Evaporation system leakage fault diagnosis method and storage medium

Abstract

The invention provides an evaporation system leakage fault diagnosis method and a storage medium, and belongs to the technical field of automobile fuel oil equipment control. The method comprises the steps that firstly, signals are collected, whether fault diagnosis conditions are met or not is judged according to the signals, diagnosis working condition request conditions are entered, and evaporation system leakage fault diagnosis is conducted after the fault diagnosis conditions are met and the diagnosis working condition request conditions are entered; moreover, in the process of diagnosing the leakage fault of the evaporation system, if the condition of quitting the working condition coordination is met, the diagnosis is interrupted. Evaporation system leakage fault diagnosis can be carried out in the running state, the diagnosis completion probability is increased, the driving cycle diagnosis frequency is reduced, and NVH complaints caused by engine starting and running during parking or pre-stopping (low vehicle speed) are reduced. In addition, the number of times of interruption diagnosis is reduced, the one-time diagnosis completion rate is increased, and the IUPR rate is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile fuel equipment control, and in particular relates to an evaporation system leakage fault diagnosis method and a storage medium. Background Art

[0002] At present, the diagnosis of fuel system leakage in automobiles is done by pumping or extracting air into the fuel system, judging the rate of change of the fuel tank pressure, and determining whether there is a leakage in the fuel evaporation system. The current hybrid evaporation system leakage diagnosis technology is mainly divided into two types according to the extraction method: 1. When the engine is stopped, use an air pump to pump air into the evaporation system pipeline, carbon canister, and fuel tank, and determine whether there is a leakage by the difficulty of pumping air; 2. When the engine is running, control the engine power to form a negative pressure (relative to atmospheric pressure) in the intake manifold, and extract air from the evaporation system pipeline, carbon canister, and fuel tank. After the negative pressure is formed, the pressure is maintained, and the rate of change of the fuel tank pressure is judged to determine whether there is a leakage.

[0003] For the second type of air extraction, the existing technology mainly prohibits the engine from stopping or requesting to start the engine in the pre-parking state or parking state, controls the engine power to extract air, and mainly judges whether to enter the control engine extraction based on the braking and vehicle speed signals. Among them, when diagnosing in the parking or pre-parking state, it is necessary to keep the engine running or request the engine to start, resulting in poor NVH (Noise, Vibration, Harshness); when the high-pressure Ready parking or pre-parking state lasts for a short time, the diagnosis process is easily interrupted, resulting in repeated diagnosis in a driving cycle. If the single driving cycle time is short, the diagnosis cannot be completed, resulting in too low IUPR (In Use (Monitor) Performance Ratio) rate. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art, and to provide an evaporation system leakage fault diagnosis method and storage medium, so as to reduce the number of interruption diagnosis times, improve the one-time diagnosis completion rate, and improve the IUPR rate.

[0005] The present invention is achieved through the following technical solutions:

[0006] A first aspect of the present invention provides an evaporation system leakage fault diagnosis method, which first collects signals and determines whether fault diagnosis conditions and diagnostic operating condition request conditions are met based on the signals, and performs evaporation system leakage fault diagnosis after the fault diagnosis conditions and diagnostic operating condition request conditions are met; and during the evaporation system leakage fault diagnosis process, if the exit operating condition coordination conditions are met, the diagnosis is interrupted.

[0007] A further improvement of the present invention is:

[0008] The method comprises:

[0009] (0) Initialization: Set the initial value of the number of non-response request conditions to 0, and set the initial value of the number of interrupt diagnosis conditions to 0;

[0010] (1) Collecting signals and determining whether the fault diagnosis conditions are met, if yes, proceeding to step (2), if no, returning to step (0);

[0011] (2) determining whether the diagnostic condition is satisfied, if yes, proceeding to step (3), if no, returning to step (1);

[0012] (3) determining whether the priority of the evaporative system diagnostic operating condition request is the highest; if so, sending an operating condition coordination request signal, an operating condition request engine speed, an operating condition request engine torque, and an operating condition coordination request priority, and then proceeding to step (4); if not, returning to step (1);

[0013] (4) Sending a request for evaporation system diagnostic status;

[0014] (5) Determine whether to respond to the diagnostic condition request. If yes, proceed to step (6). If not, increase the number of non-response request conditions by 1, and then proceed to step (7).

[0015] (6) Coordinate the response to the operating conditions and then perform evaporation system leakage fault diagnosis;

[0016] (7) determining whether to end the evaporative system diagnosis for the current driving cycle; if so, proceeding to step (8); if not, returning to step (0);

[0017] (8)End.

[0018] A further improvement of the present invention is:

[0019] In step (1), the operation of determining whether the fault diagnosis condition is met includes: if the following nine conditions are met at the same time, it is determined that the fault diagnosis condition is met; if any one of the following nine conditions is not met, it is determined that the fault diagnosis condition is not met:

[0020] There are no evaporation system related faults;

[0021] The ambient temperature is within the temperature diagnosis range;

[0022] The environmental pressure is within the environmental pressure diagnosis range;

[0023] The fuel tank pressure is within the fuel tank pressure diagnostic range;

[0024] The oil level percentage is lower than the set oil level percentage;

[0025] The carbon canister load is less than the load threshold;

[0026] The starting water temperature is within the starting water temperature diagnostic range and the engine running time is greater than the running time threshold;

[0027] Stable air-fuel ratio;

[0028] The time interval between two diagnoses is greater than the diagnostic interval threshold.

