Automobile fuel evaporation dynamic leakage detection system and detection method

Abstract

This invention discloses a dynamic fuel evaporation leak detection system for automobiles, comprising a fuel tank, a carbon canister, a refueling assembly, an intake assembly, several pressure sensors, a six-degree-of-freedom motion device, and a controller. The fuel tank is fixed on top of the six-degree-of-freedom motion device, and the refueling assembly is fixed to the upper part of one end of the fuel tank. A fuel tank isolation solenoid valve and the upper side of the carbon canister are respectively located on the upper part of the other end of the fuel tank. The nitrogen cylinder of the intake assembly is connected to the upper part of one side of the fuel tank. The pressure sensors are respectively fixed inside the fuel tank, the refueling assembly, the connecting pipe, and the carbon canister. A desorption solenoid valve and an exhaust solenoid valve are respectively located on the upper side of the carbon canister. The detection method is used to detect leaks in the refueling assembly, the fuel tank isolation solenoid valve, the carbon canister, and cracks in the fuel tank. This invention fills the gap in dynamic fuel evaporation leak detection for automobiles, improves the range and accuracy of leak detection, and can efficiently and accurately detect the leak location and orifice size during the dynamic leak process.

Description

Technical Field

[0001] This invention relates to a leak detection system for fuel-powered vehicles, and more particularly to a fuel evaporation leak detection system and method for vehicles, belonging to the field of automotive environmental protection technology. Background Technology

[0002] Evaporative emissions from automotive fuel are a significant source of volatile organic compounds (VOCs), easily contributing to smog and photochemical smog, severely polluting the environment. The "Limits and Measurement Methods for Pollutant Emissions from Light-Duty Vehicles (China Stage VI)" standard imposes stricter requirements on fuel evaporation system leak diagnosis, requiring the ability to diagnose leaks from orifices with a diameter greater than or equal to 1.0 mm (0.5 mm can be used as an alternative if requested by the manufacturer). Furthermore, during vehicle operation, variations in vehicle operating conditions and road conditions cause fuel tank sloshing, exacerbating fuel evaporation and leakage, leading to dynamic leakage. Dynamic fuel evaporation leaks are significantly larger than static fuel evaporation leaks. Therefore, developing dynamic leak detection systems and methods for fuel evaporation systems to reduce fuel leakage is crucial for energy conservation and environmental protection.

[0003] Chinese invention patent CN110031160B discloses a fuel evaporation leakage detection system and method, which installs a pressure sensor between the intake manifold and the carbon canister. The system uses a single pressure sensor to determine whether there is a fuel evaporation leakage, but it cannot determine the location and amount of the leakage.

[0004] Chinese invention patent CN112228217B discloses an on-board diagnostic device for monitoring fuel evaporation leakage in automobiles. It uses ultrasonic sensors and pressure sensors to determine the location and diameter range of the leak hole. It is a static leak detection device and can only detect leaks inside the fuel tank. It cannot detect leaks in other locations such as refueling components, valves, and carbon canisters, nor can it detect the accurate diameter of the leak hole.

[0005] Chinese invention patent application CN112031946A discloses a method for diagnosing faults in a fuel evaporation system. It enables fault diagnosis under non-idling conditions and can diagnose faults in the carbon canister vent valve, carbon canister desorption solenoid valve, first leakage, and second leakage. However, it cannot diagnose leakage faults in other important locations, nor can it diagnose the size of the leakage hole.

[0006] None of the patent documents mentioned above regarding leakage detection in automotive fuel evaporation systems can detect dynamic leaks that occur during vehicle operation, nor can they determine the location of the leak or the exact diameter of the leak hole. Summary of the Invention

[0007] The purpose of this invention is to provide a dynamic leakage detection system and method for automotive fuel evaporation, which can detect dynamic leakage of a vehicle during driving under different road conditions and accurately determine the location and diameter of the leak, thereby improving the accuracy of leakage detection.

[0008] This invention is achieved through the following technical solution:

[0009] A dynamic fuel evaporation leakage detection system for automobiles includes a fuel tank, a carbon canister, a refueling assembly, an intake assembly, several pressure sensors, a six-degree-of-freedom motion device, and a controller. The bottom of the fuel tank is fixed to the top of the six-degree-of-freedom motion device via a mounting plate, and the bottom of the six-degree-of-freedom motion device is supported on the ground. One end of the refueling assembly is fixed to the upper part of one end of the fuel tank, and the upper part of the other end of the fuel tank is connected to the adsorption port on the upper side of the carbon canister via a fuel tank isolation solenoid valve and a connecting pipe. The intake assembly includes a nitrogen cylinder, a flow regulating solenoid valve, and a check valve. The output pipe at the upper end of the nitrogen cylinder is connected to the upper part of one side of the fuel tank via the flow regulating solenoid valve and the check valve. A first pressure sensor is fixed inside the upper side of the fuel tank, a second pressure sensor is fixed inside the upper end of the refueling assembly, a third pressure sensor is fixed inside the middle of the refueling assembly, a fourth pressure sensor is fixed inside the connecting pipe, and a fifth pressure sensor is fixed inside the carbon canister. A desorption solenoid valve and an exhaust solenoid valve are respectively provided on the upper side of the carbon canister. The fuel tank isolation solenoid valve, the flow regulating solenoid valve, the desorption solenoid valve, the exhaust solenoid valve, and each pressure sensor are electrically connected to the controller.

