WO2018041583A1

WO2018041583A1 - Determining operating states of an internal combustion engine by means of a generator regulator of an electric machine which is coupled to the internal combustion engine

Info

Publication number: WO2018041583A1
Application number: PCT/EP2017/070276
Authority: WO
Inventors: Paul Mehringer; Joerg Maas; Udo Schulz
Original assignee: Robert Bosch Gmbh
Priority date: 2016-09-01
Filing date: 2017-08-10
Publication date: 2018-03-08
Also published as: CN109642510A; DE102016216509A1; EP3507476A1

Abstract

The invention relates to a method for determining an operating state (128a, 132a) of an internal combustion engine (112), comprising the following steps: determining the temporal course of a rotational speed (n) of an electric machine (114) coupled to the internal combustion engine (112); determining a mean value (DMD) of the rotational speed (122) from the temporal course of the rotational speed (122) and determining at least one rotational speed pattern (128, 132), produced by the internal combustion engine (112), from the temporal course of the rotational speed (122), the rotational speed pattern having an oscillation (O) superimposed over the temporal course of the mean value (DMD) of the rotational speed (122); and determining at least one operating state (128a, 132a) of the internal combustion engine (112) by comparing the mean value (DMD) of the rotational speed (122) to a first threshold value (Thl) and comparing an undulation (W) of the oscillation (O) superimposed over the temporal course of the mean value (DMD) of the rotational speed (122) to a rotational speed range (B). Furthermore, the invention relates to a corresponding computing unit (118) which is configured to carry out the method, to an electric machine (114) comprising the computing unit (118) and to a corresponding computer program.

Description

description

title

DETERMINING OPERATING STATES OF AN INTERNAL COMBUSTION ENGINE THROUGH A GENERATOR CONTROLLER OF AN ELECTRICAL MACHINE COUPLED TO THE INTERNAL COMBUSTION ENGINE

The present invention relates to a method for determining an operating state of an internal combustion engine, as well as a computing unit, preferably a controller for an electrical machine and a computer program for its implementation.

State of the art

For regulating the vehicle electrical system voltage in vehicles, electrical machines, in particular externally excited electrical machines, can be used. These have a controller which regulates the excitation current of the electric machine as a function of the vehicle electrical system voltage. Such a machine is known from DE 10 2012 204 751 AI.

In addition, it is also possible to use so-called intelligent controller, set, for example, in the operating state "overrun" a higher excitation current to the electric machine to recover electrical energy o- or in the case of the operating state "acceleration" by the internal combustion engine, the output currents of reduced electrical machine to provide more drive torque to accelerate the vehicle.

If an electrical machine is generally referred to below, this can also be an electric machine which can be operated as a generator and / or motor, for example a so-called starter generator. The detection of the operating states of the internal combustion engine is currently the responsibility of the engine control unit, which recognizes these operating conditions on the basis of its own control specifications and makes appropriate specifications with respect to the respective operating state of the internal combustion engine to the controller of the electric machine by means of suitable interfaces. As a result, the controller controls the current output of the generator via a nominal voltage specification of the vehicle electrical system voltage.

However, this method is very expensive, since the respective operating conditions of the internal combustion engine are only determined externally in the engine control unit of the internal combustion engine, the determined operating conditions are transmitted to the controller of the electric machine and then, if necessary, the controller the corresponding to the respective operating condition of the engine control requirements to the electric machine.

In addition, a communication link between the controller and engine control unit must be present and always maintained in order to enable a corresponding control of the electric machine.

It would therefore be desirable for the operating state detection of the internal combustion engine not to be based on control specifications of the engine control unit but on objective state variables or measurement variables of the electric machine based thereon that reflect the operating state of the internal combustion engine.

Disclosure of the invention

A method for determining an operating state of an internal combustion engine, as well as a computer unit and a computer program for carrying it out with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims, as well as the following description.

Advantages of the invention The method is used to determine an operating state of an internal combustion engine by means of a control unit, wherein preferably the control unit is designed as a controller of a coupled to the internal combustion engine electric machine.

