US3884200A

US3884200A - Exhaust gas recirculation control system for internal combustion engines

Info

Publication number: US3884200A
Authority: US
Inventors: Roland B Caldwell
Original assignee: Ranco Inc
Current assignee: Ranco Inc of Delaware
Priority date: 1971-08-03
Filing date: 1971-08-03
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20
Also published as: AU4138772A; AU462247B2; US3739797A; DE2221152B2; DE2221152C3; IT962632B; SE386956B; FR2149736A5; JPS5146211B1; GB1401343A; DE2221152A1; CA959360A

Abstract

A vacuum operated valve for controlling recirculation of exhaust gases through an internal combustion engine is actuated by the output of a vacuum regulator having a source vacuum from the intake manifold which it regulates according to the vacuum in the venturi of the carburetor to produce a vacuum output which is an amplification of the venturi vacuum. The amplified output is terminated when the engine choke is operative. A reservoir maintains a vacuum to the vacuum regulator during moderate acceleration and a valve responsive to a minimum vacuum in the intake causes the vacuum regulator to cut off its output and close the recirculation valve during heavy acceleration or loading.

Description

VACUUM RESERVOIR I United States Patent 1 1 [111 3,884,200

Caldwell May 20, 1975 [54] EXHAUST GAS RECIRCULATION 3,648,672 3/1972 Muroki et a1. 123/119 A CONTROL SYSTEM FOR INTERNAL 3,713,428 l/l973 Sandhagen 123/119 A COMBUSTION ENGINES FOREIGN PATENTS OR APPLICATIONS [75] Inventor; Roland B, Caldwell, Columbus 1,601,374 4/1970 Germany 123/119 A Ohio Primary ExaminerWendell E. Burns [73] Asslgnee' gil Incorporated Columbus Attorney, Agent, or FirmWatts, Hoffman, Fisher &

Heinke [22] Filed: Aug. 3, 1971 21 Appl. No.: 168,595 [57] ABSTRACT A vacuum operated valve for controlling recirculation of exhaust gases through an internal combustion en- [52] US. Cl 123/119 A gins is actuated by the output f a vacuum regulator [51] Int. Cl. F02m 25/06 having a source vacuum f the intake manifold [58] Field of Search. 123/103, 1 19 A, 127, l 19 DB, which it regulates according to the vacuum in the ven- 123/119 D; 60/278 turi of the carburetor to produce a vacuum output which is an amplification of the venturi vacuum. The [56] References Clted amplified output is terminated when the engine choke UNITED STATES PATENTS is operative. A reservoir maintains a vacuum to the 2,071,116 9 7 French 123/1 19 A vacuum regulator during moderate acceleration and a 3,021,827 2/1962 Brunner.... 123/127 valve responsive to a minimum vacuum in the intake 3,507,260 5/1970 Walker 123/119 A causes the vacuum regulator to cut off its output and 3,542,003 10/1970 a o l 19 A close the recirculation valve during heavy acceleration 3,542,004 11/1970 Cornelius 60/278 or l di 3,621,825 11/1971 Ojala 123/119 A 3,643,640 2/1972 Kraus 123/119 A 29 Claims, 8 Drawmg Figures 58 Q/LAWERELIEF) -j VACUUM REGULATOR MANIFOLD PATENTEDHAYZOIQYS 3,884,200

SHEET 1 BF 3 III/ 11/ VIJIJJ 52 v -l3 74) flo H I DUMP (RELIEF) 52 VALVE VACUUM REGULATOR CHECK VACUUM i VALVE REsERvo|R 55 i Fl MANIFOLD INVENTOR. ROLAND B. CALDWELL MJM TTORNEYS PAIENIED 3; 884,200

SHEET 2 BF 3 /VV V0 I II// Fl INVENTOR.

G 4 ROLAND B. GALDWEL.

ATTORNEYS PATENTEUHKY'ZOIQYB 3,884,200

SHEET 3 OF 3 FIG? VACUUMB VOLUME OF Q RECRCULATED GAS FIGB W A c ENGINE SPEED W INVENTOR.

ROLAND B. CADWELL FIGB BY 1 2w a M ATTOREYS v EXHAUST GAS RECIRCULATION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION It is well known that nitrogen oxides are produced by internal combustion engines during lean gas mixture conditions and that the production of these oxides may be substantially reduced or eliminated by injecting or recirculating exhaust gases into the intake manifold. This practice is referred to as exhaust gas recirculation and is desirable for reducing emission of nitrogen oxide from engines of automobiles, etc. During idling, high speeds, heavy acceleration or heavy loading of an internal combustion engine, recirculation of the exhaust gases adversely affects operation of the engine and furthermore, under such conditions, a rich fuel mixture is present which does not produce the objectional nitrogen oxide-It has been proposed heretofore to provide an exhaust recirculating valve operative under various influences to recirculate exhaust gases only during certain engine operating conditions so as to minimize the discharge of nitrogen oxide into the atmosphere. Examples of such proposals are disclosed in US. Pat. Nos. 2,154,417, 2,419,747 and 3,507,260. These proposals are impractical or costly and have not been generally adopted.

