Method for monitoring the leakage of an exhaust gas recirculation system for an engine

Abstract

A method for monitoring the leakage of an exhaust gas recirculation (EGR) system for an engine of a vehicle, comprising the steps of: Determining by a control device (100) whether the engine (40) is in an idle state in which the EGR system is not operated (S200); Determining by the control device (100) whether a leakage of the EGR system occurs based on an expected pressure of gas sucked into an intake manifold (10) connected to the engine (40) and a measured pressure of gas sucked into the intake manifold (10) when the engine (40) is in the idle state (S205); Determining by the control device (100) that a leakage of the EGR system occurs when the measured pressure is greater than the expected pressure (S260, S290), and if it is determined that a leakage of the EGR system is occurring, ultimately determining by the control device (100) that a leakage of the EGR system is occurring based on a measured pressure of gas sucked into the intake manifold (10) corresponding to an opening angle of an exhaust gas recirculation (EGR) valve (20), a measured pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle, an expected pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20), and an expected pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated in the opening angle in a state in which the fuel supply to the engine (40) is switched off (S295), wherein a first measured pressure, which is calculated based on the measured pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20) and the measured pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle, is greater than a first expected pressure, which is calculated based on the expected pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20) and the expected pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle.

Description

[0001] The invention relates to a vehicle, and in particular to a method for monitoring the leakage of an exhaust gas recirculation system for an engine (e.g. an internal combustion engine) of a vehicle.

[0002] A diesel vehicle generally includes an exhaust gas recirculation (EGR) device for reducing nitrogen oxides (NOx) among the exhaust gases produced by driving a vehicle engine.

[0003] Generally, the EGR device is mounted in a middle position of a pipe connecting an EGR valve to an exhaust manifold and an intake manifold, and the EGR amount is determined by an opening degree of the EGR valve.

[0004] When a leak occurs in the EGR device, exhaust emissions increase, engine idling instability occurs, and overall vehicle performance deteriorates. Therefore, EGR device leakage diagnosis is required.

[0005] Generally, engine exhaust contains a large amount of harmful components, such as CO, HC, and nitrogen compounds (NOx). As the engine combustion temperature increases, the amount of NOx increases. Therefore, to reduce the amount of NOx in the exhaust, it is necessary to reduce the engine combustion temperature.

[0006] Instantaneous high-temperature heat can be generated by increasing a propagation speed of a flame ignited in a spark plug in a state where the density of the fuel-air mixture in a combustion chamber of the engine is high, thereby increasing the combustion temperature of the engine.

[0007] An exhaust gas recirculation (EGR) system can introduce a portion of the exhaust gas into the combustion chamber by incorporating that portion of the exhaust gas into the fuel-air mixture, thereby reducing the density of the fuel-air mixture without changing the air-fuel ratio. Therefore, the exhaust gas recirculation system can reduce the engine's combustion temperature to reduce the amount of NOx in the exhaust gas.

[0008] The exhaust gas recirculation process is used not only to reduce the amount of NOx in the exhaust gas, but also to improve engine fuel economy. By using the exhaust gas recirculation process, the combustion chamber temperature can be lowered to reduce the amount of NOx, and at the same time, the engine's ignition timing can be advanced to prevent knocking. Therefore, engine performance can be improved, and the vehicle's fuel economy can be improved.

[0009] DE 10 2016 006 715 A1 describes a method for monitoring the leakage of an exhaust gas recirculation (EGR) system for an engine of a vehicle, comprising the steps of: determining by a control device whether the engine is in an idle state in which the EGR system is not operated, determining by the control device whether a leakage of the EGR system occurs based on an expected pressure of gas sucked into an intake manifold connected to the engine and a measured pressure of gas sucked into the intake manifold when the engine is in the idle state, determining by the control device that a leakage of the EGR system occurs if the measured pressure is greater than the expected pressure.

[0010] Another method for monitoring the leakage of an EGR system for a vehicle engine is known from KR 10 2012 0 119 339 A.

[0011] The invention provides a method for monitoring the leakage of an exhaust gas recirculation system for an engine of a vehicle, which method is suitable for diagnosing or detecting a small amount of flow leakage of the exhaust gas recirculation system for the engine.

