US3885536A

US3885536A - Recirculating exhaust gas load initiated control (relic)

Info

Publication number: US3885536A
Application number: US408953A
Authority: US
Inventors: John R Marshall
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1973-10-23
Filing date: 1973-10-23
Publication date: 1975-05-27
Anticipated expiration: 1992-05-27
Also published as: GB1451853A; JPS5073030A; JPS531418B2; AU7370374A; CA1021651A; DE2449431A1

Abstract

The engine has a duct connecting the gases in the exhaust gas crossover passage to the intake manifold, the duct normally being closed by a valve that is opened by manifold vacuum modulated as a function of carburetor throttle blade opening (EGR port vacuum) and connected to the valve by a vacuum regulator having an airbleed that is controlled by manifold vacuum so that the gas recirculating valve opening signal force varies with load during part throttle operations and idle to prevent recirculation during engine idle and cruising and wide-open throttle operations while providing controlled operation in the engine accelerating range between.

Description

n 5] May 27, 1975 l l REClRCULATlNG EXHAUST GAS LOAD lNlTIATED CONTROL (RELIC) John R. Marshall, Novi, Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[75] Inventor:

Primary Examiner-Charles J. Myhre Assistant E.taminerDaniel .l.. OConnor Attorney, Agent, or FirmRolbert E. McCollum; Keith L. Zerschling [57] ABSTRACT The engine has a duct connecting the gases in the exhaust gas crossover passage to the intake manifold, the duct normally being closed by a valve that is opened by manifold vacuum modulated as a function of carburetor throttle blade opening (EGR port vacuum) and connected to the valve by a vacuum regulator having an air-bleed that is controlled by manifold vacuum so that the gas recirculating valve opening signal force varies with load during part throttle operations and idle to prevent recirculation during engine idle and cruising and wide-open throttle operations while providing controlled operation in the engine accelerating range between.

6 Claims, 3 Drawing Figures RECIRCULATING EXHAUST GAS LOAD INITIATED CONTROL (RELIC) This invention relates, in general, to an internal combustion engine. More particularly, it relates to a system for controlling the recirculation of exhaust gases back into the engine through the intake manifold.

Devices are known for recirculating a portion of the engine exhaust gases back through the engine to control the emission of unburned hydrocarbons and lower the output of oxides of nitrogen. These devices have included valving to prevent recirculation of the exhaust gases at undesired times and generally are controlled by movement of the carburetor throttle valve so that recirculation is prevented during engine idle and wideopen throttle operations. This is desirable because at engine idle, exhaust gas scavenging is inefficient, while at wide-open throttle position, maximum power is limited by the availability of oxygen.

It is an object of this invention to provide an exhaust gas recirculation (EGR) system of the above type that affords a finer control of the recirculation of gases back into the engine by means of a regulating valve that schedules EGR flow in proportion to load during idle speed and part throttle operation.

It is a further object of the invention to provide an EGR valve for opening and closing a duct containing exhaust gases for their recirculation into an engine, the valve being moved to open the duct by a signal force that is determined by the level of manifold vacuum in a port (EGR port) traversed by the carburetor throttle valve, and controlled by a valve that regulates the EGR signal force by means of an air bleed to vary the signal force and EGR flow in proportion to engine load as indicated by manifold vacuum changes.

Other objects, features and advantages of the invention would become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating the preferred embodiments thereof, wherein;

FIG. 1 is a cross-sectional view of a portion of an internal combustion engine and associated carburetor embodying the invention;

FIG. 2 is a cross-sectional view taken on a plane indicated by and viewed in the direction of the arrows 2-2 of FIG. I; and,

FIG. 3 is a modification.

FIG. 1 illustrates a portion of one-half of a twobarrel carburetor of a known downdraft type. It has an air horn section 12, a main body portion 14, and a throttle body 16, joined by suitable means not shown. The carburetor has the usual air/fuel induction passages 18 open at their upper ends 20 to fresh air from the conventional air cleaner, not shown. The passages 18 have the usual fixed area venturies 22 cooperating with booster venturies 24 through which the main supply of fuel is induced, by means not shown.

Flow of air and fuel through induction passages 18 is controlled by a pair of throttle valve plates 26 each fixed on a shaft 28 rotatably mounted in the side walls of the carburetor body.