[0010] The objectives of this invention can also be further achieved through the following technical measures.

[0011] Furthermore, the refueling assembly includes a refueling pipe, a refueling cap, and a circulation pipe. The lower end of the refueling pipe is fixedly connected to the upper side of one end of the fuel tank. The refueling cap is located on the top of the refueling pipe. The second pressure sensor is fixed on the inner side of the refueling cap. The two ends of the circulation pipe are respectively connected to the fuel tank and the upper end of the refueling pipe. The third pressure sensor is fixed in the middle of the circulation pipe.

[0012] Furthermore, the six-degree-of-freedom motion device includes an upper moving platform, an array of universal joints, several electric cylinders, and a lower stationary platform. The bottom of the oil tank is fixed to the top of the upper moving platform via a mounting plate. The universal joints are spaced apart between the lower side of the upper moving platform and the upper side of the lower stationary platform. The two ends of the inclined electric cylinders are hinged to the corresponding universal joints. The several electric cylinders are arranged crosswise between the middle of the lower side of the upper moving platform and the middle of the upper side of the lower stationary platform.

[0013] A detection method for a dynamic fuel evaporation leakage detection system for automobiles includes the following steps:

[0014] The main locations of dynamic leaks in automotive fuel evaporation systems can be categorized as leaks in the refueling assembly, fuel tank isolation solenoid valve, carbon canister, and fuel tank cracks.

[0015] Step 1) Determine if the refueling assembly is leaking.

[0016] Leaks in the refueling components are categorized into leaks in the refueling cap and leaks in the recirculation pipe. The detection process is as follows: The controller commands the closure of the tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve, and opens the flow regulating solenoid valve. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the tank reaches the controller's preset target pressure value P... 10 At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value P from the second pressure sensor. 20 The pressure value P of the third pressure sensor 30 and the pressure value P of the fourth pressure sensor 40 Compare P 20 and P 30 Two pressure values ​​and P 10 Differences in pressure values;

[0017] If P 20 <P 10 or P 30 <P 10 If the condition is found to be true, it is determined that there is a leak in the refueling component, and then the precise location of the leak is determined.

[0018] If P 20 <P 10 And P 30 =P 10 If the condition is confirmed, it is determined to be a leak in the fuel filler cap;

[0019] If P 30 <P 10 And P 20 =P 10 If the condition is found to be true, then it is determined to be a leak in the circulation pipe;

[0020] If P 30 <P 10 And P 20 <P 10 If the condition is met, it is determined that both the fuel filler cap and the recirculation pipe are leaking.

[0021] If P 20 =P 10 And P 30 =P 10 If the condition is met, it is determined that there is no leakage in the refueling component; if there is no leakage in the refueling component, proceed to step 2); otherwise, proceed directly to step 5.

[0022] Step 2) Determine if the fuel tank isolation solenoid valve is leaking.

[0023] Repeat the detection process in step 1) and compare P. 40 Pressure value and P0 pressure value and P 10 The difference in pressure values, where P0 is standard atmosphere.

[0024] If P0 = P 40 <P 10 If so, it is determined that the fuel tank isolation solenoid valve has no leakage;

[0025] If P0 < P 40 ≤P 10 If the fuel tank isolation solenoid valve is found to be leaking, proceed to step 3); otherwise proceed directly to step 5.

[0026] Step 3) Check if there are cracks or leaks in the fuel tank.

[0027] Repeat step 1) of the detection process until the first pressure sensor in the fuel tank reaches the preset target pressure value P. 10 At that time, the controller commands the flow regulating solenoid valve to close, according to P. 10 Whether to reduce or decrease the level to determine the leakage situation, if P 10 If there is no change, it is determined that the fuel tank has no cracks or leaks; if P 10 If the pressure value decreases over time, it is determined that there is a crack in the oil tank and a leak; if there is no crack in the oil tank and a leak occurs, proceed to step 4); otherwise, proceed directly to step 5.

[0028] Step 4) Check for leaks in the carbon canister.

[0029] The controller commands the desorption solenoid valve and exhaust solenoid valve to close, and the tank isolation solenoid valve and flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and check valve to enter the tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the tank reaches the controller's preset target pressure value P... 10 At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value P from the fifth pressure sensor. 50 Compare P 10 and P 50 Differences in pressure values;

[0030] If P 50 =P 10 If so, it is determined that there is no leak in the carbon canister;

[0031] If P 50 <P 10 If so, it is determined that the carbon canister is leaking;

[0032] Step 5) Calibration test of standard leakage hole

[0033] Before determining the leakage orifice diameter corresponding to the leakage point during dynamic leakage, a calibration test of the standard leakage orifice is first performed. Standard leakage orifices with diameters of 0.5 mm and 1.0 mm are installed on the oil tank. The controller commands the oil tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve to close, and the flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the oil tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the oil tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the oil tank reaches the preset target pressure value P... 10 At that time, the controller commands the flow regulating solenoid valve to close and starts timing, recording the pressure value P from the first pressure sensor. 10 The curve showing the relationship between time t and P 10 The calibration ends when the value drops to P0.

