DE102020206799A1 - Method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic diagram of an internal combustion engine on a test bench and a control device for controlling a test bench for an internal combustion engine - Google Patents

Abstract

The invention relates to a method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic diagram of an internal combustion engine (3) on a test bench (1), a first operating point being selected in the characteristic diagram, the internal combustion engine (3) in the first operating point is operated, whereby a) a combustion chamber peak pressure setpoint value for a combustion chamber peak pressure is gradually reduced until a first operating parameter of the internal combustion engine (3) lies beyond a first predetermined limit value, with a respective setting value for the combustion chamber peak pressure setpoint value and a respective one for each change step resulting consumption value and / or emission value are stored, whereby) the operation of the internal combustion engine (3) is continued with the combustion chamber peak pressure setpoint last reached, at which the first operating parameter was not yet beyond the first predetermined limit value, wherebyic) combustion The center of gravity setpoint for a combustion center of gravity is shifted early in steps until a second operating parameter of the internal combustion engine (3) is beyond a second predetermined limit value, with a respective setting value for the combustion focus setpoint value and a resulting consumption value and / or emission value for each change step are stored, whereby) the operation of the internal combustion engine (3) is continued with the last reached combustion focus setpoint, in which the second operating parameter was not yet beyond the second predetermined limit value, wherebyie) the combustion focus setpoint is gradually shifted to a late stage until a The third operating parameter of the internal combustion engine (3) is beyond a third predetermined limit value, with a respective setting value for the combustion focus setpoint value and a respective resulting consumption value and / or Emi for each change step ssion value can be saved.

Description

The invention relates to a method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic diagram of an internal combustion engine on a test bench and a control device for controlling a test bench for an internal combustion engine.

Control units for internal combustion engines typically include speed control; other system and / or manipulated variables are set using maps. If the structural concept of an internal combustion engine changes, for example with a view to various sensors that are additionally provided or omitted, or if a control unit is to be set up to operate a completely newly developed internal combustion engine, this results in considerable time-consuming and cost-intensive data processing for the maps. The data is often set manually on the test bench by a test bench driver. The aim of the data on the maps is to be able to implement specifications regarding the pollutant emissions to be complied with and / or a maximum fuel consumption to be complied with, especially for the later operation of the internal combustion engine, the internal combustion engine then being operated by the control unit in such a way that the corresponding specifications are complied with.

The invention is based on the object of creating a method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic map of an internal combustion engine on a test bench and a control unit for controlling a test bench for an internal combustion engine, the disadvantages mentioned not occurring.

The object is achieved in that the present technical teaching is provided, in particular the teaching of the independent claims and the embodiments disclosed in the dependent claims and the description.

The object is achieved in particular by creating a method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic diagram of an internal combustion engine on a test bench, in which a first operating point is selected in the characteristic diagram. The internal combustion engine is operated at the first operating point. In this case, a) a combustion chamber peak pressure setpoint value for a combustion chamber peak pressure is gradually reduced until a first operating parameter of the internal combustion engine is beyond a first predetermined limit value. For each change step of the gradual reduction of the combustion chamber syringe pressure target value, a respective setting value for the combustion chamber peak pressure target value and a resulting consumption value and / or emission value are stored. Then b) the operation of the internal combustion engine is continued with the combustion chamber peak pressure setpoint last reached, at which the first operating parameter was not yet beyond the first predetermined limit value. Then, c) a combustion focus setpoint value for a combustion focus is shifted early in steps until a second operating parameter of the internal combustion engine is beyond a second predetermined limit value. For each change step of the gradual shifting of the combustion focus setpoint value, a respective setting value for the combustion focus setpoint value and a consumption value and / or emission value resulting in each case are stored. Then d) the operation of the internal combustion engine is continued with the last reached combustion center of gravity setpoint, at which the second operating parameter was not yet beyond the second predetermined limit value. Finally, e) the combustion focus setpoint is gradually shifted to a late stage until a third operating parameter of the internal combustion engine is beyond a third predetermined limit value, with a respective setting value for the combustion focus setpoint and a resulting consumption value and / or emission value being stored for each change step .

