Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
2003-02-27
2004-06-29
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
C123S674000, C123S339120, C123S436000
Reexamination Certificate
active
06755176
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based on Japanese Patent Application No. 2002-56492 filed on Mar. 1, 2002 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection quantity controller for an internal combustion engine. More specifically, the present invention relates to a pilot injection quantity controller for an internal combustion engine, capable of driving a fuel injector a plurality of times while the engine is in a compression stroke to inject a small quantity of fuel at least once for pilot injection before main injection.
2. Description of Related Art
A conventional common rail type fuel injection system injects a high-pressure fuel stored in a common rail under pressure into the cylinders of a multi-cylinder diesel engine. This common rail type fuel injection system performs pilot injection several times prior to main injection that makes the engine produce torque to reduce combustion noise and engine vibrations by stabilizing combustion from the start of main injection and to improve the quality of the exhaust gas.
Usually, the variation of an actual injection quantity in an injection command pulse time (TQ pulse width) for which the fuel injector injects fuel is corrected by individually adjusting the fuel injectors of the cylinders. Since the pilot injection quantity is as small as 5 mm
3
/st, the pilot injection cannot achieve its purpose satisfactorily due to the variation of the actual injection quantity in the injection command pulse time, and the failure of pilot injection or injection of an excessive quantity of the fuel due to the deterioration of the ability of the fuel injector resulting from the secular change of injection quantity. The actual injection quantity injected by the fuel injector in the injection command pulse time tends to vary in a wide range when the injection pressure is high. Thus, it is very difficult to guarantee the performance of the fuel injector when the injection quantity is as small as on the order of 1 mm
3
/st.
An inter-cylinder engine speed variation injection quantity correcting technique (FCCB) has been proposed to solve the foregoing problems. Application of this correcting technique is limited only to the correction of fuel injection pressure during idling, and this correcting technique cannot achieve correct correction of fuel injection pressure while the vehicle is running and when fuel injection pressure is high.
A method of proportionally distributing an injection quantity correction to two injection cycles, i.e., a pilot injection cycle and a main injection cycle is proposed in JP-A 2-23252. Application of this method, similarly to that of the foregoing known technique, is limited to the correction of fuel injection pressure during idling, and this method is unable to achieve accurate correction. Since this method distributes an injection quantity correction to the pilot injection cycle and the main injection cycle in proportion to the ratio of a pilot injection quantity to a total injection quantity and the ratio of a main injection quantity to the total injection, quantity, respectively, the method determines an estimated fuel injection quantity correction and is unable to quantitatively determine the divergence of an injection quantity relative to an injection command pulse time for the injector.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an injection quantity controller for an internal combustion engine, capable of quantitatively determining an actual injection quantity to be injected in an injection command pulse time by an injector.
According to a first aspect of the present invention, an injection quantity controller for an internal combustion engine calculates a learning control mode injection quantity according to the operating condition of the engine when learning executing conditions dependent on a predetermined operating condition of the engine or operating conditions for the engine are valid, substantially uniformly divides the learning control mode injection quantity by n, achieves inter-cylinder engine speed variation correction for individually correcting injection quantities for cylinders to smooth engine speed variation in each cylinder by measuring engine speed variation in each cylinder while n split injection cycles are performed, and comparing the engine speed variations in all the cylinders with a mean value, and achieves mean engine speed correction by measuring the mean engine speed while the n injection cycles are performed, and uniformly correcting the injection quantities for all the cylinders so that the mean engine speed is maintained at the desired engine speed for mean engine speed correction.
Furthermore, the injection quantity controller calculates, for each cylinder, a first injection quantity correction corresponding to the deviation of a measured engine speed variation in each cylinder from a mean engine speed variation of engine speed variations in all the cylinders, calculates a uniform second injection quantity correction for all the cylinders necessary to maintain the mean engine speed at the desired engine speed, and adds up a value obtained by dividing the first injection quantity correction for each cylinder by n and a value obtained by dividing the uniform second injection quantity correction for all the cylinders by n. Thus, the difference between an actual injection quantity and an injection quantity to be injected by the injector in the command injection pulse time, and the deterioration of the performance of each injector due to the secular change of injection quantity can be quantitatively determined for each cylinder. The relation between an ideal command injection pulse time and an injection quantity can be determined by adding up and storing the difference and the learned value learned by the preceding learning cycle as a learned fuel injection quantity for each cylinder.
The present invention may be implemented in the following manner.
The first and the second correction calculating means calculate the first injection quantity correction for each cylinder and the uniform second injection quantity correction for all the cylinders for a plurality of different fuel injection pressure levels, and the learned value storage means updates and stores learned values for the plurality of different fuel injection pressure levels. Thus, the difference between an injection quantity to be injected in the injection command pulse time by the injector and an actual injection quantity can be quantitatively determined in a state where the engine is in operation even at a high fuel injection pressure and at a very small injection quantity, which is difficult to guarantee even by the single injector.
The learned values stored by the learned value storage means for fuel injection pressure levels other than the plurality of different fuel injection pressure levels are determined by interpolation. Thus, the learned values stored by the learned value storage means for the entire working range of fuel injection pressure in an actual vehicle including fuel injection pressures in the learning control mode can be used as corrections to be reflected in calculating the fuel injection quantity for each cylinder. Consequently, an ideal correlation between command injection pulse time and fuel injection quantity can be maintained.
The learned value indicates a deviation of an actual injection quantity from an injection quantity to be injected in the command injection pulse time for each fuel injection pressure and each cylinder of the engine.
It is known that a temporary learned value including a change, caused by load on the engine, of an engine demand injection quantity is abnormally greater than other temporary learned values. Therefore, the injection quantity controller is provided with the temporary learned value storage means capable of dividing the learned control mode injection quantity into substantially equal n injection qu
Hiroi Taiyo
Takashima Yoshimitsu
Takeuchi Katsuhiko
Yoshidome Manabu
Denso Corporation
Nixon & Vanderhye P.C.
Wolfe Willis R.
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