The throttle body 16 is flanged as indicated for bolting to the top of the engine intake manifold 30, with a spacer element 32 located between. Manifold has a number of vertical risers or bores 34 that are aligned for cooperation with the discharge end of the carburetor induction passages 18. The risers 34 extend at right angles at their lower ends 36 for passage of the mixture out of the plane of the figure to the intake valves of the engine.

The exhaust manifolding part of the engine cylinder head is indicated partially at 38, and includes an exhaust gas crossover passage 40. The latter passes from the exhaust manifold, not shown, on one side of the engine to the opposite side beneath the manifold trunks 36 to provide the usual hot spot" beneath the carburetor to better vaporize the air/fuel mixture.

As best seen in FIG. 2, the spacer 32 is provided with a worm-like recess 42 that is: connected directly to cross-over passage 40 by a bore 44. Also connected to passage 42 is a passage 46 alternately blocked or connected to a central bore or passage 48 communicating with the risers 34 through a pair of ports 50. Mounted to one side of the spacer is a cup shaped boss 52 forming a chamber 54 through which

passages

46 and 48 are interconnected.

As described above, it is necessary and desirable to provide some sort of control to prevent the recirculation of exhaust gases at undesirable times. For this purpose, passage 46 normally is closed by a valve 56 that is moved to an open position by a servo 58. The servo includes a hollow outer shell 64 containing an annular flexible diaphragm 66. The latter divides the interior into an air chamber 68 and a signal vacuum chamber 70. Chamber 68 is connected to atmospheric pressure through a vent 72, while chamber 70 is connected to a vacuum signal force through a line 74. The stem of valve 56 is fixed to a pair of retainers 76 secured to diaphragm 66. They serve as a seat for a compression spring 77 normally biasing the valve to its closed position. The stem slidably and sealingly projects through a plate 78 closing chamber 54.

As shown in FIG. 1, the carburetor contains a manifold vacuum sensing port 80 and an exhaust gas recirculating (EGR) port 82. The latter is located above the port 80 and above the closed position of throttle valve 26 to be traversed by the edge of the throttle valve as it moves open. The pressure in. port 82 thereby varies from atmospheric to the manifold vacuum level as a function of the opening of throttle valve 28. Port 82 is connected through a vacuum regulating device 84 in passage 74 to servo 58.

Device 84 in this case is manifold vacuum controlled to regulate the flow of EGR vacuum to servo 58 in proportion to engine load. More specifically, device 84 includes a vacuum switch 86 in a series with an EGR signal vacuum regulator 88 to bleed EGR vacuum as a function of throttle valve position when the manifold vacuum is above a certain level. As shown schematically in FIG. 1, both the vacuum switch 86 and vacuum regulator 88 are constructed alike. They consist of

outer housings

90, 90 divided into two

chambers

92, 92 and 94, 94' by annular

flexible diaphragms

96, 96. The lower shell portions are formed with two

passages

98, 98 and 100, 100. The latter passages are formed at their chamber ends with

conical seats

102, 102 for cooperation with the

diaphragms

96, 96 which act as regulating valves.

Compression springs

104, 104 are seated between spacers 106, 1.06 riveted to the diaphragms and adjustable stops 108, 108'.

The vacuum switch 86 controls the bleed of air to the vacuum regulator 88 as a function of manifold vacuum level. Chamber 92 is connected by a passage 110 to manifold vacuum port 80. Lower passage 98 is vented to atmosphere, while passage 100 is connected by a passage 112 to lower passage 98 of the vacuum regulator 88. If the force of spring 104 is chosen, for example, to be such as to keep diaphragm 96 against seat 102 until the manifold vacuum rises above 7 inches Hg., then the diaphragm will block off the bleed of air into passage 100 for all vacuum levels below 7 inches Hg.

The vacuum regulator 88 regulates the EGR signal vacuum to the EGR valve 56 by at times bleeding it, with the air from the vacuum switch 86. In this case, the EGR vacuum in port 82 is connected by a line 114 through

parallel lines

116 and 118 to the upper chamber 92' and lower passage 100 respectively, of the regulator valve, as well as to the line 74 leading to the EGR valve. The spring 104 in this case would be chosen to have a force such that would maintain the diaphragm 96' seated to block passage 100 below say 3 inches Hg., EGR vacuum force, for example.