In this way, it is quickly and easily possible, in an automated manner, to determine those consumption values and / or emission values for the set operating point of the characteristic diagram that can result from variation of at least the most important system and / or manipulated variables. After appropriate data entry of the map with the method proposed here, a maximum consumption value and / or emission value to be complied with can then be specified during later operation of the internal combustion engine it can be chosen that the respective specification with reference to the consumption and / or emission value is adhered to.

The method is very efficient and can particularly advantageously be carried out in a maximum of 15 minutes for each operating point in the characteristic diagram. A regulation which generates the manipulated variables of the internal combustion engine in accordance with the predetermined, operating point-dependent setpoint variables is advantageously already available in the control device of the internal combustion engine that is to be supplied with data. With the help of the method it is preferably achieved that the applicable emission regulations, especially for non-road applications, in a defined test cycle, for example C1 according to ISO 8178 Part 4, be respected. In particular, by taking into account the predetermined limit values, the method proposed here also takes into account the relevant component protection for the internal combustion engine with reference in particular to exhaust gas temperature, combustion chamber pressure gradient and combustion chamber peak pressure. Overall, the method provides a very efficient method that enables the internal combustion engine to be started up and calibrated quickly, with optimal values for operating points with a view to the requirements set with regard to emissions and / or consumption, depending on the application and engine concept, quickly and preferably in real time on the test bench can be determined.

In the context of the present technical teaching, the characteristic map of the internal combustion engine is in particular spanned by a speed of the internal combustion engine on the one hand and a torque of the internal combustion engine on the other.

An operating point of the internal combustion engine in the characteristic diagram is thus characterized by a specific combination of values on the one hand for the speed and on the other hand for the torque. During steps a) to e), the selected operating point is kept constant, i.e. the values selected as the operating point for the torque on the one hand and the speed on the other hand are not changed.

A setting value is understood here to mean, in particular, a value of an operating parameter, in particular a system and / or a manipulated variable of the internal combustion engine, which is set in order to increase the respective specified setpoint value, i.e. in particular, depending on the step, the combustion chamber peak pressure setpoint value or the combustion focus setpoint value, to adjust. In one embodiment of the method, however, the setting value can also be the respective setpoint value itself.

A consumption value is understood to mean, in particular, an instantaneous fuel consumption, in particular based on a unit of time or a route, possibly calculated virtually.

An emission value is understood here to mean, in particular, a pollutant concentration or particle concentration, in particular nitrogen oxide concentration or soot concentration, in the exhaust gas. The emission value is particularly preferably a nitrogen oxide concentration in the exhaust gas.

A consumption and / or emission value resulting in each case is understood here to mean, in particular, such a consumption and / or emission value which is at the respective specified setpoint, that is, depending on the step, the combustion chamber peak pressure setpoint or the combustion focus setpoint, or at the the set value results in each case. The respective storage of the setting value, the consumption value and / or the emission value thus results in an assignment of the consumption value and / or emission value to the respective setting value and at the same time to the respective target value.

The first operating parameter, the second operating parameter and the third operating parameter can in principle be the same operating parameter, but also different operating parameters. In particular, in each step of the method, in particular in each change step, a plurality of operating parameters are checked to determine whether predetermined limit values are reached or exceeded for these operating parameters, the step-by-step change in the setpoint being terminated and the method being continued with the next method step if one of the operating parameters under consideration exceeds the limit value assigned to it. In this respect, the first operating parameter, the second operating parameter and the third operating parameter are in each case those operating parameters in the respective method steps which chronologically first exceed the limit value assigned to them. Correspondingly, the first predetermined limit value, the second predetermined limit value and the third predetermined limit value are each the limit values assigned to the corresponding operating parameters. The first predetermined limit value, the second predetermined limit value and the third predetermined limit value can also be limit values of the same operating parameter.

The fact that an operating parameter lies beyond a limit value means that the limit value is transcended on the basis of the values for the operating parameter that were previously present during operation of the internal combustion engine. The fact that the limit value is transcended or "exceeded" in this sense does not necessarily mean that the respective operating parameter assumes a value that is greater than the assigned limit value; impermissible value range for the operating parameter is exceeded. This can possibly also mean that the operating parameter becomes smaller than the predetermined limit value, depending on the particular operating parameter and limit value considered.

