A system and method for fuel vapor system leak detection

Abstract

The application discloses a system for fuel evaporation system leakage detection, and belongs to the technical field of oil and gas leakage detection.The system comprises an electric control module, a pressure pump, a pressure sensor group and a gasoline volatile gas sensor.An oil tank is communicated with a carbon can through a first pipeline, and the carbon can is communicated with the pressure pump through a second pipeline.The pressure sensor group, the volatile gas sensor and the pressure pump are electrically connected with the electric control module.The gasoline volatile gas sensor signal is fitted with the pressure sensor group signal, so that the detection precision and the detection frequency of the fuel evaporation system leakage detection are improved.A standard leakage hole is arranged, and the electric control module is used for fitting the pressure change signal curve and comparing the pressure change curve with that of the standard leakage hole, so that the diameter of the leakage hole is accurately determined.The fuel evaporation system is divided into different module parts through a valve, and the position of the leakage hole is quickly detected and judged through the sensor, so that too many devices are not needed, and cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas leak detection technology, specifically relating to a system and method for detecting leaks in fuel evaporation systems. Background Technology

[0002] GB18352.6-2016, "Limits and Measurement Methods for Pollutant Emissions from Light-Duty Vehicles (China Stage VI)," specifies requirements for leak diagnosis in automotive fuel evaporation systems, demanding that on-board diagnostic systems be capable of detecting leaks larger than or equal to 1 mm in the fuel evaporation system. Currently used on-board vapor recovery systems (ORVR) can recover 98% of fuel vapor generated during refueling, driving, and parking. If a leak exists in the fuel evaporation system, evaporated pollutants will overflow from the leak, significantly reducing the ORVR's recovery efficiency. Therefore, it is necessary to test the airtightness of the automotive fuel evaporation system.

[0003] Currently, positive pressure and negative pressure methods are mainly used for fuel system leak detection. However, many factors affect the pressure inside the fuel tank, such as temperature, fuel level, and fuel sloshing. Relying solely on pressure changes cannot accurately determine the condition of a fuel tank leak. The biggest advantage of the positive pressure method is its clear signal, short detection time, and ability to detect tiny pores with high accuracy. However, pressurizing the fuel tank accelerates the emission of gasoline vapor into the atmosphere, causing pollution and resource waste. The advantage of the negative pressure method is that the pressure inside the system is always lower than atmospheric pressure, preventing additional fuel vapor emissions. Utilizing the vacuum at the engine intake manifold to create negative pressure is economical. However, when evacuating the fuel tank, gasoline evaporation causes a decrease in vacuum, which can lead to false positives for detecting extremely small pores.

[0004] Chinese patent CN112228217A discloses an on-board diagnostic device and method for monitoring fuel evaporation leaks in automobiles. The method uses a distance intersection algorithm based on the acoustic intensity of the leak hole and a pressurization method to determine the location and size of the leak hole. However, this method requires the installation of 11 ultrasonic sensors, which is expensive and not suitable for practical applications.

[0005] Chinese patent CN107152354A discloses a vehicle fuel evaporation system leak diagnosis device and method. This method uses an oxygen sensor to detect the air-fuel ratio signal in the fuel tank to correct the tank pressure, thereby determining the presence of a leak. However, this method has low detection accuracy and cannot accurately determine the diameter and location of the leak.

[0006] Chinese patent CN110657926A describes a fuel evaporation system leak detection device and method. The device pressurizes the system with an electric pump, maintains the pressure at saturation for 30 seconds, and then compares it with a preset pressure to determine if there is a leak. The device then outputs colored smoke to indicate the location of the leak. However, this detection method is only suitable for use in repair shops. Summary of the Invention

[0007] Technical Problem: In view of the above-mentioned problems existing in the prior art, the technical problem to be solved by the present invention is to provide a system for detecting leaks in a fuel evaporation system to reduce interference factors during leak detection, and to provide a detection method to quickly determine whether there are leaks in the fuel evaporation system, thereby improving detection accuracy and shortening detection time.

[0008] Technical Solution: To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A system for detecting leaks in a fuel evaporation system includes an electronic control module, a pressure pump for pressurizing a fuel tank and a carbon canister, a pressure sensor group for detecting the pressure within the fuel evaporation system, and a gasoline volatile gas sensor disposed in the fuel tank. The fuel tank is connected to the carbon canister via a first pipeline, and the carbon canister is connected to the pressure pump via a second pipeline. The pressure sensor group, the volatile gas sensor, and the pressure pump are all electrically connected to the electronic control module.

