Method for operating an internal combustion engine with exhaust valve lift control and motor vehicle

Abstract

Method for operating an internal combustion engine (12) which has a knock sensor (24) for detecting uncontrolled combustion and a valve lift control (20, 22) for an exhaust valve (18) of a cylinder (14) which is configured to switch the valve lift of the exhaust valve (18), wherein automatically - for overrun operation by means of the valve lift control (20, 22) the valve lift of the exhaust valve (18) is deactivated, - a signal received by the knock sensor (24) is evaluated with regard to a predefined criterion for detecting a malfunction of the valve lift control (20, 22), and - in response to such a detected fault, a predetermined control measure relating to the valve lift control (20, 22) is executed - at least as part of the control measure, the deactivation of the valve lift for at least one subsequent overrun operation is only switched off when at least a predetermined number and / or at least a predetermined temporal and / or temporal density of fault switching related to a number of separate overrun operating times has been detected.

Description

[0001] The present invention relates to a method for operating an internal combustion engine and to a correspondingly equipped and furnished motor vehicle.

[0002] Even though internal combustion engines have been around for a long time, there is still interest in and a need for further development, for example regarding efficiency or reliability. One well-known approach to improving internal combustion engines is variable valve lift control. However, such mechanisms can in turn lead to further problems in the operation of the respective internal combustion engine.

[0003] Against this background, a diagnostic system for a discrete variable valve lift system of an internal combustion engine is described in DE 10 2007 053 783 B4. The diagnostic system described therein comprises a Fast Fourier Transform module (FFT module) that generates a frequency content signal based on an FFT method and a valve impulse sensor signal. Furthermore, the diagnostic system includes a fault detection module that selectively diagnoses a malfunction of a discrete variable valve lift system based on the frequency content signal. The fault detection module sets a fault signal based on a frequency range derived from the engine speed.

[0004] German patent DE 10 2004 013 767 A1 describes a method for diagnosing the functionality of a valve lift control system in an internal combustion engine. The method uses a characteristic map to define the relationship between a valve lift setting and a corresponding ignition angle, so that adjusting the valve lift results in a corresponding adjustment of the ignition angle. For each associated valve lift-ignition angle setting, a structure-borne sound frequency of the internal combustion engine, present during normal operation of the valve lift control system, is determined. This frequency, along with the characteristic map, is stored as a target frequency in a control unit of the internal combustion engine. The control unit compares the actual frequency of the structure-borne sound from the internal combustion engine, determined by a sensor, with the target frequency assigned to the controlled valve lift-ignition angle setting.If the actual frequency deviates from the target frequency, an error message is issued, indicating a malfunction of the valve stroke adjustment.

[0005] DE 11 2014 004 271 T5 describes a method for controlling the operation of an internal combustion engine. The method includes instructing the engine to operate in intermittently and determining whether an exhaust valve actuation fault has occurred, in which the exhaust valve assigned to a selected cylinder does not open correctly during a selected operating cycle. If an exhaust valve actuation fault is detected, the intake valve assigned to the selected cylinder is deactivated during a subsequent operating cycle in which the intake valve would otherwise have been actuated, in response to the detection of the exhaust valve actuation fault.

[0006] Another approach described in DE 10 2014 118 587 A1 involves a method for ignition advance control of a power engine. In response to at least partial combustion or a misfire in a first cylinder, a spark ignition for a second cylinder, which receives exhaust gas residue from the combustion in the first cylinder, is selectively deactivated. This is ultimately intended to enable the adjustment of the spark and / or fuel injection in a cylinder based on late combustion, partial combustion, or a misfire in an adjacent cylinder.

[0007] The object of the present invention is to enable a particularly reliable operation of an internal combustion engine.

[0008] This problem is solved according to the invention by the subject matter of the independent claims. Possible embodiments and further developments of the present invention are specified in the dependent claims, in the description, and in the drawings.

[0009] The method according to the invention serves to operate or control an internal combustion engine, for example, a motor vehicle. The method is applied to an internal combustion engine that has a knock sensor for detecting uncontrolled combustion in a cylinder of the engine and a valve lift control for at least one exhaust valve of at least one cylinder, in particular for all exhaust valves of all cylinders of the engine. The valve lift control is configured to switch the valve lift of the at least one exhaust valve, i.e., to activate and deactivate its valve lift in a controlled manner.

