Fuel boosting system for internal combustion engine

An automatic fuel boosting system for supplying an optimum amount of fuel to an internal combustion engine based on engine temperature. This fuel boosting system includes a sensor for sensing if the engine temperature at the time of starting is below a predetermined value, an advance angle control circuit, responsive to the sensor, for advancing the ignition angle based on engine temperature, and a solenoid, responsive to the control circuit, for actuating a fuel boosting device so that an optimum amount of fuel is supplied to the intake manifold of the engine based on engine temperature, if the engine temperature is sensed to be below the predetermined value.

BACKGROUND OF THE INVENTION 
This invention relates to a fuel boosting system in an internal combustion 
engine which is automatically activated based on engine temperature. 
In many forms of engines, there is provided a manual device for supplying 
an increased amount of fuel to the engine at the time of starting when the 
engine temperature is low. However, since the additional fuel required 
when starting the engine varies depending on the atmospheric and engine 
temperatures, an optimum amount of fuel cannot be supplied by a manual 
device. 
An object of this invention, therefore, is to provide an automatic fuel 
boosting system for supplying an optimum amount of fuel to the engine 
based on engine temperature without relying simply on manual boosting. 
A further object of this invention is to provide an automatic fuel boosting 
system which simultaneously advances the ignition angle based on engine 
temperature. 
The fuel boosting system should preferably include a sensor for sensing the 
engine temperature at the time of starting and an advance angle control 
circuit, which is responsive to the sensor, for advancing the ignition 
angle and for energizing a solenoid based on engine temperature. When the 
solenoid is energized, it actuates a fuel boosting device so that fuel is 
pumped into the engine intake manifold based on engine temperature. 
SUMMARY OF THE INVENTION 
An automatic fuel boosting system in an internal combustion engine which 
includes a sensor for sensing if the engine temperature at the time of 
starting is below a predetermined value, an advance angle control circuit, 
responsive to the sensor, for advancing the ignition angle based on the 
engine temperature, and a solenoid, responsive to the control circuit, for 
actuating a fuel boosting device so that an optimum amount of fuel is 
supplied to the intake manifold of the engine based on the engine 
temperature, if the engine temperature is sensed to be below the 
predetermined value. 
The advance angle control circuit preferably includes an ignition angle 
advance circuit having a control timer. The control timer is responsive to 
the sensor. When the engine temperature is sensed to be below the 
predetermined value at the time of starting, the control timer and, 
accordingly, the control circuit are switched on for a particular period 
of time based on engine temperature. When the control timer is switched 
on, the ignition angle advance circuit advances the ignition angle a 
particular degree for a particular period of time based on the engine 
temperature. The switching on of the control timer simultaneously 
energizes a solenoid for a particular period of time based on the engine 
temperature. When the solenoid is energized it actuates the fuel boosting 
device, so that an optimum amount of fuel is supplied to the engine intake 
manifold for a particular period of time based on engine temperature. When 
the timer goes off, the ignition angle advance circuit performs ignition 
timing based on the throttle opening or engine rpm and the solenoid is no 
longer energized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, the internal combustion engine 10 is supported 
so that its output shaft rotates about a vertically extending axis. A 
drive shaft driven by the engine output shaft extends into a driveshaft 
housing (not shown). This drive shaft extends to a lower unit (not shown) 
so as to drive a propeller or other form of propulsion device in a known 
manner. 
Referring now in detail to FIG. 1, the engine 10 is comprised of a cylinder 
block 11 in which three cylinder bores extend in a horizontal direction, 
as is conventional outboard motor practice. In the illustrated embodiment, 
the internal combustion engine is depicted as being of the three cylinder 
in line, crankcase compression, two-cycle type. It is to be understood, of 
course, that the invention may be utilized in conjunction with other types 
of engines than the two-cycle type and also engines having different 
numbers of cylinders or different cylinder configurations. 
