Method and device for diagnosing response failure of vehicle rear oxygen sensor, and vehicle

Abstract

The application discloses a kind of vehicle rear oxygen sensor response fault diagnosis method, device and vehicle.It includes: the oxygen storage capacity of catalytic converter under different exhaust flow is obtained;According to different exhaust flow and its corresponding oxygen storage capacity, the relationship between exhaust flow and oxygen storage capacity is determined;According to the relationship between exhaust flow and oxygen storage capacity, whether the response of rear oxygen sensor is fault is diagnosed.Under the premise that the original operating condition of vehicle is not changed, the slow response fault of rear oxygen sensor is diagnosed, the stability of entire automobile system is ensured, and the method is not only suitable for traditional car, but also suitable for hybrid electric vehicle.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to vehicle diagnostic technology, and in particular to a method and device for diagnosing a response failure of a rear oxygen sensor of a vehicle. BACKGROUND

[0002] The rear oxygen sensor mainly feeds back the oxygen content behind the three-way catalytic converter to the engine control unit, so as to detect the working condition of the three-way catalytic converter, i.e., the conversion rate of the catalytic converter. Once the rear oxygen sensor fails, the control unit of the electronic fuel injection system cannot obtain the information of the oxygen concentration in the exhaust pipe, and thus cannot perform feedback control on the air-fuel ratio, which will increase the fuel consumption and exhaust pollution of the engine, and cause the engine to have unstable idling, misfire, surge and other failure phenomena.

[0003] Currently, the existing system adopts two ways to perform diagnosis: 1. For a traditional vehicle, the rear oxygen sensor voltage is artificially increased in a deceleration fuel cut condition to diagnose the slow response from rich to lean of the rear oxygen sensor voltage. 2. For a hybrid vehicle, the engine is artificially dragged by the motor through torque setting to create a fuel cut condition to diagnose the slow response from rich to lean of the rear oxygen sensor voltage.

[0004] Problems in the prior art are as follows: 1. For a traditional vehicle, increasing the rear oxygen voltage makes the mixture rich and increases fuel consumption. 2. For a hybrid vehicle, the engine is dragged by the motor for too many times, which affects the service life of the motor. SUMMARY

[0005] The present application provides a method and device for diagnosing a response failure of a rear oxygen sensor of a vehicle, which realizes diagnosis of the slow response failure of the rear oxygen sensor without changing the original operating condition of the vehicle, and ensures the stability of the entire vehicle system.

[0006] In a first aspect, the present application provides a method for diagnosing a response failure of a rear oxygen sensor of a vehicle, comprising:

[0007] obtaining the oxygen storage capacity of a catalytic converter under different exhaust flow rates;

[0008] determining the relationship between the exhaust flow rate and the oxygen storage capacity according to different exhaust flow rates and their corresponding oxygen storage capacities;

[0009] diagnosing whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow rate and the oxygen storage capacity.

[0010] Further, obtaining the oxygen storage capacity of a catalytic converter under different exhaust flow rates comprises:

[0011] obtaining the current oxygen storage capacity of the catalytic converter under the current exhaust flow rate;

[0012] set the exhaust flow rate as a next exhaust flow rate, and obtain a next oxygen storage amount of the catalyst under the next exhaust flow rate.

[0013] Further, when setting the exhaust flow rate as a next exhaust flow rate, further comprising:

[0014] The difference between the different exhaust flow rates is greater than a first threshold.

[0015] Further, when setting the exhaust flow rate as a next exhaust flow rate, further comprising:

[0016] The difference between the different exhaust flow rates is greater than a first threshold.

[0017] Further, according to the different exhaust flow rates and their corresponding oxygen storage amounts, a relationship between the exhaust flow rate and the oxygen storage amount is determined, comprising:

[0018] According to the different exhaust flow rates and their corresponding oxygen storage amounts, a coordinate point in a coordinate system of the exhaust flow rate and the oxygen storage amount is determined.

[0019] According to the coordinate point of the exhaust flow rate and the oxygen storage amount, a linear relationship between the exhaust flow rate and the oxygen storage amount is fitted.

[0020] Further, according to the relationship between the exhaust flow rate and the oxygen storage amount, whether the response of the rear oxygen sensor is faulty is diagnosed, comprising:

[0021] According to the coordinate point of the exhaust flow rate and the oxygen storage amount, a linear slope of the exhaust flow rate and the oxygen storage amount is determined.

