Method for checking functionality of controllable shut-off valve in tank exhaust system

Abstract

The invention discloses a method for checking the functional capability of a controllable shut-off valve (1400) in a tank exhaust system (1000). The tank exhaust system is provided with a tank area (1200); a reservoir region (1100) with a fuel vapor reservoir (1110); a controllable shut-off valve (1400) located in a bleed line (1300) connecting the fuel vapor reservoir (1110) and the fuel tank (1210); and a pressure change device (1800) for changing the pressure in the memory region (1100); and a pressure detection device (1500) having a reservoir pressure detection device (1510) and a tank pressure detection device (1520). In the method, a pressure detection device (1500) is activated, and the shut-off valve (1400) is controlled with respect to the closed state or the closed target state thereof is detected. According to the invention, the pressure change device (1800) is operated with respect to changing the pressure in the memory region (1100), and a pressure profile in the memory region (1100) is detected in a first time period (T0) and evaluated as to whether a first pressure change in the memory chamber (1100) caused by the operation of the pressure change device (1800) satisfies a first plausibility criterion. The pressure progresses in the reservoir region (1100) and in the tank region (1200) are detected by detecting output signals of the reservoir pressure detection device (1510) and the tank pressure detection device (1520) during the second time period (T1) and the correlation between them is evaluated. A closing failure of the shut-off valve (1400) is identified as a function of the correlation.

Description

Technical Field

[0001] The invention relates to a method for checking the functional capacity of a controllable shut-off valve in a tank venting system, as well as a computer program product and a control device for implementing the method. Background Art

[0002] Legal regulations require that the fuel vapors generated in the fuel tank do not escape into the surroundings in an uncontrolled manner. Vehicles with internal combustion engines are therefore usually equipped with a tank ventilation system. The core element of the tank ventilation system is the fuel vapor accumulator, to which the fuel vapors generated in the fuel tank are fed. The vapors are adsorbed by an adsorbent (usually activated carbon) contained in the fuel vapor accumulator and are thus stored. In order to prevent the adsorbent from becoming saturated, the fuel vapor accumulator must be regenerated from time to time. For this purpose, the fuel vapor accumulator is flushed with fresh air, wherein the stored fuel vapor is fed in a controlled manner to the engine-driven combustion.

[0003] In a purely internal combustion engine-driven vehicle, fuel vapor from the fuel tank is continuously delivered to the fuel vapor storage device. This is feasible because the internal combustion engine is very frequently operated as the only drive source and therefore the regeneration of the fuel vapor storage device does not present a problem. However, in a hybrid drive solution, i.e., a vehicle with an electric motor and an internal combustion engine as drive sources, the driving distance is getting longer and longer without activating the internal combustion engine at all, so the regeneration possibility of the fuel vapor storage device becomes less and less. For this reason, a pressure storage tank solution is now used, which is separated from the fuel vapor storage device by a controllable shut-off valve. In the pressure storage tank, the hydrocarbon vapor released under high pressure is always blocked until the escape of the vapor in the direction of the fuel vapor storage device can be achieved by opening the shut-off valve in a controlled manner.

[0004] Legal regulations require that the function of tank venting systems or their components be checked. The function of the shut-off valve is crucial here, since it must be ensured that the fuel tank is depressurized before the tank cap is opened in order to prevent hydrocarbons from escaping uncontrolled into the environment. Summary of the invention

[0005] The object of the present invention is to provide a method, a computer program product and a control device, by means of which the functional capacity of a shutoff valve of a tank venting system can be checked particularly reliably.

[0006] This object is achieved by the subject matter of the independent claim. Advantageous embodiments of the invention are described in the dependent claims.

[0007] A method is disclosed, which involves checking the functional capability of a controllable shut-off valve in a tank venting system. The tank venting system includes: a tank area with a fuel tank; a storage area with a fuel vapor storage; a venting line connecting the fuel vapor storage and the fuel tank; a controllable shut-off valve, which is arranged in the venting line and prevents pressure balance between the tank area and the storage area in a closed state, and allows pressure balance between the tank area and the storage area in an open state. The tank venting system also includes: a pressure changing device for changing the pressure in the storage area; and a pressure detection device for detecting the pressure in the storage area and for outputting an output value representing the detected pressure.

[0008] The pressure detection device has a storage pressure detection device for detecting the pressure in the storage area and a tank pressure detection device for detecting the pressure in the tank area. In other words, the pressure detection device has a first pressure detection device, which is configured to detect the pressure in the storage area (also referred to as "storage pressure" in this document), and a second pressure detection device, which is configured to detect the pressure in the tank area (also referred to as "tank pressure" in this document). The pressure in the tank area is in particular the pressure in the fuel tank; in the case of liquid fuel, this pressure is expediently the pressure of the gas volume above the liquid level in the fuel tank.

[0009] According to the steps of the method, the pressure detection device is activated.

[0010] In one embodiment of the method, the control of the stop valve in terms of the closed state is implemented in another method step. "Controlling the stop valve in terms of the closed state" is particularly understood to mean sending a control signal to the stop valve, by means of which the closing process of the stop valve is triggered. In the present disclosure, "controlling in terms of the closed state" is also understood to mean, for example, maintaining the closed target state of the stop valve after the vehicle is started and not controlling the stop valve in terms of the open state. In another embodiment of the method, as an alternative or subsequent solution to controlling the stop valve in terms of the closed state, in a method step, it is detected whether there is a closed target state of the stop valve. If there is no closed target state, the method is preferably interrupted or restarted. "The closed target state of the stop valve" is particularly understood to mean the following state, in which the stop valve is not manipulated in terms of the open state. For example, for a valve closed without current, the closed target state is a no-current state. Controlling the stop valve in terms of the closed target state and / or detecting whether there is a closed target state of the stop valve is particularly performed before or after activating the pressure detection device.

