Device for detecting leakage of fuel evaporation control (EVAP) system and diagnosis method

Abstract

The invention discloses a device for detecting leakage of a fuel evaporation control system and a diagnosis method. The device comprises a communicating pipe, and the communicating pipe is provided with an air inlet end connected with the atmosphere and an air outlet end connected with an EVAP system in an on-off mode; the flow detector is used for detecting the flow of the gas; the pressure detector is used for detecting pressure; the calibration assembly comprises a plurality of standard holes and a plurality of switching parts; and the main control module is used for receiving the data from the flow detector to generate calibration data, and calculating the leakage equivalent aperture based on the calibration data and the current flow data when the air outlet end is connected with the EVAP system. According to the scheme, the flow is calibrated through the standard hole with the known hole diameter in the marking stage, and the corresponding relation between the flow and the hole diameter is established. During detection, the leakage equivalent aperture of the EVAP system is accurately calculated based on the calibration data and the flow detected by the flow detector, the severity of system leakage is judged, and the problem that an existing detection method cannot accurately judge the size of the leakage aperture is effectively solved.

Description

Technical Field

[0001] The present application generally relates to the field of fault detection technology. More specifically, the present application relates to a device and a diagnostic method for detecting leakage in an evaporative fuel access (EVAP) system. Background Art

[0002] With the rapid development of the automotive industry and the ever-expanding fleet size, the management of evaporative emissions from motor vehicles has become a critical component in improving the atmospheric environment. Currently, outdated evaporative emission control technology is common in gasoline vehicles. This is particularly evident in activated carbon canister breakdown and poor sealing of the evaporative fuel access system (EVAP), leading to excessive fuel vapor leakage and negatively impacting air quality. The National Phase VI Motor Vehicle Pollutant Emission Standard and "GB18285-2018 Gasoline Vehicle Pollutant Emission Limits and Measurement Methods (Dual Idle Method and Simple Operating Condition Method)" impose strict requirements for leak detection in the EVAP system: when the system leak equivalent aperture exceeds 1mm, the vehicle must trigger a fault alarm and rely on specialized equipment to accurately locate the leak and quantify its extent. However, existing detection equipment lacks accuracy, making it impossible to quantify the leak extent and, consequently, determine the specific EVAP system fault type. This makes it difficult for maintenance personnel to accurately troubleshoot the problem, resulting in a lack of targeted and inefficient remediation efforts.

[0003] In view of this, there is an urgent need to provide a device and a diagnostic method for detecting leakage in the evaporative fuel access (EVAP) system, so as to quickly detect the equivalent aperture of the EVAP system leakage, so that maintenance personnel can accurately troubleshoot the fault and improve maintenance efficiency. Summary of the Invention

[0004] In order to at least solve one or more of the technical problems mentioned above, the present application proposes in multiple aspects a device and a diagnostic method for detecting equivalent aperture leakage of the EVAP system, thereby enabling maintenance personnel to accurately troubleshoot faults and improve maintenance efficiency.

[0005] In a first aspect, the present application provides a device for detecting leakage of a fuel evaporation control (EVAP) system, the device comprising: a connecting pipe, the connecting pipe having an air inlet end and an air outlet end, the air inlet end being connected to the atmosphere, and the air outlet end being connectable and disconnectable to the EVAP system; a flow detector for detecting the flow of gas passing through the connecting pipe; a pressure detector for detecting the pressure in the connecting pipe; a calibration assembly comprising a plurality of standard holes of different sizes arranged on the connecting pipe, and a plurality of switching components for controlling the connection or disconnection of different standard holes with the device; and a main control module for receiving data from the flow detector to generate calibration data of the standard hole aperture and flow rate, and calculating the leakage equivalent aperture based on the calibration data and current flow rate data when the air outlet end is connected to the EVAP system.

[0006] In some embodiments, the main control module is also connected to an on-board diagnostic system (OBD) reading module or a sensor module to obtain the vehicle's operating parameters, and determines the carbon canister desorption function by comparing the obtained operating parameters with preset parameters.

[0007] In some embodiments, a pressure reducing filtration module is further included, which is arranged at the air inlet end; the pressure reducing filtration module includes: a pressure reducing device for stabilizing the gas pressure to a preset working range; and a filtering device for removing impurities in the gas.

