Method and apparatus for checking the plausibility of the functionality of a crankcase ventilation system

Abstract

Various embodiments may include a method for checking the plausibility of the functionality of a crankcase ventilation system of an internal combustion engine, wherein crankcase ventilation system has a crankcase, an intake tract equipped with an intake manifold, and a connecting line arranged between the crankcase and the intake manifold, the method comprising: detecting an occurrence of a negative load change; in response, comparing a measured intake manifold pressure with a modelled intake manifold pressure using acquired operating variables of the internal combustion engine and of a crankcase model; and determining on the basis of the comparison result whether the connecting line arranged between the crankcase and the intake manifold becomes blocked or drops out.

Claims

1. A method for checking the plausibility of the functionality of a crankcase ventilation system of an internal combustion engine, wherein crankcase ventilation system has a crankcase, an intake tract equipped with an intake manifold, and a connecting line arranged between the crankcase and the intake manifold, the method comprising: detecting an occurrence of a negative load change; in response, comparing a measured intake manifold pressure with a modelled intake manifold pressure using acquired operating variables of the internal combustion engine and of a crankcase model; wherein the connecting line pneumatically connects a free volume of the crankcase to the intake tract at a point downstream of a throttle valve in the intake tract; comparing the measured intake manifold pressure to the measured ambient pressure; if the measured intake manifold pressure is higher than the ambient pressure, waiting until a negative load change occurs; upon detecting an occurrence of a negative load change, comparing the measured intake manifold pressure to the measured ambient pressure, activating a diagnostic window if the measured intake manifold pressure undershoots the measured ambient pressure; calculating a difference or an integral of the difference between the measured intake manifold pressure and the modelled intake manifold pressure within the diagnostic window; comparing the determined difference or the integral of the difference to a predefined threshold value; and if the determined difference or the integral of the difference is greater than the threshold value, detecting whether the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.

2. The method as claimed in claim 1, further comprising adapting operation of the internal combustion engine in response to detecting the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.

3. The method as claimed in claim 2, wherein adapting operation of the internal combustion engine includes making an entry is made in a fault register or deactivating a crankcase function or displaying a fault.

4. An internal combustion engine comprising: a crankcase ventilation system; a crankcase; an intake tract equipped with an intake manifold; a connecting line arranged between the crankcase and the intake manifold, wherein the connecting line pneumatically connects a free volume of the crankcase to the intake tract at a point downstream of a throttle valve in the intake tract; and a control apparatus having a processor and a memory storing instructions, when loaded and execute by the processor, configure the processor to: detect an occurrence of a negative load change; in response, compare a measured intake manifold pressure with a modelled intake manifold pressure using acquired operating variables of the internal combustion engine and of a crankcase model; comparing the measured intake manifold pressure to the measured ambient pressure; if the measured intake manifold pressure is higher than the ambient pressure, waiting until a negative load change occurs; upon detecting an occurrence of a negative load change, comparing the measured intake manifold pressure to the measured ambient pressure, activating a diagnostic window if the measured intake manifold pressure undershoots the measured ambient pressure; calculating a difference or an integral of the difference between the measured intake manifold pressure and the modelled intake manifold pressure within the diagnostic window; comparing the determined difference or the integral of the difference to a predefined threshold value; and if the determined difference or the integral of the difference is greater than the threshold value, detecting whether the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further properties of the teachings herein are elucidated from the exemplary explanation thereof below, given with reference to the figures. In the drawings:

(2) FIG. 1 shows a sketch of an internal combustion engine which is equipped with an apparatus for checking the plausibility of the functionality of a crankcase ventilation system incorporating the teachings of the present disclosure;

(3) FIG. 2 shows a sketch illustrating a crankcase model incorporating the teachings of the present disclosure;

(4) FIG. 3 shows a sketch illustrating passive detection of a blockage in the connecting line between the crankcase and the intake manifold incorporating the teachings of the present disclosure;

