Method for determining an air volume in a combustion chamber of an internal combustion engine

Abstract

A method for determining an air volume in a combustion chamber of a fuel-injection internal combustion engine, especially during a load change condition, including synchronizing a throttle valve setpoint signal to an operating state criterion (t.sub.n); determining a curve dynamics of the throttle valve position taking into account the synchronized throttle valve setpoint signal; determining an actual air volume quantity at an ACTUAL time point (t.sub.0); determining a desired time point (t.sub.0+t); predicting a further air volume quantity for the desired time point (t.sub.0+t) and determining a total air volume quantity from the ACTUAL air volume quantity and the further air volume quantity for the desired time point (t.sub.0+t).

Claims

1. A method for determining an air volume in a combustion chamber of a fuel-injection internal combustion engine during a load change condition, comprising: synchronizing a throttle valve setpoint signal to an operating state criterion (t.sub.n); determining a curve dynamics of the throttle valve position taking into account the synchronized throttle valve setpoint signal; determining an actual air volume quantity at an ACTUAL time point (t.sub.0); determining a desired time point (t.sub.0+t); predicting another air volume quantity for the desired time point (t.sub.0+t); determining a total air volume quantity from the ACTUAL air volume quantity and the further air volume quantity for the desired time point (t.sub.0+t).

2. The method as recited in claim 1, wherein the operating state criterion (t.sub.n) includes a crankshaft position and/or an intake valve position.

3. The method as recited in claim 1, further comprising determining the actual air volume quantity including measuring a manifold pressure (p.sub.SR) and/or an air mass flow (m.sub.SR).

4. The method as recited in claim 1, wherein predicting another air volume quantity includes: predicting a throttle valve position (.sub.1, .sub.2) at a first and a second prediction time point (t.sub.1; t.sub.2); predicting a first air volume quantity (p(t.sub.1)) at the first prediction time point (t.sub.1); predicting at least one second air volume quantity (p(t.sub.2)) at the second prediction time point (t.sub.2) on the basis of a tank model; and determining the further air volume quantity.

5. The method as recited in claim 4, wherein the tank model maps a combustion chamber and/or an injection chamber of the spark ignition engine at the desired time point (t.sub.0+t).

6. The method as recited in claim 1, wherein the further air volume quantity includes a predicted pressure difference and/or a predicted air-mass flow difference.

7. The method as recited in claim 1, wherein the further air volume quantity is predicted taking into account a characteristics map having fixed and/or variable data, a calculation algorithm, and/or operating state quantities of the spark ignition engine.

8. The method as recited in claim 1, wherein the desired time point (t.sub.0+t) and/or the prediction time point is determined taking into account a speed-dependent time difference (t).

9. The method as recited in claim 1, wherein the air volume is determined for a direct fuel injection combustion chamber.

10. A combustion engine having a control that is adapted for implementing a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of present invention will be described exemplarily and with reference to the attached drawing, in which:

(2) FIG. 1 shows an internal combustion engine 100 that is suited for implementing the method according to the present invention;

(3) FIG. 2 schematically represents an electronic engine-power control for the internal combustion engine shown in FIG. 1 for implementing the method according to the present invention;

(4) FIG. 3 is a diagram that schematically clarifies the synchronization step of the method according to the present invention;

(5) FIG. 4 is a diagram that schematically illustrates the modeling step of a curve dynamics of the throttle valve position;

(6) FIG. 5 is a schematic representation of the prediction of another air volume quantity;

(7) FIG. 6 is a schematic representation of the discrete determination of a first and second air volume quantity; and

(8) FIG. 7 is a schematic flow chart of the method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 schematically shows an internal combustion engine 100 having internal mixture formation (direct injection) and, alternatively, external mixture formation (manifold injection, dashed line representation). Shown is one of a plurality of cylinders 1 having piston 2 that define combustion chamber 3. Combustion chamber 3 is optionally sealed by an intake valve 4 or an exhaust valve 5 or communicates with intake manifold 6 or with exhaust pipe 7.

(10) Fuel injection motor 8, which is actuated by an actuating element 9 and injects fuel directly into the combustion chamber, leads into combustion chamber 3. For that purpose, actuating element 9 receives control signals from an engine management 10.

(11) Optionally, fuel injection motor 8, together with actuating element 9, may also lead into intake manifold 6 (dashed line representation). It is then a question of an engine 100 having external mixture formation and manifold injection.

(12) Configured in intake manifold 6 is throttle valve 11 which receives control signals 12 via engine management 10 and emits position signals 13. Throttle valve 11 thereby regulates air-mass flow S that is directed by intake manifold 6 into combustion chamber 3. The piston movement produced by the combustion is taken up by crankshaft 14, and a speed sensor 15 transmits engine speed n to engine management 10. A detector 16 in the form of a pressure sensor and/or mass-flow sensor senses intake manifold pressure p.sub.SR or an air-mass flow m.sub.SR and likewise supplies it as a signal indicative thereof to engine management unit 10.