THE PRESENT INVENTION An object of the present invention is the provision 'of a valve to control recirculation of exhaust gases inan internal combustion engine, which valve is operated to increase the flow of recirculated exhaust gases in accordance with the velocity of air drawn into the carburetor during utilization of relatively lean fuel mixtures by the engine and to reduce or stop the flow of recirculated exhaust gases in response to relatively rich fuel.

vacuum for operating the valve being provided from the intake manifold of the engine through a vacuum regulator operated in accordance with the vacuum at the venturi of the engine carburetor and which regulator has a vacuum output to the valve actuator which is an amplification of the venturi vacuum. By this arrangement a vacuum for opening the exhaust recirculating valve is available for increasing the valve opening as the rate or volume of combustion air intake of the engine increases within a given range, and when the intake manifold vacuum decreases below a given value in response to acceleration, loading or high speed, the valve will be operated to throttle or close off the recirculation of exhaust gases, irrespective of an increase in vacuum at the venturi. i

A further object of the invention is the provision of a vacuum operated valve of the character described having means to prevent opening of the valve during the time the engine choke valve is closed and the vacuum at the venturi thereby increased beyond normal. A still further object of the invention is the provision of a vacuum operated valve of the type described in which the source of operating vacuum for the recirculating control valve includes a vacuum reservoir to maintain sufficient vacuum to open the valve during moderate acceleration, and valve means to vent the reservoir in response to a full ope'n throttle condition to prevent opening of the recirculating control valve.

Other objects and advantages of the invention will be apparent from the following description of a preferred form of the invention, reference being made to the accompanying drawings wherein:

FIG. 1 is a schematic showing of a valve and its controlling components for'controlling the recirculation of exhaust gases through an internal combustion engine in accordance with the present invention;

FIG. 2 is a sectional view of the exhaust recirculating valve in FIG. 1 and shown on a larger scale;

FIG. 3 is a view, partly in section, of a vacuum regulator depicted in FIG. 1 and on a larger scale;

FIG. 4 is a graph depicting the relative vacuum in certain portions of the control system and engine for the recirculating valve shown in FIG. 1 during different engine speeds;

FIG. 5 is a sectional view of a dump valve shown in FIG. 1 and on a larger scale;

FIGS. 6 and 7 are fragmentary sectional views of the intake of the engine carburetor showingdetails of a choke valve operated in two different positions; and

.FIG. 8 is a graph showing the flow of exhaust gases through the recirculation valve in relation to vacuum conditions in the engine and valve control system.

Referring to FIG. 1 of the drawings, an exhaust gas recirculating valve and its control system is shown for a four-cycle internal combustion engine for an automotive vehicle. The engine and vehicle are not shown in l .the venturi 12 in the inlet is distributed through the" manifold to the engine cylinders in the usual manner.

In accordance with the present invention, a valve 16 controls the flow of exhaust gases from the exhaust manifold 15 to the intake manifold 14 for recirculation into the cylinders. The inlet of valve 16 is connected with the exhaust manifold through a suitable conduit 1,7, and the outlet of the valve is connected with the intake manifold through asuitable conduit 20. The valve 16, details of which may be seen in FIG. 2,

' includes a body 21 comprised of two rigid dish shaped

members

22, 23 arranged with the edges of the open sides joined with a flexible diaphragm 24 disposed therebetween. The peripheral edges of the diaphragm 24 are hermetically sealed to the joining edges of the

members

22, 23 and the diaphragm divides the body into separate upper and

lower chambers

25, 26.

The chamber 26 has an inlet 27 in the bottom wall and an outlet 30 in the side thereof. A valve seat 31 is formed at the inlet 27 and is adapted to be closed by a poppet valve member 32. The valve member 32 is connected with the diaphragm 24 by a stem 33 and opens and closes the seat 31 in response to deflections of the diaphragm. I

The valve member 32 is urged to close on seat 31 by a spring 34 compressed between the top wall of the chamber 25 and the diaphragm 24. The valve member 32 is moved from the valve seat 31 by a vacuum produced in the chamber 25. More or less of a vacuum is produced in the chamber by the output of a vacuum amplifier 35, which is connected with the chamber through a tube 37 attached to an outlet stem 36.

A plate 38 extends across the chamber 26 and defines an opening which closely surrounds the valve stem 33. The chamber 26 is open to atmospheric pressure between the plate 38 and the diaphragm 24 via a suitable port or vent opening 39, as is conventional, to enable controlled deflection of the diaphragm 24 by the amplifier 35.

As best seen in FIG. 3, the amplifier comprises a frame formed of two rigid dish shaped members 40, 41 having their open sides attached to one another about the edges thereof. A flexible diaphragm 42 is disposed between the members 40, 41 with the edges thereof hermetically joined with the edges of the open side of the member 40. The diaphragm 42 and member forms an input vacuum signal chamber 43. A vacuum regulator assembly 44 is suitably secured in an opening in the bottom wall of the member 41. The vacuum regulator 44 is preferably like that which is the subject matter of U.S. Pat. No. 3,125,111 and includes a body 45 having a port 48 connected with the interior of the intake manifold, described more fully hereinafter, by a tube 47. A vacuum signal output port 46 is connected with the stem 36 of the chamber 25 of valve 16 by the tube 37. The degree of vacuum signal at the port 46 is determined by the position of a plunger 50 of the vacuum regulator 44 and which plunger is attached to the diaphragm 42. The member 41 has an opening therein to atmosphere so that the position of the plunger 50 will depend upon the degree of vacuum above the diaphragm 42. The manner in which the vacuum signal at the outlet port 48 is regulated is explained in the aforementioned US, Pat. No. 3,l25,l l l. The vacuum signal chamber 43 has an outlet in the form of a stem 51 which is connected by a tube 52 with the venturi 12 of the carburetor as is explained in greater detail hereinafter. The amplifier 35 is arranged so that as the vacuum in the venturi of the carburetor increases, the vacuum at the port 48, referred to as the output vacuum, increases correspondingly from a zero value, causing the valve member 32 to move from the seat 31.