[0029] A further improvement of the present invention is:

[0030] In step (2), the operation of determining whether the condition for entering the diagnostic operating condition is met includes:

[0031] If the following five conditions are met at the same time, it is determined that the condition for entering the diagnostic condition is met; if any one of the following five conditions is not met, it is determined that the condition for entering the diagnostic condition is not met:

[0032] The vehicle speed is lower than the diagnostic speed threshold;

[0033] The acceleration is less than the acceleration threshold for entering the diagnosis;

[0034] The slope is less than the diagnostic slope threshold;

[0035] The SOC is greater than the diagnostic SOC threshold;

[0036] The power required by the driver is less than the difference between the battery's allowable discharge power and the power reserved for entering diagnosis.

[0037] A further improvement of the present invention is:

[0038] In step (5), the operation of determining whether to respond to the diagnostic condition request includes:

[0039] Determine whether the priority of the operating condition coordination request is the highest. If so, determine to respond to the diagnostic operating condition request. If not, determine whether the response conditions are met. If so, determine to respond to the diagnostic operating condition request. If not, determine not to respond to the diagnostic operating condition request.

[0040] A further improvement of the present invention is:

[0041] The operations for determining whether the response conditions are met include:

[0042] If the following three conditions are met at the same time, the response condition is determined to be met; if any of the following three conditions is not met, the response condition is determined to be not met:

[0043] The slope is less than the slope threshold;

[0044] SOC is greater than the SOC threshold;

[0045] The power required by the driver is less than the difference between the battery's allowable discharge power and the reserved power.

[0046] A further improvement of the present invention is:

[0047] In step (6), the operation of coordinating the operating condition response includes: controlling the engine speed and torque to reach the operating condition requested engine speed and the operating condition requested engine torque.

[0048] A further improvement of the present invention is:

[0049] In step (6), the operation of diagnosing the leakage fault of the evaporation system includes:

[0050] Phase A: Carbon canister vent valve monitoring and tank pressure stabilization phase

[0051] If the ventilation valve stuck closed fault is detected, the fault diagnosis is terminated and then the process goes to step (8), otherwise it goes to stage B;

[0052] Phase B: Carbon canister valve high flow monitoring and compensation gradient measurement phase

[0053] (B1) If the fuel tank pressure rises, the compensation gradient is calculated within the set time to determine whether the compensation gradient is greater than the maximum allowable gradient. If so, the diagnosis is interrupted, and the number of interruption diagnosis is increased by 1 before entering step (7). If not, the process enters (B2). If there is severe condensation of the oil vapor in the evaporation system, it is determined whether the reduction value of the fuel tank pressure exceeds the threshold. If so, the diagnosis is interrupted, and the number of interruption diagnosis is increased by 1 before entering step (7). If not, the process enters (B2).

[0054] (B2) determining whether the fuel tank pressure is lower than the high flow diagnostic threshold of the carbon canister solenoid valve and has never exceeded the high flow diagnostic threshold within the diagnostic time; if so, reporting a carbon canister valve high flow fault, terminating the fault diagnosis and proceeding to step (8); if not, proceeding to step (B3);

[0055] (B3) Record the compensation gradient and then proceed to stage C;

[0056] Phase C: Carbon canister valve low flow diagnosis and gross leak diagnosis phase

[0057] (C1) If the desorption flow integral is greater than the low flow diagnostic integral threshold of the carbon canister solenoid valve, and the fuel tank pressure is greater than the low flow diagnostic threshold of the carbon canister solenoid valve, a carbon canister valve low flow fault is reported, and the diagnosis is terminated and the process proceeds to step (8), otherwise the process proceeds to (C2);

[0058] (C2) The fuel tank pressure continues to drop, and the pressure drop value of the fuel tank is calculated. If the desorption flow integral is greater than the gross leak diagnosis integral threshold, and the pressure drop value is higher than the gross leak diagnosis pressure difference threshold, a gross leak fault of the evaporation system is reported, and the diagnosis is terminated and the process proceeds to step (8). Otherwise, the process proceeds to (C3);

[0059] (C3) If the tank pressure reaches the set target pressure value, enter stage D;

[0060] Phase D: 1mm leakage monitoring phase

[0061] Calculate the oil tank pressure rise gradient within the set time, and subtract the compensation gradient from the oil tank pressure rise gradient to obtain the vacuum decay gradient. If the vacuum decay gradient exceeds the 1mm leakage diagnosis threshold, a 1mm leakage fault is reported, and the diagnosis is terminated and the process goes to step (8).

[0062] A further improvement of the present invention is:

[0063] During the process of evaporation system leakage fault diagnosis, it is determined in real time whether the exit working condition coordination condition is met. If yes, the fuel evaporation system leakage fault diagnosis is interrupted, and the interruption diagnosis number is increased by 1 before entering step (7). If no, it enters step (8).

[0064] A further improvement of the present invention is:

[0065] The operation of judging whether the conditions for exiting the working condition coordination are met includes: if any one of the following nine conditions is met, it is judged that the conditions for exiting the working condition coordination are met; if none of the following nine conditions is met, it is judged that the conditions for exiting the working condition coordination are not met:

[0066] The vehicle speed is greater than the interrupt diagnosis vehicle speed threshold;

[0067] The acceleration is greater than the interrupt diagnosis acceleration threshold;

[0068] The slope is greater than the interruption diagnosis slope threshold;

[0069] The SOC is lower than the interrupt diagnosis SOC threshold;

[0070] The power demanded by the driver is greater than the difference between the battery's allowable discharge power and the power reserved for exiting diagnosis;

[0071] Diagnosis: The initial pressure-maintaining process is severe with condensation, and the reduction in tank pressure exceeds the pressure drop threshold;

[0072] The compensation gradient is greater than the gradient threshold;

[0073] During the vacuuming process, the carbon canister flushing flow rate is greater than the flushing threshold;

[0074] An evaporative system fault has occurred.