(13) FIG. 2 clarifies the control of throttle valve 11. Engine management 10 includes a controller unit 17 having a monitoring module 18 and a processing unit 19. Unit 17 receives signals from sensors and transmits signals to actuators. Thus, for example, an accelerator pedal module 20 emits position signal 21 of an accelerator pedal position, and controller unit 17 processes the same, thereby transmitting a throttle valve actuating signal 23 to throttle valve 11 which, in turn, transmits a position signal 22 to unit 17. Thus, controller unit 17 of engine management 10 adjusts and monitors the throttle valve position.

(14) The method according to the present invention includes important sub-steps:

(15) FIG. 3 shows a synchronization step where the diagram illustrates the following signal characteristics over time t: a curve of accelerator pedal position 24, which characterizes a driver command, and a throttle valve setpoint signal 25 (original), which follows from the curve of the accelerator pedal positionin each case, plotted as angle . Illustrated on time axis in each case are time points t.sub.n, which characterize the beginning of an intake stroke, respectively. In the method, original throttle valve setpoint signal 25 is advanced in time (direction of arrow), so that it is immediately before a time point t.sub.n of an intake cycle. This synchronized or timed throttle valve setpoint signal 26 is used for the remainder of the method.

(16) For this, FIG. 4 shows a modeling of the actual throttle valve position curve (throttle dynamics) that is to be derived from synchronized throttle valve setpoint curve 26. Due to inertias in the system, the actual throttle valve curve is indicated in the diagram by curve 27 that deviates from throttle valve setpoint curve 26. In a calculation method or with the aid of characteristic data, a throttle valve curve 28 is then modeled (dashed line representation), which is used for further calculations. With the aid of modeled throttle valve curve 28, throttle valve positions (opening angles .sub.1 and .sub.2) may be determined at specific time points t.sub.1 and t.sub.2 (different opening angles of the throttle valve and thus different pressure curves across the throttle valve).

(17) FIG. 5 shows the method sequence where, in a first step, with the aid of a throttle valve model, throttle valve position at is determined. It then leads in a pressure tank model 32 to a prediction pressure p(t.sub.1). This is likewise determined in a next step at a time point t.sub.2 for a second throttle valve position .sub.2. p(t.sub.2) results here. It likewise corresponds to a predicted pressure value.

(18) FIG. 6 shows the determination of a total air volume quantity 33 that results from predicted pressure variables p(t.sub.1) and p(t.sub.2), as well as from an actual air volume quantity 34 (here, ACTUAL pressure p.sub.ACTUAL) that is determined with the aid of detector 16. Pressure variables p(t.sub.1), p(t.sub.2) and p.sub.ACTUAL are thereby summed.

(19) FIG. 7 shows an exemplary embodiment of the entire inventive method sequence including the steps: S1 synchronizing a throttle valve setpoint signal 25, 26 to an operating state criterion t.sub.n (for example, intake stroke of the next cylinder/crankshaft position); S2 determining/modeling a curve dynamics 28 of the throttle valve position taking into account the synchronized throttle valve setpoint signal 26; S3 determining an actual air volume quantity (p.sub.sr) 34 at an ACTUAL time point t.sub.0; S4 determining a desired time point t.sub.0+t; S5 predicting another air volume quantity (p, m) for the desired time point (t.sub.0+t); S6 determining a total air volume quantity 33 from the ACTUAL air volume quantity 34 and the further air volume quantity for the desired time point (t.sub.0+t).

(20) Step S5 may thereby include other optional steps (entered in parentheses in the figure): S51 predicting a throttle valve position .sub.1; .sub.2 at a first and a second prediction time point t.sub.1; t.sub.2; S52 predicting a first air volume quantity p(t.sub.1) at first prediction time point t.sub.1; S53 predicting at least one second air volume quantity p(t.sub.1) at second prediction time point t.sub.2; S54 determining the further air volume quantity on the basis of a tank model 32.

(21) Other variations and exemplary embodiments of the present invention will become apparent to one skilled in the art from the claims.

LIST OF REFERENCE NUMERALS

(22) 100 combustion engine 1 cylinder 2 piston 3 combustion chamber 4 intake valve 5 exhaust valve 6 intake manifold 7 exhaust pipe 8 fuel injection motor 9 actuating element 10 engine management/engine management unit 11 throttle valve 12 control signal 13 actuating signals 14 crankshaft 15 speed sensor 16 detector 17 controller unit 18 monitoring module 19 processing unit 20 accelerator pedal module 21 position signal 22 throttle valve position signal 23 throttle valve actuating signal 24 curve of the accelerator pedal position 25 original throttle valve setpoint signal 26 synchronized throttle valve setpoint signal 27 real throttle valve curve 28 modeled throttle valve position curve 31 throttle valve model 32 pressure tank model 33 total air volume quantity 34 actual air volume quantity (P.sub.SR; m.sub.SR) 35 further air volume quantity t.sub.0 actual time point T.sub.0+t desired time point t.sub.n operating state criterion t.sub.1; t.sub.2 prediction time point .sub.1; .sub.2 throttle valve position