(5) FIG. 4 shows a sketch illustrating active detection of a blockage in the connecting line between the crankcase and the intake manifold incorporating the teachings of the present disclosure;

(6) FIG. 5 shows a sketch illustrating passive detection of dropping out or absence of the connecting line between the crankcase and the intake manifold incorporating the teachings of the present disclosure;

(7) FIG. 6 shows a sketch illustrating active detection of dropping out or absence of the connecting line between the crankcase and the intake manifold incorporating the teachings of the present disclosure;

(8) FIG. 7 shows a sketch illustrating active detection of dropping out or absence of the connecting line between the crankcase and the intake manifold when the intake manifold model controller is switched off incorporating the teachings of the present disclosure; and,

(9) FIG. 8 shows a flowchart illustrating a method for checking the plausibility of the functionality of a crankcase ventilation system incorporating the teachings of the present disclosure.

DETAILED DESCRIPTION

(10) Various embodiments of the teachings herein permit a fault to be detected in the region of the connecting line, e.g., embodied as a connecting hose, between the crankcase and the intake manifold, without the need for the presence of additional components such as a switching valve, differential pressure sensor, etc. It furthermore permits in many cases detection of a fault without using a lambda sensor or a deflection of a lambda controller. It additionally permits the presence of leakage in the intake manifold to be differentiated from the presence of dropping out of the connecting hose between the crankcase and the intake manifold. It also permits the dropping out of the connecting line, preferably embodied as a connecting hose, between the crankcase and the intake manifold to be detected. In addition, a method incorporating the teachings herein operates comparatively quickly, since it is not necessary to compare data items from a plurality of successive idling phases with one another.

(11) FIG. 1 shows a sketch of an internal combustion engine which is equipped with an apparatus for checking the plausibility of the functionality of a crankcase ventilation system incorporating the teachings of the present disclosure. The internal combustion engine comprises an intake tract 1, an engine block 2, a cylinder head 3 and an exhaust tract 4. The intake tract 1 comprises a throttle valve 11, and an intake manifold 13, which is fed towards a cylinder Z1 via an intake duct into the engine block 2.

(12) The engine block 2 comprises a crankcase 20 which accommodates a crankshaft 21, and also a connecting rod 25 which is coupled to a piston 24 of the cylinder Z1 and which couples the crankshaft 21 to the piston 24 of the cylinder Z1. The crankcase 20 is additionally filled partially with lubricant, in particular engine oil, which is circulated and filtered by means of devices which are not illustrated. Moreover, the crankcase 20 comprises a free volume which can extend, if appropriate, as far as the cylinder head 3.

(13) The cylinder head 3 comprises a valve drive with a gas inlet valve 30 and a gas outlet valve 31 and associated valve drives 32, 33. The cylinder head 3 additionally comprises an injection valve 34 and a spark plug 35. Alternatively, the injection valve 34 can also be arranged in the intake tract 1.

(14) The exhaust gas tract 4 comprises an exhaust gas catalytic converter 40, which is embodied, for example, as a three-way catalytic converter.

(15) In order to direct the fuel vapors which are present in the crankcase 20 into the intake tract 1, a crankcase ventilation apparatus 5 is provided. The latter has a first duct 51 which branches off from the intake tract 1 upstream of the throttle valve and leads to the crankcase 20. The first duct 51 is pneumatically coupled to the free volume of the crankcase 20. Fresh air can flow into the crankcase 20 through this duct 51. Furthermore, a second duct 53 is provided which connects the free volume of the crankcase 20 pneumatically to the intake tract 1 at a point downstream of the throttle valve 11. The free volume of the crankcase 20 can be ventilated by means of the two ducts 51 and 53. An oil mist separator provided in the crankcase ventilation apparatus 5 is not illustrated for reasons of clarity.