The electric machine can be driven by the internal combustion engine, wherein the electric machine with the internal combustion engine firmly connected and can be coupled to the crankshaft, for example by means of a belt drive. Within the controller, the time profile of a rotational speed of the electrical machine is determined in a first method step. The speed of the electric machine can preferably be determined from the time profile of at least one phase signal of the electric machine. In the present case, a phase signal is at least one of the phase voltages and / or one of the phase currents, at least one of the stator-side phase windings of the electrical machine, in particular against a fixed reference potential, such. B. mass, measured. In addition, it may be preferred, alternatively or cumulatively, to determine the profile of the rotational speed of the electrical machine by means of a rotational speed sensor which is in operative connection with the electric machine or can be provided thereon.

In a further method step, an average value of the rotational speed is determined from the time profile of the rotational speed and at least one rotational speed pattern effected by the internal combustion engine is determined from the time profile of the rotational speed. The speed pattern caused by the internal combustion engine has an oscillation superimposed on the time profile of the mean value of the rotational speed, which is reflected in the time course of the rotational speed of the electric machine. The mean value of the speed is determined over a determinable time interval, which typically comprises several periods of the oscillation. The determinable time interval can result from a specific number of oscillation periods of the instantaneous speed, but should have at least one oscillation period caused by compression and decompression and / or one working cycle of the cylinder. In a further step of the method, the operating state of the internal combustion engine is determined by comparing the mean value of the rotational speed with a first threshold value and comparing a ripple of an oscillation superimposed on the time profile of the mean value of the rotational speed with a rotational speed band. Preferably, the speed band is determined in terms of absolute value by the first threshold value and a further threshold value, wherein the first threshold value and the further threshold value define a speed range in which the idling mode of the internal combustion engine takes place.

By such a threshold value comparison of the mean value of the speed and the comparison of the ripple of the temporal course of the mean value of the speed superimposed oscillations with a speed band, in a very simple manner and with very little computational and storage effort by the controller of the electric machine, a Operating state determination of the internal combustion engine can be effected.

The preferred operating states to be recognized are the operating state of the internal combustion engine, compression stroke and / or power stroke, preferably ignition of a fuel-air mixture, in particular idling operation and operation outside the idling operation (non-idling operation), e.g. in partial load operation and / or full load operation. In particular, the abovementioned operating states of the internal combustion engine can be determined in a particularly simple and efficient manner by means of the method described at the outset and distinguished accordingly.

In this case, it is further preferred that the operating state idling operation of the internal combustion engine is detected such that the mean value of the rotational speed is greater than the first threshold value, particularly preferably greater than the first threshold value and less than a further threshold value, and the waviness of the temporal Course of the mean value of the speed superimposed oscillation runs within the speed band and is smaller in magnitude than the speed band. Thus, in the preferred embodiment for idle mode detection, a threshold band will be between a first threshold and a comparatively larger one compared to the first threshold determined further threshold value of the rotational speed, in which case it is concluded that the operating state idle operation when the average value of the rotational speed is within the threshold band, and the ripple of the oscillation within the speed band runs. In the present case, the amplitude or average amplitude is the difference between the maximum of the oscillation and the mean value or the minimum of the oscillation and the mean value, the ripple being approximately twice the amplitude. Thus, in the present case it is particularly preferred if the maxima of the oscillation always lie below the further threshold value during idling operation and are therefore smaller than the further threshold value. The same applies to the detection of further operating states, as described below.

In a further preferred embodiment of the invention, the operating state non-idling operation, in particular partial load operation, the internal combustion engine is detected such that the average value of the rotational speed is greater than the first threshold, preferably greater than the further threshold, and the ripple of the time course The superimposed oscillation of the mean value of the rotational speed runs at least partially within the rotational speed band and is greater in magnitude than the rotational speed band. This means that at least the regions of the oscillation which have a local maximum of the rotational speed (positive oscillations) have time regions which run outside the rotational speed band. By the first criterion, which runs the mean value of the speed above the first threshold, the speed range can be detected, which lies between the mean in the idling mode and the further threshold value. Due to the further requirement that the mean value of the rotational speed is greater than the further threshold value, it is possible to detect all further rotational speeds for a non-idling operation which are outside the idling speed band. It has been recognized that by the delivery of torque by the internal combustion engine, the amplitude or ripple of the oscillation increases depending on the output of torque by the internal combustion engine. This effect can be used to compare the amplitude level or ripple with the comparison with a speed band and the comparison of the Average value of the speed to determine the current operating state. Thus, from a combination of a comparison of the mean value of the speed with at least one of the threshold values and the determination that the amplitudes or the waviness of the oscillations exceed the speed band used to define the idling mode in absolute terms, it can be concluded that a non-idling operating state, in particular a partial load operation is present. An amount exceeding the speed band means that the areas of the oscillation, which in particular have a local maximum of the rotational speed (positive oscillations), have time ranges which run outside the rotational speed band.

