Internal combustion engine having a regulating device

Abstract

An internal combustion engine (1) having a regulating device (C) wherein an air-fuel mixture with a combustion air ratio () which is adjustable by the regulating device is burnt in the internal combustion engine, wherein the regulating device (C) has a power output regulating circuit adapted to adapt an actual output (P.sub.g) of the internal combustion engine (1) to a reference power output (P.sup.d.sub.g) of the internal combustion engine (1) by way of an adjustment of the combustion air ratio (), and a NOx emission regulating circuit adapted by way of a functional relationship (2) to actuate actuators influencing a charge pressure as an alternative parameter for the NOx emission by the charge pressure such that a charge pressure reference value (p.sup.d.sub.im) can be set for each reference power output (P.sup.d.sub.g) of the internal combustion engine.

Claims

1. An internal combustion engine having a regulating device, wherein an air-fuel mixture having a combustion air ratio adjustable by the regulating device, is burnt in the internal combustion engine, the regulating device comprising: a power output regulating circuit configured to change an actual power output of the internal combustion engine to a reference power output of the internal combustion engine by an adjustment of the combustion air ratio; and a NOx emission regulating circuit configured to use a functional relationship to actuate actuators influencing a charge pressure for NOx emission regulation, based on a charge pressure reference value set for each reference power output of the internal combustion engine; wherein the charge pressure reference value is set using reference power output, instead of actual power output of the internal combustion engine, and there is no coupling of NOx emission regulation and power output regulation.

2. The internal combustion engine as set forth in claim 1, wherein the NOx emission regulating circuit comprises a charge pressure regulator operable to change the charge pressure to a charge pressure reference value, wherein the charge pressure regulator is a comparator and a PID regulator combination, or a model-based regulator.

3. The internal combustion engine as set forth in claim 1, wherein the power output regulating circuit comprises a regulator operable to actuate the actuators which influence a combustion gas mass flow, wherein the regulator is a comparator and a PID regulator combination, or a model-based regulator.

4. The internal combustion engine as set forth in claim 1, wherein the power output regulating circuit comprises a skip fire regulating module to which the reference power output can be fed as an input and which is configured to actuate a regulator for a combustion gas mass flow such that no combustion occurs in selected cylinders of the internal combustion engine in a state in which combustion gas is absent.

5. The internal combustion engine as set forth in claim 1, wherein a regulator within the power output regulating circuit is configured such that further actual parameters can be fed to the regulator as an input thereof, wherein the regulator limits a control parameter reference combustion air ratio with regard to the further actual parameters such that when limit values of the further actual parameters are reached, no further change in the control parameter reference combustion air ratio occurs in a direction which further adversely influences the further actual parameters.

6. The internal combustion engine as set forth in claim 1, further comprising a trajectory generator configured to convert a non-steady abrupt presetting of the reference power output by a user into a steady trajectory for the reference power output, wherein the trajectory generator is upstream of the power output regulating circuit and the NOx emission regulating circuit.

7. The internal combustion engine as set forth in claim 6, wherein the trajectory generator is further configured to receive the actual output of the internal combustion engine as an input and to monitor a deviation between an instantaneous value of the reference power output in accordance with a steady function and the actual output of the internal combustion engine such that, in an event of an excessively large deviation, the steady trajectory of the reference power output is limited to a given value above the actual output of the internal combustion engine.

8. The internal combustion engine as set forth in claim 1, further comprising a dead time compensation device to which a predeterminable dead time can be fed and which is configured to acquire the reference power output, the actual output of the internal combustion engine, and an actual charge pressure at a time and output same as an output in a form predicted into a future.

9. The internal combustion engine as set forth in claim 8, further comprising a regulator which is configured to acquire an output of the dead time compensation device as an input and to output a reference combustion air ratio in dependence on the input.

