Method and device for diagnosing a scavenge line path of an oil tank ventilation system of a motor vehicle operating in a combustion engine manner

Abstract

A method for diagnosing the scavenging path of a fuel tank ventilation system in a motor vehicle operating in a combustion engine mode is disclosed, wherein the scavenging path extends between a fuel vapor retention filter (3) and an intake manifold (24) of the motor vehicle, and includes a fuel tank ventilation valve (6), a pressure sensor (28), a scavenging path region arranged upstream of the pressure sensor, a scavenging path region arranged downstream of the pressure sensor, a full-load scavenging path (14) arranged between the fuel tank ventilation valve and the intake manifold, and a partial-load scavenging path (15) arranged between the fuel tank ventilation valve and the intake manifold. To diagnose the scavenging path, multiple sub-diagnoses are performed sequentially in time with the fuel tank ventilation function activated, and pressure signals measured by means of the pressure sensor are evaluated within the scope of the sub-diagnoses. Furthermore, an apparatus for diagnosing the scavenging path of a fuel tank ventilation system in a motor vehicle operating in a combustion engine mode is disclosed.

Description

Technical Field

[0001] This invention relates to a method and apparatus for diagnosing the scavenging pipe path of the fuel tank ventilation system in a motor vehicle operating in a combustion engine mode. Background Technology

[0002] To limit harmful emissions, modern motor vehicles operating with combustion engines are equipped with fuel tank ventilation systems. The purpose of these systems is to absorb and temporarily store fuel vapor formed in the fuel tank due to evaporation, preventing it from leaking into the surrounding environment. A fuel vapor retention filter, such as an activated carbon filter, is incorporated into the fuel tank ventilation system as a storage device for fuel vapor. This filter has a limited storage capacity for fuel vapor. To enable long-term use, the fuel vapor retention filter must be regenerated. For this purpose, a controllable fuel tank vent valve is arranged in the scavenging line path between the fuel vapor retention filter and the intake manifold of the internal combustion engine. This valve is opened to perform regeneration, allowing the fuel vapor adsorbed in the filter to leak into the intake manifold due to the negative pressure, and thus be supplied to the intake air of the internal combustion engine and subsequently to the combustion chamber. Simultaneously, the fuel vapor retention filter's absorption capacity for fuel vapor is restored.

[0003] exist Figure 1 The image shows an example of a known motor vehicle with a fuel tank ventilation system that operates in a combustion engine manner. Figure 1 The system shown in particular has the following components:

[0004] - Fuel tank 22;

[0005] -Activated carbon filter 3, which binds hydrocarbons from exhaust gas from fuel tank 22;

[0006] - Fuel tank vent valve 6, which is controlled by engine control unit 23 by means of pulse width modulation signal (PWM signal) to regulate the airflow from activated carbon filter 3 through full load scavenging path 14 or partial load scavenging path 15 to intake manifold 24 of combustion engine.

[0007] - A branch of the scavenging line path with check valves 7 and 8 is provided downstream of the tank vent valve 6. By means of the branch, airflow is either delivered to the inlet point downstream of the throttle valve 21 via the partial load scavenging path 15 or to the inlet point upstream of the compressor 25 of the turbocharger via the full load path 14. The turbine 26 is also part of the turbocharger.

[0008] -Intake manifold 24, which extends from air filter 20 via compressor 25 and throttle valve 21 to engine assembly 18;

[0009] - Venturi nozzle 9, which generates the necessary pressure difference across the full-load scavenging path 14 under boost pressure above ambient pressure and unthrottled engine operation.

[0010] - Pressure sensor 4 is connected to the full-load scavenging path for pipeline diagnostics of the full-load scavenging path;

[0011] - Fuel tank leak diagnostic component 2, which is connected to air filter 1 via fresh air duct 10 and activated carbon filter 3 via fresh air duct 11, is used to perform fuel tank leak diagnosis and is implemented, for example, as an electric pump unit;

[0012] - An injection system that injects the amount of fuel determined by the engine control unit 23 into the cylinders of the engine assembly 18;

[0013] - A λ-sensor 27 is arranged in the exhaust passage 19 of a motor vehicle to determine the residual oxygen content in the exhaust gas;

[0014] -Fuel tank level sensor 5;

[0015] - Fuel tank ventilation pipe 12 leading from fuel tank 22 to activated carbon filter 3;

[0016] -The scavenging pipeline path area 13 from the activated carbon filter 3 to the oil tank vent valve 6, and

[0017] - Pressure sensor 17 connected to intake manifold 24 is used to measure intake manifold pressure.

