SYSTEM AND METHOD FOR DIAGNOSING A CRANKCASE VENTILATION SYSTEM OF AN INTERNAL COMBUSTION ENGINE

Abstract

A system for diagnosing a crankcase ventilation system of an internal combustion engine. The system includes an internal combustion engine with at least one combustion chamber. The combustion chamber is bounded by a cylinder head, a cylinder in an engine block, and a piston. The piston is connected via a connecting rod to a crankshaft, which is disposed in a crankcase. An air supply system feeds fresh air into the combustion chamber of the internal combustion engine. At least one aeration line connects the air supply system to the crankcase. At least one vent line, which is different from the aeration line, connect the crankcase to the air supply system. A pressure sensor is disposed in the crankcase or the aeration line. A method for diagnosing a crankcase ventilation system and a control device for carrying out such a method are also provided.

Claims

1. A system to diagnose a crankcase ventilation system of an internal combustion engine, comprising the system comprising: an internal combustion engine with at least one combustion chamber, wherein the combustion chamber is bounded by a cylinder head, a cylinder in an engine block, and a piston, wherein the piston is connected via a connecting rod to a crankshaft, which is disposed in a crankcase; an air supply system for feeding fresh air into the combustion chamber of the internal combustion engine; at least one aeration line connecting the air supply system to the crankcase; at least one vent line, which is different from the aeration line and connects the crankcase to the air supply system; and a pressure sensor disposed in the crankcase or the aeration line.

2. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 1, wherein the internal combustion engine is designed as an internal combustion engine turbocharged via an exhaust gas turbocharger.

3. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 2, wherein the aeration line branches off from the air supply system upstream of a compressor of the exhaust gas turbocharger, and wherein the pressure sensor is disposed in or on the aeration line.

4. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 3, wherein a throttle is disposed in the aeration line upstream of the pressure sensor.

5. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 2, further comprising a Venturi nozzle disposed in the vent line.

6. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 5, wherein the Venturi nozzle is part of a suction jet pump that conveys the gas from the crankcase into an intake line of the air supply system.

7. The system for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 2, wherein the vent line runs through a suction jet pump such that a motive flow generated by the turbocharger compressor is used to generate a vacuum and thus to generate an air flow through the vent line.

8. The system for diagnosing a crankcase ventilation of an internal combustion engine according to claim 7, further comprising a second vent line that connects an intake path of the compressor of the exhaust gas turbocharger or the intake manifold to the crankcase.

9. A method for diagnosing a crankcase ventilation system of an internal combustion engine comprising the system for diagnosis according to claim 2, the method comprising: operating the internal combustion engine at an operating point at which a boost pressure is built up by the compressor of the exhaust gas turbocharger; and evaluating a change in the pressure in the crankcase or in the aeration line downstream of a throttle in response to the boost pressure build-up.

10. The method for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 9, wherein, during the boost pressure build-up, starting from a substantially constant vacuum in the crankcase, an increase in the pressure in the crankcase or in the aeration line downstream of the throttle and a drop in the pressure, following the increase in pressure, in the crankcase or in the aeration line downstream of the throttle are evaluated for the purpose of diagnosing the crankcase ventilation system.

11. The method for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 9, wherein, when the boost pressure builds up above a threshold value, starting from a substantially constant vacuum in the crankcase, a pressure maximum and a subsequent pressure minimum of the pressure in the crankcase or in the aeration line downstream of the throttle are determined and a functioning of the crankcase ventilation system is deduced from the pressure difference between the maximum pressure and the minimum pressure.

12. The method for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 9, wherein a Venturi nozzle, with which a vacuum is generated in the crankcase, is disposed in the vent line, and wherein a functioning of the crankcase ventilation system is determined from a decrease in pressure in the crankcase.

13. The method for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 9, wherein a volume flow through the aeration line is evaluated during a boost pressure build-up and a functioning of the crankcase ventilation system is determined from the volume flow.

14. The method for diagnosing a crankcase ventilation system of an internal combustion engine according to claim 10, wherein a pressure change in the aeration line is evaluated as a function of the pressure build-up in the intake manifold during a boost pressure build-up of the exhaust gas turbocharger.

15. A control device comprising a memory unit and a computing unit, wherein a computer program code is stored in the memory unit, which code, when executed by the computing unit, executes the method according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0031] FIG. 1 shows an example for an internal combustion engine for carrying out a method of the invention for diagnosing a crankcase ventilation system of the internal combustion engine;

[0032] FIG. 2 shows an example for an internal combustion engine for carrying out a method of the invention for diagnosing a crankcase ventilation system of the internal combustion engine; and

[0033] FIG. 3 shows a flowchart for carrying out a method of the invention for diagnosing a crankcase ventilation system of an internal combustion engine.