[0010] With the valve lift activated, the exhaust valve can regularly and alternately open and close the exhaust side of the respective cylinder in the manner known from conventional internal combustion engines without valve lift control or variable valve timing. With the valve lift deactivated, however, the respective exhaust valve remains in a single position, specifically its closed position, which closes the exhaust side of the respective cylinder, particularly over several revolutions of the engine's crankshaft, i.e., over several piston cycles within the respective cylinder. Therefore, with the valve lift deactivated, a charge exchange in the respective cylinder can be prevented.

[0011] In one step of the inventive process, the valve lift of at least one exhaust valve is deactivated by means of the valve lift control for overrun operation of the internal combustion engine or a motor vehicle equipped therewith. During the corresponding overrun operating period, the respective exhaust valve then remains in a specific position, in particular in its closed position, i.e., in its valve seat.

[0012] In a further step of the inventive process, a signal received or measured by the knock sensor is evaluated with respect to a predetermined criterion for detecting a malfunction of the valve lift control. Such a malfunction can occur, for example, if the valve lift control or a corresponding switching device has not activated or deactivated the valve lift of the exhaust valve as intended in response to a corresponding control signal. Such a malfunction can be characterized, for example, by the fact that the respective exhaust valve is not fully guided to its respective end position. For example, in such a malfunction, a corresponding guide element for the valve or a corresponding switching device may be damaged.The switching device can detach from the end of the valve stem of the respective exhaust valve facing away from the cylinder, allowing the exhaust valve to fall back into its valve seat unguided and uncontrolled. This can generate an acoustic or structure-borne sound signal in the internal combustion engine, which can be detected by the knock sensor.

[0013] Signals related to a malfunction in the valve lift control may differ from other signals detected by the knock sensor, for example, by exhibiting different signal characteristics and / or occurring at different times. This is taken into account here by the corresponding predefined criterion, for example, by specifying relevant characteristics as a reference or comparison value.

[0014] For evaluation, the signal recorded or measured by the knock sensor—that is, a corresponding raw signal, which may be a continuous voltage signal, for example—can be integrated, particularly over a predefined measurement or time window. The resulting integral value can then be compared, for example, with a predefined threshold value (perhaps as part of the criterion) to determine whether a malfunction has occurred that is reflected or affected by the signal recorded by the knock sensor. Similarly, the height, length, shape, and / or time of a peak occurring in the signal recorded by the knock sensor can be determined and evaluated, for example, compared with corresponding values ​​specified by the criterion to detect malfunctions or other issues.To identify peaks or signal shapes in the signal recorded by the knock sensor that indicate or correspond to faulty switching.

[0015] In a further step of the inventive process, upon detection of at least one such fault, a predetermined control measure relating to the valve lift control is executed or initiated. For this purpose, for example, a corresponding control signal can be automatically generated and output and / or the valve lift can be controlled or adjusted in a predetermined manner.

[0016] According to the invention, the control measure, or at least part thereof, involves deactivating the valve lift of the at least one exhaust valve for at least one subsequent overrun operation, i.e., for each subsequent overrun operating period. This only occurs, however, if at least a predetermined number and / or at least a predetermined density or frequency of malfunctions related to a number of separate overrun operating periods has been detected. In particular, the time since the last activation of the valve lift, the last start-up of the internal combustion engine, and / or the last deletion of an entry indicating a malfunction of the valve lift control from a fault memory can be taken into account.This allows for a particularly reliable response to temporary changes or influences that have led to at least one malfunction, while long-term effects or characteristics do not have an excessively strong influence.

[0017] By not deactivating the valve lift for the subsequent overrun operation immediately upon a single detected malfunction, an unnecessarily harsh reaction to isolated events, which do not necessarily indicate a persistent problem, can be avoided. By disabling the valve lift deactivation for at least the next overrun operation, the valve lift control system and the internal combustion engine are given time in which, firstly, no malfunctions can occur, and secondly, the cause of previous malfunctions may resolve itself without further intervention. For example, malfunctions can be caused by chips or particles that have entered a switching device and may dislodge themselves after a certain operating time of the internal combustion engine, perhaps due to unavoidable vibrations or similar factors.For a later, for example, one after the next, overrun operation, the valve lift deactivation can then be available again, i.e., applied, in order to benefit from the associated advantages.

