DE102017108249A1 - Crankcase ventilation system, internal combustion engine and method for determining the leakage of a crankcase ventilation system - Google Patents

Abstract

The invention relates to a crankcase ventilation system (5) of an internal combustion engine (1), which has a vibratable diaphragm which is formed in the closed crankcase ventilation system (5) at a leakage of the crankcase ventilation system (5) a pressure in the crankcase (2) to vibrate. Furthermore, the invention relates to an internal combustion engine and a method for determining the leakage of a crankcase ventilation system.

Description

The invention relates to a crankcase ventilation system according to the preamble of patent claim 1, an internal combustion engine according to claim 5 and a method for determining the leakage of a crankcase ventilation system according to the preamble of patent claim 6.

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, an overflow of gas via an oil return line of the exhaust-gas turbocharger into the crankcase can likewise occur. These gases are commonly referred to as blow-by gases.

To ensure that the pressure in the crankcase does not increase inappropriately, the crankcase ventilation systems serve to condition 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 published patent US 2015 009 0204 A1 is to take a crankcase ventilation system for an internal combustion engine, which has a vent tube in which a vent valve is arranged. The vent valve has at least one check valve or an electronically controllable valve. To determine a leak-free crankcase ventilation system pulsations or oscillations are measured by means of a pressure sensor in the crankcase, which have at least an expected amplitude at leak-free system. If the amplitude is smaller than expected, there is a leak in the crankcase ventilation system.

From the publication DE 10 2013 218 313 A1 shows a crankcase ventilation system for an internal combustion engine, which has a vent tube, which opens into a suction line of an intake tract. In the vent tube, a pressure sensor is provided, which is designed to measure a pressure in the vent tube. With the help of the pressure measured in the vent tube or its course, a diagnostic method for checking the tightness of the crankcase ventilation system is proposed.

It is the object of the present invention to provide a simple and therefore inexpensive crankcase ventilation system. In addition, it is the object to provide a cost-effective internal combustion engine with a reliable crank ventilation system. Another object is to provide a simple leak determination method for a crankcase ventilation system.

The object is achieved with a crankcase ventilation system comprising the features of claim 1. The additional object is achieved by an internal combustion engine having the features of patent claim 5. The further object is achieved by a method for determining the leakage for a crankcase ventilation system having the features of patent claim 6. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the respective subclaims.

An inventive crankcase ventilation system, which is assigned to an internal combustion engine, has at least one connecting line, which is designed to connect to a crankcase of the internal combustion engine associated separation unit with a suction line of an intake tract of the internal combustion engine can be connected. Furthermore, the crankcase ventilation system comprises a pressure regulating element for regulating a pressure in the crankcase and a pressure sensor, which is designed to receive a pressure in the crankcase. To bring about a closed circuit, the crankcase ventilation system has each connecting line directly connected to the suction line to a closing element. According to the invention, a vibratable diaphragm is formed in the crankcase ventilation system for detecting a leaky crankcase ventilation system. Thus, a simple and thus inexpensive crankcase ventilation system is formed, which is designed without complex measuring elements and / or measuring electronics for determining a possible leakage in the crankcase ventilation system. Due to the oscillating diaphragm, it is possible in a closed crankcase ventilation system to bring about a vibration of the crankcase pressure, which can be measured with the aid of the pressure sensor.

In a preferred embodiment, the oscillatable membrane corresponds to a membrane of the pressure control element. Pressure control elements can be designed in the form of a membrane-spring element. If the pressure control element has a membrane, this can be used as a vibratory membrane, whereby an even more cost-effective crankcase ventilation system is brought about.

Advantageously, the membrane is arranged in the region of the pressure sensor.

In a further embodiment, the closing element is designed in the form of a non-return element. For a further cost reduction of the crankcase ventilation system according to the invention is possible because no further control and / or control elements for closing the provided with the closing element connection line are required.

Another aspect relates to an internal combustion engine having a crankcase and an intake tract, the crankcase having a crankcase ventilation system according to one of claims 1 to 4. The advantage is that a low-cost internal combustion engine can be provided by the low-cost crankcase ventilation system, which has a designed for reliable leakage determination crankcase ventilation system.

• - zweiten Schritt die Messung des Kurbelgehäusedruckes über einen Zeitraum erfolgt, wobei jedem Messzeitpunkt des Zeitraumes der zu diesem Messzeitpunkt gemessene Kurbelgehäusedruck als Druckwert zugeordnet wird, wobei eine Kennlinie mit Hilfe der entsprechenden Messzeitpunkte und zugeordneten Druckwerten ermittelt wird,
• - dritten Schritt jeder Druckwert mit einem IO-Sollwert verglichen wird.