(16) A regulating valve 54 in the form of an underpressure valve is arranged in the second duct 53, which underpressure valve automatically adapts an effective cross-section of the second duct 53, to be precise in such a way that a defined underpressure with respect to the ambient pressure is set in the crankcase 20.

(17) When there is a suitable low pressure in the intake tract 1 downstream of the throttle valve 11, to be precise in the region in which the second duct 53 opens into the intake tract 1, the gases located in the free volume of the crankcase 20 flow back into the intake tract 1.

(18) The illustrated apparatus furthermore has a control apparatus 6. Sensors which acquire operating variables of the internal combustion engine and make available a measurement signal which represents the respectively acquired operating variable are assigned to said control device 6. These input signals of the control apparatus 6 are summarized in FIG. 1 and denoted by the reference symbol ES. The control apparatus is designed to use associated actuation signals to actuate, as a function of the specified operating variables, actuator elements which are assigned to the internal combustion engine. These actuation signals are summarized in FIG. 1 and denoted by the reference symbol AS.

(19) The sensors may include, for example, a pedal position encoder 71 which acquires the position of an accelerator pedal 7, an air mass flow meter 14 which acquires an air mass flow upstream of the throttle valve 11, a temperature sensor 15 which acquires an intake air temperature, a pressure sensor 16 which acquires an intake manifold pressure, a crankshaft angle sensor 22 which acquires a crankshaft angle to which a rotational speed is assigned, a throttle valve angle sensor 37, a temperature sensor 36 which acquires the temperature of the internal combustion engine, and an exhaust gas probe 41 which acquires a residual oxygen content of the exhaust gas and outputs a measurement signal which is characteristic of the air/fuel ratio in the cylinder Z1 during the combustion of the air/fuel mixture.

(20) The actuator elements may include, for example, the throttle valve 11, the gas inlet and gas outlet valves 30, 31, the injection valve 34 and the spark plug 35.

(21) Apart from the cylinder Z1, other further cylinders Z2 to Z4 are also provided, and corresponding further actuator elements are assigned thereto respectively.

(22) The control apparatus 6 comprises a processor unit 61 which is coupled to a program memory 62, a data memory 63 and a fault memory 64. The fault memory 64 is connected to a fault display apparatus 65. Programs for operating the internal combustion engine are stored in the program memory 62 and are executed during the operation of the internal combustion engine.

(23) These programs may include a basically known intake manifold model which calculates a modelled intake manifold pressure. The latter is adjusted to the measured intake manifold pressure by means of an intake manifold model control factor (INSY controller). These programs furthermore include a crankcase model 66 which is illustrated in FIG. 2 and whose output signals are fed to the intake manifold model which uses the output signals of the crankcase model for more precise calculation of the modelled intake manifold pressure. The following input signals may be fed to the crankcase model 66: the engine speed N, the ambient pressure P.sub.amb, the ignition angle W.sub.ign, the pressure upstream of the throttle valve P.sub.upstrmthrottle, the intake manifold pressure P.sub.intmanfpres, the ambient temperature T.sub.amb, the coolant temperature T.sub.coolant, the intake manifold temperature T.sub.intake, and the oil temperature T.sub.oil.

(24) The following output signals may be determined from these input signals by means of the crankcase model 66: the pressure in the crankcase P.sub.crnkcse, the absolute air mass in the crankcase M.sub.abs.air,crnkcse, the absolute fuel mass in the crankcase M.sub.abs.HC,crnkcse, the absolute residual gas mass in the crankcase M.sub.abs.RG,crnkcse, the fresh air mass flow into the crankcase MAF.sub.in,crnkcse, the blow-by mass flow into the crankcase MFL.sub.in,BlowBy, the fresh air mass flow out of the crankcase MAF.sub.fa,crnkcse, the vaporized mass flow out of the crankcase MFL.sub.fa,crnkcse and the residual gas mass flow out of the crankcase MFL.sub.RG,crnkcse.

