A method of optimizing fuel system leak diagnosis

Abstract

The application discloses a method for optimizing fuel system leakage diagnosis, which comprises the following steps: obtaining the DMTL current value I2 corresponding to the U-shaped section structure pipeline with accumulated oil and system leakage and the gas generated by DMTL reaching pressure balance with the gas of system leakage, and the time T2 required for DMTL to reach the current I2 when the U-shaped section has no accumulated oil and the system has no leakage; after the DMTL system triggers diagnosis, the DMTL works at the maximum current Im for 10s, and then the DMTL is turned on to balance the pressure in the oil tank with the outside; starting the leakage diagnosis, after 300s, if the current value of the DMTL reaches I2, it is judged that the fuel system has no leakage, and if the current value of the DMTL cannot reach I2, it is judged that the fuel system has leakage. The application not only has simple structure, convenient diagnosis and good stability, but also effectively expands the application range of the DMTL while ensuring the strength of the vehicle body structure.

Description

Technical Field

[0001] This invention belongs to the field of fuel system leak diagnosis technology, and specifically relates to an optimized method for fuel system leak diagnosis. Background Technology

[0002] With the implementation of the China VI emission standard, new limits have been added for "evaporative emissions" and "fuel emissions" of the entire vehicle, with the fuel system having a significant impact. Upgrading fuel system technology reduces evaporative emissions, while simultaneously adding an OBD system to monitor fuel leaks. This system monitors the sealing of the entire evaporative system (excluding the pipes and joints between the charcoal canister solenoid valve and the engine) to prevent fuel vapor from leaking into the atmosphere. This monitoring unit is called the Fuel Evaporative Emission Leakage Diagnostic System. This system performs diagnostics and records data under specific driving cycles and external conditions. During the diagnostic process, if one or more leak points are found in the fuel system, and the leakage from these leak points is greater than or equal to the leakage from a standard orifice as specified by regulations, satisfying a certain logical algorithm, the engine malfunction indicator lamp will illuminate to remind the user to check for leaks and repair them, thus preventing environmental pollution and fuel waste caused by direct release of fuel vapors into the atmosphere.

[0003] The DMTL fuel evaporative emission leak diagnostic system is a diagnostic system introduced to meet the China VI OBD requirements. The test begins after the vehicle is stopped. DMTL pumps air into the fuel tank system. (See attached image.) Figure 1 When diagnosing the DMTL system, a driving cycle as specified below must first be met, see [link to relevant documentation]. Figure 6 Park and turn off the engine. Figure 1 The system shown has a problem: if the pipeline being tested has a U-shaped section and there is oil accumulation in the U-shaped section, the gas pumped out by the DMTL may not be able to pass through the U-shaped section. The existing leak diagnosis strategy may make a misjudgment. Therefore, it is urgent to develop an optimized method for fuel system leak diagnosis to solve the above technical problems. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention provides an optimized method for fuel system leak diagnosis, which is not only simple in structure, convenient in diagnosis, and has good stability, but also effectively expands the application scope of DMTL while ensuring the strength of the vehicle body structure.

[0005] This invention discloses an optimized method for diagnosing fuel system leaks, applicable to fuel systems including a U-shaped segment pipeline. The U-shaped segment pipeline comprises a first pipeline segment, a second pipeline segment, a third pipeline segment, and a fourth pipeline segment. The first and third pipeline segments are arranged in parallel, as are the second and fourth pipeline segments. The first and third pipeline segments are connected via the second pipeline segment, which is connected to the fuel tank. One end of the fourth pipeline segment is connected to the carbon canister, and the other end is connected to the third pipeline segment. The carbon canister is connected to the DMTL (Digital Digitizer Tolerancing). The first pipeline section is vertically positioned below the longitudinal beam of the vehicle body, and is vertically positioned to the side of the longitudinal beam. The distance between the central axis of the first pipeline section and the central axis of the third pipeline section is H, where H = P / ρ*g, P is the pressure generated by the DMTL when it operates at its maximum current Im, ρ is the gasoline density, and g is the acceleration due to gravity. The optimized steps for fuel system leak diagnosis include obtaining the DMTL current value I2 when there is oil accumulation in the U-shaped section pipeline and the system leaks, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking from the system, and the time T required for the DMTL to reach current I2 when there is no oil accumulation in the U-shaped section and no system leak. 2； After the DMTL system triggers the diagnostic, the DMTL operates at the maximum allowable current Im for 10 seconds, and then the DMTL is turned on to balance the pressure inside the fuel tank with the external pressure. Leak diagnosis begins. If the current value of the DMTL reaches I2 after 300 seconds, it is determined that there is no leak in the fuel system; if the current value of the DMTL does not reach I2 after 300 seconds, it is determined that there is a leak in the fuel system.

