U.S. patent number 3,797,465 [Application Number 05/156,439] was granted by the patent office on 1974-03-19 for fuel injection system for internal combustion engines.
This patent grant is currently assigned to Nippondenso Co., Ltd.. Invention is credited to Nobuhito Hobo, Norio Omori.
United States Patent |
3,797,465 |
Hobo , et al. |
March 19, 1974 |
FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES
Abstract
A fuel injection system for internal combustion engines is
disclosed, in which there are provided fuel injection patterns for
engine starting and for full-load engine operations. Cold starting
of the engine is facilitated by injecting fuel according to the
fuel injection control pattern required by the engine at the time
of starting, and once after the engine has been started or when
engine has been warmed up the fuel injection is made according to
the fuel control pattern required for full-load operation, so that
no black smoke generates even if the engine is rotated at a low
speed with the full-load, thereby ensuring optimum fuel supply over
the entire engine speed and engine load ranges without sacrificing
the engine output for full-load operation of the engine.
Inventors: |
Hobo; Nobuhito (Inuyama,
JA), Omori; Norio (Kariya, JA) |
Assignee: |
Nippondenso Co., Ltd.
(Aichi-ken, JA)
|
Family
ID: |
26399514 |
Appl.
No.: |
05/156,439 |
Filed: |
June 24, 1971 |
Foreign Application Priority Data
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Jul 4, 1970 [JA] |
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45-58456 |
Jul 4, 1970 [JA] |
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45-58457 |
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Current U.S.
Class: |
123/357; 123/362;
123/179.17 |
Current CPC
Class: |
F02D
41/38 (20130101); F02D 2250/38 (20130101) |
Current International
Class: |
F02D
41/38 (20060101); F02m 051/00 () |
Field of
Search: |
;123/32EA,32AE,139E,139,179HG |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
We claim:
1. A fuel injection system for internal combustion engines
comprising:
circuit means for generating an engine starting control voltage,
said control voltage varying according to the fuel control pattern
required for cold starting of an engine, said engine starting
control voltage being relatively high for low engine speeds,
circuit means for generating a full-load engine operating control
voltage, said control voltage varying according to the fuel control
pattern required for a full-load operation of the engine, said
full-load control voltage being relatively low for high engine
speeds, wherein as the speed of said engine increases to full-load
operation, said engine starting control voltage decreases to said
full-load control voltage,
a selecting circuit responsively coupled to each of said
aforementioned circuit means for selecting the higher one of the
control voltages generated by said control voltage generating
circuit means,
a monostable timing pulse generator connected to said selecting
circuit for providing timing pulses having a pulse duration
corresponding to the selected control voltage, and
a fuel injection pump responsive to said timing pulses having an
electromagnetic valve to control the quantity of fuel discharged
from said fuel injection pump in each cycle thereof in accordance
with the pulse duration of the timing pulse delivered from the
timing pulse generator, said engine starting control voltage
generating means including means for changing the control voltage
in response to a selected condition of engine operation.
2. The fuel injection system of claim 1 wherein said engine
starting control voltage generating circuit means includes means
for generating the control voltage in accordance with two preset
control patterns, namely, a first higher voltage pattern and a
second lower voltage pattern, and means for selecting the control
voltage of said first voltage pattern in response to an engine
cranking condition only.
3. The fuel injection system of claim 1 wherein said engine
starting control voltage generating circuit means includes means
for generating the control voltage in accordance with two preset
control patterns, namely, a first higher voltage pattern and a
second lower voltage pattern, and means for selecting the control
voltage of said higher voltage pattern in accordance with a cold
engine condition only.
4. The fuel injection system of claim 1 wherein said engine
starting control voltage generating circuit means includes means
for varying the control voltage of the control pattern to be
changed in response to an instantaneous engine temperature
condition.
5. The fuel injection system of claim 2 wherein said engine
starting control voltage generating circuit means includes,
means for changing each control voltage of both the higher and
lower voltage patterns in response to an instant engine temperature
condition.
Description
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to fuel injection systems for compression
ignition engines in which excessive air is introduced into each
cylinder and output power is controlled by varying the quantity of
pressurized fuel injected into each cylinder. More particularly,
the invention concerns fuel injection systems having an electronic
fuel control means.