[0075] A further improvement of the present invention is:

[0076] In step (7), the operation of determining whether to end the current driving cycle evaporation system diagnosis includes:

[0077] If the number of unresponsive request conditions is greater than the number threshold or the number of interrupted diagnosis is greater than the number threshold, it is determined that the current driving cycle evaporation system diagnosis is terminated; if the number of unresponsive request conditions is less than or equal to the number threshold and the number of interrupted diagnosis is less than or equal to the number threshold, it is determined that the current driving cycle evaporation system diagnosis is not terminated.

[0078] According to a second aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores at least one computer-executable program, and when the at least one program is executed by the computer, the computer executes the steps in the evaporation system leakage fault diagnosis method.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] The present invention can also perform evaporative system leakage fault diagnosis while driving, thereby increasing the diagnosis completion probability, reducing the number of driving cycle diagnosis times, and reducing NVH complaints caused by engine starting and running during parking or pre-parking (low vehicle speed). In addition, the present invention reduces the number of interrupted diagnosis times, improves the one-time diagnosis completion rate, and improves the IUPR rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a flowchart of the steps of a method for diagnosing leakage faults of an evaporation system according to the present invention;

[0082] Figure 2 It is the diagram of the evaporation system;

[0083] Figure 3 It is the interactive diagram of the diagnostic signal of the PCU evaporation system of the power system control module;

[0084] Figure 4 It is the fuel evaporation system fault diagnosis process diagram (fuel tank pressure, working condition request, carbon canister solenoid valve, AAV valve working sequence);

[0085] Figure 5 It is a driving diagnostic diagram. DETAILED DESCRIPTION

[0086] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0087] The present invention provides an evaporation system leakage fault diagnosis method, which is implemented by an existing power system controller (PCU) on a vehicle, wherein the power system controller integrates an engine controller and a vehicle controller.

[0088] The method of the present invention first collects signals, and determines whether fault diagnosis conditions and diagnostic operating condition request conditions are met based on the signals, and performs evaporation system leakage fault diagnosis after the fault diagnosis conditions and diagnostic operating condition request conditions are met; and, during the evaporation system leakage fault diagnosis process, if the exit operating condition coordination conditions are met, the diagnosis is interrupted.

[0089] like Figure 1 As shown, the method of the present invention specifically comprises the following steps:

[0090] (0) Initialization: Set the initial value of the number of non-response request conditions to 0, and set the initial value of the number of interrupt diagnosis conditions to 0;

[0091] (1) Collecting signals and determining whether the fault diagnosis conditions are met, if yes, proceeding to step (2), if no, returning to step (0);

[0092] Specifically, the operation of collecting signals in step (1) includes:

[0093] The following signals are collected: vehicle speed, acceleration, slope, power battery SOC, driver demand power, battery allowable discharge power, and engine operating status. These signals are obtained from existing vehicles using existing methods and are briefly described as follows:

[0094] like Figure 2 As shown, the fuel evaporation system in this embodiment is an existing system, which includes a fuel tank, a fuel tank pressure sensor (the fuel tank and the carbon canister are connected by a pipeline, and the pressure signals of the two can be considered consistent), a carbon canister, a carbon canister ventilation valve, and a carbon canister solenoid valve.

[0095] like Figure 3 As shown, the process of obtaining the signal is as follows:

[0096] ① PCU is connected to the fuel tank pressure sensor, accelerator pedal position sensor, oil level sensor, ambient temperature / pressure sensor, water temperature sensor, oxygen sensor, brake pedal switch (i.e. brake switch), crank position sensor (these are all existing settings on existing vehicles and will not be repeated here) through hard wires to obtain fuel tank pressure, accelerator pedal opening, oil level, ambient temperature, ambient pressure, water temperature, air-fuel ratio, brake, engine speed, and engine operating status. The engine operating status signal comes from Figure 3 The crank position sensor in the engine converts the crank position signal into a rotation speed by an existing method and determines the engine operating state when the rotation speed is greater than a certain value, and the engine operating time can be calculated according to the engine operating state.

[0097] ②The PCU receives the battery allowable discharge power and power battery SOC (state of charge) from the BMS (power battery control system) through the CAN bus (controller area network bus), the vehicle speed signal and torque request value and torque intervention signal from the ESC / ABS (anti-skid / anti-lock braking system), the adaptive cruise torque request value and cruise status signal from the RSM (intelligent driving system), and receives the drive motor output torque sent by the MCU (electric drive control system) and performs slope calculation. The calculated slope is one of the conditions for entering and exiting the diagnosis.

[0098] The signal processing process is as follows:

[0099] ① Differentiate the vehicle speed to obtain the acceleration, filter it with a filter coefficient (which can be calibrated according to actual needs) to obtain the filtered acceleration a;

[0100] ② According to the following dynamic formula, the real-time slope i is calculated, and the slope P is updated to the real-time slope i every time period (which can be calibrated according to actual needs). When the vehicle speed is lower than the threshold (which can be calibrated according to actual needs) or the brake pedal is pressed, the update to the real-time slope is prohibited, and the slope P maintains the slope value of the previous cycle.

