Method and system for fault diagnosis of a dual flushing system

Abstract

Procedure for diagnosing a fault in a dual flushing system, comprising: Detect, by means of a control (CLR), a pressure in a fuel tank (10) in which vapor gas is collected, measured by a fuel tank pressure sensor (11) when a turbocharger (90) is operated for boosting and a purge valve (30) is actuated; Diagnosing, by the control unit (CLR), a current situation as a fault situation in which an engine vacuum generating line (40) connected between the purge valve (30) and a front end of an expansion tank (50) remains open when a pressure change value calculated on the basis of the fuel tank pressure (10) exceeds a reference value; Output, by the control system (CLR), of a warning regarding an error situation when an error is detected; and Diagnosing, by the control (CLR), the current situation as a fault situation in which a forced vacuum generating line (70) remains closed when the pressure change value calculated on the basis of the pressure difference of the fuel tank (10) is within a reference range that is smaller than the reference value, wherein a return flow line (80) is connected between a front end of the turbocharger (90) and a front end of a throttle valve (60) and the forced vacuum generating line (70) is connected between the purge valve (30) and a section connected to the front end of the turbocharger (90) and the return flow line (80) to collect the vaporizing gas in a container (20) which is operated to be selectively purged into one of the two lines, and where the current situation is diagnosed as a fault situation in which an ejector (81) connected between the forced vacuum generation line (70), the return flow line (80) and the turbocharger (90) remains closed.

Description

Background 1. Field of invention

[0001] The present disclosure relates to a method and a system for diagnosing a fault in a dual purging system, in particular a method and a system that diagnose a fault situation of a vacuum generating line using a fuel tank pressure sensor that detects the pressure of a fuel tank. 2. Description of the state of the art

[0002] Vaporizing gas (oil vapor) is produced when fuel in a fuel tank evaporates due to external heat or during refueling. A method is used to collect this vaporizing gas using a container, whereby the collected vaporizing gas is mixed with air in an intake pipe via a purging system and then combusted in a combustion chamber.

[0003] Nowadays, an engine with multi-point injection (MPI) is used to meet emissions regulations regarding evaporative emissions through a single scavenging system. However, a single scavenging system cannot be used for a turbocharged engine with gasoline direct injection (GDI) because overpressure is created in the intake manifold during turbo operation. In other words, when a turbocharger is operating, compressed air flows into the intake manifold, creating overpressure, which can make it difficult to achieve the scavenging function with existing single-scavenging systems.

[0004] Accordingly, recent efforts have focused on meeting regulations and achieving commercial value through the use of a dual scavenging system in a turbocharged GDI engine. This involves employing a device that, when the turbocharger is operating, creates a vacuum. This vacuum allows the vaporized gas, which escapes from a reservoir during engine vacuum generation, to be scavenged in an expansion tank and then, when the turbocharger is operating, forced into a combustion chamber by means of a vacuum generator.

[0005] Furthermore, such a vacuum generator includes a pressure sensor, which is separate from a fuel tank pressure sensor on the fuel tank, to diagnose a fault in the vacuum generator based on a pressure value measured by the pressure sensor. However, the pressure sensor is installed specifically for diagnosing a fault in the vacuum generator, thus incurring additional installation costs. Therefore, there is a need to diagnose a fault in the vacuum generator without requiring the pressure sensor.

[0006] Furthermore, a flushing system is known from KR 10 2018 0 022 369 A in which a return flow line is connected between a front end of a turbocharger and a front end of a throttle valve and a forced vacuum generating line is connected between the flushing valve and a section connected to the front end of the turbocharger and the return flow line in order to collect the vaporizing gas in a container which is operated to be selectively flushed into one of the two lines.

[0007] DE 43 28 090 A1 discloses a method for diagnosing a fault in a dual purge system, comprising: detecting, by a control ECU, a pressure in a fuel tank in which vapor gas is collected, measured by a fuel tank pressure sensor, when a turbocharger is operated for boosting and a purge valve is actuated; diagnosing, by the control unit, a current situation as a fault situation in which an engine vacuum generating line, connected between the purge valve and a front end of an expansion tank, remains open when a pressure change value, calculated on the basis of the fuel tank pressure, exceeds a reference value; and outputting, by the control unit, a warning regarding a fault situation when a fault is detected.

