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

Abstract

A method for diagnosing a crankcase system of an internal combustion engine. A pressure value is captured in a crankcase system. A pressure value of a reference pressure is ascertained or a pressure value to be expected in the crankcase system is modeled. A gradient of the pressure value in the crankcase system and a gradient of the reference pressure or the modeled pressure in the crankcase system is formed. The two formed gradients are integrated over time. The function of the crankcase system is evaluated based on the values obtained by the integrations. A control device as well as an internal combustion engine for carrying out the method are provided.

Claims

1. A method for diagnosing a crankcase system of an internal combustion engine, the method comprising: capturing a pressure value in a crankcase system; ascertaining a pressure value of a reference pressure or modeling a pressure value to be expected in the crankcase system; forming a gradient of the pressure value in the crankcase system and a gradient of the reference pressure or the modeled pressure in the crankcase system; integrating the two formed gradients over time; and evaluating the function of the crankcase system based on the values obtained by the integrations.

2. The method according to claim 1, wherein the internal combustion engine is an internal combustion engine supercharged with the aid of an exhaust gas turbocharger, the reference pressure being captured in an intake manifold of an air supply system of the internal combustion engine, the intake manifold connecting a compressor of the exhaust gas turbocharger to an inlet of the internal combustion engine.

3. The method according to claim 2, wherein the reference pressure in the intake manifold is captured downstream from a throttle valve.

4. The method according to claim 2, wherein the reference pressure in the intake manifold is captured downstream from the compressor and upstream from a throttle valve.

5. The method according to claim 1, wherein a driving air flow is provided by an exhaust gas turbocharger, and a Venturi nozzle is arranged or formed in a breather line of the crankcase with the aid of which an underpressure is generated or amplified in the crankcase system.

6. The method according to claim 1, wherein an initiation of the method takes place when a boost pressure of the exhaust gas turbocharger and/or an intake manifold pressure has exceeded a defined threshold value, and/or wherein an underpressure is present at a Venturi nozzle in a breather line of the crankcase system.

7. The method according to claim 1, wherein a change of the pressure in the crankcase system is evaluated as a response to a change of the boost pressure during a pressure buildup or pressure reduction of the boost pressure.

8. The method according to claim 7, wherein an evaluation range lasts from a start of the change of the boost pressure to a point in time, at which no further rise or fall of the boost pressure takes place.

9. The method according to claim 1, wherein the pressure in the crankcase system is captured in a breather line or in a ventilation line of the crankcase or in the crankcase.

10. The method according to claim 1, wherein an initiation of the method takes place when the integral of the reference pressure gradient or the integral of the modeled pressure gradient in the crankcase system exceeds a defined threshold value.

11. The method according to claim 1, wherein the results of the integrations are each compared with a threshold value, and upon exceeding a first threshold value or upon dropping below a second threshold value for the integral of the pressure gradient in the crankcase system, a defect of the crankcase system is determined.

12. The method according to claim 1, wherein a relation of the two integrals or a difference from the two integrals is formed, and a function of the crankcase breather is determined based on the relation or the difference.

13. The method according to claim 1, wherein the pressure signal of the reference pressure or of the modeled pressure in the crankcase system and the pressure signal of the measured pressure in the crankcase system are filtered.

14. A control device comprising a memory unit and a computing unit, wherein a computer program product is stored in the memory unit, which, when executed by the computing unit, carries out the method according to claim 1.

15. An internal combustion engine comprising: at least one combustion chamber, wherein the combustion chamber is limited by a piston, which is connected to a crankshaft via a connecting rod, the crankshaft being arranged in a crankcase; and the control device according to claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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:

[0034] FIG. 1 shows an example of an internal combustion engine for carrying out a method according to the invention to diagnose a crankcase system of the internal combustion engine;

[0035] FIG. 2 shows an example of an internal combustion engine for carrying out a method according to the invention to diagnose a crankcase system of the internal combustion engine;

[0036] FIG. 3 shows an example of an internal combustion engine for carrying out a method according to the invention to diagnose a crankcase system of the internal combustion engine;

[0037] FIG. 4 shows a flowchart for carrying out a method according to the invention to diagnose a crankcase system of an internal combustion engine; and

[0038] FIG. 5 shows a further flowchart for carrying out a method according to the invention for the purpose of diagnosing a crankcase system.

