U.S. patent number 3,835,827 [Application Number 05/327,280] was granted by the patent office on 1974-09-17 for exhaust and gas recirculating system.
This patent grant is currently assigned to Ford Motor Company. Invention is credited to James H. Wolgemuth.
United States Patent |
3,835,827 |
Wolgemuth |
September 17, 1974 |
EXHAUST AND GAS RECIRCULATING SYSTEM
Abstract
An exhaust gas recirculation system is disclosed employing a
primary control valve having a vacuum operated servo mechanism for
controlling the admission of recirculating gases. The servo
mechanism is operated in response to a modulated vacuum signal
derived principally from intake manifold vacuum. Modulation of the
vacuum signal is achieved by three control means connected in
series, one of which functions in response to a differential
between carbureted venturi vacuum and the intake manifold vacuum,
another control means operates to prevent communication of the
vacuum signal to the servo mechanism during prolonged steady or
nearly steady conditions of the engine, yet another control means
is effective to prevent communication of the vacuum signal during
wide-open throttle conditions of the engine carburetor.
Inventors: |
Wolgemuth; James H. (Warren,
MI) |
Assignee: |
Ford Motor Company (Dearborn,
MI)
|
Family
ID: |
23275902 |
Appl.
No.: |
05/327,280 |
Filed: |
January 29, 1973 |
Current U.S.
Class: |
123/568.29 |
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: Burns; Wendell E.
Attorney, Agent or Firm: Malleck; Joseph W. Zerschling;
Keith L.
Claims
I claim:
1. In an engine having an exhaust manifold, an intake system for
inducting air and fuel through a metering venturi into an intake
manifold of said engine, an apparatus for recirculating exhaust
gases comprising:
a. a duct connecting said intake system and exhaust manifold,
b. valve means interposed in said duct having a first control
element normally biased to a closed position and a servo mechanism
operable to overcome said bias for variably opening said valve
means, said servo mechanism being connected to vacuum from said
intake system, and
c. first control means to modulate the connection of vacuum between
said intake system and servo mechanism in accordance with pressure
at said metering venturi, said first control means being movable in
response to a differential pressure between intake manifold vacuum
and venturi vacuum to modulate and limit the degree of intake
system vacuum communicated to said servo mechanism, said first
control means comprising a housing having a bore with stepped
portions, a spool valve provided with differential lands slidable
in respectively stepped portions of said bore, said bore having an
inlet opening in communication with said servo mechanism and an
outlet opening in communication with intake manifold vacuum, said
outlet opening being arranged so as to be opened or closed by
operable movement of said spool valve, the larger of said lands
being subject to a force on one side thereof proportional to intake
system air-flow vacuum tending to move said spool valve to an open
position about said outlet opening and the other side of said
larger land being subject to the intake manifold vacuum tending to
urge said spool valve to a close position.
2. The apparatus as in claim 1, in which an accumulator is employed
to maintain a predetermined level of intake manifold vacuum for
introduction to said first control means during all conditions of
operation except when said first control means is closed.
3. The apparatus as in claim 1, in which the smaller land is
subjected to intake manifold vacuum urging said first control means
to an open position and thereby maintaining a constant relationship
between exhaust gas recirculation and intake system air-flow vacuum
even during the closed position of said spool valve.
4. The apparatus as in claim 1, comprising in combination a third
control means effective to prevent communication of said intake
manifold vacuum with said servo mechanism during prolonged steady
state cruising conditions of said engine.
5. The apparatus as in claim 1, in which said bias for said servo
mechanism is calibrated to provide closure of said valve means at
the highest vacuum encountered at wide-open throttle for said
engine and said bias being adapted to meter a small amount of
exhaust gas recirculation during throttle positions substantially
adjacent to wide-open throttle.
6. The apparatus as in claim 1, in which there is further provided
additional control means for controlling the communication of
manifold intake vacuum to said servo mechanism, said additional
control means being adapted to prevent communication of intake
manifold vacuum to said servo mechanism during steady-state
conditions of said carburetor air flow.
