Fault diagnosis method and apparatus for front oxygen sensor, and vehicle

Abstract

A fault diagnosis method and apparatus for a front oxygen sensor, and a vehicle. The fault diagnosis method comprises: when the change in fuel trim values before and after a rear oxygen sensor is updated is less than a preset threshold, and an emission air-fuel ratio control function is activated, entering a diagnosis process; acquiring an integral value of a measured air-fuel ratio within a diagnosis period; acquiring an integral value of a target air-fuel ratio within the diagnosis period; calculating a target integral ratio, wherein the target integral ratio is a ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio; and if the target integral ratio is less than a fault integral ratio, determining that the front oxygen sensor is faulty.

Description

Fault diagnosis methods, devices and vehicles for front oxygen sensors

[0001] This application claims priority to Chinese Patent Application No. 202411193968.0, filed on August 28, 2024, entitled "Method, Apparatus and Vehicle for Fault Diagnosis of Front Oxygen Sensor", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to, but is not limited to, the field of vehicle technology, and in particular to a method, apparatus, and vehicle for diagnosing a fault in a front oxygen sensor. Background Technology

[0003] Currently, vehicle exhaust treatment systems treat pollutants in exhaust gases through oxidation-reduction reactions. Different engine raw emission compositions and catalytic converter formulations have an optimal conversion window. The engine controller maintains this optimal conversion window by periodically changing the target air-fuel ratio and adjusting the fuel injection quantity and air-fuel ratio.

[0004] However, if the pre-oxygen sensor ages, meaning it cannot provide real-time feedback on dynamic changes in the air-fuel ratio (e.g., there is a delay), it will affect air-fuel ratio control and exhaust gas treatment. Therefore, detecting whether the pre-oxygen sensor is faulty becomes a problem that needs to be solved. Currently, there are two main methods to detect whether the pre-oxygen sensor is abnormal: The first method is to actively change the target air-fuel ratio and determine whether the change in the air-fuel ratio measured by the pre-oxygen sensor is consistent with the expectation; the second method is not to actively change the target air-fuel ratio (but to control the air-fuel ratio through emissions), and when the target air-fuel ratio changes periodically, to obtain the measured change in air-fuel ratio and compare it with various pre-stored air-fuel ratio change models to assess whether the pre-oxygen sensor is abnormal.

[0005] In the first method, which actively changes the target air-fuel ratio, the fluctuations in the target air-fuel ratio are relatively large, leading to a significant increase in pollutant emissions and a deterioration in emission results. In the second method, which does not actively change the target air-fuel ratio, it is only applicable to scenarios where the pre-oxygen sensor experiences a symmetrical fault (failure for both rich-to-lean and lean-to-rich target air-fuel ratio changes). It cannot diagnose asymmetrical faults from rich-to-lean or lean-to-rich to rich states individually, making it prone to misdiagnosis and missed diagnosis. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] This application provides a method, apparatus, and vehicle for diagnosing faults in a front oxygen sensor, in order to improve the accuracy of fault diagnosis of the front oxygen sensor.

[0008] In a first aspect, this application provides a method for diagnosing faults in a pre-oxygen sensor, the method comprising:

[0009] Determine whether the vehicle currently meets the diagnostic conditions, which include: the change in fuel correction value before and after the rear oxygen sensor update is less than a preset threshold, and the emission air-fuel ratio control function is activated;

[0010] If the diagnostic conditions are met, the integral value of the measured air-fuel ratio is obtained. The starting point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the ending point is the time point determined according to the duration of the target air-fuel ratio change.

[0011] Obtain a target integral ratio, which is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio, and the integral range of the integral value of the target air-fuel ratio is the same as the integral range of the integral value of the measured air-fuel ratio.

[0012] The pre-oxygen sensor is determined to be faulty based on the target integral ratio.

[0013] Optionally, the method further includes:

[0014] Real-time acquisition of the duration for which the target air-fuel ratio begins to change;

[0015] If the duration is longer than the first duration, the end time of the first duration shall be taken as the integral endpoint of the measured air-fuel ratio.

[0016] If the duration is greater than the preset second duration but less than the first duration, then the time point at which the transition ends is taken as the integral endpoint of the measured air-fuel ratio.

[0017] The first duration is determined based on engine speed and load, and the second duration is shorter than the first duration.

[0018] Optionally, determining whether the pre-oxygen sensor has malfunctioned based on the target integral ratio includes:

[0019] Determine whether the target integral ratio is greater than the preset fault integral ratio;

[0020] If the target integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty;

[0021] If the target integral ratio is less than or equal to the fault integral ratio, then the front oxygen sensor is determined to be faulty.

[0022] Optionally, the fault integral ratio is the minimum of the following values: the fault integral ratio determined based on the integral time, the fault integral ratio determined based on the oxygen storage, and the fault integral ratio determined based on the post-oxygen fuel correction value.

[0023] Optionally, the method further includes:

[0024] If a fault is found in the front oxygen sensor, the slope of the measured air-fuel ratio from the start point to the end point within a preset unit time interval is obtained during the duration of the target air-fuel ratio starting to change.

[0025] Based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval, the fault type of the pre-oxygen sensor is determined, including delay fault or slope fault.

[0026] Optionally, determining the fault type of the pre-oxygen sensor based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval includes:

[0027] Obtain the number of slopes with a slope greater than the fault slope value during the duration of the target air-fuel ratio starting to change.

[0028] Determine whether the number of slopes is greater than a preset number;

[0029] If the slope count is greater than the preset count, then the front oxygen sensor is determined to have a slope fault.

[0030] If the slope number is less than or equal to the preset number, then the pre-oxygen sensor is determined to have a delay fault.

[0031] Optionally, determining whether the pre-oxygen sensor has malfunctioned based on the target integral ratio includes:

[0032] Obtain the target integral ratio for multiple diagnostic cycles, wherein a diagnostic cycle is defined as the period from the start to the end of a target air-fuel ratio jump.

