DE102017108246A1 - Method for determining the leakage of a crankcase ventilation system - Google Patents

Abstract

The invention relates to a method for determining the leakage of a crankcase ventilation system of an internal combustion engine. In principle, in the method according to the invention, the value of an increase in pressure in a crankcase of the internal combustion engine is analyzed. If the increase in comparison with an IO setpoint exceeds this, there is a leak in the crankcase ventilation system. A prerequisite for this leak determination is the provision of a closed crankcase ventilation system.

Description

The invention relates to a method for determining the leakage of a crankcase ventilation system according to the preamble of patent claim 1.

Crankcase ventilation systems for internal combustion engines are well known. During a power stroke of the internal combustion engine, there is a transfer of gas from a combustion chamber of the internal combustion engine via a formed between piston rings and liner of the internal combustion engine movement gap in the crankcase. If the internal combustion engine is charged with an exhaust gas turbocharger, there may also be an overflow of gas via an oil return line of the exhaust gas turbocharger in the crankcase. These gases are commonly referred to as blow-by gases.

So that the pressure in the crankcase does not increase inadmissible, the crankcase ventilation systems are provided for conditioning the pressure in the crankcase. Furthermore, they serve to prevent escape of the blow-by gases into the environment, i. into the atmosphere. In order for a possible defect of the crankcase ventilation system is detected in time, and it is not or only to a small extent to a leakage of blow-by gases into the atmosphere, it is necessary to check the crankcase ventilation system for leaks.

The patent DE 10 2007 050 087 B3 is a method for checking the tightness of the crankcase ventilation system, which includes to determine the tightness thermodynamic variables such as mass flows and temperatures that are measured, and an enthalpy to be calculated from this.

From the publication DE 100 26 492 A1 shows a method for checking the tightness of the crankcase ventilation system, which has a pressure sensor for determining a pressure in the crankcase. Furthermore, a timing valve in the crankcase ventilation system is formed, which is opened or closed depending on the pressure determined by the pressure sensor.

The publication DE 10 2004 030 908 A1 describes a method for leak testing of a crankcase ventilation system, in which a gas path of the crankcase ventilation system is subjected to a test pressure, wherein the time profile of the pressure in the gas path under the action is compared with an already determined or a calculated desired course.

Also from the pamphlets DE 10 2013 225 388A1 . JP 2013-117176 A and the patent US 5,792,949 It is known to compare a measured with the aid of a pressure sensor in the crankcase pressure with setpoints to determine the tightness of the crankcase ventilation system at defined operating conditions of the internal combustion engine.

It is the object of the present invention to provide an alternative method of determining the leakage for a crankcase ventilation system.

The object is achieved by a method for determining the leak for a crankcase ventilation system with the features of claim 1. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the respective subclaims.

• - ersten Schritt jede mit der Saugleitung unmittelbar verbundene Verbindungsleitung zu einem Messbeginn der Messung des Kurbelgehäusedruckes geschlossen wird und/oder ist,
• - zweiten Schritt die Messung des Kurbelgehäusedruckes über einen Zeitraum ab dem Messbeginn erfolgt, wobei jedem Messzeitpunkt des Zeitraumes der zu diesem Messzeitpunkt gemessene Druck als Druckwert zugeordnet wird, wobei eine Kennlinie mit Hilfe der entsprechenden Messzeitpunkte und zugeordneten Druckwerten ermittelt wird,
• - dritten Schritt eine Bestimmung des Wertes eines Anstiegs der Kennlinie mit Hilfe eines mathematischen Integrals und/oder einer mathematischen Ableitung von mindestens zwei Messzeitpunkten und deren korrespondierenden Druckwerten erfolgt, und
• - vierten Schritt eine Vergleich des ermittelten Wertes des Anstiegs mit einem IO-Sollwert durchgeführt wird, wobei der IO-Sollwert den Wert eines intakten Kurbelgehäuseentlüftungssystems kennzeichnet.

