EP1747352B1 - Oil level monitoring system for an internal combustion engine - Google Patents

Abstract

Disclosed is an internal combustion engine in an operating gear, comprising an oil reservoir (6) for holding oil in the area of a crankcase (10). An oil gauge (12) is used for detecting oil contained in the oil reservoir (6) and generating a corresponding signal which is evaluated in an evaluation unit (13) so as to generate a piece of oil level information. Preferably, said piece of oil level information is generated only when starting the internal combustion engine or for a certain period of time following starting of the internal combustion engine. Once the internal combustion engine has reached its operating speed, the oil level is no longer monitored.

Description

The invention relates to a working device with an internal combustion engine according to the preamble of patent claim 1 and to a method for monitoring an oil level in an internal combustion engine according to the preamble of patent claim 24.

Internal combustion engines, especially four-cycle petrol or diesel engines, require sufficient oil supply to be properly lubricated to be provided by oil in an oil reservoir. The oil reservoir is usually located in the vicinity of a crankcase, so that by lubricating oil, but also by an additional oil pump, the oil to the lubrication points of the cylinder, the piston, the bearing, etc. is distributed.

The presence of a required amount of engine lubrication oil is z. B. via an oil dipstick or via various sensors (eg., Oil pressure switch for lubrication with oil pump) checked. The sensors can be used in a monitoring circuit such that they shut down the engine when a lack of oil or the lack of warning lights o. Ä. Show. Motors without oil pump usually have measuring rods or a sight glass.

Simple devices for oil level monitoring also consist in that the oil level is measured by means of a float and - in the case of a lack of oil - the ignition of the internal combustion engine is interrupted. In this case, the engine does not start up when there is no oil. With highly vibrating machinery and an uncontrolled, turbulent oil movement in the engine, the engine can turn off even if there is enough oil in itself. However, since the oil is whirled up, the float takes a position that represents a lack of oil, so that the appropriate action is taken and the engine is turned off.

Since, as explained above, when the oil level is detected to be too low, the known monitoring systems prevent starting of the internal combustion engine from the outset, it is not possible for the operator to see why the engine is not starting. Accordingly, it may take unsuitable or unnecessary measures to restart the engine set (replace spark plugs, clean carburettor, etc.).

Many implements have an internal combustion engine and a driven by the internal combustion engine vibration exciter. These tools include z. B. rammers for soil compaction. Vibration plates. Hammers, etc. Due to the strong vibration generated by the vibration exciter, the oil in the combustion engine is highly muddled. Accordingly, with known oil monitoring systems, it is difficult to determine if enough oil is available to lubricate the engine.

In the US 6,580,366 B1 For example, a system for determining the chemical change of oil in a vehicle engine will be described. Part of the system is an oil level gauge. Based on a change in the amount of oil, the change in the chemical composition of the oil is determined. To obtain the required measuring accuracy, the oil quantity is determined with the help of an oil quantity sensor before starting the machine.

From the US 4,306,525 An oil gauge is known in which an optical oil sensor is provided on an oil return passage in an internal combustion engine. The measurement and display of the oil level is determined immediately after the closing of a key switch, ie even before starting the internal combustion engine.

The invention has for its object to provide a working device with an internal combustion engine, in which information about the oil level can be reliably obtained. Furthermore, a method for monitoring an oil level in an internal combustion engine is to be specified.

The object is achieved by a working device according to claim 1 and method according to claims 23 and 24.

The working device according to the invention has an oil measuring device, for detecting that oil is present in the oil reservoir, and for generating a corresponding signal. Furthermore, an evaluation device for generating oil level information on the basis of the signal from the oil meter is provided. The oil level information can be generated in a certain period of time after starting the internal combustion engine, wherein the oil level information even after the start of the internal combustion engine and / or after the expiration of the specific period is present after starting.

Specifically, the period within which the oil level information is obtained before a vibrator belonging to the working machine is driven by the internal combustion engine ends.

Since it is extremely difficult to determine the oil level in an internal combustion engine, which in particular no oil pump, but only an oil reservoir (oil sump) identifies in operation, because the oil is swirled in the crankcase of the internal combustion engine, the oil level information is determined at a time to the oil is still largely at rest, so due to the gravity effect in the oil reservoir. Once the internal combustion engine has reached its full operating speed, especially when the internal combustion engine drives a vibration generator provided in the implement and / or the specific period has elapsed, the oil level monitoring is no longer reliable. Although it can still be carried out according to the invention, it should no longer be regarded as reliable.