[0101]

[0102] Among them, T tq is the output torque of the driving motor, r is the radius of the driving wheel, i g is the speed ratio of the current gear (drive motor speed ratio, range-extended P1+P4 architecture), i0 is the main reduction ratio, η T is the transmission efficiency at the current gear, G is the vehicle's gravity, f is the rolling resistance coefficient, i is the slope, C D is the drag coefficient, A is the frontal projection area of ​​the car, a is the filtered acceleration, δ is the rotation mass conversion coefficient, m is the vehicle mass, and u is the vehicle speed.

[0103] The vehicle speed comes from the vehicle speed signal sent by ESC / ABS, and the acceleration is obtained by differential filtering of the vehicle speed, G = mg, T tq It is the driving motor torque sent by MCU through CAN. The rolling radius, speed ratio, final reduction ratio, vehicle mass, rolling resistance, frontal area, drag coefficient and rotational mass conversion coefficient are vehicle parameters. They are internally calibrable quantities and the values ​​can be calibrated according to differences in vehicle models.

[0104] ③ Driver demand power: obtained from the existing driver demand and torque distribution control module of the PCU, which will not be repeated here.

[0105] Specifically, the operation of determining whether the fault diagnosis condition is met in step (1) includes: if the target vehicle satisfies the following 9 conditions at the same time (the parameters used in the following 9 conditions are all automatically collected by the PCU or converted by an existing conversion method based on the collected parameters), then it is determined that the target vehicle meets the fault diagnosis condition; if any one of the following 9 conditions is not met, then it is determined that the target vehicle does not meet the fault diagnosis condition:

[0106] ① There is no evaporation system related fault; "related fault" here refers to other faults except leakage, such as basic pressure signal fault, carbon canister solenoid valve fault, etc.;

[0107] ② The ambient temperature is within the temperature diagnostic range, and the ambient temperature diagnostic range can be calibrated according to actual needs;

[0108] ③ The ambient pressure is within the ambient pressure diagnostic range, and the ambient pressure diagnostic range can be calibrated according to actual needs;

[0109] ④ The fuel tank pressure is within the fuel tank pressure diagnostic range, and the fuel tank pressure diagnostic range can be calibrated according to actual needs;

[0110] ⑤The oil level percentage is lower than the set oil level percentage, for example 85%;

[0111] ⑥ The carbon canister load is less than the load threshold (the carbon canister load is calculated by adaptive learning of the impact of fuel vapor on the air-fuel ratio of the mixed gas during the desorption process. If the impact on the air-fuel ratio is large, the carbon canister load is considered to be large). The load threshold can be calibrated according to actual needs;

[0112] ⑦ The starting water temperature is within the starting water temperature diagnostic range and the engine running time is greater than the running time threshold. The starting water temperature diagnostic range can be calibrated according to actual needs; the running time threshold can be calibrated according to actual needs;

[0113] ⑧ Air-fuel ratio is stable. After the control enters the closed loop, the PCU performs adaptive learning on the fuel system. After the self-learning value is stable and the deviation is small, the air-fuel ratio is considered to be stable. This is the existing technology and will not be described here.

[0114] ⑨ The time interval between two diagnoses (i.e. the time interval obtained by subtracting the time of the previous diagnosis from the time of the current diagnosis) is greater than the diagnosis interval time threshold, and the diagnosis interval time threshold can be calibrated according to actual needs;

[0115] (2) determining whether the diagnostic condition is satisfied, if yes, proceeding to step (3), if no, returning to step (1);

[0116] The operations for determining whether the conditions for entering the diagnostic condition are met include:

[0117] If the following five conditions are met at the same time, it is determined that the condition for entering the diagnostic condition is met; if any one of the following five conditions is not met, it is determined that the condition for entering the diagnostic condition is not met:

[0118] ① The vehicle speed is less than the vehicle speed threshold for entering the diagnosis, and the vehicle speed threshold for entering the diagnosis can be calibrated according to actual needs;

[0119] ② The acceleration is less than the acceleration threshold for entering the diagnosis, and the acceleration threshold for entering the diagnosis can be calibrated according to actual needs;

[0120] ③ The slope is less than the entry diagnosis slope threshold, and the entry diagnosis slope threshold can be calibrated according to actual needs;

[0121] ④ The SOC is greater than the diagnostic SOC threshold, which can be calibrated according to actual needs;

[0122] ⑤ The power required by the driver is less than the difference between the battery's allowable discharge power and the power reserved for entering the diagnosis. The power reserved for entering the diagnosis can be calibrated according to actual needs.

[0123] (3) determining whether the priority of the evaporative system diagnostic working condition request is the highest; if so, sending a working condition coordination request signal, a working condition request engine speed (which can be calibrated according to actual needs), a working condition request engine torque (which can be calibrated according to actual needs), and a working condition coordination request priority (which can be calibrated according to actual needs) to the PCU (e.g., a hybrid power mode coordination and torque calculation module in the PCU), and then proceeding to step (4); if not, returning to step (1);

[0124] In existing vehicles, different priorities are set for different working condition requests. When the existing working condition coordination module in the PCU (such as the working condition coordination request arbitration module) receives multiple working condition requests, it will compare the priorities of each working condition request, that is, arbitrate the working condition coordination requests from all system diagnoses. For example, if the priority of evaporative system leakage diagnosis is set higher than that of post-oxygen diagnosis, an evaporative system working condition coordination request will be issued instead of a working condition request for post-oxygen sensor diagnosis. These are all existing technologies and will not be repeated here.