10. The internal combustion engine as set forth in claim 3, wherein the actuators comprise port injection valves.

11. The internal combustion engine as set forth in claim 3, wherein the actuators comprise a gas metering device of a gas mixer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and details of the invention will now be discussed for various embodiments by way of example with reference to the drawings, in which:

(2) FIG. 1 is a schematic diagram showing a state of the art regulating device; and

(3) FIGS. 2-7 are schematic diagrams showing a regulating device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 2 shows a first embodiment of the invention, wherein the same references denote the same components or logical procedures as in FIG. 1.

(5) In comparison with FIG. 1, it is possible to see as a first difference that the NOx emission regulating circuit, instead of the actual power output P.sub.g of the internal combustion engine 1, involves the reference power output P.sup.d.sub.g of the internal combustion engine 1 as the input of the functional relationship 2. In the present case therefore that gives the relationship between charge pressure reference value p.sup.d.sub.im (output of the functional relationship 2) and reference power output P.sup.d.sub.g (input of the functional relationship 2) for a given NOx value in the form of a curve.

(6) In the NOx emission regulating circuit the charge pressure reference value p.sup.d.sub.im is passed to a charge pressure regulator 8 as the input. That charge pressure regulator 8 could certainly be in the form of a comparator 3 and a PID regulator 4 as shown in FIG. 1. A configuration in the form of a model-based regulator however is preferred, which in addition to the currently prevailing actual charge pressure p.sub.im also needs the charge pressure reference value p.sup.d.sub.im as the input. Unlike FIG. 1 the output of the charge pressure regulator 8 is implemented in the form of control signals u.sub.p to those actuators (for example compressor bypass valve or throttle flap valve) which influence the actual charge pressure p.sub.im. Those control signals u.sub.p were in FIG. 1 the output of the PID regulator 6 and thus the power output regulating circuit. Because those control signals u.sub.p in FIG. 2 are part of the NOx emission regulating circuit the strong coupling in FIG. 1 between the NOx emission regulating circuit and the power output regulating circuit does not occur with the invention.

(7) The power output regulating circuit in FIG. 2 differs from that in FIG. 1 only in that the regulator 5 which actuates the actuators (for example port injection valves or gas metering device of a gas mixer) which influence the combustion gas mass flow u.sub.gas is arranged in the power output regulating circuit. Instead of the arrangement of comparator 7 and PID regulator 6 it would also be possible to provide a model-based regulator.

(8) In the simplest case the functional relationship 2 occurs in the above-described form as a simple curve. As is already known from the specifications founded on EP 0 259 382 B1 the functional relationship 2 can be corrected by incorporation of corrections in respect of the ignition timing, inlet temperature and so forth.

(9) To sum up various advantages are linked to the invention: faster adaptive control in respect of load changes is possible (faster adaptation of the actual power output P.sub.g of the internal combustion engine 1 to a change in the reference output P.sup.d.sub.g), the target emission values for NOx can be attained substantially earlier upon load changes, and the emission values for NOx already remain closer to the desired value during a load change because the functional relationship 2 can be more easily followed.

(10) FIG. 3 shows a second embodiment of the invention. In comparison with FIG. 2, the power output regulating circuit additionally has a skip fire regulating module 9 to which the reference power output P.sup.d.sub.g is passed as input. The output of the skip fire regulating module 9 goes to the regulator 5 controlling the combustion gas mass flow u.sub.gas in such a way that in selected cylinders of the internal combustion engine 1 no combustion takes place in the absence of combustion gas. That permits rapid adaptation to load changes. That is advantageous for port injection internal combustion engines.

