Internal Combustion Engine Intake Manifold With Integral EGR Cooler and Ported EGR Flow Passages

The present invention relates to an intake manifold for a multicylinder internal combustion engine in which exhaust gas recirculation (EGR) is introduced by means of a central distribution system into runners of the intake manifold in close proximity to the intake valves.

EGR is essential to the control of emissions of oxides of nitrogen (NO.sub.x) by modern automotive internal combustion engines. EGR systems have been used in automotive engines for more than 25 years. During this time, most EGR systems have utilized a central EGR valve which admits exhaust gas into the incoming air or air/fuel mixture at a point in the intake manifold plenum which is well upstream of the intake ports located in the cylinder heads. As a result, it is not possible to finely or precisely control EGR flow because of the inherent time lags involved in stopping and starting the flow. This may cause control problems. For example, it is desirable to avoid misfire during closed throttle deceleration, inasmuch as misfire produces high levels of unburned hydrocarbon in the exhaust. Because combustion instability and misfire is promoted if the level of EGR in the cylinder is too great during deceleration, it is often not possible to operate an engine with a level of EGR which would otherwise be desirable for NO.sub.x control because it is not possible to shut off the EGR and purge the intake manifold of EGR gases before the throttle is closed. As a result, NO.sub.x control suffers because the engine must be operated with a lower overall level of EGR. Although various schemes have been tried to introduce EGR at points other than at a spacer mounted under a throttle body or at a central point in the engine's induction system, other problems have arisen. For example, EGR gases have been introduced in a spacer located between an intake manifold and a cylinder head, at the mounting surface between the cylinder head and manifold. This has resulted in sludging in some engines and has generally been unsatisfactory. In contrast, the present system uses an axially extending, cooled, central EGR distribution system having special anti-sludging features which promote the rapid control of EGR flow without the plugging associated with other systems. It is thus an advantage of the present system that higher levels of EGR may be used in an engine without concomitant problems such as misfire and sludging of the EGR passages and discharge nozzles. And, sludging of secondary throttles is avoided because EGR is routed exclusively through the manifold's primary runners.

An intake manifold for a multicylinder reciprocating internal combustion engine with a cylinder block having at least one cylinder head mounted thereto and a crankshaft mounted therein, has a plurality of intake runners conducting air and sometimes air and fuel to a plurality of intake ports formed in the cylinder head, and an EGR supply passage formed in the manifold and extending generally parallel to the crankshaft of the engine. A plurality of secondary EGR passages is contained in the intake manifold, with the secondary EGR passages extending from the EGR supply passage to the intake runners. A coolant passage formed in the manifold extends generally parallel to the EGR supply passage and has a common wall with the EGR supply passage. Each of the secondary EGR passages comprises a cylindrical aperture having an orifice cartridge inserted therein, with each cartridge comprising a generally cylindrical hollow body having a sharp edged orifice contained in one end thereof. The end of each orifice cartridge having the sharp edged orifice protrudes into one of the intake runners for a length which exceeds one fourth of the diameter of the cylindrical hollow body of the cartridge.

In one embodiment of the present invention, the cylinder head has a separate exhaust port associated with each of the cylinders, with the EGR supply passage being furnished with exhaust gas from at least two of the exhaust ports, and with a separate exhaust feeder passage extending from each of the exhaust ports to the EGR supply passage. In a preferred embodiment, a manifold according to the present invention is mounted between the cylinder banks of a V-type engine with the EGR supply passage and coolant passage being situated approximately an equal distance from each of the cylinder banks. The coolant passage has an engine coolant path flowing through it such that the engine coolant will remove heat from exhaust gas flowing through the EGR supply passage.

In a preferred embodiment, each of the secondary EGR discharge passages comprises a cylindrical aperture having an orifice cartridge inserted therein, with said cartridges each comprising a generally cylindrical body having a sharp edged orifice contained in one end thereof and being retained in an intake manifold by means of a plurality of extension tabs extending axially and radially from the end of the cylindrical body which opposes the end having the sharp edged orifice.

According to yet another aspect of the present invention, the subject intake manifold is ideally applied to an engine having primary and secondary intake runners for conducting air and fuel (or only air, in the case of diesel, or direct-injection or port injected gasoline engines) to the intake ports of the engine, with flow through the ports being controlled by either a single intake valve for each of the engine's cylinders or a plurality of intake valves for each of the cylinders.