DETAILED DESCRIPTION

[0039] FIG. 1 shows an example of an internal combustion engine 10 for carrying out a method according to the invention to diagnose a crankcase system 20, 26, 28, 56, 58, in particular, to diagnose the ventilation and breathing of crankcase system 20, 26, 28, 56, 58 of internal combustion engine 10. Internal combustion engine 10 includes an engine block 22 and a cylinder head 24. Internal combustion engine 10 furthermore includes at least one combustion chamber 12, which is limited by cylinder head 24, engine block 22, as well as a piston 14. Internal combustion engine 10 preferably includes multiple 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 rotational movement. Crankshaft 18 is surrounded by a crankcase 20, which is connected to engine block 22 of internal combustion engine 10.

[0040] Internal combustion engine 10 is connected to an air supply system 30 on the inlet side, via which fresh air may be supplied to combustion chamber 12 of internal combustion engine 10. Air supply system 30 comprises an air filter 34 for filtering the sucked-in 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 arranged in intake manifold 32 for controlling the amount of air supplied to combustion chamber 12. A boost pressure sensor 35 for capturing a boost pressure of exhaust gas turbocharger 38 is arranged in intake manifold 32 downstream from compressor 36 of exhaust gas turbocharger 38 and upstream from throttle valve 33. An intake manifold pressure sensor 37 is arranged in the intake manifold downstream from the throttle valve and upstream from the inlet of internal combustion engine 10. The intake manifold pressure essentially corresponds to the boost pressure of exhaust gas turbocharger 38 when throttle valve 33 is opened all the way.

[0041] Internal combustion engine 10 is furthermore connected to an exhaust system via its outlet, a turbine 39 of exhaust gas turbocharger 38 being arranged in the exhaust system, through which an exhaust gas flow of internal combustion engine 10 flows and drives compressor 36 of exhaust gas turbocharger 38.

[0042] A ventilation channel 26 is formed in engine block 22, which establishes a fluid connection between a first region of cylinder head 24 and crankcase 20. A breather channel 28 is also formed in engine block 22, which fluidically connects crankcase 20 to a second region of cylinder head 24. An oil recirculation channel 70 is provided in crankcase 20, via which oil may flow back into an oil pan 73. A first oil separator 72 is furthermore arranged in crankcase 20, to prevent oil mist from entering ventilation channel 26. A second oil separator 74 is additionally arranged in crankcase 20, which prevents an entry of oil mist into breather channel 28. In addition, an oil recirculation channel 78 is formed in engine block 22 to permit a back-flow of oil into oil pan 73.

[0043] A first flow path is provided for breathing crankcase 20, via which fresh air compressed by compressor 36 of exhaust gas turbocharger 38 may be introduced into crankcase 20 via a purge line 54, a ventilation line 56 in cylinder head 24, and ventilation channel 26. A check valve 42 is arranged in ventilation line 56 to avoid an uncontrolled outflow of air from crankcase 20. A throttle 40 may also be arranged in ventilation line 56 to limit the amount of fresh air supplied to crankcase 20.

[0044] To discharge the air from crankcase 20, a second flow path is provided, via which the air may be supplied from crankcase 20 to air supply system 30 via breather channel 28 and a breather line 58 in cylinder head 24 of internal combustion engine 10. A pressure control valve 46 is arranged in breather line 58. Breather line 58 has a branch 60 downstream from pressure control valve 46, at which breather line 58 is divided 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. A check valve 50 is arranged in first section 62, which prevents an inflow of fresh air from intake line 31 into breather line 58. First section 62 opens into intake line 31 of air supply system 30 at an opening 66, which is situated downstream from air filter 34 and upstream from compressor 36 of exhaust gas turbocharger 38. A check valve 48 is arranged in second section 64, which prevents an inflow of fresh air from intake manifold 32 into breather line 58. Second section 64 opens into intake manifold 32 of air supply system 30 at a second opening 68 downstream from throttle valve 33. A fallen-off or defective breather line 58 results in the fact that no or only a small amount of gases may be transported from crankcase 20 into intake line 31 in the direction of opening 66. As a result, in the event of a boost pressure buildup of exhaust gas turbocharger 38, no or only a less-than-expected amount of fresh air would also flow into crankcase 20 via ventilation line 56 and ventilation channel 26. The evaluation of a volume flow through ventilation line 56 may thus be used to diagnose the function of the crankcase breather. In addition, a lower-than-expected underpressure would set in downstream from throttle 40 in ventilation line 56, so that the pressure measured at sensor 52 or a pressure change resulting from a pressure change in intake manifold 32 as a result of a boost pressure buildup may also be used to diagnose the function of the crankcase breather.

