Method for testing a crankcase ventilation system of an internal combustion engine

Abstract

Method for testing a crankcase ventilation system of an internal combustion engine, which • an internal combustion engine (1) with at least one combustion chamber (6) and one crankcase (9), • a fresh gas line (10) for supplying fresh gas to the at least one combustion chamber (6) and • a vent line (17) leading from the crankcase (9) to the fresh gas line (10) and in which a pressure regulating valve (23) is integrated, wherein an actual value regarding the opening state of the pressure regulating valve (23) is compared with a setpoint value, characterized in that a malfunction of the crankcase ventilation system with regard to the gas pressure in the vent line (17) is detected if there is a defined deviation between the actual value and the setpoint value.

Description

[0001] The invention relates to a method for testing a crankcase ventilation system of an internal combustion engine with respect to the gas pressure in a ventilation line of the crankcase ventilation system.

[0002] Internal combustion engines intended to drive a motor vehicle generally have a so-called closed crankcase ventilation system, through which blow-by gases that have flowed from the combustion chambers into the crankcase of an internal combustion engine of the internal combustion engine are discharged and fed into the fresh gas line of the internal combustion engine.

[0003] Since a leak in such a crankcase ventilation system could lead to the escape of blow-by gases and thus the release of environmentally harmful substances into the environment, it is often required by law to detect such leaks.

[0004] It is known to use pressure sensors installed in the crankcase ventilation system, and especially in the crankcase itself, for such leak testing. Since these pressure sensors are exposed to the chemically aggressive blowby gases, they must be designed to be resistant, which leads to relatively high costs. Furthermore, there is a risk that the pressure sensors will freeze at very low ambient temperatures, which means that special approval conditions are required for the reliable use of the pressure sensors.

[0005] DE 10 2012 200 015 A1 discloses a filter device for a crankcase ventilation system of an internal combustion engine, wherein a filter element of the filter device can be bypassed via a bypass line. A bypass valve is integrated into the bypass line, the valve position of which can be determined by means of a position sensor. A pressure sensor can also be integrated into the filter device, which determines the gas pressure upstream and / or downstream of the filter element. The filter device further comprises a pressure control valve.

[0006] DE 10 2011 112 584 B4 describes a pressure control valve designed as a diaphragm valve for a crankcase ventilation system of an internal combustion engine, wherein a sensor device is provided for detecting an actuating movement of the diaphragm of the pressure control valve. By evaluating the signals from the sensor device, a malfunction of the pressure control valve can be detected.

[0007] The invention is based on the object of providing a functionally reliable leak test for a crankcase ventilation system in the simplest possible way.

[0008] This problem is solved by the subject matter of the patent claims.

[0009] According to the invention, a method is provided for testing a crankcase ventilation system of an internal combustion engine, wherein the internal combustion engine comprises at least one internal combustion engine having at least one combustion chamber, preferably a plurality of combustion chambers, and a crankcase, a fresh gas line for supplying fresh gas to the at least one combustion chamber, and a ventilation line leading from the crankcase to the fresh gas line and in which a pressure control valve is integrated.

[0010] During operation of the internal combustion engine, combustion processes take place in at least one combustion chamber, resulting in cyclical volume changes in the at least one combustion chamber, wherein the volume changes each result from a movement of a piston delimiting the combustion chamber. The (each) piston is drive-connected to an output shaft of the internal combustion engine, which is rotatably mounted within the crankcase. The crankcase is separated from the combustion chamber by the piston, however, this separation is not complete due to the mobility of the piston, and consequently, an overflow of gas from the combustion chamber into the crankcase is possible via a gap between the piston and a wall guiding its movement.Preferably, it can be provided that the internal combustion engine is designed as a reciprocating piston engine, so that the (each) piston is guided in a linearly movable manner in a cylinder opening which delimits the combustion chamber together with the piston, this linear movement being transmitted via a connecting rod to the output shaft designed as a crankshaft.

[0011] The method according to the invention provides that an actual value with regard to the opening state of the pressure control valve is compared with a target value and, in the event of a defined or specified deviation between the actual value and the target value, a malfunction of the crankcase ventilation system with regard to the gas pressure in the ventilation line is detected.

