U.S. patent number 3,896,777 [Application Number 05/391,533] was granted by the patent office on 1975-07-29 for exhaust gas recirculation control device.
This patent grant is currently assigned to Nissan Motor Company Limited. Invention is credited to Kenji Masaki, Shuya Nambu.
United States Patent |
3,896,777 |
Masaki , et al. |
July 29, 1975 |
Exhaust gas recirculation control device
Abstract
A device which modulates intake manifold vacuum with venturi
vacuum to actuate an exhaust gas recirculation control valve.
Inventors: |
Masaki; Kenji (Yokohama,
JA), Nambu; Shuya (Yokohama, JA) |
Assignee: |
Nissan Motor Company Limited
(Yokohama, JA)
|
Family
ID: |
13894479 |
Appl.
No.: |
05/391,533 |
Filed: |
August 27, 1973 |
Foreign Application Priority Data
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|
|
|
|
Aug 31, 1972 [JA] |
|
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47-86711 |
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Current U.S.
Class: |
123/676 |
Current CPC
Class: |
F02M
26/56 (20160201) |
Current International
Class: |
F02M
25/07 (20060101); F02m 025/06 () |
Field of
Search: |
;123/119A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Richter; Sheldon
Claims
What is claimed is:
1. In an exhaust gas recirculation system having a recirculation
conduit to recirculate a portion of exhaust gases from the exhaust
system of an internal combustion engine to the intake system
thereof having a carburetor, a vacuum actuated exhaust gas flow
metering valve normally closing the recirculation conduit; a
diaphragm device operatively connected to the metering valve and a
vacuum conduit connecting the spring loaded side of said diaphragm
device to the intake manifold for actuation of the diaphragm device
by the intake manifold vacuum to operate the metering valve, a
modulating device comprising a casing interposed in and having a
chamber forming part of said vacuum conduit, said chamber having an
air bleed port opening to the atmosphere; an air bleed valve for
closing said air bleed port; a spring loaded diaphragm having its
spring loaded side connected to the venturi of the carburetor and
the opposite side connected to the exhaust system, said spring
loaded diaphragm being operatively connected to said air bleed
valve such that said air bleed valve is urged toward such air bleed
port to decrease air flow through said air bleed port as the
magnitude of the venturi vacuum increases.
Description
The present invention relates to an exhaust gas recirculation
system for an internal combustion engine, and more particularly to
a modulating device for an intake manifold vacuum actuated exhaust
gas flow control valve for an exhaust gas recirculation system for
an internal combustion engine.
Heretofore, there have been many proposals to introduce, throughout
all operating conditions of an internal combustion engine, an inert
gas such as exhaust gas into the intake system; i.e. into the
intake manifold or into the induction passage at a location
downstream of the air filter; with the intention of reducing the
concentration of nitrogen oxides (No.sub.x) in the engine exhaust
gases by suppressing their formation. It is required that a
suitable amount of exhaust gas be introduced into the intake system
of the engine to attain satisfactory results. A reduction in engine
performance results if the ratio of the flow rate of recirculated
exhaust gas to that of intake air exceeds a certain optimum value,
and failure to suppress the formation of nitrogen oxides results if
the ratio is much smaller than the certain optimum value. If intake
manifold vacuum is employed to actuate a valve to meter the flow of
exhaust gas into the intake system of the engine, as is common in
the prior art, it is hardly possible to maintain the flow rate
ratio of recirculated exhaust gas to intake air at an optimum value
mostly due to the fact that the vacuum in the intake manifold does
not vary in proportion to the intake air flow rate throughout
operation of the engine.
It has been confirmed that the vacuum in the venturi of a
carburator varies in relation to the velocity of air flowing
through the venturi throughout operation of the engine, and
therefore in relation to the flow rate intake air being introduced
into the engine. Thus, if the vacuum in the venturi is employed as
a parameter in controlling the amount of exhaust gas introduced
into the intake system, the flow rate of exhaust gas can be metered
to an optimum ratio to that of intake air throughout all modes of
operation of the engine. However, the vacuum in the venturi is
insufficient for adequate control of a vacuum actuated valve to
meter the flow rate of recirculated exhaust gas.
It is accordingly a primary object of the present invention to
provide a modulating device for a vacuum actuated valve of an
exhaust gas recirculation system for an internal combustion engine,
by which a suitable amount of exhaust gas can be introduced into
the intake system throughout the operation of the engine.
It is another object of the present invention to employ, as a
parameter, the vacuum in the venturi of a carburetor of an engine
for controlling the amount of exhaust gas introduced into the
intake system so that the flow rate of recirculated exhaust gas
will vary in accordance with that of intake air.
These and other objects, features and advantages of the present
invention will become clear as this description progresses with
reference to the accompanying drawings, wherein:
FIG. 1 shows an exhaust gas recirculation system incorporating a
modulating device according to one embodiment of the present
invention;
FIG. 2 shows a modulating device according to another embodiment of
the present invention;
FIG. 3 shows a modulating device according to still another
embodiment of the present invention; and
FIG. 4 shows a modulating device according to still a further
embodiment of the present invention.
