P
5/14 (20060101); F02P 5/04 (20060101); F02P
5/155 (20060101); F02P 5/10 (20060101); F02P
5/145 (20060101); F02p 005/08 () |
Field of
Search: |
;123/117R,117A,102 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
The Design Development and Application of Exhaust Emissions Control
Devices by Forge-Dedman, J. A. Howard, pp. 264, 267, 268..
|
Primary Examiner: Goodridge; Laurence M.
Attorney, Agent or Firm: Stahr; Richard G.
Claims
What is claimed is:
1. An ignition spark vacuum advance system for use with motor
vehicle internal combustion engines comprising in combination with
a carburetor having a spark advance port, an ignition distributor
having an ignition spark advance mechanism operated by a spark
advance vacuum unit having a vacuum port and a source of direct
current potential,
a vacuum line extending between said carburetor spark advance port
and said spark advance vacuum unit vacuum port,
a two-way valve having an operating coil included in said vacuum
line which is normally in a first condition to establish a vacuum
connection between said carburetor spark advance port and said
spark advance vacuum unit vacuum port and operable, upon the
energization of said operating coil, to a second condition to vent
said vacuum advance unit vacuum port to atmosphere,
means for producing a direct current reference potential signal of
a magnitude proportional to vehicle speed,
means responsive to said reference potential signal for producing a
control signal during vehicle acceleration until said vehicle has
accelerated to a speed of a selected magnitude and during vehicle
deceleration after said vehicle has decelerated to a speed less
than the selected magnitude,
an electrical switching device having normally open current
carrying elements operable to an electrical circuit closed
condition in response to an electrical signal,
means for connecting said current carrying elements of said
electrical switching device and said operating coil of said two-way
valve in series across said source of direct current potential,
means responsive to said control signal for operating said
electrical switching device to the electrical circuit closed
condition, and
means responsive to engine temperatures less than and greater than
a selected engine temperature range for diverting said control
signal from said electrical switching device.
2. An ignition spark vacuum advance system for use with motor
vehicle internal combustion engines comprising in combination with
a carburetor having a spark advance port, an ignition distributor
having an ignition spark advance mechanism operated by a spark
advance vacuum unit having a vacuum port and a source of direct
current potential,
a vacuum line extending between said carburetor spark advance port
and said spark advance vacuum unit vacuum port,
a two-way valve having an operating coil included in said vacuum
line which is normally in a first condition to establish a vacuum
connection between said carburetor spark advance port and said
spark advance vacuum unit vacuum port and operable, upon the
energization of said operating coil, to a second condition to vent
said vacuum advance unit vacuum port to atmosphere,
means for producing a direct current reference potential signal of
a magnitude proportional to vehicle speed,
means responsive to said reference potential signal for producing a
control signal during vehicle acceleration until said vehicle has
accelerated to a speed of a selected magnitude and during vehicle
deceleration after said vehicle has decelerated to a speed less
than the selected magnitude,
a normally not conducting transistor having a base electrode and
two currents carrying electrodes,
means for connecting said current carrying electrodes of said
transistor and said operating coil of said two-way valve in series
across said source of direct current potential,
means responsive to said control signal for supplying base drive
current to said base electrode of said transistor, and
means responsive to engine temperatures less than and greater than
a selected engine atmosphere range for diverting said base drive
current from said transistor.
3. An ignition spark vacuum advance system for use with motor
vehicle internal combustion engines comprising in combination with
a carburetor having a spark advance port, an ignition distributor
having an ignition spark advance mechanism operated by a spark
advance vacuum unit having a vacuum port and a source of direct
current potential,
a vacuum line extending between said carburetor spark advance port
and said spark advance vacuum unit vacuum port,
a two-way valve having an operating coil included in said vacuum
line which is normally in a first condition to establish a vacuum
connection between said carburetor spark advance port and said
spark advance vacuum unit vacuum port and operable, upon the
energization of said operating coil, to a second condition to vent
said vacuum advance unit vacuum port to atmosphere,
means for producing a direct current reference potential signal of
a magnitude proportional to vehicle speed,
means responsive to said reference potential signal for producing a
control signal during vehicle acceleration until said vehicle has
accelerated to a speed of a selected magnitude and during vehicle
deceleration after said vehicle has decelerated to a speed less
than the selected magnitude,
a normally not conducting transistor having a base electrode and
two currents carrying electrodes,
means for connecting said current carrying electrodes of said
transistor and said operating coil of said two-way valve in series
across said source of direct current potential,
means responsive to said control signal for supplying base drive
current to said base electrode of said transistor,
a temperature sensitive switch having current carrying elements
operable to an electrical circuit closed condition in response to
engine temperatures less than and greater than a selected engine
temperature range, and
means for connecting said current carrying elements of said
temperature sensitive switch across said base electrode of said
transistor and a point of reference potential for diverting said
base drive current from said base electrode of said transistor.
