Monitoring deviations occurring in the valve drive of an internal combustion engine, and electronic engine control units for executing such methods

Abstract

Various embodiments include a method for detecting deviations occurring in the valve drive of an internal combustion engine comprising: measuring dynamic pressure oscillations of intake air in an air intake tract of respective internal combustion engine during operation; calculating an inlet valve stroke phase difference and/or an outlet valve stroke phase difference based on the measured dynamic pressure oscillation; calculating a valve stroke phase deviation value with respect to a valve stroke phase reference value based on the calculated phase difference; and calculating a first valve drive deviation value based on the valve stroke phase deviation value.

Claims

1. A method for detecting deviations occurring in a valve drive of an internal combustion engine, the method comprising: measuring dynamic pressure oscillations of intake air in an air intake tract of the internal combustion engine during operation; calculating an inlet valve stroke phase difference and/or an outlet valve stroke phase difference based on the measured dynamic pressure oscillation; calculating a valve stroke phase deviation value with respect to a valve stroke phase reference value based on the calculated inlet valve stroke phase difference and/or outlet valve stroke phase difference; noting a first valve drive deviation value equivalent to valve stroke phase deviation value; and based on the first valve drive deviation value, implementing one or more correction measures chosen from the group consisting of: adjusting an inlet camshaft adjustment angle, adjusting an outlet camshaft adjustment angle, adjusting an ignition timing, adjusting an injection quantity and starting an emergency operating mode and initiating an emergency stop of the internal combustion engine.

2. The method as claimed in claim 1, further comprising: measuring an inlet camshaft angle difference and/or an outlet camshaft angle difference using a crankshaft position sensor and an inlet camshaft position sensor and/or outlet camshaft position sensor during operation; calculating a second valve drive deviation value based on the measured inlet camshaft angle difference and/or outlet camshaft angle difference; comparing the first and the second valve drive deviation value with one another to perform a reciprocal plausibility check; and calculating a valve drive deviation comparison value.

3. The method as claimed in claim 2, wherein the first and/or the second valve drive deviation value is identified as plausible only if the valve drive deviation comparison value does not exceed a predefined valve drive deviation limit.

4. The method as claimed in claim 3, wherein: a control unit initiates control correction measures for the internal combustion engine and/or a fault message if the first and/or the second valve drive deviation values has been evaluated as plausible and does not exceed a predefined valve drive deviation limiting value; and the control unit initiates an emergency operating mode, emergency stop, and/or a fault message if the first and/or the second valve drive deviation value has been evaluated as plausible and exceeds the predefined valve drive deviation limiting value or a malfunction has already been previously detected associated with the valve drive.

5. The method as claimed in claim 4, further comprising continuously acquiring the first and/or the second valve drive deviation values during the operation of the internal combustion engine; and producing a respective deviation profile of the first and/or of the second valve drive deviation value over time, wherein specific causes of the deviations in the valve drive are detected based on the respective deviation profile.

6. The method as claimed in claim 3, further comprising, when there is a continuously rising value of the deviation, a wear-induced cause of the deviation in the valve drive is identified, which cause corresponds to at least one of: a lengthening of a chain, lengthening of a toothed belt, and/or wear of a gear wheel, and when there is a suddenly rising value of the deviation, a tooth-jump-induced cause of the deviation in the valve drive is identified.

7. The method as claimed in claim 2, further comprising identifying a malfunction during operation of the valve drive if the valve drive deviation comparison value exceeds a stipulated valve drive deviation comparison limiting value.

8. The method as claimed in claim 1, further comprising: in order to acquire the inlet valve stroke phase difference and/or the outlet valve stroke phase difference of the internal combustion engine during operation, generating a corresponding pressure oscillation signal based on the measured dynamic pressure oscillations; acquiring a crankshaft phase angle signal simultaneously with the measured dynamic pressure oscillations; calculating a phase position and/or amplitude of a selected signal frequency of the measured dynamic pressure oscillations in relation to the crankshaft phase angle signal based on the pressure oscillation signal using discrete Fourier transformation; acquiring, based on the acquired phase position and/or amplitude of the respective selected signal frequency, in each case as a function of lines of an equal phase position and/or of equal amplitude of the selected signal frequency, the lines depending on the inlet valve stroke phase difference and the outlet valve stroke phase difference, using reference lines of the equal phase position and/or of the equal amplitude of the same-signal frequency; calculating a respective common intersection point of lines of the equal phase position and/or equal amplitude; and determining the inlet valve stroke phase difference and/or the outlet valve stroke phase difference based on the acquired common intersection point.