[0018] Engine control unit 23 is specifically designed for

[0019] - Determine the rated values ​​for the scavenging airflow from activated carbon filter 3 to the intake manifold of the combustion engine based on the current operating conditions.

[0020] - The intake manifold pressure is determined using pressure sensor 17.

[0021] - The PWM value for controlling the tank vent valve 6 is determined from the pressure drop between the ambient pressure and the pressure at the corresponding inlet point in the intake manifold from a pre-given scavenging flow.

[0022] - Determine the amount of fuel to be injected based on the current operating status of the engine.

[0023] - Determine the delay time for the airflow delivered to the combustion unit by opening the fuel tank vent valve 6 at the two inlet points mentioned above for fuel tank ventilation, and

[0024] - The hydrocarbon concentration calculation based on scavenging mass flow, using λ-adjustment bias learning, is used to correct the amount of fuel to be injected.

[0025] According to the specific national laws, the functional capability of the scavenging air pipeline path must be guaranteed or diagnosed. A sufficiently large mass throughput must always be provided from the activated carbon filter 3 to the intake manifold 24 of the combustion engine to keep hydrocarbon emissions from the fuel tank ventilation system as low as possible.

[0026] For this purpose, it is necessary to test the functionality of the entire scavenging path, consisting of a partial-load scavenging path 15, a full-load scavenging path 14, and a scavenging line path, in which a tank vent valve 6 is arranged. If the Venturi nozzle 9 used to generate sufficient scavenging pressure drop produces a pressure difference relative to the environment under high engine loads that is greater than the pressure difference existing between the branch point downstream of the throttle valve 21 and the environment, then the full-load scavenging path becomes active. If the ratio of full-load scavenging air volume to total scavenging air volume exceeds a prescribed threshold in a pre-defined permissible cycle, the full-load scavenging path in the tank venting system must be diagnosed according to applicable legal regulations.

[0027] With the check valve 8 open, the partial load scavenging path 15 is diagnosed by energizing the tank vent valve 6 in a defined operating mode and evaluating the pressure curve obtained from it in the intake manifold 24 using the pressure sensor 17.

[0028] Diagnostic testing of the full-load scavenging path 14 is performed using pressure sensor 4 connected to the full-load scavenging path. Here, with the full-load scavenging path activated and check valve 7 open, tank vent valve 6 is energized in a pre-defined operating mode, and the resulting pressure curve is evaluated.

[0029] The described process for scavenging path diagnostics has drawbacks. Each diagnostic attempt interrupts other diagnostic functions, such as λ probe diagnostics or catalytic converter diagnostics. Furthermore, each diagnostic attempt interrupts the tank venting function, potentially significantly reducing the amount of scavenging air within the driving cycle. Additionally, diagnostics for partial and full-load scavenging paths require very stable or restricted combustion engine-like operating conditions, resulting in a high number of diagnostic initiations and interruptions overall. Moreover, tank venting valve operation with a large opening stroke is required to obtain noticeable or measurable pressure changes in the intake manifold 24 and in the full-load scavenging path 14. These pressure changes can negatively impact driving performance and exhaust emissions due to the effects of mixture formation under specific conditions. The aforementioned operating mode of the tank venting valve must be suspended from a specific hydrocarbon concentration in the mass flow through the tank venting valve to prevent undesirable driving performance and emissions effects, and diagnostics cannot be activated in the corresponding current driving cycle, resulting in a reduced activation rate of diagnostics overall. Furthermore, in the case of the procedure described in the scavenging line diagnostics, it is not possible to distinguish between a stuck tank vent valve in the open state and a closed scavenging line path.

[0030] While attempts have been made to meet legislative requirements regarding the activation ratio of scavenging line diagnostics and the minimum scavenging air volume through the fuel tank vent valve, through very high calibration and coordination costs when setting up diagnostic functions, and further attempts have been made to reduce undesirable driving performance and emissions impacts throughout the application process, these measures have not yet yielded the desired success. Summary of the Invention

[0031] The objective of this invention is to describe a method and apparatus for diagnosing the scavenging path of a fuel tank ventilation system in a motor vehicle operating in a combustion engine mode, wherein the scavenging path can be diagnosed when the fuel tank ventilation function is activated without requiring a separate operation of the fuel tank ventilation valve.

[0032] This task is accomplished by a method having the features described in claim 1 and an apparatus having the features described in claim 19. Advantageous designs and improvements of the invention are described in the dependent claims.

[0033] In this invention, the scavenging line path is diagnosed using four sub-diagnoses, each measuring the pressure at a pressure sensor located between the activated carbon filter and the tank vent valve. This allows for diagnosis of the scavenging line path while the tank vent function is activated, without requiring a separate operation of the tank vent valve. Attached Figure Description

[0034] The following is based on Figures 1 to 5 The invention is illustrated by way of example. Wherein

[0035] Figure 2 An embodiment of the apparatus according to the invention for diagnosing the scavenging duct path of the fuel tank ventilation system of a motor vehicle driven by a combustion engine is shown.