[0022] When the linear slope is greater than a second threshold, it is diagnosed that the response of the rear oxygen sensor is faulty.

[0023] Further, before obtaining the oxygen storage amounts of the catalyst under different exhaust flow rates, further comprising:

[0024] Setting an operating state of the vehicle as an enabled state for the response fault diagnosis of the rear oxygen sensor; wherein the operating state includes engine speed, exhaust flow rate, catalyst temperature, front oxygen sensor operating state, and rear oxygen sensor operating state.

[0025] In a second aspect, the embodiments of the present application also provide a vehicle rear oxygen sensor response fault diagnosis device, comprising:

[0026] An obtaining module is configured to obtain oxygen storage amounts of a catalyst under different exhaust flow rates;

[0027] A determining module is configured to determine a relationship between the exhaust flow rate and the oxygen storage amount according to the different exhaust flow rates and their corresponding oxygen storage amounts.

[0028] A diagnosis module is configured to diagnose whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow and the oxygen storage amount.

[0029] Further, the determination module comprises:

[0030] A coordinate point determination unit is configured to determine a coordinate point in an exhaust flow and oxygen storage amount coordinate system according to different exhaust flows and corresponding oxygen storage amounts.

[0031] A fitting unit is configured to fit a linear relationship between the exhaust flow and the oxygen storage amount according to the coordinate points of the exhaust flow and the oxygen storage amount.

[0032] In a third aspect, the embodiments of the present application further provide a vehicle comprising the diagnosis device for diagnosing a response fault of a rear oxygen sensor of the vehicle according to any one of the embodiments of the present application.

[0033] The present application obtains the oxygen storage amount of the catalyst under different exhaust flows, determines the relationship between the exhaust flow and the oxygen storage amount according to different exhaust flows and corresponding oxygen storage amounts, and diagnoses whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow and the oxygen storage amount. When the relationship between the exhaust flow and the oxygen storage amount is positive correlation, it can be judged that the rear oxygen sensor is faulty. The calculated increase in the oxygen storage amount of the catalyst indicates that the rear oxygen sensor is abnormal. Thus, the diagnosis of the slow response fault of the rear oxygen sensor can be realized without changing the original operating conditions of the vehicle, the stability of the entire automobile system is ensured, and the method is applicable to not only traditional vehicles but also hybrid vehicles, as long as the vehicle operating conditions include exhaust flow changes. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 FIG. 1 is a flowchart of a diagnosis method for a response fault of a rear oxygen sensor of a vehicle according to an embodiment of the present application.

[0035] Figure 2 FIG. 2 is a flowchart of a diagnosis method for a response fault of a rear oxygen sensor of a vehicle according to another embodiment of the present application.

[0036] Figure 3 FIG. 3 is a diagram showing the fitting relationship of coordinate points of an exhaust flow and an oxygen storage amount when the response of a rear oxygen sensor is normal in the embodiment two of the present application.

[0037] Figure 4 FIG. 4 is a diagram showing the fitting relationship of coordinate points of an exhaust flow and an oxygen storage amount when the response of a rear oxygen sensor is slow in the embodiment two of the present application.

[0038] Figure 5 FIG. 5 is a structural diagram of a diagnosis device for a response fault of a rear oxygen sensor of a vehicle according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] The application will be described in further detail below with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not to be used to limit the scope of the application. In addition, it should be noted that, for the sake of brevity, only the portions of the drawings that are necessary for an understanding of the application will be described.

[0040] Embodiment one

[0041] Figure 1 A flow chart of a diagnostic method for a vehicle rear oxygen sensor response fault is provided for the first embodiment of the application. The embodiment can be applied to the diagnostic method for a rear oxygen sensor fault of a traditional fuel automobile or a hybrid vehicle. The method can be executed by a diagnostic device for a vehicle rear oxygen sensor response fault and specifically includes the following steps:

[0042] S110, obtaining the oxygen storage capacity of the catalytic converter under different exhaust flow rates;