[0011] According to a further method step, in particular subsequent to the control of the stop valve with respect to the closed state or the detection of the closed target state, the pressure varying device is operated with respect to changing the pressure in the accumulator area.

[0012] According to a further method step, in particular subsequent to the operation of the pressure variation device, the pressure trend in the storage area is detected by detecting the output signal of the storage pressure detection device within a first time period, and the detected pressure trend is evaluated as follows: whether the first pressure change in the storage chamber caused by the operation of the pressure variation device meets a first credibility criterion. In a refinement of the method, the first credibility criterion is met if the magnitude of the gradient of the pressure trend in the storage area within the first time period remains above a predetermined threshold value during the first time period. In a further refinement, in order to meet the first credibility criterion, it is particularly additionally necessary that the pressure trend within the first time period rises monotonically, that is, the pressure gradient has a positive sign. In a further suitable embodiment of the method, the method is interrupted or restarted if the first credibility criterion is not met. In this way, a high reliability of the method can be advantageously ensured.

[0013] According to a further method step, the pressure trend in the storage area and in the tank area is detected by detecting the output signal of the storage pressure detection device or the tank pressure detection device in a second time period. The second time period can start at the same time as the first time period, during the first time period or after the first time period. In one embodiment of the method, the starting point of the second time period is defined by starting a timer.

[0014] According to a further method step, in particular simultaneously with or subsequently to the determination of the pressure profile within the second time period, a correlation between the pressure profiles determined within the second time period in the accumulator region and in the tank region is evaluated.

[0015] In an expedient embodiment, the pressure trend in the second time period is detected and / or the correlation is evaluated only if the first plausibility criterion is met. In this embodiment, the second time period expediently starts after the first time period, for example directly after the first time period.

[0016] In a further method step, a closing fault of the stop valve is detected based on a correlation between the pressure curves detected in the storage area and in the tank area within a second time period. In this context, a closing fault of the stop valve is understood to be, in particular, a fault of the stop valve in which the sending of a control signal for initiating a closing process of the stop valve does not result in a completely closed state of the stop valve, that is to say, in particular, does not completely prevent a pressure equalization between the tank area and the storage area.

[0017] Check whether the shut-off valve can be placed in the closed state in accordance with the regulations. In the good case, that is, if the shut-off valve can be moved into the closed state in accordance with the regulations, the storage area and the tank area are separated pneumatically. As a result, the effective pneumatic volume on which the pressure variation device acts is reduced to the volume of the storage area. In the bad case, that is, if the shut-off valve is stuck in the open state and the tank area and the storage area are pneumatically connected, the effective pneumatic volume is composed of the volume of the tank area and the volume of the storage area and is therefore significantly larger than the effective pneumatic volume in the good case. In addition, in the good case, due to the pneumatic separation of the storage area and the tank area, pressure fluctuations are not transmitted between the storage area and the tank area. Such pressure fluctuations in the tank area may be caused, for example, by the sloshing of liquid fuel in the fuel tank (for example, due to the movement of the vehicle) or by hydrocarbons released from the liquid fuel. In the bad case, the pressure fluctuations in the tank area may be affected by the storage area and / or vice versa; the pressure fluctuations in the tank area may be buffered, for example, due to the pneumatic connection to the fuel vapor storage.

[0018] Thus, in a good case, the pressure profile in the storage area is less strongly correlated with the pressure profile in the tank area than in a bad case. This different nature of the correlation in a good case and a bad case allows a particularly reliable diagnosis of a shutoff fault of the shutoff valve. In particular, the risk of an erroneous diagnosis due to pressure changes in the tank area is particularly low. In particular, when the method is carried out according to the disclosure, the risk of a shutoff fault not being detected due to high pressure dynamics in the tank area is advantageously very low.

[0019] In one embodiment of the method, a closing fault of the shutoff valve is detected if the gradients of the pressure curves of the pressure in the tank area and the pressure in the storage area have the same sign during the second time period; and the maximum pressure gradient of the pressure in the tank area exceeds a limit value predefined as a function of the maximum pressure gradient of the pressure in the storage area during the second time period; or the difference between the pressure gradient of the pressure in the tank area and the pressure gradient of the pressure in the storage area remains within a predefined tolerance range during the second time period, i.e., in particular at every point in time during the second time period. Otherwise, for example, if the maximum pressure gradient of the pressure in the tank area does not exceed a limit value predefined as a function of the maximum pressure gradient of the pressure in the storage area during the second time period, a closing fault is not detected and the shutoff valve is assumed to be closed in a prescribed manner.

[0020] In one embodiment, the tank area has a fill level sensor. In this case, the method can have an additional step in which a signal of the fill level sensor is detected and the duration of the second time period and / or a threshold value of the first plausibility criterion is predefined as a function of the detected signal of the fill level sensor. Advantageously, in this way, the measuring time of the pressure curve and a minimum pressure gradient suitable for the reliability of the method can be adapted to the dynamics of the pressure fluctuations in the fuel tank, which depends on the fill level of the fuel tank. The inertia of the system and the phase lag in the system can depend on the fill level of the tank, for example.