[0012] This is achieved according to the invention by a method for monitoring the leakage of an EGR system for a vehicle engine according to the features of claim 1. Advantageous further developments are described in the subclaims.

[0013] An exemplary embodiment of the invention provides a method for monitoring the leakage of an exhaust gas recirculation (EGR) system for an engine of a vehicle, comprising: determining (or determining or calculating) by a controller whether the engine is in an idle state in which the EGR system is not operating, determining (or determining or calculating) by the controller whether a leakage of the EGR system is occurring based on an expected (or predicted or predicted) pressure of gas drawn into an intake manifold connected to the engine and a measured pressure of gas drawn into the intake manifold when the engine is in the idle state, and determining (or determining or calculating) by the controller that a leakage of the EGR system is occurring when the measured pressure is greater than the expected pressure.

[0014] The method for monitoring EGR system leakage for the engine further comprises: when it is determined that leakage is occurring, ultimately determining, by the controller, that EGR system leakage is occurring based on a measured pressure of a gas sucked into the intake manifold corresponding to an opening angle of an exhaust gas recirculation (EGR) valve (or an exhaust gas recirculation (EGR) system valve), a measured pressure of a gas sucked into the intake manifold corresponding to a closing of the EGR valve after the EGR valve is operated at the opening angle, an expected (ora predicted or pre-calculated) pressure of the gas sucked into the intake manifold according to the opening angle of the EGR valve, and an expected pressure of the gas sucked into the intake manifold according to closing of the EGR valve after the EGR valve has been operated at the opening angle in a state in which the fuel supply to the engine is cut off. A first measured pressure, which is calculated (or determined) using the measured pressure of the gas sucked into the intake manifold according to the opening angle of the EGR valve and the measured pressure of the gas sucked into the intake manifold according to closing of the EGR valve after the EGR valve has been operated at the opening angle.determined) is greater than a first expected pressure which is calculated (or determined) by means of the expected pressure of the gas sucked into the intake manifold according to the opening angle of the EGR valve and the expected pressure of the gas sucked into the intake manifold according to a closing of the EGR valve after the EGR valve has been operated at the opening angle.

[0015] The controller can determine the expected pressure of the gas based on a speed (or number of revolutions) of the engine.

[0016] The final determination that a leakage of the EGR system occurs may include: first determining (or calculating) by the controller that a leakage of the EGR system occurs based on a measured pressure of a gas sucked into the intake manifold corresponding to a first opening angle of the EGR valve, a measured pressure of a gas sucked into the intake manifold corresponding to a closing of the EGR valve after the EGR valve has been operated at the first opening angle, an expected pressure of the gas sucked into the intake manifold corresponding to the first opening angle of the EGR valve, and an expected pressure of the gas sucked into the intake manifold corresponding to the closing of the EGR valve after the EGR valve has been operated at the first opening angle, and second determining (or calculating)Determining or calculating, by the controller, that a leakage of the EGR system is occurring based on a measured pressure of a gas drawn into the intake manifold corresponding to a second opening angle of the EGR valve, a measured pressure of a gas drawn into the intake manifold corresponding to a closing of the EGR valve after the EGR valve has been operated at the second opening angle, an expected pressure of the gas drawn into the intake manifold corresponding to the second opening angle of the EGR valve, and an expected pressure of the gas drawn into the intake manifold corresponding to the closing of the EGR valve after the EGR valve has been operated at the second opening angle.A second measured pressure, which is calculated (or determined) using the measured pressure of the gas sucked into the intake manifold according to the first opening angle of the EGR valve and the measured pressure of the gas sucked into the intake manifold according to the closing of the EGR valve after the EGR valve has been operated at the first opening angle, may be greater than a second expected pressure, which is calculated (or determined) using the expected pressure of the gas sucked into the intake manifold according to the first opening angle of the EGR valve and the expected pressure of the gas sucked into the intake manifold according to the closing of the EGR valve after the EGR valve has been operated at the first opening angle.A third measured pressure, which is calculated (or determined) using the measured pressure of the gas sucked into the intake manifold according to the second opening angle of the EGR valve and the measured pressure of the gas sucked into the intake manifold according to the closing of the EGR valve after the EGR valve has been operated at the second opening angle, may be greater than a third expected pressure, which is calculated (or determined) using the expected pressure of the gas sucked into the intake manifold according to the second opening angle of the EGR valve and the expected pressure of the gas sucked into the intake manifold according to the closing of the EGR valve after the EGR valve has been operated at the second opening angle.