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 each having a closing element connected directly to the suction line, and having a swingable diaphragm, and wherein in a first step, the closed circuit of the crankcase ventilation system by closing the with the suction immediately connected connection lines is brought about,

• second step, the measurement of the crankcase pressure takes place over a period of time, the measured crankcase pressure 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, each pressure value is compared with an IO setpoint.

In a tight crankcase ventilation system, a constant pressure in the crankcase is adjusted by means of the pressure control element. If there is a leakage or a leakage point in the crankcase ventilation system, there may be a vibration of the oscillatory diaphragm, wherein the pressure in the crankcase is excited to vibrate. The advantage of the method according to the invention can be seen in the fact that the determination of the leakage is possible both during idling operation of the internal combustion engine and in partial load operation of the internal combustion engine.

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.

• 1 in einer schematischen Darstellung eine Verbrennungskraftmaschine mit einem erfindungsgemäßen Kurbelgehäuseentlüftungssystem, und
• 2 in einem p-t-Diagramm einen Druckverlauf eines Kurbelgehäusedrucks bei leckagefreiem Zustand des Kurbelgehäuseentlüftungssystems und einen Druckverlauf des Kurbelgehäusedrucks bei Leckagezustand des Kurbelgehäuseentlüftungssystems.

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 according to the invention, and
• 2 in a pt diagram, a pressure curve of a crankcase pressure at leak-free condition of the crankcase ventilation system and a pressure curve of the crankcase pressure at leakage condition of the crankcase ventilation system.

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 along a longitudinal axis of the cylinder liner axially moving, not shown, received piston. These pistons are each with the help of one not closer shown connecting rod mounted on a crankshaft, not shown, of the reciprocating engine, wherein the crankshaft is rotatably received in the crankcase. At the crankshaft is usually a torque decrease to drive a drive shaft, not shown, for example. A motor vehicle. The axial movement of the piston is a so-called tilting movement of the piston placed, since the piston is mounted on a side facing away from the crankshaft end of the connecting rod with the aid of a piston not shown in detail 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 so-called poppet valves as 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. With the help of the piston, a combustion chamber of the reciprocating engine is configured, sucked in the fresh air, compressed, burned and ultimately ejected from it. 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 absorbs and environmentally friendly, for example. By supply to 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 5 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 p _K 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 of the internal combustion engine 1 is the pressure control element 15 on the cylinder head 3 positioned.

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 the 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 portion of the intake fresh air in the form of purge air through 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 for determining the crankcase pressure p _K intended.

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 to overflow of gas through 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. 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. Likewise, the check valve of the fifth connection line 17 closed. 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.

The crankcase ventilation system according to the invention 5 includes a vibratable membrane to determine leakage. The oscillatory membrane could be in the area of the pressure sensor 18 be positioned. In the present embodiment, the membrane corresponds to a membrane of the pressure control element 15 , which is constructed in the form of a diaphragm-spring control element. In other words, that means the pressure control element 15 a vibratable diaphragm and a return spring, usually in the form of a spiral spring, for acting on a closing element, not shown, of the pressure control element 15 includes. Unless the crankcase ventilation system 5 is leak-free, becomes a constant crankcase pressure p _K adjusted. However, there is a leak in the crankcase system 5 Before, the membrane is in particular in idle mode and in partial load operation of the internal combustion engine 1 Pressed differently and she begins to swing. One consequence of this vibration is a swinging crankcase pressure p _K that with the pressure sensor 18 is detected.

With the aid of a corresponding evaluation system, which preferably in a control unit of the internal combustion engine, not shown 1 is deposited with the pressure sensor 18 determined values of the crankcase pressure p _K recorded and evaluated. This is for everyone over the period T measured crankcase pressures pK a pressure value p assigned in 2 are in a pt-diagram, in other words that in the diagram pressures over a certain time are plotted, a first characteristic curve K _iO the crankcase pressure p _K in leak-free condition of the crankcase ventilation system 5 in the Comparison with a second characteristic K _niO the crankcase pressure p _K in leakage condition of the crankcase ventilation system 5 illustrated. The first characteristic K _iO is shown by a solid line, the second characteristic K _niO is shown in phantom. Each characteristic K _iO . K _niO is made up of several value pairs, with each measurement time point t of the period T on at this time of measurement t measured crankcase pressure p _K as pressure value p is assigned.

The measurement of the crankcase pressure takes place over the period T whose measurement start and end can be flexible, with a period T from at most 60 Seconds to strive for.