[0010] Preferably, the device further includes a discrimination device for determining the leakage orifice diameter. The discrimination device includes a first discrimination pipeline and a second discrimination pipeline connected in parallel. The first discrimination pipeline and the second discrimination pipeline are connected in parallel and communicate with the first pipeline. The first discrimination pipeline is provided with a first standard leakage orifice, and the second discrimination pipeline is provided with a second standard leakage orifice. The first discrimination pipeline is provided with a sixth valve, and the second discrimination pipeline is provided with a seventh valve. Both the sixth valve and the seventh valve are electrically connected to the electronic control module.

[0011] Preferably, the first pipeline is provided with a first valve and a second valve, the second pipeline is provided with a fourth valve and a fifth valve, and the pressure sensor group includes a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor. The first pressure sensor is disposed on the oil tank, the second pressure sensor is disposed on the pipeline between the first valve and the second valve, the third pressure sensor is disposed on the pipeline between the second valve and the fourth valve, and the fourth pressure sensor is disposed on the pipeline between the fourth valve and the fifth valve. The first valve, the second valve, the fourth valve, and the fifth valve are all electrically connected to the electronic control module.

[0012] Preferably, the first standard leakage hole is a 0.5mm standard leakage hole, and the second standard leakage hole is a 1mm standard leakage hole.

[0013] Preferably, the carbon canister is provided with a third pipeline, and the third pipeline is provided with a third valve.

[0014] The present invention also provides a method for detecting leaks in a fuel evaporation system, applied to the aforementioned system for detecting leaks in a fuel evaporation system, comprising the following steps:

[0015] Step 1: Determine if the fuel evaporation system pipes are broken and if the fuel tank cap is tightened.

[0016] Close the fuel evaporation system and external channels, pressurize the fuel evaporation system, and after a period of time, collect the average pressure value inside the fuel evaporation system. If the average pressure value is greater than the preset value, the fuel evaporation system pipe has not broken and the fuel tank cap is tightened; otherwise, the fuel evaporation system pipe has broken or the fuel tank cap is not tightened.

[0017] Step 2: Determine if there are any leaks in the fuel evaporation system;

[0018] The fuel evaporation system is pressurized and pressurized again. After a period of time, the fuel evaporation system is closed from the external channel and the system is sealed for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain the fitted pressure change curve. The fitted pressure change curve is compared with the preset pressure change curve without leakage hole to determine whether there is a leakage hole in the fuel evaporation system.

[0019] Step 3: Determine the diameter of the leak hole;

[0020] After determining the presence of a leak, the fuel evaporation system is pressurized until saturation pressure is reached. Then, the fuel evaporation system is shut off from the external channel, and the second standard leak channel is connected for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain a fitted pressure change curve. The fitted pressure change curve is compared with the preset second standard leak pressure change curve. If the attenuation slope of the fitted pressure change curve is greater than or equal to the attenuation slope of the preset second standard leak pressure change curve, then the fuel evaporation system has a leak larger than the second standard leak; otherwise, the fuel evaporation system has a leak smaller than the second standard leak.

[0021] After determining that there is a leak in the fuel evaporation system smaller than the second standard leak hole, the fuel evaporation system is pressurized until saturation pressure is reached. Then, the fuel evaporation system is closed from the external channel, and the first standard leak hole channel is connected for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain a fitted pressure change curve. The fitted pressure change curve is compared with the preset first standard leak hole pressure change curve. If the attenuation slope of the fitted pressure change curve is greater than or equal to the attenuation slope of the preset first standard leak hole pressure change curve, then there is a leak in the fuel evaporation system that is larger than the first standard leak hole and smaller than the second standard leak hole; otherwise, there is a leak in the fuel evaporation system that is smaller than the first standard leak hole.

[0022] Step 4: Determine the location of the leak hole;

[0023] After determining the diameter of the leak hole in the fuel evaporation system, the pressure inside the fuel evaporation system is increased to a preset value. The valves between multiple parts of the fuel evaporation system are closed, and the pressure changes in different parts are detected. If the pressure drop in one part exceeds the preset standard, then there is a leak hole in that part; otherwise, there is no leak hole in that part.