[0036] Figure 3 A flowchart illustrating the diagnostic process is shown.

[0037] Figure 4 A graph is shown illustrating the different ranges of the operating range of pulse width modulation, and

[0038] Figure 5 A graph is shown to illustrate the different pressure curves. Detailed Implementation

[0039] Figure 2 An example of a motor vehicle with a fuel tank ventilation system that operates in a combustion engine mode is shown, wherein a method for diagnosing the scavenging duct path of the fuel tank ventilation system according to the present invention can be performed.

[0040] Figure 2 The system shown has the following components:

[0041] - Fuel tank 22;

[0042] - As a fuel vapor retention filter implemented as activated carbon filter 3, it incorporates hydrocarbons exhausted from fuel tank 22;

[0043] -Intake manifold 24, which extends from air filter 20 via compressor 25 and throttle valve 21 to engine assembly 18;

[0044] - Fuel tank vent valve 6, which is controlled by engine control unit 23 by means of pulse width modulation signal (PWM signal) to regulate the airflow from activated carbon filter 3 to intake manifold 24 via partial load scavenging path 15 or full load scavenging path 14, wherein full load scavenging path 14 leads to intake manifold 24 via venturi nozzle 9 and high pressure line 16.

[0045] - A branch of the scavenging line path with check valves 7 and 8 is provided downstream of the tank vent valve 6. By means of the branch, the airflow is either delivered to the inlet point downstream of the throttle valve 21 via the partial load scavenging path 15 or to the inlet point upstream of the throttle valve 21 via the full load scavenging path 14.

[0046] - Venturi nozzle 9, which generates the necessary pressure difference across the full-load scavenging path 14 under boost pressure above ambient pressure and unthrottled engine operation.

[0047] - Pressure sensor 28 is arranged between activated carbon filter 3 and oil tank ventilation valve 6;

[0048] -The scavenging pipeline path area 29 is arranged between the activated carbon filter 3 and the oil tank vent valve 6 upstream of the pressure sensor 28;

[0049] -The scavenging pipeline path area 30 is arranged between the activated carbon filter 3 and the oil tank vent valve 6 downstream of the pressure sensor 28.

[0050] - Fuel tank leak diagnostic component 2, which is connected to air filter 1 via fresh air duct 10 and activated carbon filter 3 via fresh air duct 11, is used to perform fuel tank leak diagnosis and is implemented, for example, as an electric pump unit;

[0051] - An injection system that injects the amount of fuel determined by the engine control unit 23 into the cylinders of the engine assembly 18;

[0052] - A λ-sensor 27 is arranged in the exhaust passage 19 of a motor vehicle to determine the residual oxygen content in the exhaust gas;

[0053] -Fuel tank level sensor 5;

[0054] - Fuel tank ventilation pipe 12 leading from fuel tank 22 to activated carbon filter 3;

[0055] - Pressure sensor 17 connected to intake manifold 24 is used to measure intake manifold pressure.

[0056] Engine control unit 23 is specifically designed for

[0057] - Determine the rated values ​​for the scavenging airflow from activated carbon filter 3 to the intake manifold of the combustion engine based on the current operating conditions.

[0058] - The intake manifold pressure is determined using pressure sensor 17.

[0059] - The PWM value for controlling the tank vent valve 6 is determined from the pressure drop between the ambient pressure and the pressure at the corresponding inlet point in the intake manifold from a pre-given scavenging flow.

[0060] - Determine the amount of fuel to be injected based on the current operating status of the engine.

[0061] - Determine the delay time for the airflow delivered to the combustion unit by opening the fuel tank vent valve 6 at the two inlet points mentioned above for fuel tank ventilation, and

[0062] - The hydrocarbon concentration calculation based on scavenging mass flow, using λ-adjustment bias learning, is used to correct the amount of fuel to be injected.

[0063] Figure 2 The device shown is with Figure 1 The difference of the device shown is particularly that the device does not have... Figure 1 The pressure sensor 4 shown is arranged in the scavenging duct of the full-load ventilation path 14. Alternatively, pressure sensor 28 is arranged between the activated carbon filter 3 and the tank vent valve 6. Within the scope of the sub-diagnostics mentioned above, pressure measurement is performed by means of this pressure sensor 28 without the need for separate operation of the tank vent valve.

[0064] In the case of sub-diagnosis A, the partial load scavenging path 15 (including the check valve) located downstream of the tank vent valve 6 is inspected, as well as the presence of the tank vent valve 6 stuck in the closed state is checked.