[0021] In a further embodiment, the method has an additional method step in which the pressure trend in the storage area is detected by means of detecting an output signal of the storage pressure detection device within a third time period, and the detected pressure trend is evaluated as to whether a third plausibility criterion is met. In this case, in particular, if the pressure trend in the storage area detected within the third time period is monotonically rising or monotonically falling, it is assessed that the third plausibility criterion is met. A change in the sign of the slope can be caused, for example, by a change in an operating parameter of the pressure variation device. If the pressure trend is not monotonically rising or falling, there is a risk that the correlation assessment may be distorted, for example due to changes in the phase shift of the pressure trend or due to the inertia of the system.

[0022] In a variant of the design, the third time period overlaps the first and second time periods. For example, the third time period is identical to the second time period, or the third time period is a partial range of the second time period. For example, the starting point of the third time period can also be defined by the start of a timer. In a further variant of the design, the relationship between the pressure trends detected in the storage area and in the tank area during the second time period is evaluated only if a third plausibility criterion is met.

[0023] Advantageously, in this embodiment, the risk of an erroneous diagnosis due to switching processes of the valve in the tank venting system is particularly low.

[0024] In a further embodiment of the method, a fluid mass flow through the storage area is detected during a first time period. The fluid mass flow through the storage area is caused in particular by the operation of the pressure variation device. This fluid mass flow can be used, for example, to flush the fuel vapor storage area. In this embodiment, in order to meet the first credibility criterion, it can be necessary that the fluid mass flow or the time integral of the fluid mass flow within the first time period - that is, in particular the mass of the fluid flowing out of the storage area or flowing into the storage area during the first time period - reaches or exceeds a predetermined minimum value. With this embodiment, an increased reliability of the method can be achieved.

[0025] In one embodiment, the steps of the method are performed repeatedly multiple times, in particular the method as a whole is performed repeatedly multiple times. In this way, a particularly reliable diagnosis of a closing fault of the shutoff valve can be achieved.

[0026] In one embodiment of the method, the following steps are performed if a closing fault of the stop valve is not detected:

[0027] -Control the stop valve in the open state;

[0028] - evaluating the detected output signal of the pressure detection device as follows: whether a second pressure change in the storage chamber caused by the control of the stop valve in the open state satisfies a second plausibility criterion;

[0029] If the evaluation shows that the second plausibility criterion is not met, a fault in the shutoff valve is detected.

[0030] The storage area and the tank area should be pneumatically connected by controlling the stop valve in the open state. In the good case, that is, when the controllable stop valve can be moved to the open position in accordance with the regulations, pressure balance will occur between the tank area and the storage area. The pneumatic volume will suddenly expand the volume of the tank area. In the poor case, that is, when the controllable stop valve cannot be moved to the open position and remains (stuck) in the closed state, pressure balance cannot be achieved between the tank area and the storage area. So the pneumatic volume continues to be limited to the volume of the storage area. In the good case, controlling the stop valve in the open state will cause a significant change in the pressure in the storage area. This effect allows the pressure trend to be verified and the functional capacity of the stop valve to be inferred. If it is identified that the second pressure change does not meet the second credibility standard, the failure of the stop valve is identified. In this poor case, it will be possible to determine that the stop valve can no longer move to the open state or that it is stuck in the closed state.

[0031] According to one design of the method, if

[0032] After the shut-off valve has been activated in the open state, the pressure gradient in the storage area and / or in the tank area changes by at least a predetermined minimum value, or a second pressure gradient in the storage area and / or in the tank area is within a predetermined second pressure gradient value range; or

[0033] After the shut-off valve has been activated in the open state, the pressure in the storage area and / or in the tank area changes by at least a predetermined second minimum value; or the pressure in the storage area and / or in the tank area is within a predetermined second pressure value range; or

[0034] - after the shut-off valve has been activated in the open state, the second pressure curve in the accumulator region and / or in the tank region follows a predefined second reference curve, or the second pressure curve remains within a predefined second tolerance range about the second reference curve,

[0035] The evaluation then indicates that the second credibility criterion is met.

[0036] In one embodiment of the method, the pressure varying device further comprises:

[0037] a ventilation line, via which the fuel vapor accumulator is connected to the surrounding environment;

[0038] a controllable ventilation valve arranged in the ventilation line in order to control the air flow through the ventilation line;

[0039] a vent line, via which the fuel vapor storage device is connected to a negative pressure source;

[0040] a controllable exhaust valve arranged in the exhaust line in order to control the gas flow through the exhaust line,

[0041] In order to change the pressure in the storage area, the ventilation valve is closed and the exhaust valve is opened in order to generate a negative pressure in the storage area.

[0042] By opening the exhaust valve, the storage area is pneumatically connected to a negative pressure source. The negative pressure source can be, for example, an intake pipe of the internal combustion engine, a Venturi nozzle, an intake jet nozzle or a negative pressure pump. In many operating states of the internal combustion engine, a negative pressure is present in the intake pipe of the internal combustion engine downstream of a throttle element arranged therein. By connecting the storage chamber to the intake pipe at this point, an air flow in the direction of the internal combustion engine is generated and evacuation of the storage area is caused. According to this embodiment, activation of the pressure variation device causes a negative pressure in the storage area.

[0043] In other embodiments of the method, the pressure varying device comprises:

[0044] a ventilation line, via which the fuel vapor accumulator is connected to the surrounding environment;

[0045] a controllable ventilation valve arranged in the ventilation line in order to control the air flow through the ventilation line;

[0046] a vent line, via which the fuel vapor storage device is connected to a negative pressure source;

[0047] a controllable exhaust valve arranged in the exhaust line in order to control the gas flow through the exhaust line,

[0048] In order to change the pressure in the storage area, the ventilation valve and the exhaust valve are opened in order to generate a negative pressure in the storage area.