[0043] The exhaust flow rate is the flow rate of the exhaust gas emitted by the vehicle engine. When the driving conditions of the vehicle are different, the exhaust flow rate can be different. Illustratively, when the accelerator of the vehicle is increased, the exhaust flow rate is large; when the accelerator of the vehicle is decreased, the exhaust flow rate is small. The catalytic converter includes a three-way catalytic converter and is installed in the exhaust pipe of the automobile. The catalytic converter can convert the harmful gases such as CO, HC and NOx emitted by the automobile exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction. A front oxygen sensor is placed in front of the catalytic converter to detect the oxygen content in the exhaust gas and feed back to the engine control unit. The engine control unit corrects the fuel injection amount according to the signal. A rear oxygen sensor is placed behind the catalytic converter to feed back the oxygen content in the gas discharged by the catalytic converter to the engine control unit to detect the conversion rate of the catalytic converter and thus determine the quality of the catalytic converter. The catalytic converter itself has the function of storing oxygen. When the front oxygen sensor detects a signal that the oxygen content in the exhaust gas becomes lean, the rear oxygen sensor detects a signal that the oxygen content in the exhaust gas becomes lean compared to the signal detected by the front oxygen sensor. There is a time difference between the two signals. The rear oxygen sensor can detect the signal that the oxygen content in the exhaust gas becomes lean after a period of time. Therefore, when the exhaust flow rate is different, the exhaust gas emitted by the vehicle passes through the catalytic converter at different times. The time when the front oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean is defined as the initial time. The time when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean is different. The greater the exhaust flow rate, the faster the exhaust gas emitted by the vehicle passes through the catalytic converter, the shorter the time, and the faster the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean. At this time, the oxygen storage capacity of the catalytic converter is smaller. The smaller the exhaust flow rate, the longer the exhaust gas emitted by the vehicle passes through the catalytic converter, and the slower the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean. At this time, the oxygen storage capacity of the catalytic converter is larger.

[0044] S120, determining the relationship between the exhaust flow and the oxygen storage capacity according to different exhaust flows and their corresponding oxygen storage capacities;

[0045] In the embodiment, the mapping relationship between the exhaust flow and the oxygen storage capacity is determined according to each exhaust flow and the oxygen storage capacity of the corresponding catalytic converter.

[0046] S130, diagnosing whether the response of the downstream oxygen sensor is faulty according to the relationship between the exhaust flow and the oxygen storage capacity.

[0047] In the embodiment, the active lean time of the upstream oxygen sensor is fixed because the catalytic converter itself has the function of storing oxygen. When the exhaust flow increases, the exhaust gas exists in the catalytic converter for a short time, and the exhaust gas does not fully react with the noble metal in the catalytic converter. Therefore, the lean time of the exhaust gas detected by the downstream oxygen sensor becomes smaller, and the calculated oxygen storage capacity of the catalytic converter decreases. When the exhaust flow passing through the catalytic converter is constant, the oxygen storage capacity of the catalytic converter is a constant value and is only affected by the deterioration degree of the downstream oxygen sensor. When the response of the downstream oxygen sensor is slow, the signal time of the oxygen content in the exhaust gas detected by the downstream oxygen sensor becomes larger, and the calculated oxygen storage capacity of the catalytic converter becomes larger. When the exhaust flow increases, the calculated oxygen storage capacity of the catalytic converter decreases for the normal downstream oxygen sensor, and the calculated oxygen storage capacity of the catalytic converter increases for the abnormal downstream oxygen sensor.

[0048] After the relationship between the exhaust flow and the oxygen storage capacity of the catalytic converter is determined, whether the response of the downstream oxygen sensor is faulty is diagnosed according to the linear relationship between the exhaust flow and the oxygen storage capacity. When the exhaust flow increases, the oxygen storage capacity of the catalytic converter decreases, and the exhaust flow and the oxygen storage capacity of the catalytic converter are negatively correlated. At this time, it is determined that the response of the downstream oxygen sensor is normal. The oxygen storage capacity of the catalytic converter increases, and the exhaust flow and the oxygen storage capacity of the catalytic converter are positively correlated. At this time, it is determined that the response of the downstream oxygen sensor is faulty. Therefore, whether the response of the downstream oxygen sensor is faulty can be diagnosed according to the relationship between the exhaust flow and the oxygen storage capacity.