In the form shown, the output vacuum of the amplifier 35 is ten times that of the vacuum at the venturi 12. Thus, 0.1 Hg vacuum at the venturi will result in 1.0 Hg vacuum at the outlet 48, provided that degree of vacuum is present in the manifold. This ratio of amplification, or any other ratio desired, is obtained by designing the area of diaphragm 42 such that the operating plunger 50 will have sufficient force applied thereto through the diaphragm action to provide the desired amplification in the vacuum output.

For a fuller understanding of the manner in which the vacuum powered valve 16 is operated, reference is made to FIG. 4. Line MV shows the inches of Hg in the intake manifold according to increasing engine RPM under a constant load, and line VV shows the venturi vacuum for corresponding engine speeds. Line AV shows the vacuum output of the amplifier 35, the full portion indicating the actual output and the broken portion indicating the theoretical output if a higher vacuum were present in the manifold.

It will be noted that the vertical line VO indicates the engine speed at which it is desired to commence recirculation of exhaust gases. In the form shown, the valve member 32 is caused to open when the vacuum above the diaphragm 42 increases to 3" Hg by the loading spring 34. This increase in vacuum corresponds to an increase to 0.3 inches Hg of venturi vacuum. The degree of vacuum required to open the valve 16 could be changed by changing the loading characteristics of the spring 34.

The vacuum source for the vacuum amplifier 35 is the intake manifold 14 via a conduit 55, a check valve 56, a reservoir tank 57 and the conduit 47. The tank 57 is of sufficient size to maintain a vacuum in the inlet 47 of the vacuum amplifier 35 during short periods when the vacuum may be disrupted in the manifold due to temporary rapid opening of the engine throttle. The check valve 56 between the tank 57 and the intake manifold closes to prevent the vacuum in the tank 57 from dropping to the level of that in the intake manifold, during the rapid and temporary excessive opening of the engine throttle. The check valve may be of any well known form and a further disclosure of the details thereof are unnecessary to the understanding of the invention.

In the present form of the invention, it is desirable to prevent recirculation of exhaust gases whenever the manifold pressure drops below 3 inches Hg. This condition will occur when the throttle is relatively fully opened causing a richer fuel mixture to be fed to the engine. Open throttling will occur on heavy accelleration, loading on the engine or attainment of a high speed of the vehicle driven by the engine. Accordingly, a dump valve 58 is provided between the manifold and the vacuum signal conduit 52 which opens the signal to atmosphere in response to a manifold vacuum of 3 inches or less. Thus, the vacuum output of the amplifier 35 is reduced to zero by the dump valve 58 whenever the throttle is operated to produce loading of the engine, etc., causing vacuum in the intake manifold to fall below 3 inches Hg. Referring to FIG. 5, the valve 58 comprises a housing formed by the concave formed members 60, 61 which are joined about the edges of their open sides. A diaphragm 62 is crimped between or otherwise hermetically secured to, the joined edges of the members 60, 61 and forms with those members upper and

lower chambers

63, 64. The upper chamber 63 is open to atmosphere through a passage 65 and the lower chamber 64 is connected with the intake manifold through the conduit 55 connected with a connector nipple 66. A valve housing 67 is provided over the member 60, and the top wall of the member has a valve port 76 therethrough which opens inside the housing. The port 70 is adapted to be closed by a valve member 71 which has a stem 72 attached to the diaphragm 62. A compression spring 73 between the diaphragm and the bottom wall of the member 61 urges the valve member 71 from the port whenever the vacuum in the member 61 is reduced to 3 inches Hg. When the vacuum in the member 61, (and the manifold) is above 3 inches Hg, the valve 71 closes the port '70. The valve housing is connected by a conduit '74 with the conduit 52. Accordingly, when valve member 71 moves from the port 70, the vacuum signal for regulator 35 is reduced to zero through the opening to atmosphere of the dump valve 58. The vacuum output of the other regulator 35 will be zero and valve 16 will be closed.

When the engine choke valve 11 is positioned to restrict air flow through the carburetor intake 10, a vacuum will be produced below the choke valve and at the venturi 12. To prevent opening of the valve 16 by the regulator 35 in response to a vacuum created by closing of the choke 11, a bleed valve 76 is positioned in the intake upstream of the choke valve 11 and is connected with the conduit 52. The valve 76 includes a port 77 which is positioned to be closed by the choke valve 11 when the choke is in its open, inoperative position, as seeen in FIG. 6. When the choke 11 is closed, as seen in FIG. 7, the port 77 is open to atmosphere and consequently the vacuum signal to the regulator 35 is zero and valve 16 will remain closed, although the vacuum at the venturi 12 may be above 0.3 inches Hg.