Pistons are supported for reciprocation within each of the cylinder bores 
and are connected by means of connecting rods 12 to a crankshaft 13. The 
crankshaft 13 is rotatably journaled in a crankcase formed by the cylinder 
block 11 and rotates about a generally vertically extending axis. The 
crankshaft 13 is connected to the output shaft which drives the drive 
shaft as aforenoted. As is conventional with two cycle internal combustion 
engines, the crankcase is formed with a plurality of individually sealed 
crankcase chambers 14, each associated with a respective cylinder bore. 
A cylinder head is affixed to the cylinder block 11 in a known manner and 
defines three individual recesses, each of which cooperate with a 
respective cylinder bore and piston so as to define combustion chambers 
which vary in volume as the pistons reciprocate. Spark plugs 15 are 
mounted in the cylinder head with each of their gaps extending into a 
respective combustion chamber recess for a respective cylinder. 
A fuel/air charge is delivered to these chambers by means of an induction 
and charge forming system. This induction and charge forming system 
includes an air inlet device 16 that draws air from within the protective 
cowling and delivers it to a plurality of carburetors 17. 
Each carburetor is comprised of a respective induction passage 25 in which 
a flow controlling throttle valve 18 is supported in a known manner. A 
fuel bowl 19 is maintained with a constant head of fuel by means of a 
float 55 (see FIG. 2) and an operating valve (not shown) and supplies fuel 
to a main discharge nozzle 20 positioned in the venturi section of the 
induction passage 25 of the carburetor 17 upstream of the throttle valve 
18. In addition, the carburetors 17 are provided with discharge ports 
positioned downstream of the venturi sections and which control the flow 
of fuel/air mixture supplied to the engine in a known manner. The throttle 
valves 18 are all linked together by means of a linkage system 21 so that 
their movement will be synchronized. 
The carburetors 17 deliver the fuel/air charge to an intake manifold 22 
having individual manifold passages 22A, each of which discharges into a 
respective crankcase chamber 14. Reed type check valves 23 are positioned 
in each of the manifold passages 22A to preclude reverse flow through the 
manifold passages 22A, as is well known in this art. 
A spacer plate 24 is interposed between the carburetors 17 and the manifold 
22. The spacer plate 24 has individual passageways that provide 
communication between the carburetor induction passages 25 and the 
manifold passages 22A. 
The fuel/air charge which is delivered to the crankcase chambers 14 by the 
carburetors 17 is transferred upon descent of the pistons into the 
combustion chambers by transfer or scavenge passages in a known manner. At 
the appropriate time, the spark plugs 15 are fired. 
The firing power for the spark plugs 15 is derived from a magneto 
generator, which includes a flywheel magneto 27 that is affixed to the 
crankshaft 13 for rotation with it by a key and a nut. The flywheel 
magneto 27 carries a plurality of permanent magnets that cooperate with a 
charging coil 28 that is affixed to a boss of the cylinder block 11 in 
proximity thereto. The engine further includes a plurality of pulser coils 
29, one for each cylinder. These pulser coils 29 are mounted on a mounting 
ring of the flywheel magneto 27 and cooperate with the magnets so as to 
provide signals when the crankshaft 13 is at specified crank angles. 
The engine 10 may also be provided with an electric starter including a 
starter gear 30 that is affixed to the flywheel magneto 27 and which is 
driven by a suitable starter motor 85 (see FIG. 3). A sensor coil may be 
associated with the teeth of the starter 85 for providing a signal that is 
indicative of the actual rotation angle of the crankshaft 13. The engine 
10 also includes ignition coils 31, one associated with each spark plug 
15. 
In accordance with the invention there is provided a fuel boosting system 
for automatically supplying an optimum amount of fuel at the time of 
starting based on engine temperature. In addition, this fuel boosting 
system automatically advances the ignition angle and, accordingly, the 
timing of the firing of the spark plugs 15 at the time of starting based 
on engine temperature. 