A shift of the combustion focus setpoint “early” is understood here, in particular, to mean that the combustion focus is forward in time or is smaller Crankshaft angles is shifted within a working cycle of the internal combustion engine. Correspondingly, a shift “late” is understood to mean that the center of combustion is shifted backwards in time or to larger crankshaft angles within the work cycle.

The combustion center of gravity is understood to mean, in particular, a point in time or a crankshaft angle at which 50% of the fuel mass used or 50% of the chemical energy introduced into a combustion chamber of the internal combustion engine in the form of the fuel is converted. The fact that the combustion center of gravity is changed towards an early stage means in particular that it moves towards an earlier point in time relative to a top dead center position of a piston of the internal combustion engine, which is preferably designed as a reciprocating piston engine, which separates a compression stroke from an operating stroke and which is also referred to as ignition TDC or an earlier crankshaft angle is changed; in particular, it is moved closer to the ignition TDC if the focus of combustion is after the ignition TDC. Correspondingly, a change in the center of combustion to late means that the center of combustion is shifted relative to ignition TDC in the direction of a later point in time or later crankshaft angle, in particular being further removed from ignition TDC if the combustion focus is after ignition TDC lies. The combustion center of gravity is typically associated with an injection time, in particular the start of injection; in particular, it can be specified by selecting the injection time. The center of combustion can be adjusted earlier or later, in particular, by changing the injection time. A change in the point of injection early or late corresponds in an analogous manner to a change in the combustion center of gravity to early or late, although the start of injection is typically before ignition TDC. Thus, an early change in the start of injection means an increase in the distance between the injection timing and ignition TDC, while a late change in the start of injection means that the injection timing is approaching ignition TDC.

The terms “time” and “angle”, the latter in the sense of crankshaft angle, are used synonymously here in the context of the present technical teaching. When, for example, an intake valve closing time is mentioned, what is meant is, in particular, an intake valve closing angle in the sense of the corresponding crankshaft angle within a working cycle.

According to a further development of the invention, it is provided that the internal combustion engine is operated under constant conditions for a predetermined time interval before step a) and in steps b) and d). This enables the operation of the internal combustion engine to be stabilized under the respective operating conditions, which ensures that meaningful values can be obtained for the characteristic diagram, in particular with the exclusion of transient effects.

Constant operation of the internal combustion engine means in particular that at least a plurality of operating parameters, preferably all operating parameters of the internal combustion engine, are kept constant.

In particular, before step a) and in steps b) and d), an inlet air pressure, the combustion chamber peak pressure setpoint and the combustion focus setpoint are kept constant. In this case, constant values are preferably established for a combustion chamber pressure gradient and an exhaust gas temperature of the internal combustion engine.

The intake air pressure is, in particular, a combustion air pressure that is present upstream of an intake valve of the internal combustion engine, in particular a boost pressure.

The inlet air pressure is preferably set, particularly preferably regulated, by controlling a turbine bypass passage cross section, in particular a turbine bypass flap angle, as a manipulated variable.

According to a further development of the invention, it is provided that the internal combustion engine is also operated after step e) for a predetermined time interval under constant conditions. This also advantageously results in a stabilization of the running of the internal combustion engine, in particular with the setting of values for the combustion chamber pressure gradient and the exhaust gas temperature.

According to a further development of the invention, it is provided that the inlet air pressure is kept constant in each of steps a) to e). This in particular enables the method to be carried out in a stable, reproducible and meaningful manner.

According to a further development of the invention, it is provided that in step a) the combustion focus setpoint is also kept constant. In addition, the combustion chamber peak pressure setpoint is kept constant in steps c) and e). This also enables the method to be carried out in a stable, reliable and reproducible manner.

According to a development of the invention it is provided that the first operating parameter, the The second operating parameter and the third operating parameter are each selected from a group consisting of: a combustion chamber peak pressure, an intake valve closing time, a combustion focus, an injection start, an exhaust gas temperature, a combustion chamber pressure gradient and a fuel consumption. In particular, these operating parameters are meaningful and relevant to the question of when the step-by-step change in a setpoint should be terminated, in particular to ensure safe operation of the internal combustion engine, particularly with regard to component protection.