[0006] In a preferred embodiment of the present invention, leakage diagnosis is initiated. If the current value of DMTL reaches I2 after 300 seconds, it is determined that there is no leakage in the fuel system; if the current value of DMTL does not reach I2 after 300 seconds, it is determined that there is a leakage in the fuel system.

[0007] In a preferred embodiment of the present invention, the method for obtaining the DMTL current value I2 includes:

[0008] S1, When there is no gasoline in the U-shaped section pipeline and the system is not leaking, record the corresponding data of current and time when the DMTL is working;

[0009] S2, fill the U-shaped section pipe with gasoline, DMTL operates at the maximum allowable current Im for 10s, blow the gasoline into the fuel tank, and obtain the remaining amount of gasoline in the U-shaped section pipe as Um;

[0010] S3, When there is no gasoline in the U-shaped section pipeline and the system is leaking, add the remaining oil Um from S2 into the U-shaped section pipeline and record the corresponding data of current and time when DMTL is working;

[0011] S4. Plot the DMTL current and time data obtained from S1-S3 into a rectangular coordinate system to obtain a fitted curve. The horizontal axis represents time and the vertical axis represents current. Based on the fitted curve, obtain I2. I2 is the DMTL current value when there is oil accumulation in the U-shaped section of the pipeline and the system leaks, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking from the system. T2 is the time required for the DMTL to reach current I2 when there is no oil accumulation in the U-shaped section and no system leak.

[0012] In a preferred embodiment of the present invention, in S3, the method for realizing system leakage includes installing a standard leak hole on a first pipeline section.

[0013] In a preferred embodiment of the invention, the standard leak hole is located near the connection between the first pipeline section and the oil tank.

[0014] In a preferred embodiment of the present invention, the first pipeline section, the second pipeline section, the third pipeline section, and the fuel tank are all located below the vehicle floor.

[0015] In a preferred embodiment of the present invention, I2 is the DMTL current value corresponding to the condition where there is oil accumulation in the U-shaped section pipeline, the system leaks, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking from the leak hole.

[0016] In a preferred embodiment of the present invention, the conditions for triggering diagnostics in the DMTL system include:

[0017] The test vehicle completes one driving cycle and is then parked and turned off; after being parked for more than 6 hours, a cold start is performed with the engine coolant temperature between 4°C and 35°C; the driving cycle with DMTL heating lasts for at least 600 seconds; the vehicle speed is equal to or higher than 40 km / h for at least 300 seconds; a driving cycle is performed with continuous idling for at least 30 seconds; the fuel tank level is between 15% and 85%; the ambient temperature is between 4°C and 35°C; and the altitude should be below 2500m.

[0018] In a preferred embodiment of the present invention, the first pipeline section, the second pipeline section, the third pipeline section, and the fuel tank are all located below the vehicle floor.

[0019] In a preferred embodiment of the present invention, a bypass pipeline is provided between the fuel tank and the fourth pipeline section, and a fuel filler port is provided on the bypass pipeline; a fuel tank isolation valve is provided between the connection between the bypass pipeline and the fourth pipeline section and the carbon canister.

[0020] The beneficial effects of this invention are: This invention is an improvement on the control strategy of the fuel system structure in the prior art. It requires no additional external components; only a reasonable design of a leak diagnosis strategy for the fuel system structure with a U-shaped segment structure is needed. This effectively expands the application scope of DMTL while ensuring the strength of the vehicle body structure. It should be noted that in the prior art... Figure 1 The fuel system structure shown is used to detect leaks in pipelines with U-shaped sections. However, when oil accumulates in the U-shaped section, the gas pumped by the DMTL may not be able to pass through it, leading to misjudgments by existing leak diagnosis strategies. Solving this technical problem is the premise of this invention. The presence of oil accumulation in the U-shaped section renders existing leak detection strategies inapplicable to fuel system structures with U-shaped sections unusable. This invention aims to solve this problem without adding any external components. By designing the height H in the U-shaped section pipeline, and allowing for a certain height of the U-shaped section, this invention reduces the impact on the vehicle body structure design. In existing technologies, eliminating the U-shaped section requires the pipeline to pass through longitudinal beams, necessitating drilling or cutting into the beams, which may affect the strength of the vehicle body structure. This invention effectively avoids these problems, achieving fuel system leak diagnosis while ensuring the strength of the vehicle body structure. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a fuel system in the prior art;