The inventive method for determining the leakage of a crankcase ventilation system, wherein the crankcase ventilation system is associated with a crankcase of an internal combustion engine, and the crankcase ventilation system has at least one connecting line which connects an intake tract with the crankcase, and with a pressure regulating element for regulating a pressure in the crankcase, and with a pressure sensor , which receives the crankcase pressure, and wherein for establishing a closed circuit, the crankcase ventilation system having each directly connected to the suction line connecting line has a closing element, and wherein in one

• - the first step closes each connecting line directly connected to the suction line to a measurement start of the measurement of the crankcase pressure and / or is,
• the second step is the measurement of the crankcase pressure over a period of time from the beginning of the measurement, the pressure measured at that time of measurement being assigned as a pressure value to each measurement time point of the time period, a characteristic curve being determined with the aid of the corresponding measurement times and associated pressure values,
• - Third step, a determination of the value of an increase in the characteristic using a mathematical integral and / or a mathematical derivative of at least two measurement times and their corresponding pressure values is carried out, and
• - fourth step, a comparison of the ascertained value of the increase is made with an IO setpoint, wherein the IO setpoint characterizes the value of an intact crankcase ventilation system.

In a sealed crankcase ventilation system increases after a complete closing of the closing element or if more closing elements are formed, after a complete closing of all closing elements, the pressure in the crankcase slowly. In other words, a characteristic of the pressure over time has a slope of a small value. This slowly increasing pressure over time is due to the fact that in a closed, in other words almost dense crankcase ventilation system, a negative pressure prevailing in the crankcase usually relative to an ambient air pressure is compensated only slowly.

If a rapid increase in pressure is to be measured in the crankcase, this means that there is a leakage point in the crankcase ventilation system, since ambient air enters the crankcase ventilation system via the leakage point and would like to bring about or cause rapid pressure equalization.

An advantage of the method according to the invention is the fact that an improved statement about a leakage of the crankcase ventilation system can be made by considering pressure values at at least two measurement times. In particular, if several measurement times and their corresponding pressure values are evaluated, a further, more accurate statement is possible. Another advantage is to be seen in a high selectivity in the assessment of a defective and thus leaking crankcase ventilation system and an intact and thus leak-free crankcase ventilation system. An additional advantage is that the statement can be evaluated on the basis of any pressure determined in the period of the measurement and thus, for example, no test pressure of the crankcase ventilation system is required.

In a preferred embodiment of the method according to the invention, the measurement over the period directly follows a switch-off time of the internal combustion engine. This has the advantage that in particular nowadays the internal combustion engines used in a motor vehicle have a start-stop device and thus the internal combustion engine is switched off several times, in particular in a city mode. Thus, there are several measurement results in the form of the measurement times and their corresponding crankcase pressures, which is another strong statement to make a condition of the crankcase ventilation system. Furthermore, the inventive method is characterized when switching off the internal combustion engine by a statement to be made quickly to the state, for example. By the numerous shutdown operations in city operation, from. Another advantage is that very small leakage points, from about 2mm can be detected.

In an alternative embodiment of the method according to the invention, the measurement takes place over the period during a load step of the internal combustion engine. Since in a load increase a so-called part-load ventilation line of the crankcase ventilation system is closed and a so-called full load vent line of the crankcase ventilation system is not yet open, there is a closed crankcase ventilation system during the load step and can be used to determine a possible leakage.

It should be noted at this point that the crankcase ventilation system can never be completely leak-tight, as the combustion engine itself, its pistons and corresponding control elements, inlet and outlet valves are positioned differently over various locations and thus could permit an inflow of ambient air. Therefore, in this context, a leak-free crankcase ventilation system is also referred to as a sealed crankcase ventilation system with the connecting lines closed.