This fuel boosting system includes a temperature sensor 35 for sensing if 
the temperature of the engine at the time of starting is below a 
predetemined value. The system also includes an advance angle control 
circuit 36 which has an ignition angle advance circuit 37 (see FIG. 3) for 
automatically advancing the timing on the basis of engine temperature and 
engine speed which is measured by the charging coil 28. The control 
circuit 36 also includes a control timer. The system further includes a 
fuel boosting device 38 for supplying an optimum amount of fuel to the 
engine and solenoid 39 for actuating the boosting device 38. This fuel is 
pumped by the boosting device 38 through a discharge conduit 40 to a 
suction passage 41 formed in the intake manifold 22. The details of the 
fuel boosting device 38 are illustrated in FIG. 2. The details of the 
ignition circuit including the sensor 35, the control circuit 36, 
including the advance circuit 37, and the solenoid 39 is illustrated in 
FIG. 3. 
Referring now to FIG. 2, the fuel boosting device 38 includes a diaphragm 
pump 45 positioned within a pump chamber 46 that is actuated by pressure 
variations in one of the crankcase chambers 14 through a conduit 47. Fuel 
is delivered to the pump 45 from a well 48 formed in one of the carburetor 
bodies 17 and which receives fuel from its fuel bowl 19. The well 48 
communicates with the pump 45 by means of a conduit shown schematically in 
FIG. 2 and indicated by reference numeral 49. A metering jet 54 controls 
the flow of fuel through the conduit 49. An inlet valve 50 is positioned 
between the conduit 49 and pump chamber 46 to control the flow of fuel to 
the pump 45. An outlet valve 51 between the pump chamber 46 and the 
discharge conduit 40 controls fuel flow out of the pump 45. The fuel is 
delivered to the intake manifold 22 by the discharge conduit 40, which is 
positioned externally of the engine 10, when the temperature of the engine 
10 is below a predetemined value. The discharge conduit 40 communicates 
with the pump 45 through an opening 52 in the fuel boosting device 38. The 
fuel flow to the intake manifold 22 is controlled by means of a fuel 
control valve 53 which is responsive to the solenoid 39. The valve 53 is 
open when the solenoid 39 is energized and closed when the solenoid 39 is 
not energized. 
The engine 10 also includes a float 55 and an operating valve which 
maintain a constant head of fuel in the fuel bowl 19. 
In the preferred embodiment, the fuel boosting system includes a manual 
valve, designated generally by reference numeral 66 and shown 
schematically in FIG. 2. This manual valve 66 is used for supplying 
additional fuel at the time of starting when the engine temperature is low 
and when the fuel boosting device 38 is inoperative. The valve 66 
communicates with the fuel boosting device 38 so that fuel can be supplied 
from the well 48 to the intake manifold 22 without flowing through the 
fuel control valve 53. 
The valve 66 is comprised of a lever 67 for opening and closing the valve 
66, and a core element 68. The manual valve 66 communicates with an inner 
chamber defined by the outlet valve 51 by an inlet conduit. A valve means 
69 is positioned between the inlet conduit and the core 68 to control the 
flow of fuel from the boosting device 38 to the manual valve 66. An outlet 
conduit permits the valve 66 to communicate with the discharge conduit 40 
downstream of the fuel control valve 53. 
The fuel boosting device 38 further includes a core 58 and a bobbin 59, 
which, along with the solenoid 39, are enclosed by a case 60. 
FIG. 3 illustrates a circuit diagram of the ignition system. This 
embodiment is depicted in conjunction with a two cylinder engine; however, 
as aforenoted the invention can be practiced in conjunction with engines 
having any number of cylinders or spark plugs. 
The ignition system includes a magneto generator comprised of a charging 
coil 28 and pulser coils 29. An ignition coil 31 is associated with each 
spark plug 15 and has its secondary windings in circuit with the terminals 
of the spark plug 15 in a known manner. The charging coil 28 and pulser 
coils 29 output their signals to an advance angle control circuit 
indicated by reference numeral 36. This circuit includes a charging 
capacitor 72 that is charged from the charging coil 28 through a 
rectifying diode 73. As is well known, the charging capacitor 72 is 
charged during the rotation of the engine output shaft and crankshaft 13. 