[0008] Furthermore, DE 10 2012 206 810 A1 discloses systems and methods for diagnosing a valve leak in a vehicle that stores gaseous fuel in two or more tanks. A valve regulating the flow of gaseous fuel from one of the tanks is closed and reopened during a complete operating cycle while the other tanks supply gaseous fuel. A pressure spike caused by the valve reopening is analyzed to determine the rate of pressure change. Pressure spikes with a rate of change less than a threshold parameter indicate a leaking valve.

[0009] The above description of the prior art of the present disclosure serves only to provide background information on the present disclosure and should not be interpreted as belonging to the prior art known to the person skilled in the art. overview

[0010] It is therefore the purpose of the present disclosure to provide a method and a system for diagnosing a fault in a dual purging system, wherein the method and the system are able to diagnose a fault situation in a vacuum generating line using a fuel tank pressure sensor that measures the pressure of a fuel tank.

[0011] The problem is solved by a method for diagnosing a fault in a dual flushing system with the features of claims 1 or 5, and by a system for diagnosing a fault in a dual flushing system with the features of claim 6. Advantageous further developments are found in the dependent claims.

[0012] In light of the above aspect, a method is provided for diagnosing a fault in a dual scavenging system, wherein an engine vacuum generating line is connected between a scavenging valve and the front end of an expansion tank, a return flow line is connected between the front end of a turbocharger and the front end of a throttle valve, and a forced vacuum generating line is connected between the scavenging valve and a part connected to the front end of the turbocharger, the return flow line being used to collect evaporating gas from the fuel tank in a container operated in such a way as to be selectively scavenged in one of the two lines. This method may include: detecting a pressure in a fuel tank where evaporating gas is collected, measured by a fuel tank pressure sensor.when a turbocharger is operating for boost and the purge valve is actuated; diagnosing a current situation as a fault situation in which the engine vacuum generating line, connected between the purge valve and the front end of an expansion tank, remains open when a pressure change value calculated based on the fuel tank pressure exceeds a reference value; issuing a warning regarding a fault situation when a fault is detected; and diagnosing, by the control unit, the current situation as a fault situation in which a forced vacuum generating line remains closed when the pressure change value calculated based on the fuel tank pressure differential is within a reference range.which is smaller than the reference value. A return flow line is connected between the front end of a turbocharger and the front end of a throttle valve, and the forced vacuum generating line is connected between the scavenge valve and a section connected to the front end of the turbocharger and the return flow line to collect the vaporizing gas in a container that is operated to be selectively purged into one of the two lines. The current situation is diagnosed as a fault condition in which an ejector connected between the forced vacuum generating line, the return flow line, and the turbocharger remains closed.

[0013] During the initial fault diagnosis, the current situation can be diagnosed as a fault in which a first check valve in the engine vacuum generation line remains open. The pressure change value can be calculated as the derivative per unit time of the difference between the fuel tank pressure measured during purging and the fuel tank pressure measured before purging, where the reference value can be determined based on the turbocharger boost pressure, which can be a tabulated value to exhibit a rising characteristic of a linear function.

[0014] In this second fault diagnosis, the current situation can be diagnosed as a fault situation in which a second check valve in the forced vacuum generation line remains closed.

[0015] According to a further aspect of the present disclosure, a method for diagnosing a fault in a dual scavenging system is provided, wherein an engine vacuum generating line is connected between a scavenging valve and a front end of an expansion tank, a return flow line is connected between a front end of a turbocharger and a front end of a throttle valve, and a forced vacuum generating line is connected between the scavenging valve and a part connected to the front end of the turbocharger, the return flow line for collecting evaporating gas from the fuel tank in a container operated such that it is selectively scavenged in one of the two lines may include: sensing a pressure in a fuel tank in which evaporating gas is collected, measured by a fuel tank pressure sensor.when a turbocharger is operating for boost and the purge valve is actuated; diagnosing a current situation as a fault situation in which the engine vacuum generating line, connected between the purge valve and the front end of an expansion tank, remains open when a pressure change value calculated based on the fuel tank pressure exceeds a reference value; issuing a warning regarding a fault situation when a fault is detected; and diagnosing, by the control unit, the current situation as a fault situation in which a forced vacuum generating line remains closed when the pressure change value calculated based on the fuel tank pressure differential is within a reference range.which is smaller than the reference value. A return flow line is connected between the front end of a turbocharger and the front end of a throttle valve, and the forced vacuum generating line is connected between the purge valve and a section connected to the front end of the turbocharger and the return flow line to collect the vaporizing gas in a container that is operated to be selectively purged into one of the two lines. The pressure change value is calculated as the derivative per unit time of the difference between the fuel tank pressure measured during purging and the fuel tank pressure measured before purging, and the reference range is determined based on a fuel level in the fuel tank, which is a predetermined range including 0.