[0049] It should be noted that the technical solution of the embodiment is to diagnose the downstream oxygen sensor according to the working condition of the vehicle during normal driving. The change of the exhaust flow is also the automatic change of the exhaust flow during normal driving, and the exhaust flow of the vehicle is not actively controlled. Therefore, the diagnosis of the downstream oxygen sensor can be completed during normal driving of the vehicle, and the original driving condition of the vehicle and the working mode of the engine and the generator are not changed.

[0050] The technical scheme of the embodiment obtains the oxygen storage capacity of the catalytic converter under different exhaust flow rates, determines the relationship between the exhaust flow rate and the oxygen storage capacity according to different exhaust flow rates and the corresponding oxygen storage capacities, and can directly diagnose whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow rate and the oxygen storage capacity. When the relationship between the exhaust flow rate and the oxygen storage capacity is positive correlation, it can be judged that the rear oxygen sensor is faulty. Thus, the fault of the slow response of the rear oxygen sensor can be diagnosed without changing the original operating condition of the vehicle, the stability of the entire automobile system is ensured, and the method is suitable for both traditional vehicles and hybrid vehicles as long as the vehicle operating condition contains exhaust flow rate changes.

[0051] Embodiment Two

[0052] Figure 2 The flowchart of the diagnostic method for the response fault of the rear oxygen sensor of the vehicle provided in Embodiment Two of the application is optimized on the basis of the above-mentioned embodiment. Referring to Figure 2 , the method of the embodiment includes but is not limited to the following steps:

[0053] S210, setting the operating state of the vehicle to an enabled state for diagnosing the response fault of the rear oxygen sensor; wherein the operating state includes engine speed, exhaust flow rate, catalytic converter temperature, front oxygen sensor working state and rear oxygen sensor working state;

[0054] Before obtaining the oxygen storage capacity of the catalytic converter under different exhaust flow rates, the operating state of the vehicle is set to meet the enabled state for diagnosing the response fault of the rear oxygen sensor, for example, the engine speed is in the diagnostic window

n1, n2

m1, m2

[0055] S220, obtaining the current oxygen storage capacity of the catalytic converter under the current exhaust flow rate;

[0056] Specifically, the oxygen storage capacity of the catalyst under different exhaust flow rates can be calculated according to the signal change time of the front oxygen sensor and the signal change time of the rear oxygen sensor, and the oxygen storage capacity calculation formula of the catalyst is:

[0057]

[0058] Wherein, OSC represents the oxygen storage capacity of the catalyst, lambda represents the front oxygen excess air coefficient, M represents the exhaust mass flow rate, t1 represents the time when the front oxygen sensor actively reduces the lean mixture, and t2 represents the time when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean.

[0059] S230, set the exhaust flow rate to the next exhaust flow rate, and obtain the next oxygen storage capacity of the catalyst under the next exhaust flow rate;

[0060] Specifically, the exhaust flow rate can be changed by the opening degree of the accelerator pedal. For example, when the car accelerates, the intake amount also increases by stepping on the accelerator pedal to give oil, and the exhaust flow rate also increases; when the car climbs, the engine speed remains unchanged by stepping on the accelerator pedal to give oil, the intake amount increases, and the exhaust flow rate also increases.

[0061] Optionally, when the exhaust flow rate is set to the next exhaust flow rate, it also includes: setting the difference between different exhaust flow rates to be greater than a first threshold value.

[0062] Wherein, by setting the first threshold value, the difference between high and low exhaust flow rates is greater than the first threshold value, and the first threshold value can be 15g / s. By setting this, the exhaust flow rate has a greater impact on the oxygen storage capacity of the catalyst, which facilitates the calculation of the slope of the coordinate graph fitted by the coordinate points of the exhaust flow rate and the oxygen storage capacity, and can improve the diagnosis accuracy of the rear oxygen sensor.

[0063] Through the above-mentioned oxygen storage capacity calculation formula of the catalyst, the oxygen storage capacity of the catalyst under different exhaust flow rates can be calculated according to the signal change time of the front oxygen sensor and the signal change time of the rear oxygen sensor.

[0064] S240, determining the coordinate points in the exhaust flow rate and oxygen storage capacity coordinate system according to different exhaust flow rates and their corresponding oxygen storage capacities;

[0065] Specifically, the exhaust flow rate is taken as the horizontal coordinate, and the oxygen storage capacity is taken as the vertical coordinate to determine the coordinate points in the exhaust flow rate and oxygen storage capacity coordinate system, so that the linear relationship between the exhaust flow rate and the oxygen storage capacity of the catalyst can be judged through the coordinate points in the subsequent process.