[0024] Preferably, step 1 includes the following steps:

[0025] Step 1.1: The electrical control module opens the first valve, the second valve, the fourth valve, and the fifth valve, and closes the third valve, the sixth valve, and the seventh valve;

[0026] Step 1.2: Simultaneously start the pressure pump. After time t1, collect the signals p from the four pressure sensors in the pressure sensor group. 01 p 02 p 03 and p 04 ;

[0027] Step 1.3: Calculate the average value of the pressure values ​​from the four sensors, p0 = (p 01 +p 02 +p 03 +p 04 ) / 4, mix p0 with atmospheric pressure p 00 Compare with the preset pressure threshold x; if p0 ≥ p 00 +x indicates that the fuel evaporation system pipe is not broken and the fuel tank cap is tightened; otherwise, the fuel evaporation system pipe is broken or the fuel tank cap is not tightened.

[0028] Preferably, step 2 includes the following steps:

[0029] Step 2.1: The pressure pump continues to operate, pressurizing the fuel evaporation system until the system reaches its saturation pressure P after time t2.m1 Then, the pressure pump stopped working;

[0030] Step 2.2: Control the fifth valve to close. At this time, the fuel evaporation system is a sealed system. Seal the system for a period of time t3, t3 = 30s.

[0031] Step 2.3: The electronic control module receives the signals p from the four pressure sensors in the pressure sensor group during this time period. 11 p 12 p 13 and p 14 The pressure change curve h1 is obtained by fitting the signal C1 from the gasoline volatile gas sensor, where h1 = f(p 11 p 12 p 13 p 14 C1);

[0032] Step 2.4: Calculate the pressure change curve h of the preset leak-free orifice. 11 The data is stored in the electronic control module. If the detected fitted pressure change curve h1 is within the preset leak-free orifice pressure change curve h... 11 If the fuel vaporization system is located below the center, there is a leak hole; otherwise, it is not.

[0033] Preferably, step 3 includes the following steps:

[0034] Step 3.1: After determining the presence of a leak, continue pressurizing the fuel evaporation system until the saturation pressure P is reached. m1 Then, close the fifth valve and open the seventh valve.

[0035] Step 3.2, the four pressure signals p detected by the pressure sensor group (1) 21 p 22 p 23 p 24 The gasoline volatile gas sensor detects signal C2 and feeds it back to the electronic control module. This process lasts for 30 seconds.

[0036] Step 3.3: The electronic control module (7) fits the received signal to obtain the fitted pressure change curve h2, h2=f(p 21 p 22 p 23 p 24 C2); h2 and the pressure change curve with a preset 1mm standard leakage hole h 22 For comparison, if the attenuation slope k2 of h2 is greater than or equal to h... 22 The attenuation slope k 22 If the fuel vaporization system has a leakage hole larger than 1 mm, it is twice the size of the fuel vaporization system; otherwise, it has a leakage hole smaller than 1 mm.

[0037] Step 3.4: After determining that there is a leak hole smaller than 1mm, continue to pressurize the fuel evaporation system until the saturation pressure p is reached. m1 Then, close the fifth valve and open the sixth valve;

[0038] Step 3.5: The four pressure signals p detected by the pressure sensor group 31 p 32 p 33 p 34 The gasoline volatile gas sensor detects signal C3 and feeds it back to the electronic control module. This process lasts for 30 seconds.

[0039] Step 3.6: The electronic control module fits the received signal to obtain the fitted pressure change curve h3, h3 = f(p 31 p 32 p 33 p 34 The pressure change curves h3 and h3 with a preset 0.5mm standard leakage hole are shown. 33 For comparison, if the attenuation slope k3 of h3 is greater than or equal to h... 33 The attenuation slope k 33 If the diameter is twice that of the fuel evaporation system, then there is a leak hole larger than 0.5 mm but less than 1 mm; conversely, if the diameter is less than that of the fuel evaporation system, then there is a leak hole smaller than 0.5 mm.

[0040] Preferably, step 4 includes the following steps:

[0041] Step 4.1: After determining the diameter of the system leak hole, acquire the signals P from the four pressure sensors. 41 P 42 P 43 and P 44 Calculate the average value p of the pressure values ​​from its four sensors. n =(P 41 +P 42 +P 43 +P 44 ) / 4. (P) n With preset pressure value P nn For comparison, if P n ≥P nn If P n <P nn Then the fuel evaporation system is pressurized until the fuel evaporation system pressure reaches P. nn Then, the pressure pump stopped working;

[0042] Step 4.2: Close all valves. The fuel evaporation system is divided into different modules: fuel tank module, first pipeline module, carbon canister module, and second pipeline module.