[0016] Considering the above aspect, a system for diagnosing a fault in a dual scavenging system, in which an engine vacuum generating line is connected between a scavenging valve and the front end of an expansion tank, a return flow line is connected between the front end of a turbocharger and the front end of a throttle valve, and a forced vacuum generating line is connected between the scavenging valve and a part connected to the front end of the turbocharger, and the return flow line is operated to collect the fuel tank evaporation gas in a container for selective scavenging in one of the two lines, may include: an input unit into which the pressure in a fuel tank, measured by a fuel tank pressure sensor, is input while the turbocharger is performing a boost and the scavenging valve is actuated;a calculation unit configured to calculate a pressure change value based on the pressure differential of the fuel tank; a detection unit configured to diagnose a current situation as a fault situation in which the engine vacuum generation line remains open if the pressure change value calculated by the calculation unit exceeds a reference value; an output unit configured to issue a fault situation warning when the detection unit diagnoses the current situation as a fault situation;and an adjustment unit configured to determine a reference value based on the turbocharger boost pressure and to determine the reference range based on a fuel level in the fuel tank, wherein the determination unit is configured to diagnose the current situation as a fault situation in which the forced vacuum generating line remains closed when the pressure change value within a reference range is less than the reference value.

[0017] The calculation unit can be designed such that the pressure change value is calculated as the derivative per unit of time of the difference between the pressure of the fuel tank measured during purging and the pressure of the fuel tank measured before purging.

[0018] According to the present disclosure, it may be possible to diagnose a fault in a vacuum generation line during the operation of the turbocharger by means of the pressure change value measured by the pressure sensor of the fuel tank, whereby it may be possible to remove an additional pressure sensor of the corresponding type mounted in a vacuum generation line and thus reduce the manufacturing costs of a vehicle. Brief description of the drawings

[0019] The above-mentioned and further aspects, features and advantages of the present disclosure will be better understood from the following detailed description in conjunction with the accompanying drawings, wherein: Fig. 1 a diagram showing the entire configuration of a dual flushing system for a motor vehicle according to the present disclosure; Fig. 2 a diagram showing the configuration of a system for diagnosing a fault in a dual flushing system according to the present disclosure; Fig. 3 is a diagram showing the sequence of a fault diagnosis process for a dual flushing system according to the present disclosure; and Fig. Figure 4 is a diagram illustrating a pressure change in a fuel tank that occurs when a first and second check valve are in a braking or normal situation. Detailed description

[0020] The term "vehicle" or "belonging to a vehicle" or any other similar term as used herein is understood to include motor vehicles in general, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft and the like, and also includes hybrid vehicles, electric vehicles, internal combustion engine vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum).

[0021] Although an exemplary embodiment is described that uses a plurality of units to carry out the exemplary process, it is assumed that the exemplary processes can also be carried out by one or more modules. Furthermore, it is assumed that the term controller / control unit refers to a hardware unit comprising a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules in order to carry out one or more processes, which are described below.

[0022] The terminology used herein serves only to describe certain embodiments and is not intended to limit the disclosure. As used herein, the singular forms "one" and "the" are to include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms "includes" and / or "comprehensive," when used in this description, indicate the presence of specified features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes each and every combination of one or more of the related listed elements.

[0023] Unless explicitly stated or evident from the context as used here, the term "approximately" is understood to mean within a tolerance range customary in the prior art, for example, within two standard deviations of the mean. The term "approximately" may be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise indicated by the context, all numerical values ​​stated herein are modified by the term "approximately".

