Electricity: measuring and testing – Internal-combustion engine ignition system or device
Reexamination Certificate
2001-02-26
2003-02-11
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Internal-combustion engine ignition system or device
C123S491000
Reexamination Certificate
active
06518763
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control system for metering fuel to an internal combustion engine.
BACKGROUND OF THE INVENTION
A hot start of an internal combustion engine refers to restarting the engine after prolonged operation of the engine, especially under a load, with a brief interruption of operation following it. In the case of a brief interruption of operation of a hot engine, heat will form bubbles of fuel vapor in the fuel supply system that could cause problems during the next start-up if they were to occur directly in the injection valve. These fuel vapor bubbles prevent the regular metering of fuel. It is therefore customary to have a prolonged injection signal emitted under hot-start conditions so that in the event of a fuel vapor lock, a quantity of fuel sufficient for a safe start is supplied to the combustion process. Alternatively, a signal emitted to initiate the circulation of fuel through the valve, via a return line, will flush out bubbles of fuel vapor to prevent vapor lock.
In order to take measures to avoid problems in the case of a hot start of an internal combustion engine, the control system for fuel metering must recognize when a hot-start situation is present. In previous fuel metering control system for an internal combustion engine, a hot-start situation is assumed when the temperature of the coolant of the internal combustion engine is above a pre-assigned threshold temperature and the difference between the present intake air temperature and a stored temperature exceeds a pre-assigned magnitude. The hot-start situation is considered no longer to exist if the coolant temperature of the internal combustion engine lies below a second threshold temperature or if the internal combustion engine has taken in a predetermined quantity of air.
The disadvantage of these previous fuel metering control systems is that the temperature of the coolant is used as the decisive reference magnitude for recognizing a hot-start situation. An increase in coolant temperature may occur with considerable time delay with respect to the temperature in the combustion chamber and therefore also the injection valve. Thus, it may occur in practice that an internal combustion engine, after a cold start, may immediately be driven under a full load for a short time with a brief interruption of operation. In this case, the immediate environment of the combustion chamber and the injection valve is brought to a high operating temperature while the coolant itself remains relatively cool. During the interruption of operation, fuel vapor bubbles may form in the injection valve and make a restart difficult. This is because a hot-start temperature cannot be recognized based on the temperature of the coolant.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a control system or signal processing system for metering fuel to an internal combustion engine in such a way that a hot-start situation can be recognized under all operating conditions of the internal combustion engine using a simple cost-effective method.
The method of the present invention starts with the assumption that the main problem of a hot start is caused by the vapor lock inside the injection valve. The detection of the temperature at the injection valve by temperature sensors, however, would involve a considerable cost because there would have to be room to install such sensors, and a signal line would have to run from the sensor. In addition, it would be necessary to monitor the sensor in order to test the functional capability of the sensor.
The method of the present invention makes use of the fact that the resistance of an electrical conductor changes with temperature. This is also true for the electrical conductors located on the electrical opening device of the injection valve which generally have the form of a magnetic coil. If these conductors are carrying current, then the signal processing system provided for supplying fuel can determine, by known methods, the flow of current as well as the present voltage. Using Ohm's law, these values enable calculation of the actual present electrical resistance of the conductor. From the present electrical resistance and also using the above-mentioned signal processing system, the present temperature at the location of the electrical conductor can be determined directly on the injection valve. By comparison of the present temperature determined with a pre-assigned calibrated temperature value whose value is determined empirically as the limiting temperature for a hot-start situation, and which is stored in a signal processing system, the hot-start situation can be identified very precisely as a function of the temperature status at the injection valve. The hot-start situation can be identified independent of prior or subsequent states in other locations in the internal combustion engine. Special sensors and signal transmission lines and terminals for their functional control are not required.
By choosing a material for the electrical conductor whose temperature-variable resistance is known, one may influence the response behavior of the control system for recognizing a hot-start situation. The values of the present temperature on the injection valve as a function of voltage and resistance on the electrical conductor of the opening device may be stored in a memory in the signal processing system. Accordingly, the temperature values are available in real time even in the case of very small computational power of the signal processing system.
When the control system of the present invention is used on different internal combustion engines of a model series, varying operating conditions can be allowed for by using additional memory with correction factors. These correction factors can also be stored in a memory for the control system individually during the programming of the computer control system for a specific internal combustion engine, or they can be stored in a fixed memory and called up specifically for a given model series.
The method of the present invention may be executed in any known electronic engine control system or signal processing system.
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DeVries Christopher
General Motors Corporation
LeRoux Etienne P
Oda Christine
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