Note: Descriptions are shown in the official language in which they were submitted.
~3377~
AIR/FUEL R~TIO CONTROLLER
This invention relates in general to a fuel
injection system. More particularly, it relates to a
mechanism for controlling the air/fuel ratio of the mixture
charge delivered to the combustion chamber of an internal
combustion engine.
This application is a division of copending
application Serial No. 331,047 filed July 3, 1979.
U.S. 3,696,798, Bishop et al, shows and describes
a combu5tion process for a fuel injection type internal
combustion engine in which the air/fuel ratio of the
mixture charge is maintained constant during engine idle
and part throttle operating conditions, for emission
control and impro~ed i~uel econc~ his constant air/fuel
ratio is maintained even though exhaust gas recirculation
(EGR) is used to control the Nx level by reducing the
maximum combustion chamber temperature and pressure.
Copending Canadian patent application Serial No.
330,961, Fuel Injection Pump Assembly, filed June 25,
1979, shows and desc~ibes a fuel injection pump having
a face cam pumping member that is contoured to provide
a fuel flow output that varies with engine speed in a
manner to match mass air flow changes over the entire
engine speed and load operating range to provide a constant
air/fuel ratio.
This invention is directed to an air/fuel
ratio controller that provides the mechanism to maintain
the constant air/fuel ratio described in connection with
the above ~wo devices regardless of changes in engine
manifold vacuum, intake manifold gas temperature, and
the flow of exhaust gases to control Nx le~Tels. Since
the addition of exhaust gases to the intake mixture charge
will decrease the oxygen conrentration of the charge
flowing to the combustion chamber, the fuel flow from
the injection pump is further modified to change as a
function of ~GR yas flow to maintain the constant air/fuel
ratio desired. The fuel pump fuel output is also modified
as a function of intake manifold gas temperature or density.
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Fuel injection pump assemblies are known that
attempt to automatically main~ain some kind of air/fuel
ratio control in response to changes in air temperature
and air pressure as well as exhaust backpressure. For
5 example, U.S. 2,486,816, Beeh, Fuel Mixture Control for
Internal Combustion Engines, shows in Figure 10 a control
system for two fuel injection pumps in which the fuel
flow output is varied as a function of changes in engine
intake manifold vacuum level, manual settings, and intake
10 temperature and exhaust pressure levels. U.S. 2,989,043,
Reggio, Fuel Control System, shows in Figure 6 a mechanical-
vacuum system in which a particular fuel/air ratio is
chosen by movement of a manual lever 78, that ratio being
maintained even though changes occur in air temperature
and manifold vacuum levels. Figure 10 shows the use
of such a system with a fuel injection pump 104.
Neither of the above devices, however, operates
to maintain the same constant air/fuel ratio over the
entire operating load range of the engine, and neither
shows any control at all for modifying the fuel output
to compensate for the addition of exhaust gases to control
NOX levels.
In accordance with the present invention,
there is provided in an air/fuel ratio controller for
use with the fuel injection system of an internal combustion
engine of the spark ignition type having an air gas induction
passage open at one end to air at ambient pressure level
and connected at its other end to an engine intake mani-
fold to be subject to manifold vacuum changes therein,
a throttle valve rotatably mounted for movement across
the air-gas induction passage to control the air-gas flow therethrough,
an exhaust gas recirculation (EGR~ passage means connecting
engine exhaust gases to the air~gas induction passage above the
closed position of the throttle valve, an EGR flow control
valve mounted in the EGR passage means for movement between
open and closed positions to control the volume of EGR
gas flow, and an engine speed responsive positive displace-
" . .
ment type fuel injection pump having a fuel flow output
to the engine that varies in direct proportion to changes
in engine speed to match fuel flow and mass airflow through the air-gas induction passage over the
entire speed and load range of the engine to maintain
the ratio of air to fuel constant, the fuel injection
pump having a fuel flow control lever selectively movable
in opposite directions to vary the fuel flow output per
cycle.
The improvement of the invention resides in
the structure of the controller which is characterized
by a mechanical linkage mechanism including a primary
lever fixed to the pump lever for concurrent movement,
an engine manifold vacuum responsive servo means, a link
connecting the servo means to the primary lever for moving
the primary lever and fuel lever to vary the fuel flow
output as a function of changes in intake manifold vacuum
indicative of changes in air flow through the induction
passage to maintain the ratio of air to fuel constant,
and a fuel enrichment control lever operably interconnected
to the EGR valve and primary lever for modifying the
movement of the primary and fuel flow levers to vary
fuel flow as a function of the addition or deletion of
EGR gases to the induction passage to compensate for
the resulting change in percentage of air flow with respect
to the total gas flow inducted to maintain a constant
air/fuel ratio.