[0034] During the calibration test of the 0.5mm diameter leakage hole, the pressure value of the first pressure sensor was determined by P. 10 Let t be the time taken to descend to P0. 01 During the calibration test of a 1.0mm diameter leakage hole, the pressure value of the first pressure sensor was determined by P. 10 Let t be the time taken to descend to P0. 02 Therefore, the pressure decay rate is [missing information] for a 0.5mm diameter leak hole. Pressure decay rate at a 1.0 mm diameter leak hole

[0035] Step 6) Determine the range of the leakage orifice diameter.

[0036] When the leak is located at the fuel filler cap, recirculation pipe, fuel tank isolation solenoid valve, or fuel tank crack, the detection process is as follows: The controller commands the fuel tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve to close, and the flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and check valve to enter the fuel tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the fuel tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the fuel tank reaches the preset target pressure value P... 10 At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value P from the first pressure sensor. t The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor changes from P... 10 Let t be the time taken to descend to P0. 10 Then the leakage rate Compare v10 v 01 and v 02 Size;

[0037] If v 10 ≤v 01 Then determine the diameter of the leakage hole.

[0038] If v 01 <v 10 <v 02 Then determine the diameter of the leakage hole.

[0039] If v 10 ≥v 02 Then determine

[0040] When there is a leak in the carbon canister, the detection process is as follows: The controller commands the desorption solenoid valve and the exhaust solenoid valve to close, and the flow regulating solenoid valve and the tank isolation solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the tank reaches the preset target pressure value P... 10 At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value P from the first pressure sensor. 10 The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor changes from P... 10 Let t be the time taken to descend to P0. 10 Then the leakage rate Compare v 10 v 01 and v 02 The size of v 10 ≤v 01 Then determine the diameter of the leakage hole.

[0041] If v 01 <v 10 <v 02 Then determine the diameter of the leakage hole. If v 10 ≥v 02 Then determine the diameter of the leakage hole.

[0042] Step 7) Calculate the diameter of the leakage hole.

[0043] First, based on the pressure value P of the first pressure sensor in step 6). t By fitting the curve of the relationship between pressure and time and the function formula, the pressure value P can be obtained.t The exponential function relationship with respect to time t: P t =a (x+b) +c;

[0044] In the formula, a, b, and c are all constants;

[0045] According to formula P 10 V = P t V+P0V Leak and V Leak =Q t ·t, thus obtaining Volumetric flow rate Q at the leak point t The formula relating to time t;

[0046] In the formula, P0 is the standard atmospheric pressure; V is the volume occupied by air in the fuel tank, calculated by subtracting the fuel volume from the total fuel tank volume; using the method of undetermined coefficients, values ​​for t are taken, and P is obtained based on the curve and calculation formula. t and Q t A specific pressure value, then according to the formula: Calculate the gas density ρ inside the tank at time t. t In the formula, ρ t0 Given the air density at standard atmospheric pressure; calculate the mass flow rate Q at the leak point. h =Q t ·ρ t Then according to the formula The cross-sectional area A of the leak hole was calculated.

[0047] In the formula: C d Let γ be the leakage coefficient and γ be the specific heat capacity of the gas; both are constants. The flow coefficient is calculated using the following formula: After obtaining the cross-sectional area A, then according to the formula... Convert to formula Finally, the diameter value of the leakage hole d was calculated.

[0048] This invention's six-degree-of-freedom motion device, through the extension and retraction of an inclined electric cylinder, enables a fuel tank fixed to the top of an upper moving platform to perform six-degree-of-freedom motion along the X, Y, and Z axes in three-dimensional space. It reproduces actual road conditions by using a pre-defined road spectrum and employs an intake assembly and several pressure sensors to detect dynamic fuel leakage, filling a gap in current automotive fuel evaporation dynamic leakage detection devices. The detection method of this invention is based on pressure change detection and formula calculation to determine the leakage location and leakage orifice range of the fuel evaporation system, ultimately calculating an accurate value for the leakage orifice diameter. This improves the range and accuracy of leakage detection, achieving efficient and precise detection of leakage location and orifice diameter during dynamic leakage processes.

[0049] The advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments, which are given by way of example only with reference to the accompanying drawings. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of the automotive fuel evaporation dynamic leakage detection system of the present invention;

[0051] Figure 2 This is a flowchart of the detection method of the present invention;

[0052] Figure 3 This is a flowchart of the detection process of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0054] In the description of this invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" that indicate orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and do not indicate or imply that the device referred to must have a specific orientation.

