DE102017203201B4 - Method for venting a crankcase of an internal combustion engine - Google Patents

Abstract

Method for venting a crankcase (3) of an internal combustion engine (2), having at least the following steps: a) supplying at least one cylinder (4) of the internal combustion engine (2) with air via an intake area (10), b) conducting gas out of the crankcase (3) via a crankcase ventilation line (13) into the intake area (10),c) determining at least one comparative value for comparison with a pressure parameter measured in the crankcase ventilation line (13) using a mathematical model as a mathematical Function as a function of at least one operating point parameter of the internal combustion engine (2), the mathematical function being created using a computer simulation and stored in a control unit (11), so that the comparative value is obtained by loading the mathematical function and by using the currently available values of the at least one operating point parameter is obtained,d) measuring at least one pressure parameter in the crankcase ventilation line (13),e) comparing the at least one pressure parameter measured in step d) with the comparison value determined in step c), andf) triggering at least one warning function (15) , if it is recognized in step e) that the at least one printing parameter deviates from the corresponding comparison value by more than a predefinable value.

Description

The invention relates to a method for venting a crankcase of an internal combustion engine.

In internal combustion engines with combustion chambers designed like cylinders in motor vehicles, work machines, aircraft, etc., it is known to divert gas that collects in a crankcase via a ventilation line into the intake area or the exhaust gas area of the internal combustion engine. In this way, such gas can be prevented from escaping into the surroundings of the internal combustion engine. Such gas collects in the crankcase essentially because it passes from a combustion chamber (or a cylinder) through a gap past a piston of the cylinder into the interior of the crankcase. This gas is also often called "blow-by gas". If this gas were to enter the environment of the internal combustion engine directly (e.g. at the seal of the crankshaft bearings), it would not have been subjected to exhaust gas purification. This can be prevented by a targeted supply of this gas to the intake area or to the exhaust area of the internal combustion engine. Furthermore, this gas must also be vented from the (usually airtight) crankcase to avoid pressure build-up in the crankcase, since increased pressure in the crankcase would adversely affect the operation of the internal combustion engine.

In order to ensure post-combustion of this gas, it is preferred to supply the gas again to a combustion chamber of the internal combustion engine via the intake area of the internal combustion engine. Therefore, the gas is usually fed into the intake area of an internal combustion engine. For this purpose, crankcase ventilation devices are known in which a crankcase ventilation line connects the crankcase of an internal combustion engine to the intake area of this internal combustion engine.

Known crankcase ventilation devices have the disadvantage that no or only a partial diagnosis of the tightness is possible. This applies in particular to crankcase ventilation devices in which a crankcase ventilation line is connected to an intake area. The pressure in the intake area of an internal combustion engine usually fluctuates greatly. Such strong pressure fluctuations are transmitted to the crankcase ventilation device. Therefore, in the case of pressure fluctuations in the crankcase ventilation device, it is often not possible to identify very quickly the cause of these pressure fluctuations. In particular, it is often not possible to clearly assign an occurring pressure fluctuation to a leak in the crankcase ventilation device.

The publications DE 101 63 780 B4 , DE 103 20 054 A1 , DE 10 2013 218 313 A1 , DE 10 2013 225 388 A1 , DE 10 2016 201 589 B3 and DE 20 2005 012 403 U1 each disclose approaches to crankcase ventilation and their diagnosis.

Proceeding from this, it is the object of the present invention to continue to solve or at least alleviate the technical problems described in connection with the prior art. In particular, a method is to be presented for effectively diagnosing a crankcase ventilation line for leaks.

This object is achieved with a method according to the features of patent claim 1. Further advantageous refinements of the method are specified in the dependently formulated patent claims. The features listed individually in the patent claims can be combined with one another in any technologically meaningful way and can be supplemented by explanatory facts from the description, with further embodiment variants of the invention being shown.