[0012] An internal combustion engine according to the invention accordingly comprises at least the combustion engine with the at least one combustion chamber and the crankcase, the fresh gas line for supplying fresh gas to the at least one combustion chamber, the vent line leading from the crankcase to the fresh gas line and into which the pressure control valve is integrated with an opening state sensor configured to determine the actual value regarding the opening state of the pressure control valve. Furthermore, a control device receiving a signal from the opening state sensor is provided, wherein the control device is configured to automatically carry out a method according to the invention.

[0013] For this purpose, the control device can comprise a memory, wherein a computer program is stored in the memory, the execution of which enables a method according to the invention to be carried out. In this regard, the invention also relates to a corresponding control device and a computer program with a program code for executing a method according to the invention when the computer program is executed on a computer.

[0014] While in the pressure control valve according to DE 10 2011 112 584 B4, a check of the opening state of the pressure control valve by means of the sensor device therein is provided solely for a functional test of the pressure control valve, the opening state of the pressure control valve is checked in the method according to the invention to check the gas pressure in the ventilation line, whereby in particular a leak or a lack of tightness in the crankcase ventilation system can be detected, which can be caused in particular by a hole in a hose line that is part of the ventilation line or by a loose connection of such a hose line to another component of the crankcase ventilation system. Alternatively or additionally, the method according to the invention can also detect, for example, a blockage in the ventilation line.

[0015] The invention is based on the idea that the opening state of the pressure control valve is directly dependent on the gas pressure in the ventilation line. Consequently, in a crankcase ventilation system that is fault-free with regard to the gas pressure in the ventilation line and thus, in particular, exhibits neither leaks nor blockages, this leads to defined opening states of the pressure control valve depending on the specific operating states of the internal combustion engine. This makes it possible to define these corresponding opening states as target values, for which purpose, in particular, a corresponding operating map can be determined in advance, in which the opening states are specified as a function of the operating states of the internal combustion engine.The operating states of the internal combustion engine can be defined, in particular, by the load and / or the speed at which the internal combustion engine is operated, and / or the pressure of the fresh gas in the fresh gas line immediately upstream of the internal combustion engine. The target values ​​can be determined by measurement during operation of the internal combustion engine or during operation of a corresponding (reference) internal combustion engine with a known-to-be faultless crankcase ventilation system. However, the target values ​​can also be determined using a model, so that opening states of the pressure control valve suitable for the various operating states can be determined purely mathematically based on defined values ​​relating to various operating states of the internal combustion engine and the design of the pressure control valve.According to the invention, a setpoint relating to a specific operating state of the internal combustion engine can be compared with a correspondingly determined actual value. If a defined deviation occurs between the actual value and the setpoint, a malfunction can be assumed regarding the gas pressure in the vent line. The error-related deviation between the actual value and the setpoint can also lead to a defined (measured) limit value or a mechanical stop being reached regarding the opening state of the pressure control valve, which would otherwise not be the case (i.e., without the malfunction).

[0016] In principle, it can be provided that a malfunction of the crankcase ventilation system is assumed as soon as a deviation between the actual value and the target value is detected. Preferably, however, it can be provided that this only occurs when such a detected deviation corresponds at least to a defined minimum deviation. This makes it possible to compensate, in particular, for tolerance-related measurement errors regarding the determination of the actual value of the opening state, but also for determination errors regarding the target value, which can also be present as tolerance-related measurement errors or result from inaccuracies due to the modeling of the target values. This can prevent such deviations from being incorrectly identified as a malfunction of the crankcase ventilation system.

[0017] Preferably, the opening state of the pressure control valve can be determined based on the position of a valve element of the pressure control valve. The opening state sensor of an internal combustion engine according to the invention can therefore be configured as a position sensor associated with a valve element of the pressure control valve. The position sensor can, in particular, be configured to measure the distance and / or acceleration of a movement of the valve element and derive a position of the valve element therefrom.