[0055] like Figures 1-3 As shown, this embodiment includes a fuel tank 1, a carbon canister 2, a refueling assembly 3, an intake assembly 4, five pressure sensors, a six-degree-of-freedom motion device 6, and a controller 7. The six-degree-of-freedom motion device 6 includes an upper moving platform 61, 12 sets of universal joints 62, six electric cylinders 63, and a lower stationary platform 64. The bottom of the fuel tank 1 is fixed to the top of the upper moving platform 61 by a mounting plate 11. The universal joints 62 are spaced apart between the lower side of the upper moving platform 61 and the upper side of the lower stationary platform 64. The two ends of the inclined electric cylinders 63 are hinged to the corresponding universal joints 62. The six electric cylinders 63 are arranged crosswise between the lower middle of the upper moving platform 61 and the upper middle of the lower stationary platform 64. The different extensions and retractions of the six electric cylinders 63 drive the upper moving platform 61 to perform six-degree-of-freedom motion in three-dimensional space, moving and rotating along the X, Y, and Z axes respectively. This allows the fuel tank 1 fixed on the upper moving platform 61 to reproduce the actual road conditions of the vehicle according to a set road map.

[0056] The refueling assembly 3 includes a refueling pipe 31, a refueling cap 32, and a circulation pipe 33. The lower end of the refueling pipe 31 is fixedly connected to the upper right side of the fuel tank 1. The refueling cap 32 is located on the top of the refueling pipe 31. The second pressure sensor 52 is fixed on the inner side of the refueling cap 32. The two ends of the circulation pipe 33 are respectively connected to the fuel tank 1 and the upper end of the refueling pipe 31. The third pressure sensor 53 is fixed in the middle of the circulation pipe 33.

[0057] The intake assembly 4 includes a nitrogen cylinder 41, a flow regulating solenoid valve 42, and a check valve 43. The output pipe 411 at the upper end of the nitrogen cylinder 41 is connected to the upper right side of the oil tank 1 through the flow regulating solenoid valve 42 and the check valve 43 in sequence.

[0058] The upper left end of the fuel tank 1 is connected to the adsorption port 21 on the upper side of the carbon canister 2 via a fuel tank isolation solenoid valve 12 and a connecting pipe 13. The air intake assembly 4 includes a nitrogen cylinder 41, a flow regulating solenoid valve 42, and a one-way valve 43. The output pipe 411 at the upper end of the nitrogen cylinder 41 is connected to the upper right side of the fuel tank 1 via the flow regulating solenoid valve 42 and the one-way valve 43. The first pressure sensor 51 is fixed inside the upper side of the fuel tank 1, the fourth pressure sensor 54 is fixed inside the connecting pipe 13, and the fifth pressure sensor 55 is fixed inside the carbon canister 2. A desorption solenoid valve 22 and an exhaust solenoid valve 23 are respectively provided on the upper side of the carbon canister 2. The fuel tank isolation solenoid valve 12, the flow regulating solenoid valve 42, the desorption solenoid valve 22, the exhaust solenoid valve 23, and each pressure sensor are electrically connected to the controller 7.

[0059] The controller 7 includes a control module and a detection module. The control module is responsible for controlling the opening and closing of each solenoid valve and the start and stop of each electric cylinder 63 of the six-degree-of-freedom motion device 6. The control module also needs to optimize the acquired road spectrum signal by performing Fourier transform on the displacement and acceleration parameter signals of the road spectrum and iteratively correcting them multiple times to ensure that the root mean square error of the signal is less than 10%. The iterative root mean square error E rr The calculation method is as follows

[0060] In the formula, Y d (t) represents the desired time-domain response signal (kN), Y i (t) represents the i-th response signal (kN).

[0061] The detection module is responsible for receiving the pressure signal from the pressure sensor and determining the location and size of the leak hole based on the dynamic leakage detection method of the automotive fuel evaporation system, and finally obtaining an accurate dynamic leakage situation.

[0062] A detection method for a dynamic fuel evaporation leakage detection system for automobiles includes the following steps:

[0063] The main locations of dynamic leaks in the automotive fuel evaporation system are: leaks in the refueling component 3, leaks in the fuel tank isolation solenoid valve 12, leaks in the carbon canister 2, and leaks from cracks in the fuel tank 1.

[0064] Step 1) Determine if refueling component 3 is leaking.

[0065] Leaks in the refueling component 3 are categorized into leaks in the refueling cap 32 and leaks in the circulation pipe 33. The detection process is as follows: Controller 7 instructs the closure of the tank isolation solenoid valve 12, desorption solenoid valve 22, and exhaust solenoid valve 23, and opens the flow regulating solenoid valve 42. Nitrogen gas from nitrogen cylinder 41 enters the output pipe 411 and sequentially passes through the flow regulating solenoid valve 42 and the check valve 43 to enter the tank 1 at a constant flow rate. Controller 7 extends and retracts the corresponding electric cylinder 63 of the six-degree-of-freedom motion device 6 according to the input actual road spectrum command, thereby driving the tank 1 to move according to the corresponding degree of freedom according to the actual road spectrum. When the first pressure sensor 51 in the tank 1 reaches the preset target pressure value P of controller 7... 10 At that time, controller 7 commands the flow regulating solenoid valve 42 to close and records the pressure value P of the second pressure sensor 52. 20 The pressure value P of the third pressure sensor 53 30 and the pressure value P of the fourth pressure sensor 54 40 Compare P 20 and P 30 Two pressure values ​​and P 10 Differences in pressure values.