In principle, it is preferred that the first threshold value define a lower speed limit and the further threshold value an upper speed limit for an idling mode. It is understood that the respective speed limits can be adjusted according to the internal combustion engine used. The idle mode can thus be used to a certain extent as a reference operating state; in particular, the speeds to be expected can be used as a reference for the threshold values or the rpm band for detecting the operating states.

In a further embodiment of the invention, it is preferred that with a changing mean value of the rotational speed, the mean value of the rotational speed runs essentially centrally in the rotational speed band. The speed band is determined by the first threshold and the further threshold only in terms of amount. This makes it possible that, for example, the speed band can be adapted to a time-varying mean value such that the speed band follows the gradient of the time profile of the mean value of the speed. Thus, during a speed increase, for example during an acceleration process in partial load operation, a corresponding differentiation of the operating states can be made.

In a further preferred embodiment, the method has a further method step for regulating the electric machine by the excitation current of the electric machine, in a respective operating state of the Internal combustion engine is controlled such that the braking torque of the electric machine is increased or decreased.

A corresponding control of the electric machine on the basis of the respectively determined operating state (in particular the operating conditions partial load operation and / or idling) of the internal combustion engine is advantageous, since thereby in the case of an acceleration operation (eg partial load operation or full load operation), for example, by as much as possible required by the internal combustion engine and output torque is to be converted into propulsion (full load), the braking torque of the electric machine reduced, can even be lowered to zero, so as not to affect the acceleration process. A suitably adapted control can also be used advantageously during a partial load operation of the internal combustion engine. The same applies to the braking torque of the electric machine during idling operation of an internal combustion engine, since during the idling operation of the internal combustion engine this is particularly sensitive to the action of an external braking torque, which may mean a reduction in the speed of the internal combustion engine below a critical threshold in the worst case, so that the internal combustion engine is strangled. By a reliable detection of the idle state of the internal combustion engine by means of the controller of the electric machine, thus the rule specification of the excitation current and thus the braking torque of the electric machine can be specified such that the critical speed threshold of the internal combustion engine is not reached or fallen below.

In addition, it is particularly preferred that the excitation current is controlled by specifying a nominal voltage and / or a nominal current of the motor vehicle electrical system or by specifying a maximum current output, the maximum current output and / or the maximum excitation current, preferably being parameterized according to operating states of the internal combustion engine.

By such excitation current control, which is based on a specification of the target voltage or the desired current of the motor vehicle electrical system, a corresponding control of the electric machine, in particular a nearly braking torque-free running of the electric machine in the acceleration mode of the internal combustion engine or a correspondingly reduced Bremsmomentbeaufschlagung during idling operation, implemented. Alternatively, such a regulation can also be regulated by regulating a maximum current to be delivered to the motor vehicle electrical system, wherein this maximum current can in turn be parameterized as a function of the respective operating states of the internal combustion engine. Such a parameterization can either be done numerically or be implemented by querying the stored in a stored map parameters.

The use of a computing unit, in particular a controller for an electrical machine, which is preferably arranged in the electric machine, but can also be arranged externally to the electric machine is for the determination of the operating conditions idle mode and non-idling mode, in particular part-load operation, and for a Any resulting regulation of the braking torque of the electric machine is particularly advantageous, as this allows the method according to the invention to be carried out in a particularly simple manner.

