Fuel Evaporation System Fault Diagnosis Method

Abstract

The present invention relates to the technical field of automotive fault diagnosis methods, and specifically refers to a fuel evaporation system fault diagnosis method. A first pressure sensor, a second pressure sensor and a number of solenoid valves are added to the fuel evaporation system; the following steps are carried out: S1. Adjust the solenoid valve, collect the pressure value P11 of the first pressure sensor, and judge whether there is a fault of the flushing valve being stuck or the connecting pipe leaking. If not, collect the pressure value P12 of the second pressure sensor and judge whether there is a fault of the carbon canister being blocked. If not, proceed to the next step; S2. Adjust the solenoid valve, collect the pressure value P21 of the first pressure sensor, and judge whether there is a fault of the vent pipe leaking or the circulation pipe leaking. If not, proceed to the next step; S3. Adjust the solenoid valve, collect the pressure value P31 of the first pressure sensor, and judge whether there is a fault of the fuel tank leaking based on P31. If not, it proves that the fuel evaporation system is normal. The method of the present invention is simple and the fault diagnosis is accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive fault diagnosis methods, and specifically refers to a fuel evaporation system fault diagnosis method. Background Art

[0002] The "Emission Limits and Measurement Methods for Light-Duty Vehicles (Phase VI)" (hereinafter referred to as the National VI Standard) issued in China makes strict regulations on leakage detection: fuel vehicles must be equipped with a fuel evaporation system leakage diagnosis device that can monitor in real time, and check whether there is a leakage hole with a cumulative diameter greater than 1 mm in the fuel evaporation system once in each fault detection cycle. The National VI Standard requires that vehicles sold in the Chinese region must meet the requirements of this regulation starting from July 1, 2020, while the United States and the European Union implemented the control of vehicle evaporative pollutant emissions earlier.

[0003] If classified from the perspective of pressure control, the current mainstream solutions for fuel evaporation leakage diagnosis are natural pressure, positive pressure, and negative pressure. As a typical positive pressure detection method, DMTL (Diagnostic Module Tank Leakage) has the advantages of fast detection speed and high detection accuracy, and is a product with a relatively high installation ratio in the domestic and foreign markets.

[0004] Using the DMTL method to detect leakage adds a DMTL hardware module to the fuel evaporation system. The system schematic diagram is as Figure 1 shown, including a fuel tank, a carbon canister, a DMTL module, and an intake manifold. A fuel filling pipe is provided on the fuel tank. The fuel tank is connected to the adsorption port of the carbon canister through a ventilation pipe. The desorption port of the carbon canister is connected to the intake manifold through a connecting pipe. A flushing valve is provided between the connecting pipe and the intake manifold. The diagnostic port of the carbon canister is connected to the DMTL module through a communication pipe. A filter is provided on the side of the DMTL module away from the carbon canister.

[0005] The DMTL module includes an electric vacuum pump, a switching valve, and a reference hole (throttle hole). The engine electronic control unit controls the electric pump and the switching valve separately according to the usage needs. When the DMTL module works, the electric vacuum pump injects gas into the fuel evaporation system, and diagnoses the fuel evaporation system by obtaining the current change of the electric vacuum pump or the pressure change in the evaporation system to determine whether there is a leakage, but this diagnosis cannot determine the location where the fault occurs. The determination of the fault location can provide great convenience for the cause analysis and repair of fuel evaporation system faults. Therefore, how to realize the cause analysis of faults and the determination of fault locations under the premise of controllable costs has positive significance. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies of the above background art and provide a fuel evaporation system fault diagnosis method.

[0007] The technical solution of the present invention is: a method for diagnosing faults in a fuel evaporation system. The fuel evaporation system includes a fuel tank, a carbon canister, a DMTL module, and an intake manifold. A fuel filling pipe is installed on the fuel tank, and the fuel tank is connected to the adsorption port of the carbon canister through a ventilation pipe. The desorption port of the carbon canister is connected to the intake manifold through a connecting pipe. A flushing valve is provided at the connection between the intake manifold and the connecting pipe. The diagnostic port of the carbon canister is connected to the DMTL module through a communicating pipe. The ventilation pipe is connected to the fuel filling pipe through a circulation pipe.