[0066] If P 20 <P 10 or P 30 <P 10 If the condition is found to be true, it is determined that there is a leak in refueling component 3, and then the precise location of the leak is determined.

[0067] If P 20 <P 10 And P 30 =P 10 If the condition is confirmed, then it is determined that the fuel filler cap 32 is leaking.

[0068] If P 30 <P 10 And P 20 =P 10 If the condition is met, then the leak is determined to be in circulation pipe 33.

[0069] If P 30 <P 10 And P 20 <P 10 If this is confirmed, it is determined that both the filler cap 32 and the circulation pipe 33 are leaking.

[0070] If P 20 =P 10 And P 30 =P 10 If the condition is met, it is determined that there is no leakage in refueling component 3; if there is no leakage in refueling component 3, proceed to step 2); otherwise, proceed directly to step 5.

[0071] Step 2) Determine if the fuel tank isolation solenoid valve 12 is leaking.

[0072] Repeat the detection process in step 1) and compare P. 40 Pressure value and P0 pressure value and P 10 The difference in pressure values, where P0 is standard atmospheric pressure.

[0073] If P0 = P 40 <P 10 If so, it is determined that there is no leakage in the oil tank isolation solenoid valve 12;

[0074] If P0 < P 40 ≤P 10 If there is no leakage in the oil tank isolation solenoid valve 12, it is determined that the oil tank isolation solenoid valve 12 is leaking; if there is no leakage in the oil tank isolation solenoid valve 12, proceed to step 3); otherwise, proceed directly to step 5.

[0075] Step 3) Check if there are cracks or leaks in fuel tank 1.

[0076] Repeat step 1) of the detection process. When the first pressure sensor 51 in the oil tank 1 reaches the preset target pressure value P... 10 At that time, controller 7 commands to close flow regulating solenoid valve 42, according to P 10 Whether to reduce or decrease the level to determine the leakage situation, if P 10 If there is no change, then it is determined that fuel tank 1 has no cracks or leaks. If P 10 If the pressure value decreases over time, it is determined that there is a crack and leakage in oil tank 1. If there is no crack and leakage in oil tank 1, proceed to step 4); otherwise, proceed directly to step 5.

[0077] Step 4) Check for leaks in carbon canister 2.

[0078] Controller 7 commands the desorption solenoid valve 22 and exhaust solenoid valve 23 to close, and the oil tank isolation solenoid valve 12 and flow regulating solenoid valve 42 to open. Nitrogen gas from nitrogen cylinder 41 enters the output pipe 411 and sequentially passes through flow regulating solenoid valve 42 and check valve 43 to enter the oil tank 1 at a constant flow rate. Controller 7 extends and retracts the corresponding electric cylinder 63 of the six-degree-of-freedom motion device 6 according to the input actual road spectrum command, thereby driving the oil tank 1 to move according to the corresponding degree of freedom according to the actual road spectrum. When the first pressure sensor 51 in the oil tank 1 reaches the preset target pressure value P of controller 7... 10 At that time, controller 7 commands the flow regulating solenoid valve 42 to close and records the pressure value P of the fifth pressure sensor 55. 50 Compare P 10 and P 50 Differences in pressure values.

[0079] If P 50 =P 10 If so, it is determined that there is no leakage in carbon canister 2;

[0080] If P 50<P 10 If so, it is determined that carbon canister 2 is leaking.

[0081] Step 5) Calibration test of standard leakage hole

[0082] Before determining the leakage orifice diameter corresponding to the leakage point during dynamic leakage, a calibration test of the standard leakage orifice is performed. Standard leakage orifices with diameters of 0.5 mm and 1.0 mm are respectively installed on the oil tank 1. The controller 7 commands the oil tank isolation solenoid valve 12, desorption solenoid valve 22, and exhaust solenoid valve 23 to close, and the flow regulating solenoid valve 42 to open. Nitrogen gas from the nitrogen cylinder 41 enters the output pipe 411 and sequentially passes through the flow regulating solenoid valve 42 and the one-way valve 43 to enter the oil tank 1 at a constant flow rate. The controller 7 extends and retracts the corresponding electric cylinder 63 of the six-degree-of-freedom motion device 6 according to the input actual path spectrum command, thereby driving the oil tank 1 to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor 51 in the oil tank 1 reaches the preset target pressure value P... 10 At that time, controller 7 instructs to close the flow regulating solenoid valve 42 and starts timing. Controller 7 records the pressure value P from the first pressure sensor. 10 The curve showing the relationship between time t and P 10 The calibration ends when the value drops to P0.

