Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
2002-07-12
2003-06-17
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
C123S399000, C123S480000
Reexamination Certificate
active
06578546
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method and a device for controlling an internal combustion engine, in particular a spark ignition engine with a direct fuel injection.
Ever greater requirements are being made of modern internal combustion engines, for example, in terms of reducing the fuel consumption and the emitted pollutants and in terms of a fault-free operation. The requirements are to be fulfilled under all load states of the internal combustion engine and even when changing between different load states. The various load states result essentially from the current driving situation taking into account a driver's requirement for a reduction or an increase in the torque made available by the internal combustion engine, wherein the requirement is expressed by the driver of a vehicle having the internal combustion engine.
In controllers of the type under consideration here, the determination of a desired torque or torque setpoint value corresponding to the driver's requirement is carried out on the basis of the position of at least one operator control element which can be actuated by the driver and which is generally the accelerator pedal. In vehicles with a spark ignition engine, the torque setpoint value is converted into a setpoint position for the throttle valve, which is carried out in vehicles with an electronic engine power controller (EGas, electronic gas pedal) electronically through the use of an electromotive throttle valve adjustment. Also, if appropriate, in addition to the ignition angle or injection angle which is to be set, the fuel quantity which is necessary to generate the desired torque and which is to be metered to the internal combustion engine is determined, for example, by calculation. By metering fuel to the internal combustion engine the fuel quantity which is determined and, if appropriate, by correspondingly setting the ignition angle or injection angle and/or further control variables, a torque which corresponds to the desired torque is generated. The fuel is metered into a combustion chamber of the internal combustion engine, preferably through the use of fuel injection, in particular through the use of a direct injection.
In conventional controllers, the intake air which is drawn in by the internal combustion engine, more specifically an air quantity signal or air mass flow rate signal which represents this intake air serves as a reference variable for determining the fuel quantity to be metered. An air quantity meter provides information on the intake air quantity to the controller. Further measuring pickups or sensors determine all the other data which are necessary for the allocation of fuel and signal the data, in particular data referring to the engine speed and the load state of the internal combustion engine, to the controller. The optimum parameters, in particular for the fuel quantity to be injected or the injection time, if appropriate the ignition angle to be set and/or the air charge to be metered, are determined from these input variables. In modern controllers, the assignment of the control variables to the input variables is carried out through the use of corresponding characteristic diagrams (input-output maps) of the controller.
In addition to the control of the quantity of the fuel/air mixture, a precise control of the mixture composition, that is to say of the fuel enrichment in the fuel/air mixture is necessary in order to adapt to different operating states of the internal combustion engine. The fuel/air mixture ratio is characterized, as is known, by the air ratio &lgr; which expresses the ratio between the supplied air quantity and the theoretical air requirement for complete combustion. Here, &lgr;=1 corresponds to an ideal value (homogeneous mixture), values of &lgr;<1 correspond to a deficit of air or a rich mixture and are set, for example, when the engine is started and in the full load range, and values of &lgr;>1 correspond to an excess of air or a lean mixture such as is desired, for example, in the partial load range in order to achieve a particularly economical operation.
In modern internal combustion engines with direct fuel injection, the fuel quantity to be metered is determined on the basis of different characteristic diagrams such that the fuel quantity is adapted to the load state, each characteristic diagram corresponding to a specific mode of operation. A stratified operating mode with a very lean mixture which is combustible only in the vicinity of the spark plug, a homogeneous, uniformly lean operating mode with excess air (economical driving) and a homogenous operating mode (&lgr;=1) are selected, for example, as operating modes. Switching over between these operating modes is carried out as a function of the driver's requirements and the current driving situation. The switching over can lead to jumps in the torque that is output by the internal combustion engine. These torque jumps can have disruptive and annoying effects such as jolting or shuffling when driving.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device for controlling an internal combustion engine which overcome the above-mentioned disadvantages of the heretofore-known methods and devices of this general type and which, in particular, provide a jolt-free or shuffle-free operation of internal combustion engines with direct fuel injection when changing between operating modes.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for controlling an internal combustion engine, the method includes the steps of:
determining a desired torque based on a position of at least one operating control element actuatable by a driver;
determining a fuel quantity which is to be metered to the internal combustion engine and which is necessary to generate the desired torque, by performing the steps of:
determining a normal fuel quantity based on a given normal efficiency;
determining a relative efficiency based on current operating conditions of the internal combustion engine; and
correcting the normal fuel quantity by using the relative efficiency in order to determine the fuel quantity which is to be metered to the internal combustion engine; and
generating a torque of the internal combustion engine corresponding to the desired torque by metering the fuel quantity to the internal combustion engine.
According to the invention, several steps are carried out when determining the fuel quantity to be metered, in particular when determining the fuel quantity to be injected. Here, the intake air quantity is not used, as hitherto, as a reference variable, but rather the efficiency of fuel metering operations is used as the control variable for determining the correct fuel metering quantity. Firstly, in reaction to the torque demand derived from the driver's requirement, an assumed or predefined normal efficiency is used as the basis for determining a normal fuel quantity or for determining a variable representing this normal fuel quantity corresponding to this efficiency. The term “efficiency” as used in the instant application represents the efficiency with which a fuel quantity which is metered, for example by an injection, is converted into a torque which is generated by the internal combustion engine on the basis of this fuel quantity. It goes without saying that this efficiency depends not only on the metered fuel quantity but also in particular on the time of the fuel quantity metering operation during a power stroke and on the current composition of the mixture of fuel and air. The efficiency, which may be present as a dimensionless value, changes depending on the operating point. The normal efficiency forms a reference variable which corresponds to an assumed normal operating state, for example the described homogeneous operation with &lgr;=1. For other influencing variables which define the operating state, it is also possible to assume normal values or opti
Jelden Hanno
Krebs Rudolf
Schultalbers Winfried
Argenbright Tony M.
Beck Manfred
Greenberg Laurence A.
Stemer Werner H.
Volkswagen Aktiengesellshaft
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