Referring to FIG. 1, an exhaust gas recirculation system
incorporating a modulating device of the present invention is shown
as incorporated into an internal combustion engine which may be any
conventional design, being provided with a usual carburetor 10,
intake manifold 12, and exhaust pipe 14 leading from an exhaust
manifold (not shown). The carburetor 10 is provided with a choke
valve 16, venturi section 18 and throttle valve 20.
The exhaust gas recirculation system includes an exhaust gas
recirculation conduit 22 connecting the exhaust pipe 14 with the
intake manifold 12 to recirculate a portion of the engine exhaust
gas to the intake manifold 12. Provided in the recirculation
conduit 22 is a normally closed metering valve 26 to control the
amount of exhaust gas recirculated to the intake manifold 12
through the recirculation conduit 22. The metering valve 26 has a
valve stem 28 which at its upper end is secured to a plunger 30
which in turn is fastened at its upper end to the center of a
diaphragm 32 of a diaphragm device generally designated as 34. The
diaphragm 32 is disposed in a casing 36 secured to the
recirculation conduit 22. A spring 38 biases the diaphragm 32
downwardly as shown. A chamber 24 above the diaphragm 32 is
connected by a conduit 40 to the intake manifold 12. A chamber
below the diaphragm 32 (no numeral) is open to the atmosphere
through a plurality of apertures, one being shown and designated as
42.
A modulating device 44 according to the present invention is
interposed in the conduit 40. A portion (no numeral) of the conduit
40 leading from the intake manifold 12 opens into a first chamber
46 of a casing 62 of the modulating device 44. A partition 48
devides the interior of the casing 62 into the first chamber 46 and
a second chamber 47. A valve 54 is disposed in the partition 48 to
control communication between the chambers 46 and 47. A stem 56 of
the valve 54 is operatively attached to a movable end portion 58 of
a pressure responsive membrane means which is shown as being a
bellows 60, the other end portion (no numeral) of the bellows 60
being fixed to the bottom of the chamber 47 as shown. A port 52
vents the chamber 47 to the atmosphere. A first conduit 64 connects
the interior of the bellows 60 through a hole (no numeral) in the
casing 62 to the venturi section 18. A restriction 66 is provided
in the conduit 40 as shown to limit gas flow therethrough.
The device of FIG. 1 operates as follows:
During operation of the engine, the velocity of air flowing through
the venturi section 18 and accordingly the level of vacuum therein
increase as the throttle valve 20 opens. This increase of vacuum
level in the venturi section 18 causes the bellows 60 to collapse,
moving the valve 54 downwardly to reduce the air flow into the
chamber 46 above the partition 48 through the port 52 and chamber
47. Thus, the pressure in the chamber 46 approaches the vacuum
level in the intake manifold 12 as the vacuum in the venturi
section 18 increases, and decreases as the vacuum in the venturi
section 18 decreases. Since the chamber 24 above the diaphragm 36
of the diaphragm device 34 communicates with the chamber 46 through
the conduit 40, the valve 26 will be actuated in respense to the
vacuum level in the chamber 46, thereby allowing a suitable
quantity of exhaust gas to flow through the valve 26 into the
intake manifold 12.
FIG. 2 shows an improved embodiment of a control device of the
present invention.
In the embodiment of FIG. 1, the valve 26 may fully open during a
warming-up operation of the automobile in cold weather, at which
time the choke valve 16 is nearly closed (see the phantom position
of the choke valve 16 in FIG. 1), thereby creating a relatively
high vacuum in the venturi 18 to cause the valve 54 to fully close.
Thus, a relatively large amount of exhaust gas will be introduced
into the intake manifold 12 relative to the amount of intake air
introduced thereinto to impair the drivability of the automobile
during the warming-up operation. To eliminate this condition, FIG.
2 shows an improved control device which can be applied in the
exhaust gas recirculation system of FIG. 1.
A modulating device of FIG. 2 is indicated generally as 44a. The
portion of the pipe 40 leading to the diaphragm device 34 opens
into a first chamber 46a of a casing 62a, which is vented to the
atmosphere through a restricted port 52a. A valve 54a is disposed
in a first portition 48a and controls communication therethrough
between the first chamber 46a and a second chamber 47a. The chamber
47a communicates with the intake manifold 12 through the other
portion of the conduit 40. A valve stem 56a of the valve 54a passes
through a second partition 68 in a gas tight manner, and is
connected at its bottom end as shown to a diaphragm 58a. The
diaphragm 58a divides the space in the casing 62a below the
partition 68 into an upper (as shown) or third chamber 61 and a
lower (as shown) or fourth chamber 63. The chamber 61 is vented to
the atmosphere through at least one aperture 65. A spring 70
disposed in the chamber 63 biases the diaphragm 58a upwards as
shown and thus the valve 54a to a closed position. The chamber 63
communicates with the venturi section 18 through the conduit
64.