[0022] Figure 2 This is a schematic diagram of a fuel system leakage detection strategy in the prior art;

[0023] Figure 3 This is a schematic diagram of a U-shaped section pipeline structure for an optimized fuel system leak diagnosis method according to the present invention;

[0024] Figure 4 This is a schematic diagram of the fitting curve in S4 of the method for optimizing fuel system leak diagnosis according to the present invention;

[0025] Figure 5 This is a schematic diagram of the optimized leak detection strategy of the method for optimizing fuel system leak diagnosis according to the present invention;

[0026] Figure 6 This is a schematic diagram of an optimized driving cycle based on the method for diagnosing fuel system leaks according to the present invention.

[0027] In the diagram, 1-U-shaped section of pipeline; 2-Fuel tank; 3-Carbon canister; 4-DMTL; 5-Longitudinal beam of the vehicle body; 6-Standard leak hole; 7-Vehicle floor; 8-Bypass pipeline; 9-Fuel tank isolation valve; 11-First pipeline section; 12-Second pipeline section; 13-Third pipeline section; 14-Fourth pipeline section; 81-Fuel filler neck. Detailed Implementation

[0028] The technical solutions (including preferred technical solutions) of the present invention will be further described in detail below with reference to the accompanying drawings and by way of listing some optional embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] This invention discloses an optimized method for diagnosing fuel system leaks, which is based on Figure 1 The publicly disclosed improvements to the fuel system, due to Figure 1 When the publicly disclosed fuel system has a U-shaped section structure pipe 1, oil accumulates in the U-shaped section structure pipe 1, which means that the gas pumped out by the DMTL may not be able to pass through the U-shaped section structure pipe 1. Therefore, its continued use of... Figure 2The resulting strategy is: "If the DMTL current value reaches I1 after 300 seconds, there is no leakage; if the DMTL current value does not reach I1 after 300 seconds, there is leakage." However, this strategy may lead to a misjudgment. To eliminate the aforementioned misjudgments, this invention adjusts the diagnostic strategy based on the current hardware system, enabling leak diagnosis even for systems meeting a certain U-shaped section height. This invention is used for leak diagnosis of fuel systems including a U-shaped section structure pipeline 1. The U-shaped section structure pipeline 1 includes a first pipeline section 11, a second pipeline section 12, a third pipeline section 13, and a fourth pipeline section 14. The first pipeline section 11 and the fourth pipeline section 13 are arranged in parallel, as are the second pipeline section 12 and the fourth pipeline section 14. The first pipeline section 11 and the third pipeline section 13 are connected via the second pipeline section 12. The first pipeline section 11 connects to the fuel tank 2. One end of the fourth pipeline section 14 connects to the carbon canister 3, and the other end connects to the third pipeline section 13. The carbon canister 3 connects to a DMTL 4. The third pipeline section 13 is vertically positioned below the vehicle body longitudinal beam 5, and the first pipeline section 11 is vertically positioned to the side of the vehicle body longitudinal beam 5. The central axis of the first pipeline section 11 is perpendicular to... The distance between the central axes of the third pipeline section 13 is H, where H = P / ρ*g, P is the pressure generated by the DMTL when it operates at its maximum current Im, ρ is the gasoline density, and g is the acceleration due to gravity. The optimized steps for fuel system leak diagnosis include obtaining the DMTL current value I2 when there is oil accumulation in the U-shaped section pipeline 1 and the system leaks, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking in the system, and the time T2 required for the DMTL to reach the current I2 when there is no oil accumulation in the U-shaped section and the system has no leak. After the DMTL system triggers the diagnosis, the DMTL operates at the maximum allowable current Im for 10 seconds, and then the DMTL is turned on to balance the pressure inside the fuel tank with the external environment. The leak diagnosis begins. After 300 seconds, if the current value of the DMTL reaches I2, it is determined that the fuel system has no leak. After 300 seconds, if the current value of the DMTL does not reach I2, it is determined that the fuel system has a leak.

