GB2031993A

GB2031993A - I.C. engine exhaust gas recirculation control

Info

Publication number: GB2031993A
Application number: GB7930302A
Authority: GB
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1978-09-01
Filing date: 1979-08-31
Publication date: 1980-04-30
Also published as: FR2434930A1; FR2434930B1; DE2935343C2; GB2031993B; DE2935343A1

Abstract

The control vacuum derived downstream or in the vicinity of the mixture throttle valve 13 and acting on the actuators 23, 24 of the exhaust gas recirculation and secondary air valves 15 and 18 is modified by a valve 27 responsive to the venturi vacuum and the vacuum in the secondary air passage 16 downstream of a restriction 19. A valve 38 responsive to the control vacuum adjusts operation of the valve 27 by opening an air bleed to the venturi vacuum chamber 34 of the valve or by forming the restriction in the passage 16, Fig. 2 (not shown). <IMAGE>

Description

SPECIFICATION Exhaust gas recirculation apparatus This application is related to co-pending British Patent Application No. 7907549 (Honda Case 154/102) whose subject matter is incorporated herein by this reference.

This invention relates to exhaust gas recirculation apparatus for internal combustion engines and is particuiarly directed to an improved control system for such apparatus.

It is desimbleto re-circulate exhaust gases to the engine intake passage substantially in proportion to intake flow of air to the engine. This is accomplished by the invention stated in the foregoing Patent Application. However, it is necessary for good driveability and performance of the engine to vary the ratio of exhaust gas recirculation flow to intake flow of air in response to changes of operation of the engine, that is, it is required for obtaining good driveability of the engine to reduce the rate of exhaust gas recirculation during light load operation of the engine and, for reducing NOX emission from the engine, to increase the rate of exhaust gas recirculation during heavy load operation of engine.

According to the present invention there is provided in an internal combustion engine having an intake passage for delivering an air-fuel mixture into the engine, a throttle valve in the intake passage, and an exhaust passage for carrying exhaust gases from the engine, exhaust gas recirculation apparatus comprising a passageway connecting the exhaust passage to the intake passage downstream from the throttle valve for recirculating exhaust gases into said engine, a first control valve in said passageway, an air conduit connecting said intake passage in the vicinity of or downstream from said throttle valve to atmosphere, a second control valve in said air conduit, each of said control valves having a vacuum responsive actuator, said air conduit having a restriction device located between its opening to atmosphere and said second control valve, a vacuum line connected to said intake passage upstream from said throttle valve, a regulating valve responsive to differential pressure between vacuum pressure in said vacuum line and vacuum pressure in said air control line downstream from said restriction device, a control pipe system connecting said vacuum responsive actuators to said intake passage near said throttle valve, means whereby said regulating valve acts through said control pipe system to operate said vacuum responsive actuators for said control valves, and an air induction valve responsive to vacuum pressure in said control pipe system and operatively positioned to change said differential pressure.

Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic view showing one embodi mentofthis invention; and Figure 2 is a view similar to Figure 1 showing a modification.

Referring to the drawings, the engine 10 has an intake passage 11 for an air-fuel mixture, and a passage 12 for exhaust gases. A throttle valve 13 is provided in the intake passage 11. A passageway 14 connects the exhaust passage 12 to the intake passage 11 at a location downstream from the throttle valve 13, for recirculating exhaust gases into said engine 10. An exhaust gas recirculation control valve 15 is positioned in this passageway 14.

An air conduit 16 is connected to said intake passage 11 at a location downstream from said throttle valve 13 and has an opening 17 to atmosphere. An air control valve 18 is mounted in said air conduit 16.

A fixed or variable restriction 19 is placed in the air conduit 16 at a location between the air control valve 18 and the opening 17 to atmosphere. An air control line 21 is connected to the air conduit 16 downstream with respect to said restriction 19. Each of the control valves 15 and 18 is provided with a vacuum responsive actuator 23, 24, respectively. Each of these actuators is connected to a control pipe system 26, which is in turn connected to a second vacuum outlet 25 in the intake passage 11 downstream from the throttle valve 13 or a second vacuum outlet 26a in the vicinity of the throttle valve 13 above the idle position thereof.

A regulating valve 27 is provided with a movable diaphragm member 28 having a central non-flexible portion 29. An open ended tube 31 forming a part of the control pipe system 26 is closed and opened by contact with the central non-flexible portion 29 of the diaphragm member 28. A variable opening 32 is thus formed between the open ended tube 31 and the central portion 29 of the diaphragm member 28. The chamber 33 above the diaphragm member 28 of the regulating valve 27 is subjected to pressure in the air control line 21. The chamber 34 below the diaphragm member 28 is connected to a tube 35 which in turn is connected to a first vacuum outlet 30 in the carburetor venturi section 36.