[0065] In the case of sub-diagnosis B, the full-load scavenging path 14 (including the check valve) arranged downstream of the tank vent valve 6 is inspected, as well as the presence of the tank vent valve 6 stuck in the closed state is checked.

[0066] In the case of sub-diagnosis C, an inspection is conducted given the presence of the tank vent valve 6, which is stuck in the open state.

[0067] In the case of sub-diagnosis D, the following check is performed: whether the scavenging pipeline path area 29 located upstream of pressure sensor 28 is blocked.

[0068] The presence of a leak upstream of the fuel tank vent valve 6 into the environment is located using the fuel tank leak diagnostic component 2. This type of leak is not the subject of this invention and is therefore not described in detail.

[0069] Table 1 below shows the breakdown, which indicates which sub-regions of the complete scavenging tubing path are examined in which sub-diagnoses.

[0070] Table 1:

[0071]

[0072] **: Leakage Inspection

[0073] To ensure accurate pinpointing of the defective components listed in Table 1 above, perform the diagnostic procedure sequence described below:

[0074] 1. Diagnosis D:

[0075] The following inspection is performed given the presence of a blocked scavenging line path area 29 upstream of pressure sensor 28 (Step 1):

[0076] To check for the presence of a blocked scavenging pipeline path region 29 upstream of pressure sensor 28, pressure is measured using pressure sensor 28 with the tank vent function activated and the tank vent valve controlled as permeable, where a significant mass flow is set. After reaching the settable mass flow integral (in the event of a fault, evacuating the pipeline volume downstream of the blockage up to tank vent valve 6), the pressure measured by pressure sensor 28 in the scavenging pipeline path region 29 is compared with the corresponding pressure at the inlet point of the currently activated scavenging path (full-load scavenging path 14 or partial-load scavenging path 15). When the pressure measured by pressure sensor is close to the pressure at the corresponding inlet point, the presence of a blocked scavenging pipeline path upstream of pressure sensor 28 can be inferred. A prerequisite for initiating this sub-diagnosis is a sufficiently large, settable pressure difference between the ambient pressure and the pressure at the corresponding activated inlet point, allowing for the measurement of a significant negative pressure using pressure sensor 28.

[0077] 2. Diagnosis C:

[0078] In light of the presence of the fuel tank ventilation valve 6 stuck in the open state, an inspection is conducted (step 2):

[0079] To check for the presence of a stuck fuel tank vent valve 6 in the open state, pressure is measured using pressure sensor 28, where the fuel tank ventilation function does not operate the fuel tank vent valve 6. If the fuel tank vent valve 6 closes within an adjustable time, the pressure signal measured by pressure sensor 28 in the nominal system condition is close to the ambient pressure because the activated carbon filter 3 is directly connected to the ambient air. In the case of a stuck fuel tank vent valve 6 in the open state, a negative pressure is formed based on the pressure difference between the ambient pressure and the corresponding activated inlet point, as well as the current operating level of the fuel tank vent valve. Here, a settable negative pressure threshold is used to determine the presence of a stuck fuel tank vent valve in the open state. A prerequisite for initiating this diagnosis is a sufficiently large pressure difference between the ambient pressure and the corresponding activated inlet point, settable by the diagnostic algorithm, so that a significant negative pressure can be measured by pressure sensor 28.

[0080] 3. Diagnosis A / B:

[0081] Inspect the scavenging line path downstream of the fuel tank vent valve (steps 3 and 4):

[0082] After checking the scavenging line path upstream of pressure sensor 28 in case of blockage and after ruling out the possibility that the tank vent valve 6 is stuck in its open position, pressure balance towards ambient pressure is ensured even when the tank vent valve 6 is uncontrolled. This allows for comparison of the pressure signal measured by pressure sensor 28 in both uncontrolled and controlled tank vent valve 6 situations to check the scavenging line path downstream of tank vent valve 6. For this purpose, in the case of uncontrolled tank vent valve 6, the initial pressure is measured based on the pressure measured by pressure sensor 28. Furthermore, a preset settable time is given during which tank vent valve 6 is closed. During the subsequent state when tank vent valve 6 is open, the pressure signal measured by pressure sensor 28 is compared again with the previously measured initial pressure after the preset opening time. Due to the decrease in static pressure in the scavenging line path upstream of tank vent valve 6 under nominal system conditions, a minimum negative pressure must be set at pressure sensor 28 based on the pressure difference present at the activated inlet points. Even in this case, a pressure threshold that can be set via a diagnostic algorithm is pre-defined. If this minimum negative pressure is not reached, the presence of a defective scavenging line path downstream of the tank vent valve 6 is inferred, or the presence of a stuck tank vent valve 6 in the closed state is inferred. Whether to check the partial load scavenging path 15 or the full load scavenging path 14 first in this action depends on which engine conditions first occur in the current driving cycle.