Preferably, at least a plurality, preferably each of the operating parameters mentioned here as group members, are monitored in each step of the method, in particular in each change step, for an assigned limit value being exceeded. The step-by-step change in the individual process steps is always terminated when a first operating parameter in terms of time, selected from the group members, exceeds the limit value assigned to it.

It has been found that in step a) the exhaust gas temperature, as the first operating parameter, typically exceeds the limit value assigned to it. The first predetermined limit value is therefore typically an exhaust gas temperature limit value, and the first operating parameter is preferably the exhaust gas temperature.

It has been found that typically in step c) the combustion chamber pressure gradient is the first to exceed the limit value assigned to it. The second operating parameter is thus preferably the combustion chamber pressure gradient, and the second predetermined limit value is, in particular, a combustion chamber pressure gradient limit value.

It has been found that in step e) the fuel consumption typically first exceeds the limit value assigned to it. The third operating parameter is therefore typically fuel consumption and the third predetermined limit value is typically a fuel consumption limit value.

According to a further development of the invention, it is provided that in steps a), c) and e) a value for at least one operating parameter is additionally stored in each change step, the at least one operating parameter being selected from a group consisting of: the combustion chamber peak pressure , the intake valve closing time, the center of combustion, the start of injection, the exhaust gas temperature, the combustion chamber pressure gradient, and the fuel consumption. In particular, this results in extensive data input to the characteristic field, so that when the internal combustion engine is later operated, system and manipulated variables can be selected in a targeted manner in order to comply with the specifications with regard to emissions and / or fuel consumption.

According to a further development of the invention, it is provided that at least one second operating point is selected in the map, the internal combustion engine being operated at the second operating point, and steps a) to e) being carried out for the second operating point. The method proposed here is therefore carried out in a preferred embodiment not only for one operating point of the characteristic diagram, but at least for two operating points.

The selection of an operating point, the operation of the internal combustion engine at the selected operating point and the implementation of steps a) to e) are preferably repeated for a plurality of operating points. In this way, the method is advantageously carried out for a large number of operating points in the characteristic map, so that the characteristic map is data in a simple, efficient and inexpensive manner to a large extent, preferably completely.

In a preferred embodiment, the selection of an operating point, the operation of the internal combustion engine at the selected operating point and the implementation of steps a) to e) are repeated for a predetermined number of operating points, the predetermined number of operating points in particular by a predetermined test cycle, for example C1 -Test cycle according to ISO 8178 part 4 is specified.

According to a development of the invention, it is provided that the change in the combustion chamber peak pressure setpoint is implemented in step a) by changing the point in time when the inlet valve closes. In this respect, in particular the inlet valve closing time is, in a preferred embodiment, the setting value in step a).

As an alternative or in addition, the change in the setpoint value for the focus of combustion is implemented in steps c) and e) by changing the start of injection. In this respect, according to a preferred embodiment, the start of injection is the setting value in steps c) and e).

The operating parameters or manipulated variables proposed here are each particularly suitable for setting the corresponding setpoint values.

Finally, the task is also achieved by adding a control unit to control a test bench is created for the internal combustion engine, the control unit being set up to carry out the method according to the invention or one of the previously described embodiments of the method. In connection with the control device, there are in particular the advantages that have already been explained in connection with the method.

The control device proposed here is a test bench control device which is set up to control the test bench. This is to be distinguished from a control device for the operation of the internal combustion engine, which, in contrast to the test bench control device, is also referred to as an internal combustion engine control device.

The relevant characteristic diagrams are in particular calibrated with the aid of the test bench control unit. The characteristic fields with data in this way are then used later in the internal combustion engine control unit to operate the internal combustion engine.

• 1 eine schematische Darstellung eines Ausführungsbeispiels eines Prüfstands für eine Brennkraftmaschine mit einem Ausführungsbeispiel eines Steuergeräts, und
• 2 eine schematische Darstellung einer Ausführungsform des Verfahrens in Form eines Flussdiagramms.