The mechanical-vacuum linkage automatically
changes the fuel injection pump fuel output in response
to engine intake manifold vacuum changes upon opening
of the vehicle throttle valve so as to maintain a constant
air/fuel ratio, modifies the fuel output when exhaust
gases displace air in the intake charge, and modifies
the fuel output by manually overriding the constant air/fuel
ratio controlling mechanism to provide maximum enrichment
or maximum fuel output when wide open throttle accelerating
conditions of the vehicle are required.
The invention is described further, by way
~, of illustration, with reference to the accompanying
drawings, wherein:
~3~77~
Figure 1 is a schematic representation of
an internal combustion engine fuel injection system having
an air/fuel ratio controller embodying the invention;
Figures 2 and 5 are enlarged end and side
elevational views, respectively, of the air/fuel ratio
controller shown in Figure 1, with the covers removed
to expose the internal mechanism;
Figure 3 is a cross-sectional view taken on
a plane indicated by and viewed in the direction of the
arrows 3-3 of Figure 2;
Figure 3A is a schematic representation of
the linkages shown in Figure 3 isolated from the remaining
parts, for clarity;
Figure 4 is a cross~sectional view taken on
a plane indicated by and viewed in the direction of the
arrows 4-4 of Figure 2; and
Figures 6 and 7 are enlarged cross-sectional
views taken on planes indicated by and viewed in the
direction of the arrows 6-6 and 7-7 of Figures 4 and 3, respectively,
Figure 7 appearing on the same sheet of drawings as Figure ~A.
Referring to the drawings, Figure 1 illustrates
schematically a portion of the induction and exhaust
system of a fuel injection type internal combustion engine
in which is incorporated the air/fuel ~A/F) ratio controller
of this invention.
More specifically, the system includes an
air-gas intake manifold induction passage 10 that is
open at one end 12 to air at essentially atmospheric
or ambient pressure level and is connected at its opposite
end 14 to discharge through valving not shown into a
swirl type combustion chamber indicated schematically
at 16. The chamber in this case is formed in the top
of a piston 18 slidably mounted in the bore 20 of a cylinder
block 22. The chamber has a pair of spark plugs 24
for the ignition of the intake mixture charge from the
induction passage 14 and the fuel injected from an injector
26 providing a locally rich mixture and overall lean
cylinder charge. An exhaust gas conduit 28 is connected
to a passage 30 that recirculates a portion of the exhaust
~377~
gases past an EGR valve 32 -to a point near the inlet
to the induction passage 10 and above the closed position
of a conventional throt-tle valve 34. Thus, movement
of the throttle valve 34 provides the total control of
the mass flow of gas (air plus EGR) into the engine cylinder.
The EGR valve 32 is rotatable by a servo mechanism 36
connected by means not shown to -the throttle valve 34
to provide a flow of exhaust gases during the load conditions
of operation of the engine.
The fuel in this case delivered to injector
26 is provided by a fuel injection pump 38 of the plunger
type shown and described more fully in copending Canadian
application Serial No. 330,961 referred to above. The
details of construction and operation of the pump are
fully described in the above Serial No. 330,961 and,
therefore, are not repeated since they are believed to
be unnecessary for an understanding of the invention.
Suffice it to say, however, that the pump has a cam face
40 that is contoured to match fuel pump output with the
mass air flow characteristics of the engine for all engine
speed and load conditions of operation so as to maintain
a constant base air/fuel ratio to the mixture charge
flowing into the engine combustion chamber 16 at all
times. The pump has an axially movable fuel metering
sleeve valve helix 42 that cooperates with a spill port
44 to block the same at times for a predetermined duration
to thereby permit the output from the plunger 4S of the
pump to build up a pressure against a delivery valve
48 to open the same and supply fuel to the injector 26.
Axial movement of the heliX by a fuel control lever 50
will vary the base fuel flow output hy moving the helix
to bloc~ or unblock a spill port 44 for a greater or
- lesser period of time.