4. An ignition spark vacuum advance system for use with motor
vehicle internal combustion engines comprising in combination with
a carburetor having a spark advance port, an ignition distributor
having an ignition spark advance mechanism operated by a spark
advance vacuum unit having a vacuum port and a source of direct
current potential,
a vacuum line extending between said carburetor spark advance port
and said spark advance vacuum unit vacuum port,
a two-way valve having an operating coil included in said vacuum
line which is normally in a first condition to establish a vacuum
connection between said carburetor spark advance port and said
spark advance vacuum unit vacuum port and operable, upon the
energization of said operating coil, to a second condition to vent
said vacuum advance unit vacuum port to atmosphere,
means for producing a direct current reference potential signal of
a magnitude proportional to vehicle speed,
a trigger circuit responsive to said reference potential signal for
producing a control signal during vehicle acceleration until said
vehicle has accelerated to a speed of a selected magnitude and
during vehicle deceleration after said vehicle has decelerated to a
speed less than the selected magnitude,
a normally not conducting switching transistor having a base
electrode and two currents carrying electrodes,
means for connecting said current carrying electrodes of said
transistor and said operating coil of said two-way valve in series
across said source of direct current potential,
a driver transistor having two current carrying electrodes
connected across a selected polarity terminal of said source of
direct current potential and said base electrode of said switching
transistor responsive to said control signal for completing a
circuit through which base drive current is supplied to said base
electrode of said switching transistor, and
means responsive to engine temperatures less than and greater than
a selected engine temperature range for diverting said base drive
current from said switching transistor.
5. An ignition spark vacuum advance system for use with motor
vehicle internal combustion engines comprising in combination with
a carburetor having a spark advance port, an ignition distributor
having an ignition spark advance mechanism operated by a spark
advance vacuum unit having a vacuum port and a source of direct
current potential,
a vacuum line extending between said carburetor spark advance port
and said spark advance vacuum unit vacuum port,
a two-way valve having an operating coil included in said vacuum
line which is normally in a first condition to establish a vacuum
connection between said carburetor advance port and said spark
advance vacuum unit vacuum port and operable, upon the energization
of said operating coil, to a second condition to vent said vacuum
advance unit vacuum port to atmosphere,
means for producing a direct current reference potential signal of
a magnitude proportional to vehicle speed,
a trigger circuit responsive to said reference potential signal for
producing a control signal during vehicle acceleration until said
vehicle has accelerated to a speed of a selected magnitude and
during vehicle deceleration after said vehicle has decelerated to a
speed less than the selected magnitude,
a normally not conducting switching transistor having base, emitter
and collector electrodes,
means for connecting said collector-emitter electrodes of said
switching transistor and said operating coil of said two-way valve
in series across said source of direct current potential, a driver
transistor having base, collector and emitter electrodes,
means for applying said control signal to said base electrode of
said driver transistor,
means for connecting said emitter-collector electrodes of said
driver transistor and said base-emitter of said switching
transistor across said source of direct current potential,
a temperature sensitive switch having current carrying elements
operable to an electrical current closed condition in response to
engine temperature less than and greater than a selected engine
temperature range, and
means for connecting said current carrying elements of said
temperature sensitive switch across said base-emitter electrodes of
said switching transistor.