[0024] Furthermore, the control logic of the present disclosure can be embodied as a non-temporary, computer-readable medium on a computer-readable storage medium comprising executable program instructions that are executed by a processor, controller, or similar device. Examples of computer-readable storage media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable recording medium can also be distributed across networked computer systems, allowing the computer-readable media to be stored and executed in a distributed manner, for example, via a telematics server or a controller area network (CAN).

[0025] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. Fig. Figure 1 is a diagram showing a dual flushing system for a motor vehicle to which the present disclosure can be applied, wherein a fuel tank pressure sensor 11 can be configured to measure the pressure in a fuel tank 10.

[0026] Furthermore, a container 20 can be provided for collecting vapor gas escaping from the fuel tank 10, which can be connected to a purge valve 30 for discharging the vapor gas collected in the container 20. An engine vacuum generation line 40 can be connected between the purge valve 30 and the front end of an expansion tank 50, so that when a vacuum is generated in the engine, the vapor gas flowing from the purge valve 30 can flow through the engine vacuum generation line 40 into the expansion tank 50, thereby purging the vapor gas.

[0027] Additionally, an ejector (expulsion device) 81 can be arranged at the front end of a turbocharger 90, wherein a return flow line 80 can be connected between the ejector 81 and the front end of a throttle valve 60, and a forced vacuum generation line 70 can be connected between the purge valve 30 and the ejector 81, which is connected to the front end of the turbocharger 90 and the return flow line 80, so that when overpressure is generated in the engine, the vaporizing gas flowing from the purge valve 30 can flow through the forced vacuum generation line 70 into the expansion tank 50, thereby purging the vaporizing gas. A first check valve 41 and a second check valve 71 can each be arranged in the engine vacuum line 40 and the forced vacuum line 70 to prevent backflow of vaporizing gas.

[0028] In other words, when a vacuum is created in the engine, the vaporizing gas can be expelled from the reservoir 20 and, due to the suction force generated by the engine vacuum, flow to the purge valve 30. The purge valve 30 can be actuated upon a signal from the CLR control unit, allowing the vaporizing gas to flow through the engine vacuum generation line 40 into the expansion tank 50, thus purging the vaporizing gas.

[0029] However, when overpressure is generated in the engine by the operation of the turbocharger 90, air can circulate through the return flow line 80 and the ejector 81, thereby creating a vacuum in the forced vacuum generation line 70. Accordingly, when the purge valve 30 is actuated upon a signal from the CLR control unit, the vaporizing gas can flow through the forced vacuum generation line 70 into the expansion tank 50, thus purging the vaporizing gas. Additionally, a fault in the engine vacuum generation line 40 and the forced vacuum generation line 70 due to a pressure change in the fuel tank 10 can be diagnosed during the diagnostics of the dual purge system of this disclosure.

[0030] With reference to the Fig. 2 and Fig. 3. A procedure for diagnosing a fault in a dual purge system may include the following: detection, by a control CLR, of a pressure in the fuel tank 10, measured by the fuel tank pressure sensor 11, when the turbocharger 90 is operating for boosting and the purge valve 30 is operating; determination, by the control CLR, of the current situation as a fault situation (e.g., detection of a malfunction) in which the engine vacuum generating line 40 remains open when a pressure change value calculated from a pressure differential in the fuel tank 10 exceeds a reference value (e.g., an initial diagnosis); and output, by the control, of a warning of a fault situation in response to the detection of a malfunction.

[0031] The control system can be implemented, according to exemplary embodiments of the present disclosure, by a non-volatile memory (not shown) configured to store algorithms for executing the operation of various components of a vehicle or data about software instructions for executing the algorithms, and a processor (not shown) configured to perform the operation described below using the data stored in the memory. The memory and the processor can be separate chips. Alternatively, the memory and the processor can be integrated into a single chip. The processor can be implemented as one or more processors.

[0032] Furthermore, in the first fault diagnosis process, the current situation can be diagnosed as a fault in which the first check valve 41 in the engine vacuum generation line 40 remains open. This means that when the purge valve 30 is actuated by the turbocharger 90 during charging, vaporizing gas flows into the forced vacuum generation line 70, and therefore the engine vacuum generation line 40 should be closed.