7. The apparatus as in claim 6, in which said additional control
means comprises a housing having a bore with an inlet thereto in
communication with said servo mechanism and an outlet thereof in
communication with the inlet to said first control means, a valve
element therein normally biased in a closed position preventing
flow between said inlet and outlet and a land connecting with said
element having opposite sides thereof normally subjected to intake
manifold vacuum, and means for delaying the relief of intake
manifold vacuum from either side of said land upon a change of
intake manifold vacuum so that one side of said land will be
effective to overcome said bias and open said second control means
according to said predetermined delay.
Description
BACKGROUND OF THE INVENTION
Numerous systems have been devised to recycle exhaust gases into
the air/fuel induction system of an automotive engine for a variety
of purposes among which include:
A. use of the exhaust gases to prewarm and thereby vaporize the
incoming air/fuel mixture to facilitate its complete combustion in
the combustion zone,
B. recirculation of the exhaust gases to reuse unignited or
partially burned portions of the fuel which would otherwise pass
out into the exhaust pipe and into the atmosphere, and
C. recirculate exhaust gases for the purpose of reducing oxides of
nitrogen emitted from the exhaust system and into the atmosphere.
This is brought about by reducing the maximum combustion
temperature in consequence of the dilution of the air/fuel mixture
by the recycling of exhaust gases.
However, since the load and power demands of the engine change
rather considerably over their normal operation, the above goals
cannot be easily achieved if consideration is given to driveability
and satisfactory engine performance. To this end, the invention is
concerned with utilizing control signals which vary the volume and
timing of exhaust gas recirculated in conformity with achieving
more goals. It is known that the recycling of at least 5 percent
and not more than 25 percent of the total exhaust gases through the
engines, depending upon the load or power demand, will reduce the
combustion temperature to less than 2,200.degree.F. But within this
range, the amount recycled at any one moment must be tuned to a
variety of engine conditions.
SUMMARY OF THE INVENTION
The primary object of this invention is to provide an exhaust gas
recirculation system capable of introducing exhaust gases to the
intake manifold system during periods when exhaust gas
recirculation will not substantially hinder the normal power
operation of the engine and in such modulated quantities that best
suit the attainment of lower emissions. To this end, the invention
contemplates the control or admission of exhaust gas recirculation
in response to a vacuum signal, the signal being modulated
primarily in proportion to carburetor venturi vacuum. On and off
controls are additionally superimposed over this primary modulation
by use of (a) a valve adapted to close on a delayed basis in
response to a change in intake manifold vacuum and to remain closed
during steady state manifold vacuum conditions, and (b) a valve is
adapted to close when wide-open throttle conditions are
substantially reached.
One or more combinations of the above controls provide a sensitive
variation of exhaust gas recirculation more in tune with the
multiple needs of the engine for top performance as well as the
emissions criteria.
To provide a constant relationship between recirculation and
carbureted air flow, an admitting valve may be contoured to provide
a flow area through the throat of the admitting valve which is
proportional to the one half power of the modulated vacuum signal;
the modulated vacuum signal in turn may be related to venturi
vacuum which increases at a rate equal to the second power of the
air-flow through the carburetor.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic illustration of the exhaust gas
recirculation system used in conjunction with a typical internal
combustion engine.
DETAILED DESCRIPTION
Referring now to FIG. 1, a preferred embodiment is illustrated
comprising, broadly, an exhaust gas recirculation system adapted to
operate with a typical engine having an intake system A and an
exhaust manifold B, the intake system further comprising a
carburetor having a typical air horn 9 provided with a metering
venturi 10 for inducting fuel (not shown) in response to the vacuum
created by said metering venturi. A throttle 8 is employed to
conventionally control the flow of the fuel and air mixture passing
into intake manifold 11 of the engine.