[0083] The diagnostic procedure sequence described above is as follows: Figure 3 This will be explained.

[0084] The diagnostic procedure sequence begins by inquiring whether suitable initiation conditions exist for scavenging line diagnostics. If such suitable initiation conditions exist, the process proceeds to the first sub-diagnostic D, which checks for blockages in the scavenging line path region 29 upstream of pressure sensor 28.

[0085] If a blockage is detected in the scavenging line path area 29 during this check, a fault exists and the scavenging line diagnostic ends. If no blockage is detected in the scavenging line path area 29 during this check, no fault exists and the process proceeds to the second sub-diagnostic C. In this sub-diagnostic C, it is checked whether the tank vent valve 6 is stuck in the open state.

[0086] If a stuck fuel tank vent valve 6 in the open state is identified during this check, a fault exists, and the purging line diagnostic ends. If no stuck fuel tank vent valve 6 in the open state is identified during this check, no fault exists, and the process proceeds to an inquiry, in which it is checked whether a pre-defined activation condition exists for the third sub-diagnostic A or the fourth sub-diagnostic B.

[0087] If an activation condition for the third sub-diagnosis A is identified during the inquiry, the process proceeds to that third sub-diagnosis. In this third sub-diagnosis A, the partial load scavenging path 15 located downstream of the tank vent valve 6 is examined, taking into account the presence of the tank vent valve 6 stuck in the closed state.

[0088] If a defective partial load scavenging path 15 and / or a stuck tank vent valve 6 in the closed state are identified during these checks, a fault exists and the scavenging line diagnosis ends. If no defective partial load scavenging path or stuck tank vent valve in the closed state is identified during these checks, the process proceeds to the fourth sub-diagnosis B once the activation condition for the fourth sub-diagnosis B is met.

[0089] In this fourth sub-diagnosis B, the full-load scavenging path 14 arranged downstream of the tank vent valve 6 is inspected, and the presence of the tank vent valve stuck in the closed state is also checked.

[0090] If a defective full-load scavenging path 14 and / or a stuck tank vent valve 6 in the closed state are identified during these checks, the presence of a fault is confirmed, and the scavenging line diagnosis ends. If no defective full-load scavenging path or stuck tank vent valve in the closed state is identified during these checks, the entire scavenging line is considered fault-free. In this case, the method for diagnosing the scavenging line also ends.

[0091] If, when querying whether a pre-defined activation condition exists for the third sub-diagnosis A or the fourth sub-diagnosis B, an activation condition for the fourth sub-diagnosis is identified, then the process proceeds to that fourth sub-diagnosis. In this fourth sub-diagnosis B, the full-load scavenging path 14 located downstream of the tank vent valve 6 is examined, and the presence of the tank vent valve 6 stuck in the closed state is also examined.

[0092] If a defective full-load scavenging path 14 and / or a stuck tank vent valve 6 in the closed state are identified during these checks, a fault exists and the scavenging line diagnostic ends. If no defective full-load scavenging path or stuck tank vent valve in the closed state is identified during these checks, the process proceeds to the third sub-diagnostic A once the activation condition for the third sub-diagnostic is met.

[0093] In this third sub-diagnosis A, the partial load scavenging path 15 located downstream of the tank vent valve 6 is examined, and the presence of the tank vent valve stuck in the closed state is also inspected.

[0094] If a defective partial-load scavenging path 15 and / or a stuck tank vent valve 6 in the closed state are identified during these checks, the presence of a fault is confirmed, and the scavenging line diagnosis ends. If no defective partial-load scavenging path or stuck tank vent valve in the closed state is identified during these checks, the entire scavenging line is considered fault-free. In this case, the method for diagnosing the scavenging line also ends.

[0095] The method described above has several advantages.

[0096] One advantage is that the diagnostic function is executed through defined implementation logic without actively interfering with the fuel tank ventilation function. This results in an increased fuel tank ventilation scavenging rate during the driving cycle.

[0097] Furthermore, the sequential execution of single diagnostic steps ensures accurate and precise location of defective components or pipe sections within the scavenging pipeline path. Therefore, a blocked scavenging pipeline path can be distinguished from a stuck tank vent valve 6 in the open state.

[0098] Another advantage is that there is no interruption of competing diagnostic functions, such as λ probe diagnostics and catalytic converter diagnostics.

[0099] Furthermore, it avoids undesirable driving performance and environmental impacts caused by the active distribution of the control curve of the fuel tank vent valve.

