Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-03-01
2001-03-20
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S568210
Reexamination Certificate
active
06202624
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for operating an internal combustion engine of a motor vehicle wherein the fuel is injected directly into the combustion chamber of the engine either in a first operating mode during a compression phase or in a second operating mode during an intake phase and the fuel is combusted in the combustion chamber. In the method, at least a portion of the exhaust gas, which is generated in the combustion, is fed back into the combustion chamber. Furthermore, the invention relates to an internal combustion engine especially for a motor vehicle. The engine has an injection valve with which fuel can be injected directly into a combustion chamber either in a first mode of operation during a combustion phase or in a second mode of operation during an intake phase. The engine also includes means for feeding back the exhaust gas into the combustion chamber and has a control apparatus for controlling (open loop/closed loop) the quantity of exhaust gas fed back.
BACKGROUND OF THE INVENTION
A system of this kind for operating an internal combustion engine having direct injection especially for a motor vehicle is generally known and is continuously further developed with respect to a further reduction of fuel and a reduction of exhaust gas.
In this connection, a so-called stratified charge operation as a first operating mode and a so-called homogeneous operation as a second operating mode are distinguished. The stratified charge operation is especially used for small loads; whereas, the homogeneous operation is applied for larger loads applied to the engine. In the stratified charge operation, the fuel is injected into the combustion chamber during the combustion phase and is there injected in the immediate vicinity of a spark plug. The fuel can however also be injected further distant from the spark plug and can be conducted to the spark plug via a movement of air. This has the consequence that no uniform distribution of the fuel can take place in the combustion chamber. The advantage of the stratified operation is that the applied smaller loads can be handled by the engine with a very small quantity of fuel. Larger loads, however, cannot be satisfied in the stratified charge operation. In the homogeneous operation, which is provided for such larger loads, the fuel is injected during the intake phase of the engine so that a swirling and therefore a distribution of the fuel in the combustion chamber can still easily take place. To this extent, the homogeneous operation corresponds approximately to the operation of internal combustion engines wherein fuel is injected into the intake manifold in the conventional manner.
In both modes of operation, that is, in the stratified load operation and in the homogeneous operation, the fuel quantity to be injected is controlled (open loop and/or closed loop) to an optimal value in dependence upon a plurality of input quantities with respect to a reduction of fuel, a reduction of exhaust gas and the like.
Here it is advantageous for the reduction of the generated exhaust gas when the exhaust, which arises in the combustion in the combustion chambers, is not immediately discharged into the ambient and is instead fed back into the combustion chambers in order to again be conducted for combustion.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an internal combustion engine having direct injection wherein further fuel reductions and exhaust gas reductions are possible with the aid of the exhaust-gas feedback.
This task is solved in a method of the above-mentioned type or for an internal combustion engine of the above-mentioned type in that the quantity of exhaust gas, which is fed back into the combustion chamber, is differently controlled in both modes of operation with the control being open loop and/or closed loop.
Accordingly, both modes of operation of the internal combustion engine having direct injection are considered in the control (open loop/closed loop) of the exhaust gas which is fed back. This means that especially in stratified charge operation, the exhaust-gas feedback is controlled (open loop and/or closed loop) differently than in homogeneous operation and the greatest reduction in fuel is achievable in stratified charge operation. Thus, in stratified charge operation, it is necessary to reduce the nitrogen oxide emissions which occur in this mode of operation via a corresponding exhaust-gas feedback as far as possible. Furthermore, and according to the invention, the transitions which are present between the two modes of operation, are controlled differently (open loop and/or closed loop). In total, a system for operating an internal combustion engine having direct injection is thereby achieved with which an optimal fuel reduction with simultaneous exhaust gas reduction is obtained based on the particular adapted control (open loop and/or closed loop) in each mode of operation.
In an advantageous configuration of the invention, the quantity of feedback exhaust gas in the first mode of operation is controlled (open loop and/or closed loop) in dependence upon the rpm of the engine and/or upon the torque, which is to be outputted by the engine, and/or the fuel mass which is to be injected into the combustion chamber. Accordingly, in the stratified charge operation, a complex and complete control (open loop and/or closed loop) of the exhaust-gas feedback is carried out. In this way, it is achieved that nitrogen oxide emissions, which arise in the stratified charge operation, are reduced to a minimum with the aid of the exhaust-gas feedback. According to the invention, the reductions in fuel, which are possible in stratified charge operation, are achievable with a simultaneous reduction in exhaust gas.
It is especially purposeful when the following are considered: the intake air temperature and/or the engine temperature and/or the ambient pressure and/or the degree of tank venting and/or the like. In the control (open loop and/or closed loop) according to the invention of the exhaust-gas feedback in layered charge operation, not only are the dynamic operating conditions considered such as the rpm of the engine but also the statistical operating conditions such as the engine temperature. In this way, the control (open loop and/or closed loop) is optimally adapted to the conditions of the internal combustion engine and an optimal reduction of the generated exhaust gas is thereby achieved.
In an advantageous further improvement of the invention, the quantity of the exhaust gas, which is fed back into the combustion chamber, is controlled (open loop and/or closed loop) in dependence upon the intake-manifold pressure for a switchover into the first mode of operation. In this way, it is achieved that a transition as uniform as possible is present with the switchover from the homogeneous operation into the stratified charge operation. In this connection, it is especially purposeful when the exhaust-gas feedback is adapted to the dynamic of the intake manifold.
In an advantageous embodiment of the invention, a constant quantity and especially a small quantity or even no exhaust gas is fed back in the second mode of operation. In the homogeneous operation, only a small or even no exhaust-gas feedback is therefore required. In this way, it is avoided in homogeneous operation that a feedback of exhaust gas which is too high leads to disturbances of the combustions in the combustion chambers.
In an advantageous improvement of the invention, for a switchover into the second mode of operation, an actual switchover is only made after a pregiven time duration. Because of the dynamic of the exhaust-gas feedback, a larger quantity of exhaust is fed back after a switchover which is to be made. If, under these preconditions, a switchover were made into the stratified charge operation, this could lead to combustion misfires or the like. Therefore, the actual switchover into the stratified charge operation is delayed. In this way, combustion misfires are reliably avoided. During this delay, t
Maienberg Uwe
Stuerz Manfred
Argenbright Tony M.
Ottesen Walter
Robert & Bosch GmbH
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