Method of determining in real time the flow rate characteristic of a fuel injector
First Claim
1. A method of determining the flow rate characteristic of at least one electrically-controlled fuel injector feeding an internal combustion engine and mounted in a fuel feed circuit of said engine, the determination being in real time and as a function of an injection control duration, and said circuit comprising at least one pump fed from a fuel tank and connected to a common rail for feeding fuel to the injectors of the engine, each injector being controlled by an engine control unit, including at least one calculator and at least one memory, such that on each cycle of the engine, each injector delivers a mass of fuel to the engine as determined by said injector flow rate characteristic, which expresses the mass injected as an increasing function of the injection control duration of said injector as controlled by said engine control unit, said flow rate characteristic including a zone that is substantially linear, for injection control duration values greater than a minimum time, and defined by a gain corresponding to its slope, and by an offset at the origin where the extension of the linear zone towards the origin of injection control durations intersects the injection control duration axis, and a non-linear zone for small values of injection control durations, between the offset and said linear zone, the nominal theoretical linear and non-linear zones being initially stored in the engine control unit in the form of a theoretical offset and a theoretical gain for the linear zone, together with at least one table or mathematical relationship for the non-linear zone,the method comprising at least the steps consisting in:
- assuming that the gain is equal to the theoretical gain or to an updated gain based on the theoretical gain; and
for each injector whose characteristic is to be determined, replacing each of at least one reference injection having an injection control duration controlled by the engine control unit in compliance with the stored characteristic, with a multiple injection comprising a succession of at least two injections of injection control durations that are assumed to cause the same mass of fuel to be injected as by the replaced reference injection;
in determining the difference in fuel mass between the replaced reference injection and the multiple injection;
in deducing therefrom an error in the determination of said characteristic; and
in modifying the gain and/or the offset of the linear zone or at least of a table or mathematical relationship for the non-linear zone so as to compensate said error, and storing the new characteristic as determined in this way.
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Abstract
The method comprises the steps consisting in assuming that the gain of at least one injector is equal to a theoretical gain or an updated gain, and in replacing each of at least one reference injection of injection control duration controlled by the engine control unit in application of a stored characteristic, with a multiple injection comprising a succession of at least two injections of injection control durations that are assumed to cause the same mass of fuel to be injected as by the replaced reference injection, in determining the fuel mass difference between the reference injection and the multiple injection, in deducing therefrom an error in determining the characteristic, and in modifying the gain and/or the offset of the linear zone of the initial characteristic or at least a table or mathematical relationship for the non-linear zone of said characteristic, so as to compensate the error, and storing the new characteristic as determined in this way. Applications to real time determination as a function of the injection control duration of the flow rate characteristic of fuel injectors for internal combustion engines fed by injection.
32 Citations
10 Claims
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1. A method of determining the flow rate characteristic of at least one electrically-controlled fuel injector feeding an internal combustion engine and mounted in a fuel feed circuit of said engine, the determination being in real time and as a function of an injection control duration, and said circuit comprising at least one pump fed from a fuel tank and connected to a common rail for feeding fuel to the injectors of the engine, each injector being controlled by an engine control unit, including at least one calculator and at least one memory, such that on each cycle of the engine, each injector delivers a mass of fuel to the engine as determined by said injector flow rate characteristic, which expresses the mass injected as an increasing function of the injection control duration of said injector as controlled by said engine control unit, said flow rate characteristic including a zone that is substantially linear, for injection control duration values greater than a minimum time, and defined by a gain corresponding to its slope, and by an offset at the origin where the extension of the linear zone towards the origin of injection control durations intersects the injection control duration axis, and a non-linear zone for small values of injection control durations, between the offset and said linear zone, the nominal theoretical linear and non-linear zones being initially stored in the engine control unit in the form of a theoretical offset and a theoretical gain for the linear zone, together with at least one table or mathematical relationship for the non-linear zone,
the method comprising at least the steps consisting in: - assuming that the gain is equal to the theoretical gain or to an updated gain based on the theoretical gain; and
for each injector whose characteristic is to be determined, replacing each of at least one reference injection having an injection control duration controlled by the engine control unit in compliance with the stored characteristic, with a multiple injection comprising a succession of at least two injections of injection control durations that are assumed to cause the same mass of fuel to be injected as by the replaced reference injection;
in determining the difference in fuel mass between the replaced reference injection and the multiple injection;
in deducing therefrom an error in the determination of said characteristic; and
in modifying the gain and/or the offset of the linear zone or at least of a table or mathematical relationship for the non-linear zone so as to compensate said error, and storing the new characteristic as determined in this way. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- assuming that the gain is equal to the theoretical gain or to an updated gain based on the theoretical gain; and
Specification