[0018] The invention is based on the understanding that by deactivating the valve lift, a charge exchange in the cylinder during overrun can be prevented, thus avoiding or reducing charge exchange losses. Furthermore, the present invention is based on the understanding that when the valve lift is switched accordingly, malfunctions, i.e., errors, can occur that can be detected by the knock sensor of the internal combustion engine – which is typically already present in modern internal combustion engines. The knock sensor, or rather...The detection of knock or sound signals using the knock sensor can therefore be used not only to prevent conventional knocking, i.e., uncontrolled combustion processes, for example by appropriately influencing an ignition angle, but also to detect faulty switching of the valve lift control, especially for an unfired overrun operation of the internal combustion engine.

[0019] Such malfunctions can occur particularly during the final stroke of the exhaust valve immediately preceding the respective overrun operation or overrun period, and / or during the first stroke of the exhaust valve immediately following the respective overrun operation or overrun period. At these times, the valve lift control deactivates or activates the exhaust valve stroke, respectively.

[0020] Such switching errors, at least if they occur repeatedly, can damage the respective valve train and ultimately even lead to total engine failure. However, an intrinsically safe switching system that does not permit switching errors is not readily implementable, for example, due to the relatively high speeds of the moving components involved, the correspondingly short time windows, and the delay between the output of a corresponding switching or control signal and its execution. The present invention, however, provides a way to detect and react to such switching errors in a particularly simple manner, especially using components that are already available.This can at least reduce damage or wear resulting from faulty valve lift control, which can ultimately lead to improved reliability in the operation of the internal combustion engine, for example in the form of a longer service life and / or timely warning of a total failure.

[0021] In one possible embodiment of the present invention, the valve lift is deactivated by switching a switchable roller rocker arm provided as part of the valve lift control. After each overrun operation, the valve lift can be automatically reactivated by switching the respective switchable roller rocker arm in the opposite direction. The use of a switchable roller rocker arm represents a practical way to implement the valve lift control or the switching operation of the valve lift, i.e., a variable valve train of the respective exhaust valve.

[0022] In a further possible embodiment of the present invention, only the signal recorded by the knock sensor within a predetermined time window is evaluated to detect the faulty switching. In other words, a dedicated or separate time window can be defined, i.e., predetermined, for the detection of faulty switching of the valve lift control, which can, in particular, differ from a time window defined for conventional knock detection. Such a time window, which thus comprises only a fraction of an operating cycle or a period of piston movement within the cylinder, can readily be defined for the detection of faulty switching, since, according to a finding of the present invention, signals detectable by the knock sensor resulting from faulty switching of the valve lift control do not occur at arbitrary times or in arbitrary states of the internal combustion engine.By limiting the evaluation to knock sensor signals recorded within a specific time window, the amount of data to be processed, and thus the corresponding data processing effort, can be limited or reduced. Furthermore, particularly clear and reliable detection of signals resulting from a malfunction can be achieved, since signals from other sources, which might, for example, exhibit similar waveforms by chance but occur outside the time window, are not even considered. Ultimately, this reduces the number of false positives and, conversely, achieves particularly reliable detection of malfunctions. The predefined time window can, for example, be defined as a specific crank angle range.

[0023] In one possible embodiment of the present invention, the time window defining the signals or signal components of the knock sensor to be considered for detecting malfunctions is automatically and dynamically adjusted during operation of the internal combustion engine, depending on the current engine speed. This dynamic adjustment is made with respect to the temporal position of the time window relative to a predetermined reference time or a corresponding reference event and / or with respect to the length of the time window. In other words, the start and / or end of the time window can automatically vary depending on the engine speed. For example, at a higher engine speed, the time window can begin closer to the respective reference time or reference event and / or be of shorter duration.A reference point or corresponding reference event could be, for example, the passage of a crankshaft through a top or bottom dead center. To implement the dynamic adjustment of the time window proposed here, a corresponding rule or function, a characteristic map, an assignment table, and / or similar can be defined, i.e., stored, which assigns a start time, an end time, and / or a duration of the time window to different rotational speeds of the internal combustion engine. This dynamic adjustment of the time window allows for the particularly reliable, consistent, and efficient detection of signals generated by faulty switching, and thus ultimately the faulty switching itself.