[0043] Step 4.3: Detect the pressure change within the module using pressure sensors installed in different module sections. If the pressure drop of the module exceeds the preset standard, then the module has a leak; otherwise, there is no leak, and the electronic control module displays a fault on the instrument panel.

[0044] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. By setting a gasoline volatile gas sensor, the signal of the gasoline volatile gas sensor is fitted with the signal of the pressure sensor group, reducing interference factors during leak detection, eliminating the need to consider fuel level and temperature, and improving the detection accuracy and frequency of leak detection in the fuel evaporation system; 2. By setting a standard leak hole, the pressure change signal curve is fitted using the electronic control module and compared with the pressure change curve of the standard leak hole to accurately determine the diameter of the leak hole; 3. By dividing the fuel evaporation system into different modular parts through valves, the location of the leak hole can be quickly detected and determined by sensors, eliminating the need to install too many devices and saving costs. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of the present invention;

[0046] Figure 2 This is a pressure change curve during the leak diagnosis process of this invention;

[0047] Figure 3 This is a flowchart of the leakage diagnosis method of the present invention. Detailed Implementation

[0048] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0049] like Figure 1As shown, a system for detecting leaks in a fuel evaporation system includes an electronic control module 7, a pressure pump 4, a pressure sensor group 1, a gasoline volatile gas sensor 3, and a discrimination device 5. The pressure pump 4 is a pneumatic diaphragm pump located near the engine intake manifold. It utilizes the vacuum at this location to drive the pneumatic diaphragm pump, thereby establishing positive pressure in the fuel evaporation system. The pressure pump 4 is electrically connected to the electronic control module 7, which controls the operation of the pressure pump 4. The pressure pump 4 is connected to a carbon canister 8 via a second pipe 42, and the fuel tank 6 is connected to the carbon canister 8 via a first pipe 41. The gasoline volatile gas sensor 3 is installed inside the fuel tank 6. This semiconductor-type gasoline volatile gas sensor detects changes in the concentration of gasoline vapors in the fuel tank during fuel evaporation system leak detection. The volatile gas sensor 3 is electrically connected to the electronic control module 7 and is used to... The gas concentration change signal is sent to the electronic control module 7; the discrimination device 5 includes a first discrimination pipeline and a second discrimination pipeline connected in parallel. The first discrimination pipeline and the second discrimination pipeline are connected in parallel and connected to the first pipeline 41. The first discrimination pipeline is provided with a first standard leakage hole 501, which is a 0.5mm standard leakage hole. The second discrimination pipeline is provided with a second standard leakage hole 502, which is a 1mm standard leakage hole. The first discrimination pipeline is provided with a sixth valve 206, which is used to control the connection and disconnection between the 0.5mm standard leakage hole and the first pipeline 41. The second discrimination pipeline is provided with a seventh valve 207, which is used to control the connection and disconnection between the 1mm standard leakage hole and the first pipeline 41. The sixth valve 206 and the seventh valve 207 are both electrically connected to the electronic control module 7, and the electronic control module 7 controls the operation of the two valves.

[0050] The first pipeline 41 is equipped with a first valve 201 and a second valve 202. The first valve 201 is located at the end of the first pipeline 41 near the oil tank 6, and the second valve 202 is located at the end of the first pipeline 41 near the carbon canister 8. The second pipeline 42 is equipped with a fourth valve 204 and a fifth valve 205. The fourth valve 204 is located at the end of the second pipeline 42 near the carbon canister 8, and the fifth valve 205 is located at the end of the second pipeline 42 near the pressure pump 4. The carbon canister 8 is equipped with a third pipeline, on which a third valve 203 is located. The first valve 201 and the second valve 202... 2. The third valve 203, the fourth valve 204, and the fifth valve 205 are all electrically connected to the electronic control module 7. The electronic control module 7 controls the operation of these valves. When the electronic control module 7 controls all valves to be closed, the fuel evaporation system is divided into multiple parts. The section from the fuel tank 6 to the first valve 201 is the fuel tank module section. The section from the first valve 201 to the second valve 202 is the first pipeline module section. The section from the second valve 202 to the carbon canister 8 and from the fourth valve 204 to the carbon canister 8 is the carbon canister module section. The section from the fourth valve 204 to the fifth valve 205 is the second pipeline module section.