Exhaust gas recirculation is conveyed by a duct or passages C
interconnecting the exhaust manifold with the intake manifold;
primary valve means D is effective to control the admission of
exhaust gases through said duct C. Valve means D is operated in
response to a servo mechanism E which has a control element or
diaphragm 23 normally biased in one direction to close valve means
D and is subject to a modulated vacuum signal to overcome the
effect of said bias for opening said valve means. Modulation of
said vacuum signal is achieved through a series of control means H,
G and F. Means H is effective to control the communication of
intake manifold vacuum with the servo mechanism in response to a
differential between intake system vacuum obtained at the metering
venturi 10 and intake manifold vacuum. Control means F is effective
to interrupt normal communication of the modulated vacuum signal to
said servo mechanism in response to wide-open throttle conditions
of said carburetor. Means G is effective to prevent communication
of the modulated vacuum signal with said servo mechanism during
prolonged steady state cruising conditions of the engine.
Turning now in more particularity to the components of the system,
primary valve means D comprises a rigid valve housing 7 having a
cylindrical bore or wall 17 subdivided therein longitudinally into
chamber portions 18, 19, 26 and 27 by the respective interposition
of flat walls 16, 22 and a diaphragm 23 (forming a control
element), all extending transversely across the bore at spaced
locations. The wall 16 has an opening 15 therein defining a valve
seat; a valve element 14 is movable between opened and closed
positions (shown in the semi-open position in FIG. 1) for said
valve seat. The valve element 14 is carried by a valve stem 25
connected with said flexible diaphragm 23 for movement therewith.
Inlet 21 chamber portion 18 provides for introducing exhaust gases
via conduit 12 from said exhaust manifold; outlet 20 from chamber
portion 19 is provided for communicating with the intake manifold
11 of said intake system by way of a conduit 13 connecting with a
port 92 positioned below the carburetor throttle 8.
The servo-mechanism E utilizes a helical spring 24 to bias
diaphragm 23 in a direction to bring valve element 14 to a closed
position; spring 24 acts between the right hand side of wall 22 and
the left hand side of diaphragm 23. A passage 29 is provided to
communicate chamber portion 26 with the control vacuum signal
conveyed from means F, G and H, means H communicating directly with
the port 91 of the intake manifold immediately below the throttle
of the carburetor. The opposite side of the diaphragm 23 is
subjected to pressure in chamber portion 27 which is vented V to
atmosphere by way of passage 28.
Control means H, as indicated, is adapted to provide modulation of
intake manifold vacuum in accordance with a signal that rises and
falls more closely with the conditions at which the engine can
assimulate exhaust gas recirculation. For this purpose the vacuum
generated at the primary venturi 10 of the carburetor is utilized;
this signal is generally proportional to the second power of the
air-flow rate through the air horn 9. When intake manifold vacuum
will be generally high at low speeds of the engine, venturi vacuum
will not be low; similarly at high engine speeds, intake manifold
vacuum will be generally insignificant whereas venturi vacuum will
be available. To employ the venturi vacuum signal, control means H
has a housing 6 defining a valve chamber 73 having stepped
cylindrical walls 73a, 73b and 73d; walls 73b and 73d are connected
by a tapered wall 73c. A spool valve 74 is slidable in chamber 73
and has cylindrical land 77 (having diameter 78) slidable in
intimate contact with the cylindrical wall 73a; land 75 (having
diameter 79) is slidable in intimate contact with cylindrical wall
73b and diaphragm 86 is connected at the juncture of tapered wall
73c and wall 73d to define chamber portions 84 and 85. The lands 77
and 75 are spaced apart, by stem 76, a distance so that in the
position as viewed in FIG. 1, inlet 95 and outlet 81 to chamber
portion 80 are in communication.
Chamber portion 80 is defined by the lands 77 and 75; inlet 82 is
connected to a reservoir 98 by passage 95, the reservoir in turn is
in communication with intake manifold vacuum by way of conduit 65
leading to port 91. To insure sufficient vacuum for system
operation at low intake manifold vacuum levels, an accumulator (in
the form of reservoir 98) is utilized; a check valve 100 acting
against seat 101 is employed to preserve the reservoir vacuum.
Outlet 81 is ultimately in communication with the servo-mechanism
E.
Chamber portion 85 (defined between the land 75 and the diaphragm
86) is in communication with atmosphere, identified as vent V, by
way of passage 94. Chamber portion 84 (defined between the
diaphragm 86 and the end of the chamber) has an inlet 88 in
communication (by way of passage 89) with a port 90 entering into
the venturi of the carburetor.