[0008] In some embodiments, two pressure detectors are connected to the connecting pipe, one of which is arranged between the pressure reducing filtration module and the flow detector, and the other is arranged between the flow detector and the calibration component.

[0009] In some embodiments, the main control module is integrated with an environmental parameter correction unit for dynamically compensating the flow and pressure detection results based on the real-time collected temperature and atmospheric pressure.

[0010] In some embodiments, the main control module stores a mapping relationship between equivalent aperture and fault cause, and outputs the corresponding fault cause based on the detected leakage equivalent aperture.

[0011] In the second aspect, the present application provides a fuel evaporation control (EVAP) system leakage diagnosis method based on the above-mentioned device, and the diagnosis method includes the following steps: calibration stage: disconnect the air outlet and the EVAP system, and after the pressure in the control device is stabilized at a preset value, turn on the different standard holes in the calibration component, record the flow data corresponding to each standard hole to generate calibration data; leakage equivalent aperture detection stage: connect the air outlet and the EVAP system, inject gas into the system and maintain a stable pressure, and calculate the leakage equivalent aperture based on the current flow data and calibration data.

[0012] In some embodiments, if the detected leakage equivalent aperture is smaller than a preset value, a pressure decay detection is performed after the leakage equivalent aperture detection stage. The pressure decay detection includes: cutting off the gas source, monitoring the pressure change value within a preset time, and if it exceeds a first threshold, it is determined that there is a leak in the EVAP system.

[0013] In some embodiments, a self-leakage detection is performed before the calibration stage, including: disconnecting the air outlet from the EVAP system, turning on all switching components to purge the inside of the device; after the purge is completed, turning off the flow detector and detecting the pressure change, if the pressure change value exceeds a second threshold, it is determined that the device has self-leakage.

[0014] In some embodiments, the diagnostic method further includes detecting the desorption function of the carbon canister, wherein the detection method is to obtain operating parameters of the vehicle and compare the operating parameters with preset parameters to determine the desorption function of the carbon canister.

[0015] Through the apparatus for detecting evaporative fuel injection (EVAP) system leaks provided above, embodiments of the present application establish calibration data for the flow rate-to-aperture relationship by calibrating the flow rate using a standard aperture of known aperture during the marking phase. During actual testing, the EVAP system's leakage equivalent aperture is accurately calculated based on the calibration data and the flow rate detected by the flow detector, enabling precise determination of the severity of the EVAP system leak. This effectively addresses the issue of existing detection methods' low precision and inability to accurately determine the size of the leak aperture. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the exemplary embodiments of the present application will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0017] Figure 1 A schematic diagram of a device for detecting leakage in an evaporative fuel access control (EVAP) system according to the present invention is shown;

[0018] Figure 2 A flow chart of a method for diagnosing a leak in an evaporative fuel access (EVAP) system in some embodiments of the present application is shown;

[0019] Figure 3 A flow chart of a method for diagnosing a leak in an evaporative fuel access (EVAP) system in some embodiments of the present application is shown;

[0020] Figure 4 A flow chart of a fuel evaporation control (EVAP) system leak diagnosis method in some embodiments of the present application is shown.

[0021] In the figure: 100, a device for detecting leakage of a fuel evaporation control system;

[0022] 101. Connecting pipe; 102. Fuel evaporation control system; 103. Flow detector; 104. Pressure detector; 105. Calibration component; 1051. Standard hole; 1052. Switching component; 106. Main control valve; 107. Connecting valve; 108. Pressure relief valve; 109. Main control module; 110. Pressure reducing filter module; 111. Main control board; 112. Fan; 113. Indicator light. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0024] It should be understood that the terms "include" and "comprising" used in the description and claims of this application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0025] It should also be understood that the terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this specification and claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" as used in this specification and claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.

[0026] As used in this specification and claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0027] The specific implementation of the present application will be described in detail below with reference to the accompanying drawings.

[0028] like Figure 1As shown, in some embodiments, a device 100 for detecting leakage of a fuel evaporation control (EVAP) system is provided, the device comprising: a connecting pipe 101, the connecting pipe 101 having an air inlet end and an air outlet end, the air inlet end being connected to the atmosphere, and the air outlet end being connected and disconnected to the EVAP system; a flow detector 103 for detecting the flow of gas passing through the connecting pipe 101; a pressure detector 104 for detecting the pressure in the connecting pipe 101; a calibration component 105, comprising a plurality of standard holes 1051 of different sizes arranged on the connecting pipe 101, and a plurality of switching components 1052 for controlling the connection or disconnection of different standard holes 1051 with the device; and a main control module 109 for receiving data from the flow detector 103 to generate calibration data of the aperture and flow of the standard hole 1051, and calculating the leakage equivalent aperture based on the calibration data and the current flow data when the air outlet end is connected to the EVAP system.