[0066] Wherein, the oxygen storage capacity calculation formula of the catalyst is:

[0067]

[0068] Wherein, OSC represents the oxygen storage capacity of the catalyst, lambda represents the front oxygen excess air coefficient, M represents the exhaust mass flow, t1 represents the time when the front oxygen sensor actively reduces the lean mixture, and t2 represents the time when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean.

[0069] It can be seen that when lambda is a fixed value, the time when t1 starts to calculate is a fixed value, and OSC is mainly affected by the exhaust flow and the time t2 when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean. When the exhaust flow is large, because the exhaust gas exists in the catalyst for a short time, and the exhaust gas does not fully react with the noble metal in the catalyst, the value of t2 becomes small. When the exhaust flow becomes large, the calculated OSC value will become small. The time t2 when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean is affected by the oxygen storage capacity of the catalyst and the deterioration of the rear oxygen sensor. When the catalyst is certain, the oxygen storage capacity is a fixed value, and only affected by the degree of deterioration of the rear oxygen sensor. When the rear oxygen sensor responds slowly, the time t2 when the rear oxygen sensor detects the signal that the oxygen content in the exhaust gas becomes lean becomes large, so the calculated OSC value will become large.

[0070] S250, fitting the linear relationship between the exhaust flow and the oxygen storage capacity according to the coordinate points of the exhaust flow and the oxygen storage capacity;

[0071] Wherein, in the coordinate system where the abscissa represents the exhaust flow and the ordinate represents the oxygen storage capacity, the coordinate points determined by different exhaust flows and corresponding oxygen storage capacities can be fitted into a straight line as the linear relationship between the exhaust flow and the oxygen storage capacity.

[0072] When the rear oxygen sensor responds normally, the relationship between the coordinate points of the exhaust flow and the oxygen storage capacity is schematically shown as Figure 3 , as shown in Figure 3 , the abscissa represents the exhaust flow, the ordinate represents the oxygen storage capacity, and the calculated oxygen storage capacity of the catalyst decreases with the increase of the exhaust flow when the rear oxygen sensor responds normally.

[0073] When the rear oxygen sensor responds slowly (for example, delayed by 1s), the relationship between the coordinate points of the exhaust flow and the oxygen storage capacity is schematically shown as Figure 4 , as shown in Figure 4 , the abscissa represents the exhaust flow, the ordinate represents the oxygen storage capacity, and the calculated oxygen storage capacity of the catalyst increases with the increase of the exhaust flow when the rear oxygen sensor responds slowly.

[0074] S260, determining the linear slope of the exhaust flow and the oxygen storage capacity according to the linear relationship between the exhaust flow and the oxygen storage capacity fitted by the coordinate points of the exhaust flow and the oxygen storage capacity;

[0075] According to the linear relationship between the exhaust flow and the oxygen storage capacity fitted by the coordinate points of the exhaust flow and the oxygen storage capacity, it can be obtained that when the rear oxygen sensor responds normally, as Figure 3As shown, the oxygen storage capacity of the catalytic converter decreases with increasing exhaust flow rate, and the linear slope is negative; when the after-oxygen sensor responds slowly, such as... Figure 4 As shown, the oxygen storage capacity of the catalytic converter increases with the increase of exhaust flow rate, and the linear slope is positive.

[0076] S270. When the linear slope is greater than the second threshold, diagnose the response fault of the oxygen sensor.

[0077] Specifically, when determining whether the post-oxygen sensor has a slow response fault based on the linear slope, a second threshold can be set to a positive value, such as 0.05. When the linear slope of the coordinate points of exhaust flow rate and oxygen storage is greater than the second threshold, the post-oxygen sensor is diagnosed as having a slow response fault; otherwise, the post-oxygen sensor responds normally, and the diagnosis is complete.