In operation, during engine idle speed and deceleration conditions, the throttle valve is closed, so no EGR flow occurs because the EGR port is at substantially atmospheric pressure. This transmitted through line 74 maintains the EGR valve 56 closed. While manifold vacuum is high, above 7 inches Hg, opening of passage 100 to the air in passage 98 is ineffective since the lower chamber 94 in the vacuum regulator is already at atmospheric pressure.

Assume now that the throttle valve 26 is moved to a slightly open position for light accelerations of the vehicle. The manifold vacuum most likely will not decay below a vacuum level of 7 inches Hg., therefore, the vacuum switch 86 will remain open, bleeding air in passage 98 into the open end of passage 100 to the air passage 98 of the vacuum regulator 88. At this time, the EGR vacuum in port 82 will be modulating the manifold vacuum as the throttle valve traverses the EGR port. Assume, therefore, that the EGR vacuum at this time is above 3 inches Hg. This then causes the diaphragm 96' to move off the conical seat 102 and permit bleed of the EGR vacuum level in passage 100 by the air in passages 98'. This bleed will decay the EGR vacuum signal force to the EGR valve 56 until an equilibrium position is obtained in which the forces of the EGR vacuum plus the spring force acting on the upper side of diaphragm 96 are sufficient to seat it against the conical seat 102. The EGR vacuum will then regulate at the lower vacuum force level, thus providing a small amount of EGR flow and one corresponding essentially to the light load operation.

During heavy vehicle accelerations, movement of throttle valve past the EGR port to a nearly wide open position will decay the manifold vacuum to a level below 7 inches Hg. Accordingly, the vacuum switch 86 will close, by the diaphragm 96 seating against the conical end of passage 100, so that air no longer is bled into line 112. Accordingly, the EGR vacuum in

lines

116 and 118 will be at their full value, resulting in the EGR valve opening to its maximum flow capacity, which is desired during this condition of operation.

During wide open throttle conditions, the movement of the throttle valve to a nearly vertical position will generally decay the manifold vacuum to nearly zero. This also will put the EGR port at nearly atmospheric pressure, which will then close the EGR valve 56 even though the switch 86 is closed. This condition will continue for so long as it takes the manifold vacuum to recover and begin building up again, at which point the EGR vacuum will then be at its full value to the EGR valve 56 until it reaches a level above 7 inches Hg. At this point, switch 86 will open and begin regulating the EGR signal vacuum to the EGR valve 56. While FIG. 1 illustrates the vacuum switch 86 and vacuum regulator 88 somewhat schematically, FIG. 3 shows a preferred integrated and more to scale construction. More specifically, the combined vacuum switch and vacuum amplifier are housed within a three piece outer housing 120 having a central partition 122 dividing the housing into two

main sections

124 and 126. A first annular flexible diaphragm 128 subdivides the chamber 126 into a pair of

chambers

130 and 132. Chamber 130 is connected to manifold vacuum through a passage 134 connected to intake manifold port 80. Chamber 132 is connected or vented to air at atmospheric pressure through a passage 136. The vacuum regulator portion 124 of the housing likewise is further subdivided by an annular flexible diaphragm 138 into two

chambers

140 and 142. The chamber 140 is connected by a passage 144 to the EGR vacuum port 82 as well as to the EGR valve line 74. Chamber 142 is connected to the vent passage 136 by a pair of intersecting passages 146 and 148 through the center partition 122. A compression spring 150 is seated between the diaphragm 128 and an adjustable stop 152 slidable in the shell 120. Likewise, a compression spring 154 is seated between the diaphragm 138 and a second adjustable stop 156 slidable in the housing 120. The force of spring 150 would be chosen so as to be comparable to the force of spring 104 of the vacuum switch, and, in that respect, would be approximately equal to 7 inches Hg. The force of spring 154, likewise would be similar to that of the force of spring 104' of the vacuum regulator, and would be approximately equal to 3 inches Hg.