(25) In some embodiments, the crankcase model 66 may be used to determine the air mass or gas mass in the intake manifold as precisely as possible. An indication of the fact that the air mass or gas mass in the intake manifold is correctly modelled is the correspondence between the modelled and the measured intake manifold pressure.

(26) When negative load changes, referred to as “tip outs”, occur, the influence of the air mass which flows back into the intake manifold 13 through the crankcase 20 is particularly large. This flowing of the air mass or gas mass out of the crankcase 20 can be detected on the basis of the profile of the intake manifold pressure, i.e. from a comparison of the profile of the modelled intake manifold pressure with the measured intake manifold pressure.

(27) The following diagnostic possibilities are obtained by means of the crankcase model 66 described above:

(28) A blockage in the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13 can be detected as passive detection. This passive detection is based on the fact that when a negative load change is present, an intact crankcase ventilation system can be actuated by virtue of the fact that a rise in the intake manifold pressure can be detected, said rise starting when the ventilation of the crankcase starts and ending when the pressure-regulating valve 54 closes.

(29) This rise in pressure, which can be determined both chronologically and quantitatively by using the crankcase model, is used as a decision criterion for the specified passive detection of a blockage in the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13, wherein the measured intake manifold pressure is compared with the modelled intake manifold pressure. If the measured intake manifold pressure is below the modelled intake manifold pressure, then the presence of a blockage is detected. A precondition for such a diagnostic decision is that a low intake manifold model control factor (INSY controller) is present.

(30) Such passive detection of a blockage in the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13 is illustrated in FIG. 3. In this context, the presence of a fault is illustrated in the left-hand diagram of FIG. 3, since in the diagnostic window F shown there the modelled intake manifold pressure K1 deviates from the measured intake manifold pressure K3. The diagnostic window is opened when the measured intake manifold pressure undershoots the ambient pressure, which is illustrated by the line K2, and is closed again after the expiry of a predefined time period.

(31) In the right-hand diagram of FIG. 3, the fault-free state is illustrated, since in the diagnostic window F shown there the modelled intake manifold pressure K1 corresponds to the measured intake manifold pressure K3. A blockage in the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13 can be confirmed as active detection. This active detection can be carried out, for example, chronologically after passive detection and can be used to set up a request to a diagnostic coordinator to initiate more detailed checking of the crankcase or to take other measures. In order to carry out this active detection, when a negative load change is present, the crankcase model is deactivated in the sense that all the mass flows are set to 0 kg/h. Then, when a blockage is present in the connecting hose 53 between the crankcase 20 and the intake manifold 13, the modelled pressure is approximately equal to the measured pressure. Furthermore, when a blockage is present, the deflection of a lambda controller which is present is only small. If no blockage is present, the deflection of a lambda controller which is present is significantly larger. The presence of a low intake manifold model controller factor (INSY controller) is also a precondition for this diagnostic decision.

(32) Such active detection of a blockage in the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13, is illustrated in FIG. 4. In this context, the presence of a fault is illustrated in the left-hand diagram of FIG. 4, since in the diagnostic window F shown there the modelled intake manifold pressure K1 corresponds to the measured intake manifold pressure K3. The diagnostic window is also opened here when the measured intake manifold pressure undershoots the ambient pressure, which is illustrated by the line K2, and is closed again after the expiry of a predefined time period.

(33) In the right-hand diagram of FIG. 4, the fault-free state is illustrated, since in the diagnostic window F shown there the modelled intake manifold pressure K1 deviates from the measured intake manifold pressure K3.

