US3888222A

US3888222A - Exhaust gas recirculation

Info

Publication number: US3888222A
Application number: US499090A
Authority: US
Inventors: Tsutomu Tomita
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1973-10-02
Filing date: 1974-08-20
Publication date: 1975-06-10
Anticipated expiration: 1992-06-10
Also published as: JPS5060627A

Abstract

A system is provided for optimizing recirculation of exhaust gases in the exhaust system of an internal combustion engine. A flow control valve is inserted in a passage interconnecting an intake system and exhaust system of the engine. Means are provided for actuating the flow control valve in response to vacuum pressure upstream of a throttle valve to increase the flow rate of exhaust gases to be recirculated; and means are provided to actuate the flow control valve to decrease the flow rate of recirculated gases in response to vacuum pressure downstream of the throttle valve.

Description

United States Patent 11 1 Tomita 1 1 EXHAUST GAS RECIRCULATION [75] Inventor: Tsutomu Tomita, Okazaki, Japan [73] Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha, Toyota, Japan [22] Filed: Aug. 20, 1974 [21] Appl. No; 499,090

[30] Foreign Application Priority Data Oct. 2, 1973 Japan 48-110194 [52] US. Cl 123/119 A [51] Int. Cl. F02m 25/06 [58] Field of Search 123/119 A [56] References Cited UNITED STATES PATENTS 3,507,260 4/1970 Walker 123/119 A 3,730,156 5/1973 Sarto 123/119 A 3,739,747 6/1973 Caldwell 123/119 A 3,756,210 9/1973 Kuehl 123/119 A 3,774,583 11/1973 King 123/119 A 3,800,765 4/1974 Thompson 123/119 A 5] June 10, 1975 3,814,070 6/1974 Wertheimer 123/119 A 3,818,880 6/1974 Dawson et a1. 123/119 A 3,834,366 9/1974 Kingsbury 123/119 A Primary Examiner-Wendell E. Burns Assistant Examiner-David Reynolds Attorney. Agent, or Firm-Stevens, Davis, Miller & Mosher [57] ABSTRACT A system is provided for optimizing recirculation of exhaust gases in the exhaust system of an internal combustion engine. A flow control valve is inserted in a passage interconnecting an intake system and exhaust system of the engine. Means are provided for actuating the flow control valve in response to vacuum pressure upstream of a throttle valve to increase the flow rate of exhaust gases to be recirculated; and means are provided to actuate the flow control valve to decrease the flow rate of recirculated gases in response to vacuum pressure downstream of the throttle valve.

3 Claims, 12 Drawing Figures PATENTEDJUN 10 ms SHEEY FIG.

FIG. 2

PATENTEnJuu 10 ms 3. 888.222 SHEET 2 FIG. 5

u m: OE "m FIG. 4B 5 M PRESSURE DOWNSTREAM OF 5 THROTTLE VALVE gg TEAVY LOAD %u.: i

PRESSURE UPSTREAM OF THROTTLE VALVE PATENTEI] JUN 1 0 i975 SHEET CONT- ROLLER I FIG. 7

ZJI' -5 SEE/ 5 5% Lo mzwuimma FIG. 8A

PRESSURE UPSTREAM OF THROTTLE VALVE PRESSURE DOWNSTREAM OF THROTTLE VALVE HEAVY LOAD FIG. 83

FIG. 8C

PRESSURE UPSTREAM OF THROTTLE VALVE EXHAUST GAS RECIRCULATION BACKGROUND OF THE INVENTION The present invention relates to means for handling the exhaust gas of an internal combustion engine, and more particularly to means for recirculating a part of the exhaust gases discharged from the engine to an intake system thereof.

Exhaust recirculation systems have been used in internal combustion engine for the purpose of reducing maximum combustion temperature in order to minimize the production of nitrogen oxides, which are a primary pollutioncausing exhaust component. In one prior art recirculation system, a part of the exhaust gases is injected upstream of a throttle valve in an engine carburetor through a flow control valve. Since the exhaust gases must flow through the carburetor, the gases may cause such problems as corrosion of the carburetor, deposits on the throttle valve which cause sticking. and introduction of moisture in the throttle valve that may produce freezing. It is therefore desirable to provide a recirculation system in which these problems are avoided.