[0100] Furthermore, since the pressure profile directly upstream of the tank vent valve 6 can be evaluated with a small mass flow through the tank vent valve 6 and a small control duty cycle obtained therefrom, scavenging line diagnostics can be performed even when there is a high concentration of scavenging medium in the scavenging medium.

[0101] Furthermore, the described method can be used to distinguish between the tank vent valve 6 stuck in the open state and the closed scavenging line path or the closed tank vent valve 6.

[0102] The above describes a method and apparatus for diagnosing the scavenging path of a fuel tank ventilation system in a motor vehicle operating in a combustion engine mode, wherein the scavenging path can be diagnosed when the fuel tank ventilation function is activated without requiring a separate operation of the fuel tank ventilation valve.

[0103] When the tank vent valve 6 is configured as a shift control valve (Schaltventil), significant pressure pulsations are generated upstream of the tank vent valve 6 at the scavenging line sensor system, i.e., pressure sensor 28, during operation. This may result in the average pressure signal being robustly evaluated only at high control ratios. At low control ratios, an average line pressure is set that roughly corresponds to ambient pressure, i.e., the pressure taken when the tank vent valve 6 is at rest. This makes robust evaluation difficult.

[0104] To ensure robust evaluation, a special evaluation strategy for scavenging line pressure is proposed according to one embodiment of the invention. This special evaluation strategy enables robust implementation of the aforementioned passive scavenging line diagnostics for verifying partial and full load paths, even under low control ratios of the fuel tank vent valve 6 and an expanded operating range of the combustion engine.

[0105] For this purpose, Figure 4 The control range shown, namely the pulse width modulation (PWM) operating range of the fuel tank vent valve 6, is divided into three ranges: B1, B2, and B3. Here, the calibrable setting parameters PAR_1 and PAR_2, stored in the engine control as a family of characteristic curves, constitute the range limits. These setting parameters are related, for example, to the engine load, the pressure difference across the corresponding activated scavenging line, and the activation state of the scavenging line.

[0106] Range B1:

[0107] If the control ratio does not exceed the threshold defined under PAR_1, no assessment of the scavenging line pressure is performed. The control level of the tank vent valve 6 is too low within this range for a robustly measurable pressure change to be obtained at the pressure sensor 28 after the tank vent valve 6 is opened.

[0108] Range B2:

[0109] If the operation of the tank vent valve 6 is within range B2, which is the intermediate (mittleren) operating range of the tank vent valve 6 limited by parameters PAR_1 and PAR_2, then the pressure peak appearing at the pressure sensor 4 is evaluated according to the following scheme in order to perform partial load and full load path verification:

[0110] First, ensure that the sampling rate of the pressure signal measured by the pressure sensor 28 and the computational grid for implementing the diagnostic function follow the Nyquist-Shannon sampling theorem, which guarantees that there must be an implementation frequency that is at least twice the expected pressure signal frequency, generated by the timing of the tank vent valve 6.

[0111] - The entry point for the diagnostic process is the closed tank vent valve 6. Here, with the tank vent valve 6 unoperated, the initial pressure is measured based on the current pressure signal measured by pressure sensor 28. Figure 5 In this context, the pressure is represented by "X".

[0112] - Following the activation of the tank vent valve control within the range between PAR_1 and PAR_2, the minimum (“Y”) and maximum (“Z”) pressures reached at pressure sensor 28 are stored within a settable time. At the start of diagnostics, the “Y” and “Z” values ​​are initialized to the initial pressure “X”. This is in Figure 5 The diagram clarifies this, showing the curve of ambient pressure p1, the curve of measured scavenging line pressure p2 with the measured minimum pressures Y1, Y2 and Y... and the measured maximum pressures Z1, Z2 and Z..., and the curve of average scavenging line pressure p3.

[0113] Finally, the criteria for a good or bad test are based on the difference between the determined minimum (“Y”) and maximum (“Z”) values. If the difference between the minimum and maximum values ​​measured during a settable time period exceeds the settable parameter PAR_4, it is inferred that a functional tank ventilation path, including the tank vent valve 6, exists.

[0114] - For example: MAX(Z)-MIN(Y)>PAR_4 is suitable for good testing.

[0115] - For example: MAX(Z)-MIN(Y)<=PAR_4 is suitable for bad testing.

[0116] - Instead of the pressure difference formation described above regarding good or bad tests, any combination of minimum or maximum pressures within the recorded pressure peaks can be applied.

[0117] For example: MIN(Z) - MAX(Y)

[0118] - In one particular implementation of the diagnostics, a defined number of good tests can be calibrated before inferring the functional tank ventilation path.