If the method according to the invention is used during a load step, it is advantageous for the error-free determination of a possible leakage of the crankcase ventilation system if the crankcase pressure has an IO setpoint over a further period of time immediately preceding the measurement.

It has been found that limiting the time period to at most the 60 second period for evaluating the crankcase ventilation system, i. H. In other words, the leakage determination is sufficient for reliable diagnosis. Thus, a very fast method and reliable method is realized.

For simplified and therefore cost control, the closing element works in the form of a self-regulating non-return valve. Thus, no control and / or other controls for closing the connecting line provided with the closing element are required.

Advantageously, the result of the leakage diagnosis is displayed in a display of a motor vehicle having the internal combustion engine. Thus, the operator of the motor vehicle is almost always informed about the condition of his crankcase ventilation system and, if there is a leak or leakage, quickly visit a workshop, so not impermissibly leakage fluid, or blow-by gas enters the environment.

• 1 in einer schematischen Darstellung eine Verbrennungskraftmaschine mit einem Kurbelgehäuseentlüftungssystem,
• 2 in einem p-t-Diagramm einen Kennlinie eines Kurbelgehäusedrucks bei leckagefreiem Zustand des Kurbelgehäuseentlüftungssystems, einen Kennlinie des Kurbelgehäusedrucks bei Leckagezustand des Kurbelgehäuseentlüftungssystems sowie einen Kennlinie eines Umgebungsdruckes bei abgeschalteter Verbrennungskraftmaschine, und
• 3 in einem p-t-Diagramm einen Kennlinie in einer Saugleitung der Verbrennungskraftmaschine, einen Kennlinie in einem Kurbelgehäuse der Verbrennungskraftmaschine und die Kennlinie des Umgebungsdruckes bei einem Lastsprung der Verbrennungskraftmaschine.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or shown alone in the figure can be used not only in the respectively specified combination, but also in other combinations or in isolation, without the scope of To leave invention. Show it:

• 1 in a schematic representation of an internal combustion engine with a crankcase ventilation system,
• 2 in a pt diagram, a characteristic of a crankcase pressure at leak-free condition of the crankcase ventilation system, a characteristic curve of the crankcase pressure at leakage condition of the crankcase ventilation system and a characteristic of an ambient pressure with the internal combustion engine off, and
• 3 in a pt diagram, a characteristic in a suction line of the internal combustion engine, a characteristic curve in a crankcase of the internal combustion engine and the characteristic of the ambient pressure at a load step of the internal combustion engine.

An internal combustion engine according to the invention 1 , which is designed in the form of a reciprocating engine, is shown schematically in FIG 1 illustrated. The reciprocating engine has a crankcase 2 on which with a cylinder head 3 is firmly connected. In the crankcase 2 are in non-illustrated cylinder liners predominantly taken along a longitudinal axis of the cylinder liner axially moving, not shown piston. These pistons are mounted with the help of a connecting rod, not shown in detail on a crankshaft, not shown, of the reciprocating engine, wherein the crankshaft is rotatably received in the crankcase, at which usually takes place a torque decrease for driving a drive shaft, not shown. The axial movement is a so-called tilting movement of the piston placed, since the piston is mounted at a side facing away from the crankshaft end of the connecting rod by means of a piston pin a tilting movement about the piston pin executable.

The cylinder head 3 has not shown in detail control elements for filling and emptying of a so-called combustion chamber, which is formed by means of the cylinder head, the piston and the cylinder liner. The control elements of the reciprocating engine are usually designed in the form of poppet valves, so-called inlet valves and exhaust valves, which are movably received in the cylinder head and realize opening and closing of corresponding, formed in the cylinder head openings, inlet openings and outlet openings. The filling of the combustion chamber is done with fresh air. The emptying of the combustion chamber corresponds to a displacement of a combustion residue formed in the combustion chamber of the fresh air, which was supplied for combustion fuel. During a so-called charge change phase, the combustion residue, in particular exhaust gas, is displaced out of the combustion chamber via the outlet openings, predominantly by a stroke movement of the piston and also by incoming fresh air. Under fresh air is not alone to understand the air sucked in through the environment, since today many internal combustion engines have an exhaust gas recirculation unit, by means of which exhaust gas is fed into the intake. In other words, the fresh air drawn into the cylinder may also contain some of the exhaust gas.