Description
This invention is directed to an ignition spark vacuum advance
system and, more specifically, to an ignition spark vacuum advance
system for use with motor vehicle internal combustion engines which
provides ignition spark retard at vehicle or engine speeds less
than a preselected magnitude with normal engine temperatures and
normal ignition spark vacuum advance at any vehicle or engine speed
with a cold or over-heated engine.
In an effort to reduce the undesirable emissions of the exhaust of
internal combustion engines employed to drive motor vehicles,
various ignition spark control systems have been developed which
prevent ignition spark vacuum advance during low vehicle speeds.
One undesirable consequence of systems of this type is the
difficulty of a cold engine to start properly in cold weather and
drive the vehicle without stalling. Furthermore, since internal
combustion engines heat more rapidly with a retarded spark, there
is a tendency for the engine to overheat at low vehicle speeds,
such as encountered in slow traffic or standing, with the spark
retarded.
It is, therefore, an object of this invention to provide an
improved ignition spark vacuum advance system for use with motor
vehicle internal combustion engines.
It is another object of this invention to provide an improved
ignition spark vacuum advance system for use with motor vehicle
internal combustion engines which, at low vehicle or engine speeds,
disenables the ignition spark vacuum advance mechanism while the
engine is at normal operating temperature and enables the ignition
spark vacuum advance mechanism at any vehicle or engine speed while
the engine is operating at temperatures less than and greater than
a selected engine temperature range.
In accordance with this invention, an ignition spark vacuum advance
system for use with motor vehicle internal combustion engines which
retards the ignition spark at low vehicle or engine speeds while
the engine is operating within a selected engine temperature range
and provides normal ignition spark vacuum advance at any vehicle or
engine speed while the engine operating temperature is less than
and greater than a selected engine temperature range is provided
wherein a switching transistor having the collector-emitter
electrodes connected in series in the energizing circuit of the
operating coil of a two-way valve, the energization of which
operates the valve to a condition which vents the vacuum port of an
associated spark advance mechanism vacuum unit to atmosphere, is
triggered conductive through the collector-emitter electrodes in
response to a control signal produced during vehicle acceleration
until the vehicle has accelerated to a speed of a selected
magnitude and during vehicle deceleration after the vehicle has
decelerated to a speed less than the selected magnitude and the
current carrying elements of a temperature sensitive switch,
operated to the electrical circuit closed condition in response to
engine temperatures less than and greater than a selected engine
temperature range, are connected across the base-emitter electrodes
of the switching transistor.
For a better understanding of the present invention, together with
additional objects, advantages and features thereof, reference is
made to the following description and accompanying single FIGURE
drawing which sets forth the ignition spark vacuum advance system
of this invention in schematic form.
The ignition spark vacuum advance system for use with motor vehicle
internal combustion engines of this invention operates in
combination with a conventional automotive type carburetor 10
having a vacuum spark advance port 12, an ignition distributor 14,
shown in top plan view in the FIGURE, and a source of direct
current potential, which may be a conventional automotive type
battery 8.
Carburetor 10 may be of conventional design having a vacuum spark
advance port 12 which opens into the carburetor mixing conduit 16,
through which the air-fuel mixture is conducted to the intake
manifold 15, just above the throttle plate 17. At idle or
conditions of very low engine speeds, throttle plate 17 is closed
or nearly closed, consequently, carburetor vacuum spark advance
port 12 is exposed to substantially atmospheric pressure as shown
in the FIGURE. As the throttle plate 17 is revolved to open in a
counterclockwise direction, as viewing the FIGURE, carburetor
vacuum spark advance port 12 becomes exposed to the engine intake
manifold vacuum.
Ignition distributor 14 may be of conventional design having an
ignition spark advance mechanism of conventional design operated by
a spark advance vacuum unit 18 having a vacuum port 19. As ignition
spark vacuum advance mechanisms of this type are well known in the
automotive art, and per se, form no part of this invention, it has
not been illustrated in detail in the FIGURE. The operation will be
explained in greater detail later in this specification.