[0119] Range B3:

[0120] The pressure signal measured by pressure sensor 28 is compared to the pressure signal measured by the uncontrolled tank vent valve 6 and the controlled tank vent valve 6 to inspect the scavenging line downstream of the tank vent valve 6. Here, the control level must at least exceed PAR_2. Therefore, in the case of the uncontrolled tank vent valve 6, the initial pressure is measured based on the pressure signal at pressure sensor 28. Furthermore, the tank vent valve 6 is closed for a predetermined settable time. In the subsequent state where the tank venting function is on and the tank vent valve 6 is open, where the control level must again exceed parameter PAR_2, after a settable opening time, the pressure value measured by pressure sensor 28 is compared with the previously measured initial pressure. Due to the static pressure drop in the nominal system in the scavenging line upstream of the tank vent valve 6, a minimum negative pressure must be set at pressure sensor 28 based on the pressure difference present at the activated inlet points. A settable pressure threshold is also predetermined for this purpose. If this minimum pressure is not reached, it can be inferred that there is a defective scavenging line downstream of the tank vent valve 6 or that the tank vent valve 6 is stuck in the closed state. Whether to first perform a partial load path or a full load path test depends on which engine conditions first occur in the current driving cycle.

[0121] After activating diagnostics in range B2 or B3, the tank vent valve does not need to be closed before entering range B1 again. This means that switching the pressure assessment functionality for range B2 or B3 is seamlessly performed by setting parameter PAR_2 without re-initializing the diagnostic function (measurement of the initial pressure).

[0122] The behavior described above has the following advantages:

[0123] -Due to the splitting of the pressure assessment range and the related application of the pressure assessment functionality shown, the described passive tank ventilation diagnostic function can also be implemented at a small level of control of the tank vent valve and over a very wide operating range of the combustion engine.

[0124] - The diagnostic function is performed in all physically assessable operating ranges without actively interfering with the fuel tank ventilation function, which results in an increased fuel tank ventilation scavenging rate during driving cycles.

[0125] - In addition, competitive diagnostic functions such as λ probe diagnostics and catalytic converter diagnostics are not interrupted by scavenging pipeline diagnostics.

[0126] - In addition, it eliminates the impact on driving performance and emissions caused by the active distribution (Absetzen) of the control curve to the fuel tank vent valve.

[0127] -Because the pressure profile immediately preceding the tank vent valve 6 can be evaluated with a small mass flow through it and a small control duty cycle, scavenging line diagnostics can be performed even at high concentrations of the scavenging medium.

[0128] - In the case of the described behavior, the tank vent valve 6 stuck in the open state can be distinguished from the closed scavenging line path or the closed tank vent valve 6.

[0129] List of reference numerals

[0130] 1 air filter

[0131] 2. Fuel Tank Leak Diagnostic Components

[0132] 3 Activated Carbon Filter

[0133] 4 pressure sensors

[0134] 5. Oil tank level sensor

[0135] 6. Fuel tank ventilation valve

[0136] 7 Check Valve

[0137] 8 Check Valve

[0138] 9 Venturi nozzles

[0139] 10 Fresh Air Ducts

[0140] 11 Fresh air ducts

[0141] 12 Fuel Tank Ventilation Pipeline

[0142] 13 Scavenging pipeline route area

[0143] 14 Full-load scavenging path

[0144] 15 Partial Load Scavenging Paths

[0145] 16 High-pressure pipelines

[0146] 17 pressure sensors

[0147] 18 engine sets

[0148] 19 exhaust channels

[0149] 20 air filters

[0150] 21 Throttle Valve

[0151] 22 fuel tanks

[0152] 23 Engine Control Unit

[0153] 24 intake manifold

[0154] 25 compressor

[0155] 26 turbines

[0156] 27λ-sensor

[0157] 28 pressure sensors

[0158] 29 Pressure sensor 28 Upstream scavenging pipeline path area

[0159] 30 Pressure sensor 28 Downstream scavenging pipeline path area.