2. DESCRIPTION OF THE PRIOR ART
Some prior-art fuel injection systems comprise a reciprocal fuel
pump having a reciprocating piston for drawing and discharging fuel
and provided with a normally closed electromagnetic valve. When the
electromagnetic valve is open, fuel under a comparatively low
constant pressure is admitted through it into a compression chamber
defined between the piston and cylinder of the fuel pump. A
separately provided electronic control means provides electric
pulses to the electromagnetic valve to open it. The electromagnetic
valve controls the quantity of fuel supplied to the compression
chamber mentioned above according to the duration of the electric
pulse delivered to it. The fuel supplied to the compression chamber
is further pressurized by the reciprocating piston and then
delivered through pressurized fuel piping to each fuel injection
nozzle, from which it is injected into the associated engine
cylinder.
A different type of prior-art fuel injection system from the
above-mentioned one is similar to the commonly termed unit
injector. In this type of fuel injection system, each engine
cylinder is provided with a fuel injection port, and the fuel to be
injected is supplied to a compression chamber in the unit injector
through a normally closed electromagnetic valve in proportion to
the duration of the open state of the electromagnetic valve exactly
controlled from an electronic control means. The fuel supplied to
the compression chamber is pressurized by a piston operated with
cam member usually provided on the engine cylinder head and driven
from the engine crankshaft, and the pressurized fuel is injected
into each cylinder.
It is also well known that more fuel is required when starting the
engine at a relatively low temperature than is necessary when the
engine has been warmed up. Further, it is well known that the fuel
injection pattern is determined so as to supply to the engine
sufficient fuel quantity available for engine starting even when
the engine is at a lowest possible temperature that would be
encountered, with an engine speed of about 200 rpm, at the time of
cranking, and under a condition substantially equivalent to full
load condition with the accelerator pedal depressed to the utmost,
and, subsequently, the fuel quantity gradually reduced to the one
determined by smoke limit for an engine speed slightly higher than
that at the time of cranking, usually 1,200 rpm, so as to ensure
smooth starting of the engine.
However, with such a fuel injection pattern, in which the quantity
of fuel supply is predetermined with respect to just the smoke
limit for an engine speed of, for instance, 1,200 rpm, a great deal
of black smoke inevitably results when the engine having warmed up
is operated under the full-load condition at a lower speed, for
instant about 1,000 to 800 rpm. This problem encountered in the
conventional fuel injection system of either mechanical or
pneumatic control type for internal combustion engines, cannot be
solved unless the construction of the system is made extremely
complicated. At present, therefore, it is usual to predetermine the
quantity of fuel supplied for low-speed engine operation with
respect to a quantity less than the smoke limit by making the fuel
increase for the starting of the engine as small as possible even
with slight sacrifice in the full-load engine output so as to
reduce the black smoke when the engine having warmed up is operated
at low speeds. Therefore, it has heretofore been impossible to
always operate the engine under the optimum fuel supply condition
irrespective of the engine speed and engine load.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fuel injection system
for internal combustion engines comprising an engine starting
control voltage generator to provide a control voltage meeting the
fuel control pattern required for the cold starting of the engine,
a full-load engine operation control voltage generator to provide a
control voltage meeting the fuel control pattern required for the
full-load operation of the engine, a selecting circuit to select
the higher of the output control voltage of both said control
voltage generators, a monostable timing pulse generator to provide
timing pulses with a pulse duration corresponding to said selected
output control voltage, and a fuel injection pump provided with an
electromagnetic valve to control the quantity of fuel discharged
from said fuel injection pump is each cycle thereof in accordance
with the pulse duration of the timing pulse delivered from the
timing pulse generator, at least said engine starting control
voltage generator, being provided with means to control the control
voltage according to the engine operation.
Another object of the invention is to provide means to generate the
output control voltage of two preset control patterns of said
engine starting control voltage generator, namely a higher voltage
pattern and a lower voltage pattern, and select a control voltage
of said higher voltage pattern only when the engine is being
cranked or before the engine has been warmed up.
Further object of the invention is to provide means to produce an
output control voltage of the control pattern of said engine
starting control voltage generator which may be changed
corresponding to the instant engine temperature.