In operation, the operating vacuum generated at the second vacuum outlet 25 in the intake passage 11 acts on the vacuum responsive actuators 23 and 24 to open the exhaust gas recirculation control valve 15 and the air control valve 18. Exhaust gases from the exhaust passage 12 are then circulated backto the intake passage 11. The vacuum intensity in the air conduit 16 between the air control valve 18 and the orifice 19 acts on the regulating valve 27 to cause the central portion 29 of the diaphragm 28 to lift away from the valve port 32. Also the vacuum intensity in the first vacuum outlet 30 introduced into the second chanber 34 through the tube 35 acts on the regulating valve 27 to cause the diaphragm 28 to close the valve port 32.Thus, the action of the regulating valve 27 is regulated by means of both vacuum intensities in the air conduit 16 between the air control valve 18 and the orifice 19 and the first vacuum outlet 30 in the venturi portion. As the vacuum intensity at the first vacuum outlet 30 increases, the regulating valve 27 closes and acts to raise the vacuum pressure in the vacuum responsive actuators 23 and 24, with the result that the rate of flow of exhaust gas circulation also increases.

From the foregoing description, it wili be understood that the operating vacuum from the intake passage acting on a control valve is regulated by a regulating valve placed in a passageway connecting the intake passage to the atmosphere. The regulating valve responds in proportion to the engine load and therefore the control of introduction of gas is accomplished in a direct manner. The exhaust gas recirculation control valve and the air control valve operate synchronously with each other so that by measuring the rate of flow through the orifice leading to atmosphere and selecting the flow characteristics of the air control valve on the basis thereof, various rates of the additional gas flow introducted into an engine can be established.

In accordance with this invention, a branch 22 from the air conduit 16 leads to a chamber 20 below the flexible diaphragm 40 of an air induction valve 38. The other side of the diaphragm 40 is subjected to vacuum pressure in the control pipe 26. A restriction 37 is placed in the control pipe system 26 between the second vacuum outlet 25 and the actuators 23,24 and 28. The air induction valve 38 controls flow of air through the branch 22 into the tube 35, the extent of opening of the valve 38 being controlled by differential pressure across the diaphragm 40.

In operation, the air induction valve 38 remains closed when the differential pressure across the diaphragm 40 is low. The intensity of the vacuum in the tube 35 remains high, thereby urging the diaphragm 28 in the regulating valve 27 to move in a direction to close the openings 32. Leakage from the tube 31 into the chamber 34 is thus restricted, with consequent increase of intensity of the vacuum in the control pipe system 26. The recirculation control valve 15 then moves toward open position to increase the rate of exhaust gas recirculation through the passage way 14 and into the intake passage 11 of the engine 10.

When the intensity of the vacuum in the control pipe system 26 increases, the differential pressure across the diaphragm 20 increases to move the air induction valve 38 toward open position. Atmospheric air then flows from the branch 22 through the valve 38 and into the tube 35, thereby reducing the intensity of the vacuum in the chamber 34. This causes the central portion 29 of the diphragm 28 to move away from the tube 31 to increase the size of the opening 32. This in turn reduces the intensity of the vacuum in the control pipe system 26 with the resu It that the recirculation control valve 15 is moved toward closed position. This reduces the flow of exhaust gas through the passageway 14 into the intake passage 11 of the engine 10.

In the modified form of the invention shown in Figure 2, the parts and connections are the same as that previously described except that the air induction valve 38 controls flow of atmospheric air from air inlet 39 into the air conduit 16a upstream from the air control valve 18.

The differential pressure across the diphragm 28 is thus varied by varying the vacuum intensity of the air in the chamber 33, instead of varying the vacuum intensity in the chamber 34, as in the device of Figure 1.

Claims

1. In an internal combustion engine having an intake passage for delivering an air-fuel mixture into the engine, a throttle valve in the intake passage, and an exhaust passage for carrying exhaust gases from the engine, exhaust gas recirculation apparatus comprising a passageway connecting the exhaust passage to the intake passage downstream from the throttle valve for recirculating exhaust gases into said engine, a first control valve in said passageway, an air conduit connecting said intake passage in the vicinity of or downstream from said throttle valve to atmosphere, a second control valve in said air conduit, each of said control valves having a vacuum responsive actuator, said air conduit having a restriction device located between its opening to atmosphere and said second control valve, a vacuum line connected to said intake passage upstream from said throttle valve, a regulating valve responsive to differential pressure between vacuum pressure in said vacuum line and vacuum pressure in said air control line downstream from said restriction device, a control pipe system connecting said vacuum responsive actuators to said intake passage near said throttle valve, means whereby said regulating valve acts through said control pipe system to operate said vacuum responsive actuators for said control valves, and an air induction valve responsive to vacuum pressure in said control pipe system and operatively positioned to change said differential pressure.

2. An engine as claimed in claim 1, in which said regulating valve has a variable opening for bleeding said control pipe system into said vacuum line.

3. An engine as claimed in claim 1 or 2, in which the air induction valve is operatively connected to change the intensity of the vacuum in said vacuum line by bleeding atmospheric air into it.

4. An engine as claimed in claim 1 or 2, in which the air induction valve is operatively connected to vary the air pressure supplied to the regulating valve.

5. An internal combustion engine having exhaust gas recirculation apparatus substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.