EGR flow according to the present invention is considered to be ported because EGR gases flow through secondary EGR passages extending from an EGR supply passage to the individual runners of the intake manifold. Moreover, those skilled in the art will appreciate in view of this disclosure that a system according to the present invention could be employed so as to conduct EGR into the intake ports within the cylinder heads, as opposed to EGR entry into the intake manifold runners. In such case, the secondary EGR passages could extend from the intake manifold into the cylinder head's intake ports without passing through the runners upstream of the intake ports.

FIG. 1 is a perspective view of a V-type engine having an intake manifold according to the present invention. Those skilled in the art will appreciate in view of this disclosure that only the lower part of the intake manifold is shown, it being understood that an upper part having at least a throttle body, if not fuel injectors associated therewith would be applied to the engine in a fashion known to those skilled in the art and suggested by this disclosure.

FIG. 2 is a plan view of an intake manifold according to the present invention.

FIG. 3 is a longitudinal cross-section of a manifold according to the present invention, taken along the line 3--3 of FIG. 2, which is also the centerline of the engine's crankshaft, which is marked C/L.

FIG. 4 is a transverse cross-section of a manifold of FIG. 2 taken along the line 4--4 of FIG. 2.

FIG. 5 is a sectional view of a manifold of the present invention taken along the line of 5--5 of FIG. 2, showing an orifice cartridge with particularity.

FIGS. 6 and 7 are perspective views of an orifice cartridge according to one aspect of the present invention.

FIG. 8 shows an alternative embodiment according to the present invention.

FIG. 9 is a schematic representation of an alternative embodiment of the present invention.

As shown in FIG. 1, engine 10 has lower intake manifold 12 and cylinder heads 14. Although engine 10 is shown as being of the V-type, those skilled in the art will appreciate in view of this disclosure that an intake manifold according to the present invention could be applied to an engine having an inline, or horizontally opposed, or other type of configuration. Moreover, the present invention could be applied to an engine having a single or divided intake ports controlled by one valve or divided intake ports controlled by more than one intake valve.

As shown in FIG. 2, intake manifold 12 according to the present invention has a series of primary intake runners 18A which are open at all times, and a plurality of secondary intake runners 18B, the flow through which is controlled by a series of secondary port throttles 2, which are mounted on common shafts 34. EGR is introduced only through primary intake runners 18A because in this manner the flow through primary runners 18A will generate high swirl and fast burn combustion characteristics. This will allow an engine equipped with a system according to the present invention to maintain acceptable combustion characteristics with high quantities of EGR gas, allowing improvements in fuel economy and reduced NO.sub.x emissions, and, because EGR is introduced close to the intake ports (22, FIG. 9) within the cylinder heads, the engine will tolerate increased quantities of EGR as a result of the quick response of the system. Introduction of EGR through primary runners 18A also allows the use of EGR when secondary port throttles 32 are closed.

FIG. 2 illustrates that a system according to the present invention may be applied to an engine having a single intake valve 20 serving two intake ports, 22A and 22B controlled by single valve 20A in one case, or by two intake ports 22A and 22B controlled by two valves 20B. In either case, EGR is introduced into the engine via primary intake runners 18A, so as to achieve high velocity flow and resulting high swirl and fast burn characteristics. Those skilled in the art will appreciate in view of this disclosure that more than two intake valves could be employed according to the present invention.

FIGS. 3 and 4 illustrate the construction of the EGR supply passage and coolant passages in a manifold according to the present invention. As best seen in FIG. 4, EGR supply passage 24 is formed in and integral with manifold 12. As suggested in FIG. 3, supply passage 24 extends generally parallel to the crankshaft of the engine. The centerline of the crankshaft is shown in FIG. 2 as C/L; the outline of EGR supply passage 24 is shown in ghost in FIG. 2, which of course is a plan view of manifold 12. As shown in FIGS. 3 and 4, engine coolant passage 28 shares a common wall, 28A, with EGR supply passage 24. As with EGR supply passage 24, coolant passage 28 is cored into manifold 12, which may be formed from aluminum or other metallic or non-metallic, heat-resistant and low heat transmitting materials known to those skilled in the art and suggested by this disclosure. Because coolant passage 8 has a common wall with EGR supply passage 24, this shared common wall allows heat transfer between EGR gases and engine coolant. As a result, during cold operation, hot coolant warms EGR supply passage 24, so as to reduce the risk of condensation and sludging or deposit obstruction of sharp edged orifices 44 (FIG. 6). During warmed-up or hot engine operation, the relatively cold coolant extracts heat from the EGR gases, reducing the risk of detonation and also reducing the risk of deposit formation within the various EGR passages. An additional advantage of the present system is that because the hot exhaust gas is confined solely to the lower manifold, manifold 12 in this case, the upper manifold (not shown) may be constructed of lighter and less costly thermoplastic because the upper manifold need not come in contact with the hot, corrosive EGR gases.