The course of the first characteristic K _iO the crankcase pressure p _K in leak-free condition of the crankcase ventilation system 5 has pressure oscillations with a bandwidth B around a constant average pressure value p _Km on. The course of the characteristic K _iO corresponds to a constant crankcase pressure p _K , in an intact, ie no leakage crankcase ventilation system 5 ,

In comparison, the course of the first characteristic curve K _niO the crankcase pressure p _K in leakage condition of the crankcase ventilation system 5 Pressure _oscillations around a further average pressure value p _Knio , which is clearly from the constant average pressure value p _Km different.

For fault diagnosis is a so-called IO setpoint p _KiO stored in the control unit, with which the determined pressure value p depending on its measuring time t is compared. The adjustment takes place over a longer period of time T , which in a period of maximum 60 Seconds. Be in the period T several deviations from the IO setpoint p _KiO found, there is a leaking crankcase ventilation system 5 in front.

In another embodiment, the over the period T measured crankcase pressures p _K summed and an average formed. If this mean value is below the IO setpoint p _KiO This also indicates a leaking crankcase ventilation system 5 out.

The result of the method according to the invention, ie there is a leakage-prone or an intact, ie dense, crankcase ventilation system 5 Before, can be displayed or output in any form, for example. In a display of the motor vehicle.

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

p _K

crankcase pressure

p _KiO

IO setpoint

p _Km

Average pressure value

p _KniO

further average pressure value

t

Measuring time

B

bandwidth

K _iO

Characteristic intact crankcase ventilation system

K _niO

Characteristic leakage crankcase ventilation system

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

• US 20150090204 A1 [0004]
• DE 102013218313 A1 [0005]

Claims (9)

A crankcase ventilation system, wherein the crankcase ventilation system (5) is assigned to an internal combustion engine (1), and the crankcase ventilation system (5) has at least one connecting line (12; 16; 17) which has a separating unit (11 ) with a suction line (13) of an intake tract (8) of the internal combustion engine (1) is designed to flow through connectable, and with a pressure control element (15) for controlling a pressure (p _K ) in the crankcase (2), and with a pressure sensor (18) in which a pressure (p _K ) in the crankcase (2) is designed such that it can be received, and in which the crankcase ventilation system (5) connects each connecting line (12, 16) directly connected to the suction line (13) to a closing element (20, 19) ), characterized in that the crankcase ventilation system (5) for detecting a leaking crank Ventilation system (5) has a vibratable membrane. Crankcase ventilation system according to Claim 1 , characterized in that the oscillatable membrane corresponds to a membrane of the pressure regulating element (15). Crankcase ventilation system according to Claim 1 or 2 , characterized in that the membrane in the region of the pressure sensor (18) is arranged. Crankcase ventilation system according to one of the preceding claims, characterized in that the closing element (20; 19) is designed in the form of a non-return element. Internal combustion engine, comprising a crankcase (2) and an intake tract (6), wherein the crankcase (2) is a crankcase ventilation system (5) according to any one of Claims 1 to 4 having. Method for leakage diagnosis for a crankcase ventilation system, wherein the crankcase ventilation system (5) is assigned to an internal combustion engine (1), and the crankcase ventilation system (5) has at least one connecting line (12; 16; 17) which is connected to a crankcase (2) of the internal combustion engine (1 ) associated with a suction line (13) an intake tract (8) of the internal combustion engine (1) is designed to flow through, and with a pressure control element (15) for regulating a pressure (p _K ) in the crankcase (2), and with a pressure sensor (18) which receives the crankcase pressure (p _K ), and in which the crankcase ventilation system (5) has a closing element (20, 19) connected to the suction line (13) for directing a closed circuit , and with a vibratable membrane, characterized in that - in a first step, the g closed circuit of the crankcase ventilation system (5) is brought about by closing the connecting lines (12, 16) directly connected to the suction line (13), - in a second step measuring the crankcase pressure (p _K ) over a period of time (T), each one Measuring time (t) of the period (T) of the measured at this measurement time (t) crankcase pressure (p _K ) is assigned as the pressure value (p), wherein a characteristic (K _iO ; K _niO ) is determined with the aid of the corresponding measurement times (t) and associated pressure values (p), and - in a third step, each pressure value (p) is compared with an IO setpoint. Method according to Claim 6 , characterized in that over a certain period of time (T) the crankcase pressure (p _K ) is recorded and an average _pressure value (p _Km ; p _KniO ) is determined, which is compared with the IO setpoint. Method according to Claim 7 , characterized in that the period (T) comprises at most 60 seconds. Method according to one of Claims 6 to 8th , characterized in that the closing element (20; 19) functions in the form of a self-regulating non-return valve.

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