Due to the translational and tilting movement of the piston, a movement gap formed between the piston and the cylinder liner can not be completely sealed off, with piston rings (not shown) being movably received on an outer circumference of the piston for sealing purposes. During the movement of the piston, there is a diffusion of gas present in the combustion chamber, ie both fresh air and exhaust gas, a so-called blow-by gas, from the combustion chamber via the movement gap into the crankcase 2 , which is designed to receive the crankshaft movable.

To avoid a crankcase 2 damaging overpressure is the blow-by gas via a so-called crankcase ventilation 4 , which takes the form of an opening in the crankcase 2 is designed to dissipate.

So that the blow-by gas can not get directly into the environment, is a crankcase ventilation system 5 , the crankcase breather 4 comprising, provided, which is the result of an operating point blow-by gas of the internal combustion engine 1 takes up and environmentally friendly, for example, by supplying the internal combustion engine 1 degrades.

The internal combustion engine 1 is an exhaust gas turbocharger 6 assigned to its compressor 7 in an intake tract 8th the internal combustion engine 1 is included. In an alternative embodiment of the internal combustion engine 1 is a compressor for compressing intake air of the internal combustion engine 1 in the intake tract 6 arranged. The compressor 7 is in the intake tract 8th upstream of the cylinder head 3 positioned between the compressor 7 and the cylinder head 3 a metering element 9 , which is designed in this embodiment in the form of a throttle valve, is arranged. The dosing element 9 serves a fuel supply corresponding to an accelerator pedal position.

Between the dosing element 9 and the compressor 7 is a non-illustrated intercooler for cooling the compressor 7 sucked fresh air arranged.

The crankcase ventilation system 3 consists of an extensive line system. Starting from the crankcase breather 4 is a first connection line 10 the crankcase 2 with a separation unit 11 , in particular a Ölnebelabscheider, flow-through connected. The separation unit 11 is by means of a second connection line 12 with a suction line 13 of the intake tract 8th permeable connected. The second connection line 12 opens upstream of the compressor 7 in the suction line 13 ,

The separation unit 11 is further by means of a third connection line 14 with a pressure control element 15 connected, which in the crankcase 2 prevailing pressure regulates. The pressure control element 15 is in turn with the suction line 13 with the help of a fourth connection line 16 permeable connected, wherein the fourth connecting line 16 between the metering element 9 and the cylinder head 3 in the suction line 13 empties. In an exemplary embodiment, the internal combustion engine according to the invention 1 is the pressure control element 15 on the cylinder head 3 positioned. It regulates the crankcase pressure by throttling the pressure in the suction line 13 ,

Furthermore, the crankcase ventilation system 5 a fifth connection line 17 which comprise the separator 11 with the suction line 13 connects, the fifth connecting line 17 between the compressor 7 and the metering element 9 in the suction line 13 empties. The fifth connection line 17 is in the form of a so-called PCV line, referred to in technical jargon as a "positive crankcase ventilation" line, formed on this PCV line, especially in trained in the form of gasoline engines internal combustion engines, a small part of the fresh air sucked in the form of purging air the crankcase 2 to be led. In the fifth connection line 17 a non-illustrated check valve is provided which a gas flow starting from the crankcase 2 in the suction line 13 in derogation.

In the crankcase 2 is a pressure sensor 18 provided for determining the crankcase pressure.

So that the blow-by gas from the crankcase 2 can be sucked, in this a negative pressure by means of the pressure control element 15 generated, the internal combustion engine 1 is in operation. Depending on the operating state, the generation of the negative pressure takes place in different ways.