[0051] The pressure sensor group 1 includes a first pressure sensor 101, a second pressure sensor 102, a third pressure sensor 103, and a fourth pressure sensor 104. The first pressure sensor 101 is installed on the inner wall of the fuel tank 6 and is used to detect pressure changes in the fuel tank 6. The second pressure sensor 102 is installed on the first pipeline 41 and is located between the first valve 201 and the second valve 202. The third pressure sensor 103 is installed on the second pipeline 42 and is located between the fourth valve 204 and the carbon canister 8 (the third pressure sensor 103 can also be installed inside the carbon canister 8). The fourth pressure sensor 104 is installed on the pipeline between the fourth valve 204 and the fifth valve 205. The pressure sensor group 1 is used to detect pressure changes in the fuel evaporation system. The pressure sensor group 1 is electrically connected to the electronic control module 7 and sends pressure signals to the electronic control module 7.

[0052] The electronic control module 7 can be a separate ECU module or an engine control unit module. It is used to receive signals from the pressure sensor group and the gasoline volatile gas sensor, to control the opening and closing of all valves in the system, to control whether the pressure pump is working, and to determine whether there is a leak and the location and size of the leak.

[0053] like Figure 2 and Figure 3 As shown, this embodiment also provides a method for detecting leaks in a fuel evaporation system, applied to the aforementioned system for detecting leaks in a fuel evaporation system, including the following steps:

[0054] Step 1: Determine if the fuel evaporation system pipes are broken and if the fuel tank cap is tightened. This includes:

[0055] Step 1.1: The electrical control module 7 opens the first valve 201, the second valve 202, the fourth valve 204, and the fifth valve 205, and closes the third valve 203, the sixth valve 206, and the seventh valve 207.

[0056] Step 1.2: Simultaneously start pressure pump 4. After time t1, collect the signals p from the four pressure sensors in pressure sensor group 1. 01 p 02 p 03 and p 04 .

[0057] Step 1.3: Calculate the average value of the pressure values ​​from the four sensors, p0 = (p 01 +p 02 +p 03 +p 04 ) / 4, mix p0 with atmospheric pressure p 00 Compare with the preset pressure threshold x; if p0 ≥ p 00+x indicates that the fuel evaporation system pipe is not broken and the fuel tank cap is tightened; otherwise, the fuel evaporation system pipe is broken or the fuel tank cap is not tightened.

[0058] Step 2: Determine if there are any leaks in the fuel evaporation system, specifically including:

[0059] Step 2.1: Pressure pump 4 continues to operate, pressurizing the fuel evaporation system until the system reaches saturation pressure P after time t2. m1 After that, pressure pump 4 stopped working.

[0060] Step 2.2: Control the fifth valve 205 to close. At this time, the fuel evaporation system is a sealed system. The system is sealed for a period of time t3, t3 = 30s.

[0061] Step 2.3: The electronic control module 7 receives the signals p from the four pressure sensors in pressure sensor group 1 during this time period. 11 p 12 p 13 and p 14 The pressure change curve h1 is obtained by fitting the signal C1 from the gasoline volatile gas sensor, where h1 = f(p 11 p 12 p 13 p 14 C1).

[0062] Step 2.4: Calculate the pressure change curve h of the preset leak-free orifice. 11 The data is stored in the electronic control module. If the detected fitted pressure change curve h1 is within the preset leak-free orifice pressure change curve h... 11 If the fuel vaporization system is located below the center, there is a leak hole; otherwise, it is not.

[0063] Step 3: Determine the diameter of the leak hole, specifically including:

[0064] Step 3.1: After determining the presence of a leak, continue pressurizing the fuel evaporation system until the saturation pressure P is reached. m1 Then, close the fifth valve 205 and open the seventh valve 207.

[0065] Step 3.2, the four pressure signals p detected by pressure sensor group 1 21 p 22 p 23 and p 24 The gasoline volatile gas sensor detects signal C2 and feeds it back to the electronic control module. This process lasts for 30 seconds.