According to the invention, in case there are provided two preset
voltage patterns, namely a high voltage pattern and lower voltage
pattern, for the control voltage of the engine starting control
voltage generator, which is provided with means to select an output
control voltage of said high voltage pattern out of said two preset
voltage patterns by detecting the cranking of the engine or by
detecting a predetermined tmeperature of the engine warmed up, the
fuel to be injected at the time of the cranking of the engine is
controlled according to the high voltage pattern of the output
control voltage of the engine starting control voltage generator
meeting the fuel control pattern required at the time of cranking
of the engine, thus ensuring extremely smooth starting of the
engine.
Also, after the engine has been cranked, or when the engine has
been warmed up according to the lower voltage pattern selected for
the control voltage of the engine starting control voltage
generator, and the fuel injection pattern determined by the control
voltage output of the full-load engine operation control voltage
generator, the fuel to be injected is controlled so that no black
smoke generates even if the engine is rotated at a low speed with
the full-load, thus ensuring operation of the engine under the
optimum fuel supply condition over the entire engine speed and
engine load ranges without sacrificing the full-load engine
output.
Further, according to the invention, a starter switch is used for a
means to detect the cranking of the engine, so that selection of
the low voltage pattern is reliably and automatically effected
whenever the engine is being cranked by the simple on-off operation
of the starter swtich of extremely simple construction.
Still further, according to the invention, a bimetal switch is used
for a means to detect a predetermined temperature of the engine
warmed up so that selection of the lower voltage pattern is
reliably and automatically effected whenever the engine has been
warmed up.
Still further, according to the invention, a semiconductor
temperature-sensitive element having a negative resistance
characteristic is used for a means to detect the instant engine
temperature and be able to change the voltage pattern corresponding
to the detected temperature so that the engine may be started
smoothly even if the engine is at a low temperature since the fuel
is supplied according to said voltage pattern.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a graph showing a fuel injection pattern to be provided
by an electronic control means in the system according to the
invention.
FIG. 2 is a block diagram outlining an embodiment of the fuel
injection system according to the invention.
FIGS. 3a to 3d show characteristic curves of various parts of the
system of FIG. 2.
FIG. 4 is a circuit diagram showing an example of the control
voltage generator circuit in the system of FIG. 2.
FIGS. 5a to 5c show characteristic curves illustrating the
operation of the circuit of FIG. 4.
FIG. 6 is a circuit diagram showing part of the system according to
the invention.
FIG. 7 is a graph to illustrate the operation of the circuit of
FIG. 6.
FIG. 8 is a circuit diagram showing part of the system according to
the invention.
FIG. 9 is another circuit diagram showing part of the system
according to the invention.
FIG. 10 is a graph to illustrate the operation of the circuit of
FIG. 9.
FIG. 11 is still further circuit diagram showing part of the system
according to the invention.
FIG. 12 is a graph to illustrate the operation of the circuit of
FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention will become more apparent from the following
description of a preferred embodiment with reference to the
accompanying drawing.
FIG. 1 shows one of fuel characteristics of internal combustion
engines for vehicles, namely a fuel characteristic required when
the accelerator pedal is depressed to the utmost. In the Figure,
the ordinate represents the quantity Q of fuel injected and the
abscissa represents the engine speed N. Reference character a
indicates the quantity of fuel required at the time of cold
starting of the engine, character b indicates a fuel characteristic
at the time of operation of the starter motor, and character c
indicates the quantity of fuel required for the full-load engine
operation. N.sub.1 indicates an engine speed corresponding to the
smoke limit. For a full-load low-speed engine operation after the
engine has been started, a fuel characteristic as indicated at b'
determined from the smoke limit consideration is required instead
of the character b.
FIG. 2 shows a fuel injection system according to the invention. A
control voltage generating circuit 1 provides control voltage Vc
whose voltage pattern corresponds to the fuel characteristics
required by the engine.
FIG. 3a shows a control voltage pattern provided (with the ordinate
representing the control voltage Vc and abscissa representing the
engine speed N).
The control voltage Vc is fed to a timing pulse generator 2, which
also receives trigger pulses from a trigger pulse generator coupled
to the drive shaft of a fuel injection pump 4 to produce timing
pulses. It may consist of a monostable multi-vibrator. The duration
of the timing pulse is controlled in proportion to the control
voltage Vc of the control voltage generating circuit 1.
FIG. 3b shows the duration .tau. of the timing pulse plotted
against the control voltage Vc.
