Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-03-02
2001-04-10
Solis, Erick (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S305000
Reexamination Certificate
active
06213087
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to a method of operating an internal combustion engine, in particular for a motor vehicle, in which fuel is injected directly into a combustion chamber either in a first mode during a compression period or in a second mode during an induction period, and in which the fuel quantity injected into the combustion chamber is open-loop and/or closed-loop controlled in varying ways in the two modes. Furthermore, the present invention concerns an internal combustion engine, in particular for a motor vehicle, having an injection valve, by which fuel can be injected directly into a combustion chamber either in a first mode during an induction period or in a second mode during a compression period, and having an electronic control unit for the varying open-loop control and/or closed-loop control of the fuel quantity injected into the combustion chamber in the two modes.
Systems of this type for the direct injection of fuel into the combustion chamber of an internal combustion engine are generally known. In this context, a so-called stratified operation, as the first mode, is distinguished from a so-called homogeneous operation, as the second mode. The stratified operation is employed particularly with smaller loads, whereas the homogeneous operation is used for larger loads applied to the internal combustion engine. In stratified operation, the fuel during the compression period of the internal combustion engine is injected into the combustion chamber, specifically into the immediate vicinity of a spark plug. The result is that it is no longer possible to achieve a uniform distribution of the fuel in the combustion chamber, but rather the fuel is immediately ignited by the spark plug. The advantage of stratified operation lies in the fact that the smaller loads that are applied can be handled by the internal combustion engine using a very small quantity of fuel. However, larger loads cannot be managed using stratified operation. In homogeneous operation, which is provided for these types of larger loads, the fuel during the induction period of the internal combustion engine is injected so that it is possible immediately to achieve a swirl effect and thus a distribution of the fuel in the combustion chamber. To this extent, homogeneous operation roughly corresponds to the modus operandi of internal combustion engines in which fuel is commonly injected into the intake pipe.
In both modes, i.e., in stratified operation and in homogeneous operation, the fuel quantity to be injected is open-loop and/or closed-loop controlled as a function of a multiplicity of input variables towards an optimal value with respect to fuel economy, emission reduction, and the like. The open-loop and/or closed-loop control, in this context, is different in the two modes.
SUMMARY OF THE INVENTION
An object of the present invention is to indicate a direct-injection internal combustion engine, in which a further reduction of fuel consumption is possible.
This object is achieved in a method of the type mentioned at the beginning or in an internal combustion engine of the type mentioned at the beginning, in that the first mode is, or can be, operated as the normal mode and the second mode as the exceptional mode.
The first and the second modes, i.e., the stratified operation and the homogeneous operation, are therefore not equal in terms of value or of usefulness. According to the present invention, the stratified operation is prescribed as the normal mode of the internal combustion engine, whereas the homogeneous operation is prescribed as the mode of the internal combustion engine only in exceptional cases. As a result of this evaluation or weighting of the two modes, it comes about that the stratified operation is always preferred. At the same time, this means that the mode is preferred using which it is possible to achieve further fuel economies, namely the stratified operation. The system according to the present invention is therefore designed such that the homogeneous operation, which increases energy consumption, is treated as the exception whereas the stratified operation, which reduces energy consumption, is designated as the normal mode. In this way, greater fuel economy is achieved using the internal combustion engine according to the present invention.
In one advantageous embodiment of the present invention, the exceptional mode is requested. For this purpose, it is particularly advantageous if in the electronic control unit a signal is present which constitutes a request for the exceptional mode. A request of this type can, for example, be made indirectly by the driver, who presses down on the accelerator in order thus, for example, to accelerate in the motor vehicle. This simultaneously constitutes an increase in the load placed on the internal combustion engine, which can no longer be handled by the internal combustion engine in the stratified operation but rather only in the homogeneous operation. However, if the internal combustion engine is in its normal mode, i.e., in the stratified operation, then it is necessary to shift from the stratified operation to the homogeneous operation. This shifting is initiated by the request for the homogeneous operation, i.e., the exceptional mode. The consequence of this is that the internal combustion engine switches over to the homogeneous operation, which increases the fuel consumption, only in response to a special request. In the normal state, on the other hand, the internal combustion engine is always run in the fuel-economizing stratified operation.
In one advantageous refinement of the present invention, the normal mode is always used if there is no request for the exceptional mode. As a result of this measure, the weighting or evaluation of the two modes is realized. Therefore, there is no request or the like for the normal mode, but rather the shift is always carried out to the normal mode, or the normal mode is in use, if there is no request for the exceptional mode. In this way the internal combustion engine is always operated, in the normal case, in a fuel-economizing stratified operation and is only operated in the homogeneous operation in exceptional cases by request. In this manner, the fuel consumption, as was already mentioned, is further optimized.
It is particularly advantageous if in the electronic control unit there is a signal that designates the state of the normal mode. This means that the signal indicates whether the internal combustion engine is in the normal mode, i.e., in stratified operation, or not. In this way also, particularly in the electronic control unit, the evaluation or weighting of the two modes is expressed.
In one advantageous embodiment of the present invention, the exceptional mode is only used if the internal combustion engine satisfies certain operating conditions. In this manner, it is achieved that the transition from the stratified operation to the homogeneous operation can take place without any undesirable changes in the rpm's of the internal combustion engine, in particular without intense vibration. Thus by taking the aforementioned operating conditions into account, it can be achieved that the passengers of the vehicle virtually fail to notice this transition.
In one advantageous refinement of the present invention, the exceptional mode is only used if the quantity of air in the combustion chamber falls below a preselected level. This constitutes one measure by which intensive vibration is reliably avoided in the transition from stratified operation to homogeneous operation of the internal combustion engine.
In one advantageous embodiment of the present invention, the exceptional mode is only used if a prescribed time duration has elapsed since the preceding use of the exceptional mode.
In a further advantageous embodiment of the present invention, use of the exceptional mode is only terminated if a prescribed time duration has elapsed since the last use of the normal mode.
The two aforementioned embodiments represent temporal debouncing. In particular,
Kenyon & Kenyon
Robert & Bosch GmbH
Solis Erick
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