[0083] During the calibration test of the 0.5mm diameter leakage hole, the pressure value of the first pressure sensor 51 was determined by P. 10 Let t be the time taken to descend to P0. 01 During the calibration test of the 1.0mm diameter leakage hole, the pressure value of the first pressure sensor 51 was determined by P. 10 Let t be the time taken to descend to P0. 02 Therefore, the pressure decay rate at a leakage orifice with a diameter of 0.5 mm is... Pressure decay rate at a 1.0 mm diameter leak hole

[0084] Step 6) Determine the range of the leakage orifice diameter.

[0085] When the leak is located at the filler cap 32, the circulation pipe 33, the fuel tank isolation solenoid valve 12, or a crack in the fuel tank 1, the detection process is as follows: Controller 7 commands the fuel tank isolation solenoid valve 12, the desorption solenoid valve 22, and the exhaust solenoid valve 23 to close, and opens the flow regulating solenoid valve 42. Nitrogen gas from nitrogen cylinder 41 enters the output pipe 411 and sequentially passes through the flow regulating solenoid valve 42 and the check valve 43 to enter the fuel tank 1 at a constant flow rate. Controller 7 extends and retracts the corresponding electric cylinder 63 of the six-degree-of-freedom motion device 6 according to the input actual path spectrum command, thereby driving the fuel tank 1 to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor 51 in the fuel tank 1 reaches the preset target pressure value P... 10At that time, controller 7 commands the flow regulating solenoid valve 42 to close and records the pressure value P of the first pressure sensor 51. t The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor 51 changes from P 10 Let t be the time taken to descend to P0. 10 Then the leakage rate Compare v 10 v 01 and v 02 Size;

[0086] If v 10 ≤v 01 Then determine the diameter of the leakage hole. If v 01 <v 10 <v 02 Then determine the diameter of the leakage hole.

[0087] If v 10 ≥v 02 Then determine

[0088] When there is a leak in the carbon canister 2, the detection process is as follows: The controller 7 commands the desorption solenoid valve 22 and the exhaust solenoid valve 23 to close, and the flow regulating solenoid valve 42 and the oil tank isolation solenoid valve 12 to open. Nitrogen gas in the nitrogen cylinder 41 enters the output pipe 411 and passes through the flow regulating solenoid valve 42 and the check valve 43 in sequence to enter the oil tank 1 at a constant flow rate. The controller 7 extends and retracts the corresponding electric cylinder 63 of the six-degree-of-freedom motion device 6 according to the input actual path spectrum command, thereby driving the oil tank 1 to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor 51 in the oil tank 1 reaches the preset target pressure value P... 10 At that time, controller 7 commands the flow regulating solenoid valve 42 to close and records the pressure value P of the first pressure sensor 51. 10 The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor 51 changes from P 10 Let t be the time taken to descend to P0. 10 Then the leakage rate

[0089] Compare v 10 v 01 and v 02 The size of v 10 ≤v 01 Then determine the diameter of the leakage hole.

[0090] If v 01 <v 10 <v 02 Then determine the diameter of the leakage hole.

[0091] If v 10 ≥v 02 Then determine the diameter of the leakage hole.

[0092] Step 7) Calculate the diameter of the leakage hole.

[0093] First, based on the pressure value P of the first pressure sensor 51 in step 6). t By fitting the curve of the relationship between pressure and time and the function formula, the pressure value P can be obtained. t The exponential function relationship with respect to time t: P t =a (x+b) +c, where a, b, and c are all constants.

[0094] According to formula P 10 V = P t V+P0V Leak and V Leak =Q t ·t, thus obtaining Volumetric flow rate Q at the leak point t The formula relates to time t; where P0 is standard atmospheric pressure; V is the volume of air in the fuel tank, calculated as the total volume of the fuel tank minus the volume of fuel. Using the method of undetermined coefficients, values ​​for t are taken, and P is obtained based on the curve and calculation formula. t and Q t A specific pressure value, then according to the formula: Calculate the gas density ρ inside the tank at time t. t In the formula, ρ t0 Given the air density at standard atmospheric pressure; calculate the mass flow rate Q at the leak point. h =Q t ·ρ t Then according to the formula The cross-sectional area A of the leak hole was calculated.

[0095] In the formula: C d Let γ be the leakage coefficient and γ be the specific heat capacity of the gas; both are constants. The flow coefficient is calculated using the following formula: After obtaining the cross-sectional area A, then according to the formula... Convert to formula Finally, the diameter value of the leakage hole d was calculated.