[0033] However, if the engine vacuum generation line 40 is not closed and remains open due to a fault (e.g., failure, malfunction, error) of the first check valve 41, etc., the excess air supplied by the turbocharger 90 can flow into the combustion chamber and back into the engine vacuum generation line 40, thereby increasing the pressure in the fuel tank 10. If the first check valve 41, as in Fig. As shown in Figure 4, if the check valve remains open, the pressure change value of the fuel tank 10 rises above the reference value, so that the current situation can be recognized as a fault situation of the first check valve and a warning about the fault situation can be issued to the driver. In other words, the warning can be issued and displayed on a display instrument in the vehicle.

[0034] Furthermore, the pressure change value (or pressure change rate) of fuel tank 10 can be calculated as the derivative per unit time of the difference between the pressure of fuel tank 10 measured during purging and the pressure of fuel tank 10 measured before purging. In other words, the pressure of fuel tank 10 measured during purging is the currently measured pressure value of fuel tank 10, and the pressure of fuel tank 10 measured before purging is an initial pressure value, which can be expressed by the following formula: Fuel tank pressure change value = (current fuel tank pressure value - initial pressure value) / unit time

[0035] The reference value, which is compared with the pressure change value of the fuel tank 10, is a value that can be determined from the boost pressure of the turbocharger 90, which can be a tabulated value to exhibit an increasing slope property of a linear function.

[0036] The procedure may further include diagnosing the current situation as a fault situation in which the forced vacuum generation line 70 remains closed when the pressure change value calculated on the basis of the pressure difference of the fuel tank 10 is contained in a reference range below the reference value (e.g. a second diagnosis).

[0037] In the second fault diagnosis, the current situation can be diagnosed as a fault in which the second check valve 71 in the forced vacuum generation line 70 remains closed, or as a fault in which the ejector 81 connected between the forced vacuum generation line 70, the return flow line 80, and the turbocharger 90 remains closed. This means that if the purge valve 30 is actuated during charging by the turbocharger 90, vaporizing gas can flow into the forced vacuum generation line 70, so the forced vacuum generation line 70 should be open.

[0038] However, if the forced vacuum generation line 70 is not open and remains closed due to a fault in the second check valve 71 or in the ejector 81, no vacuum is generated in the forced vacuum generation line 70, so the vaporizing gas in the container 20 cannot be drawn in and the pressure of the fuel tank 10 does not change. Therefore, if the second check valve 71 or the ejector 81, as in Fig. As shown in Figure 4, if the second check valve 71 remains closed, the pressure change value in the fuel tank 10 is within the reference range including 0, and thus the current situation can be recognized as a fault situation of the second check valve 71 or the ejector 81 and a warning can be issued to a driver regarding the fault situation.

[0039] If the second check valve 71 or the ejector 81 is in a normal state, a vacuum is generated in the forced vacuum generation line 70, so that the pressure change value of the fuel tank 10 can be expressed as a negative value. Specifically, the pressure change value of the fuel tank 10 can be calculated as the derivative per unit time of the difference between the pressure of the fuel tank 10 measured during purging and the pressure of the fuel tank 10 measured before purging. In other words, the pressure of the fuel tank 10 measured during purging is the currently measured pressure value of the fuel tank 10, and the pressure of the fuel tank 10 measured before purging is an initial pressure value, which can be expressed by the following formula: Fuel tank pressure change value = (current fuel tank pressure value - initial pressure value) / unit time

[0040] The reference range, which is compared with the pressure change value of the fuel tank 10, can be determined based on the fuel level in the fuel tank 10, which can be a tabulated value including 0.

[0041] Furthermore, Fig. 2 A diagram showing the configuration of a system for diagnosing a fault in a dual flushing system according to the present disclosure, which may include an input unit 100, a computation unit 110, a determination unit 120, and an output unit 130, which may be components of the CLR controller. In other words, the units can be operated by the controller.

[0042] According to Fig. 2. The pressure in fuel tank 10, measured by the fuel tank pressure sensor 11 while the turbocharger 90 is performing boost and the purge valve 30 is operating, can be input into the input unit 100. The calculation unit 110 can be configured to calculate a pressure change value based on the pressure difference in fuel tank 10. The pressure change value can be calculated, for example, as the derivative per unit time of the difference between the pressure in fuel tank 10 measured during purging and the pressure in fuel tank 10 measured before purging.