9. The method as claimed in claim 1, wherein the method is executed on an electronic computing unit assigned to an electronic, programmable engine control unit of the internal combustion engine.

10. An electronic, programmable engine control unit for controlling an internal combustion engine, the engine control unit comprising: a processor; and an electronic memory unit storing a set of instructions, the instructions, when loaded and executed by the processor, causing the processor to: measure dynamic pressure oscillations of intake air in an air intake tract of the internal combustion engine during operation; calculate an inlet valve stroke phase difference and/or an outlet valve stroke phase difference based on the measured dynamic pressure oscillation; calculate a valve stroke phase deviation value with respect to a valve stroke phase reference value based on the calculated inlet valve stroke phase difference and/or the calculated outlet valve stroke difference; note a first valve drive deviation value equivalent to the valve stroke phase deviation value; and based on the first valve drive deviation value, implementing one or more correction measures chosen from the group consisting of: adjusting an inlet camshaft adjustment angle, adjusting an outlet camshaft adjustment angle, adjusting an ignition timing, adjusting an injection quantity and starting an emergency operating mode and initiating an emergency stop of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The exemplary embodiments and developments of the subject matter described in the present disclosure are explained below with reference to the figures, in which respect:

(2) FIG. 1: shows a simplified schematic drawing of a reciprocating-piston internal combustion engine;

(3) FIG. 2: shows the schematic drawing as per FIG. 1, with labeling of the possible position and angle deviations of significant components of the reciprocating-piston internal combustion engine;

(4) FIG. 3: shows a simplified illustration of the method sequence incorporating teachings of the present disclosure, in a block diagram illustration;

(5) FIG. 4: shows a two-dimensional diagram for the exemplary illustration of the profile of different valve drive deviation values over the operating duration of an internal combustion engine with a plotted valve drive deviation limiting value; and

(6) FIG. 5: shows a two-dimensional diagram for the exemplary illustration of the profile of a valve drive deviation difference value over the operating duration of an internal combustion engine with a plotted valve drive deviation difference limiting value.

(7) Parts which are identical in terms of function and designation are denoted by the same reference signs throughout the figures.

DETAILED DESCRIPTION

(8) For optimum operation of the internal combustion engine (with regard to emissions, consumption, power, running smoothness etc.), the fresh-gas charge introduced into the combustion chamber during the intake stroke should be known to the best possible extent in order to enable the further parameters for the combustion, such as for example the fuel quantity which is to be supplied, and which is possibly directly injected, to be coordinated therewith. The so-called charge exchange, that is to say the intake of fresh gas and the discharge of the exhaust gas, is in this case highly dependent on the control timing of the inlet valves 22 and outlet valves 32, that is to say on the profile with respect to time of the respective valve strokes in relation to the profile with respect to time of the piston stroke. In other words, during operation, the charge exchange is dependent on the phase positions of the inlet and outlet valves in relation to the crankshaft phase angle and thus in relation to the phase position of the reciprocating piston.

(9) The prior art for acquiring the fresh-gas charge and for coordinating the control parameters of the internal combustion engine therewith comprises measuring a so-called reference internal combustion engine in all occurring operating states, for example as a function of the rotational speed, the load, if appropriate of the valve control timings predefinable by means of phase adjusters, if appropriate the operating parameters of exhaust-gas turbocharger or supercharger etc., and storing these measurement values or derivatives thereof or model approaches representing the behavior on the engine control unit of a corresponding series-production internal combustion engine. All structurally identical, series-produced internal combustion engines of the same type series are then operated with this reference dataset that is generated.

(10) A deviation, resulting for example from manufacturing tolerances or wear, of the actual relative positions between inlet valves and outlet valves and the crankshaft phase angle or the reciprocating-piston position of a series-production internal combustion engine in relation to the ideal reference positions of the reference internal combustion engine, that is to say a phase difference of the inlet valve stroke and of the outlet valve stroke in relation to the crankshaft phase angle, predefined by the crankshaft position sensor, or the phase position of the crankshaft and therefore the piston stroke, has the effect that the fresh-gas charge actually drawn in deviates from the fresh-gas charge determined as a reference, and thus the control parameters based on the reference dataset are not optimum. During the operation of the internal combustion engine, these errors can have adverse effects with regard to emissions, consumption, power, running smoothness etc.