[0096] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A detection method for a dynamic fuel evaporation leakage detection system for automobiles, wherein the dynamic fuel evaporation leakage detection system includes a fuel tank, a carbon canister, a refueling assembly, an intake assembly, several pressure sensors, a controller, and a six-degree-of-freedom motion device. The bottom of the fuel tank is fixed to the top of the six-degree-of-freedom motion device via a mounting plate, and the bottom of the six-degree-of-freedom motion device is supported on the ground. One end of the refueling assembly is fixed to the upper part of one end of the fuel tank, and the upper part of the other end of the fuel tank is connected to the adsorption port on the upper side of the carbon canister via a fuel tank isolation solenoid valve and a connecting pipe. The intake assembly includes a nitrogen cylinder and a flow regulator. The output pipe at the top of the nitrogen cylinder is connected to the upper part of the oil tank via a flow regulating solenoid valve and a check valve. The first pressure sensor is fixed inside the upper side of the oil tank, the second pressure sensor is fixed inside the upper end of the refueling assembly, the third pressure sensor is fixed inside the middle of the refueling assembly, the fourth pressure sensor is fixed inside the connecting pipe, and the fifth pressure sensor is fixed inside the carbon canister. A desorption solenoid valve and an exhaust solenoid valve are respectively installed on the upper side of the carbon canister. The oil tank isolation solenoid valve, the flow regulating solenoid valve, the desorption solenoid valve, the exhaust solenoid valve, and each pressure sensor are electrically connected to the controller. The refueling assembly includes a refueling pipe, a refueling cap, and a circulation pipe. The lower end of the refueling pipe is fixedly connected to the upper side of one end of the fuel tank. The refueling cap is located on the top of the refueling pipe. The second pressure sensor is fixed on the inner side of the refueling cap. The two ends of the circulation pipe are respectively connected to the fuel tank and the upper end of the refueling pipe. The third pressure sensor is fixed in the middle of the circulation pipe. Its features are, Includes the following steps: The dynamic leakage locations of automotive fuel evaporation systems can be categorized into refueling component leaks, fuel tank isolation solenoid valve leaks, carbon canister leaks, and fuel tank crack leaks. Step 1) Determine if the refueling assembly is leaking. Leaks in the refueling components are categorized into leaks in the refueling cap and leaks in the recirculation pipe. The detection process is as follows: The controller commands the closure of the tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve, and opens the flow regulating solenoid valve. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the tank reaches the controller's preset target pressure value... At that time, the controller commands the flow regulating valve to close and records the pressure value of the second pressure sensor. The pressure value of the third pressure sensor and the pressure value of the fourth pressure sensor ,Compare and Two pressure values ​​and Differences in pressure values; like < or < If the condition is found to be true, it is determined that there is a leak in the refueling component, and then the precise location of the leak is determined. like < and = If the condition is confirmed, it is determined to be a leak in the fuel filler cap; like < and = If the condition is found to be true, then it is determined to be a leak in the circulation pipe; like < and < If the condition is met, it is determined that both the fuel filler cap and the recirculation pipe are leaking. like = and = If the condition is met, it is determined that there is no leakage in the refueling component; if there is no leakage in the refueling component, proceed to step 2); otherwise, proceed to the calibration test of the standard leakage hole, determine the range of the leakage hole diameter, and calculate the leakage hole diameter value in sequence. Step 2) Determine if the fuel tank isolation solenoid valve is leaking. Repeat the detection process in step 1) and compare. Pressure value and pressure value and Difference in pressure values, Standard atmospheric pressure; like = < If so, it is determined that the fuel tank isolation solenoid valve has no leakage; like < ≤ If there is no leakage in the oil tank isolation solenoid valve, proceed to step 3; otherwise, proceed to the calibration test of the standard leakage hole, determine the range of the leakage hole diameter, and calculate the leakage hole diameter value in sequence. Step 3) Check if there are cracks or leaks in the fuel tank. Repeat step 1) of the detection process until the first pressure sensor in the fuel tank reaches the preset target pressure value. At that time, the controller commands the flow regulating solenoid valve to close, according to... Whether to reduce the level to determine the leakage situation, if If there is no change, it is determined that the fuel tank has no cracks or leaks; if If the pressure value decreases over time, it is determined that the oil tank has a crack and is leaking; if there is no crack and the oil tank is leaking, proceed to step 4); otherwise, proceed to the standard leak hole calibration test, determine the range of the leak hole diameter, and calculate the leak hole diameter value in sequence. Step 4) Check for leaks in the carbon canister. The controller commands the desorption solenoid valve and exhaust solenoid valve to close, and the oil tank isolation solenoid valve and flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and check valve to enter the oil tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the oil tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the oil tank reaches the controller's preset target pressure value... At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value of the fifth pressure sensor. ,Compare and Differences in pressure values; like = If so, it is determined that there is no leak in the carbon canister; like < If so, it is determined that the carbon canister is leaking.