The underlying idea is therefore that the oil level information is determined at a time at which the oil measuring device can still provide reliable measurement results, but the oil level information even at a later date, when the oil measuring device reliable results are no longer expected, eg during normal operation of the implement, is still available. In this context, oil level information can be an evaluated measured value or a correspondingly conditioned signal, which represents in particular whether sufficient oil is present in the oil reservoir or not.

On the basis of the oil level information certain consequences can be initiated, as will be explained later.

Simply stated, the oil level is measured at the start (before, during or shortly after), ie at a point in time when the implement is still in relative calm.

The authoritative, inventively produced and also available at a later date oil level information does not exclude that even later, so in operation of the implement, further oil level information can be determined. However, these oil level information is either not sufficiently reliable or are evaluated according to other, not further detailed here, as not belonging to the invention criteria. On the other hand, the oil level information generated early on is decisive for the invention.

In connection with the starting of the internal combustion engine, the start of a rotation of a crankshaft of the internal combustion engine is considered as the start of starting. At the end of the starting is a time when the rotational speed of the crankshaft is greater than a starting speed, which by a Starting device (eg an electric starter or a recoil starter) is imposed on the crankshaft. Then, namely, the internal combustion engine is able to automatically increase its crankshaft speed, without the need for further support by the starting device.

It is particularly advantageous if the specific time period after starting the internal combustion engine is short in relation to the total operating time of the internal combustion engine after starting. Assuming that the internal combustion engine is in operation for at least a few minutes, the predetermined time period should be in the range of seconds. In particular, the period of time within which the oil level information is obtained should end before the vibrator is driven by the internal combustion engine.

The oil level information is obtained by the evaluation device on the basis of the signal from the oil meter. In essence, the oil level information will indicate that there is enough oil in the oil reservoir or that there is a lack of oil.

If the implement has a vibrator, the beginning of the driving of the vibrator by the engine may trigger the end of the "certain period". This means that the oil level information can be obtained until the vibration exciter is activated. However, the vibration exciter will exert such strong vibrations on the implement that afterwards, ie in normal working mode reliable oil level monitoring is no longer possible.

In another embodiment of the invention, the oil level information may be generated until the clutch couples the internal combustion engine to the vibration exciter. This ensures that the strong vibrations of the vibration exciter can not yet affect the generation of oil level information.

Again, in another embodiment of the invention, the oil level information is producible when the engine has reached a predetermined minimum speed after starting. The minimum speed can be chosen relatively low and is z. B. required to with the help of appropriate Aggregates of the internal combustion engine to generate a supply voltage for the oil meter and the evaluation. Since usually an internal combustion engine when starting relatively quickly reaches at least one idle speed, often even an overlying operating speed, the period during which the oil level information is generated, very short.

In an advantageous further development of the invention, the oil level information can be generated as long as the actual crankshaft speed is less than a predetermined operating speed at which the implement performs its intended work.

It is particularly advantageous if the oil level information is generated once at the beginning of an operating time of the internal combustion engine, that is to say in particular during or after starting. This means that at a specific, most appropriate time, when there is still a relatively large amount of oil in the oil reservoir, the oil level is determined or the presence of oil detected and evaluated in the form of oil level information. If the oil level is OK or oil is available, no further action is required within the operating cycle. This is especially true when the internal combustion engine typically only has a relatively short operating time until it is stopped again. When the internal combustion engine is restarted, a new oil level check is carried out.

If, on the other hand, the oil level information indicates that there is too little oil in the oil reservoir, the internal combustion engine can be switched off with the aid of a stop device. As such stop means is suitable for. B. the ignition system of the engine, which is controlled via the evaluation in a suitable manner to effect the stopping of the engine.

However, it is not absolutely necessary that the engine is shut down immediately after detecting the oil shortage and generating appropriate oil level information. Rather, a predetermined period of time may elapse after the presence of the specific oil level information until the stop device switches off the internal combustion engine. This has the advantage that the operator still appropriate information, eg. B. by acoustic or visual warnings can be transmitted to inform him of the lack of oil.