[0049] This embodiment is an alternative to the embodiment described above, in which the ventilation valve is opened instead of closed. This achieves a flushing effect in the fuel vapor accumulator, thereby regenerating the fuel vapor accumulator. Although only a low negative pressure can be generated in this case, a functional check of the shutoff valve can be carried out at the same time during the flushing process of the fuel vapor accumulator, which is required from time to time anyway. In order to generate the strongest possible negative pressure, the vent valve can be opened to the greatest extent, and this process is preferably carried out when the negative pressure generated by the negative pressure source is particularly high.

[0050] In a further embodiment of the method, the pressure varying device has:

[0051] a ventilation line, via which the fuel vapor accumulator is connected to the surrounding environment;

[0052] a controllable ventilation valve arranged in the ventilation line in order to control the air flow through the ventilation line;

[0053] a controllable pump which is arranged in the ventilation line downstream of the ventilation valve in order to pump ambient air from the atmosphere into the fuel vapor accumulator in order to generate an overpressure in the accumulator region;

[0054] a vent line, via which the fuel vapor storage device is connected to a negative pressure source;

[0055] a controllable exhaust valve arranged in the exhaust line in order to control the gas flow through the exhaust line,

[0056] In order to change the pressure in the storage area, the ventilation valve is opened, the exhaust valve is closed and the pump is started in order to generate an excess pressure in the storage area.

[0057] This embodiment is a further alternative to the embodiments according to the two embodiments described above. Pumping ambient air into the storage area would result in an overpressure there.

[0058] In one embodiment of the method, the storage pressure detection device is designed as a virtual sensor. In this case, a physical sensor for detecting the storage pressure in the storage area is advantageously not required, as may be the case in other embodiments of the method. In this way, the method can be carried out particularly cost-effectively. In this embodiment, the output signal of the storage pressure detection device, which represents the pressure in the storage area, is modeled, for example, based on a pressure that is measured downstream of the exhaust valve or is calculated for a position downstream of the exhaust valve as a function of one or more other parameters, for example by means of a trained neural network.

[0059] According to a further aspect, a computer program product is disclosed which can be loaded into a memory of a computer and has software code segments which, when executed on a computer, cause the execution of a method according to at least one of the above-described embodiments, embodiments and variants.

[0060] Furthermore, a data carrier is disclosed, on which a computer program product is stored. In one embodiment, the computer program product contains a characteristic diagram, in particular a calibrated characteristic diagram, for a limit value of the maximum pressure gradient of the pressure in the tank region, which is predetermined as a function of the maximum pressure gradient of the pressure in the storage area, and a threshold value for the gradient magnitude of the pressure curve in the storage area. According to a further aspect, a control device for controlling a tank venting system is disclosed, the control device having a computer and a memory, in which the computer program product is loaded.

[0061] This control device is also designed with all necessary interfaces to be connected to the tank exhaust system. When the control device is running, the computer program product loaded on the control device is run and the method is executed.

[0062] With regard to the advantages of the computer program product and the control device, reference is made to the embodiments regarding the method, which apply in an analogous manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be described in more detail below according to embodiments with reference to the accompanying drawings. In the accompanying drawings:

[0064] Figure 1 A schematic diagram of a tank venting system for a motor vehicle is shown;

[0065] Figure 2 A flow chart illustrating an embodiment of a method for inspecting a tank venting system is shown. DETAILED DESCRIPTION

[0066] exist Figure 1Schematically shown in FIG. 1 is a tank venting system 1000 for a motor vehicle (not shown) having an internal combustion engine 2000 . The tank venting system 1000 has a storage area 1100 and a tank area 1200 .

[0067] In the exemplary embodiment, the tank region 1200 comprises a fuel tank 1210 for storing a fuel 1211 , a filling level sensor 1213 and a delivery pump 1214 for delivering the fuel in the direction of the internal combustion engine 2000 .

[0068] In the exemplary embodiment, storage area 1100 has a fuel vapor storage accumulator 1110 . Fuel vapor storage 1110 is designed as an activated carbon container and serves to temporarily store hydrocarbons released from fuel tank 1210 .

[0069] The storage area 1100 and the tank area 1200 are coupled to each other via a venting line 1300. A controllable stop valve 1400 is arranged in the venting line 1300, which in a closed state prevents pressure equalization between the tank area 1200 and the storage area 1100 and in an open state allows pressure equalization between the tank area 1200 and the storage area 1100. The stop valve 1400 can be designed as a pulse width modulated electric valve.

[0070] The tank venting system 1000 further comprises a ventilation line 1600, via which the fuel vapor storage 1110 is connected to the atmosphere or the surroundings, and a controllable ventilation valve 1610, which is arranged in the ventilation line 1600 in order to control the gas flow through the ventilation line 1600. In the ventilation line 1600, a controllable pump 1620 is also arranged downstream of the ventilation valve 1610, which is used to pump ambient air from the atmosphere into the fuel vapor storage 1110 when the ventilation valve 1610 is open, in order to generate an overpressure in the storage area 1100.