[0008] It further includes a first pressure sensor installed on the communicating pipe, a second pressure sensor installed on the connecting pipe, a first solenoid valve installed on the ventilation pipe between the circulation pipe and the carbon canister, a second solenoid valve installed on the ventilation pipe between the circulation pipe and the fuel tank, and a third solenoid valve installed on the circulation pipe.

[0009] The diagnostic method is carried out according to the following steps:

[0010] S1. Close the flushing valve and the first solenoid valve, open the second solenoid valve and the third solenoid valve. The DMTL module injects gas into the fuel evaporation system, collect the pressure value P11 of the first pressure sensor, and based on P11, judge whether there is a fault of flushing valve jamming or connecting pipe leakage. If not, collect the pressure value P12 of the second pressure sensor, and compare P11 and P12 to judge whether there is a fault of carbon canister blockage. If not, proceed to the next step.

[0011] S2. Open the first solenoid valve, close the flushing valve, the second solenoid valve and the third solenoid valve. The DMTL module injects gas into the fuel evaporation system, collect the pressure value P21 of the first pressure sensor, and based on P21, judge whether there is a fault of ventilation pipe leakage or circulation pipe leakage. If not, proceed to the next step.

[0012] S3. Close the flushing valve, open the first solenoid valve, the second solenoid valve and the third solenoid valve. The DMTL module injects gas into the fuel evaporation system, collect the pressure value P31 of the first pressure sensor, and based on P31, judge whether there is a fault of fuel tank leakage. If not, it proves that the fuel evaporation system is normal.

[0013] According to a method for diagnosing faults in a fuel evaporation system provided by the present application, in the step S1, the method for judging whether there is a fault of flushing valve jamming or connecting pipe leakage based on P11 includes: comparing the pressure value P11 of the first pressure sensor with a set pressure value Pref. If P11 < Pref, it is judged that there is a fault of flushing valve jamming or connecting pipe leakage; if P11 ≥ Pref, it is judged that there is no fault of flushing valve jamming or connecting pipe leakage at present.

[0014] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S1, to determine whether there is a fault of carbon canister blockage by comparing P11 and P12: compare P11 with P12. If (P11 - P12) / P11 > a, it is determined that there is a current fault of carbon canister blockage; if (P11 - P12) / P11 ≤ a, it is determined that there is no current fault of carbon canister blockage.

[0015] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S2, the method for determining whether there is a fault of vent pipe leakage or circulation pipe leakage based on P21 includes: compare the pressure value P21 of the first pressure sensor with the set pressure value Pref. If P21 < Pref, it is determined that there is a fault of vent pipe leakage or circulation pipe leakage; if P21 ≥ Pref, it is determined that there is no current fault of vent pipe leakage or circulation pipe leakage.

[0016] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S3, the method for determining whether there is a fault of fuel tank leakage based on P31 includes: compare the pressure value P31 of the first pressure sensor with the set pressure value Pref. If P31 < Pref, it is determined that there is a fault of fuel tank leakage; if P31 ≥ Pref, it is determined that there is no current fault of fuel tank leakage.

[0017] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S1, close the flushing valve and the first solenoid valve, open the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the working current I11 of the air pump in the DMTL module, compare I11 with the set current value Iref. If I11 < Iref, it is determined that there is a fault of flushing valve jamming or connecting pipe leakage; if I11 ≥ Iref, it is determined that there is no current fault of flushing valve jamming or connecting pipe leakage.

[0018] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S2, open the first solenoid valve, close the flushing valve, the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the working current I21 of the air pump in the DMTL module, compare I21 with the set current value Iref. If I21 < Iref, it is determined that there is a fault of vent pipe leakage or circulation pipe leakage; if I21 ≥ Iref, it is determined that there is no current fault of vent pipe leakage or circulation pipe leakage.

[0019] According to a fuel evaporation system fault diagnosis method provided by the present application, in step S3, the flushing valve is closed, the first solenoid valve, the second solenoid valve and the third solenoid valve are opened, the DMTL module injects gas into the fuel evaporation system, the working current I31 of the air pump in the DMTL module is collected, and I31 is compared with the set current value Iref. If I31 < Iref, it is determined that there is a fuel tank leakage fault; if I31 ≥ Iref, it is determined that there is no fuel tank leakage fault at present.

