Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2002-03-25
2004-01-06
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
Reexamination Certificate
active
06672292
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fluid inlet, which can be used, in particular, as an exhaust gas recirculation inlet in the intake system of an internal combustion engine.
It is known in the art to recirculate exhaust gases into the intake system of an internal combustion engine. This measure is taken to reduce the emission of harmful substances by the internal combustion engine. The high temperature of the exhaust gas, however, is problematic. Particularly if the intake system is made of synthetic resin material (i.e., plastic), the introduction of the exhaust gas can cause the intake system to melt in the area of the exhaust gas inlet.
To prevent excessive thermal stress of the intake system, European patent no. EP 486,338 proposes an exhaust gas feed line with a double-walled construction. The exhaust gas is fed through the inner pipe into the intake system. The hollow space resulting between the two walls has an insulating effect relative to the contact point of the exhaust gas feed line and the intake pipe.
To achieve an additional cooling effect, a portion of the fresh intake air is guided through the gap. This fresh air is taken from a throttle valve and reaches the gap via a bypass line. The cooling air returns to the intake system through corresponding openings parallel to the exhaust gas stream.
In this proposed solution, however, the proportion of recirculated exhaust gas to passing combustion air cannot be increased at will. The double-walled pipe is connected directly to the intake pipe such that, with higher recirculation rates, there is nevertheless a risk that the wall of the intake system will melt. Furthermore, the hot exhaust gas stream strikes the opposite wall of the intake system unchecked and causes high thermal stress in this area, too, which can lead to component failure.
To prevent this European patent application no. EP 886,063 proposes a gas conducting element
26
(cf.
FIG. 2
) with a high thermal loading capacity, which protects the wall of the intake system against a direct impact of the hot exhaust gas stream. Within this gas conducting element, the hot exhaust gas stream has sufficient time to mix with the intake air. Furthermore, the gas conducting element is made of a heat-resistant material. This material has a high thermal stability and can therefore intermediately store or conduct heat peaks in the introduced exhaust gas and release them again during operating states that develop less heat.
This component, however, increases the weight of the unit. This is undesirable particularly in mobile applications, e.g., in motor vehicles. Furthermore, the gas conducting element increases the material and production costs for the intake system.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved fluid inlet for introducing a hot fluid into a hollow structure.
Another object of the invention is to provide a fluid inlet for introducing a hot fluid into a stream of cooler fluid flowing through a duct or pipe.
It is also an object of the invention to provide a fluid inlet for introducing a hot fluid into a hollow structure which will effectively protect the hollow structure against damage due to thermal stress resulting from introduction of the hot fluid.
A further object of the invention is to provide a fluid inlet for introducing a hot fluid into a hollow structure which is cost-effective to produce.
An additional object of the invention is to provide an inlet for introducing a hot fluid into a hollow structure which has a low overall weight.
These and other objects are achieved in accordance with the present invention by providing a fluid inlet for introducing a hot fluid into a hollow structure, comprising a hollow structure for conducting a stream of a fluid; an inlet feed connection to introduce a hot fluid into the hollow structure; and an insert mounted inside the hollow structure having a wall surrounding the inlet feed connection to shield the hollow structure from hot fluid introduced through the inlet connection; in which the inlet connection has a higher thermal stability than the hollow structure and is heat-resistant relative to said hot fluid, and in which the insert shields interior walls of the hollow structure against the introduced hot fluid, and the walls of the insert are at least substantially aligned in the flow direction of the introduced fluid.
The fluid inlet according to the invention comprises three structural functional areas: the hollow structure, the inlet connection, and an insert. The hollow structure is suitable for conducting a fluid and may, for instance, comprise an intake pipe for an internal combustion engine. The inlet connection is suitable to be connected to a supply line or duct through which the hot fluid to be introduced is supplied. These components are interconnected.
The described fluid inlet must be designed for the thermal stresses caused by the introduction of the hot fluid. This means that the inlet connection must be heat-resistant to the fluid being introduced. For the hollow structure, however, materials with a lower melting point, such as thermoplastic synthetic resin materials, are frequently used. These materials would melt if the fluid being introduced impinged directly against them, which would lead to component failure. To prevent this, an insert is provided in the hollow structure according to the invention in the area where the introduced fluid would strike the walls of the hollow structure. This insert is characterized in that it has walls with inner surfaces that are at least substantially aligned with the direction of flow of the introduced fluid. This prevents the introduced fluid from striking the insert directly. The flow of the introduced fluid will therefore gradually conform to the insert, so that significantly less heat is transferred to the insert than would be the case if the flow impacted it directly. This effect is further enhanced in that the introduced fluid is mixed with the passing fluid before it strikes the insert, so that the fluid mixture is cooled. This, too, reduces the thermal stress on the insert.
The advantage achieved by the invention can be used in different ways. Compared to insert elements used in the prior art, the insert can be provided with thinner walls to save weight. The low thermal capacity of the insert is compensated by the lower thermal stress. Another possibility is to select a material with a lower melting point for the insert. Even plastics with a high melting point can be considered here. This will reduce the component weight and permit cost-effective production of the insert. A plastic component can furthermore be more easily disposed of, e.g., by incineration.
A third possibility of using the described advantage is an increase in the temperature of the fluid being introduced. A particularly suitable application is found in the automotive area if the fluid supply line is used to recirculate exhaust gas into the intake system of an internal combustion engine. Especially in modern diesel engines, a high exhaust gas recirculation rate is required in certain operating states to meet the required exhaust gas emission values. These high exhaust gas recirculation rates can be realized with economically produced parts if the described design principle is followed.
In accordance with a further embodiment of the inventive concept, a space or gap is provided between the insert and the walls of the hollow structure. This gap insulates the hollow structure relative to the insert if the fluid passing through the hollow structure has a lower heat conduction coefficient than the insert. The hollow structure can be designed as a bypass line segment for the fluid passing through. In this case, the flow passing through does not mix with the fluid being introduced, so that it has additional cooling properties relative to the insert, which is being heated. In this way the thermal stress of the insert can be reduced even further.
A further variant of the invention is created by providing t
Filterwerk Mann & Hummel GmbH
Kwon John
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