(11) For the illustration of the possible deviations that occur in a series-production internal combustion engine, and for the definition of the nomenclature of said deviations, reference will be made below to FIG. 2, which shows the internal combustion engine from FIG. 1 but in which, for a better overview, the reference designations illustrated in FIG. 1 have been omitted and only the corresponding deviations are designated. Proceeding from a reference position of the position encoder 43 arranged on the crankshaft control adapter 10, the phase angle of which position encoder is detected by the crankshaft position sensor 41, there are resulting multiple tolerance chains that lead to deviations of the phase positions, hereinafter also referred to as phase differences, of reciprocating pistons 6, inlet valves 22 and outlet valves 32 in relation to the ideal reference phase positions.

(12) Here, the piston stroke phase difference ΔKH results for example from a deviation of the crankpin angle HZW, the so-called crankpin angle difference ΔHZW, in relation to the reference position of the crankshaft position sensor 41 and from different dimensional tolerances (not illustrated) of connecting rod 7 and reciprocating piston 6. Furthermore, the inlet valve stroke phase difference ΔEVH results for example from a deviation in the cam position, the so-called inlet camshaft angle difference ΔENW, owing to mechanical tolerances or deformations (not illustrated) of the camshaft itself, of the inlet camshaft control adapter 24 and of the control mechanism 40. If a phase adjuster for the inlet camshaft is present, then consideration is possibly also given to an inlet camshaft adjustment angle ENVW or to a deviation thereof from the setpoint.

(13) In the same way, the outlet valve stroke phase difference ΔAVH results for example from a deviation in the cam position, the so-called outlet camshaft angle difference ΔANW, owing to mechanical tolerances or deformations (not illustrated) of the camshaft itself, of the outlet camshaft control adapter 24 and of the control mechanism 40. If a phase adjuster for the outlet camshaft is present, then consideration is possibly also given to an outlet camshaft adjustment angle ANVW or to a deviation thereof from the setpoint.

(14) Deviations in the form of the inlet camshaft angle difference ΔENW and the outlet camshaft angle difference ΔANW frequently occur owing to wear phenomena such as, for example, the lengthening of control chains or toothed belts which occurs during operation, and the wear of the chain wheels or belt wheels or else gear wheels. In this context, in an unfavorable case entire tooth jumps, this is so the slipping through of the control chain or of the toothed belt by one tooth or even a plurality of teeth, can occur. Such deviations cannot be sensed and corrected, as for example, can manufacturing-induced mechanical tolerances, by one-off measurement of the internal combustion engine before it is put into service, since they only occur during operation and, under certain circumstances, change in a continuously gradual fashion.

(15) In order to counteract this problematic situation, most currently known systems operate with a reference point system (position encoder feedback). Here, in each case one position encoder as a position mark which can be sensed by means of a sensor is placed on the crankshaft and on the inlet camshaft and/or on the outlet camshaft, or also on the respective crankshaft control adapter and on the inlet camshaft control adapter and/or on the outlet camshaft control adapter, or also on a phase adjuster that may be provided, etc. As a result, the relative phase position of the respective inlet camshaft and/or outlet camshaft with respect to the position of the crankshaft can be acquired, and deviations from the aimed—at reference values can be identified. The undesired effects of said deviations can then be counteracted in the control unit by means of an adaptation or correction of corresponding control parameters in a manner dependent on the acquired deviations.

(16) Corresponding methods are taught, for example, in documents DE 195 03 457 C1, EP 1 915 516 B1, and FR 2 850 755 B1. On the other hand, in the patent applications DE 10 2015 209 665.3, DE 10 2015 222 408.2, DE 10 2016 219 584.0, and DE 10 2016 219 582.4 which are still unpublished, various methods are presented which permit the inlet valve stroke phase difference, the outlet valve stroke phase difference and the piston stroke phase difference to be acquired during operation on the basis of dynamic pressure oscillations, the intake air in the intake tract of the respective internal combustion engine, independently of corresponding position encoders and position sensors on the camshafts.

