Knock control by reduction of injection period

Details Knock control by reduction of injection period Knock control by reduction of injection period

1991-12-06

1992-11-17

Argenbright, Tony M.

Internal-combustion engines

Charge forming device

Including cylinder pressure or temperature responsive means

123531, F02D 4114, F02D 4134

Patent

active

051634058

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the controlling of the operation of an internal combustion engine and in particular to taking corrective action upon the occurrence of "knock" arising from detonation rather than controlled combustion of part of the fuel/air mixture.
"Knock" is a well-known problem in the operation of internal combustion engines and is a particular problem when an engine is subjected to transient high load conditions. It is known to provide engines with a "knock" sensor, usually in the form of a vibration sensor, to either issue an appropriate warning to the engine operator or to activate an appropriate automatic corrective procedure. Known corrective procedures are usually to either retard the ignition timing of the engine, or to increase the fuelling rate of the engine. Controlling the level of "knock" by retarding ignition timing and/or the use of an increasing fuelling rate resulting in a rich mixture may lead to problems in emissions control or power output.
It is the object of the present invention to provide a system for controlling "knock" in internal combustion engines which will provide an effective response to the detection of "knock" to control same, and has a relatively minor influence on emission levels in the engine exhaust.
With this object in view, there is provided according to the present invention, a method of operating an internal combustion engine to control "knock" therein, comprising injecting a metered quantity of fuel entrained in a gas directly into the engine combustion chamber, controlling the timing of injection by setting the time of the end of the period of injection in relation to the engine cycle, and reducing the duration of the injection period in response to detection of "knock". in the engine above a predetermined level.
Preferably upon detection of "knock" above said predetermined level, the duration of injection is reduced by a preset initial amount, and thereafter if "knock" persists, by a preset additional amount, or several thereof, until "knock" ceases or the detected level falls below said predetermined level. Normally the preset initial amount of reduction of the duration of injection is greater than the subsequent preset additional amounts. Thus, upon the detection of "knock" above the predetermined level, there will be an initial reduction in the duration of injection, that initial amount being preset to achieve a cessation of "knock" under normal circumstances, and one or more preset additional amounts of adjustment are required only under severe "knock" conditions.
Conveniently, after "knock" has ceased as a result of a reduction in the duration of injection, that duration is increased at a predetermined rate to its normal level preferably in a step-wise manner so that there will not be a sudden variation in the injection period, which can in some circumstances, re-initiate "knock" in the engine.
As is common practice, both ignition timing and injection timing are set on the basis of degrees of rotation of the crankshaft prior to the top dead centre (TDC) position of the piston of the particular cylinder. The duration of the period of injection can be similarly measured in degrees of angle of rotation of the crankshaft or on a time base. The present proposal to decrease the duration of the period of injection is based on the timing of the completion of injection be set on an angle of rotation prior to TDC and the duration of injection being real time based measured forward from the injection completion timing.
As is known, "knock" or detonation of the fuel commonly initiates in areas of minimal clearance between the piston and the wall of the combustion chamber, usually the cylinder head, and such areas of minimum clearance are normally located around the perimeter of the principal combustion area. The present invention by reducing the period of injection from a set completion timing, hence reducing the time period between commencement of injection and commencement of ignition results in less time for the fuel to travel to those areas of high compr

REFERENCES:
Translation of cited passage at p. 307 of a Taiwanese text "Internal Combustion Engines" (translation provided).

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