[0017] The second opening angle can be larger than the first opening angle.

[0018] The measured pressure of the gas can be measured by an intake gas pressure sensor installed in the intake manifold.

[0019] The EGR system leakage monitoring method for the engine may further include: determining (or calculating) by the controller whether a change value of a sensor value of a throttle position sensor included in the EGR system is in a stable state and lambda control, which is a control related to an air-fuel ratio of the engine, is in a stable state before determining that EGR system leakage occurs.

[0020] The EGR system leakage monitoring method for the engine may further comprise: when it is determined that EGR system leakage occurs, oxygen sensors measure a lambda value indicating that a ratio (or proportion) of a fuel supplied to the engine is in a lean state to output the measured value to the controller, and performing lambda feedback control, which is control related to an air-fuel ratio of the engine, by the controller such that the ratio (or proportion) of the fuel is changed to a rich state to set the measured lambda value to a normal lambda value of 1.

[0021] The exhaust gas recirculation system leakage monitoring method for the engine of the vehicle according to the exemplary embodiment of the invention can diagnose a small amount of flow leakage in the exhaust gas recirculation system of the engine to meet the exhaust gas recirculation (EGR) on-board diagnostic (OBD) regulations.

[0022] Furthermore, the exemplary embodiment of the invention may eliminate a differential pressure sensor or a temperature sensor used for flow rate measurement from the exhaust gas recirculation system to monitor a flow rate of leakage or a flow amount of leakage of the exhaust gas recirculation system.

[0023] The invention is explained in more detail with reference to the drawing. The drawing shows: Fig. 1 is a view for explaining an exhaust gas recirculation (EGR) system according to an exemplary embodiment of the invention; Fig. 2 is a view for explaining a control device for controlling an EGR valve used in Fig. 1 is shown; Fig. 3A and Fig. 3B are flowcharts illustrating a method for monitoring exhaust gas recirculation system leakage for an engine of a vehicle according to an exemplary embodiment of the invention; Fig. 4 is a flow chart illustrating steps after the second detection of a small amount of flow leakage of the exhaust gas recirculation system included in the Fig. 3A and Fig. 3B; and Fig. 5 is a view for explaining the step of secondly detecting a small amount of flow leakage of the exhaust gas recirculation system used in the Fig. 3A and Fig. 3B is shown.

[0024] In order to sufficiently understand the present invention and the object achieved by carrying out the present invention, reference is made to the accompanying drawings which illustrate exemplary embodiments of the present invention and contents described in the accompanying drawings.

[0025] Hereinafter, the present invention will be described in detail by describing exemplary embodiments of the present invention with reference to the accompanying drawings. In describing the present invention, well-known configurations or functions will not be described in detail since they may unnecessarily obscure the essence of the present invention. Throughout the accompanying drawings, the same reference numerals are used to denote the same components.

[0026] Terms used in this specification are used only to describe particular example embodiments rather than to limit the present invention. Singular forms are intended to include plural forms unless the context clearly indicates otherwise. It is further understood that the terms "comprise" or "have" used in this specification indicate the presence of features, integers, steps, acts, elements, or parts recited in this specification, or a combination thereof, but do not preclude the presence or addition of one or more other features, integers, steps, acts, components, parts, or a combination thereof.

[0027] Throughout the specification and the following claims, where an element is not described as being "coupled" to another element, the element may be "directly coupled" to the other element or "electrically or mechanically coupled" to the other element through a third element.

[0028] Unless otherwise defined, it is understood that the terms used in this specification, which include technical and scientific terms, have the same meaning as those commonly understood by those skilled in the art. It is understood that the terms defined by the dictionary are identical to the meanings in the context of the related technology, and they should not be defined in an ideal or overly formal way unless the context clearly dictates otherwise.

[0029] The component "unit," block, or module used in the present exemplary embodiment may be implemented in software such as a task, class, subroutine, process, task, thread, or program executed in a predetermined area in memory, or in hardware such as an application-specific programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and may be implemented with a combination of software and hardware. The component "part" or the like may be embedded in a computer-readable storage medium, and some parts thereof may be distributed across a plurality of computers.