(17) In this context, during the operation of the internal combustion engine the dynamic pressure oscillations, which can be assigned to the respective cylinder, in the air intake tract are measured and the corresponding pressure oscillation signal is generated therefrom. A crankshaft phase angle signal is acquired at the same time. The phase position and/or the amplitude of at least one selected signal frequency of the measured pressure oscillations in relation to the crankshaft phase angle signal are acquired from the pressure oscillation signal using discrete Fourier transformation.

(18) Then, on the basis of the acquired phase positions and/or amplitudes of the respective selected signal frequencies, lines of an equal phase position and of equal amplitude of the respectively same signal frequency are acquired using reference lines of the equal phase position and of the equal amplitude of the respective signal frequency, which reference lines are stored in reference line characteristic diagrams or acquired by means of a respective algebraic model function. Then, the inlet valve stroke phase difference and the outlet valve stroke phase difference and, if appropriate, the piston stroke phase difference are determined from the acquired common intersection point of the lines of equal phase positions and of the lines of equal amplitudes of the respective signal frequencies.

(19) A person skilled in the art will include all components that serve for the supply of air to the respective combustion chambers of the cylinders, and which thus define the so-called air path, under the term “air intake tract” or also simply “intake tract”, “intake system” or “inlet tract” of an internal combustion engine. These terms may include, for example, an air filter, an intake pipe, an intake manifold or distributor pipe or, for short, suction pipe, a throttle flap valve, as well as, if appropriate, a compressor and the intake opening in the cylinder and/or the inlet duct of the cylinder.

(20) For the analysis of the pressure oscillation signal, the latter is subjected to a discrete Fourier transformation (DFT). For this purpose, an algorithm known as a fast Fourier transformation (FFT) may be used for the efficient calculation of the DFT. By means of DFT, the pressure oscillation signal is now broken down into individual signal frequencies which can thereafter be separately analyzed in simplified fashion with regard to their amplitude and the phase position.

(21) It has been found that both the phase position and the amplitude of selected signal frequencies of the pressure oscillation signal are dependent on the valve control timings, that is to say on the phase profiles of the inlet valve stroke, of the outlet valve stroke and of the piston stroke of the internal combustion engine. The phase position of a signal frequency characterizes here the relative position of the signal frequency signal in relation to the crankshaft rotational angle signal, and the amplitude is a measure of the amount of deflection of the signal frequency signal in relation to a center line.

(22) Ever stricter legal requirements in respect of the operational safety of an internal combustion engine, in particular with respect to the exhaust gas emissions which are caused, require the actual sensor data and operating data which are obtained and used for the corresponding control of the internal combustion engine, to be continuously monitored during ongoing operation and for their plausibility to be checked within the scope of self-diagnostics and for their susceptibility to errors to be checked. With respect to the deviations which occur in the valve drive of an internal combustion engine and are sensed with the above-mentioned methods known from the prior art, this has previously not been possible, since a correspondingly redundant value for plausibility checking was not available in the past.

(23) The teachings of the present disclosure describe methods and engine control units with which a valve drive deviation value which is comparable with a conventionally acquired valve drive deviation value can be made available as far as possible without additional expenditure on technical equipment, with the result that the two valve drive deviation values can be used for reciprocal plausibility checking.

(24) In some embodiments, the method for detecting deviations occurring in the valve drive of an internal combustion engine is characterized in that an inlet valve stroke phase difference and/or an outlet valve stroke phase difference are acquired by means of analysis of dynamic pressure oscillations of the intake air in the air intake tract of the respective internal combustion engine during operation, and a valve stroke phase deviation value with respect to a valve stroke phase reference value is acquired therefrom, wherein a first valve drive deviation value is acquired on the basis of the valve stroke phase deviation value.