[0029] Those skilled in the art will understand that the EVAP system, as a closed-loop management system for fuel vapor in motor vehicles, consists of a fuel tank, an activated carbon canister, a solenoid valve, and connecting pipes. This system achieves its environmental protection function through the following mechanisms: when the vehicle is turned off, fuel tank vapor is adsorbed and stored in the canister; when the engine is running, the solenoid valve opens, and the vapor is introduced through the pipes into the combustion chamber for full combustion, achieving fuel vapor recovery and reuse. Because the EVAP system's environmental effectiveness relies entirely on its airtightness, leakage from any component (such as a punctured canister) or interface (such as a crack in the pipe) will cause fuel vapor to escape.

[0030] In order to solve the above problems, the present invention provides a detection device for diagnosing leakage of the fuel evaporation control (EVAP) system. Specifically, the device 100 for detecting leakage of the EVAP system includes a connecting pipe 101, a flow detector 103, a pressure detector 104, a calibration component 105 and an active module. Specifically, the connecting pipe 101 is a channel for gas flow, one end of which is connected to the atmosphere and the other end can be connected or disconnected with the EVAP system. When it is necessary to detect whether there is a leak in the EVAP system, the air outlet end of the connecting pipe 101 is connected to the EVAP system; and when performing device self-test or calibration, the air outlet end is disconnected from the EVAP system. A pressure detector 104 and a flow detector 103 are connected to the connecting pipe 101, wherein the pressure sensor is used to detect the pressure in the connecting pipe 101 in real time, and the flow detector 103 is used to detect the gas flow through the connecting pipe 101.

[0031] The connecting tube 101 is also provided with a calibration assembly 105, which includes a plurality of standard holes 1051 of different diameters (e.g., 0.25 mm, 0.5 mm, 1 mm, 1.5 mm, and 2 mm) and a switching component 1052 provided on the connecting tube 101 corresponding to each of the different standard holes 1051. The diameters of the standard holes 1051 are known and precise, and the switching component 1052 can control whether the different standard holes 1051 are connected to or disconnected from the connecting tube 101. During the calibration process, after the pressure in the control device 104 is maintained at a stable state, the standard holes 1051 of different diameters are opened in sequence, allowing gas to flow through the standard holes 1051. Simultaneously, the flow detector 103 measures the corresponding flow data, thereby establishing a correspondence between the diameter of the standard holes 1051 and the flow rate, and generating calibration data.

[0032] The detection device provided by this solution also includes a main control module 109, which is in communication with the flow detector 103, the pressure detector 104, and the switching component 1052 in the calibration component 105. The main control module 109 can receive data from the flow detector 103 and the pressure detector 104 to generate instructions for controlling the switch of the switching component 1052, and can also generate calibration data and calculate the leakage equivalent aperture. Specifically, during the calibration phase, the main control module 109 receives the pressure data detected by the pressure detector 104, and after the pressure data stabilizes, it sequentially issues different control instructions to control the switching component 1052 to conduct standard holes 1051 of different apertures, obtain flow data corresponding to the apertures of different standard holes 1051, and generate calibration data of the aperture and flow of the standard hole 1051, and establish a corresponding relationship between the flow rate and the aperture. When actually testing the EVAP system, all switching components 1052 of the control calibration assembly are in the open state, connecting the air intake end and the EVAP system. When the main control module 109 detects that the pressure is the same as the pressure during the calibration stage, it starts to measure whether the EVAP system is leaking, that is, the main control module 109 receives the flow data measured by the current flow detector 103, and queries and compares the leakage equivalent aperture of the EVAP system based on the calibration data generated in the marking stage, that is, queries the calibration data to see how large the aperture of the standard hole 1051 will cause the currently measured gas leakage flow.