[0043] Furthermore, the determination unit 120 can be configured to diagnose or detect the current situation as a fault situation, whereby the vacuum generation line 40 of the motor remains open if the pressure change value calculated by the calculation unit 110 exceeds a reference value. The determination unit 120 can also be configured to diagnose or detect the current situation as a fault situation, whereby the forced vacuum generation line 70 remains closed if the pressure change value is within a reference range that is smaller than the reference value. If the determination unit 120 diagnoses the current situation as a fault situation, the output unit 130 can be configured to issue a warning of the fault situation.

[0044] The system may further include an adjustment unit 140 configured to determine a reference value based on the boost pressure of the turbocharger 90 and to establish a reference range based on a fuel level in the fuel tank 10. Fault diagnosis by the dual purging system according to the present disclosure is described below with reference to the Fig. 2 and Fig. 3 described. First, the pressure in the fuel tank 10 can be measured and stored by the fuel tank pressure sensor 11 before the purge valve 30 is actuated (S10).

[0045] When turbocharger 90 begins charging (S20), it can be determined whether the purge valve 30 is actuated during turbocharger 90 charging (S30). If purge valve 30 is actuated and one second elapses, the pressure of fuel tank 10 at that time can be measured and stored (S40). The pressure change value of fuel tank 10 can be calculated based on the difference value for A seconds between the initial pressure of fuel tank 10 measured in step S10 and the current pressure measured in step S40 (S50).

[0046] Furthermore, a reference value and a reference range corresponding to the pressure change value can be set based on factors such as the turbocharger boost pressure 90, the fuel level, the coolant temperature, and the atmospheric pressure. It can also be determined whether the pressure change value exceeds the reference value (S60). If the pressure change value is exceeded, the current situation can be diagnosed as a fault situation in which the first check valve 41 remains open (S70), and the driver can be warned of the fault situation by a display instrument (S80).

[0047] If the pressure change value is not exceeded, the first check valve 41 can be diagnosed as being in a normal state (S90). Furthermore, regardless of whether the pressure change value is determined within the reference range (S100), and if the pressure change value is within the reference range, the current situation can be diagnosed as a fault situation in which the second check valve 71 or the ejector 81 remains closed (S110), with the driver being warned of the fault situation by a display instrument (S120). However, if the pressure change value is outside the reference range, the second check valve 71 and the ejector 81 can be diagnosed as being in a normal state (e.g., without failure) (S130).

[0048] As described above, the present disclosure can diagnose the current situation as a fault in the first check valve 41 if the pressure change value in the fuel tank 10 is greater than the reference value, and can diagnose the current situation as a fault in the second check valve 71 or the ejector 81 if the pressure change value in the fuel tank 10 is within the reference range. Accordingly, the diagnosis of a fault in a vacuum generation line during the operation of the turbocharger 90 can be made using the tank pressure sensor 11 designed to measure the pressure in the fuel tank 10, whereby an additional pressure sensor installed in a vacuum generation line can be omitted in the appropriate manner, thereby also reducing the manufacturing costs of a vehicle.