[0125] (4) issuing an evaporation system diagnostic working condition request: the existing working condition coordination request module in the PCU issues an evaporation system diagnostic working condition request to the existing hybrid mode coordination and torque calculation module in the PCU;

[0126] (5) Determine whether to respond to the diagnostic condition request. If yes, proceed to step (6). If not, increase the number of non-response request conditions by 1 (i.e., the cumulative number of non-response request conditions), and then proceed to step (7).

[0127] Specifically, the existing hybrid mode coordination and torque calculation module in the PCU determines whether to respond to the diagnostic condition request. The operation of determining whether to respond to the diagnostic condition request includes:

[0128] Determine whether the priority of the operating condition coordination request is the highest. If so, determine to respond to the diagnostic operating condition request. If not, determine whether the response conditions are met. If so, determine to respond to the diagnostic operating condition request. If not, determine not to respond to the diagnostic operating condition request.

[0129] The operation of determining whether the response condition is met includes:

[0130] If the following three conditions are met at the same time, the response condition is determined to be met; if any of the following three conditions is not met, the response condition is determined to be not met:

[0131] ① The slope P is less than the slope threshold, and the slope threshold can be calibrated according to actual needs;

[0132] ② The SOC is greater than the SOC threshold, and the SOC threshold can be calibrated according to actual needs;

[0133] ③ The power required by the driver is less than the difference between the allowable discharge power of the battery and the reserved power. The reserved power can be calibrated according to actual needs.

[0134] (6) Performing coordinated response to the operating conditions and then conducting evaporation system leakage fault diagnosis, i.e., evaporation system fault diagnosis;

[0135] The operation of performing coordinated response to working conditions includes:

[0136] Control the engine speed and torque to reach the engine speed and engine torque required by the working condition. The specific process is as follows:

[0137] ① Send a start request (if the engine is not running, a start request is sent; if the engine is running, a signal prohibiting engine shutdown is sent to ensure that the engine is running for diagnosis) and a working condition request for engine torque to the engine torque control module in the PCU. The engine torque control module drives and controls the engine to start (if the engine is not running, the injection ignition is controlled) and controls the electronic throttle opening to make the engine torque reach the working condition request for engine torque;

[0138] ② Send the generator speed request (equal to the operating condition requested engine speed multiplied by the generator speed ratio) to the MCU (motor control system), and the MCU controls the generator to respond to the speed request to achieve the operating condition requested generator speed.

[0139] Specifically, Figure 4As shown, the operation of evaporation system leakage fault diagnosis includes 4 stages:

[0140] Phase A: Carbon canister vent valve monitoring and tank pressure stabilization phase

[0141] After the fault diagnosis starts, the carbon canister solenoid valve is closed, and the atmosphere enters the fuel tank through the open carbon canister ventilation valve, and the fuel tank pressure rises. If the fuel tank pressure does not reach the ambient pressure (that is, it is basically consistent with the ambient pressure within the ventilation valve diagnosis time (which can be calibrated according to actual needs) (that is, it is basically consistent with the ambient pressure, but it cannot be completely consistent due to pressure sensor manufacturing deviation and other reasons), that is, when the fuel tank pressure is lower than the ventilation valve diagnosis pressure threshold, the carbon canister ventilation valve stuck closed fault is reported. If the ventilation valve stuck closed fault is detected (it can be known from the fuel tank pressure sensor that when stuck closed, the inside of the fuel tank will be in a negative pressure state), the fault diagnosis is terminated and then transferred to step (8), otherwise it enters stage B. The termination of diagnosis due to the reporting of the fault will not accumulate the number of interrupted diagnosis times, and no diagnosis will be performed again in this driving cycle.

[0142] Phase B: Carbon canister valve high flow monitoring and compensation gradient measurement phase

[0143] After the fuel tank pressure returns to the ambient pressure (the pressure measured by the ambient pressure sensor during diagnosis) for a certain period of time (which can be calibrated according to actual needs), the carbon canister ventilation valve is closed and the entire evaporation system is in a sealed state. At this time, the following judgments and treatments are performed:

[0144] (B1) If the fuel tank pressure rises due to the evaporation of the fuel, then within the set time (which can be calibrated according to actual needs), calculate the rising gradient of the fuel tank pressure, that is, the compensation gradient, and determine whether the compensation gradient is greater than the maximum allowable gradient (which can be calibrated according to actual needs). If so, interrupt the diagnosis, increase the number of interruptions by 1 (that is, the cumulative number of interruptions) and enter step (7). If not, enter (B2); If there is severe condensation of the oil vapor in the evaporation system, determine whether the reduction value of the fuel tank pressure exceeds the threshold value (which can be calibrated according to actual needs). If so, interrupt the diagnosis, increase the number of interruptions by 1 and enter step (7). If not, enter (B2);

[0145] (B2) determining whether the fuel tank pressure is lower than a high flow diagnostic threshold value (which can be calibrated according to actual needs) of the carbon canister solenoid valve and has never exceeded the threshold value within the diagnostic time (which can be calibrated according to actual needs); if so, reporting a carbon canister valve high flow fault (such as normally open stuck), terminating the fault diagnosis and proceeding to step (8); if not, proceeding to step (B3);

[0146] (B3) recording the compensation gradient, which is used to correct the vacuum decay gradient calculated in stage D, and then entering stage C;

[0147] Phase C: Carbon canister valve low flow diagnosis and gross leak diagnosis phase