To obtain modulation of the vacuum signal passing through means H,
a differential between intake manifold vacuum (acting on the inner
surfaces of the spool valve) and venturi vacuum (acting on
diaphragm 86) is employed. Initially, venturi vacuum from passage
89 will flex the diaphragm 86 to the right allowing the spool valve
74 to uncover inlet 82, thereby admitting the intake manifold
vacuum to the chamber portion 80. Intake manifold vacuum operating
against the differential faces of lands 77 and 75 will have a
resultant force urging the spool valve to the left and closing
inlet 82. Thus, the resultant intake manifold vacuum force will
oppose that of the venturi vacuum operating on the diaphragm; the
land areas are chosen so that the forces will be generally in
equilibrium or nearly so at mid-range speed conditions for the
engine. If engine conditions are such that the venturi vacuum will
predominate over the intake manifold vacuum resultant, the spool
valve will move further to the right, admitting a larger degree of
intake manifold vacuum as the vacuum control signal. This may occur
at higher speed conditions. Should the intake manifold vacuum
differential predominate, such as at low speeds or idle, the
opposite will occur and the valve 74 will be moved to restrict the
inlet 82. When the spool 74 is moved sufficiently to substantially
restrict or close the inlet 82, the vent V will be opened
communicating with atmosphere by passage 96. The vent V cannot be
uncovered by over movement of the spool valve to the left because
of its attachment to the diaphragm; this prevents a leak to
manifold vacuum. All vents, in the various control means, as well
as in the primary valve means, are vented to the clean side of the
engine air cleaner which is very slightly below atmospheric
pressure.
The modulation by means H provides a type of amplification of a
weak signal (venturi vacuum) to a relatively strong signal (intake
manifold vacuum). At times it may be desirable to construct the
apparatus to produce a constant relationship between exhaust gas
recirculation and the carbureted air flow through the venturi 10.
To accomplish the latter, intake manifold vacuum in chamber portion
80 (which is our control vacuum) will be modulated further by
intake manifold in chamber portion 5 (this manifold vacuum, under
most conditions will be slightly different from the control vacuum
in chamber 80). To this end, a passage 97 communicates chamber
portion 5 with port 91 of the carburetor. Thus at high manifold
vacuum levels, the modulated control vacuum communicated to outlet
81 is reduced from the value which it would normally have at low
manifold vacuum levels. This offsets the effect of the vacuum
signal on the differential pressure across the primary valve D
(namely, the pressure at inlet 21 minus the pressure at the outlet
20). Thus with high manifold vacuum, control vacuum will be
somewhat lowered and the primary valve means D will not be open as
far, thereby providing a smaller flow area to compensate for the
higher vacuum at inlet 21.
Proceeding directly to the third control means G (skipping for the
moment the second control means F) further modulation of the
control vacuum signal is obtained in accordance with transient
conditions of the engine. That is to say, the control vacuum will
be admitted to permit exhaust gas recirculation during
accelerations and short cruises when it is mot desirable to do so.
Control means G comprises a housing 4 defining a valve chamber
having stepped portions; a first cylindrical wall 47 (having a
diameter 44) is interrupted by a smaller cylindrical wall 48
(having a diameter 45). An enlarged chamber 56 is defined at the
right hand side of the chamber. A spool valve 41 with three lands
42, 43 and 53 is arranged to slidably reciprocate within the
chamber portions; land 42 is adapted to slide in intimate
relationship with the cylindrical wall 47, land 43 slides in
intimate relationship with cylindrical wall 48, and the third land
53 (having a diameter similar to land 42) slides in intimate
relationship with the right hand side of the cylindrical wall 47.
The spacing between lands 42 and 43 is arranged to provide a
chamber portion 3 and fluid communication between inlet 49 and
outlet 50 when the lands are so positioned as in FIG. 1.
A compression spring 55 is positioned between the termination of
the chamber of housing 4 and the right hand surface of land 53;
spring 55 urges spool valve 41 in a leftward direction causing the
edge of the land 43 to move across the edge 82 of inlet 49 and
thereby close communication with the outlet. Similarly, the land 42
will uncover a vent allowing the space between the lands to be
reduced to substantially atmospheric pressure. Chamber portions 58
and 56 (which are on opposite sides of land 53) are interconnected
by parallel passages 62 and 63, both of which are commonly in
communication with intake manifold vacuum via passage 66 and 65.
