Exhaust gas recirculation valve

[57] ABSTRACT

A diaphragm operated control valve assembly, responsive either to vacuum conditions at an induction passage slot traversed by the edge of the throttle or to exhaust back pressure, controls recirculation of exhaust gases from the intake manifold exhaust crossover passage to the intake manifold induction passages.

[56] References Cited

Claims, 5 Drawing Figures

UNITED STATES PATENTS

1,069,785 8/1913 Ulmer, Jr......................... 123/188 P

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PATENTED OCT 21973

SHEET 1 OF 3

3.762.384

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INVENTORS &amp;limrd0.ihu ^BY CmstCHinrt

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PATENTED OCT 21973

3,762,384

SHEET 2 OF 3

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PATENTED® 21973

3.762.384

SHEET 3 OF 3

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3,762,384

EXHAUST GAS RECIRCULATION VALVE RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 90,399, filed Nov. 17, 1970 and now abandoned.

SUMMARY OF THE INVENTION

This invention relates to exhaust gas recirculation and more particularly to a novel valve assembly designed to control recirculation of exhaust gases. Important features of the valve design reduce conduction of exhaust gas heat from the valve area to the diaphragm and prevent escape of exhaust gas past the valve stem.

The details as well as other objects and advantages of this invention are shown in the drawings and set forth in the description of the preferred embodiments.

SUMMARY OF THE DRAWINGS

FIG. 1 is a top plan view of a V-8 engine intake manifold containing induction passages and an exhaust crossover passage, together with a carburetor spacer plate containing an exhaust gas recirculation passage and carrying an exhaust gas recirculation control valve assembly;

FIG. 2 is a transverse sectional view taken generally along line 2—2 of FIG. 1, showing the induction passage plenums and the exhaust crossover passage in the manifold and the inlet to the exhaust gas recirculation passage in the spacer plate, to which a carburetor throttle body has been added;

FIG. 3 is an enlarged sectional view taken along line 3—3 of FIG. 1, showing the details of the vacuum operated exhaust gas recirculation control valve assembly;

FIG. 4 graphically illustrates the vacuum signal created at different induction air flow rates and induction vacuums and used to operate the FIG. 3 valve assembly; and

FIG. 5 is an enlarged sectional view, similar to that of FIG. 3, showing the details of the back pressure operated exhaust gas recirculation control valve assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 2, an intake manifold 10 has a pair of vertical primary riser bores 12 and 14 and a pair of vertical secondary riser bores 16 and 18. Riser bores 12 and 16 open to an upper horizontal plenum 20 connected forwardly (leftwardly as viewed in FIG. 1) to a pair of transverse runners 22 and 24 and connected rearwardly (rightwardly as viewed in FIG. 1) to another pair of transverse runners 26 and 28. Similarly, riser bores 14 and 18 open to a lower horizontal plenum 30 connected forwardly to a pair of transverse runners 32 and 34 and rearwardly to another pair of transverse runners 36 and 38.

An exhaust crossover passage 40 extends transversely from the left-hand side of manifold 10 beneath plenums 20 and 30 and receives a portion of the exhaust gases discharged from the engine combustion chambers. Exhaust crossover passage 40 may be blocked at the right-hand side if desired.

An insert plate 42 is secured on manifold 10 and has primary riser bores 44 and 46 and secondary riser bores 48 and 50 which meet, respectively, riser bores 12, 14, 16, 18 of manifold 10.

A carburetor 52 is secured on insert plate 42 and has primary throttle bores 54 and 56 which meet, respectively, primary riser bores 44 and 46 of insert plate 42. Carburetor 52 also has secondary throttle bores (not shown) which meet secondary riser bores 48 and 50 of insert plate 42.

A bore 58 in manifold 10 leads upwardly from exhaust crossover passage 40 to the first portion 60 of an exhaust recirculation passage formed in insert plate 42. The first portion 60 of the exhaust recirculation passage leads through a control valve 62 to a second portion 64 of the exhaust recirculation passage. This second portion 64 divides into a pair of branches 66 and 68 which lead to the primary riser bores 44 and 46 in insert plate 42.

It should be appreciated that both portions 60 and 64 of the exhaust recirculation passage may be integrated in manifold 10 rather than in separate insert plate 42.

One embodiment of control valve 62 is shown in detail in FIG. 3. It comprises a base member 70 having an upper wall 72, a peripheral wall 74, and a lower wall 76 which define a chamber 78. Chamber 78 has an inlet 80 opening from the first portion 60 of the exhaust gas recirculation passage and an outlet 82 opening to the second portion 64 of the exhaust gas recirculation passage. A valve seat member 84 is threadedly secured in inlet 80 in a tamperproof location.