[0066] Step 3.3: The electronic control module 7 fits the received signal to obtain the fitted pressure change curve h2, h2 = f(p 21p 22 p 23 p 24 C2); h2 and the pressure change curve with a preset 1mm standard leakage hole h 22 For comparison, if the attenuation slope k2 of h2 is greater than or equal to h... 22 The attenuation slope k 22 If the pressure is twice that of the fuel evaporation system, then there is a leak hole larger than 1 mm; conversely, if the pressure is less than that of the fuel evaporation system, then there is a leak hole smaller than 1 mm. The attenuation slope can be calculated from the end point and the beginning point of the attenuation stage of the pressure change curve. The starting point coordinates are (X1, Y1), and the ending point coordinates are (X2, Y2). The attenuation slope is the absolute value of (Y2-Y1) / (X2-X1).

[0067] Step 3.4: After determining that there is a leak hole smaller than 1mm, continue to pressurize the fuel evaporation system until the saturation pressure p is reached. m1 Then, close the fifth valve 205 and open the sixth valve 206.

[0068] Step 3.5: The four pressure signals p detected by pressure sensor group 1 31 p 32 p 33 and p 34 The gasoline volatile gas sensor 3 detects signal C3 and feeds it back to the electronic control module. This process lasts for 30 seconds.

[0069] Step 3.6: The electronic control module 7 fits the received signal to obtain the fitted pressure change curve h3, h3 = f(p 31 p 32 p 33 p 34 The pressure change curves h3 and h3 with a preset 0.5mm standard leakage hole are shown. 33 For comparison, if the attenuation slope k3 of h3 is greater than or equal to h... 33 The attenuation slope k 33 If the diameter is twice that of the fuel evaporation system, then there is a leak hole larger than 0.5 mm but less than 1 mm; conversely, if the diameter is less than that of the fuel evaporation system, then there is a leak hole smaller than 0.5 mm.

[0070] Step 4: Determine the location of the leak, specifically including:

[0071] Step 4.1: After determining the diameter of the system leak hole, acquire the signals P from the four pressure sensors. 41 P 42 P 43 and P 44 Calculate the average value p of the pressure values ​​from its four sensors. n (P 41 +P42 +P 43 +P 44 ) / 4. (P) n With preset pressure value P nn For comparison, if P n ≥P nn If P n <P nn Then the fuel evaporation system is pressurized until the fuel evaporation system pressure reaches P. nn After that, the pressure pump (4) stopped working.

[0072] Step 4.2: Close all valves. The fuel evaporation system is divided into different modules: fuel tank module, first pipeline module, carbon canister module, and second pipeline module.

[0073] Step 4.3: The pressure changes within each module are detected using pressure sensors installed in different modules. The first pressure sensor 101 detects the pressure changes in the fuel tank module, the second pressure sensor 102 detects the pressure changes in the first pipeline module, the third pressure sensor 103 detects the pressure changes in the carbon canister module, and the fourth pressure sensor 104 detects the pressure changes in the second pipeline module. If the pressure drop detected by any of the pressure sensors exceeds a preset standard, then the module corresponding to that pressure sensor has a leak; otherwise, there is no leak, and the electronic control module 7 displays a fault on the instrument panel.