[0033] This solution calibrates the flow rate using a standard orifice 1051 of known diameter during the marking phase, establishing a corresponding relationship between flow rate and aperture. During actual testing, this calibration relationship allows the EVAP system's leakage equivalent aperture to be accurately calculated based on the flow rate detected by the flow detector 103. This allows the severity of EVAP system leaks to be precisely determined, effectively resolving the issue of existing detection methods' low precision and inability to accurately determine leak aperture size.

[0034] In a specific embodiment, a pressure reducing filtration module 110 is further included, which is arranged at the air inlet end; the pressure reducing filtration module 110 includes: a pressure reducing device for stabilizing the gas pressure to a preset working range; and a filtering device for removing impurities in the gas.

[0035] In this solution, a pressure-reducing filter module 110 is also installed on the connecting pipe at the air inlet end. This module 110 includes a pressure-reducing device and a filter. The pressure-reducing device is used to stabilize the gas pressure within a preset operating range, providing a stable gas source for subsequent flow and pressure testing processes, ensuring the accuracy and reliability of the test results. The filter effectively removes impurities from the gas, preventing them from entering the testing equipment or EVAP system, and preventing impurities from wearing, clogging, or damaging precision components, thereby extending the equipment's service life and improving the system's stability and reliability.

[0036] It is worth noting that this solution does not limit the specific structures of the pressure reducing device and the filtering device. For example, in some specific embodiments, the pressure reducing device can be a pressure regulating valve or a pressure reducing valve, and the filtering device can be a filter or a filter.

[0037] In a specific embodiment, two pressure detectors 104 are connected to the connecting pipe 101, wherein one pressure detector 104 is arranged between the pressure reducing filtration module 110 and the flow detector 103, and the other pressure detector 104 is arranged between the flow detector 103 and the specified module.

[0038] In this solution, a pressure reducing filter module 110, a pressure detector 104, a main control valve 106, a flow detector 103, a pressure detector 104 and a calibration component 105 are sequentially provided on the connecting pipe 101 from the air inlet end to the air outlet end. That is to say, this solution is provided with two pressure detectors 104, one of which is provided between the pressure reducing filter module 110 and the flow detector 103, and is used to monitor the gas pressure after the pressure reducing filtration, and ensures the pressure stability by cooperating with the pressure reducing filter module 110. The other pressure detector 104 is provided between the flow detector 103 and the calibration component 105. The pressure detector is used to monitor the pressure between the flow detector 103 and the calibration module to ensure that each time the standard hole is turned on, the gas pressure is the same as the pressure when the EVAP system is actually detected (that is, consistent with the pressure after the pressure reducing filtration), thereby ensuring the accuracy of the calibration.

[0039] It's worth noting that the connecting pipe 101 in this embodiment is equipped with a connecting valve 107 that controls the flow of gas between the outlet and the EVAP system. When the EVAP system needs to be tested, connecting valve 107 is opened to allow gas to enter the system. When testing is not required or other operations are being performed, such as self-testing or calibration, connecting valve 107 is closed to cut off the gas supply. Furthermore, a pressure relief valve 108 is installed between connecting valve 107 and the EVAP system. This valve automatically opens when gas pressure exceeds a preset safety level, releasing excess gas and preventing damage to the EVAP system and testing equipment caused by excessive pressure.

[0040] It's also worth noting that the main control module in this solution is equipped with a main control board 111, which runs the environment correction algorithm, control logic decision-making, and data storage and analysis. The main control module is also equipped with a fan 112 and an indicator light 113. Fan 112 is used to cool the main control module, and indicator light 113 indicates the device status, allowing operators to determine whether the device needs maintenance based on the indicator light.

[0041] In a specific implementation scheme, the main control module 109 is integrated with an environmental parameter correction unit for dynamically compensating the flow and pressure detection results according to the temperature and atmospheric pressure collected in real time.

[0042] It is understood by those skilled in the art that the flow rate of gas is affected by temperature and pressure. Therefore, the main control module 109 in this solution is integrated with an environmental parameter correction unit for dynamically compensating the flow rate and pressure detection results based on the real-time collected temperature and atmospheric pressure. Specifically, the temperature and air pressure are obtained in real time by sensors, and the flow rate and pressure are corrected according to the Bernoulli equation (Formula 1) and the gas state equation (Formula 2):

[0043]

[0044] Q: standard state volume flow rate (standard flow rate, unit: slm);

[0045] Δp: measured pressure difference (kPa);

[0046] ρ: Current gas density (kg / m 3 );

[0047] T: real-time ambient temperature (K);

[0048] P: real-time atmospheric pressure (kPa);

[0049] T0, P0, ρ0: standard state reference values;

[0050] The following is a detailed introduction to the flow correction steps:

[0051] Flow calibration value correction:

[0052] The calibration flow rate Q of standard holes with different apertures cal Convert to standard flow: Then generate the aperture-standard flow calibration data.