FIG. 3 illustrates water passage 25 allowing engine coolant to pass into coolant passage 28. After flowing the length of passage 28, coolant exits through outlet 28B.

Details of construction of the secondary EGR passages and orifice cartridges are shown in FIGS. 5, 6, and 7. Starting with cylindrical aperture 26, which extends from EGR supply passage 24 to primary intake runner 18A, the secondary EGR passages each further include orifice cartridge 40 having a generally cylindrical hollow body 42, with a first end having sharp edged orifice 44 therein, and a second end having a plurality of retention tabs 46 extending axially and radially from the end of generally cylindrical body 42. It has been determined that stainless steel comprises an appropriate material for construction of orifice cartridges 40. It has further been determined that it is beneficial for cartridges 40 to extend, as shown in FIG. 5, a distance from the wall of runner 18A through which the cartridge extends. In other words, the sharp edged orifice 44 should be carried at some distance from wall 18C through which the orifice cartridge extends. Extension of sharp edged orifice 44 into runner 18A by a distance exceeding one fourth of the diameter of cylindrical hollow body 42 will assure that flow through orifice 44 is not occluded due to a build-up of sludge in and around orifice 44. Although not wishing to be bound by the theory, it is believed that protrusion of sharp edged orifice 44 into runner 18A causes a reduction in the risk of plugging because of convective cooling from the passing air stream. FIGS. 6 and 7 show collar 48 comprising an annular radial extension of the outer cylindrical surface of generally hollow body 42. Collar 48 allows orifice cartridge 40 to be inserted either manually or by automated machinery to a preset protrusion level, so as to maintain the beneficial protrusion of orifice 44 into runner 18A. Those skilled in the art will appreciate in view of this disclosure that orifice cartridges 40 could be retained within their parent bores by alternate means such as staking, pressing, welding, bonding, or other means.

FIG. 9 illustrates yet another aspect of the present invention, which schematically indicates that EGR supply passage 24 is furnished with exhaust gas taken directly from exhaust ports 30 of the engine, with a separate exhaust feeder passage 38 extending from each of exhaust ports 30 at a location which is adjacent exhaust valve 31 and its seat, to EGR supply passage 24. Each exhaust feeder passage 38 has one end which is located adjacent the exhaust valve and seat. It has been determined that drawing exhaust gases from the individual exhaust ports close to the exhaust valve and seat will allow the recirculation of exhaust gases containing high levels of unburned hydrocarbons and, as a result, the unburned hydrocarbon emissions of the engine will be correspondingly reduced. This effect is even more pronounced during cold engine warmup, given the fact that most catalysts are not operational during cold starting and warmup, and any reduction of unburned hydrocarbons is particularly needed.

FIG. 8 illustrates an alternate embodiment of the present invention in which the secondary EGR passages comprise bare cylindrical borings 26A. In certain applications an ordinary drilling as shown in FIG. 8 may produce satisfactory results in terms of resisting plugging, and if this is the case, the cost of a system according to the present invention may be correspondingly reduced by eliminating the need for a plurality of orifice cartridges 40.

While the invention has been shown and described 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, although the intake runners are generally described herein as conveying air and fuel to the intake ports of the cylinder heads, the present invention is equally applicable to fuel injection arrangements in which only air is carried through the intake runners, with the fuel being supplied either through direct cylinder fuel injection as with diesel or direct-injected gasoline engines, or by means of port injection of gasoline. Also, the present invention could be applied to natural gas fueled engines, or other types of internal combustion engines.