[0020] According to a fuel evaporation system fault diagnosis method provided by the present application, the set pressure value Pref is the normal working pressure of the air pump in the DMTL module when the fuel evaporation system has no faults.

[0021] According to a fuel evaporation system fault diagnosis method provided by the present application, the set current value Iref is the normal working current of the air pump in the DMTL module when the fuel evaporation system has no faults.

[0022] The advantages of the present application are as follows:

[0023] 1. By integrating two groups of pressure sensors and three groups of solenoid valves on the fuel evaporation system, the present application uses the opening and closing of the solenoid valves to control the on-off of the internal pipeline of the entire fuel evaporation system, isolates the main components in the fuel evaporation system, and then judges the location where the fault occurs in the current fuel evaporation system and obtains the fault situation through the pressure data of the pressure sensor or the working current of the air pump in the DMTL module, which is convenient for subsequent fault analysis, detection and maintenance of the fuel evaporation system, and can also effectively avoid false fault alarms;

[0024] 2. When judging whether there is a fault of flushing valve jamming or connecting pipe leakage in the first step, the present application closes the flushing valve and the first solenoid valve to isolate the passages leading to the fuel tank and the fuel pipe, so that the gas injection of the DMTL module can only enter the carbon canister part and the intake manifold part, and compares the pressure of this part with the set pressure value, then the fault of flushing valve jamming or connecting pipe leakage can be accurately judged;

[0025] 3. In the first step of judgment, the present application judges whether the carbon canister is blocked by comparing the pressure values of the two pressure sensors before and after the carbon canister. If the difference between the two pressure values is large, it indicates that the carbon canister is blocked, and the judgment process and method are simple and effective;

[0026] 4. In the second step of this application, it is judged whether there is a fault of vent pipe leakage or circulation pipe leakage. By opening the first solenoid valve and closing the flushing valve, the second solenoid valve and the third solenoid valve, except for the fuel tank, the rest of the fuel evaporation system is unobstructed. The purpose of this step of detection is to judge the tightness of the vent pipe and the circulation pipe. After the DMTL module pressurizes and injects gas, the pressure of the first pressure sensor is collected and compared with the set pressure value, so as to accurately judge whether there is a leakage in the current passage. Since the possibilities of flushing valve jamming, connecting pipe leakage and carbon canister blockage have been excluded in the first step, if a fault occurs, it can only be vent pipe leakage or circulation pipe leakage. The judgment process and method are simple and effective.

[0027] 5. In the third step of this application, it is judged whether there is a fault of fuel tank leakage. By closing the flushing valve and opening the first solenoid valve, the second solenoid valve and the third solenoid valve, the entire fuel evaporation system forms a passage. After the DMTL module pressurizes and injects gas, the pressure of the first pressure sensor is collected and compared with the set pressure value, so as to accurately judge whether there is a leakage in the current passage. Since the possibilities of other parts of the fuel evaporation system having faults have been excluded in the previous two steps, if a fault occurs, it can only be fuel tank leakage. The judgment process and method are simple and effective.

[0028] 6. When judging whether there is a fault of flushing valve jamming or connecting pipe leakage in the first step of this application, it can not only be judged by the pressure value, but also by comparing the working current of the air pump of the DMTL module with the set current value. Compared with the method of detecting by using a pressure sensor, the current judgment method has less investment and faster detection.

[0029] 7. When judging whether there is a fault of vent pipe leakage or circulation pipe leakage in the second step of this application, the working current of the air pump of the DMTL module can also be collected and compared with the set current value for judgment. This judgment mode can obtain the judgment result without adding a pressure sensor, or compare it with the result monitored by the pressure sensor to enhance the accuracy and reliability of the fault judgment result.

[0030] 8. When judging whether there is a fault of fuel tank leakage in the third step of this application, the working current of the air pump of the DMTL module can also be collected and compared with the set current value for comparison and judgment. The judgment method is simple, has less investment, and the result can be obtained quickly.

[0031] 9. Based on the structural characteristics of the fuel evaporation system, this application selects an empirical value as the set pressure value, which improves the efficiency and accuracy of fault judgment.

