FR2550822A1 - METHOD FOR CONTROLLING THE QUANTITY OF FUEL IN INTERNAL COMBUSTION ENGINES - Google Patents

Abstract

A.PROCEDE FOR ADJUSTING THE AMOUNT OF FUEL IN INTERNAL COMBUSTION ENGINES. B. PROCEDURE CHARACTERIZED IN USING THE DEGREE OF SENSE OF THE ACCELERATOR, THE LOAD OF THE MOTOR AND THE NUMBER OF ROTATES OF THE MOTOR TO MAKE AN ESTIMATION OF THE NECESSARY AIR VOLUME QA, THEN, AS A FUNCTION OF THIS EVALUATION, THE VOLUME FLOW OF AIR QA IS CONTROLLED. C. THE INVENTION CONCERNS THE POWER SUPPLY OF INTERNAL COMBUSTION ENGINES.

Description

Method for controlling the amount of fuel in engines

  The present invention relates to a method for controlling the amount of fuel in

internal combustion.

  In general, it is known that in an internal combustion engine, even if the throttle valve is opened or closed completely instantaneously, the volume flow rate of air sucked into the cylinder varies according to a function

  first order delay having a time constant.

  To explain the detail of this point, reference will be made by way of example to FIG. 1; according to this figure, the volume flow rate of air in the suction pipe, controlled by the butterfly 1 is represented by QAV; the volume flow rate of air in the manifold 2 is represented by QAM, the volume flow rate of air sucked into a cylinder 3 is represented by QAE; the volume of the collector 2 is represented by Vm; the absolute pressure in the manifold 2 is represented by Pm; the volume of the cylinder 3 is represented by Vc, the number of engine revolutions is represented by N and in the case of a four-cylinder engine 20 we have: QAE = p Vc x N x 2 p = Pm po = Pm x 1,193 = K Pm Po 760 (760 mm Hg at 230 ° C) QAE K Pm Vc N QAE = K Pm (1) Thus, Q Am = p Vm = K Pm Vm At d Pm Q Am = K Vm dt (2) ) Thus, Q Am = Q Av QAE (3) According to the relations 1, 2, 3 one obtains: Kmd Prn Vc N d K Vm dt = QAV K Pm VN 30 (4) Vm 3 O d Pm (5) Thus, This means that even in the case of an air volume flow rate Q Av which varies instantaneously in the intake manifold, the absolute pressure Pm in the manifold varies according to a delay function. This is why Vc N the air volume flow rate QA (= QAE) sucked into the cylinder 15 dre 3 varies according to a first order delay function, inversely proportional to the pressure.

  absolute Pm prevailing in the collector.

  For this reason, by way of example, according to a known method of adjusting the amount of fuel, as represented by the curve in point I: in FIG. 2, the quantity of fuel injected per injector varies directly as a function of the variation of the travel of the accelerator pedal; this presents a difficulty at the time of acceleration or deceleration, because the air / fuel ratio of the gas mixture and the torque supplied by the engine varies very rapidly, which results in an uncomfortable shock

for the driver.

  There is also known another process represented by a dashed line curve in FIG. 2, the amount of fuel injected by the injector varies inversely proportional to the absolute pressure Pm prevailing in the collector 2; in this case, the difficulty is that in particular, when the engine is running at a low rotational speed, there is a delay in the response to the accelerator pedal, so that the acceleration and

deceleration will be weak.

  The object of the present invention is to overcome known drawbacks and solutions and to create a method for controlling the amount of fuel injected into an internal combustion engine so as to avoid uncomfortable shocks when accelerating or accelerating. a deceleration, everything

  by improving the acceleration and deceleration characteristics of the engine.

  For this purpose, the invention relates to a method characterized in that the necessary air volume flow rate and the time constant of the first-order delay are determined until the fuel injected is effectively sucked into the cylinder, using the degree of depression of the accelerator pedal, the number of revolutions of the engine and the load applied to the engine, then when the accelerator pedal is depressed, the quantity of fuel is determined taking into account the constant Of time of the first-order fuel delay and the first-order delay of the volume flow of air actually sucked into the cylinder, to obtain a ratio

air / correct fuel.

  The present invention will be described in more detail with the aid of the accompanying drawings, in which Fig. 1 is a diagram showing the different volumes of intake air to the cylinder; Fig. 2 is a graph showing the characteristic changes in the amount of fuel injected, in conventional fuel control systems; FIG. 3 shows a control diagram for implementing the fuel control method according to the invention; FIG. 4 is a graph showing the variation of the quantity of fuel injected, according to

the process of the invention.

  Description of the preferred embodiment

  The present invention will be explained hereinafter with the aid of the accompanying drawings and in particular the embodiment shown in FIGS. 3 and 4. FIG. 3 shows the control diagram according to the method of the invention. When the driver depresses the accelerator pedal For example, from the point of intersection (Q Ai; QF 1) O 10 to point B (QA 2, QF 2) (FIG. 2), the degree of depression of the number of engine revolutions at point A and amplitude of the load applied to the motor will be detected by different sensors; the required volume flow of air, ie the air volume flow QA 2 at point B and the time constant of the first order delay until the fuel injected actually arrives in cylinder 3 will be estimated, then the amount of fuel (amount of fuel injected by the injector) will vary from QF 1 to QF 2 taking into account the estimated time constant of the first-order fuel delay, for a volume flow of air having the first-order delay mentioned above This results in the following formula: ## EQU1 ## In this formula, N represents the number of injections This is why the variation of the quantity of fuel QF results in the dashed curve in FIG. 4 If the value of the constant N varies, the curve of variation of the quantity of fuel QF also varies and c This is why the air / fuel ratio can be adjusted freely. In view of the variation in the quantity of feed fuel QF, any disturbing shock at the time of acceleration or deceleration is avoided and the characteristics of acceleration and deceleration are improved.

Claims (1)

CLAIM:   A method for controlling the amount of fuel fed to an internal combustion engine, characterized in that an air volume flow rate (QA) and a time constant of the first-order delay are determined until the fuel is actually sucked into the cylinder (3) of the engine, starting from the degree of depression of the accelerator pedal, the number of revolutions of the engine and the load applied to the engine, 10 and when the accelerator pedal is depressed , the amount of feed fuel (QF) is determined by taking into account the time constant of the first-order fuel delay, with respect to the delay of   first order of the air volume flow rate which must actually be sucked into the cylinder.