(25) In some embodiments, the inlet valve stroke phase difference and/or an outlet valve stroke phase difference are acquired directly, but between the crankshaft and the inlet valves and outlet valves there are, apart from the valve drive, also further transmission components, such as for example the cams of the camshaft itself or the connection between the camshaft and the respective camshaft control adapter, the valve drive deviation value does not correspond directly to the acquired inlet valve stroke phase difference and/or the outlet valve stroke phase difference. Therefore, for example at the initial putting into service there is already an inlet valve stroke phase difference and/or an outlet valve stroke phase difference, whereas with respect to the valve drive it is assumed that when the first putting into service occurs the valve drive is adjusted into the setpoint position and firstly does not have a deviation. A valve drive deviation value occurs with respect to the adjusted initial setpoint position as a reference value, only in the course of the continuing operation. Accordingly, the inlet valve stroke phase difference and/or outlet valve stroke phase difference which are determined at the first putting into service are also acquired and stored as valve stroke phase reference values, to which reference is made in all the further measurements. The difference between the respective currently acquired inlet valve stroke phase difference and/or the outlet valve stroke phase difference and the associated valve stroke phase reference value results in a valve stroke phase deviation value on the basis of which the valve drive deviation value can be acquired, for example using the transmission ratio of the valve drive.

(26) In some embodiments, an electronic, programmable engine control unit for controlling an internal combustion engine has an assigned electronic computing unit and an assigned electronic memory unit and is characterized in that the electronic computing unit and the electronic memory unit are configured, inter alia, to execute a method as described above and to correspondingly control the internal combustion engine by means of the engine control unit. For this purpose, for example a corresponding program algorithm and the necessary reference values are stored in the electronic memory unit and then called for execution by means of the electronic computing unit.

(27) The methods and the engine control units described herein have the advantage that without an additional sensor system and particular expenditure on technical equipment a valve drive deviation value can be acquired independently of position encoders and position sensors which are assigned to the valve drive, thereby providing means for performing plausibility checking of the valve drive deviation value. The schematic illustration of a reciprocating piston internal combustion engine 1 which is shown in FIGS. 1 and 2, with the functional components which are decisive with respect to the subject matter of this patent application, and the possible deviations which occur, and for the purpose of defining the designation of these deviations, has already been explained.

(28) FIG. 3 shows a simplified, schematic block diagram for the exemplary illustration of a method sequence incorporating teachings of the present disclosure. In the region of the diagram which is surrounded by the box 100, the method for the detection of deviations occurring in the valve drive of an internal combustion engine is summarized. In some embodiments, the method is characterized in that firstly an inlet valve stroke phase difference ΔEVH and/or an outlet valve stroke phase difference ΔAVH are acquired by means of analysis of dynamic pressure oscillations of the intake air in the air intake tract 20 of the respective internal combustion engine 1 during operation.

(29) For example an inlet valve stroke phase reference value ΔEVH_Ref or an outlet valve stroke phase reference value ΔAVH_Ref, a valve stroke phase deviation value VhP_Aww, with respect to an assigned valve stroke phase reference value ΔVH_Ref, is then acquired from the inlet valve stroke phase difference ΔEVH or from the outlet valve stroke phase difference ΔAVH, or from both values together, for example by forming mean values ((ΔEVH+ΔAVH)/2). This can be done, for example, easily by forming differences in accordance with
VhP_Aww=ΔEVH−ΔEVH_Ref or
VhP_Aww=ΔAVH−ΔAVH_Ref or
VhP_Aww=((ΔEVH+ΔAVH)/2)−ΔVH_Ref

(30) The corresponding valve stroke phase reference values ΔVH_Ref, ΔEVH_Ref, ΔAVH_Ref are, for example, values which were acquired when the internal combustion engine was first put into service and are stored in an electronic memory unit of the engine control unit of the internal combustion engine.

(31) Subsequent to this, a first valve drive deviation value VT_Aww_1 may then be acquired on the basis of the valve stroke phase deviation value VhP_Aww. This can be done, for example, by using the transmission ratios between the inlet valves 22 or outlet valves 32 and the crankshaft 9. In order to acquire the inlet valve stroke phase difference ΔEVH and/or an outlet valve stroke phase difference ΔAVH, it is possible, in some embodiments, to use, for example, one of the methods from Applicant's patent applications DE 10 2015 209 665.3, DE 10 2015 222 408.2, DE 10 2016 219 584.0, and DE 10 2016 219 582.4. The presented methods make it possible to acquire the inlet valve stroke phase difference ΔEVH, the outlet valve stroke phase difference ΔAVH and the piston stroke phase difference ΔKH on the basis of dynamic pressure oscillations of the intake air in the air intake tract of the respective internal combustion engine, independently of corresponding position encoders 43 and position sensors 42 at the camshafts during operation.