2. The detection method of the automotive fuel evaporation dynamic leakage detection system as described in claim 1, characterized in that, It also includes the following steps: Step 5) Calibration test of standard leakage hole Before determining the leakage orifice diameter corresponding to the leakage point during dynamic leakage, a calibration test of the standard leakage orifice is first performed. Standard leakage orifices with diameters of 0.5 mm and 1.0 mm are installed on the oil tank. The controller commands the oil tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve to close, and the flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the oil tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the oil tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the oil tank reaches the preset target pressure value... At that time, the controller commands the flow regulating solenoid valve to close and starts timing, recording the pressure value from the first pressure sensor. Over time The curve showing the relationship between changes, until... Down to Calibration complete; During the calibration test of the 0.5mm diameter leakage hole, the pressure value of the first pressure sensor was changed from... Down to The time elapsed is recorded as During the calibration test of the 1.0mm diameter leakage hole, the pressure value of the first pressure sensor was determined by... Down to The time elapsed is recorded as Therefore, the pressure decay rate is [missing information] for a 0.5mm diameter leak hole. Pressure decay rate at a leakage orifice with a diameter of 1.0 mm ; Step 6) Determine the range of the leakage orifice diameter. When the leak is located at the fuel filler cap, recirculation pipe, fuel tank isolation solenoid valve, or fuel tank crack, the detection process is as follows: The controller commands the fuel tank isolation solenoid valve, desorption solenoid valve, and exhaust solenoid valve to close, and the flow regulating solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and check valve to enter the fuel tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the fuel tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the fuel tank reaches the preset target pressure value... At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value of the first pressure sensor. The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor changes from... Down to The time elapsed is recorded as Then the leakage rate ,Compare , and Size; like If the diameter of the leak hole is φ≤0.5mm, then it is determined that the diameter of the leak hole is ≤0.5mm. like If the diameter of the leak hole is 0.5mm < φ < 1.0mm, then it is determined that the diameter of the leak hole is 0.5mm < φ < 1.0mm. like If the diameter of the leak hole φ is greater than or equal to 1.0 mm, then it is determined that the diameter of the leak hole is greater than or equal to 1.0 mm. When there is a leak in the carbon canister, the detection process is as follows: The controller commands the desorption solenoid valve and the exhaust solenoid valve to close, and the flow regulating solenoid valve and the tank isolation solenoid valve to open. Nitrogen gas from the nitrogen cylinder enters the output pipe and sequentially passes through the flow regulating solenoid valve and the check valve to enter the tank at a constant flow rate. The controller extends and retracts the corresponding electric cylinder of the six-degree-of-freedom motion device according to the input actual path spectrum command, thereby driving the tank to move according to the corresponding degree of freedom according to the actual path spectrum. When the first pressure sensor in the tank reaches the preset target pressure value... At that time, the controller commands the flow regulating solenoid valve to close and records the pressure value of the first pressure sensor. The curve showing the relationship between pressure and time, where the pressure value of the first pressure sensor changes from... Down to The time elapsed is recorded as Then the leakage rate ,Compare , and The size, if If the diameter of the leak hole is φ≤0.5mm, then it is determined that the diameter of the leak hole is ≤0.5mm. like If the diameter of the leak hole is 0.5mm < φ < 1.0mm, then it is determined that the diameter of the leak hole is 0.5mm < φ < 1.0mm. like If the diameter of the leak hole φ is greater than or equal to 1.0 mm, then it is determined that the diameter of the leak hole is greater than or equal to 1.0 mm. Step 7) Calculate the diameter of the leakage hole. First, based on the pressure value of the first pressure sensor in step 6). By fitting the curve of the relationship between pressure and time to the function formula, the pressure value can be obtained. Regarding time The exponential function relationship: ; In the formula, a, b, and c are all constants; According to the formula and , and thus Volumetric flow rate at the leak point Regarding time Relationship; In the formula, Standard atmospheric pressure; The volume occupied by air in the fuel tank is calculated by subtracting the fuel volume from the total fuel tank volume. Using the method of undetermined coefficients, for Values ​​are selected, and the results are obtained based on the curve and calculation formula. and A specific pressure value, then according to the formula: ,calculate Gas density inside the fuel tank at any given time In the formula The density of air at standard atmospheric pressure; Calculate the mass flow rate at the leak point. Then according to the formula The cross-sectional area of ​​the leakage hole was calculated. ; In the formula: Leakage coefficient, Here, represents the specific heat capacity of the gas, and all are constants. The flow coefficient is calculated using the following formula: ; derive the cross-sectional area Then, according to the formula Convert to formula Finally, the leakage hole was calculated. Diameter value.

3. The detection method of the automotive fuel evaporation dynamic leakage detection system as described in claim 1, characterized in that, The six-degree-of-freedom motion device includes an upper moving platform, an array of universal joints, several electric cylinders, and a lower stationary platform. The bottom of the oil tank is fixed to the top of the upper moving platform by a mounting plate. The universal joints are spaced apart between the lower side of the upper moving platform and the upper side of the lower stationary platform. The two ends of the inclined electric cylinders are respectively hinged to the corresponding universal joints.

4. The detection method of the automotive fuel evaporation dynamic leakage detection system as described in claim 3, characterized in that, Several electric cylinders are arranged in a cross configuration between the lower middle part of the upper moving platform and the upper middle part of the lower stationary platform.

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