[0030] It is necessary to monitor the flow rate leakage of an exhaust gas recirculation (EGR) system due to the introduction of on-board diagnostic (OBD) regulations.

[0031] With reference to the Fig. 1 to 5, in a determination step S200, a controller 100 may determine whether an engine 40 of the vehicle is in an idle state. For example, the controller 100 may determine whether the engine 40 is in the idle state based on a rotational speed (rpm) of the engine 40. For example, in the idle state of the engine 40, the exhaust gas recirculation system (or an EGR valve 20 and an EGR cooler 30 of the exhaust gas recirculation system) may not be operating. When the EGR valve 20 is operating, the EGR valve 20 may be open.

[0032] In the EGR system (or EGR device) installed in Fig. As shown in Figure 1, EGR gas cooled by EGR cooler 30 can flow into a combustion chamber of engine 40 via the open EGR valve 20, so that a temperature of the combustion chamber can be reduced. The EGR system can restrict a knock generation range of engine 40 and can advance an ignition timing of the engine. Therefore, the torque of engine 40 and the fuel efficiency of the vehicle can be improved.

[0033] An EGR ratio of the EGR system can be determined by considering the engine speed 40 or an engine load. The EGR ratio can be given by the following equation.

[0034] EGR ratio = EGR gas quantity / total amount of fuel-air mixture.

[0035] In the above equation, a total amount of the fuel-air mixture may be a value obtained by adding an amount or an air mass of fresh air and the EGR gas amount (e.g., an EGR gas mass).

[0036] In the idling state of the engine 40, there may be no change in the opening degree of a throttle valve that controls the intake air quantity of the engine, and the engine may be at an idle speed. An opening angle of the EGR valve 20 may be adjusted by an electric motor. If an EGR gas leak occurs during a non-operational period (e.g., an idling range of the engine 40) of the exhaust gas recirculation system, the engine start may be disabled, and the vehicle's exhaust gas may increase.

[0037] The control device 100, which is an engine management system (EMS), can control the overall operation of the exhaust gas recirculation system with the engine 40. For example, the engine 40 can be a four-cylinder engine or a multi-point fuel injection (MPI) engine. For example, the control device 100, such as an engine control unit (ECU), can be one or more microprocessors operated by a program or hardware including the microprocessor. The program can include a series of instructions for performing the method for monitoring the leakage of the exhaust gas recirculation system according to the exemplary embodiment of the invention. The instructions can be stored in a memory.

[0038] With reference to Fig. 2, the controller 100 may determine a target EGR flow rate using the vehicle state information (e.g., the rotational speed (RPM) or torque of the engine 40), the intake air pressure at a front end of an intake manifold 10, the intake air temperature at the front end of the intake manifold, the pressure of a gas (i.e., the fresh air (or a fuel-air mixture) and an EGR gas) drawn into the intake manifold, a lambda control value, and a value of a throttle position sensor TPS. The controller 100 may control operation of the EGR valve 20 based on the target EGR flow rate.

[0039] According to step S205, the controller 100 may receive an expected pressure of a gas (i.e., fresh air or a fuel-air mixture and EGR gas) drawn into the intake manifold 10 connected to the engine 40 and a measured pressure (or an actually measured pressure) of the gas drawn into the intake manifold in the engine's idle state in which the exhaust gas recirculation system is not operating. The controller 100 may determine the expected pressure of the intake gas based on a number of revolutions (e.g., a speed) of the engine, which is the vehicle state information. For example, the expected pressure may be determined through a test as a pressure expected according to an exhaust gas recirculation system, and the determined pressure may be stored in a memory.The measured pressure of the intake gas may be measured by an intake gas pressure sensor 15 installed in the intake manifold 10, and the measured pressure may be given to the controller 100.

[0040] According to step S210, in order to determine whether a change value TPS_DIF of a sensor value of the throttle position sensor TPS is in a stable state and a lambda control is in a stable state, the control device 100 may determine whether an absolute value of the change value TPS_DIF of the sensor value of the throttle position sensor TPS is smaller than a first threshold value THD1 for a predetermined time (eg, 100 ms), and whether an absolute value of a deviation of the lambda control is smaller than a second threshold value THD2.