The arithmetic unit is therefore configured to execute the method, which means that the arithmetic unit has a corresponding arithmetic processor and / or a corresponding data memory with a computer program stored thereon and / or is set up by a corresponding integrated circuit to execute the method according to the invention. The execution of the method in a controller of the electric machine is also advantageous, since both the evaluation of the signals, determining the respective operating conditions and adjusting the electrical machine based on the determined operating conditions without additional external communication links and independent of an external computer, memory and / or rule architecture.

The implementation of the method in the form of a computer program, which is preferably available on a data medium, in particular a memory, in the arithmetic unit for carrying out the method is advantageous, because this causes very low costs, especially if an executive controller is still used for other tasks, and therefore already exists. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, as are frequently known from the prior art.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

Brief description of the drawings

Figure 1 shows a schematic representation of an operating state-based control of an electric machine by the engine control means of a communication link according to the prior art;

FIG. 2 a shows an internal combustion engine as well as an electrical machine according to the invention coupled to the internal combustion engine in a first schematic representation;

FIG. 2b shows an internal combustion engine, as well as an electric machine coupled to the internal combustion engine, according to a further exemplary embodiment, in a schematic representation;

FIG. 2c shows an electrical machine coupled to a vehicle electrical system in an enlarged schematic representation;

Figure 3 shows a time profile of a phase voltage of the electric machine, and the speed derived therefrom;

FIG. 4 shows a speed curve of the internal combustion engine, in which several operating states of an internal combustion engine are traversed by way of example;

FIGS. 5 a, b show two exemplary operating states of the internal combustion engine which are determined by means of the method. FIG. 1 shows a control known from the prior art for regulating the voltage in a motor vehicle electrical system 10. The motor vehicle electrical system 10 is fed by means of an electric machine 14 coupled to an internal combustion engine 12, wherein the electric machine 14 is driven by the internal combustion engine 12 by means of a coupling element 16, typically a belt drive. For regulating the vehicle electrical system voltage 10, a computing unit 18 in the form of a regulator 20 is provided, which adjusts the excitation current of the electric machine in accordance with the vehicle electrical system voltage 10.

In order to be able to regulate the regulation or the feeding of electrical energy into the vehicle electrical system 10 as a function of the respective operating states of the internal combustion engine 12, the corresponding operating states of the internal combustion engine 12 are typically determined by a control device 22 assigned to the internal combustion engine 12, whereupon the control device 22 via a communication link 24 transmits control signals to the controller 20 to set an exciting current of the electric machine 14 corresponding to a respective operating state of the internal combustion engine 12. Here, the controller 20 of the electric machine 14 or a corresponding external to the electric machine 14 arranged computing unit (not shown) with respect to a determination of the respective operating conditions of the internal combustion engine 12 is always passive and only set up based on a control by the controller 22, the excitation current to increase or decrease the electric machine 14 according to the respective operating state.

FIG. 2 a) shows a schematic representation of a construction according to the invention of an internal combustion engine 112 and an electric machine 114 connected to the internal combustion engine 112, wherein the electric machine 114 is driven by the internal combustion engine 112 by means of a belt 116. The belt 116 is operatively connected to the crankshaft 117 of the internal combustion engine 112 on the engine side. The internal combustion engine 112 gives due to the Working cycles and / or the compression of the respective cylinder of the internal combustion engine 112, the torque pulses to the crankshaft 117 from. The frequency of the torque output is determined by the current speed of the engine 112 and the number of cylinders of the engine 112. In a four-stroke engine, the frequency of the torque output determined by the formula: fmoment = n _K w / 60 * ZyNnderzahl / 2, where nKw the speed of the internal combustion engine 112, and the crankshaft in

Revolutions per minute.

This non-uniform torque output generates a corresponding vibration behavior of the internal combustion engine 112. By the fixed coupling of the electric machine 114 with the internal combustion engine 112 through the coupling element 116 in the form of a belt or a rigid connection of the electric machine 114 and the internal combustion engine 112 (not shown) , the corresponding oscillation caused by the pulse-like torque output of the engine 112 is transmitted to the electric machine 114 and its rotational speed 122.