In another embodiment of the invention, the evaluation device is coupled to a speed control device, so that in the presence of an oil level corresponding lack of oil level information, the speed of the engine to a lying below an operating speed speed value, z. B. an idle speed, is adjustable. At idle, the internal combustion engine can usually be operated even with insufficient lubrication for a relatively long time without being damaged. Again, the operator can still be displayed suitable information so that he recognizes the lack of condition.

The acoustic, but especially the visual warning can be issued over a certain period of time, even if the oil level information is no longer present. For example, it is possible that the internal combustion engine has been switched off by one of the measures described above or by the action of the operator. In that case, it might be helpful if e.g. serving as a visual warning indicator LED is still operated for a certain period. For energy supply, a correspondingly designed capacitor device may be required.

In a preferred embodiment of the invention, the internal combustion engine has a voltage device for generating and / or storing electrical energy. This may be z. Example, to act a Magnetzündanlage for generating electrical energy or a battery ignition system for storing electrical energy. The voltage device provides the supply voltage required for the oil measuring device and the evaluation device. Particularly in the case of a magnetic ignition system, the supply voltage is generated only when the internal combustion engine is started, that is to say when the crankshaft is rotated. The oil level information is then generated in each case immediately after the start of the boot process, which also should be followed a relatively short period of time.

If the oil level information already before starting the engine is to be obtained, it is particularly advantageous if a voltage device for storing electrical energy for the supply of the oil meter and the evaluation is provided. With the help of this electrical energy, the oil level information can then be stored as needed.

Preferably, the evaluation device is integrated in the oil meter, so that the two components form a unit and can be installed together in the internal combustion engine.

An oil sensor provided in the oil measuring device can be operated according to various principles, wherein in particular capacitive, optical, thermal and / or mechanical measuring principles are suitable.

It is particularly advantageous if the oil sensor, optionally with an integrated evaluation device, can be screwed into a motor housing of the internal combustion engine. This z. B. a hole can be used, which was originally intended for a dipstick.

A method according to the invention comprises the following steps: First, the internal combustion engine is started by the starter device (electric starter or recoil starter). Immediately after the start of the starting process of the internal combustion engine, the oil meter is operated so that the presence of oil in the oil reservoir can be detected and a corresponding signal can be generated. The signal is evaluated to generate oil level information that indicates whether enough oil is present in the engine or not.

The oil level information remains available even after the start phase and can be used to initiate appropriate consequences.

Preferably, the oil level information is generated only after reaching a predetermined minimum speed of the internal combustion engine.

If the oil level information corresponds to an information that there is too little oil in the oil reservoir, various measures can be triggered: The operation of the internal combustion engine can immediately or after Expired a predetermined period of time after detecting the lack of oil. Furthermore, it is possible to limit the rotational speed of the internal combustion engine to a rotational speed value which is below an operating rotational speed. Alternatively or additionally, acoustic and / or optical warning signals can be transmitted to the operator.

Fig. 1

schematisch einen bekannten Verbrennungsmotor;

Fig. 2

schematisch ein erfindungsgemäßes Ölüberwachungssystem; und

Fig. 3

ein Flussdiagramm zur Erläuterung des erfindungsgemäßen Ölüberwachungssystems.

These and other advantages and features of the invention are explained in more detail below by way of example with the aid of the accompanying figures. Show it:

Fig. 1

schematically a known internal combustion engine;

Fig. 2

schematically an inventive oil monitoring system; and

Fig. 3

a flowchart for explaining the oil monitoring system according to the invention.

In Fig. 1 a known internal combustion engine is shown, so that only a brief description is given below. As internal combustion engines are basically motors with separate lubrication, ie z. B. four-stroke gasoline engines or diesel engines.

In a motor housing 1, a crankshaft 2 is rotatably mounted on which in turn at least one connecting rod 3 is rotatably mounted. At the other end of the connecting rod 3, a piston 4 is held, which is in a cylinder 5 axially reciprocable. Below the crankshaft is an oil reservoir 6 (oil sump, oil sump), is collected in the lubricating oil. The oil can be drained through an oil outlet 7 if the oil is dirty or depleted.

At the in Fig. 1 shown internal combustion engine is provided in a provided in the motor housing 1 thread 8, a static oil pressure switch 9. The oil pressure switch 9 has the disadvantage that it works in principle like a float, so that it drives the operation of the internal combustion engine, especially when the engine drives a vibration generator, not shown, and accordingly the oil very strong in a Crankshaft 2 surrounding crankcase 10 is swirled, can no longer reliably determine the presence of a sufficient amount of oil. Thus, there is the possibility that the oil pressure switch 9 detects a lack of oil, although in the crank chamber 10 sufficient oil circulates.