[0032] 10. Based on the structural characteristics of the fuel evaporation system and the normal working condition of the air pump of the DMTL module, this application selects an empirical value as the set current value, which improves the efficiency and accuracy of fault judgment.

[0033] This application adds a solenoid valve and a pressure sensor to the fuel evaporation system. By controlling the opening and closing of the solenoid valve, the fuel evaporation system is divided into three independent spaces for separate diagnosis, thereby realizing the judgment of the fault location and the diagnosis of different fault causes, providing great convenience for the further analysis, detection and repair of subsequent faults, and having great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : Schematic structural diagram of the existing fuel evaporation system;

[0035] Figure 2 : Schematic structural diagram of the fuel evaporation system of this application;

[0036] Figure 3 : Schematic diagram of the fault diagnosis process of this application;

[0037] Among them: 1 - fuel tank; 2 - carbon canister; 3 - DMTL module; 4 - intake manifold; 5 - fuel filler pipe; 6 - vent pipe; 7 - connecting pipe; 8 - flushing valve; 9 - communicating pipe; 10 - filter; 11 - circulation pipe;

[0038] 12 - first pressure sensor; 13 - second pressure sensor; 14 - first solenoid valve; 15 - second solenoid valve; 16 - third solenoid valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The embodiments of the present invention will be described in detail below, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as a limitation of the present invention.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0041] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] This application relates to a method for diagnosing faults in a fuel evaporation system, the purpose of which is to accurately diagnose faults in the fuel evaporation system. The current fuel evaporation system is as Figure 1 shown, including a fuel tank 1, a carbon canister 2, a DMTL module 3, and an intake manifold 4. A fuel filling pipe 5 is installed on the fuel tank 1. The fuel tank 1 is connected to the adsorption port of the carbon canister 2 through a ventilation pipe 6. The desorption port of the carbon canister 2 is connected to the intake manifold 4 through a connecting pipe 7. A flushing valve 8 is provided at the connection between the intake manifold 4 and the connecting pipe 7. The diagnostic port of the carbon canister 2 is connected to the DMTL module 3 through a communication pipe 9. The ventilation pipe 6 is connected to the fuel filling pipe 5 through a circulation pipe 11. The DMTL module 3 includes an air pump, a switching valve, and a reference orifice (throttle orifice). During fault diagnosis, the air pump of the DMTL module 3 pressurizes and injects gas into the fuel evaporation system. A filter 10 is provided on the side of the DMTL module 3 away from the communication pipe 9.

[0044] In order to accurately diagnose faults in the fuel evaporation system, this application has improved the fuel evaporation system, as Figure 2 shown. The improved fuel evaporation system includes a first pressure sensor 12 installed on the communication pipe 9, a second pressure sensor 13 installed on the connecting pipe 7, a first solenoid valve 14 installed on the ventilation pipe 6 between the circulation pipe 11 and the carbon canister 2, a second solenoid valve 15 installed on the ventilation pipe 6 between the circulation pipe 11 and the fuel tank 1, and a third solenoid valve 16 installed on the circulation pipe 11.

[0045] The first solenoid valve 14 can control the on-off of the ventilation pipe 6 between the carbon canister 2 and the fuel tank 1. The second solenoid valve 15 can control the on-off of the ventilation pipe 6 between the circulation pipe 11 and the fuel tank 1. The third solenoid valve 16 can control the on-off of the circulation pipe 11. The first pressure sensor 12 can measure the pressure value in the communication pipe 9. The second pressure sensor 13 can measure the pressure value in the connecting pipe 7.

[0046] Specifically, the method for diagnosing faults in the fuel evaporation system of this application is carried out according to the following steps:

[0047] S1. Close the flushing valve 8 and the first solenoid valve 14, open the second solenoid valve 15 and the third solenoid valve 16. The DMTL module 3 injects gas into the fuel evaporation system, collects the pressure value P11 of the first pressure sensor 12, and determines whether there is a malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking based on P11. If not, collect the pressure value P12 of the second pressure sensor 13, and compare P11 and P12 to determine whether there is a malfunction of the carbon canister 2 being blocked. If not, proceed to the next step;