These oscillations can be deduced from the phase signal 120a (see FIG. 3) of the electric machine 114 as a result of the fixed coupling between the electric machine 114 and the internal combustion engine 112. The method according to the invention is described by means of a computing unit 118, on which the method is carried out. For control and evaluation, the electric machine 114 has the inventive calculation unit 118 in the form of a controller 120, which is set up to determine from the phase signal 121 a time profile of a rotational speed 122. The time profile of the rotational speed 122 is analyzed by the arithmetic unit 118, and a speed pattern 128, 132 (compare FIGS. 4 and 5) derived from the characteristic pulse-like vibrations of the internal combustion engine 112 is derived from the time profile of the rotational speed 122. In particular, the rotational speed patterns 128, 132 have characteristic oscillations O with corresponding amplitudes A and ripple W (compare FIGS. 4 and 5). In addition, the arithmetic unit 118 is designed to determine an average value DMD of the rotational speed 122, and to store this, if necessary, accordingly.

The mean value DMD of the rotational speed 122 is determined within a definable time interval, wherein the time interval for determining the mean value DMD of the rotational speed 122 should have a plurality of oscillations O, but at least one oscillation O. Furthermore, the amplitude A of the oscillation O or its ripple W can be determined. Amplitude A (see FIG. 5) is the absolute difference between the maximums of oscillation O and the mean value DMD of rotational speed 122, and ripple W is approximately twice the amplitude A. By comparing the mean value DMD of rotational speed 122 with a first threshold value Thi and comparing the ripple W, the time course of the mean value DMD of the rotational speed 122 superimposed oscillation O, with a speed band B, the operating states 128a and 132a of the internal combustion engine 112 can be determined. The operating states of the internal combustion engine here include the operating state partial load operation 128a and idle operation 132a. In order to determine the above-mentioned operating states, a further threshold value Thi2 can additionally be used for comparison with the mean value DMD of the rotational speed 122.

The arithmetic unit 118 in the form of a regulator 120 is thus set up, based on the mean value DMD of the rotational speed and the waviness W, of the oscillation O superposed on the time characteristic of the mean value DMD of the rotational speed when compared with a first threshold value Thi and / or second threshold value Thi2 and derived therefrom speed band B to determine the operating states 128a and 132a (see Figures 4 and 5), without the need for a corresponding external control unit is required. The electrical machine 114 or the computing unit 118 associated therewith is therefore configured to carry out the method steps described above and the method steps to be described below in a completely independent manner from an external analysis and / or external control unit. The thresholds Thi and Thi2 set the amount of speed band B, in which typically the ripple W of the oscillation O in the idling operation 132a runs. The idle operation 132a of the internal combustion engine 112 can thus be identified particularly simply by the fact that the mean value DMD of the rotational speed 122 is greater than the first threshold value Thi and smaller than the further threshold value Thi2, and that the waviness W extends within the rotational speed band B. Likewise, the non-idle operation mode, particularly partial load operation 128a of the engine 112, may be recognized. In partial load operation 128a, the average value DMD of the rotational speed 122 is greater than the first threshold value Thi, and the waviness W, the oscillation O superimposed on the time profile of the mean value DMD of the rotational speed 122, runs at least partially within the rotational speed band B and is greater in magnitude than the rotational speed band B.

Thus, by adjusting the mean value DMD of the speed 122 in a definable time interval, and the amplitude A or the ripple W of the rotational speed O 122 superimposed on the oscillation O with the speed band B, a safe and very simple determination of the respective operating conditions 128a and / or 132a , be effected.

In Figure 2b, another, similar to Figure 2a embodiment is described. Identical or comparable features to FIG. 2a have been identified by the same reference numerals but with a further letter (b). The electric machine 114b has a rotation speed sensor 115b connected to the electric machine. The rotation speed sensor 115b is fixed to the electric machine 114b so as to detect the rotation speed of the rotor of the electric machine 114b. The speed 122 determined by means of the speed sensor 115b can be used in the same way as the speed values 122 determined by means of a phase signal 121 in order to determine the operating states 128a and / or 132a of the internal combustion engine 112b. This results in an alternative reference source of the rotational speed signal 122, which can be used either alternatively or cumulatively for determining the rotational speed 122 from the phase signal 121.