[0018] Furthermore, it can preferably be provided that the comparison of the actual value with the target value, and thus the test for a malfunction of the crankcase ventilation system, is carried out continuously during operation of the internal combustion engine, so that a malfunction can be detected as quickly as possible. "Continuous" is understood to mean a comparison of the actual value with the target value if this is always carried out when it is technically expedient. An interruption of the comparison, and thus the test for a malfunction of the crankcase ventilation system, should therefore not be carried out, even though the comparison or test would be technically expedient.

[0019] Interrupting or not performing the comparison or test might be advisable if the pressures on both sides of the pressure control valve are essentially the same due to the operating state of the internal combustion engine. This could be the case, for example, when the internal combustion engine is operating at so-called full intake manifold load, in which fresh gas is supplied to the internal combustion engine without compression and with no or minimal throttling. The comparison between the actual value and the target value could then produce the same result with or without a malfunction of the crankcase ventilation system. This could consequently lead to the comparison leading to the false conclusion that no malfunction is present.

[0020] Preferably, therefore, it can be provided that the comparison is interrupted or not carried out if, due to the operation of the internal combustion engine, essentially the same pressures occur in the vent line upstream and downstream of the pressure control valve (includes deviations of up to a maximum of 10%, preferably up to a maximum of 5% (the basis being the lower value)). Accordingly, it can preferably be provided that the comparison is carried out, preferably always carried out, when compressed fresh gas and / or fresh gas actively throttled by means of a throttle device is supplied to the internal combustion engine, because then a sufficiently large pressure difference can exist across the pressure control valve.

[0021] For supplying compressed fresh gas, an internal combustion engine according to the invention or one used within the framework of a method according to the invention may comprise a fresh gas compressor integrated into the fresh gas line. This fresh gas compressor may preferably be part of an exhaust gas turbocharger.

[0022] In such an internal combustion engine, it can also be provided that a first branch of the vent line opens into a section of the fresh gas line located upstream of the fresh gas compressor, and a second branch of the vent line opens into a section of the fresh gas line located downstream of the fresh gas compressor. A shut-off valve is integrated into each of the branches and is designed to close the respective branch in the event of excess pressure on the side of the respectively associated section of the fresh gas line. The terms "upstream" and "downstream" refer to a flow of fresh gas in the fresh gas line toward the internal combustion engine.Such a design of the internal combustion engine enables crankcase ventilation both in aspiration mode, in which essentially no compression of the fresh gas is achieved by the fresh gas compressor, and in boost pressure mode of the internal combustion engine, in which a significant compression of the fresh gas is achieved by the fresh gas compressor. Due to the arrangement of its outlet on the intake side of the fresh gas compressor, the first branch can ensure a sufficient pressure gradient across the vent line during boost pressure mode, while this can be the case via the second branch in aspiration mode.This applies in particular if the section of the fresh gas line into which the second line of the vent line opens is located between a throttle valve integrated into the fresh gas line, in particular in a design as a throttle flap, and the combustion engine, because then a sufficiently large negative pressure can be realized in the region of the opening of the second line of the vent line by means of the throttle valve.

[0023] According to a preferred development of such an internal combustion engine according to the invention and usable according to the invention, the pressure relief valve can be arranged upstream (with respect to a flow of gas via the vent line, starting from the crankcase of the internal combustion engine in the direction of the fresh gas line) of a branching of the vent line into the two lines. This can result in an advantageous structural design of the internal combustion engine.

[0024] The internal combustion engine of an internal combustion engine according to the invention can, in particular, be a (self-igniting and quality-controlled) diesel engine or a (spark-ignition and quantity-controlled) gasoline engine, or a functional combination thereof, e.g., a homogeneous compression ignition internal combustion engine. The internal combustion engine can be operated with both liquid fuel (i.e., diesel or gasoline) and a gaseous fuel (in particular, natural gas, LNG, or LPG).

[0025] The invention further relates to a motor vehicle, in particular a wheel-based and non-rail-based motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine of the internal combustion engine can be provided, in particular, for the (direct or indirect) provision of the traction drive power for the motor vehicle.