Extending between the carburetor vacuum spark advance port 12 and
the spark advance vacuum unit vacuum port 19 is a vacuum line which
includes vacuum line segments 20 and 21 and a two-way valve 22,
having an operating member or rod 23, which is operated to a first
position by compression spring 24 to establish a vacuum connection
between the carburetor vacuum spark advance port 12 and spark
advance vacuum unit vacuum port 19 and is operable to a second
position upon the energization of operating coil 25 to vent the
spark advance vacuum unit vacuum port 19 to atmosphere. Two-way
valve 22 is illustrated in the FIGURE as having a center chamber 26
and two outside chambers 27 and 28 separated by respective walls 29
and 30. Each of chambers 26, 27, and 28 communicates externally of
valve 22 through respective ports 31, 32, and 33. Internally of
valve 22, center chamber 26 communicates with outside chamber 28
through an inside port 34 having an angularly disposed valve seat
35 and with the other outside chamber 27 through an inside port 36
having an angularly disposed valve seat 37. Port 31 of two-way
valve 22 is interconnected with the spark advance vacuum unit
vacuum port 19 through vacuum line segment 21, port 32 is
interconnected with the carburetor vacuum spark advance port 12
through vacuum line segment 20 and port 33 is vented to atmosphere.
Secured to the end of operating member 23 within valve 22 is a
piston 38 having two angularly disposed faces 39 and 40 which are
arranged to engage respective angularly disposed valve seats 35 and
37 in a tight complementary fit. Valve 22 is operated to the first
condition by compression spring 24 and is operated to the second
condition by energizing operating coil 25 which moves rod 23
linearly in an upward direction as viewing the FIGURE. In the first
condition of valve 22, face 39 of piston 38 is in a tight
complementary fit with valve seat 35 to provide an open passage
therethrough between only ports 31 and 32 and in the second
condition, face 40 of piston 38 is in a tight complementary fit
with valve seat 37 to provide an open passage therethrough between
only ports 31 and 33. It is to be specifically understood that
two-way valve 22 of the FIGURE is only one example of many two-way
valves which may be employed for this application.
With conventional ignition spark vacuum advance mechanisms, the
carburetor vacuum spark advance port is directly interconnected
through a vacuum line with the spark advance vacuum unit vacuum
port. The spark advance vacuum unit 18 may be one of the many
vacuum units well known in the automotive art.
Mounted within the distributor 14 is a movable breaker plate, upon
which the ignition breaker contact points are mounted, which is
rotatable in a plane normal to the axis of the distributor drive
shaft to advance and retard the engine ignition spark. This movable
breaker plate is revolved by an operating arm, such as that
referenced by the numeral 41 in the FIGURE, which is attached to
and moved by a diaphragm within the spark advance vacuum unit 18
through push rod 42 in a manner well known in the automotive
art.
At idle or conditions of low engine speed with the carburetor
throttle plate 17 closed or nearly closed, the carburetor vacuum
spark advance port 12 is exposed to atmospheric pressure,
consequently, the diaphragm within the spark advance vacuum unit 18
is exposed to atmosphere on both sides. Under these conditions, the
diaphragm and connected operating rod 42 are forced by a spring,
also within the spark advance vacuum unit 18, in a direction which
will rotate the movable breaker plate within the distributor 14 in
the direction which will retard the ignition spark. With the
carburetor throttle plate 17 open during acceleration or cruising
speeds, the carburetor vacuum spark advance port 12 is exposed to
engine intake manifold vacuum, consequently, the diaphragm within
the spark advance vacuum unit 18 is exposed to manifold vacuum on
the side of the vacuum port 19. Under these conditions, the
diaphragm within the spark advance vacuum unit 18 and connected
operating rod 42 are forced in the opposite direction by the
greater pressure on the side of the diaphragm vented to atmosphere
to rotate the movable breaker plate in the direction which will
advance the ignition spark. From this description, it is apparent
that with two-way valve in the first condition of operation with
face 39 of piston 38 in tight complementary fit with valve seat 35,
the ignition spark vacuum advance mechanism illustrated in the
FIGURE will operate in a normal manner.