Basically, to bring about a negative pressure in the crankcase 2 one in the suction line 13 used intake manifold pressure. However, this intake manifold pressure is at different points on the suction line 13 different sized. In particular, the intake manifold pressure is usually during operation of the exhaust gas turbocharger 6 upstream of the compressor 7 , hereinafter referred to as intake manifold pressure before compressor, smaller than he downstream of the compressor 7 is, wherein this intake manifold pressure is referred to below with intake manifold pressure after compressor.

Is the internal combustion engine 1 in partial load operation, the negative pressure with the help of in the suction line 13 adjacent intake manifold pressure after compressor brought about. One is in the fourth connection line 16 arranged first check valve 19 of the crankcase ventilation system 5 open. Unless the internal combustion engine 1 in full load operation, the negative pressure is using the in the suction line 13 applied intake manifold pressure before compressor caused. One is in the second connection line 12 arranged second check valve 20 open, with the first check valve 19 closed, so no air over the fourth connection line 16 in the crankcase 2 can occur. The second check valve 20 However, it is closed until the pressure in the crankcase 2 is greater than the pressure before the compressor.

Of course, in part-load operation of the internal combustion engine 1 the second check valve 20 closed by an overflow of gas via the second connecting line in the crankcase 2 to prevent. The first check valve 19 closes as soon as the pressure to the compressor is greater than the pressure in the crankcase 2 , The two check valves 19 . 20 are self-regulating pressure-dependent executed. They are both closed, if in the crankcase 2 a vacuum is applied and the internal combustion engine 1 is out of order, or is switched off. Thus, the crankcase ventilation system 5 even after the operation of the internal combustion engine 1 largely tight and it can almost no exhaust gases after operation of the internal combustion engine 1 from the crankcase ventilation system 5 get into the environment.

Indicates the crankcase ventilation system 5 a leak on, escapes over the site, the leakage point, uncontrolled leakage fluid consisting of the blow-by gas from the crankcase ventilation system 5 , A detection of the leakage point is possible with the aid of the method according to the invention described below.

This can be done by measuring the crankcase pressure over a period of time T recorded. Typically, the crankcase pressure increases with a near-sealed crankcase ventilation system 5 very slowly. This means that to check for a possible leak the crankcase ventilation system 5 must be closed. These are all check valves 19 . 20 and the check valve of the fifth connection line 17 close to it via the suction line 13 no gas, fresh air and / or exhaust gas can escape.

The check valves 19 . 20 and the check valve of the fifth connection line 17 are both at a shutdown of the internal combustion engine 1 as well as in a load jump the same, for example. From the throttled operation of the internal combustion engine 1 in the charged operation, closed and there is thus a closed circuit of the crankcase ventilation system 5 in front. When a load jump, the first check valve 19 the fourth connection line 16 , ie the so-called part-load vent line closed when the load increases, the second check valve 20 the second connection line 12 , so-called full load vent line, still closed. In other words, that means the period T the measurement at a load jump a measurement start t1 , which corresponds to the beginning of the load increase, and a measuring end t2 , which by opening the second check valve 20 is characterized.

In a first embodiment of the method according to the invention, the examination of the crankcase ventilation system takes place 5 on leakage when switching off the internal combustion engine 1 , The inspection of the crankcase ventilation system 5 starts when switching off the internal combustion engine 1 , wherein the shutdown time in the first embodiment, the start of measurement t1 of the period T corresponds to the measurement.

In 2 are in a pt diagram an exemplary first characteristic K _iO the crankcase pressure in leaking condition of the crankcase ventilation system 5 , an exemplary second characteristic K _niO the crankcase pressure at leakage condition of the crankcase ventilation system 5 and an exemplary third characteristic Ku of the pressure in the environment, resp. the atmosphere, represented. Every characteristic K _iO . K _niO , Ku is made up of several value pairs, with each measurement time t of the period T on at this time of measurement t measured pressure as pressure value p is assigned.