The invention is explained in more detail below with reference to the drawing. Show:

• 1 a schematic representation of an embodiment of a test stand for an internal combustion engine with an embodiment of a control device, and
• 2 a schematic representation of an embodiment of the method in the form of a flowchart.

1 shows a schematic representation of an exemplary embodiment of a test stand 1 on which an internal combustion engine 3 is arranged. The test bench 1 is set up in particular to automatically generate consumption and / or emission values in at least one operating point of a characteristic diagram of the internal combustion engine 3 , in particular in a plurality of operating points of the map. In particular, the test bench 1 a control unit 5 , that is to say a test bench control device, which is set up to carry out an embodiment of a method, explained in more detail below, for the automated determination of consumption and / or emission values in at least one operating point, in particular a plurality of operating points, of the characteristic map. The internal combustion engine 3 has at least one combustion chamber 7th on. It is possible that the internal combustion engine 3 is designed as a single-cylinder test engine. The internal combustion engine 3 but it can also be a series-produced internal combustion engine that is put to the test 1 is operated, in particular for later use in series operation of the internal combustion engine 3 to collect applicable data.

The internal combustion engine 3 is designed in particular as a reciprocating piston engine. To that extent is the combustion chamber 7th a piston that can be displaced in a reciprocating manner 9 assigned. Next are the combustion chamber 7th an inlet path 11th with an inlet valve 13th for supplying combustion air into the combustion chamber 7th , as well as an exhaust path 15th with an exhaust valve 17th assigned to the removal of exhaust gas.

The inlet valve 13th a variable valve train is assigned, so that an intake valve closing time phiES for the intake valve 13th can be specified variably. This is what the control unit is for 5 preferably in a manner not shown with the variable valve drive of the inlet valve 13th effectively connected. It is possible that in addition the exhaust valve 17th a variable valve train is also assigned.

The combustion chamber 7th is also a fuel injector 19th for feeding fuel into the combustion chamber 7th , in particular for direct introduction, in particular direct injection or direct injection, assigned. The control unit 5 is in a manner not expressly shown with the fuel injector 19th operatively connected in order to specify a start of injection (BOI).

The inlet path 11th is a not shown here, with the control unit 5 operatively connected pressure sensor assigned to determine an inlet air pressure p5. This pressure sensor is also with the control unit 5 effectively connected.

The combustion chamber 7th a combustion chamber pressure sensor, also not shown here, is assigned to determine a combustion chamber pressure, in particular in a time-resolved manner. This combustion chamber pressure sensor is also connected to the control unit 5 effectively connected. The control unit 5 is set up in particular to determine a combustion chamber peak pressure pmax and a temporal combustion chamber pressure gradient dp / dt from the combustion chamber pressure, which is preferably recorded in a time-resolved manner.

The outlet path 15th a temperature sensor (not shown here) is assigned, which is also associated with the control unit 5 is operatively connected to determine an exhaust gas temperature TAbgas.

The internal combustion engine 3 has an exhaust gas turbocharger 21 with one in the exhaust path 15th arranged turbine 23 and one in the inlet path 11th arranged compressor 25th on, with the turbine 23 with the compressor 25th is effectively connected to the drive. To the turbine 23 is a turbine bypass 27 with an adjustable bypass flap 29 arranged, the bypass valve 29 with the control unit 5 is operatively connected in a manner not shown here, so that the control unit 5 can specify a bypass flap angle αTBP. The bypass flap angle αTBP determines in particular the inlet air pressure p5.

The control unit 5 is also set up to determine an instantaneous fuel consumption. This can be done using a suitable sensor, or computationally, for example, using the one in the control unit 5 known control of the fuel injector 19th .

2 shows spread over the 2A , 2 B , 2C and 2D a schematic representation of an embodiment of a method for the automated determination of consumption and / or emission values at an operating point of a characteristic diagram of the internal combustion engine 3 put to the test 1 . The method steps shown below are preferably carried out one after the other for a plurality of operating points, ie in particular repeated, in particular for a predetermined number of predetermined operating points, the operating points being in particular predetermined by a test cycle.

