U.S. patent number 3,612,020 [Application Number 05/039,258] was granted by the patent office on 1971-10-12 for compensating fuel metering for exhaust gas recirculation.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to John W. Moulds.
United States Patent |
3,612,020 |
Moulds |
October 12, 1971 |
COMPENSATING FUEL METERING FOR EXHAUST GAS RECIRCULATION
Abstract
In an internal combustion engine, exhaust gas is recirculated
from the intake manifold exhaust gas crossover passage to the
induction passage. An exhaust gas recirculation control valve is
positioned by the throttle to proportion exhaust gas recirculation
flow to induction airflow. In one embodiment, the exhaust gas
recirculation passages are cast integrally in the intake manifold.
Fuel metering in a timed fuel injection system responsive to
manifold absolute pressure is compensated for exhaust gas
recirculation.
Inventors: |
Moulds; John W. (Penfield,
NY) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
21904510 |
Appl.
No.: |
05/039,258 |
Filed: |
May 21, 1970 |
Current U.S.
Class: |
123/478 |
Current CPC
Class: |
F02M
26/41 (20160201); F02D 21/08 (20130101); F02M
1/00 (20130101) |
Current International
Class: |
F02D
21/00 (20060101); F02M 25/07 (20060101); F02D
21/08 (20060101); F02M 1/00 (20060101); F02m
025/06 () |
Field of
Search: |
;123/119A,32EA,139AW,119 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Burns; Wendell E.
Claims
I claim:
1. In an internal combustion engine having an induction passage for
airflow to the engine, a throttle in said induction passage
controlling airflow therethrough, and an exhaust passage for
exhaust gas flow from the engine: a fuel system for delivering fuel
to said engine, an exhaust gas recirculation passage extending from
said exhaust passage to said induction passage for recirculating
exhaust gas to said induction passage, and a valve in said exhaust
gas recirculation passage controlling exhaust gas flow
therethrough, said fuel system including means controlling fuel
delivery to said engine in accordance with the pressure in said
induction passage below said throttle whereby the rate of fuel
delivery to said engine tends to increase as the absolute pressure
in said induction passage downstream of said throttle increases,
said fuel system further including means controlling fuel delivery
to said engine in accordance with the position of said valve
whereby the rate of fuel delivery to said engine tends to decrease
as said valve permits increased recirculation of exhaust gas to
said induction passage, said fuel system thereby providing an
appropriate rate of fuel delivery to said engine as the pressure in
said induction passage below said throttle varies with variations
both in engine load and in the position of said throttle without
providing an inappropriate rate of fuel delivery to said engine as
the pressure in said induction passage below said throttle varies
with variations in exhaust gas recirculation to said induction
passage.
Description
In a fuel system which relies on manifold pressure as an indication
of airflow to the engine and meters fuel flow in accordance
therewith, fuel flow may be incorrectly proportioned to airflow
when exhaust gas is recirculated to the induction passage unless
the fuel metering is compensated for the partial pressure due to
exhaust gas. This invention provides means, particularly suited for
use with a timed fuel injection system, to adjust the fuel metering
in accordance with the position of a valve controlling exhaust gas
recirculation to the induction passage.
The details as well as other objects and advantages of this
invention are set forth below and shown by the drawings
wherein:
FIG. 1 is a top plan view of an induction passage throttle body and
an exhaust gas recirculation control valve;
FIG. 2 is a side elevational view of the device shown in FIG. 1
illustrating the configuration of the cam member;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1
illustrating the exhaust gas recirculation control valve;
FIG. 4 is a sectional view along line 4--4 of FIG. 1 illustrating
the control valve operating mechanism;
FIG. 5 is a sectional view along line 5--5 of FIG. 2 illustrating
the adjustable connection in the linkage between the exhaust gas
recirculation control valve and the throttle;
FIG. 6 is a top plan view of the FIG. 1 intake manifold
illustrating the exhaust gas crossover passage;
FIG. 7 is a top plan view of an alternative intake manifold having
integrally cast exhaust gas recirculation passages;
FIG. 8 is a sectional view taken along line 8--8 of FIG. 7
illustrating the openings from the exhaust gas recirculation
passage to the induction passages;
FIG. 9 is a view similar to FIG. 2 illustrating the
fuel-metering-compensating mechanism; and
FIG. 10 is a circuit diagram for an electronically controlled timed
fuel injection system illustrating two embodiments of
variable-impedance devices for compensating the fuel metering.
Referring first to FIGS. 1 and 2, a throttle body assembly 10 is
mounted on an intake manifold 12. A pair of induction passages 14
pass through assembly 10 and are controlled by a pair of throttles
16 disposed on a throttle shaft 18.