In another prior art system, recirculated gases are injected downstream of the carburetor throttle valve, into the intake system. In this system, the exhaust gases are recirculated due to the difference in vacuum pressure in the intake manifold and the pressure of exhaust gases. Therefore, a large volume of the exhaust gases (large with respect to the volume of intake air) is forced to be recirculated even when the amount of intake air is reduced and it would be desirable to reduce the volume of recirculated exhaust gases. For example, the volume of intake air to an engine is less than under a light load, but vacuum pressure in the intake manifold is increased so that an excessive amount of exhaust gas is recirculated. This causes such malfunctions as breathing, surging, misfiring and other such problems.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an exhaust gas recirculation system for an internal combustion engine which provides optimal volumes of recirculated exhaust gases and which is responsive to the volume of intake air, whereby exhaust gas recirculation is responsive to engine operating conditions.

Briefly stated, there is provided in accordance with the present invention, means for controlling recirculation of exhaust gases responsive to engine operating conditions. A flow control valve is positioned in an exhaust gas passage which interconnects an intake system and an exhaust system in the internal combustion engine. A first diaphragm in the flow control valve is actuated in response to vacuum pressure in the vicinity of the throttle valve, and a second diaphragm is actuated in response to vacuum pressure downstream of the carburetor throttle valve in the intake system.

BRIEF DESCRIPTION OF THE DRAWINGS The means by which the foregoing objects and features of novelty are achieved are pointed out with particularity in the claims forming the concluding portion of the specification. The invention, both as to its organization and manner of operation may be further understood by reference to the following description taken in connection with the following drawings.

Of the drawings:

FIG. 1 is a diagram of a preferred embodiment of an exhaust gas recirculation system constructed in accordance with the present invention,

FIG. 2 is a cross-sectional view ofa flow control valve for inclusion in the system of FIG. 1;

FIG. 3 is a cross-sectional view of another form of flow control valve which may be used in the present invention;

FIGS. 4A and 4B are respective plots of flow control valve first and second diaphragm displacements versus pressure upstream and downstream of the throttle valve respectively, and FIG. 4C is a family of curves illustrating displacement ofa valve member in the recirculation passage under various driving conditions;

FIGS. 5 and 6 are partial sectional views illustrating alternative forms of ports providing a vacuum pressure responsive to the degree of opening of a throttle valve;

FIG. 7 is a diagrammatic representation of another embodiment of a system constructed in accordance with the present invention; and

FIGS. 8A, 8B and 8C are plots similar to those of FIGS. 4A, 4B and 4C which are useful in understanding the operation of the embodiment of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is illustrated a system constructed in accordance with the present invention including an internal combustion engine 1 having an intake manifold 2 connected thereto. An air source in the form of an air cleaner 3 provides air to the intake manifold 2. A venturi throat 4 is provided between the air source 3 and the intake manifold 2. Fuel is provided through a throttle valve 5 positioned between the air source 3 and intake manifold 2. The throttle valve 5 is well-known, and in the present embodiment comprises a pivoted disc. The engine 1 is also provided with an exhaust manifold 6, and an exhaust gas recirculation passage 7 is connected between the intake manifold 2 and exhaust manifold 6. A flow control valve 8 is provided in the recirculation passage 7 for controlling the volume of exhaust gas recirculated back to the intake manifold 2.

Referring to both FIGS. 1 and 2. the flow control valve 8 is described in further detail. A housing 9 includes an intake port 10 communicating with the exhaust manifold 6. A valve member II is provided for flow control in a valve chamber 12 which is a portion of the recirculation passage 7 and which communicates with a discharge port 13. The discharge port l3 communicates with the intake manifold 2. The valve member 11 is engageable with a valve seat 14 provided in the intake port I0 and is movable by a valve stem 15. The valve stem I5 extends through the housing 9 through an air-tight bushing 16 fitted at one surface of the valve chamber II opposite the valve seat 14. The end of the valve stem IS opposite the valve member II extends into a diaphragm box I7 mounted on the hous ing 9. The diaphragm box 17 is divided by a first diaphragm 18 into upper and

lower diaphragm chambers

19 and 20. A coiled spring 21 is disposed in the upper diaphragm chamber (upper meaning remote from the housing 9) 20 and normally biases the first diagraphm 18 toward the housing 9. A second inner diaphragm box 22 is attached to the first diaphragm 18 within the lower chamber I9. The inner diaphragm box 22 is di' vided by a second diaphragm 23 into an inner, lower diaphragm chamber 24 and an inner, upper diaphragm chamber 25. A coiled spring 26 disposed in the inner, lower diaphragm chamber 24 normally biases the second diaphragm 23 upwardly.