[0048] Closing the flushing valve 8 is to cut off the intake manifold 4 to avoid air leakage at the current passage. Closing the first solenoid valve 14 is equivalent to cutting off the fuel tank 1 and the fuel filling pipe 5. The entire fuel evaporation system passage part is the DMTL module 3, the connecting pipe 9, the carbon canister 2, and the connecting pipe 7;

[0049] When the air pump of the DMTL module 3 pressurizes and injects gas into the passage, the pressure value of the connecting pipe 9 can be collected through the first pressure sensor 12. At this time, the pressure value is actually the pressure value of the entire passage. If there is a leakage in this passage, the pressure value P11 monitored by the first pressure sensor 12 will be significantly smaller than the pressure value under normal conditions of the passage. And there are only two possibilities for such a leakage situation. One is that the flushing valve 8 is stuck, and the stuck flushing valve 8 causes the connecting pipe 7 to communicate with the intake manifold 4, and the gas in the passage leaks through the intake manifold 4; the other is that the connecting pipe 7 leaks;

[0050] Of course, in this passage, it is also possible that the connecting pipe 9 leaks, but generally the pipeline of the connecting pipe 9 is very short, and the possibility of leakage is small, so this situation is excluded;

[0051] If the monitored P11 is normal, it proves that there is no malfunction of the above-mentioned flushing valve 8 being stuck or the connecting pipe 7 leaking in the current passage. At this time, the pressure value P12 in the connecting pipe 7 can be monitored through the second pressure sensor 13. The first pressure sensor 12 is at the front end of the carbon canister 2, and the second pressure sensor 13 is at the rear end of the carbon canister 2 (the front end and the rear end here are determined along the direction of the air pump injecting gas). If the pressure value P11 and the pressure value P12 differ greatly, it proves that the carbon canister 2 between the first pressure sensor 12 and the second pressure sensor 13 may be blocked. If the pressure value P11 and the pressure value P12 do not differ greatly, it proves that the carbon canister 2 is normally connected. The carbon canister 2 has a certain fluid resistance, so the pressure value P11 and the pressure value P12 will not be exactly equal;

[0052] S2. Open the first solenoid valve 14, close the flushing valve 8, the second solenoid valve 15 and the third solenoid valve 16. The DMTL module 3 injects gas into the fuel evaporation system, collects the pressure value P21 of the first pressure sensor 12, and determines whether there is a fault of leakage in the vent pipe 6 or the circulation pipe 11 based on P21. If not, proceed to the next step;

[0053] The purpose of opening the first solenoid valve 14 is to add the vent pipe 6 to the passage on the basis of step S1. Therefore, the current passage includes the DMTL module 3, the connecting pipe 9, the carbon canister 2, the connecting tube 7 and the vent pipe 6. In step S2, by collecting the pressure value P21 of the first pressure sensor 12, if the pressure value P21 is significantly lower than the pressure value under normal conditions, it proves that there is a leakage in the current passage. Since it has been proved in step S1 that the flushing valve 8 is not stuck, the connecting tube 7 does not leak, and the carbon canister 2 is not blocked, the possible faults are only the leakage of the vent pipe 6 or the leakage of the circulation pipe 11;

[0054] S3. Close the flushing valve 8, open the first solenoid valve 14, the second solenoid valve 15 and the third solenoid valve 16. The DMTL module 3 injects gas into the fuel evaporation system, collects the pressure value P31 of the first pressure sensor 12, and determines whether there is a fault of leakage in the fuel tank 1 based on P31. If not, it proves that the fuel evaporation system is normal;

[0055] Opening the first solenoid valve 14, the second solenoid valve 15 and the third solenoid valve 16 is equivalent to connecting the entire fuel evaporation system. The current passage includes the DMTL module 3, the connecting pipe 9, the carbon canister 2, the connecting tube 7, the vent pipe 6, the circulation pipe 11, the fuel filling pipe 5 and the fuel tank 1. In step S3, by collecting the pressure value P31 of the first pressure sensor 12, if the pressure value P31 is significantly lower than the pressure value under normal conditions, it proves that there is a leakage in the current passage. Since it has been proved in step S2 that the flushing valve 8 is not stuck, the connecting tube 7 does not leak, the carbon canister 2 is not blocked, the vent pipe 6 does not leak, and the circulation pipe 11 does not leak, the possible fault is only the leakage of the fuel tank 1. In fact, it is also possible that the circulation pipe 11 or the fuel filling pipe 5 leaks, but this situation is rare and is excluded;

[0056] If the diagnosis is carried out according to the above process, specifically as shown in the appendix Figure 3 If there is no fault situation, it proves that there is no fault in the current fuel evaporation system. In the specific steps, if the above fault situation occurs, the entire diagnosis process ends immediately.

