Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-11-22
2001-10-02
Wolfe, Willis R. (Department: 3747)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C123S568120, C123S568110, C123S568200
Reexamination Certificate
active
06295815
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an internal combustion engine, particularly an internal combustion engine with an exhaust gas re-circulation system including an exhaust gas re-circulation line, which branches off an exhaust gas pipe and returns exhaust gas to an engine intake duct and which includes a valve for controlling the re-circulation flow of the exhaust gas.
Such an internal combustion engine is described for example in DE 195 24 603 C1. The known internal combustion engine includes an exhaust gas re-circulation system by way of an exhaust gas re-circulation line, which branches off an exhaust pipe and re-circulates exhaust gases to a charge air intake duct. The exhaust gas re-circulation line includes a shutoff valve which, depending on its position, permits, or blocks, passage of exhaust gases through the re-circulation line. During normal operation with exhaust gas re-circulation, the shut-off valve is closed when the engine power output is above a certain value since otherwise the charge air pressure in the intake duct would be higher than the exhaust gas pressure in the exhaust gas line so that no exhaust gas could flow through the exhaust gas re-circulation line.
The shutoff valve is a plate valve whose valve plate is biased by a valve spring onto an annular valve seat disposed in the exhaust gas re-circulation line. In an embodiment provided for commercial vehicles the shutoff valve opens against the flow direction of the exhaust gas to be re-circulated in order to prevent opening of the valve by the high exhaust gas pressure forces occurring in the exhaust gas duct during engine braking operation. These forces might otherwise exceed the closing forces of the valve spring whereby the valve would be pushed open resulting in a loss of engine braking power.
The shutoff valve is arranged at the point where the exhaust gas re-circulation line branches off the exhaust gas line and includes a tubular valve housing which forms a beginning section of the exhaust gas re-circulation line. The exhaust gas re-circulation line extends then from the valve housing at a right angle so that a valve spring and a valve operating membrane can be arranged in alignment with the tubular housing.
The shutoff valve opens into the exhaust gas line in such a way that the exhaust gas flow can pass the valve plate extending normal to the exhaust gas flow.
The known internal combustion engine has the disadvantage that, when the shutoff valve is open, the valve plate acts as a baffle plate generating a high flow resistance. The deflection of the exhaust gases necessitated by the design of the shutoff valve also results in an increased flow resistance. In order to provide for a flow of exhaust gas from the exhaust pipe to the intake duct, the exhaust gas pressure in the exhaust pipe must be higher than the intake air pressure in the intake duct. The pressure level required to be present in the exhaust pipe for the re-circulation of the exhaust gas depends among others on the flow resistance in the exhaust gas re-circulation line. In order to overcome the relatively high flow resistance caused by the shutoff valve, the pressure in the exhaust pipe must be relatively high to overcome the gas flow resistance which detrimentally affects fuel consumption of the engine.
Furthermore, the shutoff valve of the prior art arrangement is not provided with a firm stop at its open end position and can therefore be subject to oscillations because of pressure pulsations in the exhaust gas flow. As a result the free flow cross-section is reduced and the re-circulated exhaust gas volume becomes too small that is it deviates from the desired value.
In order to facilitate the flow of exhaust gases around the valve plate when the shutoff valve is open, in the arrangement shown in the patent publication the shutoff valve must be arranged exactly at the branch-off location of the exhaust gas re-circulation line and must open into this line. Otherwise, the exhaust gas re-circulation line needs to include a section of increased diameter in which the valve plate is accommodated in the open position of the shutoff valve. However, it is a disadvantage that, in the first case, the position of the exhaust valve is predetermined and cannot be changed, and, in the second case, the manufacturing costs are higher and the arrangement is larger and requires an increased amount of space.
It is the object of the present invention to provide an internal combustion engine with an exhaust gas re-circulation system of the type referred to above which, however, has low flow losses in the exhaust gas re-circulation pipe and wherein the position of the valve in the exhaust gas re-circulation line can be selected freely and in a space-saving manner.
SUMMARY OF THE INVENTION
In an internal combustion engine with exhaust gas re-circulation including a fresh air supply duct extending from the charger of a turbocharger to the engine, an exhaust pipe extending from the engine to the turbine of the turbocharger for driving the turbocharger, and an exhaust gas re-circulation pipe extending from the exhaust pipe to the intake duct, the exhaust gas re-circulation pipe includes a flap valve having a pivotally supported valve flap which, in an open position of the flap valve, is disposed in a plane parallel to the direction of the exhaust gas flow through the flap valve for minimizing the flow resistance in the exhaust gas re-circulation pipe.
The internal combustion engine according to the invention has the advantage that the valve plate extends parallel to the flow in the exhaust gas re-circulation line when the valve is open whereby the cross-section of the valve body in the exhaust gas flow is quite small. As a result, the flow resistance is substantially smaller than that of the valves used in the state of the art arrangements. As a result, the fuel consumption of the engine is reduced.
Since the cross-section of the exhaust gas re-circulation line does not need to be increased to accommodate the valve flap, the valve may be arranged at any place within the exhaust gas re-circulation line. Furthermore, the form and contour of the flap may be easily adapted to the particular conditions in the exhaust gas re-circulation line. The pivot structure of the flap can be realized in a simple arrangement by a shaft on which the flap is mounted and whose ends are rotatably supported in the walls of the exhaust gas re-circulation pipe.
It is particularly advantageous if stops are arranged at the inside of the re-circulation pipe, which are sealingly engaged by the valve flap when the valve is closed. A tight closing of the flap valve prevents a pressure equalization between the intake charge air side and the exhaust side of the internal combustion engine which is advantageous for the dynamic operation of the engine.
In a preferred embodiment of the invention, the flap of the valve has a cross-section, which is streamlined; preferably, it has a symmetrical drop-like shape. With this measure, the flow resistance of the flap can be substantially reduced.
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Bechle Sven
Gartner Uwe
Bach Klaus J.
Daimler-Chrysler AG
Wolfe Willis R.
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