(34) Furthermore, dropping out or absence of the connecting line 53, implemented as a connecting hose, between the crankcase 20 and the intake manifold 13 can be detected as passive detection. This detection is based on the fact that dropping out of the specified connecting hose in steady-state operation is equivalent to leakage in the intake manifold, wherein an intake manifold model controller (INSY controller) which is present compensates this leakage by a change in the throttle valve angle. When a negative load change is present, there is the possibility of differentiating between the specified leakage in the intake manifold 13 and a dropped-out connecting hose 53 between the crankcase 20 and the intake manifold 13. This is because when a negative load change is present a leakage in the intake manifold becomes apparent in such a way that the mass flow which exits the crankcase can still be detected on the basis of a non-continuous drop in pressure. In contrast with this, dropping out of the connecting hose 53 between the crankcase 20 and the intake manifold 13 can be detected on the basis of a continuous drop in pressure. The deviation between the measured intake manifold pressure and the modelled intake manifold pressure is large during the ventilation of the crankcase 20. In both above-mentioned cases, it is necessary for the respective diagnostic decision that there is a large intake manifold model controller factor (INSY controller). This large intake manifold model controller factor serves as the differentiating criterion with respect to the presence of a blockage.

(35) Such passive detection of dropping out of the connecting hose 53 provided between the crankcase 20 and the intake manifold 13 is illustrated in FIG. 5. In this context, the presence of a fault is illustrated in the left-hand diagram of FIG. 5, since in the diagnostic window F shown there the modelled intake manifold pressure K1 deviates from the measured intake manifold pressure K3. The diagnostic window is opened when the measured intake manifold pressure undershoots the ambient pressure, which is illustrated by the line K2, and is closed again after the expiry of a predefined time period.

(36) In the right-hand diagram of FIG. 5, the fault-free state is illustrated, since in the diagnostic window F shown there the modelled intake manifold pressure K1 corresponds to the measured intake manifold pressure K3. Dropping out of the connecting hose 53 between the crankcase 20 and the intake manifold 13 can be confirmed as active detection. This active detection can be carried out, for example, chronologically after passive detection and can be used to set up a request to a diagnostic coordinator to initiate more detailed checking or other measures. In order to carry out this active detection, when a negative load change is present, the crankcase model is deactivated in the sense that all the mass flows are set to 0 kg/h. Then, when dropping out of the connecting hose between the crankcase 20 and the intake manifold 13 has occurred, the modelled pressure is approximately equal to the measured pressure. The presence of a high intake manifold model controller factor (INSY controller) is also a precondition for this diagnostic decision, in order to be able to differentiate from a blockage of the connecting hose 53.

(37) Such active detection of dropping out of the connecting hose 53 between the crankcase 20 and the intake manifold 13 is illustrated in FIG. 6. In this context, the presence of a fault is illustrated in the left-hand diagram of FIG. 6, since in the diagnostic window F shown there the modelled intake manifold pressure K1 corresponds to the measured intake manifold pressure K3. The diagnostic window is also opened here when the measured intake manifold pressure undershoots the ambient pressure, which is illustrated by the line K2, and is closed again after the expiry of a predefined time period.

(38) In the right-hand diagram of FIG. 6, the fault-free state is illustrated, since in the diagnostic window F shown there the modelled intake manifold pressure K1 deviates from the measured intake manifold pressure K3.

(39) A further diagnostic possibility is illustrated in FIG. 7. This further diagnostic possibility corresponds essentially to the diagnostic possibilities explained with reference to FIGS. 5 and 6 but, in particular it differs from these in that as a further precondition for the diagnosis the intake manifold model controller (INSY controller) is switched off. A difference from the case shown in the right-hand illustration of FIG. 6 is that the deviation between the measured intake manifold pressure and the modelled intake manifold pressure is even greater than in the example shown in the right-hand illustration of FIG. 6.

(40) The presence of a fault is illustrated in the left-hand diagram of FIG. 7, since in the diagnostic window F there the modelled intake manifold pressure K1 corresponds to the measured intake manifold pressure K3. The presence of a fault-free case is illustrated in the right-hand diagram of FIG. 7, since in the diagnostic window F there the modelled intake manifold pressure K1 deviates from the measured intake manifold pressure K3.