[0071] In addition, the fuel vapor storage device 1110 is connected to the negative pressure source 2100 via the exhaust line 1700. In the present embodiment, the intake pipe 2100 of the internal combustion engine 2000 is used as the negative pressure source. The exhaust line leads into the intake pipe 2100 at a position downstream of a throttle mechanism 2200 (throttle valve), which is arranged in the intake pipe 2100. When the internal combustion engine 2000 is running, there is a negative pressure at this position. As an alternative, a Venturi nozzle or an intake jet nozzle can also be used as a negative pressure source. A controllable exhaust valve 1710 is arranged in the exhaust line 1700, by means of which the air flow through the exhaust line 1700 can be controlled.

[0072] The tank area is defined by the fuel tank 1210 , the shutoff valve 1400 , and the section of the bleed line 1300 located therebetween.

[0073] The storage area is defined by the fuel vapor storage 1110, the shut-off valve 1400, the section of the vent line 1300 located between the fuel vapor storage 1110 and the shut-off valve 1400, the ventilation valve 1610, the section of the ventilation line 1600 located between the fuel vapor storage 1110 and the ventilation valve 1610, the exhaust valve 1710 and the section of the exhaust line 1700 located between the fuel vapor storage 1110 and the exhaust valve 1710.

[0074] The ventilation line 1600, the controllable ventilation valve 1610, the pump 1620, the exhaust line 1700 and the controllable exhaust valve 1710 together form a pressure variation device 1800, by means of which the pressure in the storage area 1100 can be varied. In order to generate an overpressure in the storage area 1100 (relative to the pressure in the tank area 1200), the shutoff valve 1400 is closed, the exhaust valve 1710 is closed, the ventilation valve 1610 is opened, and the pump 1620 is operated. Alternatively, in order to generate a negative pressure in the storage area 1100 (relative to the pressure in the tank area 1200), the shutoff valve 1400 is closed, the ventilation valve 1610 is closed, and the exhaust valve 1710 is opened, thereby connecting the storage area 1100 to the intake pipe.

[0075] The tank venting system further comprises a pressure acquisition device 1500 having a storage pressure sensor 1510 for detecting the gas pressure in the storage area 1100. The pressure acquisition device 1500 additionally comprises a tank pressure sensor 1520 for detecting the gas pressure in the storage tank area 1200. Figure 1 In the embodiment of , the storage pressure sensor 1510 is arranged in the exhaust line upstream of the exhaust valve 1710 , and the tank pressure sensor 1520 is arranged in the fuel tank 1200 .

[0076] A control device 3000 is provided which is connected to tank venting system 1000 . The control device is designed to detect, store, evaluate, interpret, quantify and qualitatively and quantitatively assess and compare output signals of storage pressure sensor 1510 and output signals of tank pressure sensor 1520 .

[0077] The fuel contained in the fuel tank 1210 tends to release hydrocarbons. In the closed state, the shut-off valve 1400 prevents gaseous hydrocarbons from escaping from the tank area 1200, which leads to a continuous increase in the pressure there. It is necessary to reduce the pressure of the tank area 1200 from time to time. By placing the shut-off valve 1400 in the open state, the gaseous hydrocarbons will flow into the fuel vapor storage 1110 in a controlled manner due to the pressure difference and be stored there temporarily. However, the fuel vapor storage 1110 has a limited capacity and must be regenerated from time to time. For this purpose, the shut-off valve 1400 is closed and the ventilation valve 1610 is opened. By controlling the exhaust valve 1710, the fuel vapor storage 1110 is connected to the intake pipe 1700, whereby a scavenging effect is generated due to the existing pressure difference, wherein the stored hydrocarbons are sucked into the intake pipe 1700 and then supplied to the internal combustion engine 2000, where the hydrocarbons participate in the combustion. The flushing process can be supported by operating pump 1620 , which enables flushing of fuel vapor accumulator 1110 even at very low negative pressures around the intake manifold.

[0078] The law requires that the function of the stop valve 1400 be checked. Figure 2 An embodiment of the method for inspecting the stop valve 1400 is explained in more detail with reference to the flowchart of:

[0079] The method begins with step 100 , for example, when the internal combustion engine is started by the vehicle driver.

[0080] In step 200, pressure detection device 1500 is activated or operated and its output signal is detected. This means that the current output value of storage pressure sensor 1510, which represents the pressure in the storage area, and the current output value of tank pressure sensor 1520, which represents the pressure in the fuel tank, are detected and stored at predetermined time intervals or continuously, for example, by control device 3000. The current output signal is then detected and stored in all subsequent method steps.

[0081] In step 300, the shutoff valve 1400 is controlled in the closed state. In the closed state, pressure equalization and gas flow between the storage area 1100 and the tank area 1200 are prevented. If the shutoff valve 1400 is a valve that is closed without current, the control in the closed state can be achieved, for example, by switching the shutoff valve without current.

[0082] In step 400, the pressure varying device 1800 is operated to change the pressure in the storage area 1100. In one embodiment of the method, the pressure varying device 1800 remains activated during the entire method. To generate an overpressure, the exhaust valve 1710 is closed, the ventilation valve 1610 is opened, and the pump 1620 is operated. To generate a negative pressure, the ventilation valve 1610 is closed or opened and the exhaust valve 1710 is opened, whereby the storage area 1100 is connected to the intake pipe 2000 as a negative pressure source.