First of all, as part of the method, a first operating point is selected in the characteristics map, and so is the internal combustion engine 3 is operated in the first operating point.

This is in the start of the procedure, in a phase 0 , an engine run to stabilize the engine is carried out, the internal combustion engine 3 is operated for a predetermined time interval under constant conditions. In particular, an inlet air pressure setpoint p5, setpoint, a combustion chamber peak pressure setpoint value pmax, setpoint, and a combustion focus setpoint value phi50, setpoint are kept constant. As already stated, the bypass flap angle αTBP is used as the manipulated variable for the inlet air pressure p5; The inlet valve closing time phiES is used as the manipulated variable for the combustion chamber peak pressure setpoint pmax, setpoint; The start of injection BOI serves as the manipulated variable for the setpoint value for the focus of combustion. Under these conditions, measured values are obtained for the combustion chamber pressure gradient dp / dt and the exhaust gas temperature TAbgas.

The initial values for the inlet air pressure setpoint p5, setpoint, the combustion chamber peak pressure setpoint pmax, setpoint, and the combustion focus setpoint value phi50, setpoint can in particular be fixed or selected according to suitable criteria at the beginning of the method. It is also possible for these values to be specified manually by a test bench driver.

The procedure then continues after the predetermined time interval for the phase 0 in one phase 1 continued, which corresponds to step a) of the method. Here, the combustion chamber peak pressure setpoint pmax, setpoint is varied, namely gradually reduced, in particular in that the inlet valve closing time phiES is shifted early in steps. The inlet air pressure setpoint p5, soll and the combustion focus setpoint phi50, are kept constant.

For each change step, it is checked whether one of the following operating parameters transcends a predetermined limit value assigned to it, in particular whether the combustion chamber peak pressure pmax exceeds a predetermined combustion chamber peak pressure limit value pmax, max, whether the intake valve closing time phiES is an earliest, in this respect minimum intake valve closing time phiES, min falls below whether the exhaust gas temperature TAbgas exceeds a predetermined exhaust gas temperature limit value TAbgas, max, and whether the combustion chamber pressure gradient dp / dt exceeds a predetermined combustion chamber pressure gradient limit value dp / dt, max.

The change in the combustion chamber peak pressure setpoint pmax, soll is continued until a first operating parameter of this operating parameter is beyond the first predetermined limit value assigned to it. For each change step, a respective setting value for the combustion chamber peak pressure setpoint pmax, soll, i.e. the combustion chamber peak pressure setpoint pmax, soll itself and / or the corresponding inlet valve closing time phiES, preferably both, is stored; instantaneous consumption value be and at least one emission value, here in particular a nitrogen oxide concentration [NOx], stored in the exhaust gas. In addition, the exhaust gas temperature TAbgas and the combustion chamber pressure gradient dp / dt are preferably stored for each change step.

In this first step a), i.e. in phase 1 , the exhaust gas temperature limit value TAbgas, max is expected to be reached and exceeded first. If this is the case, and / or if one of the other monitored operating parameters transcends the limit value assigned to it, phase becomes 1 with the variation of the combustion chamber peak pressure setpoint pmax, setpoint and thus at the same time also the combustion chamber peak pressure pmax, and the method is continued in a step b) by the internal combustion engine 3 with the last reached combustion chamber peak pressure setpoint pmax, soll and thus at the same time the last reached inlet valve closing time phiES is continued, at which none of the predetermined limit values for the monitored operating parameters was transcended. In particular, a change step, namely the last change step with which the first predetermined limit value was transcended, is thus reversed, and the internal combustion engine 3 will continue to operate with the values for the operating parameters achieved in the penultimate change step.

The procedure is now according to 2 B in one phase 12th continued in step b), the internal combustion engine 3 is again operated for a predetermined time interval under constant conditions. The constant conditions correspond in particular to those previously for phase 0 explained conditions, where now as a constant value for the combustion chamber peak pressure setpoint pmax, the in phase 1 , ie step a), the last reached value is used.