The measurement of the crankcase pressure takes place over the period T at the beginning of the measurement t1 , The measuring end t2 which the period T determined, can be flexible, taking a period T of a maximum of 60 seconds.

For leakage detection is a so-called IO setpoint in a control and control unit of the internal combustion engine, not shown 1 deposited, which is a reference value of the slope of the characteristic K _iO the intact, thus leak-free crankcase ventilation system 5 is. The adjustment can be carried out with several pressure value-time pairs. The measurement can be over a longer period of time T In particular, the period is at most 60 seconds.

In a first variant of the first exemplary embodiment of the method according to the invention, the value of the increase is in the form of a mathematical derivation of the characteristic determined with the aid of the determined pressure-value-time-point pairs K _iO ; K _niO certainly.

In a second variant of the first exemplary embodiment of the method according to the invention, the value of the increase is determined by determining a mathematical integral of the characteristic curve determined with the aid of the determined pressure value / time-point pairs K _iO ; K _niO determined.

If the pressure in the crankcase increases 2 over a period of time T slowly, as is the characteristic K _iO the crankcase pressure in leaking condition of the crankcase ventilation system 5 shows, in other words, that the value of the slope of the curve K _iO is small and thus has no or only an insignificant difference in a comparison with the IO setpoint, the crankcase ventilation system 5 intact and has no leakage.

If the pressure in the crankcase increases 2 over a period of time T fast, as is the characteristic K _niO the crankcase pressure in leaking condition of the crankcase ventilation system 5 shows, this means that gas leakage into the crankcase ventilation system via one of the leaks attributable to leakage 5 penetrates, as in the closed crankcase ventilation system 5 there is a negative pressure. The increase in pressure in the crankcase 2 is then stopped when a pressure equalization in the crankcase 2 achieved. In other words, when an ambient pressure or atmospheric pressure corresponds to the crankcase pressure. From this point, the crankcase points 2 a constant crankcase pressure. Thus, as a start of measurement could t1 the time of switching off the internal combustion engine 1 be determined and as the end of the measurement t2 of the period T a first time of several measurement times t , which are characterized by a constant pressure.

In a second embodiment of the method according to the invention, the examination of the crankcase ventilation system takes place 5 on leakage at a load jump of the internal combustion engine 1 ,

In 3 are a fourth characteristic in a pt diagram K _S a pressure in the suction line 13 the internal combustion engine 1 , the first characteristic K _iO the pressure in the crankcase 2 the internal combustion engine 1 and the third characteristic K _U a pressure of the environment or atmosphere at a load jump of the internal combustion engine 1 shown. The load jump corresponds in this example to a rapid change from a throttled operation of the internal combustion engine 1 in a charged operation of the same.

For a reliable diagnosis, it is necessary that during operation of the internal combustion engine 1 before the load jump, ie in other words before further opening of the metering element 9 , in the crankcase 2 a certain, so-called crankcase target pressure prevails. In other words, that means a certain load on the internal combustion engine 1 over a further period. When the load is increased, the second check valve closes 20 in the second connection line 12 and the check valve 19 in the fourth connection line 16 is not open yet.

It thus takes place with the crankcase ventilation system closed 5 the inclusion of the crankcase pressure. If the crankcase pressure rises slowly, there is no leakage in the crankcase ventilation system 5 in front. However, if the crankcase pressure increases rapidly, that is, in other words, a value of the result of the derivative and / or the integral is greater than the IO setpoint, there is a leak in the crankcase ventilation system 5 in front.