1. a) Versorgen mindestens eines Zylinders der Verbrennungskraftmaschine mit Luft über einen Ansaugbereich,
2. b) Leiten von Gas aus dem Kurbelgehäuse über eine Kurbelgehäuse-Entlüftungs-Leitung in den Ansaugbereich,
3. c) Ermitteln mindestens eines Vergleichswertes zum Vergleich mit einem in der Kurbelgehäuse-Entlüftungs-Leitung gemessenen Druckparameter unter Verwendung eines mathematischen Modells als eine mathematische Funktion in Abhängigkeit von mindestens einem Betriebspunktparameter der Verbrennungskraftmaschine, wobei die mathematische Funktion mit einer Computersimulation erstellt und in einer Steuereinheit gespeichert wird, sodass der Vergleichswert durch Laden der mathematischen Funktion und durch Einsetzen der aktuell vorliegenden Werte des mindestens einen Betriebspunktparameters erhalten wird,
4. d) Messen mindestens eines Druckparameters in der Kurbelgehäuse-Entlüftungs-Leitung,
5. e) Vergleichen des in Schritt d) gemessenen mindestens einen Druckparameters mit dem in Schritt c) ermittelten Vergleichswert, und
6. f) Auslösen mindestens einer Warnfunktion, wenn in Schritt e) erkannt wird, dass der mindestens eine Druckparameter von dem entsprechenden Vergleichswert um mehr als einen vorgebbaren Wert abweicht.

According to the invention, a method for venting a crankcase of an internal combustion engine is presented. The method comprises at least the following steps:

1. a) supplying at least one cylinder of the internal combustion engine with air via an intake area,
2. b) conducting gas from the crankcase via a crankcase ventilation line into the intake area,
3. c) determining at least one comparison value for comparison with a pressure parameter measured in the crankcase ventilation line using a mathematical model as a mathematical function as a function of at least one operating point parameter of the internal combustion engine, the mathematical function being created with a computer simulation and stored in a control unit is, so that the comparison value is obtained by loading the mathematical function and by using the currently available values of the at least one operating point parameter,
4. d) measuring at least one pressure parameter in the crankcase ventilation line,
5. e) comparing the at least one pressure parameter measured in step d) with the comparison value determined in step c), and
6. f) triggering at least one warning function if it is recognized in step e) that the at least one printing parameter deviates from the corresponding comparison value by more than a predefinable value.

The process steps are preferably but not necessarily carried out in the order given. In particular, it is also preferred that method steps a), b), c) and d) are carried out simultaneously and in parallel during the entire operation of an internal combustion engine. The wording "during the entire operation" means in particular that no active measures are taken to prevent the execution of these process steps. In particular, the wording is not intended to rule out the possibility that the actions assigned to the individual steps may be temporarily interrupted or carried out repeatedly due to operating conditions of the internal combustion engine. The supply of a cylinder according to step a) always takes place, for example, only in intake phases. Depending on the prevailing pressure conditions, the flow of gas out of the crankcase can also be interrupted, although this is basically possible during the entire operation and is not actively prevented. Steps c) and d) can also be carried out with a fixed (or variable) repetition frequency. It also applies to steps c) to d) that preferably no measures to prevent these steps are carried out during the entire operation. In further embodiment variants of the method, it is also possible for individual steps a) to d) (in particular steps c) and d)) to be carried out only temporarily—in particular only when certain operating conditions of the internal combustion engine are present.

The internal combustion engine is in particular an internal combustion engine such. B. an Otto engine or a diesel engine of a motor vehicle. The internal combustion engine usually includes one or more cylinders in which fuel is combusted with air. These cylinders form the combustion chamber(s) of the internal combustion engine. The internal combustion engine also preferably includes a crankcase in which a crankshaft connected to pistons mounted in the cylinders is arranged. The crankshaft is surrounded by the crankcase. The crankcase protects the crankshaft and provides a space for lubricant. The crankcase is usually sealed in an airtight manner, in particular also in order to prevent exhaust gas and crankcase ventilation gases from escaping from the crankcase.

Gas can escape into the crankcase between the walls of the cylinders and the pistons. The internal combustion engine also has a crankcase ventilation line.

In step a), the at least one cylinder is preferably supplied with air via an intake area, so that fuel can be combusted with the air in the cylinder. The term "intake area" here means the entire area lying upstream of the combustion chambers of the internal combustion engine, through which air is supplied to the combustion chambers for combustion. The intake area itself can possibly also be divided by a compressor in an area lying upstream of the compressor and an area lying downstream of the compressor (in the flow direction of the air between the compressor and the combustion chambers of the internal combustion engine). In particular, the intake area can include one or more intake line(s).

As mentioned above, blow-by gas can get inside the crankcase. In step b), gas in the crankcase (in particular the aforementioned blow-by gas) is preferably routed out of the crankcase through the crankcase ventilation line and fed to the intake area. As a result, this gas is (re)supplied to the combustion chambers of the internal combustion engine and the gas is effectively prevented from escaping into the environment. The crankcase ventilation line can be formed from a hose made of rubber or plastic, for example.

In step c), at least one comparison value is determined for comparison with a pressure parameter measured in the crankcase ventilation line.