[0053] Measured flow correction:

[0054] The measured flow rate Q meas Synchronously convert to standard flow:

[0055] It is worth noting that in the actual detection process, Q is used to determine the leakage aperture equivalent. meas，std Compare with the aperture-standard flow calibration data to determine the actual leakage equivalent aperture.

[0056] The following are the steps for pressure correction:

[0057] The pressure sensor provides real-time feedback of the system pressure P sys ;

[0058] The main control module calculates the required compensation flow rate based on environmental parameters and dynamically increases or decreases the gas injection volume;

[0059] The above process is repeated until P sys Stabilize at the target value (such as 3.5kPa).

[0060] This solution uses the environmental parameter correction unit to accurately correct the detected flow and pressure data based on the real-time collected temperature and atmospheric pressure, thereby more accurately reflecting the actual leakage situation of the vehicle EVAP system under the actual operating environment, including key information such as the size of the leakage aperture, avoiding detection errors caused by environmental factors, and improving the accuracy of the detection results.

[0061] In a specific embodiment, the main control module 109 is also connected to an on-board diagnostic system (OBD) reading module or a sensor module to obtain the operating parameters of the vehicle, and determines the carbon canister desorption function by comparing the obtained operating parameters with preset parameters.

[0062] In this solution, the main control module 109 is connected to the OBD reader module via a communication interface such as a controller area network (CAN) bus. The OBD reader module is responsible for obtaining vehicle operating parameters, such as engine speed, coolant temperature, and fuel tank pressure, from the vehicle's OBD interface. After obtaining the actual operating parameters, they are compared one by one with the preset vehicle operating parameters pre-stored in the main control module 109 to analyze and determine the carbon canister's desorption function. For example, if the engine coolant temperature is preset to reach a certain range during carbon canister desorption, if the actual coolant temperature obtained is lower than the preset coolant temperature range, it means that the engine has not reached a thermal state suitable for desorption and cannot effectively burn the fuel vapor desorbed from the carbon canister, thereby determining that there is a problem with the carbon canister's desorption function.

[0063] This solution can determine the desorption function of the carbon canister by comparing the obtained operating parameters with the preset parameters, detect potential faults in a timely manner, ensure that the vehicle meets environmental protection regulations, and reduce the vehicle's pollution to the atmospheric environment.

[0064] Those skilled in the art will appreciate that this solution does not limit the specific form of obtaining vehicle operating parameters. That is, in other implementation schemes, the main control module 109 may obtain the vehicle operating parameters through sensors instead of through the on-board diagnostic system (OBD) reading module.

[0065] In a specific implementation scheme, the main control module 109 stores a mapping relationship between equivalent apertures and fault causes, and outputs the corresponding fault cause based on the detected leakage equivalent aperture.

[0066] In this solution, the main control module 109 stores a mapping relationship between equivalent aperture and fault cause based on a large number of experiments and actual vehicle fault data, and outputs the corresponding fault cause based on the detected leakage equivalent aperture. Specifically, a database is pre-established through experiments and data analysis, which records in detail the possible fault causes corresponding to different equivalent apertures. When a leak is detected in the EVAP system, the main control module 109 will search for the corresponding fault cause in the database based on the actual measured leakage equivalent aperture and output it. For example, if the detected leakage equivalent aperture is 0.5mm, according to the mapping relationship, it corresponds to a poor seal of the carbon canister solenoid valve, and the main control module 109 outputs a poor seal of the solenoid valve. If the detected leakage equivalent aperture is 2mm, according to the mapping relationship, it corresponds to a damaged fuel tank cap seal or a ruptured fuel line, and the main control module 109 outputs a damaged fuel tank cap seal or a ruptured fuel line. This arrangement enables maintenance personnel to quickly locate the specific cause of the leakage based on the content output by the main control module 109, greatly reducing the time and workload of maintenance personnel in troubleshooting and reducing the risk of environmental pollution caused by evaporation leakage of the vehicle.