After the predetermined time interval for step b) has elapsed, the method is in one phase 2 , ie continued in step c). Here, the inlet air pressure setpoint p5, soll and the combustion chamber peak pressure setpoint pmax, soll are kept constant, and again for the combustion chamber peak pressure setpoint pmax, the in phase 1 , ie step a), value reached is used. The combustion focus setpoint phi50, setpoint is now gradually shifted towards the early stage, in particular by the fact that the start of injection BOI is moved towards the early as the manipulated variable. For each change step, values for the combustion focus setpoint phi50, soll and / or the start of injection BOI, preferably for both, for the consumption value be, the emission value, here the nitrogen oxide concentration [NOx], and preferably the exhaust gas temperature TAbgas and the combustion chamber pressure gradient dp / dt saved.

At the same time, in each change step, the operating parameters for combustion focus phi50, start of injection BOI, exhaust gas temperature TAbgas and combustion chamber pressure gradient dp / dt are monitored for transcending a limit value assigned to them in each case. In particular, it is monitored here whether the combustion focus phi50 falls below an earliest combustion focus limit value or minimum combustion focus limit value phi50, min assigned to it, or whether the start of injection BOI falls below an earliest start of injection or start of injection limit value BOI, min assigned to it.

The step-by-step change in the combustion focus setpoint value phi50, setpoint is ended when a second operating parameter is for the first time beyond a second predetermined limit value. In step c), the combustion chamber pressure gradient dp / dt is expected to first exceed the combustion chamber pressure gradient limit value dp / dt, max.

In this case, the method is continued in step d), the phase 2 is terminated. Thus, the variation in the center of combustion phi50 is also ended early.

The operation of the internal combustion engine 3 is then continued with the last reached value of the combustion focus setpoint phi50, soll and thus at the same time the last reached value of the start of injection BOI, at which none of the operating parameters had yet transcended the limit value assigned to it. So again - as already explained - one last change step is reversed.

The procedure is then carried out according to 2C in one phase 23 , ie step d), continued with the internal combustion engine 3 is again operated for a predetermined time interval under constant conditions. Again, those previously in connection with phase 0 and phase 12th said operating parameters kept constant, with the one hand now for the combustion chamber peak pressure setpoint pmax, the in phase 1 , Step a), is used, on the other hand, for the combustion focus setpoint phi50, the value reached in phase 2 / step c) is used. In turn, measured values are set for the combustion chamber pressure gradient dp / dt and the exhaust gas temperature TAbgas.

After the predetermined time interval for step d) has elapsed, the method is now in step e), here as a phase 3 referred to, continued.

The inlet air pressure setpoint p5, soll and the combustion chamber peak pressure setpoint pmax, soll are now kept constant, the value achieved in phase 1 / step a) again being used for the combustion chamber peak pressure setpoint pmax, soll.

The combustion focus setpoint phi50, setpoint is gradually shifted to late by shifting the start of injection BOI to late as a manipulated variable. The values of the combustion focus setpoint phi50, soll and / or the start of injection BOI, preferably both, resulting in each change step, are stored, as well as the consumption value be and the emission value, here the nitrogen oxide concentration [NOx], and preferably also the exhaust gas temperature TAbgas and der Combustion chamber pressure gradient dp / dt.

The delayed shift is continued until a third operating parameter lies beyond a third predetermined limit value, the following operating parameters now being monitored: The combustion focus phi50, the start of injection BOI, the exhaust gas temperature TAbgas, the combustion chamber pressure gradient dp / dt and the consumption value be.

In particular, it is monitored whether the combustion focus phi50 exceeds a latest combustion focus limit value or maximum combustion focus phi50, max assigned to it, whether the injection start BOI exceeds a latest injection start or maximum injection start limit value BOI, max assigned to it, and whether the consumption value for one of it assigned maximum consumption value or consumption value limit value be, max exceeds.

In this case, the consumption value will probably first exceed the consumption value limit value be assigned to it, max.

In this case phase ends 3 and thus the variation in the center of combustion phi50 towards late. The operation of the internal combustion engine 3 is now continued with the last reached value of the combustion focus setpoint phi50, soll and thus the start of injection BOI at which none of the monitored operating parameters has yet transcended the limit value assigned to it.