The output of the timing pulse generator 2 is applied across an
electromagnetic coil of an electromagnetic valve 3, which is held
open during the presence of a timing pulse, that is, held open for
the duration of the timing pulse. While the electromagnetic valve
is held open, it admits fuel from a fuel supply pump to be drawn
into the fuel injection pump 4.
FIG. 3c shows the quantity of fuel drawn into the fuel injection
pump 4, which is plotted against the duration .tau. of the timing
pulse.
The quantity of the fuel discharged from the fuel injection pump 4
in each cycle thereof is equal to the quantity of fuel admitted
thereto in each cycle of the electromagnetic valve 4. The relation
between the quantity of fuel discharged from the fuel injection
pump 4 and the engine speed is substantially the same as the
control voltage pattern shown in FIG. 3a.
FIG. 3d shows the quantity Q of the discharged fuel plotted against
the engine speed N.
FIg. 4 shows the control voltage generating circuit in detail.
Reference numeral 5 generally designates an engine starting control
voltage generator, numeral 6 a full-load engine operation control
voltage generator, and numeral 7 a selecting circuit including a
current amplifier. Numeral 8 designates a speed voltage generator
generating a voltage corresponding to the speed of rotation of the
drive shaft of the fuel injection pump 4 (hereinafter referred to
as speed voltage). It may be a d-c generator coupled to the drive
shaft of the fuel injection pump 4.
The engine starting and full-load engine operation control voltage
generators 5 and 6 include respective two-input differential
amplifiers 9 and 9a. The speed voltage from the speed voltage
generator 8 consitiutes an inversion input to the differential
amplifiers 9 and 9a, and voltages V.sub.S1 and V.sub.S2
corresponding to turning points in the respective control voltage
patterns at the time of engine starting and at the time of
full-load engine operation are fed as non-inversion input to the
respective differential amplifiers through potentiometers 10 and
11. The outputs of the differential amplifiers 9 and 9a are divided
by respective voltage dividers 12 and 15 respectively consisting of
potentiometers 14 and 13.
The selecting circuit 7 comprises diodes 16 and 17, a transistor 18
and resistors 19 and 20. Of the two voltages V.sub.c1 and V.sub.c2
appearing at the output of the respective voltage dividers 12 and
15, the higher one is selectively fed through either diode 16 or 17
to the emitter follower of transistor 18 and resistors 19 and 20
for current amplification to produce an amplified output across the
resistor 20 as the control voltage Vc.
FIG. 5a shows the voltage V.sub.c1 appearing at the output of the
voltage divider 12 of the engine starting control voltage generator
5 plotted against the speed of the drive shaft of the fuel
injection pump 4 represented by the speed voltage V.sub.S.
FIG. 5b shows the voltage V.sub.c2 appearing at the output of the
voltage divider 15 of the full-load engine operation control
voltage generator 6.
FIG. 5c shows the resultant control voltage Vc appearing at the
output of the selecting circuit 7 selectively current amplifying
the higher one of the voltages V.sub.c1 and V.sub.c2. The pattern
of the control voltage Vc shown in FIG. 5c is made the same as that
of the fuel characteristic shown in FIG. 1, and hence the same as
the pattern of the fuel discharged by the fuel injection pump
4.
To change the fuel injection pattern at the time of starting the
engine and at other times, the control voltage pattern of the
control voltage generating circuit 1 may be changed
accordingly.
FIG. 6 shows an example of engine starting control voltage
generator 5, whose voltage divider 12 consists of resistors 21, 22
and 23. Numeral 24 designates a starter motor, numeral 25 a relay
having a relay coil 26 and normally open contacts 27, numeral 28 a
key switch having movable contacts 29, ignition terminals 30 and a
starter terminal 29a, numeral 31 a relay having a relay coil 32 and
normally closed contacts 33, and numeral 34 a battery.
In operation, for starting the engine the movable contacts 29 of
the key switch 28 are thrown to the starter terminal 29a, whereupon
the normally open contacts 27 of the relay 26 are closed to start
the starter motor 24, thus starting the engine. At the same time,
the normally closed contacts 33 of the relay 31 are opened, so that
the control voltage appearing at the voltage dividing point p takes
a high voltage pattern as indicated at e in FIg. 7. With the high
voltage pattern selected, the duration of the timing pulse produced
by the monostable timing pulse generator 2 is increased to increase
the quantity Q of fuel discharged from the fuel injection pump 4,
thus achieving rapid starting of the engine.