Parallel passage 62 contains a check valve adapted to allow intake
manifold vacuum to enter chamber portion 56; the ball element 60 of
the check valve will be maintained away from valve seat 61 as the
result of vacuum pressure. Parallel passage 63 contains a
restriction 64 which acts as a delay mechanism in allowing the
transient change in pressure between opposite sides of the
restriction.
When intake manifold vacuum is constant, the communication to
chamber portions 58 and 56 will impose equal forces on opposite
sides of land 53; spring 55 can thus cause the valve 41 to
substantially close. When intake manifold vacuum increases due to
deceleration, both the chamber portion 56 and the chamber portion
58 will be further evacuated quickly (check valve 60 will be open)
and the valve 41 will still continue to remain substantially
closed. However, when manifold vacuum decreases due to an increase
in engine acceleration, the check valve 60 will prevent flow from
chamber portion 56 through passage 62. The higher pressure in
chamber portion 58 will force the spool valve to the right
uncovering the inlet 49. The spool valve will move slowly due to
the restriction 64 with dampens fluid flow to or from chamber
portion 56. When transient condition has expired, the valve 41 will
be urged by spring 55 to the left to substantially close the inlet
49 and obtain equilibrium again. The time required to close the
inlet 49 can be varied by changing the size of the chambers
portions 58 and 56 or changing the size of the restrictor 64.
Another damper or delay mechanism can be built in at the left hand
side of the valve means G by use of a vent passage 68 communicating
with chamber portion 57. A parallel passage 67 is incorporated to
also communicate chamber portion 57 with the vent V. In passage 67,
a one way check valve is used, having a ball 70 adapted to seal
against seat 71 when vacuum pressure is sufficiently low in chamber
portion 57. A restrictor 69 is incorporated in passage 68 so as to
delay flow therethrough. Thus, the time required to close inlet 49
can be additionally extended; when there is a transient change of
conditions urging the spool valve 41 to the right or left, the
restrictors 69 and 64, and ball check valves 70 and 60 will
cooperate.
The control vacuum signal delivered from the means G intended for
the servo-mechanism E can be further controlled by second control
means F. Means F is adapted to prevent the admission of the control
vacuum signal during wide-open throttle conditions when exhaust gas
recirculation is not desired. Means F comprises a housing 2
defining a chamber 30 within which is slidable a spool valve 31
having lands 32 and 33 spaced apart sufficiently to allow
communication between an inlet 34 and an outlet 51 for conducting
the control vacuum signal. Valve 31 is normally urged to a closed
position over inlet 34 by spring 35 residing in chamber portion 40
defined between the right hand land 33 and the end of the chamber.
The chamber portion 40 is normally in communication with intake
manifold vacuum by way of passage 36; the chamber portion 37 on the
opposite side of the spool valve (between land 32 and the end of
the chamber) is in communication with atmosphere by either passage
38 or 39 connected as a vent V. Inlet 34 will be closed by the edge
52 of land 33 when manifold vacuum decreases to such a level that
the compression spring acting on the spool valve, moves it
sufficiently leftward. In the closed position, one of the vents
will be open, particularly through passage 38. The control vacuum
signal acting on the surfaces 32a and 33a of the respective lands
32 and 33 will offer no differential force urging the spool valve
in either direction; therefore the differential between the force
of spring 35 and the force of intake manifold vacuum, conveyed by
passages 36 and 65, will determine the position of the spool valve
31.
The scope of this invention comprehends variations of the series of
control means. For example, the system can be used without the
transient valve means G if exhaust gas recirculation is desired at
steady state cruising conditions. Control means F could be
eliminated in conjunction with reservoir 98; valve means D can then
be recalibrated to provide a shut-off at the highest vacuum
encountered at wide-open throttle conditions with metering of the
recirculation over a small range when above the highest vacuum
encountered.
* * * * *