[0041] The throttle position sensor TPS for detecting an opening angle of the throttle valve may be included in the EGR system. Lambda control may be a control related to an air-fuel ratio A / F of the engine 40, which is performed by the controller 100. The lambda λ may denote a factor corresponding to the air-fuel ratio, and the air-fuel ratio may increase as the lambda value increases. For example, the A / F may be 14.7 when the lambda is 1, and the A / F may be 14.8 when the lambda is 1.01. The lambda may represent a ratio of an actual air-fuel ratio to a stoichiometric air-fuel ratio. When the lambda is less than 1, a ratio of fuel supplied to the engine may be in a rich state in the air-fuel ratio for the engine.If the lambda exceeds 1, a ratio of a fuel may be in a lean condition in the air-fuel ratio for the engine.

[0042] According to step S215, if the absolute value of the change value of the sensor value of the throttle position sensor is less than the first threshold and the absolute value of the lambda control deviation is less than the second threshold, the controller 100 may determine whether an absolute value of a difference value between the measured pressure and the expected pressure exceeds a third threshold THD3. For example, the third threshold THD3 may be 50 hPa. If the absolute value exceeds the third threshold for a predetermined time, the controller 100 may primarily or first determine that a small amount of flow leakage of the EGR system is occurring.

[0043] According to step S220, the controller 100 may determine whether the lambda control value exceeds a value (e.g., 15%) for shifting or adjusting the fuel ratio to the rich state. If there is a slight amount of flow leakage in the EGR system, a first oxygen (O2) sensor 50 and a second oxygen sensor 70 may measure the lambda value indicating that the fuel ratio is in the lean state and may provide the measured value to the controller 100. Accordingly, the controller 100 may perform lambda control such that the fuel ratio is adjusted or changed to a rich state to adjust the measured lambda value to a normal lambda value of 1.

[0044] Oxygen sensors 50 and 70 may be installed in an exhaust pipe at a front end and a rear end of a catalyst 60 for purifying pollutants from CO, HC, and NOx contained in an exhaust gas. Oxygen sensors 50 and 70 may detect a concentration of oxygen contained in the exhaust gas. The oxygen concentration may correspond to the lambda value. Oxygen sensors 50 and 70 may provide the detected oxygen concentration to controller 100 so that controller 100 performs control related to the air-fuel ratio. In another exemplary embodiment of the invention, step S220 may be omitted.

[0045] According to step S225, after the lambda control is performed, the controller 100 may determine that a small amount of flow leakage of the exhaust gas recirculation system occurs.

[0046] According to step S230, the controller 100 may determine whether the fuel supply to the vehicle's engine 40 is shut off. For example, a state in which the fuel supply is shut off may include a deceleration state of the vehicle in which the intake gas pressure is constant.

[0047] According to step 235, the controller 100 may control or set an opening angle of the EGR valve 20 as a first opening angle (e.g., 10% of a total opening angle) when it is determined that the fuel supply to the engine 40 is shut off.

[0048] According to step S240, the controller 100 may receive a measured pressure of the gas sucked into the intake manifold 10 corresponding to the first opening angle of the EGR valve 20, and may receive a measured pressure of the gas sucked into the intake manifold 10 corresponding to a closing of the EGR valve 20 performed after the EGR valve 20 is operated at the first opening angle. The measured pressure of the intake gas may be measured by the intake gas pressure sensor 15 installed in the intake manifold 10.

[0049] According to step S245, the controller 100 may calculate a standard difference (a standard deviation) by subtracting the measured pressure of the gas sucked into the intake manifold 10 corresponding to the closing of the EGR valve 20 after operating the EGR valve 20 at the first opening angle from the measured pressure of the gas sucked into the intake manifold 10 corresponding to the first opening angle of the EGR valve 20.

[0050] According to step S250, the controller 100 may calculate an offset threshold (or an error threshold) by subtracting an expected pressure of the gas sucked into the intake manifold 10 corresponding to the closing of the EGR valve 20 after operating the EGR valve 20 at the first opening angle from an expected pressure of the gas sucked into the intake manifold 10 corresponding to the first opening angle of the EGR valve 20. The controller 100 may determine the expected pressure of the intake gas based on a number of revolutions (e.g., a speed) of the engine, which is the vehicle state information. For example, the expected pressure may be determined by a test as a pressure according to an EGR system that is expected according to the EGR system, and the determined pressure may be stored in a memory.