[0033] Remove the minimum and maximum values ​​from the target integration ratios of the multiple diagnostic cycles, and calculate the average integration ratio of the remaining target integration ratios;

[0034] Determine whether the average integral ratio is greater than the preset fault integral ratio;

[0035] If the average integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty.

[0036] If the average integral ratio is less than or equal to the preset fault integral ratio, then the front oxygen sensor is determined to be faulty.

[0037] Optionally, the diagnostic conditions may further include at least one of the following:

[0038] Atmospheric pressure is within the preset range, coolant temperature is within the preset range, the vehicle is in a non-interruptible fuel supply state, the vehicle is in a non-carbon canister flushing state and the duration meets the threshold, engine speed fluctuation is less than the threshold, engine load fluctuation is less than the threshold, and the cumulative intake air volume of the current driving cycle is greater than the threshold.

[0039] Secondly, this application also provides a fault diagnosis device for a pre-oxygen sensor, the device comprising:

[0040] The judgment module is used to determine whether the vehicle currently meets the diagnostic conditions, which include: the change in the fuel correction value before and after the rear oxygen sensor update is less than a preset threshold, and the emission air-fuel ratio control function is activated.

[0041] The first acquisition module is used to acquire the integral value of the measured air-fuel ratio if the diagnostic conditions are met. The integration start point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the integration end point is the time point determined according to the duration of the target air-fuel ratio change.

[0042] The second acquisition module is used to acquire a target integral ratio, which is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio, and the integral range of the integral value of the target air-fuel ratio is the same as the integral range of the integral value of the measured air-fuel ratio.

[0043] The fault determination module is used to determine whether the pre-oxygen sensor has malfunctioned based on the target integral ratio.

[0044] Thirdly, this application provides a vehicle, including: a front oxygen sensor, a rear oxygen sensor, and a controller;

[0045] The controller is used to perform the method as described in any of the first aspects.

[0046] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any of the first aspects.

[0047] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the method described in any of the first aspects.

[0048] This application provides a method, apparatus, and vehicle for diagnosing a fault in a front oxygen sensor. The method includes: entering a diagnostic process when the absolute value of the difference between the updated fuel correction value and the original fuel correction value of the rear oxygen sensor is greater than 0 and less than a preset threshold, and the emission air-fuel ratio control function is activated; acquiring the integral value of the measured air-fuel ratio within the diagnostic cycle; acquiring the integral value of the target air-fuel ratio within the diagnostic cycle; calculating the target integral ratio between the integral value of the measured air-fuel ratio and the integral value of the target air-fuel ratio; and determining that the front oxygen sensor has malfunctioned if the target integral ratio is less than the fault integral ratio. This method can diagnose every change in air-fuel ratio, is applicable to both asymmetric and symmetric faults, improves diagnostic accuracy, and completes the diagnosis within the diagnostic cycle during the continuous transition process, with controllable time consumption. Furthermore, compared to the active method, this method has less impact on emissions, and diagnosis can be performed as long as the diagnostic conditions are met.

[0049] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application. Other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. Attached Figure Description

[0050] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0051] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0052] Figure 1 is a schematic diagram of the air-fuel ratio change provided in this application;

[0053] Figure 2 is a flowchart illustrating the fault diagnosis method for the pre-oxygen sensor provided in this application.

[0054] Figure 3 is a schematic flowchart of the fault diagnosis method for the pre-oxygen sensor provided in this application.

[0055] Figure 4 is a flowchart illustrating the fault diagnosis method for the pre-oxygen sensor provided in this application.

[0056] Figure 5 is a schematic diagram of the change in the target air-fuel ratio and the change in the measured air-fuel ratio provided in this application.

[0057] Figure 6 is a schematic diagram of the change in the target air-fuel ratio and the change in the measured air-fuel ratio provided in this application.

[0058] Figure 7 is a schematic diagram of the fault diagnosis device for the pre-oxygen sensor provided in this application;

[0059] Figure 8 is a schematic diagram of the controller provided in this application.

[0060] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0061] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0062] It should be noted that the user information (including but not limited to user device information, user vehicle information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with relevant laws, regulations and standards, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0063] First, let me explain the terms used in this application:

[0064] Air-fuel ratio: refers to the mass ratio of air to fuel in the air-fuel mixture in a vehicle engine. It is an important parameter for engine combustion efficiency and emission control.

[0065] Theoretically, the complete combustion of 1 kg of gasoline requires approximately 14.7 kg of air; therefore, an air-fuel ratio of 14.7 is considered ideal or theoretical. In practical applications, engines are equipped with oxygen sensors and implement closed-loop control to maintain the air-fuel ratio within a near-ideal range, thereby optimizing combustion efficiency and reducing emissions.

[0066] If the air-fuel ratio is less than the ideal range, it means the mixture is too rich, which may lead to incomplete combustion and carbon buildup. If the air-fuel ratio is greater than the ideal range, it means the mixture is too lean. Although combustion is more complete, it may reduce engine power.

[0067] Front oxygen sensor: Usually installed at the front of the exhaust manifold or exhaust pipe, close to the engine. Its main function is to monitor the oxygen content in the exhaust and feed the data back to the engine control unit. The change in air-fuel ratio can be determined based on the oxygen content in the exhaust.

[0068] Post-oxygen sensor: Typically installed after the catalytic converter, its main function is to monitor the oxygen content in the exhaust gas after it has been processed by the catalytic converter. By comparing the data from the front and rear oxygen sensors, the ECU can determine the efficiency of the catalytic converter and make necessary adjustments to ensure emissions meet standards.

[0069] Currently, vehicle exhaust aftertreatment systems (three-way catalytic converters) treat pollutants in exhaust gases through oxidation-reduction reactions. From an emissions purification perspective, different engine original emission compositions and catalytic converter formulations each have an optimal conversion window (Lambda conversion window). The Lambda target value refers to the ratio of different air-fuel ratios to the optimal air-fuel ratio. The engine controller periodically changes the target air-fuel ratio (from rich to lean, lean to rich), detects changes in the actual air-fuel ratio, and adjusts the fuel injection quantity or intake air quantity in a closed loop based on changes in the actual air-fuel wave to maintain the air-fuel ratio within the optimal conversion window.