(11) FIG. 4 shows a third embodiment of the invention. In comparison with FIG. 2 this additionally involves the feedback of further actual parameters y (here exhaust gas temperature at the discharge side of the internal combustion engine 1 or the intake side of a possibly provided exhaust gas post-treatment unit (not shown) and/or knock or misfire signals of cylinders of the internal combustion engine 1 and/or oil temperature and/or water coolant temperature and/or charge air temperature upstream of the cylinders as an input of the PID regulator 6 within the power output regulating circuit. They limit the control parameter .sub.d such that when limit values of the actual parameters are reached there is no further change of .sub.d in a direction which further adversely influences the actual parameters. Adverse influence would be for example further enrichment (lower lambda value) at an already high exhaust gas temperature at the discharge side of the internal combustion engine 1 or a leaning effect (higher lambda value) when there are misfiring signals of cylinders of the internal combustion engine 1. The feedback of further actual parameters y therefore represents a safety loop, by which influencing of the control parameter .sub.d occurs only in limits which are tolerable for the internal combustion engine 1.

(12) FIG. 5 shows a fourth embodiment of the invention, wherein a trajectory generator 10 is disposed upstream of the functional relationship 2 in comparison with FIG. 2. It converts a non-steady abrupt presetting of the reference power output P.sup.d,step.sub.g by a user into a steady trajectory for the reference power output P.sup.d.sub.g. Starting from a present currently prevailing value of the reference power output P.sup.d.sub.g and a desired end value in respect of the reference power output P.sup.d.sub.g a steady function linking those values is selected, for example in the form of a (preferably linear) ramp or in the form of a polynomial or the like. In addition the actual power output P.sub.g can be fed as an input to the trajectory generator 10. In that way it is possible to monitor the deviation between the instantaneous value of the reference power output P.sup.d.sub.g in accordance with the steady function and the actual power output P.sub.g such that, in the event of an excessive deviation, the steady function of the reference power output P.sup.d.sub.g is limited to a given value above the actual power output P.sub.g. That case can be relevant for example with a cold internal combustion engine 1.

(13) FIG. 6 shows a fifth embodiment of the invention in which there is provided a dead time compensation device 11 in comparison with FIG. 2. That is advantageous in particular for mixture-charge internal combustion engines 1. The input to the dead time compensation device 11 are the reference power output P.sup.d.sub.g, the actual power output P.sub.g and the actual charge pressure p.sub.im. The input signals P.sup.d.sub.g(t), P.sub.g(t), p.sub.im(t) at a time t are output again as the output in a form P.sup.d.sub.g(t+D), P.sub.g(t+D), p.sub.im(t+D) predicted into the future t+D by a dead time D (time which lies between a change in the combustion gas mass flow and the corresponding reaction of the internal combustion engine 1 in the actual power output P.sub.g). That output serves as an input for a regulator 12 which outputs a reference value for the lambda value in dependence on the input. Prediction is effected in per se known manner in model-based fashion by integration of those differential equations which describe the dynamic behaviour of those parameters. Those differential equations are well known to the man skilled in the art.

(14) FIG. 7 shows an embodiment of the invention in which all measures of the above-discussed embodiments are jointly provided. Naturally it would also be possible here to omit individual measures. The structural units and logical relationships required for open-loop control/closed-loop control are combined together for all embodiments in the regulating device C. The term regulator in the context of the present invention does not necessarily mean a physical unit but a given function which can be implemented for example by a circuit, memory and so forth.

LIST OF REFERENCES USED

(15) 1 internal combustion engine 2 functional relationship 3 first comparator 4 first PID regulator 5 first regulator 6 second PID regulator 7 second comparator 8 charge pressure regulator 9 skip fire regulating module 10 trajectory generator 11 dead time compensation device 12 further regulator .sub.d reference lambda value (reference value for combustion air ratio) lambda value (combustion air ratio) P.sup.d.sub.g reference power output P.sub.g actual power output p.sup.d,step.sub.g abrupt presetting of the reference output p.sub.im actual charge pressure p.sup.d.sub.im charge pressure reference value t time C regulating device D dead time u.sub.gas combustion gas mass flow u.sub.p open-loop control signals influencing the actual charge pressure y actual parameters of the internal combustion engine 1 and/or downstream-connected units