[0045] Crankcase system 20, 26, 28, 56, 58 comprises at least crankcase 20, a ventilation line 26, 56, and a breather line 28, 58. Crankcase system 20, 26, 28, 56, 58 may additional comprise further ventilation or breather lines 60, 62 as well as an oil separator 72, 74, a throttle 40, a check valve 42, 48, 50, a pressure control valve 46, and/or a Venturi nozzle 44, in particular a suction jet pump. At least one pressure sensor 52 is furthermore assigned to crankcase system 20, 26, 28, 56, 58, which captures a pressure in crankcase system 20, 26, 28, 56, 58.

[0046] Internal combustion engine 10 is furthermore operatively connected to a fuel supply system. To avoid an uncontrolled escape of fuel vapors from fuel tank 80, an active carbon filter 88 is provided, in which these fuel vapors are trapped and bound. Active carbon filter 88 is connected to intake line 31 of air supply system 30 via a tank venting line 82. To regenerate active carbon filter 88, a purge air pump 84 is provided, which is arranged in tank venting line 82. A tank venting valve 86 is also provided in tank venting line 82 to control the discharge of the fuel vapor into intake line 31.

[0047] Internal combustion engine 10 is operatively connected to a control device 90, which includes a memory unit 92 and a computing unit 94. A computer program code 96 is stored in memory unit 92, which carries out a method according to the invention to diagnose a crankcase breather when computer program code 96 is executed by computing unit 94 of control device 90.

[0048] FIG. 2 shows an example of an internal combustion engine 10 for carrying out a method according to the invention to diagnose a crankcase system 20, 26, 28, 56, 58 of internal combustion engine 10. Internal combustion engine 10 includes an engine block 22 and a cylinder head 24. Internal combustion engine 10 furthermore includes at least one combustion chamber 12, which is limited by cylinder head 24, engine block 22, as well as a piston 14. Internal combustion engine 10 preferably includes multiple combustion chambers 12. Piston 14 is connected to a crankshaft 18 via a connecting rod 16, which converts an oscillating movement of piston 14 into a rotational movement. Crankshaft 18 is surrounded by a crankcase 20, which is connected to engine block 22 of internal combustion engine 10.

[0049] Internal combustion engine 10 is connected to an air supply system 30 on the inlet side, via which fresh air may be supplied to combustion chamber 12 of internal combustion engine 10. Air supply system 30 comprises an air filter 34 for filtering the sucked-in 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 the exhaust gas turbocharger is connected to an inlet of internal combustion engine 10 via an intake manifold 32. A throttle valve 33 is arranged in intake manifold 32 for controlling the amount of air supplied to combustion chamber 12. A boost pressure sensor 35 for capturing the boost pressure of exhaust gas turbocharger 38 is arranged in intake manifold 32 downstream from compressor 36 of exhaust gas turbocharger 38 and upstream from throttle valve 33. An intake manifold pressure sensor 37 is arranged in the intake manifold downstream from the throttle valve and upstream from the inlet of internal combustion engine 10. The intake manifold pressure essentially corresponds to the boost pressure of exhaust gas turbocharger 38 when throttle valve 33 is opened all the way.

[0050] Internal combustion engine 10 is furthermore connected to an exhaust system via its outlet, a turbine 39 of exhaust gas turbocharger 38 being arranged in the exhaust system, through which an exhaust gas flow of internal combustion engine 10 flows and drives compressor 36 of exhaust gas turbocharger 38.

[0051] A ventilation channel 26 is formed in engine block 22, which establishes a fluid connection between a first region of cylinder head 24 and crankcase 20. A breather channel 28 is also formed in engine block 22, which fluidically connects crankcase 20 to a second region of cylinder head 24. An oil recirculation channel 70 is provided in crankcase 20, via which oil may flow back into an oil pan 73. A first oil separator 72 is furthermore arranged in crankcase 20, to prevent oil mist from entering ventilation channel 26. A second oil separator 74 is additionally arranged in crankcase 20, which prevents an entry of oil mist into breather channel 28. In addition, an oil recirculation channel 78 is formed in engine block 22 to permit a back-flow of oil into oil pan 73.

[0052] A first flow path is provided for breathing crankcase 20, via which fresh air compressed by compressor 36 of exhaust gas turbocharger 38 may be introduced into crankcase 20 via a purge line 54, a ventilation line 56 in cylinder head 24, and ventilation channel 26. A check valve 42 is arranged in ventilation line 56 to avoid an uncontrolled outflow of air from crankcase 20. A throttle 40 may also be arranged in ventilation line 56 to limit the amount of fresh air supplied to crankcase 20. A pressure sensor 52 is furthermore arranged in ventilation line 56, with the aid of which a pressure in ventilation line 56 may be captured. Due to the fluid connection between the ventilation line and crankcase 20, a function of the crankcase breather may be inferred from the pressure change of ventilation line 56.

