INTERNAL COMBUSTION ENGINE WITH A REGULATING DEVICE

Abstract

An internal combustion engine with a regulating device, whereby a fuel-air mixture is burned in the internal combustion engine with a combustion air ratio controllable by the regulating device, whereby the regulating device comprises an emission control loop, which is designed to control the charge-air pressure as a substitute variable for the NOx emission by the actuators influencing the charge-air pressure via a functional relationship, such that, for each target power or actual power of the internal combustion engine, a charge-air pressure target value can be set, and whereby the internal combustion engine further comprises a variable valve train, by means of which an operating characteristic of at least one inlet valve can be varied, whereby the functional relationship takes into account the influence of an adjustment of the operating characteristic of the at least one inlet valve.

Claims

1. An internal combustion engine with a regulating device, whereby a fuel-air mixture is burned in the internal combustion engine with a combustion air ratio controllable by the regulating device, whereby the regulating device comprises an emission control loop, which is designed to control the charge-air pressure as a substitute variable for the NOx emission by the actuators influencing the charge-air pressure via a functional relationship, such that, for each target power or actual power of the internal combustion engine, a charge-air pressure target value can be set, and whereby the internal combustion engine further comprises a variable valve train, by means of which an operating characteristic of at least one inlet valve can be varied, characterized in that the functional relationship takes into account the influence of an adjustment of the operating characteristic of the at least one inlet valve.

2. An internal combustion engine according to claim 1, whereby, with a change in the operating characteristic of the at least one inlet valve in a direction that causes a decreased degree of filling of the internal combustion engine, the functional relationship influences the intervention on the emission control loop such that an enrichment of the fuel-air mixture supplied to the internal combustion engine is corrected to the level that is correct for the power to be provided.

3. An internal combustion engine according to claim 1, whereby, in a change of the operating characteristic of the at least one inlet valve in a direction which causes a decreased degree of filling of the internal combustion engine, the functional relationship is considered such that the emission control loop adjusts a fuel-air mixture that is richer compared to the previous operating point.

4. An internal combustion engine according to claim 1, whereby, in a change of the operating characteristic of the at least one inlet valve in a direction which causes a decreased degree of filling of the internal combustion engine, the functional relationship is considered such that a charge-air pressure of the internal combustion engine is increased.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention is explained in more detail below with reference to the figures. The drawings in detail:

[0036] FIG. 1 a diagram of charge-air pressure versus power for various Miller control times and

[0037] FIG. 2 a schematic representation of an internal combustion engine.

DETAILED DESCRIPTION

[0038] FIG. 1 shows a diagram of the charge-air pressure of an internal combustion engine over the mechanical or electrical power delivered by the internal combustion engine. The relationship is plotted for three different control times (the curves Miller 1, Miller 2 and Miller 3) for specific NOx emissions which are the same for all three curves.

[0039] Here, the inlet valve closure is the earliest in Miller 1, latest in Miller 3, and intermediate in Miller 2. The control time of the course marked Miller 1 correspondsin the words of the previous descriptionto a sharper valve closing time. Via the earlier inlet valve closure in Miller 1 compared to the two other control times, in order to achieve constant NOx emissions to obtain the same mechanical or electrical power (e.g. 75%) in Miller 1, a higher charge-air pressure is required than e.g. in Miller 2 or Miller 3.

[0040] During the operation of an internal combustion engine 1 equipped with a variable valve train 3, the control times of the inlet valves 4 are changed many times. This allows a reaction to changing load requirements as well as to changing environmental conditions. As an example, we can mention the starting process, during which the closing times of the inlet valves 4 are usually made less sharp compared to the closing times for full-load operation. Another changing condition is the external temperature. Wear and deposits on the gas exchange unit also require adjustments to the control times.

[0041] If the regulation of the internal combustion engine now moves from a constant relationship stored for an operating characteristic of the inlet valves 4 between charge-air pressure and power according to the prior art, then errors occur in the target charge-air pressure determined from the relationship, as soon as the operating characteristic has changed compared to the initial value.

[0042] With an embodiment of the present invention, the influence of an adjustment of the operating characteristic of the at least one inlet valve 4 is taken into account in the regulating device C of the internal combustion engine 1.

[0043] FIG. 2 shows schematically an internal combustion engine 1 which is equipped with a variable valve train 3. With the variable valve train 3, the opening characteristic of the at least one inlet valve 4 and thereby the quantity (volume) of the charge air or propellant gas-air mixture flowing into a combustion chamber 7 of the internal combustion engine 1 can be varied in individual cycles and optionally in individual cylinders. In this example, four combustion chambers 7 are shown. There can be significantly more or fewer.

[0044] The regulating device C includes a power control loop 5 designed to match an actual power of the internal combustion engine 1 with a target power of the internal combustion engine 1, and an emission control loop 6 designed to control, via a functional relationship 2, the charge-air pressure as a substitute variable for the NOx emission by the actuators influencing the charge-air pressure, such that, for each target power P.sup.d.sub.g or actual power P.sub.g of the internal combustion engine 1, a charge-air pressure target value p.sup.d.sub.im can be set. The functional relationship 2 can e.g. be stored in the form of a family of curves, a characteristic map, a table or in the form of an analytical relationship.