[0057] After the corresponding fault situation occurs, immediately analyze and repair according to the specific fault diagnosis situation.

[0058] In a further embodiment of the present application, this embodiment optimizes the above-mentioned step S1. In the above step S1, the method for determining whether there is a malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking based on P11 is as follows: Compare the pressure value P11 of the first pressure sensor 12 with the set pressure value Pref. If P11 < Pref, it is determined that there is a malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking; if P11 ≥ Pref, it is determined that there is no malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking at present.

[0059] The set pressure value Pref is the pressure value under the condition that the current passage is working normally, that is, there is no malfunction in the current passage, and it can also be defined as the normal working pressure value of the air pump in the DMTL module 3 when there is no malfunction in the fuel evaporation system.

[0060] P11 < Pref proves that there must be a leakage in the current passage, and the most likely leakage is that the flushing valve 8 is stuck or the connecting pipe 7 leaks. Through this method, the fault diagnosis situation of the current passage can be quickly obtained.

[0061] P11 ≥ Pref proves that there is no leakage in the current passage.

[0062] In a preferred embodiment of the present application, this embodiment further optimizes the above-mentioned step S1. Specifically, in step S1, when it is proved that there is no malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking in the current passage, the pressure value P12 in the connecting pipe 7 can be collected by the second pressure sensor 13, and P11 is compared with P12. If (P11 - P12) / P11 > a, it is determined that there is a malfunction of the carbon canister 2 being blocked; if (P11 - P12) / P11 ≤ a, it is determined that there is no malfunction of the carbon canister 2 being blocked at present.

[0063] The a in this embodiment is 5%, and it can also be other empirical values as long as the requirements are met.

[0064] The first pressure sensor 12 and the second pressure sensor 13 are respectively placed at the front and rear ends of the carbon canister 2. If the pressure value P11 monitored by the first pressure sensor 12 is very different from P12 of the second pressure sensor 13, it proves that it is very difficult for the air pump to inject air through the carbon canister 2, and at this time the carbon canister 2 is blocked; if the pressure value P11 monitored by the first pressure sensor 12 is not very different from P12 of the second pressure sensor 13, considering that the carbon canister 2 itself has a certain fluid resistance, it can be proved that the carbon canister 2 is normal at this time.

[0065] In another embodiment of the present application, this embodiment further optimizes the above-mentioned step S2. Specifically, in the above-mentioned step S2, the method for determining whether there is a failure of the vent pipe 6 leaking or the circulation pipe 11 leaking based on P21 is as follows: Compare the pressure value P21 of the first pressure sensor 12 with the set pressure value Pref. If P21 < Pref, it is determined that there is a failure of the vent pipe 6 leaking or the circulation pipe 11 leaking; if P21 ≥ Pref, it is determined that there is no failure of the vent pipe 6 leaking or the circulation pipe 11 leaking at present.

[0066] Similarly, the set pressure value Pref is the pressure value under the condition that the current passage is working normally. P21 < Pref proves that there is a leakage failure in the current passage at this time. Step S1 proves that there is no failure of the flushing valve 8 being stuck or the connecting pipe 7 leaking in the current passage. Based on the modules connected in the current passage, it can be quickly determined that the position of the failure in the current passage is the vent pipe 6 or the circulation pipe 11. Only when the vent pipe 6 leaks or the circulation pipe 11 leaks will the above situation occur. P21 ≥ Pref proves that there is no failure of the vent pipe 6 leaking or the circulation pipe 11 leaking in the current passage.

[0067] In a further embodiment of the present application, this embodiment optimizes the above-mentioned step S3. Specifically, in the above-mentioned step S3, the method for determining whether there is a failure of the fuel tank 1 leaking based on P31 is as follows: Compare the pressure value P31 of the first pressure sensor 12 with the set pressure value Pref. If P31 < Pref, it is determined that there is a failure of the fuel tank 1 leaking; if P31 ≥ Pref, it is determined that there is no failure of the fuel tank 1 leaking at present.