When the engine has been cranked, the movable contacts 29 of the
key switch 28 are detached from the starter terminal 29a to open
the normally open contacts 27 of the relay 25, thus stopping the
starter motor 24. At the same time, the normally closed contacts 33
of the relay 31 are closed to connect the resistor 23 in parallel
with the resistor 22 in the voltage divider 12, so that the control
voltage appearing at the voltage dividing point p takes a low
voltage pattern as indicated at f in FIG. 7. Thus, the subsequent
resultant control voltage Vc of the control voltage generating
circuit 1 is mainly determined by the control voltage V.sub.c2 of
the full-load engine operation control voltage generator 6, and the
quantity Q of fuel discharged from the fuel injection pump 4 is
controlled according to a fuel injection pattern mainly determined
by the control voltage V.sub.c2 of the full-load engine operation
control voltage generator 6.
FIg. 8 shows another example of the engine starting control voltage
generator 5, whose voltage divider 12 comprises resistors 35, 36
and 37 and a bimetal switch 38. The bimetal switch 38 is made to
open and close by detecting a predetermined engine temperature.
When the engine temperature is lower than a predetermined
temperature, the bimetal switch 38 is open. Under this condition, a
higher voltage patterns as shown by curve e in FIG. 7 is provided
for the voltage V.sub.c1 appearing at the voltage dividing point p.
When the engine temperature exceeds the predetermined temperature,
the bimetal switch 38 is closed to provide a lower voltage pattern
as shown by curve f for the voltage V.sub.c1.
In the preceding embodiments, the engine starting control voltage
generator 5 is adapted to provide two alternative voltage patterns
for its control voltage V.sub.c1. If desired, the full-load engine
operation control voltage generator 6 may also be adapted to
provide two alternative voltage patterns for its control voltage
output V.sub.c2.
To change the fuel injection pattern especially at the time of cold
starting, the control voltage of the control voltage generating
circuit 1 may be changed sequentially according to the engine
temperature.
FIG. 9 shows further example of the engine starting control voltage
generator 5, in which a semiconductor temperature-sensitive element
40 having a negative resistance characteristic such as thermistor
is connected in series with the resistor 39 of the voltage divider
12. The temperature-sensitive element 40 is placed within the
engine clyinder block or cooling water passage so as to detect the
engine temperature.
In the operation of this example, when the engine temperature is
low the resistance of the temperature-sensitive element 40 is high,
so that the lower the engine temperature the higher the voltage
V.sub.c1 appearing at the voltage dividing point p, as shown by
broken curves i, j, and k in FIG. 10.
With a higher voltage pattern for the voltage V.sub.c1 the pulse
length of the timing pulse produced by the timing pulse generator 2
is increased to increase the quantity Q of fuel discharged from the
fuel injection pump 4. With an increase in the engine temperature
the voltage V.sub.c1 is progressively decreased to eventually
provide a voltage pattern for normal running as shown by solid
curve h.
It will be apparent that the voltage divider 15 in the full-load
operation control voltage generator 6 may, if necessary, be
provided with a semiconductor temperature-sensitive element having
a negative resistance characteristic like the voltage divider 12 in
the preceding example of the engine starting control voltage
generator 5.
FIG. 11 shows still further example of the engine starting control
voltage generator 5, whose voltage divider 12 comprises resistors
21, 22 and 23, and a semiconductor temperature-sensitive element 40
having the same characteristics as the one shown in FIG. 9. The
resistor 23 is connected at one end thereof to the means to detect
the engine cranking which consists of the relay 31, the key switch,
the relay 25 and the starter motor as mentioned in FIG. 6.
In the operation of this example, when the engine is being cranked,
the lower is the engine temperature, the higher is the voltage
V.sub.c1 appearing at the voltage dividing point P, as shown by
broken curves m, n and o in FIG. 12. And after the engine has been
started, the voltage V.sub.c1 appearing at the voltage dividing
point P moves from higher levels shown by curves m, n and o to the
lower levels shown by curves r, s and t, respectively, so that the
generation of black smoke can be prevented even if the engine is
rotated at a low speed with the full-load at a low temperature,
namely before the engine has been warmed up.
* * * * *