[0026] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. The drawings show, in simplified form: Fig. 1: an internal combustion engine according to the invention and usable within the framework of a method according to the invention according to a first embodiment and Fig. 2: an internal combustion engine according to the invention and usable within the framework of a method according to the invention according to a second embodiment.

[0027] The Fig. The internal combustion engine shown in Figure 1 comprises a (reciprocating piston) combustion engine 1 with a cylinder crankcase 2 forming one or more cylinder openings 3, in each of which a piston 4 is guided for linear movement. The cylinder openings 3, together with the pistons 4 and a cylinder head 5, each define a combustion chamber 6. Fresh gas (mainly air) can be burned together with fuel in the combustion chambers 6. For this purpose, the fuel can be introduced directly into the combustion chambers 6 by means of a fuel injector (not shown). The combustion of fuel-fresh gas mixture quantities in the combustion chambers 6 leads to cyclical upward and downward movements of the pistons 4, which are transmitted via connecting rods 7 to a crankshaft 8, whereby the crankshaft 8 is driven in rotation.The crankshaft 8 is rotatably mounted in the cylinder crankcase 2, and the section to which the connecting rods 7 are connected is arranged in a crank chamber 9 defined by the cylinder crankcase 2. A lower section of the cylinder crankcase 2 forms an oil pan, which is intended for the reception and temporary storage of oil used for the lubrication and cooling of the moving parts of the internal combustion engine 1.

[0028] The fresh gas is supplied to the combustion engine 1 via a fresh gas line 10. For this purpose, air is drawn in from the ambient air, cleaned in an air filter 11, and then passed through a fresh gas compressor 12, which is part of an exhaust gas turbocharger. The fresh gas can be compressed by the fresh gas compressor 12 and is then supplied to the combustion chambers 6. The fresh gas compressor 12 is driven by an exhaust gas turbine 13 of the exhaust gas turbocharger, which is integrated into an exhaust line 14 of the internal combustion engine. Exhaust gas produced during the combustion of the fuel-fresh gas mixture in the combustion chambers 6 of the internal combustion engine 1 is discharged from the internal combustion engine 1 via the exhaust line 14 and flows through the exhaust gas turbine 13. This leads, in a known manner, to a rotating drive of a turbine impeller which is connected in a rotationally fixed manner to a compressor impeller (not shown) of the fresh gas compressor 12 via a shaft.The rotating drive of the turbine impeller is thus transferred to the compressor impeller.

[0029] Downstream of the fresh gas compressor 12, a throttle device in the form of a throttle valve 16, which can be controlled by means of a control device 15, is integrated into the fresh gas line 10.

[0030] The internal combustion engine further comprises a crankcase ventilation system, by means of which blowby gases can be removed from the crankcase 9 of the internal combustion engine 1 and introduced into the fresh gas line 10. This prevents overpressure in the crankcase 9 during operation of the internal combustion engine 1 due to blowby gases entering it. Due to the high pressure temporarily prevailing in the combustion chambers 6, the blowby gases flow through the only incompletely sealed annular gaps formed between the pistons 4 and the walls of the cylinder openings 3.

[0031] The crankcase ventilation system comprises a ventilation line 17, which is partially integrated into the cylinder crankcase 2 and the cylinder head 5 of the internal combustion engine 1. The ventilation line 17 branches off from a section of the crankcase 9 located above the oil level and opens into the fresh gas line 10, with the ventilation line 17 branching into a first line 17a and a second line 17b. The first branch 17a opens into a section of the fresh gas branch 10 located upstream of the fresh gas compressor 12 and the second branch 17b opens into a section of the fresh gas branch 10 located downstream of the fresh gas compressor 12 and also downstream of the throttle valve 16. A check valve 18 is integrated into each of the branches 17a, 17b of the vent line 17, wherein these check valves 18 each close in the event of an overpressure on their side facing the fresh gas branch 10.These check valves 18 ensure that the crank chamber 9 is in fluid communication with the fresh gas line 10 via the vent line 17 via one of the lines 17a, 17b only when there is a negative pressure in the area of ​​the corresponding opening of this line 17a, 17b compared to the gas pressure in the crank chamber 9.