[0078] The technical solution of this embodiment calculates the oxygen storage capacity of the catalytic converter corresponding to different exhaust flow rates, finds the linear relationship between the oxygen storage capacity of the catalytic converter and the exhaust flow rate, obtains the linear slope based on this linear relationship, and compares the slope value with the second threshold. When the slope value is greater than the second threshold, a fault in the response of the rear oxygen sensor can be diagnosed. That is, when the relationship between exhaust flow rate and oxygen storage capacity is positively correlated, a fault in the rear oxygen sensor can be determined. Thus, without changing the original operating conditions of the vehicle, the fault of slow response of the rear oxygen sensor can be diagnosed, ensuring the stability of the entire vehicle system. Moreover, this method is applicable not only to conventional vehicles but also to hybrid vehicles, as long as the vehicle's operating conditions include changes in exhaust flow rate.

[0079] Example 3

[0080] Figure 5 This is a schematic diagram of a diagnostic device for a vehicle rear oxygen sensor response fault according to Embodiment 3 of the present invention. This device can perform the diagnostic methods for vehicle rear oxygen sensor response faults involved in the above embodiments. (Refer to...) Figure 3 The device includes: an acquisition module 310, a determination module 320, and a diagnostic module 330.

[0081] The acquisition module 310 is used to acquire the oxygen storage capacity of the catalytic converter under different exhaust flow rates;

[0082] The determination module 320 is used to determine the relationship between exhaust flow rate and oxygen storage capacity based on different exhaust flow rates and their corresponding oxygen storage capacity.

[0083] Specifically, the determining module 320 includes: a coordinate point determining unit, used to determine the coordinate points in the coordinate system of exhaust flow rate and oxygen storage capacity according to different exhaust flow rates and their corresponding oxygen storage capacity;

[0084] The fitting unit is used to fit the linear relationship between exhaust flow rate and oxygen storage capacity based on the coordinate points of exhaust flow rate and oxygen storage capacity.

[0085] The diagnostic module 330 is configured to diagnose whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow and the oxygen storage amount.

[0086] The scheme of the embodiment can obtain the oxygen storage amount of the catalyst under different exhaust flows through the obtaining module, determine the relationship between the exhaust flow and the oxygen storage amount according to different exhaust flows and the corresponding oxygen storage amounts through the determining module, and diagnose whether the response of the rear oxygen sensor is faulty according to the relationship between the exhaust flow and the oxygen storage amount through the diagnostic module. When the relationship between the exhaust flow and the oxygen storage amount is positive correlation, it can be judged that the rear oxygen sensor is faulty. The device can diagnose the slow response fault of the rear oxygen sensor without changing the original operating conditions of the vehicle, ensure the stability of the entire automobile system, and is suitable for traditional vehicles and hybrid vehicles as long as the vehicle operating conditions contain exhaust flow changes.

[0087] In an optional implementation of the embodiment, the obtaining module 310 is specifically configured to: obtain the current oxygen storage amount of the catalyst under the current exhaust flow; set the exhaust flow as the next exhaust flow and obtain the next oxygen storage amount of the catalyst under the next exhaust flow; and set the difference of different exhaust flows to be greater than a first threshold value.

[0088] The oxygen storage amount of the catalyst under different exhaust flows is calculated according to the signal change time of the front oxygen sensor and the signal change time of the rear oxygen sensor.

[0089] In an optional implementation of the embodiment, the diagnostic module 330 is specifically configured to: determine the linear slope of the exhaust flow and the oxygen storage amount according to the coordinate points of the exhaust flow and the oxygen storage amount fitting the linear relationship between the exhaust flow and the oxygen storage amount; and diagnose the response fault of the rear oxygen sensor when the linear slope is greater than a second threshold value.

[0090] In an optional implementation of the embodiment, the obtaining module 310 further includes, before obtaining the oxygen storage amount of the catalyst under different exhaust flows: setting the operating state of the vehicle as an enabled state for diagnosing the response fault of the rear oxygen sensor; and the operating state includes engine speed, exhaust flow, catalyst temperature, front oxygen sensor working state and rear oxygen sensor working state.

[0091] The vehicle rear oxygen sensor response fault diagnosis device provided in the embodiment can execute the vehicle rear oxygen sensor response fault diagnosis method provided in any embodiment of the application, and has the corresponding function modules and beneficial effects of the execution method.

[0092] Embodiment Four

[0093] The fourth embodiment of the present application provides a vehicle, which comprises the diagnosis device for the response failure of the rear oxygen sensor of the vehicle in any of the above embodiments, so as to realize the diagnosis of the response failure of the rear oxygen sensor without changing the original driving condition of the vehicle, without changing the working mode of the engine and the generator of the vehicle, and ensure the stability of the whole vehicle system. The vehicle can be a traditional vehicle or a hybrid vehicle, as long as the driving condition of the vehicle contains the change of the exhaust flow.