[0053] To discharge the air from crankcase 20, a second flow path is provided, via which the air may be supplied from crankcase 20 to air supply system 30 via breather channel 28 and a breather line 58 in cylinder head 24 of internal combustion engine 10. A pressure control valve 46 is arranged in breather line 58. Breather line 58 has a branch 60 downstream from pressure control valve 46, at which breather line 58 is divided 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. A check valve 50 is arranged in first section 62, which prevents an inflow of fresh air from intake line 31 into breather line 58. First section 62 empties into intake line 31 of air supply system 30 at an opening 66, which is situated downstream from air filter 34 and upstream from compressor 36 of exhaust gas turbocharger 38. A check valve 48 is furthermore arranged in second section 64, which prevents an inflow of fresh air from intake manifold 32 into breather line 58. Second section 64 opens into intake manifold 32 of air supply system 30 at a second opening 68 downstream from throttle valve 33.

[0054] Internal combustion engine 10 is furthermore operatively connected to a fuel supply system. To avoid an uncontrolled escape of fuel vapors from fuel tank 80, an active carbon filter 88 is provided, in which these fuel vapors are trapped and bound. Active carbon filter 88 is connected to intake line 31 of air supply system 30 via a tank venting line 82. To regenerate active carbon filter 88, a purge air pump 84 is provided, which is arranged in tank venting line 82. A tank venting valve 86 is also provided in tank venting line 82 to control the discharge of the fuel vapor into intake line 31.

[0055] Internal combustion engine 10 is operatively connected to a control device 90, which includes a memory unit 92 and a computing unit 94. A computer program code 96 is stored in memory unit 92, which carries out a method according to the invention to diagnose a crankcase breather when computer program code 96 is executed by computing unit 94 of control device 90.

[0056] FIG. 3 shows an example an internal combustion engine 10 for carrying out a method according to the invention to diagnose a crankcase system 20, 26, 28, 56, 58 of internal combustion engine 10. Internal combustion engine 10 includes an engine block 22 and a cylinder head 24. Internal combustion engine 10 furthermore includes at least one combustion chamber 12, which is limited by cylinder head 24, engine block 22, and a piston 14. Internal combustion engine 10 preferably includes multiple combustion chambers 12. Piston 14 is connected to a crankshaft 18 via a connecting rod 16, which converts an oscillating movement of piston 14 into a rotational movement. Crankshaft 18 is surrounded by a crankcase 20, which is connected to engine block 22 of internal combustion engine 10.

[0057] Internal combustion engine 10 is connected to an air supply system 30 on the inlet side, via which fresh air may be supplied to combustion chamber 12 of internal combustion engine 10. Air supply system 30 comprises an air filter 34 for filtering the sucked-in 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 the exhaust gas turbocharger is connected to an inlet of internal combustion engine 10 via an intake manifold 32. A throttle valve 33 is arranged in intake manifold 32 for controlling the amount of air supplied to combustion chamber 12. A boost pressure sensor 35 for capturing the boost pressure of exhaust gas turbocharger 38 is arranged in intake manifold 32 downstream from compressor 36 of exhaust gas turbocharger 38 and upstream from throttle valve 33. An intake manifold pressure sensor 37 is arranged in the intake manifold downstream from the throttle valve and upstream from the inlet of internal combustion engine 10. The intake manifold pressure essentially corresponds to the boost pressure of exhaust gas turbocharger 38 when throttle valve 33 is opened all the way.

[0058] Internal combustion engine 10 is furthermore connected to an exhaust system via its outlet, a turbine 39 of exhaust gas turbocharger 38 being arranged in the exhaust system, through which an exhaust gas flow of internal combustion engine 10 flows and drives compressor 36 of exhaust gas turbocharger 38.

[0059] A ventilation channel 26 is formed in engine block 22, which establishes a fluid connection between a first region of cylinder head 24 and crankcase 20. A breather channel 28 is also formed in engine block 22, which fluidically connects crankcase 20 to a second region of cylinder head 24. An oil recirculation channel 70 is provided in crankcase 20, via which oil may flow back into an oil pan 73. A first oil separator 72 is furthermore arranged in crankcase 20, to prevent an entry of oil mist into ventilation channel 26. A second oil separator 74 is additionally arranged in crankcase 20, which prevents an entry of oil mist into breather channel 28. In addition, an oil recirculation channel 78 is formed in engine block 22 to permit a back-flow of oil into oil pan 73.

[0060] A first flow path is provided for breathing crankcase 20, via which fresh air compressed by compressor 36 of exhaust gas turbocharger 38 may be introduced into crankcase 20 via a purge line 54, a ventilation line 56 in cylinder head 24, and ventilation channel 26. A check valve 42 is arranged in ventilation line 56 to avoid an uncontrolled outflow of air from crankcase 20. A throttle 40 may also be arranged in ventilation line 56 to limit the amount of fresh air supplied to crankcase 20.