[0070] Figure 1 is a schematic diagram of the air-fuel ratio change provided in this application. In Figure 1, Figure a shows the change of the target air-fuel ratio, and the increase of the air-fuel ratio is the process of controlling the engine fuel to become lean. Figure b is a schematic diagram of the normal change of the measured air-fuel ratio. The measured air-fuel ratio change detected by the sensor is basically the same as the theoretically controlled target air-fuel ratio change.

[0071] If the current oxygen sensor malfunctions, meaning the front oxygen sensor cannot provide real-time feedback on dynamic changes in the air-fuel ratio, then graphs c and d will appear. Graph c shows a delayed measured air-fuel ratio, indicating a delay-related fault in the front oxygen sensor; graph d shows a slow change in the measured air-fuel ratio, indicating a slope-related fault in the front oxygen sensor. Therefore, a malfunction in the front oxygen sensor will affect the control of the air-fuel ratio.

[0072] Figure 1 above only shows one leaning scenario; the enrichment scenario is the same, except that both the target air-fuel ratio and the measured air-fuel ratio decrease. When fuel enrichment and leaning occur in pairs in a single test, it is called a symmetrical change. If only one enrichment or leaning occurs, it is called an asymmetrical change.

[0073] Currently, there are two main methods for detecting faults in the pre-oxygen sensor:

[0074] The first approach is the active method, which involves actively changing the air-fuel ratio by a significant amount, specifically a change in the lambda target value greater than 0.05, thus unidirectionally altering the target air-fuel ratio. Anomalies are determined by comparing the actual air-fuel ratio change measured by the pre-oxygen sensor with the expected change. Here, the change in the lambda target value refers to using the air-fuel ratio corresponding to the changed lambda target value as the target air-fuel ratio.

[0075] The second approach is a passive method. This method does not actively change the target air-fuel ratio (it controls the air-fuel ratio through normal emissions). During the periodic and continuous fluctuations of the target air-fuel ratio, the system acquires the measured changes in the air-fuel ratio. The system caches a set of air-fuel ratio model values ​​with different delay / filtering times in the diagnostic module. Then, it compares the measured air-fuel ratio changes with each delay / filtering value in the model array to determine the value that best fits the air-fuel ratio model. Based on the acquired air-fuel ratio model value, it determines whether a fault has occurred. The comparison calculation process also calculates the maximum covariance value, which is used as the basis for subsequently determining the air-fuel ratio model value.

[0076] However, both of the above methods have drawbacks:

[0077] The first approach, the drawbacks of the active method:

[0078] a) Actively altering the air-fuel ratio typically results in a change in the lambda target value greater than 0.1 during symmetrical air-fuel ratio diagnosis and greater than 0.05 during asymmetrical diagnosis. The maximum change in the lambda target value for normal emission air-fuel ratio control is 0.04. Therefore, during diagnosis, the active method deviates from normal emission air-fuel ratio control, leading to a significant increase in pollutants and worse emission results. This is particularly evident in catalytic converters aged at 200,000 km (after a significant decrease in oxygen storage), where emission deterioration is very pronounced.

[0079] b) Due to the large variation in air-fuel ratio and the resulting fluctuation in engine power, a higher vehicle speed (70 km / h) is usually selected, resulting in a lower actual monitoring frequency for vehicle emissions in this diagnostic process.

[0080] c) Active changes will affect the robustness of air-fuel ratio control.

[0081] The second approach, the drawbacks of the non-active method:

[0082] a) The system caches a set of air-fuel ratio model values ​​with different delays / filtering times in the diagnostic module. This is applicable to symmetrical faults (i.e., after the oxygen sensor fails, the air-fuel ratio changes for both enrichment and leaning processes are abnormal). However, the actual signals of asymmetrical faults (i.e. after the oxygen sensor fails, the air-fuel ratio changes for only one enrichment or leaning process are abnormal) are significantly different from those of symmetrical faults, which can easily lead to misjudgment or missed judgment. Therefore, it is not possible to diagnose asymmetrical faults from rich to lean or from lean to rich separately, which can easily lead to misjudgment or missed judgment.

[0083] b) Due to emissions-based air-fuel ratio control, the diagnostic completion time is highly dependent on the oxygen storage in the catalyst. Fresh catalysts have a large oxygen storage, which makes diagnostic completion time relatively long.

[0084] c) The non-active method may result in the current measured air-fuel ratio being the air-fuel ratio from a previous time delay, affecting the accuracy of the judgment.

[0085] This application proposes a fault diagnosis method for a pre-oxygen sensor. This method is based on an active approach, that is, it determines whether the pre-oxygen sensor is faulty by controlling the change in air-fuel ratio based on normal exhaust gas detection. Specifically, when the detection conditions are met, the integral value of the measured air-fuel ratio within a diagnostic cycle is obtained. If the duration of the air-fuel ratio change is greater than a first duration, the end time of the first duration is taken as the end of the diagnostic cycle; otherwise, the end time of the air-fuel ratio change is taken as the end of the diagnostic cycle. By comparing the integral value of the measured air-fuel ratio within the diagnostic cycle with the integral value of the target air-fuel ratio, it is possible to determine whether the pre-oxygen sensor is faulty. Diagnosis can be performed every time the air-fuel ratio changes, which is applicable to both asymmetric and symmetric faults, and the diagnosis completion time is controllable.

[0086] The subject of this application is the Electronic Control Module (ECU) of an automotive engine, or a chip or processor inside the ECU.