Fig. 2 shows a section Fig. 1 wherein the oil pressure switch 9 is replaced by an oil level monitoring device 11 according to the invention. The oil level monitoring device 11 has an oil measuring device 12 and an evaluation device 13.

In the example shown, the oil measuring device 12 has a sensor which operates with a capacitive measuring principle. The sensor is positioned so that it dips into the oil at a sufficient amount of oil in the oil reservoir 6 and evaluates the oil as a dielectric between two capacitor electrodes.

For this purpose, a resonant circuit is excited whose frequency depends on whether the capacitor electrodes of the sensor are in the oil or not. The frequency is evaluated by a serving as evaluation 13 microprocessor and compared with predetermined frequency values, so that then an oil level information can be obtained, which states that the sensor is in the oil (sufficient amount of oil) or not (lack of oil).

The power supply of the oil level monitoring device 11 via a terminal 14 to which a not shown charging cable (Abstellerkabel) provided in the internal combustion engine, known per se Magnet ignition system can be connected. Since magnetic ignition systems are known in many different ways, a more detailed description is unnecessary at this point. Instead of a magnetic ignition system, it is also possible to use a battery ignition system for operating the internal combustion engine and for feeding the oil level monitoring device 11.

About the port 14 is for the oil level monitoring device 11, the possibility to turn off the engine immediately upon detection of a lack of oil or after a predetermined period of time. This is z. B. the terminal 14 short-circuited to the ground of the housing 1. Optionally, the oil level monitoring device 11 via the connection 14 also regulate the speed of the engine so that they z. B. only one idle speed corresponds.

Instead of the capacitive sensor, other physical measuring principles can also be used.

It is particularly advantageous that the oil level in the oil reservoir 6 is detected and evaluated when starting the engine, so that the oil level monitoring device 11 can already derive the required oil level information at this early point in time.

The oil level monitoring device 11 can of course also during the course of the engine continue to determine information because z. B. atomized or spilled oil continues to drip on the sensor of the oil meter 12. In the case of dry running or insufficient lubrication, oil will no longer reach the oil measuring device 12, so that even at this point in time a shutdown of the internal combustion engine by the oil level monitoring device 11 can be effected.

By suitable design of the oil measuring device 12 and the evaluation device 13, it is possible that already measured during the first crankshaft rotation by the starter (recoil starter or electric starter) of the engine, the oil quantity and the oil level information is obtained. As a result, the turbulence of the oil in the oil reservoir 6 subsequent to the starting operation no longer causes measurement errors.

So it can be z. B. adjust that the oil level information is obtained only once, at the start of the engine and subsequent oil level information, especially messages about a supposed lack of oil are ignored. It is assumed that if the internal combustion engine contains enough oil when starting, there will be enough oil available for the subsequent operating time. This is all the more true when the internal combustion engine is used in a work tool with a relatively short operating time (eg less than one hour). For each new start, namely, a new oil level control can be performed.

Due to the fact that the oil level monitoring device 11 receives electrical energy by means of the ignition system, which is present in any case in the internal combustion engine, an additional power supply is unnecessary. The oil level monitoring device 11 is thus supplied on the one hand by the ignition system of the engine with energy. On the other hand, it can cause the engine to stop via the ignition system.

When using the oil level monitoring device 11 in a diesel engine, a suitable system for power generation, eg. As a battery or an alternator for feeding the oil level monitoring device 11 may be provided. Furthermore, the oil level monitoring device 11 can then be coupled to a device for interrupting the fuel supply (eg, electrovalve).

In the case of an amount of oil considered sufficient at startup, the oil level monitoring device 11 can subsequently remain inactive so that the engine runs without being influenced by the oil level monitoring device 11. If desired, however, the oil level monitor 11 may continue to monitor the oil level and, if necessary, intervene in extreme situations.

When the internal combustion engine for driving a vibration generator in a working device, for. B. in a rammer, a hammer or a vibrating plate for soil compaction, it is particularly useful if the measurement of the oil level, d. H. obtaining the oil level information, before the activation of the vibration exciter takes place. In fact, at this point in time, most of the oil in the oil reservoir 6 is still located. After activating the vibration exciter, however, such strong vibrations are exerted that the oil can be distributed throughout the crankcase 10.

