Control method

Details Control method Control method

2000-01-13

2001-12-11

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Using multiple injectors or injections

C123S436000

Reexamination Certificate

active

06328014

ABSTRACT:

This invention relates to a control method for use in controlling the operation of a compression ignition internal combustion engine.
It is known to control the operation using the output of an algorithm, for example to derive a correction value or factor for use in determining the quantity of fuel which should be supplied to the cylinders of an engine in order to reduce cylinder-to-cylinder speed changes. The algorithm is typically supplied with data indicative of the speed of operation of the engine, for example by a rotary speed sensor which includes a camshaft or crankshaft mounted toothed wheel, and a sensor arranged to monitor the movement of the teeth of the wheel past a predetermined location. The algorithm typically uses the data indicative of the engine speed after each cylinder has passed its top-dead-centre position.
Where such a control method is used in controlling the operation of an engine having a fuel system arranged to deliver an initial, pilot injection to each cylinder followed by a main injection, it is difficult to determine from the output of the algorithm whether it is the quantity of fuel delivered during the pilot injection or that of the main injection which requires modification, and so the algorithm is not suitable for use in balancing the pilot fuel injection quantities.
According to the present invention there is provided a control method for controlling the operation of a compression ignition internal combustion engine comprising measuring the change in the engine speed which occurs during a period leading up to substantially the top-dead-centre position of a cylinder of the engine to obtain a measured engine speed change value, using the measured engine speed change value in a delta speed change algorithm, and using the output of the delta speed change algorithm to derive a pilot fuel correction factor.
The pilot fuel correction factor may be derived using a fuel balancing or correction algorithm.
The engine speed is conveniently measured for each cylinder of the engine over a period between 100° prior to the top-dead-centre position of each cylinder and the cylinder reaching substantially its top-dead-centre position.
The measured engine speed change value may be determined by measuring the engine speed when the engine occupies, for example, its 10° prior to top-dead-centre position and, for example, its top-dead-centre position, and calculating the difference between the measured engine speeds. The delta speed change algorithm is conveniently arranged to compare the measured engine speed change value with the equivalent value calculated for a previous cylinder of the engine. The fuel correction or balancing algorithm may be arranged to vary the quantity of fuel injected to each cylinder during the pilot injections of fuel to ensure that the engine speed change for each cylinder is substantially equal to that of the other cylinders.
The invention may be used in conjunction with a fuel correction or balancing algorithm for correcting or balancing the fuel quantities delivered in the main injections. As a result, the pilot and main injection quantities can be balanced at the same time.
In use, there may be circumstances, for example when the engine is operating at high speed or under a high load, in which balancing of the pilot injections is not necessary, and so the fuel correction or balancing algorithm may be disabled. There may also be circumstances in which balancing of the pilot injections is desirable, but engine conditions result in the output of the delta speed change algorithm being unreliable. In these circumstances, the pilot fuel correction factors used may be derived from factors calculated by the algorithm when the engine conditions gave rise to reliable algorithm outputs, for example when the engine was at idling speed and was operating under little or no load, or during a calibration operation, and stored in a suitable memory as a function of, for example, engine speed or load, vehicle speed, gear ratio or fuel pressure.
If desired, the same fuel correction or balancing algorithm may be used in controlling the fuel quantities used in both the pilot injection and the main injection. For example, after appropriate calibration has taken place, the engine may be operated using the fuel balancing or correction algorithm in conjunction with the output of the delta speed change algorithm, the fuel balancing or correction algorithm being used to control main injection using stored engine speed change values derived during the calibration operation or correction factors derived during calibration, and stored as a function of, for example, engine speed or load. If desired, when the engine is operating under conditions where a pilot injection is not necessary or balancing of the pilot injections is not required, then the fuel correction or balancing algorithm used to control the main injections may use the measured engine speeds and the output of the delta speed correction algorithm. In such an arrangement, the delta speed change algorithm output values or correction factors derived using the measured engine speeds may be used to update the values derived during calibration.
The operation of the delta speed change algorithm may be improved by correcting the calculated values of the engine speed change derived from the measured engine speed values to compensate for the local engine speed. It is known to use correction factors based upon the average engine speed measured over one or two crankshaft revolutions, but as the local engine speed (the speed over the period during which speed measurements are taken) may differ significantly from the average speed, such correction factors are inaccurate. It will be appreciated that the correction of calculated delta speed changes may have applications other than fuel correction or balancing, for example it may be used in misfire detection applications.


REFERENCES:
patent: 4539956 (1985-09-01), Hengel et al.
patent: 5117793 (1992-06-01), Taeu et al.
patent: 5582152 (1996-12-01), Drutel et al.
patent: 9-264160 (1997-10-01), None

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