FIG. 2c shows a further exemplary embodiment of the present invention. Identical or comparable features to FIGS. 2a and 2b have been identified by the same reference number but with a further letter c. Furthermore, it is simplified to assume that in the case of a cumulative determination of the rotational speed 122 by the phase signal 122 and the rotational speed sensor 115b (FIG. 2b), the respective operating state 128a and 132a is determined by the arithmetic unit 118c.

The arithmetic unit 118c, which is embodied in the form of a controller 120c of an electric machine 114c, is also configured to recognize the respective operating state 128a and / or 132a (see FIG. 5) and on the basis of the recognized operating state 128a and 132a of the internal combustion engine 112, to adapt an exciting current IE _IT to a respective operating state of the internal combustion engine 112 so that the braking torque of the electric machine 112 can be increased or decreased depending on the operating state. In the presently recognizable operating conditions, partial load operation 128a, or idle operation 132a, a reduction of the braking torque of the electric machine 114 and thus a reduction of the excitation current IE _IT is usually required to either the largest possible output torque of the internal combustion engine 112, or a To ensure trouble-free operation of the internal combustion engine 112 in idle operation.

In this case, the excitation current can be controlled by specifying a setpoint voltage Usoii or an Isoii of the motor vehicle electrical system 110c or by specifying a maximum current output i Max, the maximum current output _{ΙΜ 3Χ} can be parameterized according to operating conditions of the internal combustion engine 112.

By such a regulation of the exciter current \ E ", which is based on a specification of the setpoint voltage Usoii or of the setpoint current Isoii of the motor vehicle electrical system 110c If the idling or part-load operation 128a during acceleration operation of the internal combustion engine, an almost braking torque-free or drag torque-free traction of the electric machine 114a can be implemented correspondingly simply (see FIG. The same applies to a trouble-free operation of the internal combustion engine in the idling state 132a. Alternatively, such a regulation can also be regulated by means of a regulation of a maximum current ΙΜ _{3Χ to} be delivered to the motor vehicle vehicle network, whereby this maximum current ΙΜ _{3Χ can} in turn be parameterized as a function of the respective operating states 128a and 132a of the internal combustion engine 112 (see FIG. Such a parameterization can either take place numerically or be converted by querying the parameters stored in a stored map (not shown).

The determination of the rotational speed signal 122 from a phase signal 121 of the electric machine 114 is described in more detail in FIG. In the present case, the phase signal 121 is one of the phase voltages 121a of the electrical machine. It is understood that in principle any desired phase voltage of one or more phases of the electric machine 114, but also the respective phase currents can be used, to obtain therefrom the speed signal of the electric machine 114 as well as the speed signal and the speed patterns 128, 132 of the internal combustion engine 112 coupled thereto to be determined (not shown). When using more than one phase voltage, a correspondingly higher temporal resolution of the speed signal can be achieved (not shown).

The phase voltage 121a extends in a generator with current output in a first approximation rectangular. An average phase time T phase can be detected at this signal of the phase voltage 121a, which can best be determined on the steep edges of the phase voltage 121a. The phase time Tphase is modulated by the speed fluctuation in the form of a speed pattern 128, 132 characteristic of the respective operating states of the internal combustion engine 112 and maps the actual speed using the formula: n _KW = 60 / (TPHASE * PPZ * Üb), where rikw is the crankshaft speed in revolutions per minute, uv is the transmission ratio between crankshaft and generator shaft and PPZ is the number of pole pairs of the generator. The corresponding values of the rotational speed 122 and an average rotational speed 122a, which corresponds to the mean value DMD of the rotational speed 122 within a time interval, are also shown in FIG. 3 as points or as a line. The time interval can in particular be selected such that it is averaged over several oscillations.

The speed can preferably be determined digitally. By means of a measurement of the time intervals Tphase of the amplitudes in the phase signal 121 of the electric machine 114, as already described, the instantaneous speed ηκνν can be determined. If parameters such as number of cylinders, transmission ratio Ub and pole pair number PPZ of the electric machine 114 are known in the detected period, the controller 118 may store a fixed number of speed values in a memory, for example in a shift register (not shown) and at least within one oscillation cycle, respectively determine a maximum and a minimum instantaneous speed. The maximum and minimum instantaneous speeds are preferably the peak speeds in the respectively recorded time range. The difference between these speeds is a measure of the torque output by the engine 112. For accurate determination of phase T it is advantageous to ensure a high temporal resolution around the mean value of phase. In this case, for a better resolution, the rotational speed 122 can be determined on the basis of the rising and falling edges of the phase voltage 121a. In principle, any number of rpm values can be detected in the memory, although approximately one complete cycle of a vibration should be recorded for an evaluation.