[0061] To discharge the air from crankcase 20, a second flow path is provided, via which the air may be supplied from crankcase 20 to air supply system 30 via breather channel 28 and a breather line 58 in cylinder head 24 of internal combustion engine 10. A pressure control valve 46 is arranged in breather line 58. Breather line 58 has a branch 60 downstream from pressure control valve 46, at which breather line 58 is divided 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. A check valve 50 is arranged in first section 62, which prevents an inflow of fresh air from intake line 31 into breather line 58. First section 62 opens into intake line 31 of air supply system 30 at a first opening 66, which is situated downstream from air filter 34 and upstream from compressor 36 of exhaust gas turbocharger 38. A check valve 48 is furthermore arranged in second section 64, which prevents an inflow of fresh air from intake manifold 32 into breather line 58. Second section 64 empties into intake manifold 32 of air supply system 30 at a second opening 68 downstream from throttle valve 33. A pressure sensor 52, which detects a pressure in crankcase 20, is arranged in crankcase 20. A function of the crankcase breather may be inferred from a change of the pressure in air supply system 30 and a change of the pressure in crankcase 20 resulting therefrom.

[0062] Internal combustion engine 10 is furthermore operatively connected to a fuel supply system. To avoid an uncontrolled escape of fuel vapors from fuel tank 80, an active carbon filter 88 is provided, in which these fuel vapors are trapped and bound. Active carbon filter 88 is connected to intake line 31 of air supply system 30 via a tank venting line 82. To regenerate active carbon filter 88, a purge air pump 84 is provided, which is arranged in tank venting line 82. A tank venting valve 86 is also provided in tank venting line 82 to control the discharge of the fuel vapor into intake line 31.

[0063] Internal combustion engine 10 is operatively connected to a control device 90, which includes a memory unit 92 and a computing unit 94. A computer program code 96 is stored in memory unit 92, which carries out a method according to the invention to diagnose a crankcase breather when computer program code 96 is executed by computing unit 94 of control device 90.

[0064] FIG. 4 shows a flowchart for carrying out a method according to the invention to diagnose a crankcase breather of an internal combustion engine 10. In a first method step <100>, a temporal change of pressure p.sub.KS in crankcase 20 or in a component 22, 24, 26, 28 fluidically connected to crankcase 20 is captured. In a method step <110>, a pressure change p.sub.REF of a reference pressure is also captured, or a temporal change p.sub.KSM to be expected for a pressure change in crankcase 20 is modeled. In a method step <120>, a gradient is formed from temporal pressure change p.sub.KS of the pressure in the crankcase and pressure change p.sub.REF of the reference pressure or pressure change p.sub.KSM to be expected 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, a malfunction or a defect of the crankcase breather is inferred in a method step <150> upon an exceeding of the threshold value.

[0065] FIG. 5 shows a further flowchart of a method according to the invention to diagnose a crankcase system 10, 26, 28, 56, 58. A reference pressure p.sub.REF or a modeled pressure in the crankcase system p.sub.KGSm and a measured pressure in the crankcase system p.sub.KGS are provided as input variables. A first filter I, in particular a PTx filter, is provided for reference pressure p.sub.REF or a modeled pressure in the crankcase system p.sub.KGSm for the purpose of smoothing the measured values captured by the sensor for the reference pressure. A differentiation element II is subsequently provided, with the aid of which a gradient of reference pressure p.sub.REF or of modeled pressure p.sub.KGSm in the crankcase system is formed. If the value of reference pressure p.sub.REF or of modeled pressure p.sub.KGSm in the crankcase system is between a permissible minimum pressure p.sub.min and a permissible maximum pressure p.sub.max, and if an enabling condition for the method is met, an integral of the gradient is formed.

[0066] A second filter IV, in particular a PTx filter, is provided in parallel for the measured pressure in crankcase system p.sub.KGS for the purpose of smoothing the measured values captured by the sensor for the reference pressure. A differentiation element V is subsequently provided, with the aid of which a gradient of pressure p.sub.KGS in the crankcase system is formed. If the enabling condition is met, an integral of the gradient is formed. The integral is compared with a defect threshold DFS. If the integral is above the defect threshold, an intact function of the crankcase system may be assumed during evaluation VI.

[0067] If the integral is below a threshold value, a defect of the crankcase system may be inferred in evaluation VI, since the gradient to be diagnosed is smaller than a gradient to be expected for a function of the crankcase system.

[0068] 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.