[0030] In a preferred embodiment of the present invention, leakage diagnosis is initiated. If the current value of DMTL reaches I2 after 300 seconds, it is determined that there is no leakage in the fuel system; if the current value of DMTL does not reach I2 after 300 seconds, it is determined that there is a leakage in the fuel system.

[0031] In a preferred embodiment of the present invention, the method for obtaining the DMTL current value I2 includes:

[0032] S1, When there is no gasoline in the U-shaped section pipe 1 and the system is not leaking, record the corresponding data of current and time during DMTL operation (use INCA to read the relevant data; INCA is an automotive calibration tool, a basic product under ETAS, which can interface with other test platforms, HIL systems, etc., and has comprehensive testing and calibration functions. It supports protocols such as CCP or XCP, can manage calibration data, and can be used for data acquisition, calibration, ECU flash programming ProF integration, and can be used with oscilloscopes with graphical strategy data display, interface self-programming, etc. It belongs to existing technology).

[0033] S2, fill the U-shaped section pipe 1 with gasoline, and DMTL operates at the maximum allowable current Im for 10 seconds to blow the gasoline into the fuel tank. Then, obtain the remaining amount of gasoline in the U-shaped section pipe 1 as Um.

[0034] S3, When there is no gasoline in the U-shaped section pipe 1 and the system is leaking, add the remaining oil Um from S2 into the U-shaped section pipe 1, and record the corresponding data of current and time when the DMTL is working (use INCA to read the relevant data; INCA is an automotive calibration tool, a basic product under ETAS, which can interface with other test platforms, HIL systems, etc., and has comprehensive testing and calibration functions. It supports protocols such as CCP or XCP, can manage calibration data, and can be used for data acquisition, calibration, ECU flash programming ProF integration, and can be used with oscilloscopes with graphical strategy data display, interface self-programming, etc. It belongs to existing technology).

[0035] S4. Plot the DMTL current and time data obtained from S1-S3 into a rectangular coordinate system to obtain a fitted curve. The horizontal axis represents time and the vertical axis represents current. Based on the fitted curve, obtain I2. I2 is the DMTL current value when there is oil accumulation in U-shaped section pipe 1 and system leakage, and the gas generated by DMTL reaches pressure balance with the gas leaking from the system. T2 is the time required for DMTL to reach current I2 when there is no oil accumulation in U-shaped section and no system leakage.

[0036] In a preferred embodiment of the present invention, in S3, the method for realizing system leakage includes installing a standard leak hole 6 on the first pipeline section 11.

[0037] In a preferred embodiment of the invention, the standard leak hole 6 is located near the connection between the first pipeline section 11 and the oil tank 2.

[0038] In a preferred embodiment of the present invention, the first pipeline section 11, the second pipeline section 12, the third pipeline section 13, and the fuel tank 2 are all located below the vehicle floor 7.

[0039] In a preferred embodiment of the present invention, I2 is the DMTL current value corresponding to the condition where there is oil accumulation in the U-shaped section of the pipeline 1, the system leaks, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking from the leak hole.

[0040] In a preferred embodiment of the present invention, the conditions for triggering diagnosis in the DMTL system include:

[0041] The test vehicle completes one driving cycle and is then parked and turned off; after being parked for more than 6 hours, a cold start is performed with the engine coolant temperature between 4°C and 35°C; the driving cycle with DMTL heating lasts for at least 600 seconds; the vehicle speed is equal to or higher than 40 km / h for at least 300 seconds; a driving cycle is performed with continuous idling for at least 30 seconds; the fuel tank level is between 15% and 85%; the ambient temperature is between 4°C and 35°C; and the altitude should be below 2500m.

[0042] In a preferred embodiment of the present invention, the first pipeline section 11, the second pipeline section 12, the third pipeline section 13, and the fuel tank 2 are all located below the vehicle floor 7.

[0043] In a preferred embodiment of the present invention, a bypass pipe 8 is provided between the fuel tank 2 and the fourth pipeline section 14, and a fuel filler port 81 is provided on the bypass pipe 8; a fuel tank isolation valve 9 is provided between the connection between the bypass pipe 8 and the fourth pipeline section 14 and the carbon canister 3.