DETAILED DESCRIPTION

[0034] An example of an internal combustion engine 10 for carrying out a method of the invention for diagnosing a crankcase ventilation system of the internal combustion engine 10 is shown in FIG. 1. Internal combustion engine 10 has an engine block 22 and a cylinder head 24. Internal combustion engine 10 further has at least one combustion chamber 12, which is bounded by cylinder head 24, engine block 22, and a piston 14. Preferably, internal combustion engine 10 has a plurality of combustion chambers 12. Piston 14 is connected via a connecting rod 16 to a crankshaft 18, which converts an oscillating movement of piston 14 into a rotary movement. Crankshaft 18 is surrounded by a crankcase 20, which is connected to engine block 22 of internal combustion engine 10.

[0035] Internal combustion engine 10 is connected on the intake side to an air supply system 30, via which fresh air can be supplied to combustion chamber 12 of internal combustion engine 10. Air supply system 30 comprises an air filter 34 for filtering the intake air. Air supply system 30 further comprises an intake line 31, which connects air filter 34 to a compressor 36 of an exhaust gas turbocharger 38. Compressor 36 of exhaust gas turbocharger 38 is connected to an inlet of internal combustion engine 10 via an intake manifold 32. A throttle valve 33 is disposed in intake manifold 32 to control the amount of air supplied to combustion chamber 12. Downstream of compressor 36 of exhaust gas turbocharger 38 and upstream of throttle valve 33, a boost pressure sensor 35 is disposed in intake manifold 32 to detect a boost pressure of exhaust gas turbocharger 38. Downstream of the throttle valve and upstream of the inlet of internal combustion engine 10, an intake manifold pressure sensor 37 is disposed in the intake manifold. When throttle valve 33 is fully open, the intake manifold pressure essentially corresponds to the boost pressure of exhaust gas turbocharger 38.

[0036] Internal combustion engine 10 is connected further to an exhaust system via its outlet, wherein a turbine 39 of exhaust gas turbocharger 38 is disposed in the exhaust system, through which an exhaust gas stream of internal combustion engine 10 flows and which drives compressor 36 of exhaust gas turbocharger 38.

[0037] An aeration duct 26 is formed in engine block 22, which duct establishes a fluidic connection between a first region of cylinder head 24 and crankcase 20. Further, a vent duct 28 is formed in engine block 22, which duct fluidically connects crankcase 20 to a second region of cylinder head 24. Provided in crankcase 20 is an oil return 70 via which oil can flow back into an oil pan 73. Further, a first oil separator 72 is disposed in crankcase 20 to prevent oil mist from entering aeration duct 26. In addition, a second oil separator 74 is provided in crankcase 20, which prevents oil mist from entering vent duct 28. In addition, an oil return 78 is formed in engine block 22 to enable oil to flow back into oil pan 73.

[0038] A first flow path is provided for venting crankcase 20, via which path fresh air compressed by compressor 36 of exhaust gas turbocharger 38 can be introduced into crankcase 20 via a purge line 54, an aeration line 56 in cylinder head 24, and aeration duct 26. A check valve 42 is disposed in aeration line 56 to prevent the uncontrolled escape of air from crankcase 20. Further, a throttle 40 can be disposed in aeration line 56 in order to limit the amount of fresh air supplied to crankcase 20. Further, a pressure sensor 52 is disposed in aeration line 56, with which a pressure in aeration line 56 can be detected. Due to the fluidic connection between the aeration line and crankcase 20, a functioning of the crankcase ventilation system can be deduced from the pressure change in aeration line 56.