[0087] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0088] Figure 2 is a flowchart illustrating the fault diagnosis method for the pre-oxygen sensor provided in this application. As shown in Figure 2, the method includes:

[0089] S101. Determine whether the vehicle currently meets the diagnostic conditions. The diagnostic conditions include: the change in the fuel correction value before and after the rear oxygen sensor update is less than the preset threshold, and the emission air-fuel ratio control function is activated.

[0090] In this step, the vehicle controller ECU obtains the activation status of the emission air-fuel ratio control function. When the emission air-fuel ratio control function is activated, the target air-fuel ratio is changed periodically. After the target air-fuel ratio is changed, the rear oxygen sensor controls the cessation of changing the target air-fuel ratio based on the detected oxygen content in the exhaust gas.

[0091] The principle behind this solution is to perform fault diagnosis on the preceding oxygen sensor under the condition that the emission air-fuel ratio control function is activated. Therefore, for the preceding oxygen sensor to be fault-diagnosed, the emission air-fuel ratio control function must be activated.

[0092] In addition, the diagnostic conditions also need to meet the following requirements: after the oxygen sensor performs self-learning, the fuel correction value is updated (i.e., the self-learning value), and the absolute value of the difference between the updated fuel correction value and the previous fuel correction value is greater than 0 and less than a preset threshold.

[0093] The self-learning process of the rear oxygen sensor refers to the automatic adjustment and learning of the fuel system based on the feedback signal from the rear oxygen sensor. The adjusted fuel injection quantity is the fuel trim value. Fuel trim values ​​are also divided into short-term and long-term fuel trim values.

[0094] Therefore, a change in the fuel trim value indicates an abnormality in the air-fuel ratio control or exhaust gas treatment process, and only in this case will the pre-oxygen sensor fault detection begin. The absolute value of the difference between the updated and unupdated fuel trim values ​​must be less than a preset threshold. This is because a difference greater than the preset threshold indicates a systemic fault or a physical hardware malfunction, not a fault in the pre-oxygen sensor.

[0095] The preset threshold is determined by the developers through pre-calibration.

[0096] S102. If the diagnostic conditions are met, obtain the integral value of the measured air-fuel ratio. The starting point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the ending point is the time point determined according to the duration of the target air-fuel ratio change.

[0097] In this step, once the diagnostic conditions are met, fault diagnosis can be performed. First, it's necessary to determine the current diagnostic cycle and obtain the integral value of the measured air-fuel ratio within that cycle. As shown in Figure 1, the starting point of the diagnostic cycle is the time when the target air-fuel ratio begins to change, i.e., the starting point of the measured air-fuel ratio integral. The change in the measured air-fuel ratio can have several scenarios. If it's as shown in Figure 1c, the measured air-fuel ratio hasn't changed at the start of the diagnostic cycle; if it's as shown in Figure 1b or d, the measured air-fuel ratio changes at the start of the diagnostic cycle. The change is triggered based on preset conditions, and the height of the change is related to the lambda target value, which needs to be less than 0.04.

[0098] The endpoint of the diagnostic cycle is determined by the duration following the target air-fuel ratio jump, which in turn is determined by the oxygen content in the exhaust gas detected by the post-oxygen sensor. Therefore, the duration following the target air-fuel ratio jump is not a fixed value. The endpoint of the diagnostic cycle differs depending on the duration following the jump.

[0099] In one specific implementation, if the duration after the target air-fuel ratio jump is greater than a first duration, then the end time of the first duration is taken as the end point of the diagnostic cycle, i.e., the integration end point of the measured air-fuel ratio. The first duration is determined by consulting a preset table based on engine speed and load; the preset table contains values ​​of the first duration calibrated by the developers for different operating conditions. If the duration is greater than a preset second duration but less than the first duration, then the end time of the jump is taken as the integration end point of the measured air-fuel ratio, where the second duration is less than the first duration.

[0100] For example, the first duration is 15 seconds as obtained from the table, and the second duration is a preset 5 seconds. If the duration after the target air-fuel ratio jump is 20 seconds, then the 15-second time point is taken as the end point of the diagnostic cycle (i.e., the end point of integration); if the duration after the target air-fuel ratio jump is 6 seconds, then the last time point of the duration after the target air-fuel ratio jump (i.e., the time point when the jump ends, which is the time point at 6 seconds) is taken as the end point of the diagnostic cycle.

[0101] S103. Obtain the target integral ratio. The target integral ratio is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio. The integral range of the target air-fuel ratio is the same as the integral range of the measured air-fuel ratio.

[0102] In this step, after obtaining the integral value of the measured air-fuel ratio, the integral value of the target air-fuel ratio is obtained within the same integral period. The integral value of the measured air-fuel ratio is divided by the integral value of the target air-fuel ratio to obtain the ratio of the two integral values, which is taken as the target integral ratio.

[0103] For a fault-free pre-oxygen sensor, the sensitivity response is timely, and the reaction speed of the measured air-fuel ratio will be very close to the expected value, so the target integral ratio will be close to 1. If the pre-oxygen sensor is aged and the speed of obtaining the measured air-fuel ratio is not timely, such as in Figure 1c or d, the integral value of the measured air-fuel ratio will decrease. A smaller integral value of the measured air-fuel ratio will result in a target integral ratio less than 1; the more severe the fault, the smaller the target integral ratio.

[0104] S104. Determine whether the front oxygen sensor is faulty based on the target integral ratio.

[0105] If the target integral value is less than the preset fault integral ratio, the front oxygen sensor is determined to be faulty; otherwise, the front oxygen sensor is determined not to be faulty.

[0106] The exemplary fault integral ratio can be set to 0.5, 0.6, or 0.4. The specific value used can be adjusted according to the actual calibration process, and there is no restriction here.

[0107] Optionally, the fault integral ratio can also be dynamically determined from a preset fault integral ratio based on the diagnostic process. How to determine it will be described in subsequent embodiments.

