Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-03-02
2001-10-16
Solis, Erik (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S436000
Reexamination Certificate
active
06302081
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating an internal combustion engine, in particular of a motor vehicle, in which fuel is injected directly into a combustion chamber either, in a first operating mode, during a compression phase or, in a second operating mode, during an intake phase; in which switching between the two operating modes occurs; and in which the operating variables influencing the actual torque of the internal combustion engine are controlled in open-loop and/or closed-loop fashion, as a function of a reference torque, differently in the two operating modes. The present invention further relates to an internal combustion engine, in particular for a motor vehicle, having an injection valve with which fuel can be injected directly into a combustion chamber either, in a first operating mode, during a compression phase or, in a second operating mode, during an intake phase; and having a control device for switching between the two operating modes and for differing open-loop and/or closed-loop control, in the two operating modes, of the operating variables influencing the actual torque of the internal combustion engine as a function of a reference torque.
BACKGROUND INFORMATION
Existing systems for directly injecting fuel into the combustion chamber of an internal combustion chamber switch between a first operating mode and a second operating mode.
A distinction is made in this context between a so-called stratified mode as a first operating mode, and a so-called homogeneous mode as a second operating mode. Stratified mode is used in particular at lesser loads, while homogeneous mode is utilized when greater loads are applied to the internal combustion engine.
In stratified mode, fuel is injected into the combustion chamber during the compression phase of the internal combustion engine, in such a way that at the moment of ignition, a fuel cloud is located in the immediate vicinity of a spark plug. This injection event can be accomplished in different ways. For example, it is possible for the injected fuel cloud already to be present at the spark plug during or immediately after the injection event, and to be ignited by it. It is also possible for the injected fuel cloud to be guided to the spark plug by a charging movement, and only then ignited. With both combustion methods, what is present is not a uniform fuel distribution but rather a stratified charge.
The advantage of the stratified mode is that in it, the lesser loads that are being applied can be handled by the internal combustion engine with a very small quantity of fuel. Greater loads, however, cannot be handled with the stratified mode.
In the homogeneous mode provided for such greater loads, fuel is injected during the intake phase of the internal combustion engine, so that the fuel can readily experience turbulence and thus be distributed in the combustion chamber. In this respect, homogeneous mode corresponds approximately to the method of operation of internal combustion engines in which fuel is injected in conventional fashion into the intake duct. If necessary, homogeneous mode can also be used at lesser loads.
In stratified mode, the throttle valve in the intake duct leading to the combustion chamber is opened wide, and combustion is controlled in open-loop and/or closed-loop fashion only by way of the fuel mass that is to be injected. In homogeneous mode, the throttle valve is opened or closed as a function of the requested torque, and the fuel mass to be injected is controlled in open-loop and/or closed-loop fashion as a function of the aspirated air mass.
In both operating modes, i.e., in stratified mode and in homogeneous mode, the fuel mass to be injected is additionally controlled in open-loop and/or closed-loop fashion, by a plurality of further operating variables, to a value that is optimum in terms of fuel economy, exhaust emissions reduction, and the like. The open-loop and/or closed-loop control is different in the two operating modes.
It is necessary to switch the internal combustion engine over from stratified mode to homogeneous mode and back again. Whereas in stratified mode the throttle valve is opened wide and air is thus supplied largely unthrottled, in homogeneous mode the throttle valve is only partially open and thus reduces the supply of air. Especially when switching over from stratified mode into homogeneous mode, the ability of the intake duct leading to the combustion chamber to store air must be taken into consideration. If it is not taken into account, the switchover can result in an increase in the torque delivered by the internal combustion engine.
SUMMARY
It is an object of the present invention to create a method for operating an internal combustion engine with which improved switching between the operating modes is possible.
This object is achieved according to the present invention in that a change in the actual torque during a switchover operation is detected; and that as a function thereof, at least one of the operating variables is influenced.
Based on the determination of changes in the actual torque during the switchover operation, it is possible to detect roughness or jerking during the switchover. Once jerking has been detected, the roughness can be counteracted by influencing operating variables. It is thereby globally possible to avoid roughness or jerking during the switchover from homogeneous operation to stratified operation or vice versa. The switchover operations between the two operating modes are thus improved, in particular, in terms of enhanced smoothness and thus enhanced comfort.
In an advantageous embodiment of the present invention, the actual torque is determined before and after a switchover operation. This represents a particularly easy possibility for sensing the change in the actual torque.
In an advantageous embodiment of the present invention, the change in the actual torque is detected as a function of the sensed rotation speed of the internal combustion engine. The result is that any change in the actual torque and thus any jerking or the like can be detected with the aid of the rotation speed sensor that is already present. Additional sensors or other additional components are thus not necessary.
In an advantageous embodiment of the present invention, roughness values are determined for the individual cylinders. From these roughness values, conclusions can be drawn as to changes in the actual torque of the internal combustion engine. Using the roughness values, it is thus possible to detect speed fluctuations or jerking of the internal combustion engine. The roughness values can be determined in various ways. For example, it is possible to provide a roughness sensor to measure the roughness values. The roughness values can also, for example, be derived from the rotation speed of the internal combustion engine. The roughness values represent an indication of torque differences between successive cylinders.
In an advantageous embodiment of the present invention, at least one of the operating variables influencing the actual torque is changed in both operating modes at a mutually corresponding operating point of the internal combustion engine, and at least one of the roughness values of the first operating mode is then compared to at least one of the roughness values of the second operating mode. The internal combustion engine is thus exposed to a change in each of the two operating modes.
The consequence of that change is determined in the form of a change in the roughness values. From that change in the roughness values, conclusions can be drawn as to possible torque differences between the two operating modes. Potential jerking upon switchover between the two operating modes can thus be detected in advance and prevented.
It is particularly advantageous if the operating variable is changed in cylinder-specific fashion in such a way that the delivered torque of successive cylinders changes, but the total torque of all the cylinders remains the same. The changes are thus performed in cylinder-specifi
Foerster Juergen
Koehler Christian
Mallebrein Georg
Mentgen Dirk
Moser Winfried
Kenyon & Kenyon
Robert & Bosch GmbH
Solis Erik
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