[0148] Keep the carbon canister ventilation valve closed, open the carbon canister solenoid valve, establish negative pressure in the fuel tank system (i.e., perform vacuum pumping), and then perform the following operations:

[0149] (C1) If the desorption flow integral (calculated by the engine operating conditions during oil and gas desorption, the carbon canister solenoid valve opening, the desorption time, etc., which is an existing method and will not be repeated here) is greater than the low flow diagnosis integral threshold of the carbon canister solenoid valve, and the fuel tank pressure is greater than the low flow diagnosis threshold of the carbon canister solenoid valve, then a carbon canister valve low flow fault (for example, low load desorption pipeline blockage, disconnection, or carbon canister valve normally closed stuck) is reported, and the diagnosis is terminated and the process goes to step (8), otherwise it goes to (C2);

[0150] (C2) The fuel tank pressure continues to drop, and the pressure drop value of the fuel tank is calculated. If the desorption flow integral is greater than the gross leak diagnosis integral threshold (which can be calibrated according to actual needs), and the pressure drop value is higher than the gross leak diagnosis pressure difference threshold (which can be calibrated according to actual needs), then a gross leak fault of the evaporation system is reported, and the diagnosis is terminated and the process proceeds to step (8), otherwise it proceeds to (C3);

[0151] (C3) If the tank pressure reaches the set target pressure value (which can be calibrated according to actual needs), enter stage D.

[0152] Phase D: 1mm leakage monitoring phase

[0153] Close the canister valve, keep the canister vent valve closed, calculate the tank pressure rise gradient within the set time (which can be calibrated according to actual needs), and subtract the compensation gradient obtained in stage B from the tank pressure rise gradient to obtain the vacuum decay gradient. If the vacuum decay gradient exceeds the 1mm leak diagnosis threshold (which can be calibrated according to actual needs), a 1mm leak fault is reported, and the diagnosis is terminated and the process goes to step (8).

[0154] Furthermore, in addition to the above-mentioned interruption or termination of diagnosis (exit from working condition coordination), in the process of evaporation system leakage fault diagnosis (i.e., the four diagnostic processes ABCD), the present invention also determines in real time whether the exit from working condition coordination condition is met. If so, the fuel evaporation system leakage fault diagnosis is interrupted, and the number of interruption diagnosis is increased by 1 before entering step (7). If not, the process enters step (8).

[0155] Specifically, the operation of determining whether the conditions for exiting the working condition coordination are met includes: if any one of the following nine conditions is met, it is determined that the conditions for exiting the working condition coordination are met; if none of the following nine conditions are met, it is determined that the conditions for exiting the working condition coordination are not met:

[0156] ① The vehicle speed is greater than the interrupt diagnosis vehicle speed threshold, which can be calibrated according to actual needs;

[0157] ② The acceleration is greater than the interrupt diagnosis acceleration threshold, and the interrupt diagnosis acceleration threshold can be calibrated according to actual needs;

[0158] ③ The slope is greater than the interruption diagnosis slope threshold, and the interruption diagnosis slope threshold can be calibrated according to actual needs;

[0159] ④ The SOC is lower than the interrupt diagnosis SOC threshold, and the interrupt diagnosis SOC threshold can be calibrated according to actual needs;

[0160] ⑤ The driver's required power is greater than the difference between the battery's allowable discharge power and the exit diagnosis reserved power, and the exit diagnosis reserved power can be calibrated according to actual needs;

[0161] ⑥ During the initial pressure maintenance process of diagnosis, condensation is severe and the reduction value of the oil tank pressure exceeds the pressure drop threshold value. The pressure drop threshold value can be calibrated according to actual needs;

[0162] ⑦ Diagnose that the evaporation is intense during the initial pressure holding process, and the compensation gradient is greater than the gradient threshold. The gradient threshold can be calibrated according to actual needs;

[0163] ⑧ During the vacuuming (gross leak diagnosis) process, the carbon canister flushing flow rate is greater than the flushing threshold value, and the flushing threshold value can be calibrated according to actual needs;

[0164] ⑨An evaporation system failure occurs.

[0165] (7) Determine whether the evaporation system diagnosis of the current driving cycle (the starting and ending points of the current driving cycle are from the activation of the drive system to the deactivation of the drive system) has ended. If so, proceed to step (8); if not, return to step (0).

[0166] The operations for determining whether to end the evaporative system diagnosis for the current driving cycle include:

[0167] If the number of unresponsive request conditions is greater than the number threshold or the number of interrupted diagnosis is greater than the number threshold, it is determined that the current driving cycle evaporation system diagnosis is terminated; if the number of unresponsive request conditions is less than or equal to the number threshold and the number of interrupted diagnosis is less than or equal to the number threshold, it is determined that the current driving cycle evaporation system diagnosis is not terminated.

[0168] (8)End.

[0169] The beneficial effects of the present invention are verified by an embodiment below:

[0170] like Figure 5As shown, in stage ①, the PCU determines whether all fault diagnosis conditions are met; in stage ②, the PCU enters the diagnostic condition, controls the engine to reach the condition request speed and condition request torque, and then starts the evaporation system leakage diagnosis from ② to ⑤; during the diagnostic process from ② to ⑤, if the acceleration is not greater than the interruption diagnosis acceleration threshold and there is no fault in the diagnostic process, then it enters stage ⑥, completes the diagnosis, exits the condition coordination, and ends the diagnosis.

