Internal-combustion engines – Two-cycle – Rear compression
Patent
1998-04-23
1999-08-10
McMahon, Marguerite
Internal-combustion engines
Two-cycle
Rear compression
F02B 300
Patent
active
059342307
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a method for supplying fuel to a combustion engine which has an air inlet provided with a gas valve and an output shaft and wherein a fuel line in which a fuel supply device is arranged debauches into the air inlet, comprising of providing a pump with an adjustable, substantially continuous flow rate for the fuel supply device, determining the position of the gas valve, determining the rotation speed of the shaft, ascertaining the required fuel flow rate and adjusting the pump accordingly.
A method of this kind is known from U.S. Pat. No. 4,048,964. The main control signal for adjusting the pump is obtained from a volumetric air flow meter. The derived signal is further adjusted with signals representing the position of the gas valve and the rotational speed of the motor shaft, amongst other signals.
Due to the delay of the air flow meter, the control of the combustion engine has a considerable time constant, at first affecting the accurate control of the fuel supply.
The invention now has for its object to provide a method for supplying fuel which enables very rapid control such that this is suitable for fast-running engines, such as two-stroke racing engines which can have a rotation speed of up to 18,000 rpm.
This object is achieved with the method according to the invention in that the required fuel flow rate is ascertained with the determined position of the gas valve and the determined rotation speed of the shaft. Both the gas valve position and the rotation speed can be determined with a very small time constant.
The required fuel flow rate can be calculated for instance with a suitable algorithm. Preferably however, the required fuel flow rate is determined on the basis of a pre-configured matrix in which various gas valve positions and shaft rotation speeds are related to an associated fuel flow rate suitable for a desired operating mode of the engine. A high processing speed can be hereby achieved.
The matrix can be configured by calculation. The matrix is preferably at least partially configured by including therein values wherein the oxygen content of exhaust gases determined with a lambda probe arranged in an outlet of the engine has an optimal value. It is of course also possible herein to use a self-learning method, wherein the values stored in the matrix are gradually optimized during operation of the engine on the basis of simultaneously performed measurements with the lambda probe.
A further refinement of the method according to the invention is achieved by determining at least one parameter, such as the absolute pressure of air flowing through the air inlet, and correcting the determined fuel flow rate accordingly. As for instance the air pressure, air temperature and air humidity vary, modified fuel flow rates can be provided so that a desired optimum operation is obtained under all operating conditions.
The step of determining a rate of change of the shaft rotation speed and adjusting the fuel flow rate based on that rate of change, for a predetermined time duration, is preferably applied particularly in the case of fast-running engines such as racing engines. Due to the "predictive" control a time constant for the control practically equal to zero can be realized. The combustion engine will thus herein obtain the optimum fuel supply at virtually any given moment, both during constant and greatly varying operating conditions.
The invention likewise relates to and provides a combustion engine comprising at least one cylinder, a reciprocally moveable piston therein which can drive an output shaft via a transmission, an air inlet which is connected to the cylinder and in which is arranged a gas valve, fuel supply means debauching into the air inlet and comprising a pump with an adjustable, substantially continuous flow rate, control means for controlling the pump, sensors connected to the control means for at least the shaft rotation speed and the gas valve position, wherein the control means are programmed such that they c
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Uytdewilligen Frederikus
Wentink Raymond
McMahon Marguerite
Tumic Research B.V.
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