The procedure is now in accordance with 2D ) with a phase 4th continued with the internal combustion engine 3 is again operated under constant conditions, in particular the previously in phases 0, 12th and 23 operating parameters kept constant are kept constant, but now in phase 4th the combustion chamber peak pressure setpoint pmax, setpoint from phase 1 / step a) is used, with the value reached in phase 3 / step e) being used for the combustion focus setpoint value phi50, setpoint. This in turn results in measured values for the combustion chamber pressure gradient dp / dt and the exhaust gas temperature TAbgas.

After a predetermined time interval for phase 4th the procedure ends. The stored values now indicate permissible ranges in which the system values for determining the optimal consumption and emission values of the internal combustion engine 3 lie.

As already stated, this method sequence is now preferably repeated for further operating points, in particular for operating points of a predetermined test cycle.

Claims (10)

Method for the automated determination of consumption and / or emission values in at least one operating point of a characteristic map of an internal combustion engine (3) on a test bench (1), a first operating point being selected in the characteristic map, the internal combustion engine (3) being operated at the first operating point will, where a) a combustion chamber peak pressure target value for a combustion chamber peak pressure is gradually reduced until a first operating parameter of the internal combustion engine (3) lies beyond a first predetermined limit value, with a respective setting value for the combustion chamber peak pressure target value and a respectively resulting consumption value and / or for each change step Emissivity can be stored, where b) the operation of the internal combustion engine (3) is continued with the combustion chamber peak pressure setpoint last reached, at which the first operating parameter was not yet beyond the first predetermined limit value, wherein c) a combustion focus setpoint value for a combustion focus point is shifted early in steps until a second operating parameter of the internal combustion engine (3) is beyond a second predetermined limit value, with a respective setting value for the combustion focus setpoint value and a respectively resulting consumption value and for each change step / or emission value are stored, whereby d) the operation of the internal combustion engine (3) is continued with the last achieved combustion center of gravity target value, at which the second operating parameter was not yet beyond the second predetermined limit value, wherein e) the combustion focus setpoint is gradually shifted late until a third operating parameter of the internal combustion engine (3) is beyond a third predetermined limit value, with a respective setting value for the combustion focus setpoint and a resulting consumption value and / or emission value for each change step get saved. Procedure according to Claim 1 , characterized in that the internal combustion engine (3) is operated before step a) and in steps b) and d) in each case for a predetermined time interval under constant conditions. Method according to one of the preceding claims, characterized in that the internal combustion engine (3) is operated after step e) for a predetermined time interval under constant conditions. Method according to one of the preceding claims, characterized in that an inlet air pressure is kept constant in each of steps a) to e). Procedure according to Claim 4 , characterized in that - in step a) the combustion center target value is also kept constant, and that - in steps c) and e) the combustion chamber peak pressure target value is also kept constant. Method according to one of the preceding claims, characterized in that the first operating parameter, the second operating parameter and the third operating parameter are each selected are from a group consisting of: a combustion chamber peak pressure, an intake valve closing time, a combustion focus, an injection start, an exhaust gas temperature, a combustion chamber pressure gradient, and a fuel consumption. Method according to one of the preceding claims, characterized in that, in steps a), c) and e), in each change step a value for at least one operating parameter selected from a group consisting of: a combustion chamber peak pressure, an inlet valve closing time, a combustion focus, a start of injection, an exhaust gas temperature, a combustion chamber pressure gradient, and a fuel consumption, is stored. Method according to one of the preceding claims, characterized in that at least one second operating point is selected in the map, wherein the internal combustion engine (3) is operated in the second operating point, wherein steps a) to e) are carried out for the second operating point; wherein the selection of an operating point, the operation of the internal combustion engine at the selected operating point and the implementation of steps a) to e) are preferably repeated for a plurality of operating points. Method according to one of the preceding claims, characterized in that - the change in the combustion chamber peak pressure setpoint is implemented in step a) by changing an intake valve closing time, and / or that - the change in the combustion focus setpoint in steps c) and e) is implemented by changing a start of injection. Control device (5) for controlling a test stand (1) for an internal combustion engine (3), the control device (5) being set up to carry out a method according to one of the Claims 1 until 9 .

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