Method for adapting transition compensation

Abstract

A method for adapting a transition compensation based on a lambda value change for operating an engine, which includes a combustion chamber having a first inlet opening connected to a first intake pipe having a first injector. The chamber includes a second inlet opening connected to a second intake pipe having a second injector. During normal operation, a predetermined fuel quantity is injected, and this quantity includes a first and second fuel quantities to be injected respectively via the first and second openings. In a first step, the first injector remains closed, and in a second step, the first injector is opened again. In the second step, a first test fuel quantity is injected into the combustion chamber via the first opening and a second test fuel quantity is injected via the second opening, the first and second test fuel quantities making up the predetermined fuel quantity.

Claims

1. A method for adapting a transition compensation for operation of an internal combustion engine, which includes a combustion chamber having a first inlet opening connected to a first intake pipe, in which a first injector is situated, the combustion chamber having a second inlet opening connected to a second intake pipe, in which a second injector is situated, the method comprising: injecting a predetermined fuel quantity during normal operation of the internal combustion engine, the predetermined fuel quantity being made up of a first fuel quantity to be injected by the first injector and a second fuel quantity to be injected by the second injector; in a first test step carried out over a first internal combustion cycle, maintaining the first injector closed while injecting the predetermined fuel quantity by the second injector; in a second test step carried out over a second internal combustion cycle, injecting a first test fuel quantity by the first injector and injecting a second test fuel quantity by the second injector, wherein the first test fuel quantity and the second test fuel quantity together make up the predetermined fuel quantity; determining a lambda value change during at least one of: the first test step, or the second test step; and adapting a transition compensation using an operating condition during the normal operation of the internal combustion engine as a function of the determined lambda value change, the adapted transition compensation correcting the predetermined fuel quantity to account for deposition of fuel on walls of the first and second intake pipes.

2. The method of claim 1, wherein during the normal operation of the internal combustion engine, the first fuel quantity injected by the first injector and the second fuel quantity injected by the second injector are equal and/or during the second test step, the first test fuel quantity injected by the first injector and the second test fuel quantity injected by the second injector are equal.

3. The method of claim 1, wherein the lambda value change is determined at a start and/or during a course of the first and/or second test steps.

4. The method of claim 1, wherein the transition compensation is adapted as a function of the determined lambda value change for a plurality of different operating conditions of the internal combustion engine.

5. The method of claim 4, wherein the adapted transition compensation for the plurality of different operating conditions of the internal combustion engine is stored and then taken into account during the normal operation of the internal combustion engine.

6. The method of claim 1, wherein the transition compensation is adapted again for at least one operating condition of the internal combustion engine when a change in emission properties of the internal combustion engine exceeds a predetermined value.

7. The method of claim 1, wherein the transition compensation is adapted again after a predetermined time interval for a plurality of different operating conditions of the internal combustion engine.

8. The method of claim 1, wherein the injected predetermined fuel quantity is controlled by a computer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an illustration of a part of an internal combustion engine.

(2) FIG. 2a shows a schematic representation of a part of the internal combustion engine, which carries out a first method step of a method according to an exemplary specific embodiment of the present invention.

(3) FIG. 2b and FIG. 2c show the change over time of a deposited fuel quantity.

(4) FIG. 2d shows the change over time of a lambda value.

(5) FIG. 3a shows a schematic representation of a part of the internal combustion engine, which carries out a second method step of a method according to a specific exemplary embodiment of the present invention.

(6) FIG. 3b and FIG. 3c show the change over time of a deposited fuel quantity.

(7) FIG. 3d shows the change over time of a lambda value.

DETAILED DESCRIPTION

(8) FIG. 1 shows an illustration of a part of an internal combustion engine 1, including a combustion chamber 2, an injector 12, an inlet valve 10, an ignition arrangement 13, an injector orifice 14, an inlet opening 10 and a first intake pipe 11, while fuel 3 is injected into first intake pipe 11 in the direction of the combustion chamber, a second intake pipe also being provided (not shown in FIG. 1). During injection in the form of spray cones, the fuel is atomized, which is represented with the aid of a broken line in FIG. 1. This representation shows that in a realistic specific embodiment of an internal combustion engine 1, fuel 3 is also sprayed against the intake pipe wall 11 during injection.