[0108] The fault diagnosis method for the front oxygen sensor provided in this application begins when the absolute value of the difference between the updated fuel correction value and the original fuel correction value of the rear oxygen sensor is greater than 0 and less than a preset threshold, and the emission air-fuel ratio control function is activated. The method acquires the integral value of the measured air-fuel ratio within the diagnosis cycle; acquires the integral value of the target air-fuel ratio within the diagnosis cycle; calculates the target integral ratio between the integral value of the measured air-fuel ratio and the integral value of the target air-fuel ratio; and determines that the front oxygen sensor has malfunctioned if the target integral ratio is less than the fault integral ratio. This method can diagnose every change in air-fuel ratio, is applicable to both asymmetric and symmetric faults, improves diagnostic accuracy, and completes the diagnosis within the cycle with controllable time consumption. Furthermore, compared to the active method, this method has less impact on emissions, and diagnosis can be performed as long as the diagnostic conditions are met.

[0109] The non-active method only considers the comparison between the shapes of the signals. The start and end points of the integration in this method are determined based on the current loop, which can avoid the situation where the currently detected measured air-fuel ratio may be the air-fuel ratio of the previous delay, thus improving the accuracy of fault diagnosis.

[0110] After determining that the front oxygen sensor has malfunctioned, the type of malfunction can be further determined. An example is described below.

[0111] Figure 3 is a schematic flowchart of the fault diagnosis method for the pre-oxygen sensor provided in this application, as shown in Figure 3, which includes the following steps:

[0112] S201. If it is determined that the front oxygen sensor is faulty, then obtain the slope of the measured air-fuel ratio from the start point to the end point within a preset unit time interval during the duration of the target air-fuel ratio starting to change.

[0113] Currently, oxygen sensor fault types are mainly divided into delay faults and slope faults. A delay fault refers to a delay in the detection of the front oxygen sensor, causing the measured air-fuel ratio to change more slowly than the normal air-fuel ratio change, as shown in Figure 1c. A slope fault refers to a slow change in the measured air-fuel ratio during the jump process, as shown in Figure 1d.

[0114] Therefore, to distinguish between the two types of faults, the slope of the measured air-fuel ratio is used for differentiation. If the jump process is detected to continue for a period of time with a certain slope within the diagnostic cycle, it is determined to be a slope fault; otherwise, it is considered a delay fault.

[0115] Specifically, during the diagnostic cycle, the slope of the measured air-fuel ratio from the start to the end point is calculated within a preset unit time interval during the duration from which the target air-fuel ratio begins to change. The unit time interval can be set to 50 milliseconds, 100 milliseconds, 500 milliseconds, 1 second, etc., with no specific limitation. The duration of the emission-based air-fuel ratio is on the order of seconds, for example, 15 seconds, 5 seconds, or 30 seconds. Therefore, after the diagnostic cycle is determined, the slope of the measured air-fuel ratio is calculated within each unit time interval.

[0116] For ease of understanding, the following example uses a time interval of 1 second.

[0117] For example, if the first duration is set to 15 seconds, and the duration after the target air-fuel ratio begins to change is 30 seconds, then the diagnostic cycle is 15 seconds. Starting from the beginning of the diagnostic cycle, the slope of the measured air-fuel ratio is obtained for each 1-second interval. After the measured air-fuel ratio reaches its maximum value, the change in the measured air-fuel ratio is very small, and the slope is basically 0. The slopes with a slope less than the preset value can be uniformly set to 0. In this way, 15 slopes are obtained.

[0118] In another example, the first duration is set to 15 seconds, the second duration is set to 4 seconds, and the duration after the target air-fuel ratio starts to change is 5 seconds before the change ends. Therefore, the diagnostic cycle is 5 seconds. The slope of the measured air-fuel ratio is obtained for each 1 second, and a total of 5 slopes are obtained.

[0119] S202. Based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval, determine the fault type of the front oxygen sensor. The fault types include delay fault or slope fault.

[0120] In one specific implementation, a fault slope value is preset. If a certain slope is greater than the fault slope value, it indicates that the measured air-fuel ratio has changed significantly within a unit time interval, resulting in a jump. Under normal circumstances, the jump will be completed within a few unit time intervals, such as one, two, or three unit time intervals. The specific number of unit time intervals in which the jump is completed depends on the length of the set unit time interval.

[0121] Therefore, the number of slopes greater than the fault slope value within the diagnostic cycle is obtained. If the number of slopes is greater than a preset number, it indicates that the transition process is slow, confirming a slope fault in the front oxygen sensor. If the number of slopes is less than or equal to the preset number, it indicates that the transition process is completed within a preset time, confirming a delay fault in the front oxygen sensor.

[0122] Optionally, the measured air-fuel ratio change may be affected by curve fluctuations or other detection factors, and the slope exceeding the fault slope value may be discontinuous, for example, 2, 3, 0, 0, 4, 4, 4. In this case, the slopes before 0 (2, 3) are all defaulted to 0. This method avoids measuring fluctuations as the slope of the measured air-fuel ratio change.

[0123] This embodiment provides a method for diagnosing faults in a pre-oxygen sensor. After determining that a fault has occurred in the pre-oxygen sensor, the method further determines whether a delay fault or a slope fault has occurred by judging the slope change during the diagnostic period.

[0124] There are multiple ways to determine the fault type of the front oxygen sensor by measuring the slope of the air-fuel ratio. The above embodiment only shows one method. The following describes several other possible ways to determine the fault type.

[0125] The following methods are all based on the premise that the oxygen sensor has failed, which is already determined by the integral area.

[0126] The first method:

[0127] The system acquires the number of slopes within a unit time interval that exceed the fault slope value during the diagnostic cycle. If the number of slopes exceeds a preset number, and the slope exceeds the fault slope value in the first unit time interval at the beginning of the diagnostic cycle, it is identified as a slope fault; otherwise, it is identified as a delay fault. In this way, cases where both slope faults and delay faults occur simultaneously are classified as delay faults.