Also, provided is circuitry for producing a direct current
reference potential signal of a magnitude proportional to engine or
vehicle speed, circuitry responsive to the reference potential
signal for producing a control signal during vehicle acceleration
until the vehicle has accelerated to a speed of a selected
magnitude and during vehicle deceleration after the vehicle has
decelerated to a speed less than the selected magnitude, an
electrical switching device having normally open current carrying
elements, which may be a type NPN transistor 50 having a base
electrode 51, a collector electrode 52, and an emitter electrode
53, operable to an electrical circuit closed condition in response
to an electrical signal, circuitry responsive to the control signal
for operating the electrical switching device to the electrical
circuit closed condition and a device responsive to engine
temperatures less than and greater than a selected engine
temperature range for diverting the control signal from the
electrical switching device.
In the FIGURE, the output potential of battery 8 is shown to be
regulated by series resistor 43 and Zener diode 44. It is to be
specifically understood that this potential regulating arrangement
is not absolutely necessary for the practice of this invention.
One method, and without intention or inference of a limitation
thereto, for producing a direct current reference signal of a
magnitude proportional to vehicle or engine speed may be a type NPN
transistor 60 operating a Class A amplifier having the collector
electrode 62 and emitter electrode 63 thereof connected across the
positive and negative polarity terminals, respectively, of battery
8 through collector resistor 64 and positive polarity potential
lead 45 and point of reference or ground potential 5, respectively;
the parallel combination of capacitor 65 and resistor 66 connected
across the collector electrode 62 and the base electrode 61 and the
parallel combination of capacitor 67 and diode 68 in series and the
normally open contacts 76 and 77 of a magnetically operated reed
switch 75 connected across battery 8 through current limiting
resistor 69. Member 55 may be any member which may be conveniently
rotated at a speed equal to or proportional to engine speed which
is arranged to carry a plurality of permanent magnets, four of
which are illustrated in the FIGURE and referenced by the numerals
56, 57, 58, and 59. For example, member 55 may be a drum mounted
upon the engine crankshaft, it may be a member mounted upon the
engine flywheel or a member mounted upon any other vehicle part
which is rotated at a speed equal to or proportional to vehicle or
engine speed. It is only necessary that the permanent magnets
rotated thereby are in operative relationship with the normally
open contacts 76 and 77 of reed switch 75 to operate these contacts
to the electrical circuit closed condition at a frequency
proportional to vehicle speed by passing in close proximity thereto
in a manner well known in the art. While the contacts 76 and 77 of
reed switch 75 are open during any of the spaces between the
permanent magnets carried by member 55, capacitor 67 charges
through resistor 69 and diode 68. Upon the passing of one of the
magnets 56 through 59 in close proximity to reed switch 75, movable
contact 76 is magnetically operated to the electrical circuit
closed condition to stationary contact 77 to establish a discharge
circuit for capacitor 67.
Discharging capacitor 67 reduces the positive polarity potential
upon the base electrode 61 of type NPN transistor 60 thereby
decreasing the collector-emitter conduction therethrough as a Class
A amplifier. Capacitor 65 charges through the relatively low value
resistance 64 and discharges through high resistance 66 or much
more rapidly through type NPN transistor 60, depending upon the
degree of its conductivity. Consequently, the more frequently the
normally open contacts 76 and 77 of reed switch 75 are operated to
the electrical circuit closed condition by the magnets carried upon
rotating member 55 with increases of engine and vehicle speed, the
lower the degree of conduction through type NPN transistor 60. As
capacitor 65 discharges more slowly with a decrease of conduction
through transistor 60, the potential appearing across junction 78
and point of references or ground potential 5 increases in
magnitude. Consequently, this reference potential is of a magnitude
proportional to vehicle or engine speed. This reference potential,
across junction 78 and point of reference or ground potential 5, is
of a positive polarity upon junction 78 with respect to point of
reference or ground potential 5.