[0067] The device 100 for detecting leakage of the fuel evaporation control system 102 provided in the present application can not only detect the leakage of the EVAP system, but also read the key parameters of the vehicle through OBD, determine the rationality of the carbon canister desorption strategy, and realize all-round and multi-dimensional detection of the EVAP system, which can more comprehensively evaluate the performance and operating status of the EVAP system and provide a more complete basis for vehicle maintenance and management.

[0068] like Figure 2 As shown, in some embodiments, the present application provides a fuel evaporation control (EVAP) system leakage diagnosis method based on the above-mentioned device, and the diagnosis method includes the following steps: calibration stage: disconnect the air outlet and the EVAP system, and after the pressure in the control device is stabilized at a preset value, turn on the different standard holes 1051 in the calibration component 105, and record the flow data corresponding to each standard hole 1051 to generate calibration data; leakage equivalent aperture detection stage: connect the air outlet and the EVAP system, inject gas into the system and maintain a stable pressure, and calculate the leakage equivalent aperture based on the current flow data and calibration data.

[0069] The leakage diagnosis method of the fuel evaporation control (EVAP) system in this scheme includes a calibration stage and a leakage equivalent aperture detection stage. Specifically, in the calibration stage, the connecting valve 107 and the pressure relief valve 108 are first opened to disconnect the outlet end from the EVAP system to ensure that the gas does not flow into the EVAP system during the calibration process, thereby avoiding external interference and ensuring the accuracy of the calibration. Then, the main control valve 106 is controlled to close and the air inlet end is allowed to enter the connecting pipe 101, and the pressure in the control device is stabilized at a preset value through components such as the pressure reducing filter module 110 and the pressure detector 104. Next, by closing different switching components 1052 in turn, the standard holes 1051 of different apertures in the calibration component 105 are turned on one by one, and the flow data measured by the flow detector 103 of the corresponding standard hole 1051 is recorded. These flow data are combined with the known aperture of the standard hole 1051 to form the calibration data.

[0070] When the calibration phase is completed, the next step is to enter the leakage equivalent aperture detection phase. Specifically, open the connecting valve 107 and the pressure relief valve 108 to connect the outlet end of the connecting pipe 101 to the EVAP system, turn on the detection device to inject gas into the system, and then dynamically adjust the intake flow through the pressure control module to maintain the internal pressure of the EVAP system stable at a preset value (such as 3.5kPa). The flow detector 103 continuously measures the flow of the injected gas and transmits the data to the main control module 109 in real time. Based on the current flow data, the main control module 109 retrieves the standard hole 1051 aperture-flow mapping relationship established in the calibration phase, and calculates the actual leakage equivalent aperture of the EVAP system through the interpolation algorithm.

[0071] The diagnostic method provided by this solution, due to the provision of a calibration phase, can obtain calibration data for the aperture and flow rate of the standard hole 1051 through regular calibration or calibration before each test, which can effectively offset measurement deviations caused by factors such as equipment aging and environmental changes, ensuring that the test data is always consistent and reliable. In addition, the main control module 109 in this solution can quickly calculate the leakage equivalent aperture based on the detected flow data and the aperture and flow correspondence established in the calibration phase during the leakage equivalent aperture detection phase. Maintenance personnel can use this to determine the severity of the leak and the most likely source of the fault, achieving efficient fault location, significantly reducing diagnostic time, improving maintenance efficiency, and sharply reducing vehicle downtime and maintenance costs.

[0072] In a specific embodiment, during the calibration process, the environmental parameter correction unit integrated in the main control module 109 corrects the flow and pressure detection results, that is, dynamic compensation. The specific correction steps have been described in detail above and will not be described again here.

[0073] like Figure 3 As shown, in a specific embodiment, if the detected leakage equivalent aperture is smaller than a preset value, a pressure decay detection is performed after the leakage equivalent aperture detection stage. The pressure decay detection includes: cutting off the gas source, monitoring the pressure change value within a preset time, and if it exceeds a first threshold value, it is determined that there is a leak in the EVAP system.