Claims

[1] Method for diagnosing a fault in a dual flushing system, comprising: Detect, by means of a control (CLR), a pressure in a fuel tank (10) in which vapor gas is collected, measured by a fuel tank pressure sensor (11) when a turbocharger (90) is operated for boosting and a purge valve (30) is actuated; Diagnosing, by the control unit (CLR), a current situation as a fault situation in which an engine vacuum generating line (40) connected between the purge valve (30) and a front end of an expansion tank (50) remains open when a pressure change value calculated on the basis of the fuel tank pressure (10) exceeds a reference value; Output, by the control system (CLR), of a warning regarding an error situation when an error is detected; and Diagnosing, by the control (CLR), the current situation as a fault situation in which a forced vacuum generating line (70) remains closed when the pressure change value calculated on the basis of the pressure difference of the fuel tank (10) is within a reference range that is smaller than the reference value, wherein a return flow line (80) is connected between a front end of the turbocharger (90) and a front end of a throttle valve (60) and the forced vacuum generating line (70) is connected between the purge valve (30) and a section connected to the front end of the turbocharger (90) and the return flow line (80) to collect the vaporizing gas in a container (20) which is operated to be selectively purged into one of the two lines, and where the current situation is diagnosed as a fault situation in which an ejector (81) connected between the forced vacuum generation line (70), the return flow line (80) and the turbocharger (90) remains closed. [2] Method according to claim 1, wherein the current situation is diagnosed as a fault situation in which a first check valve (41) in the engine vacuum generation line (40) remains open. [3] Method according to claim 1, wherein the pressure change value is calculated as the derivative per unit time of the difference between the pressure of the fuel tank (10) measured during purging and the pressure of the fuel tank (10) measured before purging, wherein the reference value is determined on the basis of the boost pressure of the turbocharger (90), which is a tabulated value to exhibit an increasing slope property of a linear function. [4] Method according to claim 1, wherein the current situation is diagnosed as a fault situation in which a second check valve (71) in the forced vacuum generation line (70) remains closed. [5] Method for diagnosing a fault in a dual flushing system, comprising: Detect, by means of a control (CLR), a pressure in a fuel tank (10) in which vapor gas is collected, measured by a fuel tank pressure sensor (11) when a turbocharger (90) is operated for boosting and a purge valve (30) is actuated; Diagnosing, by the control unit (CLR), a current situation as a fault situation in which an engine vacuum generating line (40) connected between the purge valve (30) and a front end of an expansion tank (50) remains open when a pressure change value calculated on the basis of the fuel tank pressure (10) exceeds a reference value; Output, by the control system (CLR), of a warning regarding an error situation when an error is detected; and Diagnosing, by the control (CLR), the current situation as a fault situation in which a forced vacuum generating line (70) remains closed when the pressure change value calculated on the basis of the pressure difference of the fuel tank (10) is within a reference range that is smaller than the reference value, wherein a return flow line (80) is connected between a front end of a turbocharger (90) and a front end of a throttle valve (60) and the forced vacuum generating line (70) is connected between the purge valve (30) and a section connected to the front end of the turbocharger (90) and the return flow line (80) to collect the vaporizing gas in a container (20) which is operated to be selectively purged into one of the two lines, and wherein the pressure change value is calculated as a derivative per unit time of the difference between the pressure of the fuel tank (10) measured during purging and the pressure of the fuel tank (10) measured before purging, wherein the reference range is determined on the basis of a fuel level in the fuel tank (10) which is a predetermined range including 0. [6] System for diagnosing a fault in a dual purging system, wherein an engine vacuum generating line (40) is connected between a purge valve (30) and a front end of an expansion tank (50), wherein a return flow line (80) is connected between a front end of a turbocharger (90) and a front end of a throttle valve (60), and a forced vacuum generating line (70) is connected between the purge valve (30) and a section connected to the front end of the turbocharger (90) and the return flow line (80) such that the evaporating gas from the fuel tank (10) collected in a container (20) is controlled to be selectively purged into one of the two lines, wherein the system comprises: an input unit into which the pressure in a fuel tank (10) is entered, which is measured by a pressure sensor (11) of the fuel tank (10) while the turbocharger (90) is performing a charging operation and the purge valve (30) is actuated; a calculation unit trained to calculate a pressure change value based on the pressure of the fuel tank (10); a determination unit that is trained to diagnose a current situation as a fault situation in which the engine vacuum generating line (40) remains open when the pressure change value calculated by the calculation unit exceeds a reference value; an output unit that is trained to issue a warning regarding an error situation when the destination unit diagnoses the current situation as an error situation; and an adjustment unit designed to determine a reference value based on the boost pressure of the turbocharger (90) and to determine the reference range based on a fuel level in the fuel tank (10), wherein the determination unit is designed to diagnose the current situation as a fault situation in which the forced vacuum generation line (70) remains closed when the pressure change value within a reference range is less than the reference value. [7] System according to claim 6, wherein the calculation unit is configured to calculate the pressure change value as a derivative per unit time of the difference between the pressure of the fuel tank (10) measured during purging and the pressure of the fuel tank (10) measured before purging.

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