The circuitry responsive to the reference potential appearing
across junction 78 and point of reference or ground potential 5 for
producing a control signal during vehicle acceleration until the
vehicle has accelerated to a speed of a selected magnitude and
during vehicle deceleration after the vehicle has decelerated to a
speed less than the selected magnitude may be a trigger type
circuit comprised of type NPN transistors 70 and 80 and the
associated circuitry. The respective collector electrodes 72 and 82
of type NPN transistors 70 and 80 are connected to the positive
polarity terminal of battery 8 through respective collector
resistors 74 and 84 and the emitter electrodes 73 and 83 of
respective transistors 70 and 80 are connected to the negative
polarity terminal of battery 8 through a common emitter resistor 85
and point of reference or ground potential 5. Consequently, the
collector-emitter electrodes of both type NPN transistors 70 and 80
are connected across battery 8 in the proper polarity relationship
for forward collector-emitter conduction through type NPN
transistors. The base electrode 71 of transistor 70 is connected to
junction 78 through a current limiting resistor 79 and the base
electrode 81 of transistor 80 is connected to the collector
electrode 72 of transistor 70 through the parallel combination of
resistor 86 and capacitor 87. A capacitor 87 is included in this
coupling circuit for the purpose of absorbing any transient
voltages and for filtering any input ripple, thereby providing
consistent operation of the trigger circuit.
The circuitry responsive to the control signal for operating the
electrical switching device to the electrical circuit closed
condition may be a type PNP driver transistor 90 having the emitter
electrode 93 connected to the positive polarity terminal of battery
8 through positive polarity potential lead 45 and the collector
electrode 92 connected to the negative polarity terminal of battery
8 through current limiting resistor 88, the base-emitter electrodes
of switching transistor 50 and point of reference or ground
potential 5. Consequently, the emitter-collector electrodes of type
PNP driver transistor 90 are connected across battery 8 in the
proper polarity relationship for forward emitter-collector
conduction through a type PNP transistor. The base electrode 91 of
type PNP driver transistor 90 is connected to the collector
electrode 82 of transistor 80 through current limiting resistor
89.
The device responsive to engine temperatures less than and greater
than a selected engine temperature range, for example 140.degree.
to 160.degree. F., for diverting the control signal from the
electrical switching device may be a temperature sensitive switch
95 having a movable contact 96 and two stationary contacts 97 and
98 connected across the base-emitter electrodes of switching
transistor 50. Switch 95 may be any one of the many temperature
sensitive switches having a movable contact which is operated to an
electrical circuit closed condition to an associated stationary
contact with engine temperatures below a selected minimum and to an
electrical circuit closed condition to another associated
stationary contact with engine temperatures greater than a selected
maximum.
The current carrying elements, the collector-emitter electrodes of
type NPN switching transistor 50, of the electrical switching
device and the operating coil 25 of two-way valve 22 are connected
in series across the source of direct current potential, battery 8,
through a circuit which may be traced from the positive polarity
terminal of battery 8, through lead 46, operating coil 25 of
two-way valve 22, lead 47, the collector-emitter electrodes of type
NPN switching transistor 50 and point of reference or ground
potential 5 to the negative polarity terminal of battery 8.
Assuming that the associated internal combustion engine, not shown,
is operating at idle or low engine speed within the selected engine
temperature range, transistor 60 is operating as a Class A
amplifier and the contacts 76 and 77 of reed switch 75 are being
slowly operated by the magnets upon rotating member 55 and
capacitor 65 is charged through resistor 64, resistor 48, diode 49
and diode 68. With these conditions, the direct current reference
potential appearing across junction 78 and point of reference or
ground potential 5 is of an insufficient magnitude to provide
base-emitter drive current for transistor 70 of the trigger
circuit, consequently, transistor 70 is not conducting. With
transistor 70 not conducting, base drive current is supplied to the
base-emitter electrodes of type NPN transistor 80 of the trigger
circuit through resistors 74 and 86, through which the base
electrode 81 is connected to the positive polarity terminal of
battery 8, and through common emitter resistor 85, through which
the emitter electrode 83 is connected to the negative polarity
terminal of battery 8, consequently, transistor 80 is conducting
through the collector-emitter electrodes. Conducting transistor 80
establishes a circuit through which emitter-base drive current is
supplied to type PNP driver transistor 90 from positive polarity
potential line 45, through the emitter-base electrodes of type PNP
transistor 90, resistor 89, the collector-emitter electrodes of
transistor 80, common emitter resistor 85 and point of reference or
ground potential 5 to the negative polarity terminal of battery 8.