[0068] Similarly, the set pressure value Pref is the pressure value under the condition that the current passage is working normally. P31 < Pref proves that there is a leakage situation in the current passage. The above steps S1 and S2 prove that the flushing valve 8 is not stuck, the connecting pipe 7 does not leak, the carbon canister 2 is not blocked, the vent pipe 6 does not leak, and the circulation pipe 11 does not leak. Therefore, the possible failure is only the leakage of the fuel tank 1. P31 ≥ Pref proves that the fuel tank 1 is normal at this time and there is no failure situation.

[0069] In another embodiment of the present application, another judgment method is adopted. In the above step S1, the flushing valve 8 and the first solenoid valve 14 are closed, the second solenoid valve 15 and the third solenoid valve 16 are opened, the DMTL module 3 injects gas into the fuel evaporation system, the operating current I11 of the air pump in the DMTL module 3 is collected, and I11 is compared with the set current value Iref. If I11 < Iref, it is determined that there is a malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking; if I11 ≥ Iref, it is determined that there is no malfunction of the flushing valve 8 being stuck or the connecting pipe 7 leaking at present.

[0070] Iref is the normal operating current of the air pump in the DMTL module 3 when there is no malfunction in the current passage. The change in current can indirectly reflect the change in pressure in the passage. Therefore, by monitoring the current situation, it can be determined whether there is a leakage malfunction in the current passage.

[0071] Similarly, in the above step S2, the first solenoid valve 14 is opened, the flushing valve 8, the second solenoid valve 15 and the third solenoid valve 16 are closed, the DMTL module 3 injects gas into the fuel evaporation system, the operating current I21 of the air pump in the DMTL module 3 is collected, and I21 is compared with the set current value Iref. If I21 < Iref, it is determined that there is a malfunction of the vent pipe 6 leaking or the circulation pipe 11 leaking; if I21 ≥ Iref, it is determined that there is no malfunction of the vent pipe 6 leaking or the circulation pipe 11 leaking at present.

[0072] The same is true in step S3. In step S3, the flushing valve 8 is closed, the first solenoid valve 14, the second solenoid valve 15 and the third solenoid valve 16 are opened, the DMTL module 3 injects gas into the fuel evaporation system, the operating current I31 of the air pump in the DMTL module 3 is collected, and I31 is compared with the set current value Iref. If I31 < Iref, it is determined that there is a malfunction of the fuel tank 1 leaking; if I31 ≥ Iref, it is determined that there is no malfunction of the fuel tank 1 leaking at present.

[0073] By collecting the current situation of the air pump in the DMTL module 3, the change in air pressure in the passage can be indirectly obtained. Therefore, the first pressure sensor 12 in the fuel evaporation system can be removed, and diagnosis and judgment can be carried out based on the change in current. Or the first pressure sensor 12 can not be removed, and the diagnosis method based on current, that is, the combination of pressure measurement and current measurement, is used. The two verify each other to improve the accuracy of the entire fault diagnosis.

[0074] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, various changes and improvements will occur to the present invention, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for diagnosing faults in a fuel evaporation system, the fuel evaporation system including a fuel tank, a carbon canister, a DMTL module, and an intake manifold; a fuel filling pipe is installed on the fuel tank, and the fuel tank is communicated with the adsorption port of the carbon canister through a ventilation pipe; the desorption port of the carbon canister is communicated with the intake manifold through a connecting pipe; a flushing valve is arranged at the connection between the intake manifold and the connecting pipe; the diagnostic port of the carbon canister is communicated with the DMTL module through a communicating pipe; the ventilation pipe is communicated with the fuel filling pipe through a circulation pipe, It is characterized in that: further including a first pressure sensor installed on the communicating pipe, a second pressure sensor installed on the connecting pipe, a first solenoid valve installed on the ventilation pipe between the circulation pipe and the carbon canister, a second solenoid valve installed on the ventilation pipe between the circulation pipe and the fuel tank, and a third solenoid valve installed on the circulation pipe; The diagnostic method is carried out according to the following steps: S1. Close the flushing valve and the first solenoid valve, open the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the pressure value P11 of the first pressure sensor, and judge whether there is a fault of flushing valve jamming or connecting pipe leakage based on P11. If not, collect the pressure value P12 of the second pressure sensor, compare P11 and P12 to judge whether there is a fault of carbon canister blockage. If not, proceed to the next step; S2. Open the first solenoid valve, close the flushing valve, the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the pressure value P21 of the first pressure sensor, and judge whether there is a fault of ventilation pipe leakage or circulation pipe leakage based on P21. If not, proceed to the next step; S3. Close the flushing valve, open the first solenoid valve, the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the pressure value P31 of the first pressure sensor, and judge whether there is a fault of fuel tank leakage based on P31. If not, it proves that the fuel evaporation system is normal; In the step S1, the method for judging whether there is a fault of flushing valve jamming or connecting pipe leakage based on P11 includes: comparing the pressure value P11 of the first pressure sensor with a set pressure value Pref. If P11 < Pref, it is judged that there is a fault of flushing valve jamming or connecting pipe leakage; if P11 ≥ Pref, it is judged that there is no current fault of flushing valve jamming or connecting pipe leakage.