[0051] According to step S255, the controller 100 may determine whether a value obtained by dividing the offset threshold by the standard difference is less than a fourth threshold THD4. For example, the fourth threshold THD4 may be 0.75.

[0052] According to step S260, if the value obtained by dividing the offset threshold by the standard difference is smaller than the fourth threshold THD4, as shown in Fig. 5, the control device 100 may secondarily or secondarily determine that a small amount of flow leakage of the exhaust gas recirculation system is occurring.

[0053] Steps S230 to S260 are described in detail. If a first measured pressure, which is calculated using the measured pressure of the gas sucked into the intake manifold 10 as a result of the first opening angle of the EGR valve 20 and the measured pressure of the gas sucked into the intake manifold 10 as a result of the closing of the EGR valve 20 after the EGR valve 20 is operated at the first opening angle, is greater than a first expected pressure, which is calculated using the expected pressure of the gas sucked into the intake manifold as a result of the first opening angle of the EGR valve 20 and the expected pressure of the gas sucked into the intake manifold as a result of the closing of the EGR valve 20 after the EGR valve 20 is operated at the first opening angle, the control device 100 can secondarily determine that a small flow leakage occurs in the exhaust gas recirculation system.

[0054] According to step S265, the controller 100 may control or set an opening angle of the EGR valve 20 as a second opening angle (e.g., 20% of the total opening angle) when it is determined that the fuel supply to the engine 40 is cut off.

[0055] According to step S270, the controller 100 may receive a measured pressure of the gas sucked into the intake manifold 10 corresponding to the second opening angle of the EGR valve 20 and a measured pressure of the gas sucked into the intake manifold corresponding to a closing of the EGR valve 20 performed after the EGR valve 20 is operated at the second opening angle. The measured pressure of the intake gas may be measured by the intake gas pressure sensor 15 installed in the intake manifold 10.

[0056] According to step S275, the controller 100 may calculate a standard difference value A by subtracting the measured pressure of the gas sucked into the intake manifold corresponding to the closing of the EGR valve 20 after operating the EGR valve 20 at the second opening angle from the measured pressure of the gas sucked into the intake manifold corresponding to the second opening angle of the EGR valve 20.

[0057] According to step S280, the controller 100 may calculate a reference pressure B by subtracting an expected pressure of the gas sucked into the intake manifold corresponding to the closing of the EGR valve 20 after operating the EGR valve 20 at the second opening angle from an expected pressure of the gas sucked into the intake manifold corresponding to the second opening angle of the EGR valve 20. The controller 100 may determine the expected pressure of the intake gas based on a number of revolutions (e.g., a speed) of the engine, which is the vehicle state information. For example, the expected pressure may be determined through a test as a pressure according to an EGR system expected according to the EGR system, and the determined pressure may be stored in a memory.

[0058] According to step S285, the controller 100 may determine whether a value obtained by dividing the reference pressure B by the standard differential value A is less than a fifth threshold value THD5. For example, the fifth threshold value THD5 may be 0.75.

[0059] According to steps S290 and S295, when the value obtained by dividing the reference pressure B by the standard reference value A is smaller than the fifth threshold value THD5, the control device 100 can ultimately determine that a small amount of flow leakage occurs in the EGR system, as shown in Fig. 5 is shown.

[0060] In detail, in steps S265 to S295, if a second measured pressure calculated by means of the measured pressure of the gas sucked into the intake manifold 10 due to the second opening angle of the EGR valve 20 and the measured pressure of the gas sucked into the intake manifold 10 due to the closing of the EGR valve 20 after the EGR valve 20 is operated at the second opening angle is greater than a second expected pressure calculated by means of the expected pressure of the gas sucked into the intake manifold 10 due to the second opening angle of the EGR valve 20 and the expected pressure of the gas sucked into the intake manifold 10 due to the closing of the EGR valve 20 after the EGR valve 20 is operated at the second opening angle is sucked in, the controller 100 may ultimately determine that a small flow leakage is occurring in the EGR system.