(32) In this context, for example during the operation of the internal combustion engine, the dynamic pressure oscillations, which can be assigned to the respective cylinder, in the air intake tract 20 are measured and the corresponding pressure oscillation signal is generated therefrom. A crankshaft phase angle signal is acquired at the same time. The phase position and/or the amplitude of at least one selected signal frequency of the measured pressure oscillations in relation to the crankshaft phase angle signal are acquired from the pressure oscillation signal using discrete Fourier transformation.

(33) Then, on the basis of the acquired phase positions and/or amplitudes of the respective selected signal frequencies, lines of an equal phase position and/or of equal amplitude of the respectively same signal frequency are acquired using reference lines of the equal phase position and of the equal amplitude of the respective signal frequency, which reference lines are stored in reference line characteristic diagrams or acquired by means of a respective algebraic model function. Then, the inlet valve stroke phase difference and the outlet valve stroke phase difference and, if appropriate, the piston stroke phase difference are determined from the acquired common intersection point of the lines of equal phase positions and/or of the lines of equal amplitudes of the respective signal frequencies.

(34) A person skilled in the art will include all components that serve for the supply of air to the respective combustion chambers of the cylinders, and which thus define the so-called air path, under the term “air intake tract” or also simply “intake tract”, “intake system” or “inlet tract” of an internal combustion engine. These terms may include, for example, an air filter, an intake pipe, an intake manifold or distributor pipe or, for short, suction pipe, a throttle flap valve, as well as, if appropriate, a compressor and the intake opening in the cylinder and/or the inlet duct of the cylinder.

(35) For the analysis of the pressure oscillation signal, the latter is subjected to a discrete Fourier transformation (DFT). For this purpose, an algorithm known as a fast Fourier transformation (FFT) may be used for the efficient calculation of the DFT. By means of DFT, the pressure oscillation signal is now broken down into individual signal frequencies which can thereafter be separately analyzed in simplified fashion with regard to their amplitude and the phase position.

(36) In some embodiments, both the phase position and the amplitude of selected signal frequencies of the pressure oscillation signal are dependent on the valve control timings, that is to say on the phase profiles of the inlet valve stroke, of the outlet valve stroke and of the piston stroke of the internal combustion engine. The phase position of a signal frequency characterizes here the relative position of the signal frequency signal in relation to the crankshaft rotational angle signal, and the amplitude is a measure of the amount of deflection of the signal frequency signal in relation to a center line.

(37) In some embodiments, as shown in the region of the diagram in FIG. 3 which is surrounded by the box 200, an inlet cam shaft angle difference ΔENW and/or an outlet cam shaft angle difference ΔANW are/is additionally acquired by means of an arrangement of a crankshaft position sensor 41 and an inlet camshaft position sensor 42a and/or an outlet camshaft position sensor during 42b during operation, and a second valve drive deviation value VT_Aww_2 is acquired therefrom. The second valve drive deviation value VT_Aww_2 and the first valve drive deviation value, preferably acquired in parallel in chronological terms, VT_Aww_1 then compared with one another for the purpose of reciprocal plausibility checking, wherein a valve drive deviation comparison value (ΔVT_Aww) is formed. Plausibility checking of the valve drive deviation value can be performed easily and without additional expenditure on technical equipment, since only the signals of the sensor components, in particular pressure sensors and position sensors, which are present in any case, are evaluated in the way described.

(38) For example, as illustrated in FIG. 3, in a procedure analogous to the acquisition of the first valve drive deviation value (VT_Aww_1), the method may include acquiring a camshaft angle deviation value NwW_Aww, in relation to an inlet camshaft angle reference value ΔENW-Ref, an outlet camshaft angle reference value ΔANW-Ref or a common camshaft angle reference value ΔNW-Ref, from the inlet camshaft angle difference ΔENW and/or the outlet camshaft angle difference ΔANW. In this context, the inlet camshaft angle difference ΔENW and the outlet camshaft angle difference ΔANW can also be considered separately or in combination, for example by forming mean values ((ΔENW+ΔANW)/2). This can be done, for example, easily by forming differences in accordance with:
NwW_Aww=ΔENW−ΔENW_Ref or
NwW_Aww=ΔANW−ΔANW_Ref or
NwW_Aww=((ΔENW+ΔANW)/2)−AVH_Ref

(39) The corresponding camshaft angle reference values ΔNW-Ref, ΔENW_Ref, ΔANW_Ref are, for example values which were acquired when the internal combustion engine was first put into service and are stored in an electronic memory unit of the engine control unit of the internal combustion engine. The second valve drive deviation value (VT_Aww_2) is then acquired on the basis of the camshaft angle deviation value NwW_Aww, e.g. using the mechanical transmission ratios and, if appropriate, the angle position of phase adjusters.