The flow of current through conducting transistor 80 also produces
a potential drop across common emitter resistor 85 which is applied
to the emitter electrode 73 of transistor 70, thereby establishing
the base electrode 71 and emitter electrode 73 at substantially the
same potential, a condition which maintains transistor 70 not
conductive. With emitter-base drive current supplied to type PNP
driver transistor 90, this device conducts through the
emitter-collector electrodes thereof to supply base-emitter drive
current to type NPN switching transistor 50 from positive polarity
potential line 45, through the emitter-collector electrodes of
driver transistor 90, base resistor 88, the base-emitter electrodes
of transistor 50 and point of reference or ground potential 5 to
the negative polarity terminal of battery 8. Consequently,
switching transistor 50 conducts through the collector-emitter
electrodes thereof to complete an energizing circuit for operating
coil 25 of two-way valve 22 through a circuit previously described.
Upon the energization of operating coil 25, two-way valve 22 is
operated to the second condition in which the vacuum port 19 of
spark advance vacuum unit 18 is vented to atmosphere through port
31 of valve 22, center chamber 26, internal port 34, outside
chamber 28 and port 33. With vacuum port 19 of spark advance vacuum
unit 18 vented to atmosphere, the ignition spark vacuum advance
mechanism is disabled and the ignition spark is retarded at these
low engine and, consequently, vehicle speeds.
As the speed of the engine is increased to accelerate the vehicle,
the magnets carried by rotating member 55 operate the contacts 76
and 77 of reed switch 75 more rapidly to the electrical circuit
closed condition to reduce the degree of conduction through
transistor 60 for the reason previously set forth. A decreased
degree of conduction through transistor 60 results in the retention
of a charge of increased magnitude upon capacitor 65 as it is not
as rapidly discharged through conducting transistor 60.
Consequently, as the engine continues to accelerate the vehicle,
the reference potential appearing across junction 78 and point of
reference or ground potential 5 continues to increase in magnitude
with increase of vehicle speed until the vehicle has been
accelerated to a speed of selected magnitude, for example, 30
m.p.h., at which the magnitude of the reference potential appearing
across junction 78 and point of reference or ground potential 5 is
of a sufficient magnitude to produce base-emitter drive current
through transistor 70 of the trigger circuit. With transistor 70
conducting through the collector-emitter electrodes, base drive
current is drained from the base electrode of transistor 80 to
extinguish this device. With transistor 80 extinguished, the
circuit through which emitter-base drive current is supplied to
type PNP driver transistor 90 is interrupted, consequently, driver
transistor 90 extinguishes. With driver transistor 90 extinguished,
the circuit through which base drive current is supplied to type
NPN switching transistor 50 is interrupted, consequently, switching
transistor 50 extinguishes to interrupt the energizing circuit of
operating coil 25 of two-way valve 22. Upon the deenergization of
operating coil 25, compression spring 24 operates piston 38 of
two-way valve 22 into a tight complementary fit with valve seat 35
to place valve 22 in the first condition. With two-way valve 22 in
the first condition, a vacuum connection is established between the
carburetor spark advance port 12 and the spark advance vacuum unit
18 vacuum port 19 through vacuum line segment 20, port 32 of valve
22, outside chamber 27, internal port 36, center chamber 26, port
31 and vacuum line segment 21. With the establishment of this
vacuum connection, the internal combustion engine ignition spark
vacuum advance mechanism operates in a normal manner to provide
ignition spark advance in accordance with engine vacuum.