[0039] In order to remove the air from crankcase 20, a second flow path is provided via which the air from crankcase 20 can be fed to air supply system 30 via vent duct 28 and a vent line 58 in cylinder head 24 of internal combustion engine 10. A pressure control valve 46 is disposed in vent line 58. Vent line 58 has a branch 60 downstream of pressure control valve 46, at which branch vent line 58 splits into a first section 62, which is connected to intake line 31 of the internal combustion engine via a suction jet pump 44, and into a second section 64, which is connected to intake manifold 32 of air supply system 30. In this case, a check valve 50 is disposed in first section 62, which prevents fresh air from flowing from intake line 31 into vent line 58. First section 62 opens into intake line 31 of air supply system 30 at an inlet 66, which is located downstream of air filter 34 and upstream of compressor 36 of exhaust gas turbocharger 38. Further, a check valve 48 is disposed in second section 64, which valve prevents fresh air from flowing from intake manifold 32 into vent line 58. Second section 64 opens into intake manifold 32 of air supply system 30 at a second inlet 68 downstream of throttle valve 33. In this regard, a vent line 58 that has fallen off or is defective has the effect that no or only a small amount of gases can be transported from crankcase 20 in the direction of inlet 66 into intake line 31. As a result, when the boost pressure of exhaust gas turbocharger 38 builds up, no fresh air or a less than expected amount of fresh air would flow into crankcase 20 via aeration line 56 and aeration duct 26. Thus, the evaluation of a volume flow through aeration line 56 can be used to diagnose the functioning of the crankcase ventilation system. Further, a lower negative pressure than expected would occur in aeration line 56 downstream of throttle 40, so that the pressure measured at sensor 52 or a pressure change as a result of a pressure change in intake manifold 32 due to a build-up of boost pressure can also be used to diagnose the functioning of the crankcase ventilation system.

[0040] Further, an additional aeration line can be provided which connects air supply system 30, in particular intake manifold 32 or another section of air supply system 30 downstream of compressor 36 of exhaust gas turbocharger 38, directly, that is to say, without an intermediate suction jet pump 44, to crankcase 20. Such an additional aeration line is favorable because the pressure change in this additional aeration line is not influenced by the negative pressure generation in suction jet pump 44.

[0041] Internal combustion engine 10 is further operatively connected to a fuel supply system. To prevent an uncontrolled escape of fuel vapors from fuel tank 80, an activated carbon filter 88 is provided in which these fuel vapors are captured and bound. Activated carbon filter 88 is connected to intake line 31 of air supply system 30 via a tank vent line 82. To regenerate activated carbon filter 88, a purge air pump 84 is provided, which is disposed in tank vent line 82. Further, a tank vent valve 86 is provided in tank vent line 82 to control the release of the fuel vapor into intake line 31.

[0042] Internal combustion engine 10 is operatively connected to a control device 90, which has a memory unit 92 and a computing unit 94. A computer program code 96 is stored in memory unit 92, which code carries out a method of the invention for diagnosing a crankcase ventilation system when computer program code 96 is executed by computing unit 94 of control device 90.

[0043] A further example of an internal combustion engine 10 for carrying out a method of the invention for diagnosing a crankcase ventilation system of internal combustion engine 10 is shown in FIG. 2. Internal combustion engine 10 has an engine block 22 and a cylinder head 24. Internal combustion engine 10 further has at least one combustion chamber 12, which is bounded by cylinder head 24, engine block 22, and a piston 14. Preferably, internal combustion engine 10 has a plurality of combustion chambers 12. Piston 14 is connected via a connecting rod 16 to a crankshaft 18, which converts an oscillating movement of piston 14 into a rotary movement. Crankshaft 18 is surrounded by a crankcase 20, which is connected to engine block 22 of internal combustion engine 10.

[0044] Internal combustion engine 10 is connected on the intake side to an air supply system 30, via which fresh air can be supplied to combustion chamber 12 of internal combustion engine 10. Air supply system 30 comprises an air filter 34 for filtering the intake air. Air supply system 30 further comprises an intake line 31, which connects air filter 34 to a compressor 36 of an exhaust gas turbocharger 38. Compressor 36 of exhaust gas turbocharger is connected to an inlet of internal combustion engine 10 via an intake manifold 32. A throttle valve 33 is disposed in intake manifold 32 to control the amount of air supplied to combustion chamber 12. Downstream of compressor 36 of exhaust gas turbocharger 38 and upstream of throttle valve 33, a boost pressure sensor 35 is disposed in intake manifold 32 to detect a boost pressure of exhaust gas turbocharger 38. Downstream of the throttle valve and upstream of the inlet of internal combustion engine 10, an intake manifold pressure sensor 37 is disposed in the intake manifold. When throttle valve 33 is fully open, the intake manifold pressure essentially corresponds to the boost pressure of exhaust gas turbocharger 38.

[0045] Internal combustion engine 10 is connected further to an exhaust system via its outlet, wherein a turbine 39 of exhaust gas turbocharger 38 is disposed in the exhaust system, through which an exhaust gas stream of internal combustion engine 10 flows and which drives compressor 36 of exhaust gas turbocharger 38.