When the engine is operating at a speed to create 0.] inch Hg at the venturi 12, and a vacuum of at least 3 inches Hg is present in the intake manifold the amplifier 35 will have a vacuum output of 3 inches Hg. This output will cause the valve 16 to open. As the speed of the engine increases by increased opening of the throttle and in the absence of an appreciable load in the engine, the venturi vacuum will increase and the amplifier 35 vacuum output will increase, causing the valve 16 to open still further. As the engine approaches a wide open throttle condition, the intake manifold vacuum will decrease below the theoretical vacuum output of the amplifier 35. This reduction in vacuum causes the valve 16 to throttle the flow of gas therethrough. When the manifold vacuum is reduced to 3 inches Hg, the valve 58 vents the input to the amplifier 35 which results in closing of the gas control valve 16.

The foregoing description of the flow of recirculated exhaust gas and the related vacuum values are shown in FIG. 8. R6 represents the volume of recirculated gas entering the manifold through the valve 16. MV represents the vacuum in the intake manifold and VV represents the venturi vacuum. The output vacuum of the amplifier 35 is represented at AV. The dotted portion of AV represents the theoretical vacuum output inasmuch as the vacuum available in the intake manifold has decreased below the value called for by the amplifier 35. Thus the vacuum available for actuating valve 16 is represented by the lines AB and BC.

I claim:

1. In an internal combustion engine including a carburetor having a venturi throat, an intake manifold, an exhaust gas manifold and structure defining a passageway between said intake and exhaust manifolds: exhaust gas recirculating valve means effective to control the flow of exhaust gas through said passageway, said valve means comprising structure defining a vacuum chamber and a valving member operative in response to changes in vacuum pressure in said chamber to vary the rate of flow of exhaust gas through said passageway, vacuum control means for controllably communicating said vacuum chamber to said intake manifold said vacuum control means comprising a vacuum regulator having a vacuum inlet communicating with said intake manifold, a regulated vacuum outlet communicating with said vacuum chamber and a pressure signal inlet, and a pressure signal passage between said venturi throat and said pressure signal inlet, said regulator means controllably communicating said intake manifold and said vacuum chamber in relation to the pressure signal level communicated from said venturi throat to said pressure signal inlet.

2. An internal combustion engine as defined in claim 1 wherein said vacuum regulator further comprises pressure responsive actuating means communicating with said pressure signal from said venturi throat and 5 effective to govern communication between said vacuum inlet and said vacuum outlet as a function of the vacuum at said venturi throat.

3. An internal combustion engine as defined in claim 2 further characterized by a control valve actuatable to communicate the pressure responsive actuating means to atmosphere in response to a relatively wide open throttle condition of the engine.

4. An internal combustion engine as defined in claim 2 further characterized by a control valve for communicating the pressure response actuating means to atmosphere in response to a predetermined vacuum in said intake manifold.

5. An internal combustion engine as defined in claim 1 wherein said carburetor further comprises a choke movement of said choke valve means to render said vacuum regulator ineffective to respond to the pressure signal level from said venturi throat.

6. In an internal combustion engine defining at least one combustion chamber, a combustion air intake passage, an exhaust gas passage, and a passageway for communicating said intake and exhaust passages to enable a flow of exhaust gas to said combustion chamber: a fluid pressure operated valve means for controlling the flow of exhaust gas via said passageway into said combustion chamber, said valve means operable between an open condition and a closed condition wherein the flow of exhaust gas through said passageway is substantially terminated, fluid pressure source means providing a supply of fluid pressure communicable with said valve means for operating said valve means, a fluid pressure regulator adapted to control the fluid pressure communication between said source and said valve means for governing operation of said valve means between said conditions, and regulator controlling signal means for supplying fluid input signal to said regulator which varies as a function of the rate of flow of gas through the engine, said regulator effective to govern communication between said source and said valve means in response to said fluid input signal.

7. An internal combustion engine defined in claim 6 in which said fluid pressure source means comprises the intake manifold to said engine, and said regulator controlling signal means comprises a venturi in said air intake. I

8. An internal combustion engine as defined in claim 7 further characterized by means responsive to a relatively wide open throttle condition of said engine for operating said valve means to the closed condition.

9. An internal combustion engine as defined in claim 6 further characterized by means responsive to a drop in manifold vacuum for closing said valve.

10. An internal combustion engine as defined in claim 7 further characterized by means to supersede the control of said regulator by said venturi in response to a given pressure in said intake manifold.

11. In combination with an internal combustion engine having an air intake passage, a throttle means for governing the flow of combustion air entering the engine, and an exhaust passage, a system for introducing exhaust gas into said intake passage from said exhaust passage under predetermined running conditions of the valve means, and valving means responsive to closing engine comprising: a flow passageway between said intake passage and said exhaust passage; differential pressure responsive valve means comprising a valve member in said passageway which is movable in response to differential pressure applied to said valve means to enable flow through said passageway to vary, said valve member having a closed position in which exhaust gas flow through said passageway is blocked; source means communicable with said valve means and defining a source of operating pressure for said valve means which varies substantially in relation to operation of the throttle means; regulator means connected between said source means and said valve means for controlling the magnitude of the source means pressure communicated to said valve means to govern the differential pressure applied to said valve means, said regulator means comprising a regulator member movable inrelation to changes in the rate of combustion air intake into said engine from a first position at engine intake air flow rates below a predetermined flow rate wherein said valve member is in its closed position, said member moving from said first position in response to increasing flow rates of engine intake air above said predetermined rate whereby said regulator means is effective to increase differential pressure applied to said valve means to progressively move said valve member from said closed position; and said souce means pressure progressively changing as the engine approaches an open throttle condition to progressively reduce the differential pressure available for operating said valve means irrespective of the position of said regulator member so that said regulator means is ineffective to govern the communication between said source means and said valve means when the differential pressure demanded by said regulator means is greater than the differential pressure available from said source means, the position of said valve member thereafter controlled directly from said source means in relation to changes in source means pressure. I

12. The combination claimed in claim 11 further including means for operating said regulator member to said first position in response to detection of intake passage static pressures less than a predetermined relatively low magnitude with respect to atmospheric pressure so that said valve member is operated to said closed position.

