Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-09-17
2001-05-15
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C123S568200, C060S605200
Reexamination Certificate
active
06230696
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an internal combustion engine, especially a diesel engine, with at least one combustion chamber, and with an intake system having at least one intake manifold, and an exhaust system and an exhaust gas recirculation system for reintroducing exhaust gas into the intake system, the exhaust gas recirculation system having at least one exhaust gas recirculation line with an exhaust gas recirculation valve.
DESCRIPTION OF THE PRIOR ART
In order to meet ever stricter exhaust emission standards whilst further improving fuel economy in internal combustion engines, especially diesel engines, it has become established practice to add a certain amount of cooled exhaust gas to the fresh air drawn in by the engine. In this way the Nox emissions of an engine are reduced to the levels required by law and good fuel economy is ensured.
In charged diesel engines of commercial vehicles the mean pressure in the exhaust manifold—depending on engine size and speed—is smaller over a wide rpm and load range than on the intake side. With the use of only a connecting line between exhaust manifold and intake side no exhaust gas would reach the intake area of the cylinders.
SUMMARY OF THE INVENTION
It is an object of this invention to reduce the Nox emissions of an engine whilst ensuring good fuel economy in a simple manner.
This is achieved according to the invention by providing that the exhaust gas recirculation line branch off directly from the combustion chamber, the exhaust gas recirculation valve being positioned preferably at the branch-off. Via the EGR valve, which is small compared to the intake and exhaust valves and may be positioned in the combustion chamber top preferably constituted by the cylinder head, high-pressure exhaust gases may be withdrawn directly from the combustion chamber at the end of the high-pressure process. Preferably, the EGR valve is actuated electrically. Actuation may be effected by means of a solenoidal or piezoelectric actuating element. The EGR valve is operated via an electronic control independently of intake and exhaust valve timing.
It is further provided that the exhaust gas recirculation system have an exhaust gas collecting line, and that at least two exhaust gas recirculation lines departing from each combustion chamber open into the exhaust gas collecting line, which latter is connected to the intake system preferably via an exhaust gas recirculation cooler. If the EGR valve opens during the exhaust phase at 180° crank angle, for instance, the positive pressure difference prevailing at that moment between the combustion chamber and the intake system will cause exhaust gas to escape through the exhaust gas recirculation line into the exhaust gas collecting line, which may be placed outside the cylinder head, for example. This line collects the exhaust gas coming from each cylinder and opens into an exhaust gas recirculation cooler. Downstream of the exhaust gas recirculation cooler the exhaust gas is reintroduced into the intake system from where it will enter the cylinders once more. Depending on actual requirements, exhaust gas may be withdrawn from one cylinder, or some of the cylinders, or all cylinders.
In a preferred variant, actuation of the EGR valve is controlled in dependence of the engine characteristics. Both the number of withdrawals and the control times of the EGR valve are optimization criteria depending on the engine design. The free choice of the EGR valve opening times permits the system to be optimally controlled and matched to all operating modes in dependence of the characteristic map. In this manner optimum exhaust gas recirculation rates will be obtained yielding optimum mileage at road load and complying with even the strictest exhaust emission standards.
Special preference is given to a variant in which the exhaust gas recirculation system can be connected to the exhaust system by at least one connecting line, which latter branches off from the exhaust gas recirculation system preferably upstream of the exhaust gas recirculation cooler, and opens into the common exhaust line of the exhaust system preferably upstream of an exhaust gas turbine. Due to this connection between exhaust gas recirculation system and exhaust system the EGR valve can also act as an exhaust brake. It will be a special advantage in this context if a control element is included, preferably downstream of the exhaust gas collecting line, via which the exhaust gas collecting line can be flow connected with the exhaust gas recirculation system or the exhaust system. Via the control element, which may be configured as a flap, the exhaust gas may be introduced either into the exhaust gas recirculation cooler or, as an alternative, into the common exhaust line upstream of an exhaust gas turbine, in dependence of the operating mode (road load or deceleration).
Compared to known types of exhaust gas recirculation systems and separate exhaust brake systems the system of the invention uses up very little space.
REFERENCES:
patent: 3702111 (1972-11-01), Weaving et al.
patent: 4156414 (1979-05-01), Kawamura et al.
patent: 4192265 (1980-03-01), Amano et al.
patent: 4328781 (1982-05-01), Morita
patent: 5115790 (1992-05-01), Kawamura
patent: 5746189 (1998-05-01), Kuzuya et al.
Graf Gernot
Hrauda Gabor
Veit Ulrich
AVL List GmbH
Dykema Gossett PLLC
Wolfe Willis R.
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