Claims

[1] A method for monitoring the leakage of an exhaust gas recirculation (EGR) system for an engine of a vehicle, comprising the steps of: Determining by a control device (100) whether the engine (40) is in an idle state in which the EGR system is not operated (S200); Determining by the control device (100) whether a leakage of the EGR system occurs based on an expected pressure of gas sucked into an intake manifold (10) connected to the engine (40) and a measured pressure of gas sucked into the intake manifold (10) when the engine (40) is in the idle state (S205); Determining by the control device (100) that a leakage of the EGR system occurs when the measured pressure is greater than the expected pressure (S260, S290), and if it is determined that a leakage of the EGR system is occurring, ultimately determining by the control device (100) that a leakage of the EGR system is occurring based on a measured pressure of gas sucked into the intake manifold (10) corresponding to an opening angle of an exhaust gas recirculation (EGR) valve (20), a measured pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle, an expected pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20), and an expected pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated in the opening angle in a state in which the fuel supply to the engine (40) is switched off (S295), wherein a first measured pressure, which is calculated based on the measured pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20) and the measured pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle, is greater than a first expected pressure, which is calculated based on the expected pressure of gas sucked into the intake manifold (10) corresponding to the opening angle of the EGR valve (20) and the expected pressure of gas sucked into the intake manifold (10) corresponding to a closing of the EGR valve (20) after the EGR valve (20) has been operated at the opening angle. [2] The method of claim 1, wherein the controller (100) determines the expected pressure of gas based on a speed of the engine (40). [3] The method of claim 1, wherein the step of ultimately determining that an EGR system leak is occurring comprises the steps of: first determining by the control device (100) that a leakage of the EGR system is occurring based on a measured pressure of gas sucked into the intake manifold (10) corresponding to a first opening angle of the EGR valve (20), a measured pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the first opening angle, an expected pressure of gas sucked into the intake manifold (10) corresponding to the first opening angle of the EGR valve (20), and an expected pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the first opening angle (S260); and second determining by the control device (100) that a leakage of the EGR system occurs based on a measured pressure of gas sucked into the intake manifold (10) corresponding to a second opening angle of the EGR valve (20), a measured pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the second opening angle, an expected pressure of gas sucked into the intake manifold (10) corresponding to the second opening angle of the EGR valve (20), and an expected pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the second opening angle (S290), wherein a second measured pressure, which is calculated based on the measured pressure of gas sucked into the intake manifold (10) corresponding to the first opening angle of the EGR valve (20) and the measured pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the first opening angle, is greater than a second expected pressure, which is calculated based on the expected pressure of gas sucked into the intake manifold (10) corresponding to the first opening angle of the EGR valve (20) and the expected pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the first opening angle, and wherein a third measured pressure, which is calculated based on the measured pressure of gas sucked into the intake manifold (10) corresponding to the second opening angle of the EGR valve (20) and the measured pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the second opening angle, is greater than a third expected pressure, which is calculated based on the expected pressure of gas sucked into the intake manifold (10) corresponding to the second opening angle of the EGR valve (20) and the expected pressure of gas sucked into the intake manifold (10) corresponding to the closing of the EGR valve (20) after the EGR valve (20) has been operated at the second opening angle. [4] The method of claim 3, wherein the second opening angle is greater than the first opening angle. [5] A method according to any one of claims 1 to 4, wherein the measured pressure of gas is measured by an intake gas pressure sensor (15) arranged in the intake manifold (10). [6] Method according to one of claims 1 to 5, further comprising the step: before the step of determining that a leakage of the EGR system occurs, determining by the controller (100) whether a sensor value of a throttle position sensor (TPS) included in the EGR system and an air-fuel ratio (A / F) of the engine (40) are constant. [7] Method according to one of claims 1 to 6, further comprising the steps: when it is determined that a leakage of the EGR system is occurring, measuring a lambda value indicating that a ratio of a fuel supplied to the engine (40) is in a lean state by oxygen sensors (50, 70); and Performing a lambda control, which is a control related to an air-fuel ratio (A / F) of the engine (40), by the control device (100) such that the ratio of the fuel is changed to a rich state in order to set the measured lambda value to a normal lambda value of 1.

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