13. The combination claimed in claim 11 further including a choke valve in said intake passage and structure cooperable with said choke valve and said regulator means for effecting movement of said regulator member to its first position when said choke valve is away from its inoperative position whereby said valve member is in its closed position when the engine is choked.

14. A method of controllably recirculating engine exhaust gas into the combustion intake air of an engine to reduce the production of undesirable exhaust emissions from the engine comprising:

a. providing a passageway through which engine exhaust gas can flow for mixing with intake combustion air; and,

b. valving the flow of engine exhaust gas through the passageway in response to engine operating conditions including:

i. providing a pressure operated valve means actuable according to the magnitude of an applied pressure differential to modulate the flow of recirculated exhaust gas;

ii. communicating the valve means to a source of valve means operating fluid pressure;

iii. sensing the rate of flow of intake combustion air to the engine;

iv. controlling the communication of valve means operating fluid pressure from the source as a function of sensed intake combustion air flow rates above a predetermined rate so that said valve means is operated to enable increased recirculation of exhaust gas as intake combustion air flow rates increase 'above the predetermined rate; and,

v. reducing the magnitude of the valve means operating source pressure as the engine approaches a wide-open-throttle condition to reduce the valve means operating pressure applied to the valve means irrespective of the sensed intake combustion air flow rate whereby the amount of recirculated exhaust gas is reduced as the engine approaches the wide open throttle condition.

15. The method defined in claim 14 further charac- J terized by maintaining the valve means operating pressure less than .a given magnitude while the sensed flow rate of intake combustion air is less than said predetermined rate whereby recirculation of exhaust gas is minimized.

16. The method defined in claim 14 wherein sensing the flow rate of intake combustion air comprises determining a pressure of the combustion air flowing in-an air intake of the engine and controlling communication from the source to the valve means comprises controlling the magnitude of the operating pressure applied to the valve means as a function of the sensed pressure of the intake air flowing in the engine air intake.

17. The method defined in claim 16 further characterized by maintaining the operating pressure applied to said valve means at a predetermined greater magnitude than the magnitude of the sensed pressure. of the air flowing inthe air intake of the engine throughout a given range of intake combustion air flow rates and while the source pressure is greater than the predetermined valve operating pressure magnitude.

18. The method defined in claim 14 further characterized by terminating said flow of recirculating exhaust gas when the magnitude of the source pressure is reduced below a given minimum.

19. In an exhaust gas recirculation system for an internal combustion engine having a combustion air intake duct in which a throttle valve islocated, an intake it manifold defined downstream from said throttle valve, an exhaust manifold and a flow passageway defined between said exhaust manifold and said intake manifold: a. exhaust gas recirculating valve means for enabling exhaust gas from the exhaust manifold to be recirculated to the intake manifold through said flow passageway, said recirculating valve means comprising a valve member operated by pressure energy supplied from said intake manifold and having an open condition wherein exhaust gas is recirculated and a closed condition for preventing exhaust gas recirculation, said valve member operable in said open condition to modulate the flow of recirculated exhaust gas through said flow passageway;

b. pressure regulator means for controlling the magnitude of the pressure communicated between the recirculating valve means and the intake manifold in relation to the flow rate of air in the combustion air intake duct under predetermined engine operat ing conditions and in relation to the intake manifold pressure under other predetermined engine operating conditions;

c. said pressure regulator means defining:

i. an input signal pressure port in communication with said intake duct at a location upstream from said throttle valve for providing intake air flow rate responsive pressure signals to said regulator means,

ii. an input operating pressure port in communication with said intake manifold; and,

iii. an output valve operating pressure port in communication with said recirculating valve means;

d. said regulator means variably communicating valve operating pressure to said valve means as an amplified function of the input signal level and effective to amplify input pressure signal levels for application to the recirculating valve means via said valve operating pressure port;

e. said regulator means operative to govern the recirculating valve condition as a direct function of intake manifold pressure independently of the air flow rate in the intake duct when the engine is operated under a condition wherein the output valve operating pressure required by the input signal level would otherwise exceed the intake manifold pressure.

