The invention relates to a method for operating an internal combustion engine especially of a motor vehicle wherein the fuel, which is to be injected for a combustion, is directly injected into a combustion chamber during an intake phase and during a compression phase. Furthermore, the invention relates to an internal combustion engine especially for a motor vehicle having an injection valve with which the fuel, which is to be injected for a combustion, can be injected directly into a combustion chamber during an intake phase and during a compression phase. The engine also includes a control apparatus for the open-loop control and/or closed-loop control of the fuel mass injected into the combustion chamber.
Systems for the direct injection of fuel into the combustion chamber of an internal combustion engine are generally known. In these systems, one differentiates a so-called stratified operation and a so-called homogeneous operation. The stratified operation is especially used for lower loads; whereas, the homogeneous operation is used for larger loads applied to the internal combustion engine.
In the stratified operation, the fuel is injected into the combustion chamber during the compression phase of the engine so that a fuel cloud is located in the immediate vicinity of a spark plug at the time point of the ignition. This injection can take place in different ways. Thus, it is possible that the injected fuel cloud is located at the spark plug already during the injection or directly after the injection and is ignited thereby. Likewise, it is possible that the injected fuel cloud is guided to the spark plug by a charge movement and is only then ignited. In both combustion processes, no uniform fuel distribution is present. Instead, there is a stratified charge.
The advantage of the stratified operation is that the applied lower loads can be handled by the engine with only a very small quantity of fuel. Larger loads can, however, not be satisfied by the stratified operation.
The fuel is injected during the intake phase of the engine in homogeneous operation provided for such larger loads so that a swirling and therefore a distribution of the fuel can still easily take place in the combustion chamber. To this extent, the homogeneous operation approximately corresponds to the operation of engines wherein fuel is injected into the intake manifold in the conventional manner. The homogeneous operation can be utilized, as required, also for lesser loads.
In the stratified operation, the throttle flap is opened wide in the intake manifold leading to the combustion chamber and the combustion is open-loop controlled and/or closed-loop controlled essentially only by the fuel mass to be injected. In the homogeneous operation, the throttle flap is opened or closed in dependence upon the requested torque and the fuel mass, which is to be injected, is open-loop controlled and/or closed-loop controlled in dependence upon the inducted air mass.
In both modes of operation, that is, in the stratified operation and in the homogeneous operation, the fuel mass, which is to be injected, is open-loop controlled and/or closed-loop controlled additionally in dependence upon a plurality of additional input quantities to an optimal value with respect to fuel saving, exhaust-gas reduction and the like. The open-loop control and/or closed-loop control is then different in the two modes of operation.
It is possible to combine the two described modes of operation with each other. This is known as a so-called double injection. For this purpose, the fuel mass is determined which in total, is to be injected. Then, a first part of the fuel mass to be injected is injected during the intake phase and the remaining second part of the fuel mass to be injected is injected into the combustion chamber directly thereafter during the compression phase. The fuel mass, which is to be injected, for one and the same combustion is therefore injected into the combustion chamber of the engine with the aid of two injections.
The advantage of a double injection of this kind is that an abrupt switchover between the two modes of operation is avoided, that is, a switchover between the homogeneous operation and the stratified operation and back. In lieu thereof, the switchover is xe2x80x9cblurredxe2x80x9d over a wide range in that, for example, the fuel mass, which is to be injected during the intake phase, is slowly reduced and the fuel mass which is to be injected during the compression phase, is slowly increased.
Likewise, it is possible to provide a tank venting for the engine. Here, the so-called regeneration gas, which is vaporized in a fuel tank, is collected and supplied to the combustion. The advantage of a tank venting of this kind is that the fuel, which is contained in the regeneration gas, does not escape to the ambient but is used by the engine.
The object of the invention is to provide a method for operating an internal combustion engine as well as to provide an internal combustion engine wherein the advantages of the double injection and the tank venting are present.
This object is achieved in accordance with the invention in a method of the kind referred to above in that a regeneration gas is supplied to the combustion chamber during the intake phase. The object according to the invention is achieved in an internal combustion engine of the kind initially mentioned above in that a regeneration gas can be supplied to the combustion chamber during the intake phase by the control apparatus.
By supplying the regeneration gas during the intake phase, the breakdown of the entire quantity of fuel to be injected to the intake phase and the compression phase is not affected or even disturbed. The accuracy especially of the fuel mass, which is to be injected during the compression phase, is therefore maintained undiminished. The advantage is achieved notwithstanding that the regeneration gas is supplied to the combustion chamber and therefore to the combustion. The invention therefore combines the advantages of the direct injection (especially of the reduced fuel consumption and the lower discharge of toxic substances of the stratified operation) with the advantages of the tank venting, especially the complete utilization also of vaporizing fuel.
It is especially advantageous when fuel is injected and regeneration gas is supplied to the combustion chamber during the intake phase and when fuel is injected into the combustion chamber during the compression phase but no regeneration gas is supplied.
In an advantageous embodiment of the invention, the fuel mass, which is supplied in total into the combustion chamber during a single combustion, is composed of a first part and a second part. The first part is supplied during the intake phase and the second part is injected during the compression phase. The first part is put together from a third injected part and from a fourth part comprising the regeneration gas.
In an advantageous embodiment of the invention, for the first part of the total mass of supplied fuel, the third injected part is reduced and the fourth part made up of the regeneration gas is increased.
In this way, it is achieved that as much vaporized fuel as possible is supplied to the combustion chamber of the engine. The use of the vaporized fuel is thereby optimized.
It is especially advantageous when so much regeneration gas is supplied to the combustion chamber that the third injected part reaches a minimum value or zero.
The realization of the method of the invention in the form of a control element is especially significant with this control element being provided for a control apparatus of an internal combustion engine, especially of a motor vehicle. A program is stored on the control element which is capable of being run in a computer apparatus and especially in a microprocessor and is suitable for carrying out the method of the invention. In this case, the invention is realized by a program stored on the control element so that this control element, which is provided with the program, can define the invention in the same manner as the method for whose execution the program is suitable. As a control element, especially an electrical storage medium can be applied, for example, a read-only-memory.
Additional features, application possibilities and advantages of the invention become apparent from the following description of the embodiments of the invention which are shown in the figures of the drawing. Here, all described or illustrated features constitute the subject matter of the invention by themselves or in any desired combination independently of their combination in the patent claims or their dependency as well as independent of their formulations or illustration in the description or in the drawing.