(9) FIG. 2a and FIG. 2b show a schematic representation of a part of internal combustion engine 1, which carries out a first method step of a method according to an exemplary specific embodiment of the present invention. The internal combustion engine includes combustion chamber 2, a first and second intake pipe 11 and 21 and at least one injector per intake pipe, i.e., at least two injectors 12, 22. Combustion chamber 2 is configured in such a way that a piston (not shown in the figure) is able to move therein, and the wall of the combustion chamber has two intake ports 10, 20, through which an air-fuel mixture is drawn in, and two exhaust ports 30, 31, from which the raw exhaust gases are expelled out of combustion chamber 2 into exhaust pipes 32, 33 after the combustion process of the air-fuel mixture. A lambda sensor, which is capable of ascertaining the residual oxygen content of the exhaust gas, is usually situated at the outlet of combustion chamber 2. During normal operation, a predetermined fuel quantity is injected in the direction of corresponding inlet openings 10, 20 into intake pipes 11, 21 from the two injectors 12, 22, thereby forming a fuel-air mixture together with the aspirated air in the corresponding intake pipe. The quantity of the aspirated air is varied by a throttle valve. For example, if internal combustion engine 1 is to make available an elevated torque, the throttle valve opens. In this case, the pressure in intake pipe 11, 21 increases, the evaporation tendency of the fuel declines and a portion of the fuel is deposited on the wall. Together with fuel sprayed against the wall during injection, the fuel deposited on the wall is missing from the fuel-air mixture when it is supplied to combustion chamber 2. When the throttle valve closes, the intake pipe pressure drops, the evaporation tendency of the fuel increases, the fuel deposited on the intake pipe wall evaporates into the volume of the intake pipe and is finally additionally supplied to combustion chamber 2. Therefore, the fuel quantity provided must be expected not to reach the combustion chamber during both opening and closing. The fuel quantity supplied to the combustion chamber differs from the setpoint fuel quantity. To also take into account fuel changes resulting from, for example, the deposition of fuel on intake pipe wall 11, 21, in predetermination of the fuel to be injected, it is necessary to know the difference between the setpoint fuel quantity and the actual fuel quantity.

(10) FIG. 2 shows a first method step, in which a first injector 12 is closed over at least one entire cycle, so that no fuel is injected into first intake pipe 11, and the wall film regresses on its wall. At the same time, second injector 22 injects a substitute fuel quantity 4 into second intake pipe 21, the quantity of which corresponds precisely to the fuel quantity which would be injected by the two fuel injectors together during normal operation (illustrated by 2x printed in bold in the figure). FIG. 2b shows that during the first method step, the deposition of fuel on the first intake pipe wall 310 decreases over time 300. However, the deposition of fuel on second intake pipe wall 320 remains constant over time 300, as represented in FIG. 2c.

(11) With the aid of the lambda sensor, it is determined that measured lambda value 330 initially decreases over time 300 during the regress of the wall film and subsequently returns back to the lambda value which the lambda sensor has measured before the closing of the injector. The brief decrease and the subsequent increase of the lambda value, i.e., this lambda value change, is referred to as a fat excursion and is illustrated in FIG. 2d.

(12) In FIG. 3, the second method step of the method according to one exemplary specific embodiment of the present invention is illustrated schematically.

(13) In the second method step, first injector 12 is opened again and a first test fuel quantity 6 is injected into first intake pipe 11. First test fuel quantity 6 together with a second test fuel quantity 6, which is injected by second injector 22 into second intake pipe 21, forms a fuel quantity which corresponds to the predetermined fuel quantity from normal operation and the substitute fuel quantity. During the second method step, fuel is again deposited on the first intake pipe wall 11, i.e., the deposition of fuel on the first intake pipe wall 310 increases over time 300. This is illustrated in FIG. 3b. FIG. 3c shows that the deposition of fuel on the second intake pipe wall 320 remains constant. It is likewise found that, during the second method step, lambda value 330 initially increases over time 300 and subsequently returns to the lambda value of the lambda sensor before the injector is opened. This brief increase and the subsequent decrease of the lambda value are referred to as a lean excursion and are depicted in FIG. 3d.

(14) Repeating the first and second method steps under different operating situations makes it possible to determine the difference between the actual fuel quantity and the setpoint fuel quantity of the fuel supplied to the combustion chamber for the particular operating situation.

(15) Knowledge of the deviation from the fuel quantity provided for combustion chamber 2 then makes it possible to correct the predetermined fuel quantity for each operating situation of internal combustion engine 1, i.e., to adapt the transition compensation for the particular operating situation.