[0083] In step 500, the pressure profile of the storage area 1100 in the first time period T0 is determined based on the detected output signal of the pressure detection device 1500, in particular the output value of the storage pressure sensor 1510, and is evaluated as follows: whether the first pressure change in the storage chamber 1100 caused by the operation of the pressure variation device 1800 meets the first plausibility criterion. In this case, the term "first pressure change" not only refers to the numerical change of the pressure at a specific point in time, but also refers to all quantitative and qualitative criteria, numerical values, numerical value sets, numbers, numerical sets, characteristic parameters and characteristic values, by which the change of the pressure in the storage area 1100 can be characterized or quantified or evaluated, such as a pressure gradient, a pressure profile (a sequence of a plurality of pressure values ​​at different points in time), a numerical change of the pressure at a specific point in time, an actual pressure value at a specific point in time relative to a predetermined fixed comparison value, etc.

[0084] For example, if the first pressure gradient in the storage area 1100 acquired based on the output value of the storage pressure sensor 1510 during the operation of the pressure variation device 1800 at least reaches a predetermined first gradient limit value, or the first pressure gradient in the storage area 1100 remains within a predetermined first pressure gradient value range; or if the first pressure curve in the storage area 1100 follows a predetermined first reference curve, or the first pressure curve remains within a predetermined first tolerance range around the first reference curve, then the first plausibility criterion is considered to be met. In this case, the gradient limit value or the pressure gradient value range or the reference curve is preferably predetermined in such a way that the first plausibility criterion is met only if the magnitude of the pressure gradient in the storage area 1100 does not fall below a predetermined threshold value, which is preferably different from zero, during the first time period T0.

[0085] In a variant of the method, during a first time period T0, a fluid mass flow, which can also be referred to as a sweep mass flow, caused by the operation of the pressure variation device 1800 is acquired via a memory area. This acquisition is performed, for example, by means of modeling consisting of measured values, for example measured values ​​of the pressure detection device 1500. In this variant, in order to meet the first plausibility criterion, it is additionally necessary that the time integral of the fluid mass flow within the first time period T0 reaches or exceeds a predetermined minimum value.

[0086] If it is determined in step 500 that the first plausibility criterion is not met, the method is aborted in step 510 , in particular because the current pressure change then does not allow a reliable assessment of the pressure curve, and the method ends in step 800 .

[0087] If it is determined in step 500 that the first plausibility criterion is met, the method continues with step 600, wherein a timer is started and the pressure curve in storage area 1100 and in tank area 1200 is detected by detecting the output signals of storage pressure detection device 1510 and tank pressure detection device 1520 in a second time period T1. In this context, the duration of the second time period is selected by means of a predetermined duration as a function of the output signal of fill level sensor 1213.

[0088] In step 700, the correlation between the pressure profiles detected in the storage area 1100 and in the tank area 1200 in the second time period T1 is evaluated. In addition, a closing fault of the shutoff valve 1400 is detected based on the correlation between the pressure profiles detected in the storage area 1100 and in the tank area 1200 in the second time period T1. In this context, a closing fault of the shutoff valve 1400 is detected if the gradients of the pressure profiles of the pressure in the tank area 1200 and the pressure in the storage area 1100 during the second time period T1 have the same sign and the maximum pressure gradient of the pressure in the tank area 1200 exceeds a predetermined limit value compared to the maximum pressure gradient of the pressure in the storage area 1100 in the second time period T1.

[0089] In one embodiment of the method, if no closing fault is detected, then shut-off valve 1400 is controlled in the open state. Figure 2 This design is not shown in the drawings. For additional features of this design, in addition to the following description, reference is made to the specification, claims and drawings of an earlier international application with application number PCT / EP2022 / 057022, the disclosure of which is hereby incorporated by reference into the present disclosure.

[0090] This step, i.e. the control of the shutoff valve in the open state, can be dependent on whether the pressure in the tank area 1200 differs from the pressure in the storage area 1100 by a predetermined minimum, wherein the shutoff valve 1400 is controlled in the open state only if the test result is positive. In the open state, pressure equalization and gas flow between the storage area 1100 and the tank area 1200 can now be achieved. As mentioned in step 400, the pressure variation device 1800 is further operated with respect to the pressure variation in the storage area.

[0091] In this embodiment, the detected output signal of the pressure detection device 1500 is evaluated in a subsequent step as follows: whether the second pressure change in the storage area 1100 caused by the control of the stop valve 1400 in the open state meets the second plausibility criterion. In this step, it is checked whether the second pressure change in the storage area 1100 is plausible under the assumption that the stop valve 1400 is actually open. Because in the case where the stop valve 1400 is now actually in the open state, a significant second pressure change can be identified compared to the case where the stop valve is stuck in the closed state. Here, the term "second pressure change" not only refers to the numerical change of the pressure at a specific time, but also refers to all quantitative and qualitative criteria, numerical values, numerical value sets, numbers, numerical sets, characteristic parameters and characteristic values, which can be used to characterize or quantify or evaluate the change of the pressure in the storage area, such as pressure gradient, pressure curve (sequence of multiple pressure values ​​at different times), pressure numerical change at a specific time, actual pressure value at a specific time relative to a predetermined fixed comparison value, etc. The output value of the storage pressure sensor is used as the basis for obtaining the "second pressure change".

[0092] Thus, for example, if the change in the pressure gradient in the storage area (1100) reaches at least a predetermined minimum value after the control of the shut-off valve 1400 in the open state, or the second pressure gradient in the storage area (1100) lies within a predetermined second pressure gradient value range, then the second plausibility criterion is considered to be met. In this case, the predetermined minimum value is loaded with data such that, if the change in the second pressure gradient reaches at least the predetermined minimum value, it can be assumed that the shut-off valve 1400 is actually open. Correspondingly, the predetermined second pressure gradient value range is loaded with data such that, if the second pressure gradient lies within the second pressure gradient value range, it can be assumed that the shut-off valve 1400 is opened in accordance with the specification.