(41) FIG. 8 shows a flowchart relating to the checking of the plausibility of a method for checking the functionality of a crankcase ventilation system. After the start of the method, in a step S1 an interrogation occurs as to whether the measured intake manifold pressure is higher than the ambient pressure. If this is not the case, the process jumps back to step S1. On the other hand, if this is the case, the process continues to a step S2.

(42) In the step S2 the process waits until a negative load change occurs. After the occurrence of a negative load change, in a step S3 an interrogation occurs as to whether the measured intake manifold pressure undershoots the ambient pressure. If this is not the case, the process returns to step S3. On the other hand, if this is the case, a diagnostic window is activated in a step S4.

(43) After the activation of the diagnostic window, in a step S5 the difference or the integral of the difference between the measured intake manifold pressure and the modelled intake manifold pressure is determined.

(44) In a step S6, an interrogation occurs as to whether the determined difference or the integral of the difference is greater than a predefined threshold value. If this is not the case, the process returns to step S6. On the other hand, if this is the case, a transition to step S7 takes place in which a measure is taken. This measure can be, for example, an entry in a fault register or a deactivation of the crankcase function.

(45) After this step S7, the method is ended.

(46) Multiple advantages may be achieved by the implementing the teachings described above:

(47) The detection of a fault in the region of the connecting hose 53 between the crank case 20 and the intake manifold 13 without the need for the presence of additional components such as a switching valve, a differential pressure sensor, etc. The methods furthermore permit in many cases fault detection without the use of a lambda sensor or of a deflection of a lambda controller. The methods additionally permit the presence of leakage in the intake manifold 13 to be differentiated from the presence of dropping out of the connecting hose 53 between the crankcase 20 and the intake manifold 13. In addition, the methods described herein operate comparatively quickly, since it is not necessary to compare data items from a plurality of successive idling phases with one another.

LIST OF REFERENCE SIGNS

(48) 1 Intake tract 11 Throttle valve 13 Intake manifold 14 Air mass meter 15 Temperature sensor for intake air 16 Intake manifold pressure sensor 17 Lubricant, engine oil 2 Engine block 20 Crankcase 21 Crankshaft 22 Crankshaft angle sensor 24 Piston 25 Connecting rod 3 Cylinder head 30 Gas inlet valve 31 Gas outlet valve 32, 33 Valve drive 34 Injection valve 35 Spark plug 36 Temperature sensor for internal combustion engine 37 Throttle valve angle sensor 4 Exhaust gas tract 40 Exhaust gas catalytic converter 41 Exhaust gas probe 5 Crankcase ventilation apparatus 51 First duct, fresh air feed line 53 Second duct 54 Underpressure-regulating valve 6 Control device 61 Computational unit, processor 62 Program memory 63 Data store, value memory 64 Fault memory 65 Fault display apparatus 66 Crankcase model 7 Accelerator pedal 71 Pedal position encoder AS Output signals ES Input signals Z1-Z4 Cylinders N Engine speed P.sub.amb Ambient pressure W.sub.ign Ignition angle P.sub.upstrmthrottle Pressure upstream of throttle valve P.sub.intakemanfpres Intake manifold pressure T.sub.amb Ambient temperature T.sub.coolant Coolant temperature T.sub.intake Intake manifold temperature T.sub.oil Oil temperature P.sub.crnkcse Pressure in the crankcase M.sub.abs.air,crnkcse Absolute air mass in the crankcase M.sub.abs.HC,crnkcse Absolute fuel mass in the crankcase M.sub.abs.RG,crnkcse Absolute residual gas mass in the crankcase MAF.sub.in,crnkcse Fresh air mass flow into the crankcase MFL.sub.in,BlowBy Blow-by mass flow into the crankcase MAF.sub.fa,crnkcse Fresh air mass flow out of the crankcase MFL.sub.fa,crnkcse Evaporated mass flow out of the crankcase MFL.sub.RG,crnkcse Residual gas mass flow out of the crankcase