The valve stem extends through both the first and second (outer and inner)

diaphragm boxes

17 and 22 and has its upper end secured to the second diaphragm 23, so that movements of both the first and

second diaphragms

18 and 23 may be transmitted by the valve stem 15 to move the valve member 11. A bellows 27 is disposed concentrically with the valve stem 15 such that the

lower diaphragm chambers

19 and 24 do not communicate with each other.

The upper chamber communicates via a port 28 to a three-port solenoid control valve 29 (FIG. 1). A pipe line 30 extends from the valve 29 to a port 31 at a position adjacent the throttle valve 5 and upstream thereof. The port 31 is located such that vacuum pressure at the port 31 is proportional to the degree of opening of the throttle valve 5. The three-port solenoid control valve 29 is actuated by a controller 32 so that the port 28 may be selectively coupled to the pipe line 30 or to a port 33 of the valve 29 communicating with the atmosphere. A temperature sensor 34 responsive to ambient temperature and a sensor 35 responsive to engine cooling water are each connected to the controller 32. A sensor 36 responsive to vehicle speed is also connected to the controller 32.

A port 37 is provided in the lower diaphragm chamber 19 communicating with surrounding atmosphere. An orifice 39 (FIG. 2) is disposed in a port 38 of the second, inner diaphragm box 22, and the port 38 communicates via a flexible pipe 40 with a pipe line 41 extending between the first, outer diaphragm box 19 and a port 42. The port 42 communicates with the intake manifold 2 of the engine 1 downstream of the throttle valve 5. The orifice 39 is positioned to absorb variations in vacuum pressure in the intake manifold 2 which are transmitted to the inner, lower diaphragm chamber 24. Therefore, sudden movement of the valve member 11 in response to sudden variation in vacuum pressure in the intake manifold 2 may be prevented, whereby smooth flow control is ensured. A passage 43 is formed through the second, inner diaphragm box 22 and the first diaphragm 18 and communicates with a flexible pipe 44 which acts as a vent to the surrounding atmosphere to permit free movement of the first diaphragm 18. Therefore, the pressure in the inner, upper diaphragm chamber 25 is equal to atmospheric pressure.

Referring now to FIG. 3, in which the same reference numerals denote elements corresponding to those in FIG. 2, there is illustrated another form of flow control valve which may be used in the system of FIG. 1. In the flow control valve of FIG. 3, a passage 45 is formed in the valve stem 15 in an axial direction and communicates with the surrounding atmosphere through a passage 46 formed in the sealing bushing 16 and valve casing 9. The pipe 44 and passage 43 of the embodiment of FIGv 2 are thus replaced.

OPERATION In operation, the flow control valve 8 controls recirculation of exhaust gases from the exhaust manifold 6 through the recirculation passage 7 to the intake manifold 2. When the throttle valve 5 is open slightly so that an upper end thereof is positioned adjacent the port 31, the vacuum pressure admitted through the port 31 is in proportion to the degree of opening of the throttle valve 5. However, when the upper end of the throttle valve 5 is opened widely, the throttle valve 5 does not significantly affect the pressure at the port 31, and the vacuum pressure admitted through the port 31 is almost equal to the vacuum pressure in the intake manifold 2.

The controller 32 operates in the following manner. The three-port solenoid valve 29 is actuated in response to the output signal of the controller 32 so that the pipe line 28 extending from the flow control valve 8 communicates with the pipe line 30 when atmospheric temperature, temperature of cooling water, and vehicle speed, respectively, are within predetermined ranges. Vacuum pressure is admitted through the port 31, pipe line 30, the three-port valve 29, and the port 28 into the upper diaphragm chamber 20 of the flow control valve so that the first diaphragm 18 is caused to be moved upwardly against the biasing spring 21. Since the first diaphragm 18 is fixed to the second, inner diaphragm box 22, the valve 11 is moved upwardly a distance X1. As a result, the sectional area of the passage of exhaust gases defined by the valve seat 14 and valve member 11 is increased, and the exhaust gases are recirculated.

This description is now related to engine operation. When the engine load is light, the opening of the throttle valve 5 is small, and the vacuum pressure admitted through the port 31 is relatively high, so that the flow control valve 8 tends to increase the flow recirculation rate even when the air intake into the engine 1 is rela tively (with respect to other engine operating conditions) low. However, the vacuum pressure in the intake manifold 2 is transmitted to the diaphragm chamber 24 through the port 42, pipe line 41, the flexible pipe 40 and the orifice 39, so that the second diaphragm 23 is caused to be moved downwardly. Consequently, the valve member 11 decreases the cross-sectional area of the passage for exhaust gases so that the flow of the ex haust gases to be recirculated is further controlled.

