Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2002-01-15
2003-02-04
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
Reexamination Certificate
active
06513508
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a fluid feed duct, which is suitable particularly for recirculating exhaust gas into the intake system of an internal combustion engine.
The recirculation of exhaust gases into the intake tract of an internal combustion engine is known in the art. This measure is taken to reduce the emission of harmful pollutants from the internal combustion engine. A problem, however, is the high temperature of the exhaust gas. Particularly if the intake tract is made of thermoplastic synthetic resin material, the introduced exhaust gas can cause the intake tract to melt in the area of the exhaust gas feed.
To prevent thermal overstressing of the intake tract, EP 486,338 proposes a double wall design for the exhaust gas feed duct. The exhaust gas is fed through the inside pipe into the intake tract. The hollow space resulting between the double wall has an insulating effect with respect to the junction between the exhaust gas feed duct and the intake pipe.
To achieve an additional cooling effect, a portion of the fresh intake air is guided through this gap. The fresh intake air is removed from a point in front of a throttle valve and reaches the gap via a bypass line. The cooling air returns to the intake tract through corresponding openings parallel to the exhaust gas stream.
This proposed solution, however, does not allow the proportion of recirculated exhaust gas to transmitted combustion air to be increased at any desired ratio. The double-walled pipe is connected directly with the intake pipe, so that at higher recirculation rates, there is nevertheless a risk that the wall of the intake tract may melt. Also, the hot exhaust gas stream directly strikes the opposite wall of the intake tract, which creates another area of high thermal stressing and may cause the component to fail.
To prevent this, the design proposed in EP 886 063 A2 provides a gas conduction element
26
(cf. FIG.
2
), which can withstand the thermal stress and protects the wall of the intake tract against direct impingement of the hot exhaust gas stream. Within this gas conduction element the hot exhaust gas stream has sufficient time to mix with the intake air. However, such an additional component increases the design complexity as well as the weight of the intake tract. Both are undesirable in view of the greatest possible economic efficiency, which is the aim in the production and the use of the intake tract.
To obviate these drawbacks, the Automobiltechnische Zeitschrift, Volume 1992, p. 530 proposes to fasten hot pipes to plastic components. This hot pipe is again a double-walled pipe, but the inner pipe ends earlier than the outer pipe. This achieves an ejector effect, so that cooling air from the intake tract can be sucked through the gap of the double-walled pipe. Thus, the intake point is cooled and the cooling air simultaneously mixes with the exhaust gas stream and thereby cools the exhaust gas.
Even in this exhaust gas recirculation design, however, the realizable exhaust gas recirculation rates have an upper limit. To make the cooling gas stream possible, it is necessary to mount the exhaust gas recirculation pipe on a collar that merges directly into the locating flange for the exhaust gas feed duct on the intake manifold. At high exhaust gas recirculation rates, this heat bridge causes excessive thermal stressing of the intake tract in the area of the exhaust gas recirculation. Moreover, although the exhaust gas stream is being cooled, a gas guidance element in accordance with EP 886 063 must be provided in the intake tract if a certain exhaust gas recirculation rate is exceeded.
SUMMARY OF THE INVENTION
Thus, the object of the invention is to provide a fluid feed duct for conducting hot fluids into a hollow structure for transmitting a cooler fluid.
Another object of the invention is to provide a fluid feed duct arrangement which is cost effective to produce.
A further object of the invention is to provide a fluid feed duct which permits a high rate of introduced hot fluid in proportion to the transmitted fluid, while maintaining the thermal stressing of the hollow structure within the required limits.
These and other object of the invention are achieved by providing a fluid feed duct for recirculating engine exhaust gas into an intake tract of an internal combustion engine comprising a hollow structure for transmitting a fluid from an inlet to an outlet; a feed connection projecting interiorly into the hollow structure for introducing into the hollow structure a fluid that is hotter than the transmitted fluid, and a joint structure for sealingly mounting the feed connection inside the hollow structure, in which the feed connection and the joint structure have greater heat resistance than the hollow structure; the feed connection is heat-resistant to the introduced fluid; an end area of the feed connection points in the flow direction of the transmitted fluid, and sides of the end area around which the transmitted fluid flows are provided with outlets opening into the interior of the hollow structure.
In accordance with a further aspect of the invention, the objects are also achieved by providing a fluid feed duct for recirculating engine exhaust gas into an intake tract of an internal combustion engine comprising a hollow structure for transmitting a fluid from an inlet to an outlet; a feed connection for introducing into the hollow structure a fluid that is hotter than the transmitted fluid, and a joint structure for sealingly mounting the feed connection inside the hollow structure; wherein the feed connection and the joint structure have greater heat resistance than the hollow structure; the feed connection is heat-resistant to the introduced fluid, and means are provided to reduce the heat transfer from the feed connection to the joint structure.
According to the invention, the feed connection of the feed duct in the end area extending into the interior of the hollow structure is provided with outlet openings pointing in the flow direction of the transmitted fluid. This design measure causes the flow of the introduced fluid to be diverted in flow direction inside the hollow structure, which prevents the introduced fluid stream from striking a wall of the hollow structure. Using the ejector effect, the introduced fluid is caught and entrained by the flow of the transmitted fluid, so that rapid mixing occurs. This mixing simultaneously cools the introduced fluid and heats the transmitted fluid. The resultant temperature, however, falls within the range of the permissible thermal stressing of the hollow structure wall.
The outlet openings are arranged along the sides in the end area of the feed connection. The fact that there is a plurality of these openings enhances the mixing effect since the stream of the introduced fluid is broken up into many small partial streams.
In accordance with a further embodiment of the invention, the outlet openings are provided with baffles. Particularly if the feed connection is made of sheet metal, these baffles can be simply produced by stamping. The baffles are preferably bent into the interior of the feed connection and thereby cause optimal mixing of the introduced fluid with the transmitted fluid. In addition, the baffles cause the introduced fluid to be injected as it exits along the end area of the feed connection, so that direct contact of the introduced fluid with the walls of the hollow structure is avoided. This contact occurs only after a sufficient mixing path in the continued course of the transmitted flow inside the hollow structure.
To further promote the mixing of the two fluids, it is advantageous to provide the feed connection with a flow-optimized outer contour relative to the transmitted flow inside the hollow structure. As the fluid flows around the feed connection, a laminar flow is then created along the outer contour of the feed connection, particularly its end area. This improves the mixing result with the introduced fluid.
A particularly advantageous embodiment of the fluid feed duct is o
Fischer Jochem
Neuschwander Helmut
Crowell & Moring LLP
Filterwerk Mann & Hummel GmbH
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