[0032] The crankcase ventilation system further comprises a pressure equalization line 19, which branches off from the fresh gas line 10, specifically from a section immediately downstream and thus on the high-pressure side of the fresh gas compressor 12, and opens into the crankcase 9. Also integrated into the pressure equalization line 19 are a check valve 18, which opens in the event of excess pressure on the side facing the crankcase 9, as well as a throttle 20. Fresh gas can be transferred into the crankcase 9 via the pressure equalization line 19, thereby enabling the crankcase 9 to be vented without reducing the gas pressure in the crankcase 9.

[0033] An oil separator 21 is integrated into the vent line 17. It serves to separate oil droplets from the blowby gases conducted via the vent line 17. This separated oil is returned to the crankcase 9 via a return line 22. A pressure control valve 23 is also integrated into the vent line 17 downstream of the oil separator 21 and also upstream of the branching of the vent line 17 into the two branches 17a, 17b. The basic functioning of the pressure control valve 23 and possible designs for implementing this functioning are generally known. In this regard, reference can be made, for example, to the corresponding disclosure of DE 102011 112 584 B4.The pressure control valve 23 serves to set a defined gas pressure on the upstream side of the vent line 17, which essentially corresponds to the gas pressure in the crankcase 9, and to maintain this defined gas pressure as much as possible despite a strongly varying gas pressure on the downstream side of the vent line 17. The defined gas pressure in the crankcase 9 can, for example, be a relatively low negative pressure compared to the ambient pressure of approximately 70 hPa. In contrast, a significantly greater negative pressure relative to the ambient pressure can prevail in the fresh gas line 10. This negative pressure can, for example, temporarily amount to 700 hPa.The pressure control valve 23 prevents a gas pressure in the crank chamber 9 that is significantly higher than the defined one, which could otherwise lead to contaminated air from the environment being sucked into the crank chamber 9 via seals of the cylinder crankcase 2.

[0034] According to a preferred embodiment, the pressure control valve 23 can have the following structure (not shown): a valve body is connected to a diaphragm, which is subjected on one side to the gas pressure of the blowby gas coming from the crankcase 9. This action on the diaphragm is counteracted by a spring element whose spring preload can be adjustable. The side of the diaphragm subjected to the blowby gas coming from the crankcase 9 is connected via a valve opening to the section of the vent line 17 located downstream of the pressure control valve 23. Depending on a deformation of the diaphragm, the valve body connected to the diaphragm closes the valve opening or opens it to a variable extent. The higher the gas pressure of the blowby gas acting on the diaphragm, the more the valve body closes the valve opening.Consequently, a passive control of the gas pressure of the blowby gas acting on the membrane and thus also of the gas pressure in the crank chamber 9 can be achieved, since the pressure control valve 23 is closed further, the higher the pressure gradient from the crank chamber 9 to the fresh gas line 10 is.

[0035] A position sensor 24 is assigned to the valve body of the pressure control valve 23, by means of which an actual value regarding the opening state of the valve body and thus of the pressure control valve 23 can be determined. The position sensor 24 is connected to the control device 15 in a signal-conducting manner. This determination of the opening state serves to monitor the crankcase ventilation system for a malfunction that (also) affects the gas pressure in the ventilation line 17. For this purpose, a characteristic map is stored in the control device 15 of the internal combustion engine, in which desired values ​​regarding the opening state of the pressure control valve 23 are entered as a function of all operating states in which the internal combustion engine can be operated.By comparing the determined actual value with the stored target value, a corresponding malfunction of the crankcase ventilation system can be concluded if a defined deviation between these values ​​exists. A corresponding evaluation is carried out automatically by the control device 15, whereby upon detection of a malfunction, an error message can be generated and stored in an error memory of the control device 15. If, for example, there is a leak in one of the branches 17a, 17b of the ventilation line 17, this results in too low a vacuum or too high a pressure on the corresponding side of the pressure control valve 23, causing it to open wider than expected for the corresponding operating state based on the stored target values.