[0074] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting leaks in a fuel evaporation system, and a system for detecting leaks in a fuel evaporation system, characterized in that, The fuel evaporation system leak detection system includes an electronic control module (7), a pressure pump (4) for pressurizing the fuel tank (6) and carbon canister (8), a pressure sensor group (1) for detecting the pressure in the fuel evaporation system, and a gasoline volatile gas sensor (3) installed in the fuel tank (6). The fuel tank (6) is connected to the carbon canister (8) through a first pipeline (41), and the carbon canister (8) is connected to the pressure pump (4) through a second pipeline (42). The pressure sensor group (1), the volatile gas sensor (3), and the pressure pump (4) are all electrically connected to the electronic control module (7). The system for detecting leaks in the fuel evaporation system also includes a discrimination device (5) for determining the leak hole diameter. The discrimination device (5) includes a first discrimination pipeline and a second discrimination pipeline connected in parallel. The first discrimination pipeline and the second discrimination pipeline are connected in parallel and connected to the first pipeline (41). The first discrimination pipeline is provided with a first standard leak hole (501), and the second discrimination pipeline is provided with a second standard leak hole (502). The first discrimination pipeline is provided with a sixth valve (206), and the second discrimination pipeline is provided with a seventh valve (207). The sixth valve (206) and the seventh valve (207) are both electrically connected to the electronic control module (7). The first pipeline (41) is provided with a first valve (201) and a second valve (202), and the second pipeline (42) is provided with a fourth valve (204) and a fifth valve (205). The pressure sensor group (1) includes a first pressure sensor (101), a second pressure sensor (102), a third pressure sensor (103), and a fourth pressure sensor (104). The first pressure sensor (101) is installed on the oil tank (6), the second pressure sensor (102) is installed on the pipeline between the first valve (201) and the second valve (202), the third pressure sensor (103) is installed on the pipeline between the second valve (202) and the fourth valve (204), and the fourth pressure sensor (104) is installed on the pipeline between the fourth valve (204) and the fifth valve (205). The first valve (201), the second valve (202), the fourth valve (204), and the fifth valve (205) are all electrically connected to the electronic control module (7). The first standard leakage hole (501) is a 0.5mm standard leakage hole, and the second standard leakage hole (502) is a 1mm standard leakage hole; The carbon canister (8) is provided with a third pipeline, and the third pipeline is provided with a third valve (203). The leakage detection method includes the following steps: Step 1: Determine if the fuel evaporation system pipes are broken and if the fuel tank cap is tightened. Close the fuel evaporation system and external channels, pressurize the fuel evaporation system, and after a period of time, collect the average pressure value inside the fuel evaporation system. If the average pressure value is greater than the preset value, the fuel evaporation system pipe has not broken and the fuel tank cap is tightened; otherwise, the fuel evaporation system pipe has broken or the fuel tank cap is not tightened. Step 2: Determine if there are any leaks in the fuel evaporation system; The fuel evaporation system is pressurized and pressurized again. After a period of time, the fuel evaporation system is closed from the external channel and the system is sealed for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain the fitted pressure change curve. The fitted pressure change curve is compared with the preset pressure change curve without leakage hole to determine whether there is a leakage hole in the fuel evaporation system. Step 3: Determine the diameter of the leak hole; After determining the presence of a leak, the fuel evaporation system is pressurized until saturation pressure is reached. Then, the fuel evaporation system is shut off from the external channel, and the second standard leak channel is connected for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain a fitted pressure change curve. The fitted pressure change curve is compared with the preset second standard leak pressure change curve. If the attenuation slope of the fitted pressure change curve is greater than or equal to the attenuation slope of the preset second standard leak pressure change curve, then the fuel evaporation system has a leak larger than the second standard leak; otherwise, the fuel evaporation system has a leak smaller than the second standard leak. After determining that there is a leak in the fuel evaporation system smaller than the second standard leak hole, the fuel evaporation system is pressurized until saturation pressure is reached. Then, the fuel evaporation system is closed from the external channel, and the first standard leak hole channel is connected for a period of time. The pressure signal of the fuel evaporation system and the gasoline evaporation signal in the fuel tank are fitted to obtain a fitted pressure change curve. The fitted pressure change curve is compared with the preset first standard leak hole pressure change curve. If the attenuation slope of the fitted pressure change curve is greater than or equal to the attenuation slope of the preset first standard leak hole pressure change curve, then there is a leak in the fuel evaporation system that is larger than the first standard leak hole and smaller than the second standard leak hole; otherwise, there is a leak in the fuel evaporation system that is smaller than the first standard leak hole. Step 4: Determine the location of the leak hole; After determining the diameter of the leak hole in the fuel evaporation system, the pressure inside the fuel evaporation system is increased to a preset value. The valves between multiple parts of the fuel evaporation system are closed, and the pressure changes in different parts are detected. If the pressure drop in one part exceeds the preset standard, then there is a leak hole in that part; otherwise, there is no leak hole in that part.

2. The method for detecting leaks in a fuel evaporation system according to claim 1, characterized in that, Step 1 includes the following steps: Step 1.1: The electrical control module (7) opens the first valve (201), the second valve (202), the fourth valve (204), and the fifth valve (205), and closes the third valve (203), the sixth valve (206), and the seventh valve (207); Step 1.2: Simultaneously start the pressure pump (4), and after time t1, collect the signals p from the four pressure sensors of the pressure sensor group (1). 01 p 02 p 03 and p 04 ; Step 1.3: Calculate the average value p0 of the pressure values ​​from the four sensors. 01 +p 02 +p 03 +p 04 ) / 4, mix p0 with atmospheric pressure p 00 Compare with the preset pressure threshold x; if p0 ≥ p 00 +x indicates that the fuel evaporation system pipe is not broken and the fuel tank cap is tightened; otherwise, the fuel evaporation system pipe is broken or the fuel tank cap is not tightened.