This invention is directed to an air/fuel
ratio controller that is connected to the fuel pump lever
50 to change the fuel flow output as a function of manifold
vacuum changes (air flow changes) upon opening of the
throttle valve 34 so that the air/fuel ratio of the mixture
charge flowing to the engine cylinder will remain constant.
~337~
The controller also modifies the fuel flow upon the addi~ion
of EGR gases to the intake charge and upon changes in
the temperature of the intake charge, each of which
again changes the oxygen concentration in the charge.
The controller is illustrated generally in
Figure 1 at 52. It contains a vacuum-mechanical linkage
mechanism that is illustrated more particularly in Figures
2-7. The controller contains a fuel control lever 54
that is fixed to the fuel injection pump fuel lever 50
for ~oncurrent movement. It also has a fuel flow output
- control link 56 that is connected to an aneroid 58 to
be responsive to intake manifold vacuum changes, and
a fuel enrichment linkage or fuel ratio changing linkage
60 that moves in response to the flow of EGR gases and
changes in intake manifold gas temperature to modify
the movement of the fuel control link 56 and fuel lever
54 to maintain the constant air/fuel ratio desired.
~ ore specifically, Figure 3 shows on an enlarged
scale a side elevational view of the controller 52 with
the side cover 70 (Figure 2) removed for clarity. The
body 72 of the controller contains a number of cavities
within which is pivotally mounted a shaft 74 on which
the fuel control lever 54 is fixed. Lever 54 is a right
angled bellcrank, each leg 76,78 of which contains an
elongated cam slot or yoke 8P,82 receiving therein, respec-
tively, floating rollers 84,86. Referring to Figure
1, the roller 84 is received within the yoke 88 to which
lever 50 is attached so that arcuate pivotal movement
of leg 76 of lever 54 in either direction causes an axial
movement of the helix 42 on the metering sleeve of the
pump to change the fuel flow output level or rate of
flow.
The floating roller 86 (Figures 3 and 7) is
also received within the elongated slots or yokes 90,92
provided, respectively, in yoke members 94 and 96. Yoke
member 94 is formed as an extension of a rod 98 fixed
to the aneroid 58 movable within a sealed chamber 102.
The aneroid 58 conslsts of an annular expandable metallic
bellows that is sealed with a vacuum inside. A spring
~33~74
lV~ 7
lt~ biases a pair of supports 104 apart to prevent the
complete collapse of the bellows from outside pressure
in chamber 102. The chamber is connected by a fitting
106 to a line 108 opening into the intake manifold at
; 5 110 in Figure 1. Thus, changes in engine intake manifold
vacuum will be reflected by the contraction or expansion
of the bellows 58 causing a linear movement of the rod
9~ and a vertical (as seen in Figure 3) movement of roller
86 in the slot 90 in a direction at right angles to the
axis of movement of the rod 98. This causes an arcuate
camming of the fuel control lever 54 by the roller 86
moving in the cam slot 82.
The other yoke member 96 in Figure 3 is mounted
for a sliding movement on a shaft 112 that is non-rotatably
fixed at opposite ends in the housing 72. The yoke member
96 slides along the shaft 112 in a direction at right
angles to the longitudinal axis of cam slot 92 and to
the direction of movement of the floating roller 86.
This movement of roller 86 again causes an arcuate ~ovement
of the fuel control ~ever leg 78 to rotate shaft 74 and
axially move the fuel metering sleeve helix 42 shown
in Figure 1 to change the fuel output flow level or rate
of flow.
It will be seen that the floating roller 86
can be moved either separately by the intake manifold
vacuum changes moving rod 9~, or as will herein~fter
be described, by movement of the ratio changing member
96 in response to changes in the intake manifold gas
temperature or the flow of EGR gases to compensate for
the change in percentage of air to the total mass air
flow. These movements are indicated more clearly in
Figure 3~ wherein the uel control lever 54 and two yoke
members 94, 96 are isolated and their movements indicated
to show the mechanical advantages and linear movements
providing the arcuate movement of fuel control lever
54.
Figure 4 shows the air/fuel ratio changing
. mechanism that modifies the fuel output level dictated
by the manifold vacuum control mechanism shown in Figure
~13377~
3 to compensate for changes in intake manifold gas temperature
and the flow of EGR gases. If the density of the air
changes, the ~eight of the air intake charge will also
change and, therefore, the air/fuel ratio would change
were not means provided to correct for this. Similarly,
the addition or deletion of EGR gases to the mass air
flow will change the oxygen concentration so that the
fuel flow need be changed to maintain the air/fuel ratio
constant.