[0024] In a further possible embodiment of the present invention, the control measure, or at least part thereof, involves deactivating the valve lift during overrun until the end of the current operating time of the internal combustion engine. Thus, if a fault is detected, the valve lift can remain activated at least until the end of the current operating time, in particular until the next start-up, especially until the next cold start of the internal combustion engine, until the end of the current journey of a motor vehicle equipped with the internal combustion engine, or at least until the next ignition of the corresponding motor vehicle is switched off; in other words, a corresponding activated switching state of the valve lift or the valve lift control is maintained.This allows for consideration of the fact that a detected malfunction might be caused by a situation or condition that is only temporary during a current journey of the vehicle or a current operating time of the internal combustion engine. The next time the internal combustion engine is started, however, a different situation or condition may exist that does not lead to malfunctions in the valve lift control. Thus, the proposed design strikes a compromise between the particularly reliable and effective prevention of malfunctions and the damage or wear they cause, on the one hand, and the utilization of the advantages achievable through valve lift deactivation during overrun.If faulty switching is detected over several temporally separated operating periods of the internal combustion engine, a longer-term or permanent deactivation of the automatic valve lift deactivation can be carried out for subsequent overrun operating periods.

[0025] Accordingly, in a further possible embodiment of the present invention, the control measure(s) to be executed can be automatically selected based on a predefined escalation cascade of different measures. These different escalating measures can be graded, in particular, depending on an absolute and / or relative number or density of detected malfunctions, a situation, and / or an operating state of the internal combustion engine. For example, upon the first or only detected malfunction, only a corresponding entry can be made in a logbook or fault memory, without affecting the operation of the internal combustion engine or the valve lift control. If several malfunctions are detected, a higher escalation level can, for example, involve the temporary and / or situation-dependent deactivation of the automatic valve lift deactivation.For example, such a deactivation can be applied only for the current operating time or journey, or only when the internal combustion engine speed exceeds a predetermined minimum speed. If malfunctions are detected over several operating times of the internal combustion engine or journeys of a vehicle equipped with an internal combustion engine, the automatic valve lift deactivation during overrun can be permanently deactivated as a further or more stringent control measure. Reactivation can then only occur, for example, during maintenance of the internal combustion engine or a workshop visit of the vehicle in question.From a predetermined escalation level, a warning signal can be generated, such as a warning light that indicates the occurrence of a malfunction, and / or – if necessary at a higher escalation level – an instruction to shut down the internal combustion engine or the respective vehicle can be issued to the operator, user, or driver. Such an escalation cascade allows, on the one hand, excessive damage or wear caused by malfunctions to be limited, and on the other hand, enables a timely and reliable response to serious or persistent causes of malfunctions in the valve lift control, in order to prevent, for example, more serious damage or engine failure.

[0026] In a further possible embodiment of the present invention, an event counter is incremented after a predetermined number of detections of fault switching and decremented after a predetermined number of switching operations of the valve lift control executed without a detected fault switching. The predetermined control measure is then executed or terminated, in particular only when the event counter reaches a predetermined value and / or this value has changed by a predetermined amount, for example, since the last executed control measure. Such an event counter can be implemented in software particularly easily and with minimal effort and can provide a reference or a trigger mechanism for executing the control measures in a particularly simple and reliable manner.The event counter's reading can implicitly contain or summarize a history of both failed and successful (error-free) switching operations of the valve lift control. Using the event counter eliminates the need to maintain or analyze a detailed history or statistics, thus saving considerable data processing effort. The predefined number for incrementing or decrementing the event counter can be 1 or more, and can be the same or different for each. This provides flexibility to adjust the behavior of the internal combustion engine or the valve lift control for various applications according to specific needs or requirements.For example, the number of circuits that must be successfully executed, i.e., without errors, to cause the event counter to decrement can be chosen to be larger for improved longevity of the internal combustion engine than for short-term efficiency optimization of the internal combustion engine.

[0027] In a further possible embodiment of the present invention, during overrun operation, the valve stroke of an intake valve corresponding to the exhaust valve is also automatically deactivated. Corresponding exhaust and intake valves can be located on the same cylinder. In this case, during overrun operation, the respective cylinder is closed on both the intake and exhaust sides. This allows compression work to be performed in the respective cylinder against the closed exhaust and intake valves during overrun operation, and corresponding energy can be at least partially recovered. In other words, during overrun operation, residual compression and subsequent expansion of residual gas contained in the respective cylinder can occur instead of a charge exchange. This allows charge exchange losses to be avoided or reduced particularly effectively during overrun operation.The internal combustion engine can therefore, in addition to the valve lift control for the at least one exhaust valve, also have an intake valve control that enables controlled activation and deactivation of the valve lift of the at least one intake valve, in particular of all intake valves.