The method according to the invention thus has the following method steps:

First process step:

Close everyone with the suction line 13 directly connected connection line 12 . 16 . 17 at the beginning of the measurement t1 the measurement of the crankcase pressure

Second process step:

Measurement of the crankcase pressure over the period T , with each measurement time t of the period T the at this time of measurement t measured pressure as pressure value p is assigned, where a characteristic K _iO ; K _niO with the help of the corresponding measurement times t and associated pressure values p is representable

Third procedural step:

Determination of the value of an increase of the characteristic K _iO ; K _niO with the help of a mathematical integral and / or a mathematical derivation of at least two measurement times t and their corresponding pressure values p , and

Fourth process step:

Comparison of the value of the ascertained increase with the IO setpoint.

The result of the leakage determination can, for example, in particular in case of a defect of the crankcase ventilation system 5 , in the first embodiment at the next start of the internal combustion engine 1 or in the second embodiment during operation of the internal combustion engine 1 in an operating display of one with the internal combustion engine 1 equipped motor vehicle are displayed.

The method according to the invention is therefore characterized in particular by the evaluation of a plurality of crankcase pressures measured at specific measuring times. Basically, a pressure increase is evaluated, whereby the value of the increase is determined. This can be done on the basis of absolute or relative pressures.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

crankcase

3

cylinder head

4

crankcase ventilation

5

Crankcase ventilation system

6

turbocharger

7

compressor

8th

intake system

9

metering

10

First connection line

11

separation unit

12

Second connection line

13

suction

14

Third connection line

15

Pressure control element

16

Fourth connection line

17

Fifth connection line

18

pressure sensor

19

First check valve

20

Second check valve

p

pressure value

t

Measuring time

t1

measurement start

t2

measuring

K _iO

First characteristic

K _niO

Second characteristic

K _S

Fourth characteristic

K _U

Third characteristic

T

Period

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007050087 B3 [0004]
• DE 10026492 A1 [0005]
• DE 102004030908 A1 [0006]
• DE 102013225388 A1 [0007]
• JP 2013117176 A [0007]
• US 5792949 [0007]

Claims (7)

Method for determining the leakage of a crankcase ventilation system, wherein the crankcase ventilation system (5) is associated with a crankcase (2) of an internal combustion engine (1), and the crankcase ventilation system (5) has at least one connecting line (12; 16; 17) having an intake tract (8) the crankcase (2) flows through, and with a pressure control element (15) for controlling a pressure in the crankcase (2), and with a pressure sensor (18) which receives the crankcase pressure, and wherein to achieve a closed circuit, the crankcase ventilation system (5) each connecting line (12, 16) directly connected to the suction line (13) has a closing element (20, 19), characterized in that in a first step, each connecting line (12, 16) directly connected to the suction line (13) becomes a Measurement start (t1) of the measurement of the crankcase pressure is closed and / or is - second Step the measurement of the crankcase pressure over a period of time (T) from the start of measurement (t1) takes place, each measuring time (t) of the period (T) of the measured at this measurement time (t) pressure is assigned as a pressure value (p), wherein a characteristic curve (K _iO ; K _niO ) is determined with the aid of the corresponding measurement times (t) and associated pressure values (p), - third step, a determination of the value of an increase of the characteristic (K _iO ; K _niO ) by means of a mathematical integral and / or a mathematical derivative of at least two measuring times (t) and their corresponding pressure values (p) takes place, and - fourth step, a comparison of the determined value of the increase is performed with the IO setpoint. Method according to Claim 1 , characterized in that the measurement over the period (T) directly follows a switch-off of the internal combustion engine (1). Method according to Claim 1 , characterized in that the measurement over the period (T) during a load step of the internal combustion engine (1). Method according to Claim 3 , characterized in that over a the time period (T) immediately preceding the further period of the crankcase pressure having an IO setpoint. Method according to one of the preceding claims, characterized in that the period (T) is not greater than 60 seconds. Method according to one of the preceding claims, characterized in that the closing element (20; 19) functions in the form of a self-regulating non-return valve. Method according to one of the preceding claims, characterized in that a result of the leakage diagnosis is displayed in a display of a motor vehicle having the internal combustion engine (1).

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