As already explained, the at least one comparison value is determined in step c) using a model as a function depending on at least one operating point parameter of the internal combustion engine. This model can also be referred to as a pressure model.

The comparison value can be understood in particular as an expected value that the measured pressure parameter assumes, provided in particular that there is no leakage in the crankcase ventilation line. The pressure expected in this way in the crankcase ventilation line can, in particular, depend on a current operating state of the internal combustion engine and/or vice versa exercise influences. It is therefore preferred that the comparison value is determined taking into account possible influences. In this way, a current comparison value that is adapted in particular to the current operating state is provided.

A speed, a load, an air throughput and/or a torque of the internal combustion engine come into consideration here as operating point parameters.

The comparative value is calculated as a mathematical function using the mathematical model for the respective ranges of the operating point parameters. The mathematical function for calculating the comparison value is created using a computer simulation. The one- or multi-dimensional mathematical function thus obtained is stored in the control unit. The comparison value currently to be used for step e) is obtained by loading the corresponding mathematical function and by inserting the currently available values of the operating point parameters.

The function described for calculating the comparison value can also be a model or pressure model. The at least one comparison value is particularly preferably determined in step c) using a pressure model which simulates the conditions or properties influencing the pressure in the crankcase ventilation line and in the components connected to the crankcase ventilation line. A comparative value can be calculated based on this pressure model. The conditions or properties of the crankcase ventilation line or the components that are connected to the crankcase ventilation line and communicate with the crankcase ventilation line in terms of pressure are preferably simulated in the form of parameters. Such communicating components are, for example, the crankcase connected to the crankcase ventilation line, the intake area and valves that are connected to the crankcase ventilation line. The parameters can be parameters of a formula that is implemented in the model or the print model. With this formula, the comparison value can be calculated from the input variables.

In step d) the pressure parameter is measured. This is preferably done with at least one pressure measuring device that records the crankcase pressure and is integrated into the crankcase ventilation line, for example. The pressure measuring device can have a pressure sensor of any type and in particular also sensors that detect a pressure-related deformation of a section of the crankcase ventilation line, it being possible to draw conclusions about a pressure in the crankcase ventilation line from this deformation. If necessary, a plurality of the pressure parameters can also be obtained via a corresponding plurality of pressure measuring devices, with the different pressure measuring devices preferably being arranged at different points on the crankcase ventilation line. The pressure measuring device can be an electronic pressure sensor.

For step e), a comparison is preferably made for each measured pressure parameter (from step d)) with a respective corresponding comparison value (from step e)).

The at least one warning function to be triggered in step f) can in particular be an indicator light, a device for generating an acoustic signal, or a memory for an electronic error message for later reading (in particular in a workshop). The at least one warning function is preferably not triggered in step f) if the comparison in step e) shows that none of the measured pressure parameters falls below or exceeds the respective corresponding comparison value (depending on whether the respective comparison value was specified as an upper or lower limit ). In that case, step f) is not carried out. Alternatively, step f) can be understood in the case that step f) comprises deciding not to trigger the at least one warning function.

The connection between the crankcase and the intake area via the crankcase ventilation line can create a vacuum in the crankcase because air is sucked into the combustion chamber via the intake area. Because the pressure in the intake area can fluctuate, it is preferred that the crankcase ventilation line has a valve.

The valve is in particular a check valve. A check valve is preferred (free) flow in one direction, while flow in the opposite direction through the valve is prevented. The model preferably has at least one condition that simulates the behavior of a valve adjacent to the crankcase ventilation line.

This feature of the model can be used to emulate a check valve, for example. Valves that subdivide the crankcase ventilation line and connect it to adjacent components have the property that they restrict the communication of drue impact differently depending on the opening state of the valve. This property can be efficiently reproduced with the help of conditions in the model.

A pressure in the crankcase usually continues to such a check valve via the crankcase ventilation line. Between the check valve and the intake area, the pressure in the crankcase ventilation line is subject in particular to the pressure fluctuations that also occur in the intake area and which can make it difficult or impossible to diagnose this section of the crankcase ventilation line for leaks. The check valve is therefore preferably arranged as close as possible to a crankcase ventilation line connection of the intake area (i.e. at the junction point of the crankcase ventilation line in the intake area) and thus as close as possible to the end of the crankcase ventilation line. By arranging the check valve in this way, a particularly large part of the crankcase ventilation line can be diagnosed for leaks using the continued pressure of the crankcase.