2. The method for diagnosing a failure of a fuel evaporation system according to claim 1, wherein: In the step S1, comparing P11 and P12 to judge whether there is a fault of carbon canister blockage: compare P11 with P12. If (P11 - P12) / P11 > a, it is judged that there is a current fault of carbon canister blockage; if (P11 - P12) / P11 ≤ a, it is judged that there is no current fault of carbon canister blockage.

3. The method for diagnosing a fuel evaporation system failure according to claim 1, wherein: In the step S2, the method for judging whether there is a fault of ventilation pipe leakage or circulation pipe leakage based on P21 includes: comparing the pressure value P21 of the first pressure sensor with a set pressure value Pref. If P21 < Pref, it is judged that there is a fault of ventilation pipe leakage or circulation pipe leakage; if P21 ≥ Pref, it is judged that there is no current fault of ventilation pipe leakage or circulation pipe leakage.

4. The method for diagnosing a failure of a fuel evaporation system according to claim 1, wherein: In step S3, the method for judging whether there is a fuel tank leakage fault based on P31 includes: comparing the pressure value P31 of the first pressure sensor with the set pressure value Pref. If P31 < Pref, it is judged that there is a fuel tank leakage fault; if P31 ≥ Pref, it is judged that there is no fuel tank leakage fault at present.

5. The method for diagnosing a fuel evaporation system failure according to claim 1, characterized in that: In step S1, close the flushing valve and the first solenoid valve, open the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the working current I11 of the air pump in the DMTL module, compare I11 with the set current value Iref. If I11 < Iref, it is judged that there is a fault of the flushing valve sticking or the connecting pipe leaking; if I11 ≥ Iref, it is judged that there is no fault of the flushing valve sticking or the connecting pipe leaking at present.

6. The method for diagnosing a fuel evaporation system failure according to claim 1, wherein: In step S2, open the first solenoid valve, close the flushing valve, the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the working current I21 of the air pump in the DMTL module, compare I21 with the set current value Iref. If I21 < Iref, it is judged that there is a fault of the vent pipe leaking or the circulation pipe leaking; if I21 ≥ Iref, it is judged that there is no fault of the vent pipe leaking or the circulation pipe leaking at present.

7. The method for diagnosing a failure of a fuel evaporation system according to claim 1, characterized in that: In step S3, close the flushing valve, open the first solenoid valve, the second solenoid valve and the third solenoid valve, the DMTL module injects gas into the fuel evaporation system, collect the working current I31 of the air pump in the DMTL module, compare I31 with the set current value Iref. If I31 < Iref, it is judged that there is a fuel tank leakage fault; if I31 ≥ Iref, it is judged that there is no fuel tank leakage fault at present.

8. A method for diagnosing a failure of a fuel evaporation system according to any one of claims 1 to 4, characterized in that: The set pressure value Pref is the normal working pressure of the air pump in the DMTL module when there is no fault in the fuel evaporation system.

9. A method for diagnosing a failure of a fuel evaporation system according to any one of claims 5 to 7, characterized in that: The set current value Iref is the normal working current of the air pump in the DMTL module when there is no fault in the fuel evaporation system.

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