The spring 150 biases the diaphragm 128 against the open end of the passage 148 in partition 122; thus, when seated, blocking the bleed of air into the annular chamber 142. Likewise, the spring 154 biases the diaphragm 138 against the opposite side of the partition 122, which in this case is closed off. A through port 158 in provided through the diaphragm retainer.

The operation is essentially the same as previously described. ln brief, below a manifold vacuum level of 7 inches Hg., such as during heavy accelerations, the spring 150 will maintain the diaphragm 128 seated against the inlet end of passage 148 to thus block flow of air into the chamber 142. With the throttle valve positioned for heavy accelerations, the EGR vacuum in passage 144 will move the diaphragm 138 away from the center partition 122. However, since there is no bleed of air in chamber 142, the EGR vacuum will remain at full value and the full force of the EGR port vacuum will be applied to the EGR valve 56. Accordingly, the maximum flow of EGR will occur.

During lighter vehicle accelerations, when the manifold vacuum does not decay to below a 7 inches Hg. level, the diaphragm 128 will be moved off the center partition allowing air to flow into chamber 142. Thus, when EGR vacuum moves the diaphragm 138 against the force of spring 154, the opening of passage 158 will cause a bleed down of the EGR vacuum by the air in chamber 142 so that the EGR vacuum signal to the EGR servo 58 will be less and in proportion to the load so that a low EGR flow will occur.

From the foregoing, it will be seen that the invention provides an EGR flow rate during part throttle operations that is nearly proportional to engine load so that during maximum accelerations a maximum flow capacity is obtained, whereas during light load operation, only little flow is provided. Likewise, it will be seen that the invention prevents large flow when wide open throttle conditions of operation occur because at that time the EGR port vacuum is nearly zero.

While the invention has been described and illustrated in its preferred embodiments, it will be clear to those skilled in the arts to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention. For example, it will be clear that the spring forces of both the vacuum switch and the vacuum regulator can be changed as desired to vary the operating characteristics of the switch and regulator. Also, while the EGR port is shown as located above the closed position of the throttle valve, it will be clear that the port could be located as desired either to straddle the edge of the throttle valve in a closed position, for example, or be located further above the throttle valve than shown so as to delay a buildup of EGR port vacuum until the throttle valve has opened substantially. Other positions may also be possible within the scope of the invention.

1 claim:

1. An exhaust gas recirculating system in an internal combustion engine having intake and exhaust manifolds, a carburetor induction passage, a throttle valve controlling flow through the passage, the system comprising, a duct connecting the exhaust gases to the engine intake manifold, an exhaust gas recirculation (EGR) valve normally closing the duct to prevent recirculation and movable to an open position by a signal vacuum connected thereto, the induction passage containing an exhaust gas recirculating (EGR) port located relative to the throttle valve so as to be traversed by the throttle valve edge during opening throttle valve movements so as to be at essentially atmospheric pressure at closed throttle positions with decreases in pressure level in proportion to the progressive opening of the throttle valve upon exposure of the port to manifold vacuum until EGR port vacuum reaches the level of manifold vacuum, conduit means operatively connecting EGR port signal vacuum to the valve to move the same, a vacuum regulator in the conduit means for regulating the EGR signal vacuum level including a source of air at ambient or atmospheric pressure connected to the regulator for variably bleeding the EGR signal vacuum to a regulated level, and switch means for shutting off or permitting the flow of air to the regulator to terminate or permit the regulating function of the regulator.

2. An exhaust gas recirculating system in an internal combustion engine having intake and exhaust manifolds and a carburetor induction passage having a throttle valve controlling flow through the passage, the system comprising, a duct connecting the exhaust gases to the engine intake manifold, an exhaust gas recirculation (EGR) valve normally closing the duct to prevent recirculation and movable to an open position by a signal vacuum connected thereto, and modified manifold vacuum responsive means operable to provide a signal vacuum to the valve that varies from one pressure level at closed or nearly closed throttle positions to manifold vacuum levels near wide open throttle positions in response to movement of the throttle valve and changes in manifold vacuum to provide an EGR flow rate that varies essentially in proportion to the load during part load operation, the induction passage containing an EGR port located relative to the throttle valve so as to be traversed by the edge of the throttle valve upon opening movements of the throttle valve so as to be at essentially atmospheric pressure at closed throttle positions with decreases in pressure level in proportion to the progressive opening of the throttle valve until EGR port vacuum reaches the level of manifold vacuum, conduit means operatively connecting the EGR port signal vacuum to the valve to move the same, the vacuum responsive means including a vacuum regulator to which air at ambient or atmospheric pressure is connected by second conduit means for at times bleeding the EGR vacuum level, including an air bleed valve means in the second conduit means acted upon by manifold vacuum for movement above a predetermined manifold vacuum force level to supply air to the regulator to regulate at times the EGR signal vacuum level acting on the EGR valve.