A valve pintle 86 has a generally conical contour cooperating with valve seat 84 to provide a variable area for flow of recirculated exhaust gases. Valve pintle 86 is retained on a valve stem 88 by staking the end 90 of stem 88. Stem 88 extends upwardly through an opening 92 in the upper wall 72 of base member 70.

A housing member 94 has a central portion 96 provided with an opening 98 receiving valve stem 88.

An intermediate member 100 has an annular, downwardly concave, dished portion 102 disposed between the central portion 96 of housing member 94 and the upper wall 72 of base member 70. An asbestos insulating disc 104 is received in the dished portion 102 of intermediate member 100 and reduces conduction of exhaust heat from base member 70 to housing member 94.

Intermediate member 100 also has a central, downwardly concave, cupped portion 106 with a central opening 108 receiving valve stem 88. A plurality of graphited asbestos sealing discs 110 and a steel washer 112 are received in the cupped portion 106 of intermediate member 100 and engage valve stem 88 to guide stem 88 and to reduce air flow into chamber 78 through openings 108 and 92.

Housing member 94 has an outer rim 114 supported by three outwardly and upwardly extending spokes 116 (only two of which appear in the figure). Each spoke 116 has a slightly raised rib 117 for reinforcement. Spokes 116 provide a minimized path for heat conduction from the central portion 96 of housing member 94 to the rim 114 of housing member 94.

A cover member 118 has a rim 120 secured about rim 114 of housing member 94. A diaphragm 122 is clamped between rims 114 and 120 to define an enclosure 123 between diaphragm 122 and cover 118. Diaphragm 122 carries valve stem 88. A spring 124 exerts a downward bias on diaphragm 122, valve stem 88, and valve pintle 86 to engage valve pintle 86 with valve seat 84.

3,762,384

A hose 126, secured to a fitting 128 opening from chamber 123, forms a vacuum signal conduit extending to carburetor 52 as shown in FIG. 2. A passage 130 within carburetor 52 connects hose 126 with a slot 132 opening from throttle bore 56. Slot 132 is disposed adjacent and extends above and slightly below the upstream edge 134 of the carburetor throttle 136 which is rotatably disposed in throttle bore 56 on a throttle shaft 138.

In operation, an air-fuel mixture, or air alone in the case of a fuel injected engine, will be drawn into the engine through the induction passage defined by carburetor throttle bores 54 and 56, insert plate riser bores 44, 46, 48, 50 and manifold riser bores 12, 14, 16 and 18, manifold plenums 20 and 30, and manifold runners 22, 24, 26, 28, 32, 34, 36, 38. When throttles 136 and 137 are closed as shown in FIG. 2, the substantially atmospheric pressure in throttle bore 56 above throttle 136 bleeds into the upper portion of slot 132 and reduces the induction vacuum sensed by the lower portion of slot 132. The resultant vacuum signal delivered through passage 130 and hose 126 to chamber 123 is insufficient to raise diaphragm 122 against the bias of spring 124. Valve pintle 86 is thereby maintained in engagement with valve seat 84 to prevent recirculation of exhaust gases through control valve chamber 78.

As throttles 136 and 137 are opened to a part throttle position, the upstream edge 134 of throttle 136 traverses slot 132 and a greater portion of slot 132 is subjected to the induction vacuum below throttle 136 while a lesser portion of slot 132 is subjected to the substantially atmospheric pressure above throttle 136. The resultant vacuum signal transferred through passage 130 and hose 126 to chamber 123 raises diaphragm 122 against the bias of spring 124. Valve pintle 86 is then lifted away from valve seat 84 to recirculate exhaust gases from exhaust crossover passage 40 through bore 58, passage 60, inlet 80, chamber 78, outlet 82, passage 64, and branches 66 and 68 to riser bores 44 and 46.

The rate at which exhaust gases are recirculated through control valve 62 is determined by the contour of pintle valve 86 and by the lift of valve 86, the pressure differential between exhaust crossover passage 40 and insert plate primary riser bores 44 and 46 being sufficient to maintain flow through control valve 62 at or near sonic velocity. The lift of valve 86 is determined by the vacuum signal created by slot 132 which, as shown in FIG. 4, is proportional to the rate of induction air flow. The precise value of the vacuum signal may be controlled by the contour of slot 132 and its orientation with respect to throttle 136.

As throttles 136 and 137 approach wide open position, the induction vacuum below the throttles becomes insufficient to hold diaphragm 122 against the bias of spring 124. Valve pintle 86 thereupon reengages valve seat 84 to prevent recirculation of exhaust gases.

An additional advantage in the design of valve 62 also should be noted: no elaborate seals are required to assure against leakage about valve stem 88. Because chamber 78 is connected through passage 64 directly to the induction system below throttles 136 and 137, chamber 78 is maintained at subatmospheric pressures. Thus any leakage past valve stem 88 is only atmospheric air entering from within housing member 94, and the potential for deposits around valve stem 88 is minimized.