As an oil measuring device 12 may also be a conventional stand, z. As a static oil switch, are used, if this is suitable for vibration. The evaluation device 13 should then be designed such that the oil level measurement - as stated above - only at the beginning of the engine operation, ie evaluates the measurement signals of the oil switch when starting. During operation of the engine, in particular after activation of the vibration generator, the Ignore the measurement signals of the oil switch from the evaluation device 13.

In Fig. 3 a flow chart is shown showing the operation of the oil level monitoring system according to the invention.

In a step S1, the internal combustion engine is started, for. B. by pulling a Reversierstarters.

As a result, in step S2, a supply voltage for the electronics used in the oil level monitoring device 11 is available.

In step S3, an oscillation frequency f _{osz of} a resonant circuit equipped with a microprocessor is measured with the aid of the capacitive sensor of the oil measuring device 12. The frequency f _osz changes depending on the oil wetting of the sensor. The measurement in step S3 can already be carried out at the moment of starting, ie the first time the reversing starter is pulled. The measured data are then stored in step S4. In step S5, the engine speed is measured and compared in step S6 with a predetermined value (here: 1000 min ^-1 ). As long as the engine speed has not yet reached the predetermined speed, the speed is further measured in step S5.

If the engine speed has exceeded the predetermined limit speed, it is checked in step S7 whether the measured resonant circuit frequency f _{osz is} greater than a preset frequency f _lim . The preset frequency f _lim is factory-stored in the production of the implement when the sensor is calibrated. The frequency f _lim corresponds to the resonant circuit frequency for the minimum required oil level.

If the measured frequency f _{osz is} greater than f _lim , a light-emitting diode LED is turned on for operation control in step S8 and the oil level monitoring is switched off in step S9. The amount of oil in the internal combustion engine is no longer monitored during this operating cycle. Only when the engine is restarted - after previously switching off - does the oil level control start again with step S1.

If it is determined in step S7 that the measured frequency f _{osz is} smaller is the predetermined frequency limit f _lim , the system concludes that there is not enough oil left in the engine. Then, in step S10, a light emitting diode LED is set in flashing operation to give the operator a warning signal. During this time, the engine keeps running. After lapse of a certain period of time (eg, 10 seconds, step S11), the ignition of the engine is stopped in step S12, so that the engine is turned off. Accordingly, in step S13, the light-emitting diode also goes out. The operator now has the opportunity to refill oil.

Claims (26)

1. Working device having a combustion engine and a vibration exciter which can be driven by the combustion engine, wherein the combustion engine has:

   - a starter device for starting the combustion engine;

   - an oil tank (6) in the region of a crank chamber (10) to receive oil;

   - an oil measuring device (12) for recognising that oil is present in the oil tank (6) and for generating a corresponding signal; and

   - an evaluation device (13) for generating oil level information on the basis of the signal from the oil measuring device (12);
   wherein

   - the oil level information can be generated in a set time period after start-up of the combustion engine;

   - the time period is set in such a way that it ends before the vibration exciter is driven by the combustion engine; and wherein

   - the oil level information is still present even after the set time period following start-up has elapsed.
2. Working device as claimed in claim 1, characterised in that the set time period is short in relation to an operating time of the combustion engine.
3. Working device as claimed in claim 1 or 2, characterised in that the commencement of driving of the vibration exciter by the combustion engine triggers the end of the set time period.
4. Working device as claimed in claim 2 or 3, characterised in that a coupling for coupling the combustion engine to the vibration exciter is provided and that the oil level information can be generated by the evaluation device (13) after start-up of the combustion engine until the coupling couples the combustion engine to the vibration exciter.
5. Working device as claimed in any one of claims 1 to 4, characterised in that the oil level information can be generated until commencement of a working phase in which the working device performs its intended work.
6. Working device as claimed in any one of claims 1 to 5, characterised in that the oil level information can be generated within a preset time span after a preset minimum revolution speed of the combustion engine has been reached.
7. Working device as claimed in claim 6, characterised in that the oil level information can be generated immediately after the preset minimum revolution speed of the combustion engine has been reached.
8. Working device as claimed in any one of claims 1 to 7, characterised in that the oil level information can be generated as long as the actual crankshaft revolution speed is lower than a specified working revolution speed.
9. Working device as claimed in any one of claims 1 to 8, characterised in that the oil level information can be generated once.
10. Working device as claimed in any one of claims 1 to 9, characterised in that