It is further preferred that the internal combustion engine has a compressor such as a turbocharger for compressing the air. The performance of the internal combustion engine can be increased by compressing the air before it is introduced into the cylinder or cylinders. In an internal combustion engine with a compressor, it is preferable for the crankcase ventilation line to be connected to the compressor and for the check valve to be arranged directly on the compressor. It can thereby be achieved that the influence of pressure fluctuations in the intake area on the measurement of the pressure in the crankcase ventilation line is at least reduced.

In a further preferred embodiment of the method, the model specifies linear relationships between input variables and comparison values at least for certain pressure ranges.

In particular, the operating point parameters come into consideration as input variables, as a function of which the comparison value or values are determined using the model in step c). In particular, the comparison values can be obtained as output values of the model. A particularly simple calculation can be carried out by using linear relationships. In particular, the comparison values for the specific pressure ranges can be determined using linear approximations.

• - eine Drehzahl der Verbrennungskraftmaschine,
• - ein Drehmoment der Verbrennungskraftmaschine,
• - eine Last der Verbrennungskraftmaschine,
• - ein Luftdurchsatz der Verbrennungskraftmaschine
• - ein Druck in der Umgebung der Verbrennungskraftmaschine,
• - ein Druck in dem Ansaugbereich,
• - eine Temperatur in dem Ansaugbereich,
• - eine Temperatur in der Umgebung der Verbrennungskraftmaschine,
• - eine Temperatur in einem Kühlkreislauf der Verbrennungskraftmaschine, und
• - ein Druck in dem Kurbelgehäuse.

In a further preferred embodiment of the method, the comparison value in step c) is determined at least as a function of one of the following measured input variables:

• - a speed of the internal combustion engine,
• - a torque of the internal combustion engine,
• - a load of the internal combustion engine,
• - an air flow rate of the internal combustion engine
• - a pressure in the environment of the internal combustion engine,
• - a pressure in the intake area,
• - a temperature in the intake area,
• - a temperature in the vicinity of the internal combustion engine,
• - a temperature in a cooling circuit of the internal combustion engine, and
• - a pressure in the crankcase.

The parameters mentioned are preferably measured with respective sensors which are each connected to the control unit. The comparison value is preferably determined in the control unit by calculation from the available parameters.

• - ein Kurbelgehäuse mit einer Kurbelwelle,
• - mindestens einen Brennraum nach Art eines Zylinders,
• - ein Ansaugbereich zur Versorgung des mindestens einen Zylinders mit Luft,
• - eine Kurbelgehäuse-Entlüftungs-Leitung zum Leiten von Gas aus dem Kurbelgehäuse in den Ansaugbereich,
• - mindestens eine Druckmessvorrichtung in der Kurbelgehäuse-Entlüftungs-Leitung zum Messen mindestens eines Druckparameters in der Kurbelgehäuse-Entlüftungs-Leitung,
• - eine Steuereinheit, die zumindest dazu bestimmt und eingerichtet ist, ein Verfahren wie beschrieben durchzuführen, wobei Schritt c) zumindest unter Verwendung des von der Druckmessvorrichtung gemessenen Druckparameters durchgeführt wird.

As a further aspect, an internal combustion engine is presented, which at least includes:

• - a crankcase with a crankshaft,
• - at least one combustion chamber in the manner of a cylinder,
• - an intake area for supplying the at least one cylinder with air,
• - a crankcase ventilation line for conducting gas from the crankcase into the intake area,
• - at least one pressure measuring device in the crankcase ventilation line for measuring at least one pressure parameter in the crankcase ventilation line,
• - a control unit which is at least intended and set up to carry out a method as described, wherein step c) is carried out at least using the pressure parameter measured by the pressure measuring device.

The particular advantages and design features described above for the method can be applied and transferred to the internal combustion engine described.

The invention is preferably used in a motor vehicle with an internal combustion engine that is designed as described or that can be operated as described.

The particular advantages and design features described above for the method can be applied and transferred to the motor vehicle described.

The invention and the technical environment are explained in more detail below with reference to the figure. The figure shows a particularly preferred embodiment to which the invention is not limited. In particular, it should be pointed out that the figure and in particular the proportions shown are only schematic. ???