20. In an exhaust gas recirculation system for an internal combustion engine having a combustion air intake duct through which combustion air flows to a combustion chamber, a throttle valve disposed in said air duct, an engine exhaust gas system through which exhaust gas flows from said combustion chamber, and passage means defining a flow path along which exhaust gas may flow from said exhaust gas system for mixing with combustion air:

a. pressure operated valve means for controlling the flow of exhaust gas in said passage means, said valve means comprising a valve member having an open condition in which the flow of exhaust gas in said passage means is controlled and a closed condition wherein exhaust gas flow in said passage means is blocked;

b, pressure source means defined at least in part by a portion of said intake duct downstream from said throttle valve;

c. pressure signal means defined at least in part by a second portion of said intake duct upstream from said throttle valve and effective to produce a pressure signal having a relatively small magnitude and which varies in relation to the flow rate of intake air in said second duct portion; and,

d. pressure regulator means for controlling the condition of said valve means and defining a signal pressure input port communicating with said pressure signal means, a pressure source port communicating with said pressure source means and a valve operating pressure output port communicating with said valve means, said regulator means effective to variably communicate valve operating pressure from said source means to said valve means via said output port as an amplified function of input pressure signals provided to said signal pressure input port for controlling operation of said valve means in its open condition as a function of said input pressure signals under predetermined operating conditions of the engine, said regulator means directly communicating said valve means to said pressure source means to control operation of said valve means in its open condition as a direct function of said source means pressure irrespective of intake air flow rate pressure signal levels when the output port pressure level demanded by the pressure signal is of greater magnitude than the source means pressure.

21. In an internal combustion engine including a combustion air intake, a fluid pressure operated valve means for controlling the recirculation of exhaust gases into the combustion chambers of said engine, source means providing a source of fluid pressure connected with said valve for operating said valve, said source means comprising an intake manifold of said engine, a fluid pressure regulator adapted to regulate the fluid pressure from said source to said valve, means comprising a venturi in said air intake for controlling said regulator in response to changes in velocity of the air entering the engine through said intake, and means responsive to a relatively wide open throttle condition of said engine for closing said valve means.

22. In an internal combustion engine including a combustion air intake, a fluid pressure operated valve means for controlling the recirculation of exhaust gases into the combustion chambers of said engine, source means providing a source of fluid pressure connected with said valve for operating said valve, said source means comprising an intake manifold of said engine, a fluid pressure regulator adapted to regulate the fluid pressure from said source to said valve, means comprising a venturi in said air intake for controlling said regulator in response to changes in velocity of the air entering the engine through said intake, and means responsive to a drop in intake manifold vacuum for closing said valve.

23. In an internal combustion engine including a combustion air intake, a fluid pressure operated valve means for controlling the recirculation of exhaust gases into the combustion chambers of said engine, source means providing a source of fluid pressure connected with said valve for operating said valve, said source means comprising an intake manifold of said engine, a fluid pressure regulator adapted to regulate the fluid pressure from said source to said valve, means comprising a venturi in said air intake for controlling said regulator in response to changes in velocity of the air entering the engine through said intake, and means to supersede the control of said regulator by said venturi in response to a given pressure in said intake manifold.

24. In an internal combustion engine including a carburetor having a venturi throat and an intake manifold, valve means to control the flow of exhaust gas to the combustion chambers of said engine, said valve means including a vacuum chamber and a member operative in response to changes in vacuum in said chamber to vary the rate of flow through said valve means, characterized by means for connecting said vacuum chamber to said intake manifold whereby the vacuum in said manifold affects the vacuum in said chamber and including a vacuum regulator having a vacuum inlet connected with said intake manifold and a regulated vacuum outlet connected with said vacuum chamber, means to control said vacuum regulator in response to the vacuum at the venturi of said engine comprising pressure responsive actuating means connected with said venturi throat and responding to the vacuum at said throat, and a valve for connecting the pressure responsive actuating means to atmosphere in response to a relatively wide open throttle condition of the engine.

25. In an internal combustion engine including a carburetor having a venturi throat and an intake manifold, valve means to control the flow of exhaust gas to the combustion chambers of said engine, said valve means including a vacuum chamber and a member operative in response to changes in vacuum in said chamber to vary the rate of flow through said valve means, characterized by means for connecting said vacuum chamber to said intake manifold whereby the vacuum in said manifold affects the vacuum in said chamber and including a vacuum regulator having a vacuum inlet connected with said intake manifold and a regulated vacuum outlet connected with said vacuum chamber, means to control said vacuum regulator in response to the vacuum at the venturi of said engine comprising pressure responsive actuating means connected with said venturi throat and responding to the vacuum at said throat, and, a valve for connecting the pressure responsive actuating means to atmosphere in response to a predetermined vacuum in said manifold.

26. In an internal combustion engine including a carburetor having a venturi throat and choke valve means, and an intake manifold, valve means to control the flow of exhaust gas to the combustion chambers of said engine, said valve means including a vacuum chamber and a member operative in response to changes in vacuum in said chamber to vary the rate of flow through said valve means, characterized by means for connecting said vacuum chamber to said intake manifold whereby the vacuum in said manifold affects the vacuum in said chamber and including a vacuum regulator having a vacuum inlet connected with said intake mani fold and a regulated vacuum outlet connected with said vacuum chamber, means to control said vacuum regulator in response to the vacuum at the venturi of said engine, and means responsive to closing movement of said choke valve means to render said vacuum regulator inoperative to actuate said valve means controlling flow of gas into said engine.