[0128] The second method:

[0129] The process involves obtaining the maximum measured air-fuel ratio within the diagnostic cycle, and then obtaining the measured air-fuel ratio values ​​within a preset range that differ from the maximum value. The earliest value at any given time point within this preset range is then selected as the target value. The value at the point where the measured air-fuel ratio begins to change is obtained. The slope between this starting point and the target value is calculated. The difference between this slope and the fault slope value is then determined. If the slope is greater than the fault slope value, the fault is identified as a delay fault; otherwise, it is identified as a slope fault. Essentially, this method obtains the start and end points of the measured air-fuel ratio change process, calculates the slope of the change, and if the slope is greater than the fault slope, the change process is completed quickly and is not a slope fault but a delay fault; otherwise, it is a slope fault.

[0130] The third method:

[0131] Within the diagnostic cycle, the non-zero slope is obtained for each unit time interval. The average of these non-zero slopes is calculated and compared with the fault slope value. If the average slope is greater than the fault slope, it indicates a delay fault; otherwise, it indicates a slope fault. In this method, if the slope per unit time interval is less than a preset slope, its slope is set to 0. The preset slope is used to avoid slope errors caused by detection when the measured air-fuel ratio has not changed; the preset slope must be less than the fault slope.

[0132] The following section explains how to dynamically obtain the fault integral ratio.

[0133] The fault integral ratio is the minimum of the following values: the fault integral ratio determined based on integral time, the fault integral ratio determined based on oxygen storage, and the fault integral ratio determined based on post-oxygen fuel correction value.

[0134] The fault integral ratio determined based on the integral time is based on the diagnostic cycle time (i.e., the integral time). Developers pre-calibrated the fault integral ratios corresponding to different integral times. For example, when the transition duration is greater than the first duration, and the diagnostic cycle time (integration time) is the first duration, the corresponding fault integral ratio, as found in the table, is 0.9. When the transition duration is greater than the second duration but less than the first duration, the integral time is determined by the time the transition ends. Different transition times correspond to different fault integral ratios. For instance, if the first duration is 15 seconds and the second duration is 5 seconds, the table shows a fault integral ratio of 0.9 for 15 seconds, 0.7 for 10 seconds, and 0.6 for 5 seconds. This is because if the duration is shorter than the first duration, the measured air-fuel ratio may not have reached its maximum value when the transition ends.

[0135] The fault integral ratio, determined based on the post-oxygen fuel correction value, is calculated because the post-oxygen sensor corrects the injected fuel based on the detected exhaust gas. This correction causes a change in the measured air-fuel ratio. Therefore, this factor needs to be excluded when determining if the pre-oxygen sensor is malfunctioning. Consequently, the corresponding fault integral ratio also needs to be updated when the fuel correction value is updated; that is, different fuel correction values ​​correspond to different fault integral ratios. The controller can determine the fault integral ratio based on the post-oxygen fuel correction value by looking up a table.

[0136] The fault integral ratio, determined based on the oxygen storage capacity, varies with the catalytic converter's operating time. A decrease in oxygen storage capacity leads to significant emissions deterioration and alters the actual air-fuel ratio. Therefore, this factor needs to be excluded when determining if the pre-oxygen sensor is malfunctioning. Consequently, the fault integral ratio under different oxygen storage conditions needs to be determined based on the catalytic converter's oxygen storage capacity. The controller can determine the fault integral ratio by referring to a table based on the estimated or acquired oxygen storage capacity.

[0137] To determine the fault integral ratio, the minimum fault integral ratio can be determined from the fault integral ratio determined based on integral time, the fault integral ratio determined based on oxygen storage, and the fault integral ratio determined based on post-oxygen fuel correction value. If the calculated target integral ratio is less than the minimum fault integral ratio, it indicates that a fault has occurred.

[0138] Alternatively, all three factors can be considered together, and the final fault integral ratio can be calculated by weighting or pre-calibrating.

[0139] The dynamic determination of the fault integral ratio is more in line with actual usage and improves the accuracy of diagnosing faults in the pre-oxygen sensor.

[0140] Figure 4 is a schematic flowchart of the fault diagnosis method for the pre-oxygen sensor provided in this application. As shown in Figure 4, it includes the following steps:

[0141] S301. Determine whether the vehicle meets the diagnostic criteria.

[0142] Diagnostic criteria include:

[0143] 1. The fuel self-learning value based on post-oxygen in this driving cycle must be updated, and the absolute value of the difference between the updated value and the previous value must be greater than 0 and less than the threshold.

[0144] 2. The emission air-fuel ratio control function is activated.

[0145] 3. Whether the atmospheric pressure is within the preset range, the coolant temperature is within the preset range, the vehicle is in a non-interruptible fuel supply state, the vehicle is in a non-carbon canister flushing state and the duration meets the threshold, the engine speed fluctuation is less than the threshold, the engine load fluctuation is less than the threshold, and the cumulative intake air volume of the current driving cycle is greater than the threshold.

[0146] If the diagnostic criteria are not met, no further steps will be taken.

[0147] S302. During the continuous process of air-fuel ratio jump, determine the integral endpoint of the diagnosis.

[0148] First, the time threshold (i.e., the first duration) is obtained by looking up a table based on engine speed and load.

[0149] If the duration of the target air-fuel ratio after the jump is greater than the first duration, then the end time of the first duration is taken as the integration endpoint.

[0150] If the target air-fuel ratio remains in the range after the transition for a duration greater than the pre-set second duration but less than the first duration, the point at which the transition ends is taken as the integration endpoint. At the point at which the transition ends, the emission control state is reversed compared to the previous timing sequence.

[0151] The integration starting point is the moment when the target air-fuel ratio begins to change.

[0152] S303. Determine the target integral ratio within a single diagnostic cycle.

[0153] S304. Obtain the test target integral ratio for multiple diagnostic cycles.

[0154] Multiple diagnostic cycles are greater than or equal to 3.

[0155] S305. Remove the minimum and maximum values ​​from the target integral ratios of multiple diagnostic cycles, and calculate the average integral ratio of the remaining target integral ratios.