The yoke member 96 shown in Figure 3 that
is slidably mounted on shaft 112 has pivotally pinned
to it at 114 a lever or link 116 having an elongated
cam slot or yoke 118. Slidably mounted within the slot
is afloating roller 120 pivotally secured to the yoke
end (Figure 6) of a fuel enrichment lever 122. Lever
122 is pivotally mounted on a shaft 124 that is rotatably
mounted in the housing 72 and, as seen in Figure 2, extends
out from the housing for attachment to an actuating lever
126. An arm 128 extends from the enrichment lever in
Figure 4 for engagement with a screw 130 adjustably mounted
in the housing, for a purpose to be described later.
Lever 126 in this case is connected by linkage
not shown to the EGR valve 32 in Figure 1 such that closing
of the EGR valve 32 will result in a counter-clockwise
movement or rotation of the lever 126, shaft 124 and
enrichment lever 122 to pivot lever 116 in a counter-
clockwise direction about a pivot fulcrum 132. This
will result in an upward (as seen in Figure 5~ movement
of yoke member 96 and, therefore, as seen in Figure 3,
a clockwise rotation of full control lever 54. As best
seen in Figures 3A and 1, this will increase the fuel
flow proportional to the percentage increase of air that
now displaces the EGR gas flow that has been shut off,
to maintain a constant air/fuel ratio.
Conversely, a decrease in fuel flow will occur
when the EGR valve is opened, to compensate for the displace-
ment of air in the intake charge by EGR gases.
The bellcrank lever 116 is adapted to pivot
about fuIcrum 132 that floats in response to changes
~337~
in intake manifold gas temperature. More particularly,
the fulcrum 132 consists of a pin pivotally connecting
one end of a link 134 to lever 116 and in tu~n pivotally
connected to one leg of a bellcrank lever 136 rotatably
5 mounted on a shaft 138 fixed in the housing of the con-
troller. The opposite leg of the bellcrank slidably
mounts an adjustable rod l~9 having a spherical end 140.
The latter provides a universal abutment with a pad end
142 of an adjustably mounted rod 144. The rod threadedly
lO projects from within a sleeve extension 146 of an annular
flexible metallic bellows 148.
The bellows 148 is sealed and filled with
a liquid that has a high thermal rate of expansion. An
extension 152 of the bellows anchors one end of a spring
15 154, the other end being secured to the bellows extension
146. A bulb 156 projects from the interior of the bellows
ts contir~uously subject the liquid in the bellows to
the te~perature Of the intake manifold gas charge admitted
into and surrounding this portion of the housing. The
20 spring 154 maintains the bellows under compression prevent-
ing vapor formation. Figure 4 further shows a first
spring 158 anchored to the housing and attached to a
fitting 160 projecting from lever 134 to maintain the
bellcrank spherical engagement portion 140 against the
25 pad 142 of the temperature sensitive bellows e~tension.
A second spring 166 is hooked between the housing and
the fuel enrichment lever 122 to maintain the lever against
the adjustable stop 130.
Figure 5 is a side elevational view of the
30 mechanism with the cover removed and indicates the overlying
relationship of the parts shown in Figure 2. In Figure
5, a lever 170 is fixed on the fuel control lever shaft
74 for engagement with an indicator shaft 172 slidably
mounted to project through the housing 72 (Figure 2).
35 The rod 172 forms part of a gauge 174 that indi~ates
the fuel flow per cycle. A spring 176 lightly loads
the lever 170 to eliminate some of the lash in the linkage.
In operation, the movement of the fuel injection
pump fuel lever 50 and the metering sleeve helix 42 are
~337t7~
controlled to maintain the ratio of air to fuel of the
intake charge flowing to the combustion chambers of the
engine co~stant at all engine speeds and loads, and this
is achieved by varying the fuel flow output as a function
of intake manifold vacuum changes and by modifying those
changes in response to changes in density of the intake
manifold gas by virtue of changes in the gas temperature
and by changes of volume of flow of exhaus~ gases upon
operation of the exhaust gas recirculation system.
Figure 3A illustrates more clearly the movement
of the pump fuel metering sleeve helix (connected to
84) in response to changes in manifold vacuum and changes
in intake gas temperature and the flow of EGR gases.