[0093] For example, if the pressure in the storage area (1100) changes by at least a predetermined second pressure value after the shut-off valve is activated in the open state, or the pressure in the storage area (1100) is within a predetermined second pressure value range, then the second plausibility criterion is considered to be met. In this case, the predetermined second pressure value is loaded with data such that if the second pressure changes by at least the second pressure value, then the shut-off valve 1400 can be considered to be opened in accordance with the specification. Correspondingly, the predetermined second pressure value range is loaded with data such that if the pressure in the storage area 1100 is within the second pressure value range, then the shut-off valve 1400 can be considered to be opened in accordance with the specification.

[0094] For example, if the second pressure curve in the storage area 1100 follows a predetermined second reference curve after the shut-off valve is controlled in the open state, or the second pressure curve remains within a predetermined second tolerance range around the second reference curve, then the second plausibility criterion is also considered to be met. In this case, the predetermined second reference curve is loaded with data in such a way that, if the second pressure curve follows the second reference curve, it can be assumed that the shut-off valve 1400 is opened in accordance with the specification. Correspondingly, the predetermined second tolerance range is loaded with data in such a way that, if the second pressure curve is within the second tolerance range, it can be assumed that the shut-off valve 1400 is opened in accordance with the specification.

[0095] The load data can be obtained, for example, by laboratory tests or online tests in the vehicle.

[0096] If it is determined that the second plausibility criterion is not met, a fault of the shutoff valve 1400 is detected in a further step and the method is terminated in a subsequent step. Since if the shutoff valve 1400 is functioning properly, it should have assumed its open state by being controlled in the open state, whereby the pressure in the storage area 1100 must have changed to a certain extent, so that the second pressure change criterion will be met. However, if the second pressure change criterion is not met, it can be assumed that the pressure in the storage chamber 1100 has not changed to an adequate degree, which means that the shutoff valve 1400 is stuck in the closed state and can no longer be placed in the open state.

[0097] If it is determined that the second plausibility criterion is met, the method continues with a step in which stop valve 1400 is assessed as being functional and then ends in a further step.

[0098] The method may be repeated regularly and / or in certain operating states of the internal combustion engine.

[0099] The method can be implemented as a computer program product that can be loaded onto a calculator (microcomputer). The computer program product has a software code segment that, when executed on the calculator, performs corresponding calculation operations, releases control instructions, and reads in and processes data. The computer program product can be loaded into the memory of the control device 3000 (controller), such as in Figure 1 As schematically shown. Control device 3000 has all necessary configuration features that are required for storing and executing computer program products, transmitting and receiving data, and controlling the tank venting system. In particular, control device 3000 has a digital memory, a processor, and interfaces for coupling to the components of tank venting system 1000 and internal combustion engine 2000.

Claims

1. A method for checking the functional capability of a controllable shut-off valve (1400) in a tank venting system (1000), the tank venting system having: - a tank farm (1200) having fuel tanks (1210); a storage area (1100) having a fuel vapor storage area (1110); - a venting line (1300) connecting the fuel vapor storage device (1110) and the fuel tank (1210); - the controllable shut-off valve (1400) is arranged in the venting line (1300) and in a closed state prevents pressure equalization between the tank area (1200) and the storage area (1100), and in an open state allows pressure equalization between the tank area (1200) and the storage area (1100), - a pressure variation device (1800) connected to the storage area in order to vary the pressure in the storage area (1100); a pressure detection device (1500) comprising a storage pressure detection device (1510) for detecting the pressure in the storage area (1100) and a tank pressure detection device (1520) for detecting the pressure in the tank area (1200), in, The method comprises the following steps: - detecting a closing target state of the shutoff valve, or controlling the shutoff valve with respect to the closing target state (1400); - activating the pressure detection device (1500); - operating the pressure varying means (1800) in terms of varying the pressure in the storage area (1100), - detecting the pressure trend in the storage area (1100) by detecting the output signal of the storage pressure detection device (1510) in a first time period (T0), and evaluating the detected pressure trend as follows: whether a first pressure change in the storage chamber (1100) caused by the operation of the pressure change device (1800) meets a first credibility criterion; - in particular if the first credibility criterion is met, the pressure trends in the storage area (1100) and in the tank area (1200) are acquired by detecting the output signals of the storage pressure detection device (1510) and the tank pressure detection device (1520) in a second time period (T1); - evaluating a correlation between the pressure trends in the storage area (1100) and in the tank area (1200) acquired during the second time period (T1); - a closing fault of the shut-off valve (1400) is detected based on a correlation between the pressure curves in the storage area (1100) and in the tank area (1200) detected during the second time period (T1).

2. The method according to claim 1, wherein: if: - the gradients of the pressure curves of the pressure in the tank area (1200) and the pressure in the storage area (1100) during the second time period (T1) have the same sign; and - the maximum pressure gradient of the pressure in the tank area (1200) exceeds a predetermined limit value compared to the maximum pressure gradient of the pressure in the storage area (1100) during the second time period (T1); or - the difference between the pressure gradient of the pressure in the tank area (1200) and the pressure gradient of the pressure in the storage area (1100) remains within a predetermined tolerance range during the second time period (T1), A closing failure of the stop valve (1400) is then detected.

3. A method according to any one of the preceding claims, wherein: The tank area (1200) has a fill level sensor (1213), and the method has an additional step in which a signal of the fill level sensor (1213) is detected and the duration of the second time period (T1) is predetermined based on the detected signal of the fill level sensor (1213).