The device of FIG. 2 operates as follows:
As the vacuum in the venturi section 18 increases, the vacuum in
the chamber 63 increases accordingly, so that the pressure
difference across the diaphragm 58a counteracts the action of the
spring 70 and causes the valve 54a to open. However, since the
chamber 46a is open to the atmosphere and the spring 70 biases the
valve 54a upwardly toward a closed position, the vacuum from the
intake manifold 12 in the chamber 46a can be modulated even during
a warming-up operation of the automobile, thus preventing an
excessive amount of exhaust gas from flowing through the valve 26
provided in the exhaust gas recirculation conduit 22.
FIG. 3 shows another embodiment of the present invention.
During operation of an automobile, there may occur a condition such
that the vacuum in the intake manifold 12 varies in dependence on
the engine speed at different intake air flow rates depending on
the engine loading. Thus, it may be necessary to adjust the air
flow into the chamber 46 (of FIG. 1) so that the vacuum applied to
the chamber 24 above the diaphragm 32 of the diaphragm device 34
may vary in relation to the flow rate of intake air under such a
condition. For this purpose, FIG. 3 shows an exhaust gas
recirculation system analogous to that of FIG. 1 but includes
instead of the modulating device 44 of FIG. 1 a modulating device
44b interposed in the conduit 40. In this embodiment, a first
chamber 46b of a casing 62b communicates with the upper chamber 24
of the diaphragm device 34 and the intake manifold 12 through
respective portions of the conduit 40, and also with the atmosphere
through a port 52b. A partition 68b divides the interior of the
casing 62b into the first chamber 46a and a second chamber 47b. A
valve 54b is disposed in the casing 62b to control communication
between the chamber 46b and the atmosphere through the port 52b. A
valve stem 56b of the valve 54b passes through partition 68b in a
gas tight manner, and is attached to a movable end portion 58b of a
bellows 60b disposed in the chamber 47b in a manner described with
reference to FIG. 1. The interior of the bellows 60b communicates
with the intake manifold 12 through a second conduit 72, and the
chamber 47b communicates with the venturi section 18 through a
first conduit 64b.
The device of FIG. 3 operates as follows:
During operation of the automobile, as the throttle valve 20 is
gradually opened, the vacuum in the venturi section 18 increases.
This increase in the vacuum in the venturi section 18 causes the
bellows 60b to expand and the valve 54b to move upwardly toward a
closed position. Thus, the vacuum in the chamber 24 above the
diaphragm 32 of the diaphragm device 34 increases, thereby
increasing the amount of exhaust gas being introduced into the
intake manifold 12. Where, however, the vacuum in the intake
manifold 12 increases whereas the vacuum in the venturi section 18
remains unchanged, the valve 54b moves downwardly toward an open
position. It is now seen that in the device of FIG. 3, the vacuum
in the chamber 24 above the diaphragm 32 of the diaphragm device 34
can be prevented from increasing excessively so that the amount of
exhaust gas being introduced into the intake manifold 12 under such
a condition that the vacuum in the intake manifold 12 increases but
the vacuum in the venturi section 18 remains unchanged does not
undesirably increase.
FIG. 4 shows still another embodiment of a control device of the
present invention.
A modulating device of FIG. 4 now designated generally as 44c
employed the exhaust gas recirculation system of FIG. 1 includes a
first chamber 46c a second chamber 47c, and a third chamber 49c
communicating as shown. A valve 54c controls communication between
the chamber 46c and the atmosphere through a port 52c, and has a
valve stem 56c passing through a partition 68c in a gas tight
manner and connected to a diaphragm 58c. A spring 70c biases the
diaphragm downwardly as shown and the valve 54c toward an open
position. In this embodiment the chamber 49c is connected to the
exhaust pipe 14 through a third conduit 74.
The device of FIG. 4 operates as follows:
During operation of the automobile, as the vacuum in the venturi
section 18 increases, the valve 54c will move toward a closed
position to block the port 52c. If the vacuum in the intake
manifold 12 increases while the vacuum in the venturi section 18
remains unchanged, the valve 54c will move further downwardly to
increase the degree of opening of the valve 54c and port 52c due to
the pressure in the exhaust pipe 14, because the pressure in the
exhaust pipe 14 decreases as the vacuum in the intake manifold 12
increases. If, on the other hand, the vacuum in the intake manifold
12 decreases, as when the throttle valve 20 is opened wider, the
valve 54c moves further upwardly to block the port 52c due to the
pressure in the exhaust pipe 14 because the pressure in the exhaust
pipe 14 increases as the vacuum in the intake manifold 12
decreases.
In this way, in the control device of FIG. 4, the vacuum in the
chamber 24 above the diaphragm 32 of the diaphragm device 34 can be
controlled in response to the magnitude of the vacuum in the
venturi section 18.
* * * * *