[0156] S306. Determine whether the average integral ratio is greater than the preset fault integral ratio.

[0157] S307. If the average integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty.

[0158] S308. If the average integral ratio is less than or equal to the preset fault integral ratio, then the front oxygen sensor is determined to be faulty.

[0159] This embodiment uses the average integral ratio of the target integral ratio over multiple cycles for diagnosis, which can reduce errors.

[0160] Example 1

[0161] Figure 5 is a schematic diagram of the change in target air-fuel ratio and the change in measured air-fuel ratio provided in this application. As shown in Figure 5, the solid line represents the change in target air-fuel ratio, which jumps from time point t1 to time point t2. In this example, the time point from t1 to t2 is set to be longer than the first duration, and the end of the first duration is time point t3. Therefore, the diagnostic state activation period (diagnostic cycle) is from time point t1 to time point t3. During this process, the dashed line represents the change in measured air-fuel ratio. No jump in measured air-fuel ratio was detected within the diagnostic state activation period from time point t1 to time point t3. Therefore, the integral ratio is close to 0, indicating a fault in the front oxygen sensor. Because the slope is always 0 within the diagnostic cycle, a delay fault in the front oxygen sensor is determined.

[0162] Example 2

[0163] Figure 6 is a schematic diagram of the change in target air-fuel ratio and the change in measured air-fuel ratio provided in this application. As shown in Figure 6, the solid line represents the change in target air-fuel ratio, which jumps from time point t1 to time point t2. In this example, the time point from t1 to t2 is set to be longer than the first duration, and the end of the first duration is time point t3. Therefore, the diagnostic state activation period (diagnostic cycle) is from time point t1 to time point t3. During this process, the dashed line represents the change in measured air-fuel ratio. Within the diagnostic state activation period from time point t1 to time point t3, the measured air-fuel ratio keeps increasing. Therefore, the integral ratio is close to 0.5, which is less than the preset 0.7, thus determining that the front oxygen sensor has failed. Because the slope is always greater than the fault slope value within the diagnostic cycle, the number of slope values ​​greater than the fault slope value is greater than the preset number, thus determining that the front oxygen sensor has a slope failure.

[0164] Figure 7 is a schematic diagram of the structure of the fault diagnosis device for the pre-oxygen sensor provided in this application. As shown in Figure 4, the fault diagnosis device 700 for the pre-oxygen sensor provided in this embodiment includes:

[0165] The judgment module 701 is used to determine whether the vehicle currently meets the diagnostic conditions, which include: the change in the fuel correction value before and after the rear oxygen sensor update is less than a preset threshold, and the emission air-fuel ratio control function is activated.

[0166] The first acquisition module 702 is used to acquire the integral value of the measured air-fuel ratio if the diagnostic conditions are met. The integration start point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the integration end point is the time point determined according to the duration of the target air-fuel ratio change.

[0167] The second acquisition module 703 is used to acquire a target integral ratio, wherein the target integral ratio is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio, and the integral range of the integral value of the target air-fuel ratio is the same as the integral range of the integral value of the measured air-fuel ratio.

[0168] The fault determination module 704 is used to determine whether the pre-oxygen sensor has malfunctioned based on the target integral ratio.

[0169] Optionally, the first acquisition module 702 is further configured to:

[0170] Real-time acquisition of the duration for which the target air-fuel ratio begins to change;

[0171] If the duration is longer than the first duration, the end time of the first duration shall be taken as the integral endpoint of the measured air-fuel ratio.

[0172] If the duration is greater than the preset second duration but less than the first duration, then the time point at which the transition ends is taken as the integral endpoint of the measured air-fuel ratio.

[0173] The first duration is determined based on engine speed and load, and the second duration is shorter than the first duration.

[0174] Optionally, the fault determination module 704 is specifically used for:

[0175] Determine whether the target integral ratio is greater than the preset fault integral ratio;

[0176] If the target integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty;

[0177] If the target integral ratio is less than or equal to the fault integral ratio, then the front oxygen sensor is determined to be faulty.

[0178] Optionally, the fault integral ratio is the minimum of the following values: the fault integral ratio determined based on the integral time, the fault integral ratio determined based on the oxygen storage, and the fault integral ratio determined based on the post-oxygen fuel correction value.

[0179] Optionally, the fault determination module 704 is further configured to:

[0180] If a fault is found in the front oxygen sensor, the slope of the measured air-fuel ratio from the start point to the end point within a preset unit time interval is obtained during the duration of the target air-fuel ratio starting to change.

[0181] Based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval, the fault type of the pre-oxygen sensor is determined, including delay fault or slope fault.

[0182] Optionally, the fault determination module 704 is further configured to:

[0183] Obtain the number of slopes with a slope greater than the fault slope value during the duration of the target air-fuel ratio starting to change.

[0184] Determine whether the number of slopes is greater than a preset number;

[0185] If the slope count is greater than the preset count, then the front oxygen sensor is determined to have a slope fault.

[0186] If the slope number is less than or equal to the preset number, then the pre-oxygen sensor is determined to have a delay fault.

[0187] Optionally, the fault determination module 704 is further configured to:

[0188] Obtain the target integral ratio for multiple diagnostic cycles, wherein a diagnostic cycle is defined as the period from the start to the end of a target air-fuel ratio jump.

[0189] Remove the minimum and maximum values ​​from the target integration ratios of the multiple diagnostic cycles, and calculate the average integration ratio of the remaining target integration ratios;

[0190] Determine whether the average integral ratio is greater than the preset fault integral ratio;

[0191] If the average integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty.

[0192] If the average integral ratio is less than or equal to the preset fault integral ratio, then the front oxygen sensor is determined to be faulty.