To maintain constant intake gas to fuel ratio, the fuel flow
must be directly proportional to manifold absolute pressure
and inversely proportional to manifold absolute temperature.
The geometry of the mechanism is such that the metering
sleeve travel is directly proportional to the aneroid
capsule travel and inversely proportional to tne temperature
compensator travel. -When the throttle valve 34 is positioned
closed as shown in Figure l, the engine will be conditioned
for idle speed operation permitting only sufficient mass
gas flow (air plus EGR) into the engine to maintain the
desired speed level. Although not shown, an interconnection
between the EGR valve and throttle valve would be provided
to establish a predetermined schedule of :flow of EGR
gases and an opening of the EGR valve for each position
of the throttle valve 3~ from its closed position to
a wide open throttle (WOT) position. As stated in U.S.
3,697,798, under WOT operating conditions, maximum power
is determined by the availability of oxygen to the combustion
chamber~ Therefore, at WOT, no EGR flow is desired.
At idle, some EGR flow may be desired and scheduled.
Accordingly, since the throttle valve 34 controls the
total intake through the induction passage 10, the greater
the amount of EGR gas flow for the same total mass flow,
the more the fuel pump lever 50 need be moved to decrease
fuel flow to maintain a constant air/fuel ratio. In
Figure 3A, this is accomplished by the manifold vacuum
~3377~
11
prevalent fox the particuIar position of the throttle
valve effecting a movement of the cross slide yoke 94
linearly and at right angles to the movement of the cross
slide yoke 96 whose position is attained in accordance
with the volume of EGR gas flow and manifold temperature
to rotate the fuel control lever 54 accordingly to prede-
termine the fuel flow output from the pump to maintain
the constant air/fuel ratio. The aneroid movable rod
98 secured to yoke 94 will move the floating roller 86
leftwardly as seen in Fig~re 3A as the manifold pressure increases
upon gradual opening of the throttle valve to increase
the fuel flow in proportion to the increase in air flow.
If the EGR flow remains constant, no other changes will
be made. However, a change in EGR flow upon opening
of the throttle valve causes a corresponding movement
of slide yoke 96 to further cause roller 86 to pivot
the fuel control lever to change fuel flow.
It will be clear, of coursel that each of
the linkage mechanisms is fully adjustable so as to fine
tune the movements and lengths of the linkages to provide
different operating characteristics of each controller
and to match each controller for different pumps having
different operating characteristics and different manufactur-
ing tolerances. For example, the geometry of the mechanism
is chosen so that the theoretical zero fuel flow position
of the fuel injection pum~ metering sleeve helix 42 is
coincident with the threoretical zero manifold pressure
position of the yoke 94, and the temperature scale is
such that the th~oretical zero absolute temperature position
o~ the yoke 96 coincides with the center of the shaft
74 so that fuel flow will vary as a direct proportion
of changes in manifold absolute pressure and inversely
with changes in manifold absolute temperature. The fixed
position of the fuel enrichment control lever 60 in Figure
4 will detexmine the initial air/fuel ratio. This can
be varied by adjustment of the screw 130 to obtain any
air/fuel ra~io desired.
For intake manifold gas temperature adjustments,
screwing of the rod 139 in or out of the bellcrank 136
~L~3377~
12
and screwing of the pad 142 into and out of the extension
146 will provide an infinite number of changes with respect
to the initial settings.
- One additional feature of the invention is
the ability of the operator to manually enrichen the
air/f~el mixture charge for maximum acceleration such
as during the WOT operation. While not shown, the fuel
enrichment control lever 122 in-Figure ~ would be inter-
connected with the EGR valve in such a manner that when
the EGR valve is closed or indicates a zero EGR rate,
manual rotation of the enrichment lever 122 beyond this
position in a counter-clockwise direction as seen in
Figure 4 will give greater fuel output.
From the foregoing, it will be seen that the
invention provides a mechanism that maintains the air/fuel
ratio of thé intake mixture charge to the engine constant
regardless of variations in the intake manifold vacuum
or pressure, temperature, or EGR rate. ~t the same time,
the driver retains the option to enrich the mixture manually
whenever it is necessary for maximum acceleration.
While the invention has been illustrated and
described in its preferred embodiment, it will be clear
to those skilled in the arts to which it pertains that
many chan~es and modifications may be made ther~to without
departing from the scope of the invention.