In order to illustrate that the sampling rate of the generator is sufficient to correspondingly resolve the rotational speed 122 and in particular the oscillations superimposed on the rotational speed, the ratios of the respective frequencies are considered below and compared with the Nyquist criterion. The Nyquist criterion requires that f _e / fmoment> = 2. Related to the engine speed results in the generator frequency or the frequency of the electric machine with

where ηκνν is the speed of the internal combustion engine. In combination with the equation for fmoment, this results in fe / f moment- 2 * Ub * PPZ / number of cylinders.

Thus, for example, for U n = 3, PP Z = 6, number of cylinders = 4, the quotient f _e / f moment = 9 results. Even with very large high-cylinder engines, such as a 12-cylinder engine, the ratio is fe / fmoment = 3, where again the Nyquist sampling criterion is always met.

FIG. 4 shows the rotational speed curve 122 of an internal combustion engine 112 over a relatively long period of time. This rotational speed profile 122 has corresponding rotational speed patterns 128, 132, which are exemplary for two different operating states of an internal combustion engine 112, namely idle 132a and partial load operation 128a, characteristic. The respective rotational speed patterns 128 and 132 are shown enlarged again in FIGS. 5a and 5b. FIGS. 5a and 5b each show the rotational speed 122 over time.

FIG. 5 a shows the idling mode 132 a of the internal combustion engine 112. A characteristic of this operating state is that the mean value of the rotational speed DMD is essentially constant over time. In the present case, a speed band B is selected which is defined by a lower threshold value Thi and a threshold value Thi2. Within these threshold values, the rotational speed course 122 moves in the idle mode 132a, ie, the waviness W of the rotational speed curve 122 is within the rpm band B. The rotational speed band B, however, can also be determined in terms of absolute value by the threshold values Thi and Thi2 (see FIG. , The idle mode 132a of the engine 112 is then closed when the average value DMD of the rotational speed 122, greater than the first threshold Thi is, and is smaller than the further threshold Thi2, and / or the ripple W of the oscillation O, which corresponds approximately to twice the amplitude of the oscillation, is smaller in magnitude than the speed band B. ,

In FIG. 5b, the rotational speed signal 122 in the first time segment AI approximately has the rotational speed pattern 128a in the idle state 132a. The time range in which the mean value DMD of the rotational speed 122 has a substantially constant profile changes into a constantly increasing range in the second time interval A2. Again, the mean value DMD of the rotational speed, the oscillation O with a ripple Wieiiiast superimposed.

The speed band B is determined in terms of magnitude by the threshold values Thi and Thi2 (see FIG. 5a), this speed band B comprising the ripple Wi_eeriauf the oscillation O in the idle state 132a of the internal combustion engine 112. In the time range of the changing mean value DMD of the speed (transition from section AI to section A2 and the course of section A2), the speed band B is adjusted to the time rise of the mean value DMD of the speed 122 such that the mean value DMD of the speed 122 in runs approximately centrally in the speed band B and the gradient of the average DMD follows the speed 122. Thus, a partial load operation 128a of the internal combustion engine can be concluded when the mean value DMD of the rotational speed 122 is greater than the first threshold value Thi and / or greater than the further threshold value Thi2 and the waviness Wieiiiast, the time course of the mean value DMD of the rotational speed 122 overlaid oscillation O, at least partially runs within the speed band B and in terms of magnitude greater than the speed band B is.

It is characteristic that, given a torque output of the internal combustion engine 112, the amplitude A or the waviness W of the oscillation O, compared to the amplitude or ripple W in idle mode, increases. This can be used as a sufficient criterion for detecting a non-idle operation, for example, partial load operation 128a. As a necessary criterion for a partial load operation 128a, the exceeding of the threshold Thi can be used become. In addition, based on the above-described method for detecting a non-idling operation, a full-load operation could be detected accordingly, with the full load operation of a partial load operation in particular differs in that the amount of the amplitudes A and the ripple W in full load operation against the partial load operation accordingly increased.