However, when engine load is heavy, the opening of the throttle valve 5 is large, so that vacuum pressure in the intake manifold 2 is decreased. Consequently, the downward displacement of the diaphragm 23 is decreased, whereby the valve member 11 serves to in' crease the cross-sectional area of the exhaust gas passage, whereby the rate of flow of exhaust gases through the recirculation passage 7 is increased.

The above operation is further understood with respect to FIGS. 4A, 4B and 4C. The displacement of the first diaphragm 18 is denoted X1; and the displacement of the second diaphragm 23 is denoted X2. X1 and X2 are of opposite signs. The displacement of the valve member 11 from the valve seat 14 is denoted X3. X3 equals X1 plus X2. FIG. 4A is a plot of X1 versus vacuum pressure at the port 31, and FIG. 4B is a plot of X2 versus vacuum pressure at the port 42. FIG. 4C is a plot of a family of curves illustrating in which the ordinate is X3 and the abscissa is time, each curve being plotted for a different level of engine load. For example, the lowest value of X3 is obtained for light engine load, and higher values are obtained for heavier levels of engine load.

When the ambient temperature, cooling water temperature of the engine and/or vehicle speed are higher or lower than a preset range, the three-port solenoid valve 29 is actuated by the controller 32 so that the port 28 communicates with the surrounding atmosphere via the port 33, and atmospheric pressure is introduced into the upper diaphragm chamber 20 of the flow control valve 8. As a result, the valve member 11 is seated against the valve seat 14. Vacuum pressure is admitted through the port 42, pipe line 41, flexible pipe 40 and orifice 39 into the inner, lower diaphragm chamber 24 so that the valve stem moves downwardly. Thus, the force pressing the valve member 11 against the valve seat 14 is increased, strongly cutting off exhaust gas recirculation. Therefore, strong cutoff force is provided even when the vacuum pressure in the intake manifold 2 is stronger than that in the vicinity of the throttle valve 5, which generally occurs in the case of idling or deceleration.

The range of throttle valve 5 opening in which the vacuum pressure admitted through the port 31 is proportional to the opening of the throttle valve 5 in the embodiment of FIG. 1 is small. If it is desired to increase this range, the cross-sectional area of the port 31 may be increased as shown in FIG. 5. Alternatively, as illustrated in FIG. 6, two vacuum pressure admission ports 31 may be provided.

Referring now to FIGS. 7 and 8, in which the same reference numerals denote components corresponding to components in the embodiment of FIG. I, a similar embodiment is disclosed. FIGS. 8A, 8B and 8C are plots corresponding to those of FIGS. 4A, 4B and 4C respectively, but indicating data for the embodiment of FIG. 7. In the embodiment of FIG. 7 a vacuum pressure admission port 31 is opened at the venturi throat 4 rather than in the vicinity of the throttle valve 5. In this embodiment, the vacuum pressure created in the venturi throat 4 is admitted to the port 31, the pipe line 30, the three-port valve 29 and the port 28 into the diaphragm chamber of the flow control valve 8 so that the first diaphragm I8 is caused to move over a distance X], as illustrated in FIG. 8A. Since the vacuum pressure in the venturi throat is high when the volume of air passing therethrough is large, and low when the volume is low, the flow rate of exhaust gases is controlled in proportion to the volume of intake air. This provides for optimal exhaust gas recirculation.

The vacuum pressure in the intake manifold 2 is transmitted to the inner, lower diaphragm chamber 24 so that the second diaphragm 23 is caused to be moved in the direction opposite that of the movement of the first diaphragm 18 over the distance X2. as illustrated in FIG. 8B. The resulting displacement X3 of the valve member I] of the flow control valve 8 is such that the flow rate of the exhaust gases to be recirculated is controlled in response to the volume of intake air into the engine I or in response to engine load. Furthermore, when the engine load is light, the flow rate of exhaust gases to be recirculated may be controlled in response to the vacuum pressure in the intake manifold 2.

In the embodiment of FIG. I, the vacuum pressure under full load in the vicinity of the throttle valve 5 admitted through the port 31 is lower than a predetermined value (FIG. 4A) so that the displacement XI of the first diaphragm I8 is zero. Thus. the valve member II is forced against the valve seat I4, thereby cutting off the recirculation of the exhaust gases. In the embodiment of FIG. 7, however. even under full load. a small vacuum pressure is admitted from the venturi throat 4 through a port 31 so that the first diaphragm I8 is caused to be moved over a short distance X1 (FIG. 8A). Consequently, the complete cutoff by the valve member 11 and the valve seat I4 becomes difficult. In order to overcome this problem in the present invention, a switch 47 is provided connected to detect the opening of the throttle valve 5. The switch 47 is connected to operate so that when the throttle valve 5 is wide open, a signal is connected to the controller 32 to actuate the three-port valve 29 such that the pipe line 28 communicates with atmospheric pressure at the port 33. The valve member 11 is positively seated in this manner as described above.