Inserted between throttle body assembly 10 and manifold 12 is a
plate 20 and a base 22 which have extensions of induction passages
14. Plate 20 and base 22 define an exhaust gas recirculation inlet
passage 24 leading to a control valve assembly 26 and an exhaust
gas recirculation outlet passage 28 leading from control valve
assembly 26. Branches 30 connect exhaust gas recirculation outlet
passage 28 with induction passages 14 below throttles 16. For
simplicity, exhaust gas recirculation inlet passage 24 will be
referred to merely as exhaust gas recirculation passage 24, exhaust
gas recirculation outlet passage 28 will be referred to as metered
exhaust gas passage 28, and the two passages 24 and 28 will be
referred to collectively as exhaust gas recirculation passages.
As shown in FIG. 3, exhaust gas recirculation control valve
assembly 26 has an inlet bore 32 leading from exhaust gas
recirculation passage 24 to an upper cross passage 34. A butterfly
valve 36 is disposed on a shaft 38 in an outlet bore 40 leading
from cross passage 34 to metered exhaust gas passage 28.
Shaft 38 is journaled on a pair of bushings 42 (FIG. 4) and has a
lever 44 (FIGS. 2 and 4) secured on the outer end thereof. A
torsion spring 46 (FIG. 4) biases shaft 38 and lever 44 in a
counterclockwise direction as viewed in FIG. 2.
The cover 48 for control valve assembly 26 provides a bracket
having an upstanding arm 50 (FIGS. 1 and 4) into which a pair of
bolts 52 are threadedly secured. As shown in FIG. 2, bolts 52
extend through a slot 54 in a cam member 56, thereby supporting cam
member 56 for linear motion.
An additional bolt 58 also extends through slot 54 and is secured
to an adjusting nut 60. Adjusting nut 60 threadedly receives a link
62 connected to a throttle lever 64 secured on throttle shaft
18.
A spring 66 biases cam member 56 leftwardly as viewed in FIGS. 1
and 2.
In operation, clockwise opening movement of throttles 16, throttle
shaft 18 and throttle lever 64 pulls link 62 and cam member 56
toward the right as viewed in FIG. 2. A cam follower 68 on control
valve lever 44 is biased against a cam surface 70 on cam member 56.
As is evident from FIG. 2, cam follower 68 successively contacts a
first portion 70a in which control valve 36 remains closed, a first
ramp 70b in which control valve 36 opens, a peak 70c in which
control valve 36 remains open, a second ramp 70d in which control
valve 36 closes, and a second portion 70e in which control valve 36
remains closed. The sequence is reversed as throttles 16 are closed
and spring 66 returns cam member 56 toward the left.
Cam surface 70 is configured whereby control valve 36 begins
opening movement when throttles 16 have been opened about
5.degree., reaches a fully open position when throttles 16 have
been opened between 14.degree. and 20.degree., and returns to
closed position when throttles 16 have been opened about
34.degree..
As control valve 36 opens, exhaust gas received through exhaust gas
recirculation passage 24 is admitted to metered exhaust passage 28
and delivered through branches 30 to induction passages 14.
It will be noted that since control valve 36 and cam member 56 are
biased in a valve-closing direction by springs 46 and 66, they
exert no opening force on throttles 16. Moreover, even if control
valve 36 or cam member 56 were to remain in an open position,
throttles 16 would be free to close because bolt 58 rides toward
the left in slot 54 as throttles 16 are closed.
Exhaust gas is received by exhaust gas recirculation passage 24
from an exhaust gas riser bore 72 connecting with an exhaust gas
crossover passage 74 which passes through intake manifold 12. As
may be seen in FIG. 6, intake manifold 12 includes a pair of
conventional riser passages 76 which communicate with generally
horizontal upper and lower plenum chambers 78 and 79 respectively.
Plenum chambers 78 and 79 extend longitudinally from the bottom of
riser passages 76 to transverse runner passages 80 at the ends
thereof. Exhaust crossover passage 74 extends from an inlet 75 at
one side of manifold 12, beneath riser passages 76 and plenum
chambers 78 and 79, to exhaust gas riser bore 72.
It will be appreciated, of course, that induction passages 14,
manifold riser passages 76, plenum chambers 78 and 79, and runner
passages 80 may be collectively referred to as an induction
passage.
FIGS. 7 and 8 show a modified intake manifold 12' in which the
exhaust gas recirculation and metered exhaust gas passages are cast
integrally in the manifold. The FIG. 7 view is schematic and
various combinations of dot-dash lines have been used to facilitate
visualization of the different passages. As shown in these figures,
a pair of riser passages 76 disposed on opposite sides of the
manifold centerline connect with upper and lower plenum chambers 78
and 79, respectively, which are generally horizontal and extend
longitudinally through the manifold to transversely reaching runner
passages 80.
An exhaust gas crossover passage 74' extends from an inlet 75' at
one side of the manifold centerline, beneath riser passages 76 and
plenum chambers 78 and 79, to the opposite side of the manifold
centerline. There exhaust gas crossover passage 74' discharges into
an exhaust gas recirculation passage 24'. Passage 24' leads to a
pad 82 which is adapted to receive control valve assembly 26.