Claims

claims

A method of determining an operating condition (128a, 132a) of an internal combustion engine (112), comprising the steps of:

a) determining the time profile of a rotational speed (122) of an electric machine (114) coupled to the internal combustion engine (112);

b) determining an average value (DMD) of the rotational speed (122) from the temporal

Course of the rotational speed (122) and determine at least one caused by the internal combustion engine (112) speed pattern (128, 132) from the time course of the rotational speed (122), the one of the time course of the mean value (DMD) of the rotational speed (122) superimposed on the oscillation (O); and

c) determining at least one operating state (128a, 132a) of the internal combustion engine (112) by comparing the mean value (DMD) of the rotational speed (122) with a first threshold (Thi) and comparing a ripple (W) of the time course of the mean value (DMD ) of the rotational speed (122) superimposed oscillation (O) with a speed band (B).

2. The method according to claim 1, characterized in that the speed band (B) in terms of magnitude by the first threshold (Thi) and another threshold (Thi2) is set, wherein the first threshold (Thi) and the further threshold (Thi2) a speed range in which an idling operation (132a) of the internal combustion engine (112) takes place.

3. The method according to claim 1 or 2, characterized in that the time profile of at least one phase signal (121) of an internal combustion engine (112) coupled electrical machine (114) is determined and the time course of the rotational speed (122) of the electric machine ( 114) from the

Phase signal (121) is determined.

4. The method according to claim 1 or 2, characterized in that the time profile of the rotational speed (122) of the electric machine (114) by means of a speed sensor (S) is determined.

5. The method according to any one of claims 1 to 4, characterized in that at least the operating state of the internal combustion engine (112) ignition of a fuel-air mixture (128a, 132a), in particular idling operation (132a) and / or non-idling operation, preferably partial load operation (128a ), is determined.

6. The method according to claim 5, characterized in that the idling operation (132a) of the internal combustion engine (112) is detected such that the average value (DMD) of the rotational speed (122) is greater than the first threshold value (Thi) and smaller than the other Threshold (Thi2), and the ripple (W) of the time course of the mean value (DMD) of the rotational speed (122) superimposed on the oscillation (O) within the speed band (B) and is smaller in magnitude than the speed band (B).

7. The method according to claim 5, characterized in that the non-idling operation (128a) of the internal combustion engine (112) is detected such that the average value (DMD) of the rotational speed (122) is greater than the first threshold value (Thi) and the ripple (W) of the temporal course of the mean value (DMD) of the rotational speed (122) superimposed oscillation (O) at least partially within the speed band (B) and in terms of magnitude greater than the speed band (B).

8. The method according to any one of the preceding claims, characterized in that at a changing average value (DMD) of the rotational speed (122) of the average value (DMD) of the rotational speed (122) substantially centrally in the speed band (B).

9. The method according to any one of claims 1 to 8, characterized by a further method step comprising the control of the exciter current (IE _IT ) the electric machine (114) in a respective operating state (128a, 132a) of the internal combustion engine (112) such that the braking torque of the electric machine (114) on the respective operating state (128a, 132a) is adjusted.

10. The method according to claim 9, characterized in that the excitation current (I Err) under specification of a nominal voltage (Usoii) and / or a desired current (Isoii) of the motor vehicle electrical system (110), or under specification of a maximum current output (iMax), wherein the maximum current output (ΙΜ _3Χ ) and / or the maximum excitation current preferably according to operating states (128a, 132a) of

Internal combustion engine (112) is parameterized, is regulated.

1 1. arithmetic unit (118), in particular controller (120) for an electrical machine (114), which is adapted by a corresponding integrated circuit and / or by a stored on a memory computer program to perform a method according to any one of the preceding claims.

12. Electrical machine (114), with a computing unit (118) according to claim 11.

A computer program that causes a computing unit to perform a method as claimed in any one of the preceding claims when executed on the computing unit (118).

14. Machine-readable storage medium with a stored on it

Computer program according to claim 13.