[0171] Figure 4 This is a schematic diagram of the theoretical diagnostic process. Figure 5 This is a diagram of the actual vehicle application diagnostic process. Figure 5 Stages ② to ⑤ in the figure correspond to the aforementioned stages A to D. Figure 5 In the process, ① corresponds to the aforementioned steps (1) to (4), and after judging whether the diagnosis conditions and the working condition request conditions are met and confirming the working condition priority, a working condition request is made. After requesting the working condition, enter ② to ⑤, and judge whether to respond to the working condition request. If so, respond to the working condition request and start diagnosis. Figure 5 ② to ⑤ in the figure correspond to the above steps (5) to (7). After the diagnosis is completed, proceed to ⑥, which corresponds to step (8).

[0172] Figure 4 The diagnostic process in is the existing diagnostic logic (i.e. the above four stages A to D are all existing technologies, but interrupt diagnosis is not introduced in the current four stages). This logic can only be run in static state (i.e. the vehicle speed is 0) because it is affected by the fluctuation of the fuel tank liquid level and other factors on the diagnostic accuracy.

[0173] The present invention adds a series of diagnostic and diagnostic working condition request conditions (the present invention adds interruption diagnosis conditions in the four stages A to D, such as the above-mentioned acceleration, vehicle speed, SOC and other conditions, and also determines whether the driving state meets the entry diagnosis conditions, such as vehicle speed, acceleration, slope, etc., before the diagnostic working condition coordination request), to the greatest extent possible limit the diagnostic process to the working conditions with small fluid level fluctuations, reduce the impact of tank fluid level fluctuations on diagnosis during driving, realize driving diagnosis, and avoid the limitations of static diagnosis (because static diagnosis can only be completed when the vehicle speed is 0 or in the pre-parking state, which will cause NVH complaints). For hybrid vehicles, it also avoids the bad driving experience caused by starting the engine for diagnosis at a static state.

[0174] Moreover, the present invention ensures the stability of the engine operating condition during diagnosis by introducing the exit operating condition coordination condition, improves the diagnosis completion rate and reduces the occurrence of misdiagnosis under variable operating conditions; by adding SOC, acceleration, slope, driver power demand and other entry diagnostic condition request conditions, the system does not enter diagnosis in scenarios such as low SOC, high driver power demand, climbing, and intense driving, thereby improving the accuracy of diagnosis; by introducing new interruption diagnosis conditions such as SOC, acceleration, slope, and driver power demand, it ensures that misdiagnosis does not occur during the diagnosis process, improves the accuracy of driving diagnosis, and further reduces the number of interruption diagnosis times, and ensures the completion rate of driving diagnosis through the interruption diagnosis number threshold; by introducing a driving diagnosis method, the limitations of static diagnosis are avoided.

[0175] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A method for diagnosing leakage faults in an evaporation system, characterized in that: The method first collects signals, and determines whether fault diagnosis conditions and diagnostic operating condition request conditions are met based on the signals, and performs evaporation system leakage fault diagnosis after the fault diagnosis conditions and diagnostic operating condition request conditions are met; and during the evaporation system leakage fault diagnosis process, if the exit operating condition coordination condition is met, the diagnosis is interrupted.

2. The evaporation system leakage fault diagnosis method according to claim 1, characterized in that: The method comprises: (0) Initialization: Set the initial value of the number of non-response request conditions to 0, and set the initial value of the number of interrupt diagnosis conditions to 0; (1) Collecting signals and determining whether the fault diagnosis conditions are met, if yes, proceeding to step (2), if no, returning to step (0); (2) determining whether the diagnostic condition is satisfied, if yes, proceeding to step (3), if no, returning to step (1); (3) determining whether the priority of the evaporative system diagnostic operating condition request is the highest; if so, sending an operating condition coordination request signal, an operating condition request engine speed, an operating condition request engine torque, and an operating condition coordination request priority, and then proceeding to step (4); if not, returning to step (1); (4) Sending a request for evaporation system diagnostic status; (5) Determine whether to respond to the diagnostic condition request. If yes, proceed to step (6). If not, increase the number of non-response request conditions by 1, and then proceed to step (7). (6) Coordinate the response to the operating conditions and then perform evaporation system leakage fault diagnosis; (7) determining whether to end the evaporative system diagnosis for the current driving cycle; if so, proceeding to step (8); if not, returning to step (0); (8)End.

3. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (1), the operation of determining whether the fault diagnosis condition is met includes: if the following nine conditions are met at the same time, it is determined that the fault diagnosis condition is met; if any one of the following nine conditions is not met, it is determined that the fault diagnosis condition is not met: There are no evaporation system related faults; The ambient temperature is within the temperature diagnosis range; The environmental pressure is within the environmental pressure diagnostic range; The fuel tank pressure is within the fuel tank pressure diagnostic range; The oil level percentage is lower than the set oil level percentage; The carbon canister load is less than the load threshold; The starting water temperature is within the starting water temperature diagnostic range and the engine running time is greater than the running time threshold; Stable air-fuel ratio; The time interval between two diagnoses is greater than the diagnostic interval threshold.

4. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (2), the operation of determining whether the condition for entering the diagnostic operating condition is met includes: If the following five conditions are met at the same time, it is determined that the condition for entering the diagnostic condition is met; if any one of the following five conditions is not met, it is determined that the condition for entering the diagnostic condition is not met: The vehicle speed is lower than the diagnostic speed threshold; The acceleration is less than the diagnostic acceleration threshold; The slope is less than the diagnostic slope threshold; The SOC is greater than the diagnostic SOC threshold; The power required by the driver is less than the difference between the battery's allowable discharge power and the power reserved for entering diagnosis.

5. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (5), the operation of determining whether to respond to the diagnostic condition request includes: Determine whether the priority of the operating condition coordination request is the highest. If so, determine to respond to the diagnostic operating condition request. If not, determine whether the response conditions are met. If so, determine to respond to the diagnostic operating condition request. If not, determine not to respond to the diagnostic operating condition request.

6. The evaporation system leakage fault diagnosis method according to claim 5, characterized in that: The operations for determining whether the response conditions are met include: If the following three conditions are met at the same time, the response condition is determined to be met; if any of the following three conditions is not met, the response condition is determined to be not met: The slope is less than the slope threshold; SOC is greater than the SOC threshold; The power required by the driver is less than the difference between the battery's allowable discharge power and the reserved power.

7. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (6), the operation of coordinating the operating condition response includes: controlling the engine speed and torque to reach the operating condition requested engine speed and the operating condition requested engine torque.

8. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (6), the operation of diagnosing the leakage fault of the evaporation system includes: Phase A: Carbon canister vent valve monitoring and tank pressure stabilization phase If the ventilation valve stuck closed fault is detected, the fault diagnosis is terminated and then the process goes to step (8), otherwise it goes to stage B; Phase B: Carbon canister valve high flow monitoring and compensation gradient measurement phase (B1) If the fuel tank pressure rises, the compensation gradient is calculated within the set time to determine whether the compensation gradient is greater than the maximum allowable gradient. If so, the diagnosis is interrupted, and the number of interruption diagnosis is increased by 1 before entering step (7). If not, the process enters (B2). If there is severe condensation of the oil vapor in the evaporation system, it is determined whether the reduction value of the fuel tank pressure exceeds the threshold. If so, the diagnosis is interrupted, and the number of interruption diagnosis is increased by 1 before entering step (7). If not, the process enters (B2). (B2) determining whether the fuel tank pressure is lower than the high flow diagnostic threshold of the carbon canister solenoid valve and has never exceeded the high flow diagnostic threshold within the diagnostic time; if so, reporting a carbon canister valve high flow fault, terminating the fault diagnosis and proceeding to step (8); if not, proceeding to step (B3); (B3) Record the compensation gradient and then proceed to stage C; Phase C: Carbon canister valve low flow diagnosis and gross leak diagnosis phase (C1) If the desorption flow integral is greater than the low flow diagnostic integral threshold of the carbon canister solenoid valve, and the fuel tank pressure is greater than the low flow diagnostic threshold of the carbon canister solenoid valve, a carbon canister valve low flow fault is reported, and the diagnosis is terminated and the process proceeds to step (8), otherwise the process proceeds to (C2); (C2) The fuel tank pressure continues to drop, and the pressure drop value of the fuel tank is calculated. If the desorption flow integral is greater than the gross leak diagnosis integral threshold, and the pressure drop value is higher than the gross leak diagnosis pressure difference threshold, a gross leak fault of the evaporation system is reported, and the diagnosis is terminated and the process proceeds to step (8). Otherwise, the process proceeds to (C3); (C3) If the tank pressure reaches the set target pressure value, enter stage D; Phase D: 1mm leakage monitoring phase Calculate the tank pressure rise gradient within the set time, and subtract the compensation gradient from the tank pressure rise gradient to obtain the vacuum decay gradient. If the vacuum decay gradient exceeds the 1mm leakage diagnosis threshold, a 1mm leakage fault is reported, and the diagnosis is terminated and the process goes to step (8).

9. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: During the process of evaporation system leakage fault diagnosis, it is determined in real time whether the exit working condition coordination condition is met. If yes, the fuel evaporation system leakage fault diagnosis is interrupted, and the interruption diagnosis number is increased by 1 before entering step (7). If no, it enters step (8).

10. The evaporation system leakage fault diagnosis method according to claim 9, characterized in that: The operation of judging whether the conditions for exiting the working condition coordination are met includes: if any one of the following nine conditions is met, it is judged that the conditions for exiting the working condition coordination are met; if none of the following nine conditions is met, it is judged that the conditions for exiting the working condition coordination are not met: The vehicle speed is greater than the interrupt diagnosis vehicle speed threshold; The acceleration is greater than the interrupt diagnosis acceleration threshold; The slope is greater than the interruption diagnosis slope threshold; The SOC is lower than the interrupt diagnosis SOC threshold; The power demanded by the driver is greater than the difference between the battery's allowable discharge power and the power reserved for exiting diagnosis; Diagnosis: The initial pressure-maintaining process is severe with condensation, and the reduction in tank pressure exceeds the pressure drop threshold; The compensation gradient is greater than the gradient threshold; During the vacuuming process, the carbon canister flushing flow rate is greater than the flushing threshold; An evaporative system fault has occurred.

11. The evaporation system leakage fault diagnosis method according to claim 2, characterized in that: In step (7), the operation of determining whether to end the current driving cycle evaporation system diagnosis includes: If the number of unresponsive request conditions is greater than the number threshold or the number of interrupted diagnosis is greater than the number threshold, it is determined that the current driving cycle evaporation system diagnosis is terminated; if the number of unresponsive request conditions is less than or equal to the number threshold and the number of interrupted diagnosis is less than or equal to the number threshold, it is determined that the current driving cycle evaporation system diagnosis is not terminated.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores at least one computer-executable program, and when the at least one program is executed by the computer, the computer executes the steps of the evaporation system leakage fault diagnosis method according to any one of claims 1 to 11.

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