(40) FIG. 4 shows in this respect various profiles of valve drive deviation values VT_Aww over the service life of the internal combustion engine. A profile of a first valve drive deviation value which is denoted by VT_Aww_1 and a profile of a second valve drive deviation value which is denoted by VT_Aww_2 are illustrated. Both profiles show a slowly continuous rise in the respective valve drive deviation value, wherein the second valve drive deviation value VT_Aww_2 rises more strongly than the first valve drive deviation value VT_Aww_1. The acquisition of the valve drive deviation comparison value ΔVT_Aww at a time T1 is plotted as an interval or difference between the valve drive deviation values VT_Aww_1 and VT_Aww_2.

(41) Such a continuous profile of the valve drive deviation values characterises, for example, continuously increasing wear of the transmission elements. In order to illustrate another cause of a deviation in the valve drive, a curve denoted by VT_Aww_X is plotted. Said curve shows, at a time TX, a sudden rise in the valve drive deviation value VT_Aww_X, such as would occur, for example, in the case of a tooth jump of a toothed belt, that is to say when the toothed belt slips by one or more teeth on the toothed belt wheel.

(42) In some embodiments, in conjunction with the reciprocal plausibility checking of the valve drive deviation values VT_Aww_1 and VT_Aww_2, and the formation of a valve drive deviation comparison value ΔVT_Aww, the first and/or the second valve drive deviation values VT_Aww_1 and VT_Aww_2 are evaluated as plausible as long as the valve drive deviation comparison value ΔVT_Aww does not exceed a defined valve drive deviation comparison limiting value ΔVT_Aww_Gw. This procedure is illustrated by the sequence steps 301 and 302 in the block diagram in FIG. 3. In the sequence step 301, the acquired valve drive deviation comparison value ΔVT_Aww is checked to determine whether it is lower or higher than a predefined, previously stipulated valve drive deviation comparison limiting value ΔVT_Aww_Gw. If the valve drive deviation comparison value ΔVT_Aww is lower, the acquired valve drive deviation values in the sequence step 302 are evaluated as plausible VT_Aww=ok and can be used as an input variable for corresponding control algorithms of the internal combustion engine. This ensures a type of self-diagnosis which increases the fault-free operational reliability of the internal combustion engine. This relationship is also illustrated in the diagram in FIG. 5. Here, an example of a profile of the valve drive deviation comparison value ΔVT_Aww is illustrated over the service life of the internal combustion engine and shows a continuously rising profile of the valve drive deviation comparison value ΔVT_Aww. The valve drive deviation comparison limiting value ΔVT_Aww_Gw is also plotted. As long as the valve drive deviation comparison value ΔVT_Aww is below the ΔVT_Aww_Gw, the underlying valve drive deviation value VT_Aww is evaluated as OK, that is to say as plausible.

(43) In some embodiments, in conjunction with the reciprocal plausibility checking of the valve drive deviation values VT_Aww_1 and VT_Aww_2 and the formation of a valve drive deviation comparison value ΔVT_Aww, a malfunction VT_Ffkt is detected in the region of the valve drive as soon as the valve drive deviation comparison value ΔVT_Aww exceeds a stipulated valve drive deviation comparison limiting value ΔVT_Aww_Gw at least once. This is symbolized in FIG. 3 by the sequence steps 301 and 303 as well as in FIG. 5 by the region above the valve drive deviation comparison limiting value ΔVT_Aww_Gw. In this way, a serious malfunction of the valve drive can be reliably detected and, if appropriate, measures can be taken to prevent even greater damage. Such a malfunction can be caused, for example, by a defect or incorrect positioning of the inlet camshaft position sensor, of the outlet camshaft position sensor or of the crankshaft position sensor, as well as by a defect or a malfunction of a phase adjuster of the inlet camshaft or of the outlet camshaft. Of course, in such a case, initially a plurality of measurements can be performed successively in order to confirm the detected malfunction, and therefore to debounce the detection of a malfunction, and to take measures, such as for example an emergency operating mode or even deactivation of the internal combustion engine, when the result is unambiguously confirmed.