[0028] Another aspect of the present invention is a motor vehicle comprising an internal combustion engine with a knock sensor for detecting uncontrolled combustion and a valve lift control for at least one exhaust valve of at least one cylinder of the internal combustion engine. The valve lift control is configured to switch the valve lift of the at least one exhaust valve, i.e., to activate and deactivate the valve lift. The motor vehicle is, in turn, configured to automatically execute or apply at least one variant or embodiment of the method according to the invention, i.e., to operate in accordance with such a method.

[0029] The motor vehicle may include a control unit for executing or applying the corresponding procedure, for example, as part of the valve lift control system or as a separate device. Such a control unit may, for instance, have an input interface for acquiring a signal from the knock sensor, a data storage device and a processor for processing this signal, and an output interface for sending a control signal to execute or initiate a corresponding control action. The data storage device may contain program code or a computer program that represents, i.e., encodes or implements, the procedural steps, actions, or sequences of the corresponding procedure and can be executed by the processor to effect or initiate the execution or application of the corresponding procedure.

[0030] The processor device may be, for example, a microcontroller, a microchip, a microprocessor, a hardware circuit and / or the like, or may include such a device.

[0031] The motor vehicle according to the invention can, in particular, be the motor vehicle mentioned in connection with the method according to the invention. Accordingly, the components of the motor vehicle according to the invention, such as the internal combustion engine, the knock sensor, and the valve lift control, can also be the corresponding components mentioned in connection with the method according to the invention or correspond to them. The motor vehicle according to the invention can therefore have some or all of the properties and / or features described in connection with the method according to the invention.

[0032] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0033] The drawing shows in the single figure a schematic representation of a motor vehicle with an internal combustion engine with a switchable valve lift control.

[0034] Fig.Figure 1 shows a schematic representation of a motor vehicle 10 that has an internal combustion engine 12. This internal combustion engine 12 has at least one, and in this example four, cylinders 14, each with at least one intake valve 16 and at least one exhaust valve 18. The intake valves 16 and the exhaust valves 18, or rather their respective valve lifts, can be controlled or switched by a valve control device 20, i.e., activated and deactivated. The valve control devices 20 can be controlled by a control unit 22. Furthermore, at least one knock sensor 24 is arranged on the internal combustion engine 12. The arrangement of the knock sensor 24 shown here is purely schematic.In practice, i.e., in a real internal combustion engine 12, the knock sensor 24 can also be located elsewhere, for example directly on one of the valve control devices 20. Likewise, several knock sensors can be arranged in a spatially distributed manner.

[0035] The knock sensor 24 is connected to the control unit 22 via a corresponding data or signal line. The control unit 22 is configured to evaluate a signal received by the knock sensor 24 and, based on this, to control the valve control devices 20.

[0036] To increase the variability of a valve train in an internal combustion engine, in this case the internal combustion engine 12, valve control devices 20 can be used. For this purpose, the valve control devices 20 can, for example, be designed as switchable roller rocker arms or each comprise a switchable roller rocker arm. By means of the valve control devices 20, or by means of corresponding switchable roller rocker arms, the valve lift of at least the exhaust valves 18, and in this case also the intake valves 16, can be deactivated while the camshaft is rotating. If the valve lift is deactivated on both the intake and exhaust sides, no charge exchange takes place in the cylinders 14, so that corresponding charge exchange losses are reduced and / or residual compression and expansion can be utilized.

[0037] The control unit 22 is configured to automatically deactivate the valve lift of the intake valves 16 and the exhaust valves 18 for each overrun operation of the internal combustion engine 12 or the motor vehicle 10. For this deactivation of the valve lift, a respective switchable roller rocker arm can be unlocked via a corresponding switching system, for example, in the base circle of a respective cam. In doing so, a corresponding locking pin in the respective switchable roller rocker arm can be moved from a locked position to an unlocked position. However, this movement does not always function completely or reliably. By way of example, a faulty or incomplete movement of the locking pin is here considered or referred to as a malfunction of the valve control unit 20.

[0038] In such a malfunction, the respective valve 16, 18 can strike its respective valve seat ring without guidance. This generates an acoustic event that can be detected by means of the at least one knock sensor 24, i.e., is reflected or manifested in a signal received by the sensor and provided to the control unit 22.