As hereinabove described. the flow control valve 8 may control the flow rate of the exhaust gases to be recirculated in response to vacuum pressure in the vicinity of the throttle valve 5 or in the venturi throat 4. Under a light load in which the volume of intake air is less, the flow control valve controls the flow rate of exhaust gases to be recirculated in response to vacuum pressure in the intake manifold, thereby preventing the excessive recirculation of exhaust gases. Therefore, optimal exhaust gas recirculation control may be ensured in response to engine operating conditions. Therefore, malfunctions such as breathing, surging, and misfiring are substantially eliminated, engine dfficiency may be remarkably increased, while at the same time reducing production of pollutants. The specification has been written with a view toward enabling those skilled in the art to make modifications in the specific embodiments shown above to provide an exhaust gas recirculation control system constructed in accordance with the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A system for controlling recirculation of exhaust gases from an exhaust manifold to an intake manifold in an internal combustion engine, a throttle valve of the engine being provided upstream of the intake manifold, comprising, in combination:

a recirculation passage connected between the exhaust manifold and the intake manifold;

a valve disposed in said recirculation passage including a valve member disposed such that the volume ofgases flowing in said recirculation passage is proportional to the displacement of said valve memher;

a first diaphragm box, said first diaphragm box being divided by a first diaphragm into a first diaphragm chamber and a second diaphragm chamber, means communicating said first diaphragm chamber with the surrounding atmosphere and means communicating said second diaphragm chamber with said intake manifold upstream of the throttle valve;

a second diaphragm box attached to said first diaphragm, said second diaphragm box being divided by a second diaphragm into a third diaphragm chamber in communication with the surrounding atmosphere and a fourth diaphragm chamber in communication with the intake manifold downstream of the throttle valve, displacement of said first diaphragm in a first direction being caused by vacuum pressure admitted in said second chamber, and displacment of said second diaphragm in an opposite direction being caused by vacuum pressure admitted into said fourth diaphragm chamber; and

means connecting said second diaphragm to said 2. A system according to claim 1 wherein means are valve member such that the degree of opening of provided communicating said second diaphragm chamsaid recirculation passage due to displacement of ber with said intake manifold in the vicinity of the said valve member increases with displacement of throttle valve. said first diaphragm and decrease with displace- 3. A system according to claim 1 wherein means are merit of said second diaphragm, whereby recirculaprovided communicating said second diaphragm chamtion of exhaust gases varies in response to engine her with a venturi throat upstream of the throttle valve. operating conditions.

Claims

1. A system for controlling recirculation of exhaust gases from an exhaust manifold to an intake manifold in an internal combustion engine, a throttle valve of the engine being provided upstream of the intake manifold, comprising, in combination: a recirculation passage connected between the exhaust manifold and the intake manifold; a valve disposed in said recirculation passage including a valve member disposed such that the volume of gases flowing in said recirculation passage is proportional to the displacement of said valve member; a first diaphragm box, said first diaphragm box being divided by a first diaphragm into a first diaphragm chamber and a second diaphragm chamber, means communicating said first diaphragm chamber with the surrounding atmosphere and means communicating said second diaphragm chamber with said intake manifold upstream of the throttle valve; a second diaphragm box attached to said first diaphragm, said second diaphragm box being divided by a second diaphragm into a third diaphragm chamber in communication with the surrounding atmosphere and a fourth diaphragm chamber in communication with the intake manifold downstream of the throttle valve, displacement of said first diaphragm in a first direction being caused by vacuum pressure admitted in said second chamber, and displacment of said second diaphragm in an opposite direction being caused by vacuum pressure admitted into said fourth diaphragm chamber; and means connecting said second diaphragm to said valve member such that the degree of opening of said recirculation passage due to displacement of said valve member increases with displacement of said first diaphragm and decrease with displacement of said second diaphragm, whereby recirculation of exhaust gases varies in response to engine operating conditions.

2. A system according to claim 1 wherein means are provided communicating said second diaphragm chamber with said intake manifold in the vicinity of the throttle valve.

3. A system according to claim 1 wherein means are provided communicating said second diaphragm chamber with a venturi throat upstream of the throttle valve.