Another embodiment of control valve 62 is shown in detail in FIG. 5. It comprises a base member 150 having an upper wall 152, a peripheral wall 154, and a lower wall 156 which define a chamber 158. Chamber 158 has an inlet 160 opening from a zone 162 separated from the first portion 60 of the exhaust gas recirculation passage by an orifice member 164. Chamber 158 also has an outlet 166 opening to the second portion 64 of the exhaust gas recirculation passage. A valve seat 168 is formed in inlet 160.

A valve pintle 170 cooperates with valve seat 168 and may be contoured to provide a variable area for flow of recirculated exhaust gases. Valve pintle 170 is adjustably threaded on a valve stem 172. Stem 172 extends upwardly through an opening 174 in the upper wall 152 of base member 150.

A housing member 176 has a central portion 178 provided with an opening 180 receiving valve stem 172.

An intermediate member 182 has an annular, downwardly concave, dished portion 184 disposed between the central portion 178 of housing member 176 and the upper wall 152 of base member 150. An asbestos insulating disc 186 is received in the dished portion 184 of intermediate member 182 and reduces conduction of exhaust heat from base member 150 to housing member 176.

Intermediate member 182 also has a central, downwardly concave, cupped portion 188 with a central opening 190 receiving valve stem 172. A plurality of graphited asbestos sealing discs 192 and a steel washer 194 are received in the cupped portion 188 of intermediate member 182 and engage valve stem 172 to guide stem 172 and to reduce air flow into chamber 158 through openings 190 and 174.

Housing member 176 has an outer rim 196 supported by three outwardly and upwardly extending spokes 198 (only two of which appear in the figure). Each spoke 198 has a slightly raised rib 199 for reinforcement. Spokes 198 provide a minimized path for heat conduction from the central portion 178 of housing member 176 to the rim 196 of housing member 176.

A cover member 200 has a rim 202 secured within rim 196 of housing member 176. A diaphragm 204 is clamped between rims 202 and 196 to define an enclosure 206 between diaphragm 204 and cover 200. Diaphragm 204 carries valve stem 172. A spring 208 exerts an upward bias on diaphragm 204, valve stem 172, and valve pintle 170 to engage valve pintle 170 with valve seat 168.

The pressure in zone 162 is applied through a passage 210 in valve stem 172, having a restricted opening 212 at the tip 214 thereof, to enclosure 206. Upon an increase in pressure in zone 162, diaphragm 204 is depressed and valve pintle 170 is displaced from valve seat 168 to permit recirculation of exhaust gases from exhaust crossover passage 40 through bore 58, passage 60, inlet 160, chamber 158, outlet 166, passage 64 and branches 66 and 68 to riser bores 44 and 46. Upon a decrease in pressure in zone 162, spring 208 raises diaphragm 204 and valve pintle 170 is displaced toward valve seat 168 to reduce recirculation.

Control valve assembly 62 thus is effective to maintain the pressure in zone 162 within a narrow range despite wide variations in exhaust back pressure in pas

3,762,384 sage 60 and induction passage vacuum in passage 64: valve pintle 170 is moved toward valve seat 168 to counteract a decrease in pressure occasioned by application of manifold vacuum through valve seat 168, and pintle 170 is moved away from valve seat 168 to coun- 5 teract an increase in pressure occasioned by application of exhaust back pressure through orifice member 164. Hence exhaust gas is metered through orifice member 164 from passage 60 at full exhaust back pressure to a substantially constant pressure zone 162.

The back pressure created in the exhaust passages such as 40 of an internal combustion engine is generally proportional to the square of the rate of combustion air flow through the engine induction passages. The rate of flow of exhaust gases from an exhaust passage such as 40 through an orifice such as 164 to a zone such as 162 at substantially constant pressure is generally proportional to the square root of the exhaust back pressure. Thus the rate at which exhaust gases are recirculated ₂o is generally proportional to the rate of combustion air flow.

In some applications, it may be desirable to employ a very weak spring 208 which will permit unseating of valve pintle 170 when the back pressure is very low — 25 10 inches of water, for example. However, such a construction would permit valve pintle 170 to prematurely engage orifice member 164 which shuts off recirculation of exhaust gases. In such an application, therefore, it may be desirable to employ a second spring 216, ³θ spaced slightly from diaphragm 204, which is engaged by diaphragm 204 after pintle 170 reaches a fully open position — at a back pressure of about 30 inches of water, for example. Spring 216 decreases the response of diaphragm 204 to increases in back pressure so that pintle 170 does not engage orifice member 164 and shut off recirculation of exhaust gases until the back pressure reaches a value in the range of 80 to 100 inches of water, for example. ₄θ

Spring 208 is seated on a plate 218 which is supported from housing 176 on a member 220. A tang 222 of member 220 extends through a slot 224 in plate 218 and is bent over and retains the lower end of spring 216. 45