Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2002-11-20
2004-06-22
Vo, Hieu T. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C123S436000
Reexamination Certificate
active
06754577
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for operating an internal combustion engine wherein a fresh air charge of a combustion chamber is considered in the determination of a pressure in a region lying upstream from an inlet valve or, for the determination of the fresh air charge of a combustion chamber, the pressure in the region is considered lying upstream from the inlet valve. An rpm of a crankshaft of the engine is also considered in the determination.
BACKGROUND OF THE INVENTION
Such a method is known from the marketplace and is used, for example, in internal combustion engines having intake manifold injection. In internal combustion engines of this kind, either an air mass sensor is installed in the vicinity of a throttle flap or an intake pressure sensor is installed in an intake manifold. For the control of the engine, one needs as a rule, however, the intake manifold pressure as well as the fresh air charge. This means that the quantity, which in each case is not detected with a sensor, must be simulated by means of a model. The corresponding model is characterized as a “charge exchange model”.
Based on this charge exchange model, the fresh air mass, which is inducted by the engine, is computed, for example, from the input quantity “intake manifold pressure”. The computation takes place by means of a linear equation which includes a linear slope factor which is multiplied by the difference between the intake manifold pressure and a partial pressure of an internal residual gas.
By considering this internal residual gas, the fact is taken into account that the cylinder charge always contains a certain residual gas quantity from the last combustion. A certain portion of the exhaust gas from the exhaust-gas pipe again reaches the combustion chamber during an exhaust gas recirculation because of valve overlap. This can, for example, be achieved in that the outlet valve closes only after the piston of the engine passes the top dead center. In this way, a time span can result wherein the outlet valve and the inlet valve of a combustion chamber are opened simultaneously. This time span is characterized as an overlap angle referred to a camshaft revolution.
From the marketplace, functions are known for computing the internal partial pressure of the residual gas in the combustion chamber as well as for computing the linear slope factor with the aid of characteristic fields. The following are, for example, fed into the characteristic fields: the rpm of the crankshaft of the engine; the overlap angle of the camshafts and, if required, the overlap centroid of the camshafts. However, such characteristic fields require a relatively large memory space. Furthermore, there is a requirement in present day internal combustion engines that the fresh air charge and/or the intake manifold pressure be computed with still greater precision.
From the marketplace, simulation programs are known with which the thermal and dynamic conditions within the engine can be simulated in very small steps. The actual operations during charge exchange can be simulated rather well with such simulation programs. Even pulsations which occur during operation in the intake manifold and in the exhaust-gas system of the engine can be modeled. However, a computation in real time, for example, in a control apparatus of the engine is not possible with such simulation programs because of the high complexity of computation.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a method of the type mentioned initially herein so that the desired quantity can be determined with this method with less complexity as to computation and, at the same time, with high precision.
The method of the invention is for operating an internal combustion engine including a combustion chamber, a crankshaft and inlet and outlet valves opening to the combustion chamber. The method includes the steps of: detecting the rpm (nmot) of the crankshaft; considering a fresh air charge (rl) of the combustion chamber and the rpm (nmot) when computing a pressure (ps) in a region lying upstream of the inlet valve by utilizing at least one of thermodynamic equations and flow equations at at least one discrete time point during a work cycle of the engine; or, considering a pressure (ps) in the region and the rpm (nmot) when computing the fresh air charge (rl) of the combustion chamber by utilizing one of thermodynamic equations and flow equations at at least one discrete time point during a work cycle of the engine.
The actual thermal and dynamic conditions in the combustion chamber and in the regions of the engine close to the combustion chamber can be determined with a very high precision with thermodynamic equations and/or flow equations. In contrast to the use of empirical equations and/or of characteristic fields, also the complex thermal and dynamic characteristics of modern internal combustion engines can be simulated very accurately. The computation load of a control apparatus with which functions of the engine are controlled (open loop and/or closed loop) are very low.
The formula or formulas, which result from the thermodynamic equations and/or flow equations for the computation of the fresh air charge and/or of the pressure, need only be computed once during a work cycle of the engine. A continuous small-stepped computation of the instantaneous thermal and dynamic condition in the engine is not necessary in the method of the invention as it is required in conventional simulation programs utilizing mainframe equipment. Furthermore, the influence of the instantaneous temperature of the supplied fresh gas as well as the temperature of the exhaust gas can be simulated physically in a simple manner which likewise contributes to the accuracy of the computed result.
In a first embodiment of the invention, it is suggested that a remainder gas be considered in the computation which is present in the combustion chamber after the closing of the inlet valve. Such a remainder gas is almost always present to a slight extent and is especially present however when the engine has an internal or external exhaust-gas recirculation. In such an internal exhaust-gas recirculation, the opening time point of the inlet valve and/or the closing time point of an outlet valve is so placed that the combustion chamber is filled at the start of a new work cycle not only with fresh air but also with remainder exhaust gas coming from a previous combustion. The flame temperature in the combustion chamber can be reduced by the remainder gas and therefore the formation of nitrous oxide is reduced. The consideration of this remainder gas, which is present in the combustion chamber, is very well possible with the method of the invention.
In a further embodiment, it is suggested that, in the computation, at least one of the following is considered: a residual remaining gas, which is present in the combustion chamber after the closing of the inlet valve and a reaspirated remaining gas, which is present in the combustion chamber after the closing of the inlet valve. In this way, the accuracy in the computation of the fresh air charge or of the pressure in the region lying upstream from the inlet valve is improved still further. With the term “upstream”, that region is meant which is disposed between the inlet valve and the beginning of the intake manifold independently of whether the flow is actually from the intake manifold into the combustion chamber or from the combustion chamber into the intake manifold.
The residual remainder gas is understood to be that remainder gas which is trapped in the combustion chamber volume at combustion chamber temperature and under exhaust-gas counterpressure at the time point of the closing of the outlet valve of the engine. Reaspirative remainder gas is understood to be the remainder gas which flows during the valve overlap (that is, when the inlet and outlet valves are simultaneously open) from a region, which lies downstream of the outlet valve, through the combustion chamber into the region lying upstream from the
Drung Michael
Gross Jochen
Klein Eberhard
Mallebrein Georg
Martin Lionel
Ottesen Walter
Robert & Bosch GmbH
Vo Hieu T.
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