Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-03-08
2001-06-26
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S698000
Reexamination Certificate
active
06250289
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for operating an internal combustion engine such as an engine for a motor vehicle wherein air is drawn into a combustion chamber by suction and regeneration gas is supplied to the air. Fuel is injected directly into the combustion chamber and the fuel and the regeneration gas are combusted in the combustion chamber. Furthermore, the invention relates to an internal combustion engine such as for a motor vehicle with a tank-venting valve with which regeneration gas is supplied to the air drawn by suction into the combustion chamber. The engine includes injection valves with which the fuel is injected directly into the combustion chamber and includes a control apparatus for controlling (open loop and or closed loop) variables which influence the combustion of the fuel and of the regeneration gas in the combustion chamber.
BACKGROUND OF THE INVENTION
Ever higher requirements are imposed on an internal combustion engine of a motor vehicle with respect to a reduced consumption of fuel, on the one hand, with a simultaneously low discharge of toxic exhaust gases, on the other hand. This has led to the situation that the air/fuel mixture (emanating from the fuel in the fuel tank), the so-called regeneration gas, is likewise supplied to the combustion process in the engine and is used in this manner. The mass flow and the hydrocarbon concentration of the regeneration gas are determined to consider the regeneration gas when injecting fuel into the combustion chamber. In this way, the fuel quantity, which is contained in the regeneration gas, is computed and thereby can be subtracted from the fuel quantity to be injected. The determination of the hydrocarbon concentration of the regeneration gas takes place for non-direct injection engines with the aid of a lambda probe which is subjected to the exhaust gas generated by the combustion. For this determination, it is necessary to integrate a variable, which is dependent upon the lambda sensor, during the regeneration operation over a longer time interval.
Internal combustion engines wherein fuel is not injected directly into the air intake pipe but is injected directly into the combustion chamber have the advantage that a further reduction of the fuel consumption is possible especially for low loads. In these load ranges, the fuel is injected directly ahead of the ignition and preferably into the region of the spark plug. A mixing with air takes place only to a slight extent and it is for this reason that this defines the so-called stratified operation of the direct-injecting engine. In this stratified operation, the ratio of the fuel and air exhibits a characterizing lambda value having a very high value because of the reduced fuel quantity referred to the inducted air. It is known that for high lambda values of the lambda sensor of this kind, only very imprecise measuring results are supplied so that faults are exhibited by an integration of the above-mentioned quantity dependent upon the lambda sensor. For this reason, a computation of the concentration of the regeneration gas with the aid of the integration method known to date serves no real purpose in stratified operation.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for operating an internal combustion engine, such as an engine for a motor vehicle, so that a consideration of the regeneration gas is possible even for a direct injection when injecting the fuel.
The method of the invention is for operating an internal combustion engine such as for a motor vehicle. The engine has a combustion chamber and the method includes the steps of: adding regeneration gas for only a short time duration (T) to air inducted into the combustion chamber; injecting fuel directly into the combustion chamber; combusting the fuel and the regeneration gas in the combustion chamber and assuming a specific behavior of the combustion of the fuel and the regeneration gas; detecting the actual combustion behavior of the fuel and the regeneration gas; determining the hydrocarbon concentration of the regeneration gas from the assumed specific behavior and the detected behavior; and, injecting fuel into the combustion chamber during the next time duration (T) for an injection time (TI) dependent upon the hydrocarbon concentration.
The mode of operation of the engine, that is the behavior thereof, is monitored during this short time duration. For example, the engine is monitored with respect to a mode of operation which remains steady state. If this actual mode of operation corresponds to a pregiven desired mode of operation, then the fuel quantity injected into the combustion chamber is correct. If, however, a deviation is determined, then the injected fuel quantity can either be correspondingly reduced or increased on the basis of this deviation during the next short-term supply of regenerated gas. In this way, it is overall possible to correctly compensate the additional fuel supplied via regeneration gas by a corresponding reduction of the injected fuel quantity. An integration (which runs over a longer time) of a quantity dependent upon the lambda sensor is not necessary. The method therefore supplies a fault free adaptation of the injected fuel quantity during the supply of the regeneration gas.
In a further step of the invention, a specific behavior of the combustion of the fuel and of the regeneration gas is assumed to achieve a desired mode of operation of the engine. The actual behavior of the combustion of the fuel and of the regeneration gas is detected and the fuel is supplied during the time duration for an injection time, which is dependent upon the assumed and the detected behavior. Accordingly, an expectation value is pregiven for which it is assumed that the engine maintains a desired mode of operation especially directly after the opening of the tank-venting valve. The expectation value relates to a specific behavior of the combustion in the combustion chamber for which the desired mode of operation of the engine is achieved. Furthermore, the actual behavior of the combustion is detected. As will be described hereinafter, this can be undertaken in various ways. This actual value together with the expectation value defines the basis for determining the quantity of fuel injected into the combustion chambers. Overall, a control (open loop and/or closed loop) is provided for which the actual behavior of the combustion is that quantity with the aid of which the engine is to be adjusted to the desired mode of operation.
In a further advantageous embodiment of the invention, the following takes place: an actual value is generated in dependence upon the detected behavior of the combustion of the fuel and of the regeneration gas; an expectation value is determined in dependence upon the assumed behavior of the combustion; the actual value is compared to the expectation value; and, the injection time is determined in dependence upon the comparison. This defines an expectation value/actual value comparison with the aid of which the compensation of the additional fuel quantity, which is added by the regeneration gas, is achieved by a corresponding reduction of the fuel quantity to be injected.
For an advantageous configuration of the invention, the regeneration gas is supplied for several sequential time durations to the inducted air. The supply of the regeneration gas is therefore clocked. During each supply, the behavior of the combustion and especially the change of this behavior is monitored. The injection time is changed in dependence thereon. In this way, an approximation method is provided with which, for each supply of regeneration gas, the injection time changes and thereby approaches the correct injection time. With the clocked supply of the regeneration gas, it is achieved that, in the case of an incorrect injected fuel quantity, the correct fuel quantity is quickly injected by the injection valves into the combustion chamber and thereby a correct compensation of the supplied regeneration gas is carried out.
Esteghlal Gholamabas
Mallebrein Georg
Kwon John
Ottesen Walter
Robert & Bosch GmbH
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