    - a stop device for interrupting operation of the combustion engine is provided;

    - the evaluation device (13) is coupled to the stop device; and that

    - in the presence of specific oil level information, the operation of the combustion engine can be interrupted by the stop device.
11. Working device as claimed in claim 10, characterised in that the operation of the combustion engine can be interrupted by the stop device after the elapse of a preset time span following the specific oil level information being present.
12. Working device as claimed in any one of claims 1 to 11, characterised in that the evaluation device (13) is coupled to a revolution speed regulating device, and that in the presence of specific oil level information the revolution speed of the combustion engine can be adjusted by the revolution speed regulating device to a revolution speed value below an operational revolution speed.
13. Working device as claimed in any one of claims 1 to 12, characterised in that the evaluation device (13) is coupled to a display device and that in the presence of specific oil level information visual and/or acoustic display information can be output by the display device.
14. Working device as claimed in claim 13, characterised in that the display information can be output by the display device over a set time span even if the oil level information is no longer present.
15. Working device as claimed in any one of claims 1 to 14, characterised in that the specific oil level information corresponds to information that too little oil is present in the oil tank (6).
16. Working device as claimed in any one of claims 1 to 15, characterised in that the oil level information is present in the form of a signal.
17. Working device as claimed in any one of claims 1 to 16, characterised in that

    - the combustion engine has a voltage device for generating and/or storing electrical power;

    - by means of the voltage device and after start-up of the combustion engine a supply voltage for the oil measuring device (12) and the evaluation device (13) can be provided;

    - the oil level information can be generated over a short time span by the evaluation device (13) immediately after commencement of the starting procedure of the combustion engine.
18. Working device as claimed in any one of claims 1 to 16, characterised in that

    - the combustion engine has a voltage device for storing electrical power;

    - by means of the voltage device and before start-up of the combustion engine a supply voltage for the oil measuring device (12) and the evaluation device (13) can be provided;

    - the oil level information can be generated by the evaluation device (13) before commencement of the starting procedure of the combustion engine;

    - the oil level information can be stored.
19. Working device as claimed in any one of claims 1 to 18, characterised in that the evaluation device (13) is integrated into the oil measuring device (12).
20. Working device as claimed in any one of claims 1 to 19, characterised in that the oil measuring device (12) has an oil sensor.
21. Working device as claimed in claim 20, characterised in that the oil sensor operates according to a capacitive, optical, thermal and/or mechanical principle.
22. Working device as claimed in claim 20 or 21, characterised in that the combustion engine has an engine housing (1) and that the oil sensor can be screwed into a thread (8) provided in the engine housing (11).
23. Method for monitoring an oil level in a combustion engine for driving a vibration exciter in a working device, wherein the combustion engine has:

    - a starter device for starting the combustion engine;

    - an oil tank (6) in the region of a crank chamber (10) to receive oil;

    - an oil measuring device (12) for recognising that oil is present in the oil tank (6) and for generating a corresponding signal; and

    - an evaluation device (13) for generating oil level information on the basis of the signal from the oil measuring device (12);
    having the steps of

    - starting the combustion engine by means of the starter device;

    - operating the oil measuring device (12) immediately after commencement of the starting procedure of the combustion engine until activation of the vibration exciter, in order to recognise the presence of oil in the oil tank (6) and to generate the corresponding signal;

    - evaluating the signal to generate oil level information.
24. Method as claimed in claim 23, characterised in that the oil level information is generated only after a preset minimum revolution speed of the combustion engine has been reached.
25. Method as claimed in claim 23 or 24, characterised in that the oil level information is generated only once during each starting procedure.
26. Method as claimed in any one of claims 23 to 25, characterised in that specific oil level information corresponds to information that too little oil is present in the oil tank (6), and that on the basis of the specific oil level information one or a plurality of the following measures are initiated:

    - immediate interruption of the operation of the combustion engine;

    - interruption of the operation of the combustion engine after a specified time span following determination of the specific oil level information has elapsed;

    - limiting the revolution speed of the combustion engine to a revolution speed value below the operational revolution speed;

    - activating an acoustic and/or visual display.

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