Alternatively, an exhaust gas recirculation control valve of
different design could be received in a pocket in manifold 12'. A
metered exhaust gas passage 28' extends from pad 82, above exhaust
gas recirculation passage 24', above exhaust gas crossover passage
74', and under upper plenum chamber 78 to a pair of ports 84 and
86. Port 84 opens vertically into the bottom of upper plenum
chamber 78 and is centered below the associated riser passage 76.
Port 86 opens horizontally into lower plenum chamber 79. Thus
exhaust gas is recirculated through a crossover passage to heat the
induction passages and is then delivered through a control valve
assembly into the induction passages.
It will be noted that all exhaust gas recirculated to the engine is
delivered through the exhaust gas crossover passage to heat the
induction passages, and all exhaust gas delivered through the
exhaust gas crossover passage is recirculated to the engine. Thus
the exhaust gas recirculation control valve controls both the flow
of exhaust gas for heating the induction passages and the flow of
exhaust gas recirculated to the engine. This combination proves
advantageous under conditions such as wide-open throttle operation
where exhaust gas recirculation and induction passage heating
should be reduced for maximum power. It should be recognized,
however, that the advantages of this manifold structure are not
limited to a system in which all exhaust gas flowing through the
exhaust gas crossover passage is recirculated to the induction
passages.
FIG. 9 illustrates a modification of the FIG. 2 device whereby fuel
metering may be compensated for exhaust gas recirculation. The FIG.
9 device is identical to that of FIG. 2, supplemented by an
additional cam surface 86 on cam member 56. Concurrently with
movement of control valve lever 44 by cam surface 70, cam surface
86 operates a lever 88 through a cam follower 90 carried by lever
88. Lever 88 controls a unit 92 to vary an impedance which controls
fuel metering as explained below.
FIG. 10 is a schematic diagram of an electronically controlled
timed fuel injection system. As shown therein, a fuel injector 94
directs fuel into an intake manifold runner passage 80 at the back
of an inlet valve 96 for a combustion chamber 98. Injector 94 is
operated by a solenoid 100 during each cycle of the engine, and
fuel is metered by controlling the duration of time solenoid 100 is
energized to operate injector 94.
To energize solenoid 100, a signal generator 102, which nominally
may be considered as a normally open switch, provides a negative
voltage pulse during each cycle of the engine. This pulse is
differentiated by a capacitor 104 into a negative-going voltage
spike which is delivered to the base 106 of a transistor 108.
Transistor 108 thus ceases to conduct, and the voltage at its
collector 110 increases to render a transistor 112 conductive. The
voltage at the collector 114 of transistor 112 then drops and an
amplifying transistor 116 stops conducting. The voltage at the
collector 118 of transistor 116 is thereby increased, and solenoid
100 is energized to operate injector 94.
As transistor 112 starts conducting, current passes through a
primary winding 120. Primary winding 120 is coupled, through a core
122 positioned by a pressure transducer 124, with a secondary
winding 126. As current changes in primary winding 120, a voltage
is induced in secondary winding 126 which biases base 106 of
transistor 108 in a negative direction and holds transistor 108 in
a nonconductive state. Over a period of time the rate of change of
current in primary winding 120 drops, and the voltage induced in
secondary winding 126 reduces sufficiently to render transistor 108
conductive and terminate energization of solenoid 100.
In order to control the duration of time solenoid 100 is energized,
unit 92 may control the impedance in the circuit of either primary
winding 120 or secondary winding 126. Thus unit 92 could be a
potentiometer 92a which, together with resistors 128, 130 and 132,
controls the current supplied to primary winding 120. Unit 92 also
could be a switch 92b which adds a small resistor 134 to the
resistors 136, 138, and 140 controlling the bias voltage on
secondary winding 126.
As shown in FIG. 9, pressure transducer 124 is responsive to the
absolute pressure in induction passages 14 below throttles 16. It
will be appreciated that the induction manifold pressure varies
with movement of throttles 16 and with changes in engine load. In
addition, as exhaust gas recirculation valve 36 opens and exhaust
gas is recirculated to induction passages 14, the absolute pressure
in induction passages 14 increases. Manifold absolute pressure
transducer 124 then moves core 122 in to increase the inductance
between windings 120 and 126 and lengthen the time that solenoid
100 is energized. To compensate for this, the resistance of
potentiometer 92a is increased as control valve 36 opens; this
reduces the current flow through primary winding 120 to shorten the
time that solenoid 100 is energized. Alternatively, switch 92b
closes and small resistor 134 permits an increase in the bias
voltage on secondary winding 126; thus a shorter period of time is
required to render transistor 108 conductive and terminate
energization of solenoid 100.
From the foregoing it will be appreciated that fuel metering which
is responsive to induction manifold pressure may be incorrectly
proportioned to airflow when exhaust gas is recirculated to the
induction passages, and further, that such fuel metering may be
compensated for recirculation of exhaust gas by additionally
controlling fuel metering in response to the position of the
exhaust gas recirculation control valve.
* * * * *