At the appropriate crankshaft angle, as determined by the output from the 
pulser coils 29, a silicon-controlled rectifier (SCR) 74 and specifically 
its gate 75 is rendered conductive by means of a wave shaping circuit 76. 
When this occurs, the ignition coils 31 will have a voltage induced in 
their primary windings which is magnified in the secondary windings for 
firing the spark plugs 15 in a known manner. A diode is placed between the 
charging coil 28 and the rectifying diode 73 for providing a circuit 
during the negative half way of the charging coil 28. 
The circuit is also provided with an arrangement for advancing the ignition 
angle and, accordingly, the firing of the spark plugs 15 based on engine 
temperature as sensed by the temperature sensor 35 at the time of 
starting. The temperature sensor 35 outputs its signals to the control 
circuit 36. If the engine temperature is below a predetermined value at 
the time of starting, a control timer of the control circuit 36 is 
switched on for a particular period of time based on engine temperature. 
The switching on of the control timer actuates the advance circuit 37 to 
advance the ignition angle and spark plug timing based on engine 
temperature. 
The circuit further includes a battery 77. When the engine 10 is started, a 
starter switch 78, responsive to a relay switch 79, is closed. The closing 
of the starter switch 78 during starting permits current from the battery 
77 to flow to a right switch 80 in circuit with the battery 77 and the 
solenoid 39, and which controls the flow of battery current to the 
solenoid 39. When the right switch 80 is closed current from the battery 
77 energizes the solenoid 39. 
The solenoid 39 can also be energized by current from a generating coil 81. 
A rectifier circuit 82 converts the AC input from the generating coil 81 
into a DC waveform which flows to a left switch 83 in circuit with the 
generating coil 81 and the solenoid 39, and which controls the flow of 
current from the generating coil 81 to the solenoid 39. 
A control circuit 84 controls the opening and closing of the right and left 
switches 80 and 83 and thus the energizing of the solenoid 39, based on 
the signals received from the temperature sensor 35. 
The ignition circuit also includes a starter motor 85 in circuit with the 
battery 77. The relay switch 79 control current flow from the battery 77 
to the starter motor 85 and also controls the position of the starter 
switch 78 such that the closing of the relay switch 79 causes the starter 
switch 78 to also close. 
The ignition circuit also includes a fuse 86 in circuit with the generating 
coil 81 and the battery 77. 
The preferred embodiment of the invention, is illustrated graphically and 
diagramatically in FIGS. 4, 5 and 6. If the sensor 35 detects the engine 
temperature to be below a predetermined value, 50 degress Celsius for 
example, when the starter switch 78 is in the on or closed position, the 
control timer is switched on for a particular period of time in accordance 
with FIG. 5. The actuation of the timer actuates the ignition angle 
advance circuit 37 to advance the ignition angle a particular degree 
before the top dead center mark on the crankshaft 13 and, accordingly, the 
spark plug timing based on the engine temperature as shown in FIG. 4 for a 
period of time as shown in FIG. 5. Simultaneous with the actuation of the 
advance circuit 37, the solenoid 39 is energized to open the valve 53 in 
the boosting device 38 for a period of time as shown in FIG. 5 so that the 
fuel boosting device 38 is truned on and fuel is pumped with the diaphragm 
pump 45 to the suction passage 41 formed in the engine intake manifold 22. 
After the timer shuts off, the ignition angle is advanced based on throttle 
opening or engine rpm. Similarly, if the sensor 35 detects the engine 
temperature to above a predetermined value, 50 degrees Celsius as shown in 
FIGS. 4 and 5, at the time of starting, ignition angle advancement is 
performed according to throttle opening or engine rpm. 
The foregoing descriptions represent merely exemplary embodiments of the 
invention. Various changes and modifications may be made without departing 
from the spirit and scope of the invention, as defined by the appended 
claims.