[0046] An aeration duct 26 is formed in engine block 22, which duct establishes a fluidic connection between a first region of cylinder head 24 and crankcase 20. Further, a vent duct 28 is formed in engine block 22, which duct fluidically connects crankcase 20 to a second region of cylinder head 24. Provided in crankcase 20 is an oil return 70 via which oil can flow back into an oil pan 73. Further, a first oil separator 72 is disposed in crankcase 20 to prevent oil mist from entering aeration duct 26. In addition, a second oil separator 74 is provided in crankcase 20, which prevents oil mist from entering vent duct 28. In addition, an oil return 78 is formed in engine block 22 to enable oil to flow back into oil pan 73.

[0047] A first flow path is provided for venting crankcase 20, via which path fresh air compressed by compressor 36 of exhaust gas turbocharger 38 can be introduced into crankcase 20 via a purge line 54, an aeration line 56 in cylinder head 24, and aeration duct 26. A check valve 42 is disposed in aeration line 56 to prevent the uncontrolled escape of air from crankcase 20. Further, a throttle 40 can be disposed in aeration line 56 in order to limit the amount of fresh air supplied to crankcase 20.

[0048] In order to remove the air from crankcase 20, a second flow path is provided via which the air from crankcase 20 can be fed to air supply system 30 via vent duct 28 and a vent line 58 in cylinder head 24 of internal combustion engine 10. A pressure control valve 46 is disposed in vent line 58. Vent line 58 has a branch 60 downstream of pressure control valve 46, at which branch vent line 58 splits into a first section 62, which is connected to intake line 31 of the internal combustion engine via a suction jet pump 44, and into a second section 64, which is connected to intake manifold 32 of air supply system 30. In this case, a check valve 50 is disposed in first section 62, which prevents fresh air from flowing from intake line 31 into vent line 58. First section 62 opens into intake line 31 of air supply system 30 at a first inlet 66, which is located downstream of air filter 34 and upstream of compressor 36 of exhaust gas turbocharger 38. Further, a check valve 48 is disposed in second section 64, which valve prevents fresh air from flowing from intake manifold 32 into vent line 58. Second section 64 opens into intake manifold 32 of air supply system 30 at a second inlet 68 downstream of throttle valve 33. A pressure sensor 52 is disposed in crankcase 20, which detects a pressure in crankcase 20. In this regard, a functioning of crankcase ventilation system can be deduced from a change in the pressure in air supply system 30 and a resulting change in the pressure in crankcase 20.

[0049] A vent line 58 that has fallen off or is defective would transport no or only a small amount of gas from crankcase 20 in the direction of inlet 66 into intake line 31. As a result, when the boost pressure of exhaust gas turbocharger 38 builds up in crankcase 20, a vacuum or a lower than expected vacuum would not be created as desired. Suction jet pump 44 can support or increase the formation of negative pressure in crankcase 20, which improves the crankcase ventilation.

[0050] Internal combustion engine 10 is further operatively connected to a fuel supply system. To prevent an uncontrolled escape of fuel vapors from fuel tank 80, an activated carbon filter 88 is provided in which these fuel vapors are captured and bound. Activated carbon filter 88 is connected to intake line 31 of air supply system 30 via a tank vent line 82. To regenerate activated carbon filter 88, a purge air pump 84 is provided, which is disposed in tank vent line 82. Further, a tank vent valve 86 is provided in tank vent line 82 to control the release of the fuel vapor into intake line 31.

[0051] Internal combustion engine 10 is operatively connected to a control device 90, which has a memory unit 92 and a computing unit 94. A computer program code 96 is stored in memory unit 92, which code carries out a method of the invention for diagnosing a crankcase ventilation system when computer program code 96 is executed by computing unit 94 of control device 90.

[0052] FIG. 3 shows a flowchart for carrying out a method of the invention for diagnosing a crankcase ventilation system of an internal combustion engine 10. In a first method step <100>, a temporal change in the pressure Apks in crankcase 20 or a component 22, 24, 26, 28 fluidically connected to crankcase 20 is detected. Further, in a method step <110>, a pressure change ApREF of a reference pressure is detected or an expected change over time ApKsM is modeled for a pressure change in crankcase 20. In a method step <120>, a gradient is formed from the pressure change over time Apks of the pressure in the crankcase and the pressure change ApREF of the reference pressure or the expected pressure change ApKsM in crankcase 20. This gradient is integrated over time in a method step <130>. In a method step <140>, the value obtained by the integration is compared with a threshold value, wherein, if the threshold value is exceeded, in a method step <150>, a fault or defect in the crankcase ventilation system is concluded.

[0053] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.