[0039] Malfunctions of the valve control devices 20 can be caused, for example, by interfering particles, excessively low temperatures, excessively low operating or supply voltage of the valve control devices 20, an unfavorable combination of clearances or tolerances of various individual components of the valve control devices 20 or of the internal combustion engine 12 as a whole, and / or the like.

[0040] The control unit 22 is configured to evaluate signals detected by the knock sensor 24 with respect to at least one predefined criterion in order to detect such malfunctions of the valve control devices 20 and to execute at least one predefined control measure in response to one or more detected malfunctions. In particular, the automatic deactivation of the valve lift of valves 16 and 18 for overrun operation of the internal combustion engine 12 or the motor vehicle 10, which is normally provided for in fault-free normal operation, can be at least temporarily deactivated by such a control measure. Likewise, the control unit 22 can, if necessary, intervene in the control or actuation of a switching system or the valve control devices 20 in order to prevent further malfunctions.For example, the actuation point can be varied and / or the deactivation of the valve lift by the control unit 22 can only be initiated or triggered below a predetermined maximum speed of the internal combustion engine 12 and / or only above a predetermined minimum temperature of the internal combustion engine 12 or in the area of ​​the valve control devices 20. If, however, the valve lift has been deactivated for a specific overrun operating time, the valve lift can always be activated at the end of this overrun operating time, regardless of any parameters that may have been considered for the deactivation, in order to enable or resume powered operation of the internal combustion engine 12.

[0041] Overall, the examples described show how fault detection can be implemented using knock sensors for a switchable valve train system, for example to enable particularly reliable operation of an internal combustion engine. Reference symbol list 10 motor vehicle 12 Internal combustion engine 14 cylinders 16 Inlet valve 18 Exhaust valve 20 Valve control unit 22 Control unit 24 knock sensors

Claims

[1] Method for operating an internal combustion engine (12) which has a knock sensor (24) for detecting uncontrolled combustion and a valve lift control (20, 22) for an exhaust valve (18) of a cylinder (14) which is configured to switch the valve lift of the exhaust valve (18), wherein automatically - for overrun operation by means of the valve lift control (20, 22) the valve lift of the exhaust valve (18) is deactivated, - a signal received by the knock sensor (24) is evaluated with regard to a predefined criterion for detecting a malfunction of the valve lift control (20, 22), and - in response to such a detected fault, a predetermined control measure relating to the valve lift control (20, 22) is executed - at least as part of the control measure, the deactivation of the valve lift for at least one subsequent overrun operation is only switched off when at least a predetermined number and / or at least a predetermined temporal and / or temporal density of fault switching related to a number of separate overrun operating times has been detected. [2] Method according to claim 1, characterized by , that the valve lift is deactivated by switching a switchable roller rocker arm (20) provided as part of the valve lift control (20, 22). [3] Method according to any one of the preceding claims, characterized by , that to detect the faulty switching, only the signal recorded by the knock sensor (24) from a specified time window is evaluated. [4] Method according to claim 3, characterized by, that during operation of the internal combustion engine (12) the time window is automatically dynamically adjusted with regard to its temporal position relative to a given reference time and / or with regard to its length depending on the current rotational speed of the internal combustion engine (12). [5] Method according to any one of the preceding claims, characterized by , that as the control measure the deactivation of the valve lift in overrun mode is switched off until the end of a current operating time of the internal combustion engine (12). [6] Method according to any one of the preceding claims, characterized by , that the respective tax measure to be implemented is automatically selected based on a predefined escalation cascade of different measures. [7] Method according to any one of the preceding claims, characterized by, that an event counter is incremented for each predetermined number of detections of fault switching and decremented for each predetermined number of switching operations of the valve lift control (20, 22) carried out without detected fault switching, and that the predetermined control measure is executed or terminated when the event counter reaches a predetermined counter value and / or this has changed by a predetermined amount. [8] Method according to any one of the preceding claims, characterized by , that for overrun operation, a valve stroke of an inlet valve (16) corresponding to the exhaust valve (18) is also automatically deactivated. [9] Motor vehicle (10) comprising an internal combustion engine (12) with a knock sensor (24) for detecting uncontrolled combustion and a valve lift control (20, 22) for an exhaust valve (18) of a cylinder (14) which is configured to switch the valve lift of the exhaust valve (18), wherein the motor vehicle (10) is configured to automatically execute a method according to one of the preceding claims.

Images