Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2000-10-17
2002-07-09
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C701S109000
Reexamination Certificate
active
06415779
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method and a device for fast automatic adaptation of air/fuel ratio for a fuel-injection engine, i.e. an internal combustion engine of the controlled ignition type fitted with a fuel-injection system, and having an oxygen sensor, commonly referred to as a &lgr; sensor, which detects the oxygen content of the exhaust gases.
The invention therefore relates to fuel-injection engines, in particular for motor vehicles, and a method of automatically adapting the control characteristics governing the fuel supply, i.e. a system of automatically adapting parameters governing charging of the engine cylinders, and which offers an improvement on the automatic adaptation method known from FR-A-2 708 047. The method of rapid automatic adaptation proposed by the invention may simultaneously also be a method of purging a circuit having a canister associated with the engine.
The invention also relates to an automatic adaptation device for implementing the improved method proposed by the invention and incorporates a computer, which computer at least controls the injection system but is preferably an engine control computer which additionally controls at least the ignition process.
BACKGROUND
It is common knowledge that, for a given type of engine, an adapted engine control parameter or variable, such as the quantity of fuel injected or the injection duration, given that the fuel flow rate-injection duration characteristic of the injectors is known, and which is referred to as a control variable throughout this description, is a known characteristic function which depends on parameters representative of the charging of each of the engine cylinders, referred to as charging parameters throughout this description, and such as the absolute pressure at the air intake manifold, the flow rate of the air admitted to the engine or alternatively the angle at which a throttle valve opens in a valve body on the air intake pipe to the engine, in combination with the speed or rotation speed of the engine. In particular, it is known that the basic fuel injection duration, from which the injection duration effectively applied to the injectors is obtained, is defined as a function of the absolute pressure in the air intake pipe to the engine by means of a characteristic curve which can be likened, in a steady state and across the greater part of the operating range of the engine, to a straight-line curve with a slope G, known as gain, and an initial abscissa D, referred to as shift, for a given engine speed. The increasing linear relationship between the basic injection duration TinjB and the absolute intake pressure P can therefore be written as follows:
TinjB
=(
P−D
)×
G,
(1)
where the intake pressure P represents the torque required from the engine, or load, at a given speed.
A known approach to controlling engine operation at an air/fuel ratio of around 1, corresponding to the stoichiometric mixture, is to determine an air/fuel ratio coefficient KO
2
which is used to correct the basic injection duration TinjB. This air/fuel ratio coefficient KO
2
is derived from a servoloop monitoring the air/fuel ratio R of the air-fuel mixture from an oxygen sensor positioned in the flow of the engine exhaust gas. In practice, the air/fuel ratio coefficient KO
2
is between 0.75 and 1.25 and constitutes a multiplicative correction factor for the basic injection duration TinjB, which is therefore corrected by acting on KO
2
to an air/fuel ratio R equal to 1. Acting on KO
2
generally consists in applying value transitions to this coefficient on either side of a mean value, generally set at 1, for operating the engine in open loop.
Simultaneously, another known approach is to adapt the coefficients D and G automatically as a means of keeping the air/fuel ratio coefficient KO
2
as close to its mean value as possible.
Due in particular to manufacturing tolerances, wear and/or the need to replace engine parts or components, the engines exhibit quite different characteristics from one engine to another. However, in order to ensure that engines continue to operate satisfactorily, there is a constant striving towards simultaneously obtaining an air/fuel ratio signal R and an air/fuel ratio coefficient KO
2
equal to 1 whilst automatically compensating for tolerances and drifts in engine characteristics by automatically adapting the coefficients D and G of the straight-line curve representing the operation of each engine.
A method of this type for automatically adapting the air/fuel ratio of an injection engine is known from FR-A-2 708 047 and uses a computer which, on the one hand, is connected at least to sensors monitoring engine operating parameters, from which the computer receives at least one engine speed signal and a signal enabling an engine charging parameter P to be determined, this being the absolute pressure in an air intake pipe to the engine downstream of a throttle member such as a butterfly valve controlling the air supply rate, and to an oxygen sensor in the engine exhaust gas, from which the computer receives an air/fuel ratio signal R, and, on the other hand, computes at least values of at least one control variable, namely injection durations to be transmitted to at least one injector, which are obtained from basic values for the control variable TinjB expressed as increasing linear functions of the charging parameter P and represented by straight-line curves, each defined by two coefficients, these being a shift D of the initial charging parameter and a gain G indicating the slope of the line such that TinjB=(P−D)×G, each basic value of the control variable TinjB being corrected to generate a corrected value for said control variable TinjCOR taking account of an air/fuel ratio coefficient KO
2
, to which value transitions are applied as a function of the air/fuel ratio signal R in the operating zones of the engine in closed loop, and fixed at a mean value in the operating zones of the engine in open loop in order to ensure that engine operation is centred an air/fuel ratio R equal to 1, the shift D and the gain G also being automatically adapted in cycles to ensure that the air/fuel ratio coefficient KO
2
remains close to its mean value, by correction of any shift of this coefficient KO
2
in taking account of the top and bottom values Ph and Pb of the charging parameter for operating points of the engine in a stabilized state.
The teaching of the above-mentioned document is based in particular, for a stabilized engine and depending on certain previous operating conditions of the engine, on enabling the air/fuel ratio to be automatically adapted by modifying at least the shift D and preferably only the shift, within a first operating range of the engine, at low intake pressure (for low charging parameter values) and by modifying at least the gain G and preferably only the gain within a second operating range of the engine, at high intake pressure (for high charging parameter values), these pressure ranges being set.
The disadvantage of this automatic adaptation system is that it is difficult to operate in practice due to the fact that the frequency at which the high-pressure operating range occurs, in the order of 70 kPa, and hence the opportunity of being able to take real and multiple measurements of engine operating parameters during service, is low within a standard cycle when driving a motor vehicle fitted with this engine in the city.
Furthermore, according to the above-mentioned document, whenever an automatic adaptation phase is initiated, it is allowed to continue for a maximum number of n1 cycles at most within the first operating range and for a maximum number of n2 cycles at most within the second operating range and a new automatic adaptation of shift D or gain G is not permitted until after all the automatic adaptation cycles permissible in gain and shift have been performed. The fact that the engine does not operate often enough at the high-pressure range but all the automatic adaptation cycles at
Dolinar Andrew M.
Hoang Johnny H.
Magneti Marelli France
Rudnick Piper
LandOfFree
Method and device for fast automatic adaptation of richness... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for fast automatic adaptation of richness..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for fast automatic adaptation of richness... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905115