(44) In some embodiments, compensating control correction measures Ktr_Mβn for controlling the internal combustion engine 1 and/or a fault message Info_Sig are brought about by means of a control unit 50 of the internal combustion engine 1 as long as the first and/or the second valve drive deviation values VT_Aww_1, VT_Aww_2 have been evaluated as plausible and do not exceed a predefined valve drive deviation limiting value, VT_Aww_Gw. This is illustrated symbolically in FIG. 3 by the sequence steps 302, 304, 305 and 308. For example, the correction measures Ktr_Mβn here can relate, inter alia, to the adaptation of the inlet camshaft adjustment angle ENVW and of the outlet camshaft adjustment angle ANVW by means of the phase adjuster, and to the adaptation of the ignition time, of the start of injection and of the injection quantity.

(45) However, if the first and/or the second valve drive deviation values VT_Aww_1, VT_Aww_2 exceed a predefined valve drive deviation limiting value VT_Aww_Gw or a malfunction VT_Ffkt has already previously been detected in the region of the valve drive, an emergency operating mode Nt_Btb or an emergency stop Nt_stop and/or a fault message Info_Sig of the internal combustion engine 1 is brought about by means of a control unit 50 of the internal combustion engine 1. In this way, it is possible to react to various conditions in a way which is respectively adapted to an optimum degree, in order to ensure optimum operation of the internal combustion engine 1. This sequence is illustrated symbolically in FIG. 3 on the basis of the sequence steps 302, 304, 306, 307 and 308. In FIG. 4, the checking of the valve drive deviation values VT_Aww_1, VT_Aww_2 or VT_Aww_X in relation to a valve drive deviation limiting value VT_Aww_Gw is also illustrated, wherein below the valve drive deviation limiting value VT_Aww_Gw correction measures Ktr_Mβn are initiated and above the valve drive deviation limiting value VT_Aww_Gw an emergency operating mode Nt_Btb or an emergency stop Nt_Stop is initiated.

(46) In some embodiments, the first and/or the second valve drive deviation values VT_Aww_1, VT_Aww_2 are acquired continuously during the operation of the internal combustion engine, and a respective deviation profile of the first and/or of the second valve drive deviation values VT_Aww_1, VT_Aww_2 is produced over time, as is also illustrated in FIG. 4. However, in this context, the focus is no longer on a result at a specific time but rather specific causes of the deviations in the valve drive are detected on the basis of the respective deviation profile. A typical example of this is the profile VT_Aww_X shown in FIG. 4, in which the profile makes it possible to detect a tooth jump. In this way, specific malfunctions can be advantageously identified and they can be a reaction thereto in an appropriate way during operation or the type of malfunction is recorded in a fault memory and can be used for diagnostic purposes during repair.

(47) In this way, when there is a continuously rising value of the deviation profile a wear-induced cause of the deviation in the valve drive can be detected, which cause corresponds, depending on the embodiment of the valve drive, to lengthening of the chain, lengthening of a toothed belt or to wear of a gear wheel, and when there is a suddenly rising value of the deviation profile it is also possible to detect a tooth-jump-induced cause of the deviation in the valve drive. Furthermore, the example methods permit the magnitude of the deviation in the valve drive, that is to say, for example, a value for the lengthening of a chain, to be determined on the basis of the magnitude of a current deviation value of the valve drive.

(48) If a valve drive has phase adjusters, a respective current phase adjustment value can, of course, also be included in the acquisition of the first deviation value of the valve drive. In this case, the possibility also arises of acquiring a deviation difference, between a current valve drive deviation value VT_Aww_E acquired on the basis of the inlet valve stroke phase difference ΔEVH and a further current valve drive deviation value VT_Aww_A acquired on the basis of the outlet valve stroke phase difference ΔAVH, and a defect in one of the phase adjusters is detected if the difference between the two valve drive deviation values exceeds a stipulated limiting value.

(49) In some embodiments, the example method may be, if appropriate, implemented with the inclusion of all the embodiments and developments described above, on an electronic computer unit 53 which is assigned to an electronic programmable engine control unit 50 of the internal combustion engine 1 and is functionally connected thereto.