Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-11-22
2001-08-14
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S295000
Reexamination Certificate
active
06273068
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating a fuel supply system for an internal combustion engine, particularly of a motor vehicle, in which a fuel quantity to be injected is determined by a control unit, the fuel quantity to be injected being initially increased during a start of the internal combustion engine and then being reduced again, and in which the fuel quantity to be injected is injected into a combustion chamber by a fuel injector. Furthermore, the present invention relates to a fuel supply system for an internal combustion engine, particularly of a motor vehicle, the fuel supply system having a control unit for determining a fuel quantity to be injected, it being possible to initially increase the fuel quantity to be injected during a start of the internal combustion engine and then to reduce it again, and having a fuel injector for injecting the fuel quantity to be injected into a combustion chamber.
BACKGROUND INFORMATION
Greater and greater demands are made on an internal combustion engine, for example, of a motor vehicle with regard to a reduction of the fuel consumption and the produced exhaust gases while, at the same time, desiring an increased power. For this purpose, modern internal combustion engines are provided with a fuel supply system in which the feeding of fuel into the combustion chamber of the internal combustion engine is controlled and/or regulated electronically, in particular, using a computer-aided control unit. In this context, it is possible to inject the fuel into an air intake tube of the internal combustion engine or directly into the combustion chamber of the internal combustion engine.
In the last-mentioned type, the “gasoline direct injection”, it is required to inject the fuel into the combustion chamber under pressure. For this purpose, provision is made for an accumulator into which the fuel is pumped by a pump and put under a high pressure. From there, the fuel is injected directly into the combustion chambers of the internal combustion engine via fuel injectors. In a homogeneous operation, the injection begins during the induction period of the respective cylinder, whereas in a fuel-saving shift operation, the injection is carried out during the compression stroke.
In both indicated methods of operation, the fuel quantity to be injected directly into the combustion chambers of the internal combustion engine via the fuel injectors, such as, possibly, also the start of injection or the end of injection are determined in advance by the control unit as a function of a plurality of performance quantities of the internal combustion engine. Subsequently, the fuel injectors are controlled by the control unit according to the determined values.
To start the internal combustion engine, special starting processes are provided. Particularly at low outside temperatures, the fuel quantity to be injected must be increased in the first injection in comparison with an internal combustion engine at operating temperature. This is necessary in order that, during the start, a sufficient quantity of low-boiling gasoline constituents are present for an ignitable air/fuel mixture. The increased fuel quantity during the start is also required to build up a wall film of fuel on the inside walls of the cylinders. During the following injections, the indicated increased fuel quantity to be injected is reduced to the normal fuel quantity to be injected for the internal combustion engine at operating temperature again.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for operating a fuel supply system as well as a fuel supply system for an internal combustion engine which enable an improved start of the internal combustion engine, particularly at low outside temperatures.
This objective is achieved according to the present invention in a method and a fuel supply system by checking whether a combustion has taken place in the cylinder, and, if no combustion has taken place, the fuel quantity to be injected is not reduced, or is not reduced to the same extent as when a combustion has taken place.
Consequently, a greater reduction of the fuel quantity to be injected in the next planned combustion in the respective cylinder is prevented exactly when no combustion has taken place. In this case, no significant heating of the cylinder or the internal combustion engine has occurred either. Therefore, the following planned combustion still requires an increased fuel quantity to make an ignitable air/fuel mixture available in the respective cylinder, and to build up a wall film in the combustion chamber of this cylinder.
This requirement is taken into account by the present invention. Thus, the present invention avoids a greater reduction of the fuel quantity to be injected in the absence of a combustion than it would be the case, for example, in a time-dependent reduction of the fuel quantity. Consequently, the present invention guarantees a secure starting operation even at low outside temperatures, and prevents, inter alia, misfiring during the start or even an unsuccessful starting operation.
In an advantageous embodiment of the present invention, the fuel quantity to be injected is reduced to a greater degree when a combustion has taken place. Only in the case that a combustion has actually occurred in one of the cylinders, the fuel quantity to be injected into this cylinder in the next planned combustion is markedly reduced. Because of the occurred combustion and the associated heating of the respective cylinder, in the next injection into this cylinder, it is no longer necessary to make a fuel quantity available which is increased to the same degree as before. Due to the heating, a smaller fuel quantity is sufficient to produce a combustion, and to form a sufficient wall film in the combustion chamber of the cylinder. This circumstance associated with the heating of the cylinder is taken into account by the present invention. The present invention checks specifically whether or not a combustion has actually taken place. Only in the first-mentioned case, the fuel quantity to be injected for the next combustion in this cylinder is considerably reduced.
In an advantageous embodiment of the present invention, the check as to whether a combustion has taken place is carried out as a function of one or more of the following performance quantities of the internal combustion engine:
increase of temperature of the respective cylinder or of all cylinders;
increase of pressure in the respective cylinder;
increase of speed of the internal combustion engine;
the lambda value of the exhaust gas of the respective cylinder or of all cylinders, which is yielded from a probe that evaluates the partial oxygen pressure;
quantity of unburnt gasoline in the exhaust gas of the respective cylinder or of all cylinders;
changes of the ignition voltage.
Using these performance quantities of the internal combustion engine, it is easy to determine whether or not a combustion has taken place in one of the cylinders. If, for example, the temperature of a specific cylinder rises after a firing of the spark plug of this cylinder, then, it can be concluded from this that this firing of the spark plug has caused an ignition of the air/fuel mixture in this cylinder, and thereby an actual combustion.
It is particularly advantageous to check whether a break-off criterion such as the reaching of a speed threshold is fulfilled, and, if the break-off criterion is fulfilled, to terminate the process. If, for example, a certain speed threshold is reached or exceeded, then this means that the starting operation is finished. In this case, the checking of the combustions in the individual cylinders can be ceased, and the fuel quantity to be injected can be injected into the combustion chambers of the internal combustion engine as a function of the normal determination by the control unit.
It is particularly advantageous to use the method on each of the cylinders of the internal combustion engine individually. In doing so, the start operati
Bochum Hansjoerg
Daeubel Ralf
Grass Gerd
Joos Klaus
Weiss Ruediger
Gimie Mahmoud
Kenyon & Kenyon
Robert & Bosch GmbH
Yuen Henry C.
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