27. In an internal combustion engine including a carburetor having a venturi throat and an intake manifold, valve means to control the flow of exhaust gas to the combustion chambers of said engine, said valve means including a vacuum chamber and a member operative in response to changes in vacuum in said chamber to vary the rate of flow through said valve means, characterized by means for connecting said vacuum chamber to said intake manifold whereby the vacuum in said manifold affects the vacuum in said chamber and including a vacuum regulator having a vacuum inlet connected with said intake manifold and a regulated vacuum outlet connected with said vacuum chamber, and means to control said vacuum regulator in response to the vacuum at the venturi of said engine, said means to control said vacuum regulator being effective to cause the regulator to provide an output of vacuum having an appreciably higher inches of mercury value than the inches of mercury value of the vacuum at the venturi throat.

28. A method of controllably recirculating engine exhaust gas into the combustion intake air of an engine to reduce the production of undesirable exhaust emissions from the engine comprising:

a. providing an engine intake combustion air passage, an engine exhaust gas passage, and a passageway through which engine exhaust gas can flow for mixing with intake combustion air; and,

b. valving the flow of engine exhaust gas through said passageway in response to engine operating conditions including:

i. providing a pressure operated valve means actuable to control the flow through said passageway;

ii. communicating said valve means to a source of valve means operating pressure;

iii. sensing the flow rate in one of said passages;

iv. producing a fluid signal which varies according to the sensed flow rate in said one passage;

v. controlling the communication of valve means operating fluid pressure to said valve means from said source according to said fluid signal to control flow through said passageway; and,

vi. reducing the magnitude of the fluid pressure applied to the valve means when the engine is operated substantially at a wide open throttle condition for operating said valve means to minimize flow through said passageway irrespective of the flow rate in said one passage.

29. The method claimed in claim 28 further comprising operating the valve means to a condition for minimizing flow through said passageway when the engine is operated at idle speed.

Claims

2. An internal combustion engine as defined in claim 1 wherein said vacuum regulator further comprises pressure responsive actuating means communicating with said pressure signal from said venturi throat and effective to govern communication between said vacuum inlet and said vacuum outlet as a function of the vacuum at said venturi throat.

5. An internal combustion engine as defined in claim 1 wherein said carburetor further comprises a choke valve means, and valving means responsive to closing movement of said choke valve means to render said vacuum regulator ineffective to respond to the pressure signal level from said venturi throat.

7. An internal combustion engine defined in claim 6 in which said fluid pressure source means comprises the intake manifold to said engine, and said regulator controlling signal means comprises a venturi in said air intake.

11. In combination with an internal combustion engine having an air intake passage, a throttle means for governing the flow of combustion air entering the engine, and an exhaust passage, a system for introducing exhaust gas into said intake passage from said exhaust passage under predetermined running conditions of the engine comprising: a flow passageway between said intake passage and said exhaust passage; differential pressure responsive valve means comprising a valve member in said passageway which is movable in response to differential pressure applied to said valve means to enable flow through said passageway to vary, said valve member having a closed position in which exhaust gas flow through said passageway is blocked; source means communicable with said valve means and defining a source of operating pressure for said valve means which varies substantially in relation to operation of the throttle means; regulator means connected between said source means and said valve means for controlling the magnitude of the source means pressure communicated to said valve means to govern the differential pressure applied to said valve means, said regulator means comprising a regulator member movable in relation to changes in the rate of combustion air intake into said engine from a first position at engine intake air flow rates below a predetermined flow rate wherein said valve member is in its closed position, said member moving from said first position in response to increasing flow rates of engine intake air above said predetermined rate whereby said regulator means is effective to increase differential pressure applied to said valve means to progressively move said valve member from said closed position; and said souce means pressure progressively changing as the engine approaches an open throttle condition to progressively reduce the differential pressure available for operating said valve means irrespective of the position of said regulator member so that said regulator means is ineffective to govern the communication between said source means and said valve means when the differential pressure demanded by said regulator means is greater than the differential pressure available from saiD source means, the position of said valve member thereafter controlled directly from said source means in relation to changes in source means pressure.

14. A method of controllably recirculating engine exhaust gas into the combustion intake air of an engine to reduce the production of undesirable exhaust emissions from the engine comprising: a. providing a passageway through which engine exhaust gas can flow for mixing with intake combustion air; and, b. valving the flow of engine exhaust gas through the passageway in response to engine operating conditions including: i. providing a pressure operated valve means actuable according to the magnitude of an applied pressure differential to modulate the flow of recirculated exhaust gas; ii. communicating the valve means to a source of valve means operating fluid pressure; iii. sensing the rate of flow of intake combustion air to the engine; iv. controlling the communication of valve means operating fluid pressure from the source as a function of sensed intake combustion air flow rates above a predetermined rate so that said valve means is operated to enable increased recirculation of exhaust gas as intake combustion air flow rates increase above the predetermined rate; and, v. reducing the magnitude of the valve means operating source pressure as the engine approaches a wide-open-throttle condition to reduce the valve means operating pressure applied to the valve means irrespective of the sensed intake combustion air flow rate whereby the amount of recirculated exhaust gas is reduced as the engine approaches the wide open throttle condition.

15. The method defined in claim 14 further characterized by maintaining the valve means operating pressure less than a given magnitude while the sensed flow rate of intake combustion air is less than said predetermined rate whereby recirculation of exhaust gas is minimized.

16. The method defined in claim 14 wherein sensing the flow rate of intake combustion air comprises determining a pressure of the combustion air flowing in an air intake of the engine and controlling communication from the source to the valve means comprises controlling the magnitude of the operating pressure applied to the valve means as a function of the sensed pressure of the intake air flowing in the engine air intake.