3. The method for detecting leaks in a fuel evaporation system according to claim 1, characterized in that, Step 2 includes the following steps: Step 2.1: Pressure pump (4) continues to work, pressurizing the fuel evaporation system. After time t2, the system reaches its saturation pressure P. m1 Afterwards, the pressure pump (4) stopped working; Step 2.2: Control the fifth valve (205) to close. At this time, the fuel evaporation system is a sealed system. The system is sealed for a period of time t3, t3=30s. Step 2.3: The electronic control module (7) receives the signals p from the four pressure sensors in the pressure sensor group (1) during this time period. 11 p 12 p 13 and p 14 The pressure change curve h1 is obtained by fitting the signal C1 from the gasoline volatile gas sensor, where h1 = f(p) 11 p 12 p 13 p 14 (C1) Step 2.4: Calculate the pressure change curve h of the preset leak-free orifice. 11 The data is stored in the electronic control module. If the detected fitted pressure change curve h1 is within the preset leak-free orifice pressure change curve h... 11 If the fuel vaporization system is located below the center, there is a leak hole; otherwise, it is not.

4. The method for detecting leaks in a fuel evaporation system according to claim 1, characterized in that, Step 3 includes the following steps: Step 3.1: After determining the presence of a leak, continue pressurizing the fuel evaporation system until the saturation pressure P is reached. m1 Then, close the fifth valve (205) and open the seventh valve (207). Step 3.2, the four pressure signals p detected by the pressure sensor group (1) 21 p 22 p 23 p 24 The gasoline volatile gas sensor detects signal C2 and feeds it back to the electronic control module. This process lasts for 30 seconds. Step 3.3: The electronic control module (7) fits the received signal to obtain the fitted pressure change curve h2, h2=f(p 21 p 22 p 23 p 24 (C2); h2 and the pressure change curve with a preset 1mm standard leakage hole h 22 For comparison, if the attenuation slope k2 of h2 is greater than or equal to h... 22 The attenuation slope k 22 If the fuel vaporization system has a leakage hole larger than 1 mm, it is twice the size of the fuel vaporization system; otherwise, it has a leakage hole smaller than 1 mm. Step 3.4: After determining that there is a leak hole smaller than 1mm, continue to pressurize the fuel evaporation system until the saturation pressure p is reached. m1 Then, close the fifth valve (205) and open the sixth valve (206). Step 3.5, the four pressure signals p detected by the pressure sensor group (1) 31 p 32 p 33 p 34 The gasoline volatile gas sensor detects signal C3 and feeds it back to the electronic control module. This process lasts for 30 seconds. Step 3.6: The electronic control module (7) fits the received signal to obtain the fitted pressure change curve h3, h3=f(p 31 p 32 p 33 p 34 (C3), h3 and the pressure change curve of the preset 0.5mm standard leakage hole h 33 For comparison, if the attenuation slope k3 of h3 is greater than or equal to h... 33 The attenuation slope k 33 If the diameter is twice that of the fuel evaporation system, then there is a leak hole larger than 0.5 mm but less than 1 mm; conversely, if the diameter is less than that of the fuel evaporation system, then there is a leak hole smaller than 0.5 mm.

5. The method for detecting leaks in a fuel evaporation system according to claim 1, characterized in that, Step 4 includes the following steps: Step 4.1: After determining the diameter of the system leak hole, acquire the signals P from the four pressure sensors. 41 P 42 P 43 and P 44 Calculate the average value P of the pressure values ​​from its four sensors. n =( P 41 +P 42 +P 43 +P 44 ) / 4; P n With preset pressure value P nn For comparison, if P n ≥P nn If P n <P nn Then the fuel evaporation system is pressurized until the fuel evaporation system pressure reaches P. nn Afterwards, the pressure pump (4) stopped working; Step 4.2: Close all valves. The fuel evaporation system is divided into different modules: fuel tank module, first pipeline module, carbon canister module, and second pipeline module. Step 4.3: Detect the pressure change in the module by using the pressure sensors installed in different module parts. If the pressure drop of the module exceeds the preset standard, then the module has a leak hole; otherwise, there is no leak hole. Then the electronic control module (7) displays the fault on the instrument panel.

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