4. The method according to any one of the preceding claims, comprising an additional method step, in which the pressure trend in the storage area (1100) is acquired by detecting an output signal of the storage pressure detection device (1510) within a third time period (T2), and the acquired pressure trend is evaluated as follows: whether a third credibility criterion is met, wherein: If the pressure trend in the storage area acquired during the third time period (T2) is monotonically increasing or monotonically decreasing, the third credibility criterion is met, And wherein the relationship between the pressure trends detected in the storage area (1100) and in the tank area (1200) within the second time period (T1) is evaluated only if the third credibility criterion is met.

5. A method according to any one of the preceding claims, wherein: The starting point of the second time period (T1) is defined by the start of a timer, or the starting points of the second time period (T1) and the third time period (T2) are defined by the start of the timer.

6. A method according to any one of the preceding claims, wherein: During the first time period (T0), a fluid mass flow through the storage area (100) is acquired, in particular caused by the operation of the pressure variation device (1800), and in order to meet the first credibility criterion, it is additionally required that the time integral of the fluid mass flow within the first time period (T0) reaches or exceeds a predetermined minimum value.

7. A method according to any one of the preceding claims, wherein: The method steps are performed repeatedly multiple times.

8. A method according to any one of the preceding claims, wherein: In the case where a closing failure of the stop valve (1400) is not identified, the following steps are performed: - controlling the shut-off valve (1400) in an open state; - evaluating the detected output signal of the pressure detection device (1500) as follows: whether a second pressure change in the storage chamber (1100) caused by controlling the stop valve (1400) in the open state satisfies a second plausibility criterion; If the evaluation shows that the second plausibility criterion is not met, an opening fault of the shut-off valve (1400) is detected.

9. The method according to any of the preceding claims, wherein: if: - after the shut-off valve is controlled in the open state, a change in the pressure gradient in the storage area (1100) and / or in the tank area (1200) at least reaches a predetermined minimum value, or a second pressure gradient in the storage area (1100) and / or in the tank area (1200) is within a predetermined second pressure gradient value range; - after the shut-off valve is controlled in the open state, the pressure in the storage area (1100) and / or in the tank area (1200) changes by at least a predetermined second pressure value, or the pressure in the storage area (1100) and / or in the tank area (1200) is within a predetermined second pressure value range; or - after the shut-off valve has been controlled in the open state, a second pressure trend in the storage area (1100) and / or in the tank area (1200) follows a predetermined second reference trend, or the second pressure trend remains within a predetermined second tolerance range about the second reference trend, The evaluation then indicates that the second credibility criterion is met.

10. A method according to any one of the preceding claims, wherein: The pressure changing device (1800) comprises: - a ventilation line (1600), through which the fuel vapor storage (1110) is connected to the atmosphere; - a controllable ventilation valve (1610), which is arranged in the ventilation line (1600) so as to control the air flow through the ventilation line (1600); - an exhaust gas line (1700), via which the fuel vapor storage device (1110) is connected to a negative pressure source (2100), - a controllable exhaust valve (1710) arranged in the exhaust line (1700) in order to control the air flow through the exhaust line (1700), In order to change the pressure in the storage area (1100), the ventilation valve (1610) is closed and the exhaust valve (1710) is opened, so as to generate a negative pressure in the storage area (1100).

11. The method according to any one of the preceding claims 1 to 9, wherein: The pressure changing device (1800) comprises: - a ventilation line (1600), through which the fuel vapor storage (1110) is connected to the atmosphere; - a controllable ventilation valve (1610), which is arranged in the ventilation line (1600) so as to control the air flow through the ventilation line (1600); - an exhaust gas line (1700), via which the fuel vapor storage device (1110) is connected to a negative pressure source (2100), - a controllable exhaust valve (1710) arranged in the exhaust line (1700) in order to control the air flow through the exhaust line (1700), In order to change the pressure in the storage area (1100), the ventilation valve (1610) and the exhaust valve (1710) are opened to generate negative pressure in the storage area (1100).

12. The method according to any one of the preceding claims 1 to 9, wherein: The pressure changing device (1800) comprises: - a ventilation line (1600), through which the fuel vapor storage (1110) is connected to the atmosphere; - a controllable ventilation valve (1610), which is arranged in the ventilation line (1600) so as to control the air flow through the ventilation line (1600); a controllable pump (1620) arranged in the ventilation line (1600) downstream of the ventilation valve (1610) in order to pump ambient air from the atmosphere into the fuel vapor storage area (1110) in order to generate an overpressure in the storage area (1100); - an exhaust gas line (1700), via which the fuel vapor storage device (1110) is connected to a negative pressure source (2100), - a controllable exhaust valve (1710) arranged in the exhaust line (1700) in order to control the air flow through the exhaust line (1700), In order to change the pressure in the storage area (1100), the ventilation valve (1610) is opened, the exhaust valve (1710) is closed, and the pump (1620) is operated to generate an overpressure in the storage area (1100).

13. A method according to any one of the preceding claims, wherein: The reservoir pressure detection device (1510) behaves as a virtual sensor, and an output signal of the reservoir pressure detection device (1510) is modeled based on the pressure measured or calculated downstream of the exhaust valve (1710).

14. A computer program product which can be loaded into a memory of a computer and which has software code sections according to which the method according to one of the preceding claims is carried out when the computer program product is run on the computer.

15. A control device (3000) for controlling a tank venting system (1000), the control device having a computer and a memory, on which a computer program product according to the preceding claim is loaded.

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