[0074] In this solution, if the leakage equivalent aperture is detected to be less than the preset value during the leakage equivalent aperture detection phase, it indicates that there is no obvious leakage in the EVAP system. Therefore, a pressure decay test is required after the leakage equivalent aperture detection phase to further detect whether there is a small leak in the EVAP system. Specifically, after completing the leakage equivalent aperture test, the gas supply source is turned off, so that the EVAP system is in a closed state. In this way, the internal pressure of the system is observed to change over time when there is no gas replenishment, and then it is determined whether there is a leak in the system. Then, a pressure sensor is used to monitor the pressure change value within a preset time. If the pressure change exceeds a first threshold value, it is determined that there is a leak in the EVAP system. The size of the pressure change value reflects the severity of the leak. The greater the pressure change, the more serious the leak.

[0075] In one specific implementation, the monitored pressure data is plotted as a pressure decay curve, visually demonstrating the pressure change trend over time. The shape of the pressure decay curve (e.g., linear decline, sudden drop, etc.) is then used to determine the type of leak. For example, a linear decline may indicate a fine crack or interface leakage.

[0076] Furthermore, if a system leak is detected, this solution calculates the leak equivalent aperture based on calibration data. Finally, a comprehensive diagnostic report containing both the equivalent aperture and pressure decay curve is generated, providing detailed diagnostic information to maintenance personnel. This report not only provides quantitative leak equivalent aperture data but also demonstrates the dynamic characteristics of the system leak through the pressure decay curve, helping maintenance personnel gain a more comprehensive understanding of the EVAP system's operating status.

[0077] Those skilled in the art will appreciate that the first threshold in this solution is set in accordance with the relevant provisions of GB18285-2018.

[0078] like Figure 4 As shown, in a specific implementation scheme, a self-leakage detection is performed before the calibration stage, including: disconnecting the air outlet from the EVAP system, turning on all switching components 1052 to purge the inside of the device; after the purge is completed, turning off the flow detector 103 and detecting the pressure change, if the pressure change value exceeds the second threshold value, it is determined that the device has self-leakage.

[0079] In this solution, before conducting the formal test, the device's air outlet is disconnected from the vehicle's EVAP system, placing the device in an isolated, closed state to prevent external interference with the device's leak detection. The device's main control valve 106 and all switching components 1052 in the calibration assembly 105 are opened, allowing a high-flow gas flow to purge the device's internal air circuits. This operation removes residual gas impurities, condensed water, or other contaminants that could affect test accuracy, ensuring a pure testing environment.

[0080] After the purge is complete, the flow detector 103 is closed, creating a closed air path within the device. The pressure sensor then monitors the pressure changes within the device in real time. If the pressure change exceeds a second threshold within a preset time, the device is considered to have a leak and requires maintenance or calibration. If the pressure change is within the threshold, the device is leak-tight and can proceed to the subsequent calibration phase.

[0081] In a specific embodiment, the diagnostic method further includes detecting the desorption function of the carbon canister, and the detection method is to obtain the operating parameters of the vehicle and compare the operating parameters with preset parameters to determine the desorption function of the carbon canister.

[0082] The diagnostic method in this solution also needs to detect the operating parameters of the vehicle when it is in operation, compare the obtained operating parameters with the preset parameters, and then judge the desorption function of the carbon canister. Specifically, in the diagnostic process, the OBD (on-board self-diagnostic system) interface is first used to read the key operating parameters of the vehicle according to the corresponding protocol, such as vehicle speed, speed, throttle, manifold pressure, coolant temperature, catalyst temperature, fuel tank pressure, etc. The OBD system is a system that comes with the vehicle and is used to monitor and manage vehicle emissions and operating status. These parameters can be easily obtained by connecting and communicating with the OBD system. If certain parameters cannot be read from the OBD, corresponding sensors will be installed, such as a fuel tank pressure sensor, to directly obtain the required parameters.

[0083] After obtaining the actual operating parameters, they are compared with the preset parameters. The preset parameters are thresholds or ranges determined based on the performance of the carbon canister desorption function during normal vehicle operation, as well as relevant technical standards and experience, including water temperature thresholds, catalyst temperature thresholds, vacuum degree, etc. These preset parameters represent the conditions that the vehicle operating parameters should meet when the carbon canister desorption function is normal. Through comparative analysis, if the actual operating parameters are within a reasonable range and meet the conditions of the preset parameters, the carbon canister desorption function is judged to be normal; conversely, if the actual operating parameters deviate from the range specified by the preset parameters, it is judged that the carbon canister desorption function may be abnormal.