[0193] Optionally, the diagnostic conditions may further include at least one of the following:

[0194] Atmospheric pressure is within the preset range, coolant temperature is within the preset range, the vehicle is in a non-interruptible fuel supply state, the vehicle is in a non-carbon canister flushing state and the duration meets the threshold, engine speed fluctuation is less than the threshold, engine load fluctuation is less than the threshold, and the cumulative intake air volume of the current driving cycle is greater than the threshold.

[0195] The fault diagnosis device for the pre-oxygen sensor provided in this embodiment can execute the method provided in the above-described method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0196] Figure 8 is a schematic diagram of the controller provided in this application. As shown in Figure 8, the controller 80 provided in this embodiment includes at least one processor 801 and a memory 802. Optionally, the controller 80 further includes a communication component 803. The processor 801, memory 802, and communication component 803 are connected via a bus 804.

[0197] In a specific implementation, at least one processor 801 executes computer execution instructions stored in memory 802, causing at least one processor 801 to perform the above-described method.

[0198] The specific implementation process of processor 801 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0199] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0200] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0201] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0202] This application also provides a vehicle, which includes a controller, a front oxygen sensor and a rear oxygen sensor, the controller being used to implement the above-described method.

[0203] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0204] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0205] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0206] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0207] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0208] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0209] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0210] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0211] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0212] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for diagnosing a fault in a pre-oxygen sensor, the method comprising: Determine whether the vehicle currently meets the diagnostic conditions, which include: the change in fuel correction value before and after the rear oxygen sensor update is less than a preset threshold, and the emission air-fuel ratio control function is activated; If the diagnostic conditions are met, the integral value of the measured air-fuel ratio is obtained. The starting point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the ending point is the time point determined according to the duration of the target air-fuel ratio change. Obtain a target integral ratio, which is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio, and the integral range of the integral value of the target air-fuel ratio is the same as the integral range of the integral value of the measured air-fuel ratio. The pre-oxygen sensor is determined to be faulty based on the target integral ratio.

2. The method according to claim 1, further comprising: Real-time acquisition of the duration for which the target air-fuel ratio begins to change; If the duration is longer than the first duration, the end time of the first duration shall be taken as the integral endpoint of the measured air-fuel ratio. If the duration is greater than the preset second duration but less than the first duration, then the time point at which the transition ends is taken as the integral endpoint of the measured air-fuel ratio. The first duration is determined based on engine speed and load, and the second duration is shorter than the first duration.

3. The method according to claim 1 or 2, wherein determining whether the pre-oxygen sensor has malfunctioned based on the target integral ratio includes: Determine whether the target integral ratio is greater than the preset fault integral ratio; If the target integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty; If the target integral ratio is less than or equal to the fault integral ratio, then the front oxygen sensor is determined to be faulty.

4. The method according to claim 3, wherein, The fault integral ratio is the minimum of the following values: the fault integral ratio determined based on the integral time, the fault integral ratio determined based on the oxygen storage, and the fault integral ratio determined based on the post-oxygen fuel correction value.

5. The method according to claim 3 or 4, further comprising: If a fault is found in the front oxygen sensor, the slope of the measured air-fuel ratio from the start point to the end point within a preset unit time interval is obtained during the duration of the target air-fuel ratio starting to change. Based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval, the fault type of the pre-oxygen sensor is determined, including delay fault or slope fault.

6. The method according to claim 5, wherein determining the fault type of the pre-oxygen sensor based on the slope from the start to the end of the measured air-fuel ratio within each unit time interval includes: Obtain the number of slopes with a slope greater than the fault slope value during the duration of the target air-fuel ratio starting to change. Determine whether the number of slopes is greater than a preset number; If the slope count is greater than the preset count, then the front oxygen sensor is determined to have a slope fault. If the slope number is less than or equal to the preset number, then the pre-oxygen sensor is determined to have a delay fault.

7. The method according to claim 1 or 2, wherein determining whether the pre-oxygen sensor has malfunctioned based on the target integral ratio comprises: Obtain the target integral ratio for multiple diagnostic cycles, wherein a diagnostic cycle is defined as the period from the start to the end of a target air-fuel ratio jump. Remove the minimum and maximum values ​​from the target integration ratios of the multiple diagnostic cycles, and calculate the average integration ratio of the remaining target integration ratios; Determine whether the average integral ratio is greater than the preset fault integral ratio; If the average integral ratio is greater than the preset fault integral ratio, then it is determined that the front oxygen sensor is not faulty. If the average integral ratio is less than or equal to the preset fault integral ratio, then the front oxygen sensor is determined to be faulty.

8. The method according to any one of claims 1-7, wherein, The diagnostic criteria also include at least one of the following: Atmospheric pressure is within the preset range, coolant temperature is within the preset range, the vehicle is in a non-interruptible fuel supply state, the vehicle is in a non-carbon canister flushing state and the duration meets the threshold, engine speed fluctuation is less than the threshold, engine load fluctuation is less than the threshold, and the cumulative intake air volume of the current driving cycle is greater than the threshold.

9. A fault diagnosis device for a pre-oxygen sensor, the device comprising: The judgment module is used to determine whether the vehicle currently meets the diagnostic conditions, which include: the change in the fuel correction value before and after the rear oxygen sensor update is less than a preset threshold, and the emission air-fuel ratio control function is activated. The first acquisition module is used to acquire the integral value of the measured air-fuel ratio if the diagnostic conditions are met. The integration start point of the integral value of the measured air-fuel ratio is the time point at which the target air-fuel ratio begins to change, and the integration end point is the time point determined according to the duration of the target air-fuel ratio change. The second acquisition module is used to acquire a target integral ratio, which is the ratio of the integral value of the measured air-fuel ratio to the integral value of the target air-fuel ratio, and the integral range of the integral value of the target air-fuel ratio is the same as the integral range of the integral value of the measured air-fuel ratio. The fault determination module is used to determine whether the pre-oxygen sensor has malfunctioned based on the target integral ratio.

10. A vehicle comprising: Front oxygen sensor, rear oxygen sensor and controller; The controller is used to perform the method as described in any one of claims 1 to 8.

Images