3. A system as in claim 1, the switch means being moved by manifold vacuum above a predetermined level applied thereto to a position permitting flow of air to the regulator.

4. A system as in claim 1, the regulator including an atmospheric air passage, a flexible diaphragm type vacuum valve having spring means biasing the diaphragm against the air passage closing the same, means applying EGR vacuum to the diaphragm to move the vacuum valve to open the air passage and bleed down the EGR vacuum, the switch means including a second flexible diaphragm valve, other means supplying air to the air passage, second spring means biasing the second diaphragm valve to a position blocking the other means, the second diaphragm valve being responsive to manifold vacuum above the force of the second spring means to move the second diaphragm valve to open the other means and permit airflow to the air passage for control by EGR vacuum to regulate EGR signal vacuum.

5. A system as in claim 1, the regulator including an air passage having an inlet and outlet, 21 first valve that is spring movable to a first position against the air outlet blocking the same and blocking EGR signal vacuum flow from one side of the valve to the other, the first valve being responsive to EGR signal vacuum applied to the one side of the first valve to move the first valve to a second position unblocking the air outlet and permitting flow of air to the one side to decay the EGR signal vacuum, a second valve spring movable against the air inlet to block the same and movable by a predetermined level of manifold vacuum applied thereto to a second position opening the inlet to permit flow of air to the outlet, whereby EGR signal vacuum level to the EGR valve is regulated as a function of manifold vacuum above the predetermined level effecting the decay of EGR port vacuum to vary essentially proportional to load at part throttle operations.

6. A system as in claim 1, the vacuum regulator including a first flexible diaphragm exposed to a chamber pressure on one side and EGR port vacuum on the other side, a second flexible diaphragm exposed to manifold vacuum on one side and to a source of air on the other side, the diaphragms both being spring seated to block the flow of air to the chamber past the first and second diaphragms to bleed the EGR port vacuum, movement of the second diaphragm to an unseated position by manifold vacuum above a predetermined level portion to load during accelerations, the unseating of and the first diaphragm by EGR port vacuum above a the first diaphragm by EGR port vacuum to the EGR predetermined level regulating the EGR port vacuum valve.

by bleeddown by the air to vary the EGR flow in pro-

Claims

5. A system as in claim 1, the regulator including an air passage having an inlet and outlet, a first valve that is spring movable to a first position against the air outlet blocking the same and blocking EGR signal vacuum flow from one side of the valve to the other, the first valve being responsive to EGR signal vacuum applied to the one side of the first valve to move the first valve to a second position unblocking the air outlet and permitting flow of air to the one side to decay the EGR signal vacuum, a second valve spring movable against the air inlet to block the same and movable by a predetermined level of manifold vacuum applied thereto to a second position opening the inlet to permit flow of air to the outlet, whereby EGR signal vacuum level to the EGR valve is regulated as a function of manifold vacuum above the predetermined level effecting the decay of EGR port vacuum to vary essentially proportional to load at part throttle operations.

6. A system as in claim 1, the vacuum regulator including a first flexible diaphragm exposed to a chamber pressure on one side and EGR port vacuum on the other side, a second flexible diaphragm exposed to manifold vacuum on one side and to a source of air on the other side, the diaphragms both being spring seated to block the flow of air to the chamber past the first and second diaphragms to bleed the EGR port vacuum, movement of the second diaphragm to an unseated position by manifold vacuum above a predetermined level and the first diaphragm by EGR port vacuum above a predetermined level regulating the EGR port vacuum by bleeddown by the air to vary the EGR flow in proportion to load during accelerations, the unseating of the first diaphragm by EGR port vacuum to the EGR valve.