[0084] This solution not only promptly identifies any inconsistencies in the carbon canister purge strategy and ensures the proper functioning of the canister purge function, thereby effectively reducing vehicle evaporative emissions and complying with environmental standards, but also eliminates the risk of fraudulent evaporative leak diagnosis using OBD, reducing the likelihood of fraud and improving the reliability and fairness of vehicle emissions testing.

[0085] The diagnostic method provided by this solution can not only eliminate the impact of the environment on the test results by correcting the flow and pressure, but also accurately determine the leakage equivalent aperture and determine the specific fault type of the EVAP system, allowing maintenance personnel to accurately troubleshoot problems and improve maintenance efficiency.

[0086] Although multiple embodiments of the present application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art can conceive of many changes, modifications, and alternatives without departing from the thought and spirit of the present application. It should be understood that in the process of practicing the present application, various alternatives to the embodiments of the present application described herein can be adopted. The accompanying claims are intended to define the scope of protection of the present application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A device for detecting leakage in an evaporative fuel access (EVAP) system, characterized in that: The device comprises: A connecting pipe, the connecting pipe having an air inlet end and an air outlet end, the air inlet end being connected to the atmosphere, and the air outlet end being connected to the EVAP system in an on-off manner; a flow detector, used to detect the flow of gas passing through the connecting pipe; a pressure detector, used to detect the pressure in the connecting pipe; a calibration assembly comprising a plurality of standard holes of different sizes provided on the connecting pipe, and a plurality of switching components for controlling the connection or disconnection of the different standard holes with the device; and The main control module is used to receive data from the flow detector to generate calibration data of the standard aperture and flow rate, and when the outlet end is connected to the EVAP system, calculate the leakage equivalent aperture based on the calibration data and current flow rate data.

2. The device according to claim 1, characterized in that: The main control module is also connected to an on-board diagnostic system (OBD) reading module or a sensor module to obtain the vehicle's operating parameters, and determines the carbon canister desorption function by comparing the obtained operating parameters with preset parameters.

3. The device according to claim 1, characterized in that: It also includes a decompression filter module, which is located at the air inlet end; the decompression filter module includes: A pressure reducing device for stabilizing the gas pressure within a preset operating range; and Filtering device, used to remove impurities from the gas.

4. The device according to claim 3, characterized in that: The connecting pipe is connected to two pressure detectors, one of which is arranged between the pressure reducing filter module and the flow detector, and the other is arranged between the flow detector and the calibration component.

5. The device according to any one of claims 1 to 4, characterized in that: The main control module is integrated with an environmental parameter correction unit for dynamically compensating flow and pressure detection results based on the temperature and atmospheric pressure collected in real time.

6. The device according to claim 1, characterized in that: The main control module stores a mapping relationship between equivalent aperture and fault cause, and outputs the corresponding fault cause based on the detected leakage equivalent aperture.

7. A method for diagnosing leakage in an evaporative fuel access (EVAP) system based on the device according to any one of claims 1 to 6, characterized in that: The diagnostic method comprises the following steps: Calibration stage: Disconnect the outlet from the EVAP system. After the pressure in the control device stabilizes at the preset value, open the different standard holes in the calibration component in sequence and record the flow data corresponding to each standard hole to generate calibration data. Leakage equivalent aperture detection stage: Connect the air outlet to the EVAP system, inject gas into the system and maintain a stable pressure, and calculate the leakage equivalent aperture based on the current flow data and calibration data.

8. The diagnostic method according to claim 7, characterized in that If the detected leakage equivalent aperture is smaller than a preset value, a pressure decay test is performed after the leakage equivalent aperture test phase. The pressure decay test includes: Cut off the gas source, monitor the pressure change value within a preset time, and determine that the EVAP system has a leak if the pressure exceeds a first threshold.

9. The diagnostic method according to claim 7 or 8, characterized in that Perform a self-leak test before the calibration phase, including: Disconnect the outlet from the EVAP system and open all switching components to purge the inside of the device; After the purge is completed, the flow detector is closed and the pressure change is detected. If the pressure change value exceeds the second threshold, it is determined that the device has self-leakage.

10. The method according to claim 7 or 8, characterized in that The diagnostic method further includes detecting the desorption function of the carbon canister, wherein the detection method is to obtain operating parameters of the vehicle and compare the operating parameters with preset parameters to determine the desorption function of the carbon canister.

Images