17. The method defined in claim 16 further characterized by maintaining the operating pressure applied to said valve means at a predetermined greater magnitude than the magnitude of the sensed pressure of the air flowing in the air intake of the engine throughout a given range of intake combustion air flow rates and while the source pressure is greater than the predetermined valve operating pressure magnitude.

19. In an exhaust gas recirculation system for an internal combustion engine having a combustion air intake duct in which a throttle valve is located, an intake manifold defined downstream from said throttle valve, an exhaust manifold and a flow passageway defined between said exhaust manifold and said intake manifold: a. exhaust gas recircuLating valve means for enabling exhaust gas from the exhaust manifold to be recirculated to the intake manifold through said flow passageway, said recirculating valve means comprising a valve member operated by pressure energy supplied from said intake manifold and having an open condition wherein exhaust gas is recirculated and a closed condition for preventing exhaust gas recirculation, said valve member operable in said open condition to modulate the flow of recirculated exhaust gas through said flow passageway; b. pressure regulator means for controlling the magnitude of the pressure communicated between the recirculating valve means and the intake manifold in relation to the flow rate of air in the combustion air intake duct under predetermined engine operating conditions and in relation to the intake manifold pressure under other predetermined engine operating conditions; c. said pressure regulator means defining: i. an input signal pressure port in communication with said intake duct at a location upstream from said throttle valve for providing intake air flow rate responsive pressure signals to said regulator means; ii. an input operating pressure port in communication with said intake manifold; and, iii. an output valve operating pressure port in communication with said recirculating valve means; d. said regulator means variably communicating valve operating pressure to said valve means as an amplified function of the input signal level and effective to amplify input pressure signal levels for application to the recirculating valve means via said valve operating pressure port; e. said regulator means operative to govern the recirculating valve condition as a direct function of intake manifold pressure independently of the air flow rate in the intake duct when the engine is operated under a condition wherein the output valve operating pressure required by the input signal level would otherwise exceed the intake manifold pressure.

20. In an exhaust gas recirculation system for an internal combustion engine having a combustion air intake duct through which combustion air flows to a combustion chamber, a throttle valve disposed in said air duct, an engine exhaust gas system through which exhaust gas flows from said combustion chamber, and passage means defining a flow path along which exhaust gas may flow from said exhaust gas system for mixing with combustion air: a. pressure operated valve means for controlling the flow of exhaust gas in said passage means, said valve means comprising a valve member having an open condition in which the flow of exhaust gas in said passage means is controlled and a closed condition wherein exhaust gas flow in said passage means is blocked; b. pressure source means defined at least in part by a portion of said intake duct downstream from said throttle valve; c. pressure signal means defined at least in part by a second portion of said intake duct upstream from said throttle valve and effective to produce a pressure signal having a relatively small magnitude and which varies in relation to the flow rate of intake air in said second duct portion; and, d. pressure regulator means for controlling the condition of said valve means and defining a signal pressure input port communicating with said pressure signal means, a pressure source port communicating with said pressure source means and a valve operating pressure output port communicating with said valve means, said regulator means effective to variably communicate valve operating pressure from said source means to said valve means via said output port as an amplified function of input pressure signals provided to said signal pressure input port for controlling operation of said valve means in its open condition as a function of said input pressure signals under predetermined operating conditions of the engine, said regulator means directly communicating said valve means to said pressure source means to control operation of said valve meaNs in its open condition as a direct function of said source means pressure irrespective of intake air flow rate pressure signal levels when the output port pressure level demanded by the pressure signal is of greater magnitude than the source means pressure.

26. In an internal combustion engine including a carburetor having a venturi throat and choke valve means, and an intake manifold, valve means to control the flow of exhaust gas to the combustion chambers of said engine, said valve means including a vacuum chamber and a member operative in response to changes in vacuum in said chamber to vary the rate of flow through said valve means, characterized by means for connecting said vacuum chamber to said intake manifold whereby the vacuum in said manifold affects the vacuum in said chamber and including a vacuum regulator having a vacuum inlet connected with said intake manifold and a regulated vacuum outlet connected with said vacuum chamber, means to control said vacuum regulator in response to the vacuum at the venturi of said engine, and means responsive to closing movement of said choke valve means to render said vacuum regulator inoperative to actuate said valve means controlling flow of gas into said engine.

28. A method of controllably recirculating engine exhaust gas into the combustion intake air of an engine to reduce the production of undesirable exhaust emissions from the engine comprising: a. providing an engine intake combustion air passage, an engine exhaust gas passage, and a passageway through which engine exhaust gas can flow for mixing with intake combustion air; and, b. valving the flow of engine exhaust gas through said passageway in response to engine operating conditions including: i. providing a pressure operated valve means actuable to control the flow through said passageway; ii. communicating said valve means to a source of valve means operating pressure; iii. sensing the flow rate in one of said passages; iv. producing a fluid signal which varies according to the sensed flow rate in said one passage; v. controlling the communication of valve means operating fluid pressure to said valve means from said source according to said fluid signal to control flow through said passageway; and, vi. reducing the magnitude of the fluid pressure applied to the valve means when the engine is operated substantially at a wide open throttle condition for operating said valve means to minimize flow through said passageway irrespective of the flow rate in said one passage.