While the vehicle and engine is being operated at a speed greater
than the selected magnitude, transistor 70 of the trigger circuit
is maintained conductive. Conducting transistor 70 supplies less
current to common emitter resistor 85, a condition which results in
a lower potential drop thereacross. With a lower potential drop
across common emitter resistor 85, the emitter potential of
transistor 70 is reduced, therefor, a substantial drop in base
voltage upon transistor 70 will be required before transistor 70 is
extinguished. During deceleration, the contacts 76 and 77 are
operated at a proportionally lower rate, consequently, the degree
of conduction through transistor 60 begins to increase
proportionately resulting in a proportionate decrease of the
magnitude of the reference potential appearing across junction 78
and point of reference or ground potential 5. However, since the
emitter potential of transistor 70 is of a lower value while
transistor 70 is conducting, to extinguish transistor 70, the
magnitude of the reference potential applied across the
base-emitter electrodes thereof must reduce below the magnitude of
the reference potential corresponding to the speed of a selected
magnitude. Consequently, upon deceleration, transistor 70 is not
extinguished until the magnitude of the reference potential has
reduced to a value lower than that corresponding to a speed of a
selected magnitude, for example, 20 m.p.h. With this arrangement, a
hysteresis is introduced into the system to provide increased
stability and smoothness of vehicle operation. As the engine and
vehicle continue to decelerate until a speed is reached at which
the reference potential is no longer of a sufficient magnitude to
maintain transistor 70 conductive through the collector-emitter
electrodes, the transistor 70 extinguishes and transistor 80 again
conducts through the collector-emitter electrodes. With transistor
80 conducting through the collector-emitter electrodes, the
emitter-base drive circuit for type PNP driver transistor 90,
previously described, is again established to trigger drive
transistor 90 conductive through the emitter-collector electrodes
to supply base-emitter drive current to switching transistor 50.
Upon the conduction of switching transistor 50 through the
collector-emitter electrodes, the energizing circuit for operating
coil 25 of two-way valve 22 is again established to operate two-way
valve 22 to the second condition which vents the vacuum port 19 a
spark advance vacuum unit 18 to atmosphere. With vacuum 19 vented
to atmosphere, the ignition spark remains retarded at these low
engine speeds.
Should the vehicle or engine be operating at any speed at a
temperature less than the selected engine temperature range,
movable contact 96 of temperature sensitive switch 95 is operated
to the circuit closed condition to one of stationary contacts 97 or
98. With movable contact 96 electrical contact with one of the
movable contacts 97 or 98, base drive current for switching
transistor 50 is diverted therethrough, consequently, switching
transistor 50 remains not conductive to interrupt the energizing
circuit for operating coil 25 of two-way valve 22. With operating
coil 25 de-energized, compression spring 24 operates piston 38 to
the first condition to establish a vacuum connection, previously
described, between the carburetor spark advance port 12 and the
vacuum port 19 of spark advance vacuum unit 18, consequently, the
ignition spark vacuum advance mechanism operates in a normal manner
to advance the ignition spark in accordance with engine vacuum.
Should the vehicle or engine be operating at any speed at a
temperature greater than the selected engine temperature range,
movable contact 96 of temperature sensitive switch 95 is operated
to the electrical circuit closed condition to the other one of
stationary contacts 97 or 98 to divert base drive current from
switching transistor 50. Consequently, at any engine speed while
the engine is operating at a temperature greater than the selected
engine temperature range, the ignition vacuum spark advance
mechanism operates in a normal manner to advance the ignition spark
in accordance with engine vacuum.
From this description it is apparent that the ignition spark vacuum
advance system of this invention provides:
1. With the engine operating at a temperature less than a selected
engine temperature range, the ignition spark vacuum advance
mechanism operates in a normal manner to advance the ignition spark
as a function of manifold vacuum at all vehicle speeds.
2. With the engine operating at normal temperature, the ignition
spark is retarded below a vehicle speed of a selected
magnitude.
3. With the engine operating at normal temperature, the ignition
spark vacuum advance mechanism operates in a normal manner to
advance the ignition spark as a function of manifold vacuum with
vehicle speeds greater than the selected magnitude.
4. With the engine operating at a temperature greater than a
selected engine temperature range, the ignition spark vacuum
advance mechanism operates in a normal manner to advance the
ignition spark as a function of manifold vacuum at all vehicle
speeds, including standstill.
5. A hysteresis feature is introduced to provide for ignition spark
retard at normal engine temperature until the vehicle has reached a
speed of a selected magnitude upon acceleration and to introduce
ignition spark retard when the vehicle has decelerated to a speed
less than the selected magnitude upon deceleration.
While a preferred embodiment of the present invention has been
shown and described, it will be obvious to those skilled in the art
that various modifications and substitutions may be made without
departing from the spirit of the invention which is to be limited
only within the scope of the appended claims.
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