[0036] The Fig. The embodiment of an internal combustion engine according to the invention and usable according to the invention shown in Figure 2 differs from that according to the Fig. 1 essentially consists in the fact that the pressure equalization line 19 branches off from the fresh gas line 10 upstream of the fresh gas compressor 12, specifically from the clean air side of the air filter 11. Furthermore, a charge air cooler 25 is integrated into the fresh gas line 10 downstream of the fresh gas compressor 12 and downstream of the throttle valve 16. This charge air cooler 25 serves to recool the fresh gas heated as a result of compression by the fresh gas compressor 12.

[0037] In an embodiment not shown, the charge air cooler 15 is integrated into the fresh gas line 10 downstream of the fresh gas compressor 12 and upstream of the throttle valve 16. List of reference symbols 1 combustion engine 2 cylinder crankcases 3 Cylinder opening 4 pistons 5 cylinder head 6 combustion chamber 7 connecting rods 8 Crankshaft 9 Crankcase 10 Fresh gas line 11 Air filter 12 fresh gas compressors 13 Exhaust turbine 14 Exhaust system 15 Control device 16 Throttle valve 17 Ventilation line 17a first branch of the vent line 17b second branch of the vent line 18 Check valve 19 Pressure equalization line 20 Throttle 21 oil separators 22 Return line 23 Pressure control valve 24 Position sensor 25 intercoolers QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] DE 10 2012 200 015 A1

[0005] DE 10 2011 112 584 B4 [0006, 0014, 0033]

Claims

[1] Method for testing a crankcase ventilation system of an internal combustion engine, which • an internal combustion engine (1) with at least one combustion chamber (6) and a crank chamber (9), • a fresh gas line (10) for supplying fresh gas to the at least one combustion chamber (6) and • a vent line (17) which leads from the crank chamber (9) to the fresh gas line (10) and into which a pressure control valve (23) is integrated, wherein an actual value relating to the opening state of the pressure control valve (23) is compared with a target value, characterized by that if there is a defined deviation between the actual value and the target value, a malfunction of the crankcase ventilation system with regard to the gas pressure in the ventilation line (17) is detected. [2] Method according to claim 1, characterized by that the opening state of the pressure control valve (23) is determined based on a position of a valve element of the pressure control valve (23). [3] Method according to claim 1 or 2, characterized by that the comparison of the actual value with the target value is carried out continuously during operation of the internal combustion engine (1). [4] Method according to one of the preceding claims, characterized by that the comparison is interrupted when, due to the operation of the internal combustion engine, essentially equal pressures occur in the vent line (17) upstream and downstream of the pressure control valve (23). [5] Internal combustion engine, the • an internal combustion engine (1) with at least one combustion chamber (6) and a crank chamber (9), • a fresh gas line (10) for supplying fresh gas to the at least one combustion chamber (6), • a vent line (17) leading from the crank chamber (9) to the fresh gas line (10) and in which a pressure control valve (23) with an opening state sensor is integrated, and • a control device (15) which receives a signal from the opening state sensor, characterized by that the control device (15) is designed to carry out a method according to one of claims 1 or 2 in an automated manner. [6] Internal combustion engine according to claim 5, characterized by that the opening state sensor is designed as a position sensor (24) associated with a valve element of the pressure control valve (23). [7] Internal combustion engine according to claim 5 or 6, characterized byin that a fresh gas compressor (12) is integrated into the fresh gas line (10), wherein a first line (17a) of the vent line (17) opens into a section of the fresh gas line (10) located upstream of the fresh gas compressor (12) and a second line (17b) of the vent line (17) opens into a section of the fresh gas line (10) located downstream of the fresh gas compressor (12), wherein a shut-off valve is integrated into each of the lines (17a, 17b), which is designed to close the respective line in the event of an overpressure on the side of the respectively assigned section of the fresh gas line (10). [8] Internal combustion engine according to claim 7, characterized by that the pressure relief valve (23) is arranged upstream of a branching of the vent line (17) into the strands (17a, 17b). [9] Control device (15) with a memory, wherein a computer program is stored in the memory, during the execution of which a method according to one of claims 1 to 4 can be carried out. [10] Computer program with a program code for carrying out a method according to one of claims 1 to 4 when the computer program is executed on a computer.

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