Claims

1. A method for diagnosing a scavenge line path of an oil tank ventilation system of a motor vehicle operating in the manner of a combustion engine, wherein the scavenge line path extends between a fuel vapor retention filter (3) and an intake manifold (24) of the motor vehicle and has an oil tank ventilation valve (6), a pressure sensor (28) arranged between the fuel vapor retention filter and the oil tank ventilation valve, a scavenge line path region (29) arranged upstream of the pressure sensor, a scavenge line path region (30) arranged downstream of the pressure sensor between the fuel vapor retention filter (3) and the oil tank ventilation valve (6), a full-load scavenge path (14) arranged upstream of a throttle valve (21) between the oil tank ventilation valve (6) and the intake manifold (24), and a partial-load scavenge path (15) arranged downstream of a throttle valve (21) between the oil tank ventilation valve and the intake manifold (24), characterized in that, For diagnosing the scavenge line path, a plurality of sub-diagnoses are executed in time one after the other in a predefined diagnostic flow sequence, wherein in a first sub-diagnosis the presence of a blockage arranged in the scavenge line path region (29) upstream of the pressure sensor (28) is checked, and in the event of recognition of the absence of a blockage arranged in the scavenge line path region (29) upstream of the pressure sensor (28) in a second sub-diagnosis the presence of a stuck open tank ventilation valve (6) is checked, wherein the sub-diagnoses are executed in the event of an activated tank ventilation function and in the scope of the sub-diagnoses an evaluation of a pressure signal measured by means of a pressure sensor (28) arranged between the fuel vapor retention filter (3) and the tank ventilation valve (6) takes place.

2. The method of claim 1, wherein, The sub-diagnoses are executed in the event of an activated tank ventilation function without a separate actuation process of the tank ventilation valve.

3. The method of claim 1, wherein, In the event of recognition of the presence of a blockage arranged in the scavenge line path region (29) upstream of the pressure sensor (28) the diagnosis of the scavenge line path is ended.

4. The method of claim 1, wherein, In the event of recognition of the presence of a stuck open tank ventilation valve (6) the diagnosis of the scavenge line path is ended.

5. The method of claim 1, wherein, In the event of recognition of the absence of a stuck open tank ventilation valve (6) a check is made as to whether there is an activation condition for a third sub-diagnosis or for a fourth sub-diagnosis.

6. The method of claim 5, wherein, In the event of recognition of the presence of an activation condition for the third sub-diagnosis a transition into the third sub-diagnosis takes place.

7. The method of claim 6, wherein, In the third sub-diagnosis a check is made of the partial load scavenge path arranged downstream of the tank ventilation valve and of the presence of a stuck closed tank ventilation valve.

8. The method of claim 7, wherein, In the event of recognition of a defective partial load scavenge path and / or a stuck closed tank ventilation valve (6) the diagnosis of the scavenge line path is ended or alternatively a fourth sub-diagnosis is continued.

9. The method of claim 7, wherein, In the event of recognition of the absence of a defective partial load scavenge path and a stuck closed tank ventilation valve a transition into the fourth sub-diagnosis takes place in the event of an activation condition for the fourth sub-diagnosis.

10. The method of claim 9, wherein, In the event of recognition of the presence of an activation condition for the fourth sub-diagnosis a transition into the fourth sub-diagnosis takes place.

11. The method of claim 10, wherein, In the fourth sub-diagnosis a check is made of the full load scavenge path arranged downstream of the tank ventilation valve (6) and of the presence of a stuck closed tank ventilation valve.

12. The method according to any of the preceding claims, characterized in that, The pulse width actuation range of the tank ventilation valve (6) is divided into a plurality of ranges (B1, B2, B3), wherein the pressure signal measured by the pressure sensor (28) is evaluated differently.

13. The method of claim 12, wherein, In a first range (B1) an evaluation of the pressure signal measured by the pressure sensor (28) is not taken into account.

14. The method of claim 12, wherein, In a second range (B2) a pressure peak of the pressure signal measured by the pressure sensor (28) is evaluated in order to execute a diagnosis of the full load scavenge path (14) and the partial load scavenge path (15).

15. The method of claim 12, wherein, In a third range (B3), the average pressure signal measured by the pressure sensor (28) is evaluated for diagnosing the scavenge line path downstream of the oil tank ventilation valve (6) both in the case of an uncontrolled oil tank ventilation valve (6) and in the case of a controlled oil tank ventilation valve (6).

16. A device for diagnosing a scavenge line path of an oil tank ventilation system of a motor vehicle operating in the manner of a combustion engine, wherein the scavenge line path extends between a fuel vapor retention filter (3) and an intake manifold (24) of the motor vehicle and has an oil tank ventilation valve (6), a pressure sensor (28) arranged between the fuel vapor retention filter and the oil tank ventilation valve, a scavenge line path region (29) arranged upstream of the pressure sensor between the fuel vapor retention filter (3) and the oil tank ventilation valve (6), a scavenge line path region (30) arranged downstream of the pressure sensor, a full-load scavenge path (14) arranged upstream of the throttle valve (21) between the oil tank ventilation valve and the intake manifold (24), a partial-load scavenge path (15) arranged downstream of the throttle valve (21) between the oil tank ventilation valve (6) and the intake manifold (24), and an engine control device (23) which is configured to control a method according to any one of claims 1 to 15.

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