[0044] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, combinations, substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for optimizing fuel system leak diagnosis, characterized in that: It is used for leak diagnosis of a fuel system including a U-shaped section structure pipeline (1), the U-shaped section structure pipeline (1) including a first pipeline section (11), a second pipeline section (12), a third pipeline section (13) and a fourth pipeline section (14), the first pipeline section (11) and the third pipeline section (13) being arranged in parallel, the second pipeline section (12) and the fourth pipeline section (14) being arranged in parallel, the first pipeline section (11) and the third pipeline section (13) being connected through the second pipeline section (12), the first pipeline section (11) being connected to the fuel tank (2), the fourth pipeline section (14) being connected to the fuel tank (2) and ... One end of the pipeline (14) is connected to the carbon canister (3), and the other end is connected to the third pipeline (13). The carbon canister (3) is connected to the DMTL (4). The third pipeline (13) is vertically positioned below the longitudinal beam of the vehicle body (5). The first pipeline (11) is vertically positioned to the side of the longitudinal beam of the vehicle body (5). The distance between the central axis of the first pipeline (11) and the central axis of the third pipeline (13) is H, where H = P / ρ*g, P is the pressure generated by the DMTL when it operates at the maximum current Im, ρ is the gasoline density, and g is the acceleration due to gravity. The optimization steps for fuel system leak diagnosis include... Obtain the DMTL current value I2 when the U-shaped section of the pipeline has oil accumulation and system leakage, and the gas generated by the DMTL reaches pressure equilibrium with the gas leaking from the system, and the time T required for the DMTL to reach current I2 when there is no oil accumulation in the U-shaped section and no system leakage. 2； After the DMTL system triggers the diagnostic, the DMTL operates at the maximum allowable current Im for 10 seconds, and then the DMTL is turned on to balance the pressure inside the fuel tank with the external pressure. Leak diagnosis begins. After 300 seconds, if the current value of the DMTL reaches I2, it is determined that there is no leak in the fuel system. If the current value of the DMTL does not reach I2, it is determined that there is a leak in the fuel system. Methods for obtaining the DMTL current value I2 include: S1, When there is no gasoline in the U-shaped section pipeline (1) and the system is not leaking, record the corresponding data of current and time when the DMTL is working; S2, fill the U-shaped section pipe (1) with gasoline, DMTL works at the maximum allowable current Im for 10s, blow the gasoline into the fuel tank, and obtain the remaining amount of oil in the U-shaped section pipe (1) as Um; S3, When there is no gasoline in the U-shaped section pipe (1) and the system is leaking, add the remaining oil Um from S2 into the U-shaped section pipe (1) and record the corresponding data of current and time when DMTL is working; S4. Plot the DMTL current and time data obtained from S1-S3 into a rectangular coordinate system to obtain the fitting curve. The horizontal axis is time and the vertical axis is current. Based on the fitting curve, obtain I2. I2 is the DMTL current value when there is oil accumulation in the U-shaped section pipeline (1) and the system leaks and the gas generated by DMTL reaches pressure balance with the gas leaked in the system. T2 is the time required for DMTL to reach current I2 when there is no oil accumulation in the U-shaped section and no leakage in the system.

2. The method for optimizing fuel system leak diagnosis according to claim 1, characterized in that: In S3, the method of realizing system leakage includes installing a standard leak hole (6) on the first pipeline section (11).

3. The method for optimizing fuel system leak diagnosis according to claim 2, characterized in that: The standard leak hole (6) is located near the connection between the first pipeline section (11) and the oil tank (2).

4. The method for optimizing fuel system leak diagnosis according to claim 2, characterized in that: The first pipeline section (11), the second pipeline section (12), the third pipeline section (13), and the fuel tank (2) are all located below the vehicle floor (7).

5. The method for optimizing fuel system leak diagnosis according to claim 1, characterized in that: The first pipeline section (11), the second pipeline section (12), the third pipeline section (13), and the fuel tank (2) are all located below the vehicle floor (7).

6. The method for optimizing fuel system leak diagnosis according to claim 1, characterized in that: The oil tank (2) and the fourth pipeline section (14) are connected by a bypass pipeline (8), and the bypass pipeline (8) is provided with a filling port (81); an oil tank isolation valve (9) is provided between the connection between the bypass pipeline (8) and the fourth pipeline section (14) and the carbon canister (3).

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