1 shows a motor vehicle 1 with an internal combustion engine 2, which includes a crankcase 3, in which a crankshaft 6 is located. In the internal combustion engine 2, a cylinder 4 is shown as an example. In practice, however, the internal combustion engine 2 usually has a plurality of cylinders 4 , for example two, three, four, five, six or more cylinders 4 . A piston 5 is arranged in the cylinder 4 and is connected to a crankshaft 6 via a connecting rod 7 is. Air can be conducted through an intake area 10 to the cylinder 4 via an air filter 9 . The amount of air supplied to the cylinder 4 can be regulated via a throttle flap 16 . Fuel is burned in the cylinder 4 with the air sucked into the cylinder 4, whereby the piston 5 is driven. The crankshaft 6 is thereby rotated via the connecting rod 7 . The crankcase 3 can be cooled via a cooling circuit 17 which includes a cooler 18 .

Furthermore, a crankcase ventilation line 13 is shown, which connects the crankcase 3 to the intake area 10 . The crankcase ventilation line 13 is connected to the intake area 10 at a crankcase ventilation connection 14 . The direction of flow of air and gas from the crankcase 3 is indicated by arrows.

A pressure measuring device 8 for measuring a pressure parameter in the crankcase ventilation line 13 (or in a line connected to the crankcase ventilation line) is integrated into the crankcase ventilation line 13 . The pressure measuring device 8 is connected to a control unit 11 via a cable 12 . The control unit 11 is designed and set up to compare a pressure parameter measured with the pressure measuring device 8 with a comparison value. Depending on the result of this comparison, a warning function 15 is triggered with the control unit 11 .

Between the pressure measuring device 8 and the crankcase ventilation connection 14 , a check valve 19 designed as a check valve 19 is integrated into the crankcase ventilation line 13 , the passage direction of which is directed from the crankcase 3 towards the intake area 10 .

Reference List

1

motor vehicle

2

internal combustion engine

3

crankcase

4

cylinder

5

Pistons

6

crankshaft

7

connecting rod

8th

pressure gauge

9

air filter

10

intake area

11

control unit

12

Cable

13

Crankcase ventilation line

14

Crankcase ventilation connection

15

warning function

16

throttle

17

cooling circuit

18

cooler

19

Valve

Claims (7)

Method for venting a crankcase (3) of an internal combustion engine (2), having at least the following steps: a) supplying at least one cylinder (4) of the internal combustion engine (2) with air via an intake area (10), b) conducting gas out of the crankcase (3) via a crankcase ventilation line (13) into the intake area (10), c) determining at least one comparative value for comparison with a pressure parameter measured in the crankcase ventilation line (13) using a mathematical model as a mathematical function dependent of at least one operating point parameter of the internal combustion engine (2), the mathematical function being created using a computer simulation and stored in a control unit (11), so that the comparison value is obtained by loading the mathematical function and by using the currently available values of the at least one operating point parameter, d) measuring at least one pressure parameter in the crankcase ventilation line (13), e) comparing the at least one pressure parameter measured in step d) with the comparison value determined in step c), and f) triggering at least one warning function (15) if in step e) it is detected that the at least one printing parameter deviates from the corresponding comparison value by more than a predefinable value. procedure after claim 1 , wherein the model comprises at least one parameter which simulates the pressure-influencing properties of the crankcase ventilation line (13) and/or such properties of a component communicating with the crankcase ventilation line (13) in terms of pressure. procedure after claim 1 or 2 , wherein the model has at least one condition that simulates the behavior of a valve adjacent to the crankcase ventilation line (13). Procedure according to one of Claims 1 until 3 , whereby the model specifies linear relationships between input variables and comparative values, at least for certain pressure ranges. Method according to one of the preceding claims, wherein the comparison value in step c) is determined as a function of at least one of the following measured input variables: - a speed of the internal combustion engine (2), - a torque of the internal combustion engine (2), - a load of the internal combustion engine (2), - an air flow rate of the internal combustion engine - a pressure in the environment of the internal combustion engine (2), - a pressure in the intake area (10), - a temperature in the intake area (10), - a temperature in the vicinity of the internal combustion engine (2), - A temperature in a cooling circuit (17) of the internal combustion engine (2), and - a pressure in the crankcase (3). Internal combustion engine (2) comprising at least: - a crankcase (3) with a crankshaft (6) - at least one combustion chamber in the manner of a cylinder (4), - an intake area (10) for supplying the at least one cylinder (4) with air, - a crankcase ventilation line (13) for conducting gas from the crankcase (3) into the intake area (10), - at least one pressure measuring device (8) in the crankcase ventilation line (13) for measuring at least one pressure parameter in the Crankcase ventilation line (13), - a control unit (11) which is at least intended and set up to carry out a method according to one of Claims 1 until 5 to perform. Motor vehicle (1) with an internal combustion engine (2) according to claim 6 is executed and / or for carrying out a method according to one of Claims 1 until 5 is set up.

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