[0094] Of course, the vehicle provided by the embodiments of the present application includes but is not limited to the diagnosis device for the response failure of the rear oxygen sensor of the vehicle as described above, and can also perform the related operations in the diagnosis method for the response failure of the rear oxygen sensor of the vehicle provided by any of the embodiments of the present application.

[0095] It is worth noting that in the above embodiments of the diagnosis device for the response failure of the rear oxygen sensor of the vehicle, each module is only divided according to the functional logic, but is not limited to the above division, as long as the corresponding function can be realized. In addition, the specific names of each functional unit are only for easy mutual differentiation, and are not used to limit the protection scope of the present application.

[0096] It is noted that the above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, re-adjustments and substitutions without departing from the protection scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for diagnosing a fault in the response of a vehicle's rear oxygen sensor, characterized in that, include: To obtain the oxygen storage capacity of the catalytic converter under different exhaust flow rates; The relationship between exhaust flow rate and oxygen storage capacity is determined based on the different exhaust flow rates and their corresponding oxygen storage capacities. The oxygen sensor response was diagnosed as faulty based on the relationship between the exhaust flow rate and the oxygen storage capacity. Wherein, the exhaust flow rate is the flow rate of exhaust gas discharged from the vehicle engine; when the rear oxygen sensor responds normally, the oxygen storage capacity of the catalyst decreases as the exhaust flow rate increases; when the rear oxygen sensor responds slowly, the oxygen storage capacity of the catalyst increases as the exhaust flow rate increases.

2. The method according to claim 1, characterized in that, Obtain the oxygen storage capacity of the catalytic converter under different exhaust flow rates, including: Obtain the current oxygen storage capacity of the catalyst at the current exhaust flow rate; The exhaust flow rate is set as the next exhaust flow rate, and the next oxygen storage capacity of the catalyst under the next exhaust flow rate is obtained.

3. The method according to claim 2, characterized in that, When setting the exhaust flow rate as the next exhaust flow rate, the following is also included: The difference between the different exhaust flow rates is set to be greater than a first threshold.

4. The method according to any one of claims 1-3, characterized in that, Obtain the oxygen storage capacity of the catalytic converter under different exhaust flow rates, including: Under different exhaust flow rates, the oxygen storage capacity of the catalyst is calculated based on the signal change times of the front oxygen sensor and the rear oxygen sensor.

5. The method according to claim 1, characterized in that, The relationship between exhaust flow rate and oxygen storage capacity is determined based on different exhaust flow rates and their corresponding oxygen storage capacities, including: The coordinate points in the coordinate system of exhaust flow rate and oxygen storage capacity are determined according to the different exhaust flow rates and their corresponding oxygen storage capacities. The linear relationship between the exhaust flow rate and the oxygen storage capacity is fitted based on the coordinate points of the exhaust flow rate and the oxygen storage capacity.

6. The method according to claim 5, characterized in that, Diagnosing whether the oxygen sensor response is faulty based on the relationship between the exhaust flow rate and the oxygen storage capacity includes: The linear slope of the relationship between exhaust flow rate and oxygen storage capacity is determined by fitting the coordinate points of the exhaust flow rate and oxygen storage capacity. When the linear slope is greater than the second threshold, a response fault of the post-oxygen sensor is diagnosed.

7. The method according to claim 1, characterized in that, Before obtaining the oxygen storage capacity of the catalytic converter under different exhaust flow rates, the following steps are also included: The vehicle's operating state is set to the enabled state for fault diagnosis of the rear oxygen sensor; wherein the operating state includes engine speed, exhaust flow, catalytic converter temperature, operating state of the front oxygen sensor, and operating state of the rear oxygen sensor.

8. A diagnostic device for a vehicle rear oxygen sensor response fault, characterized in that, include: The acquisition module is used to acquire the oxygen storage capacity of the catalytic converter under different exhaust flow rates; The determination module is used to determine the relationship between exhaust flow rate and oxygen storage capacity based on different exhaust flow rates and their corresponding oxygen storage capacity; The diagnostic module is used to diagnose whether the response of the rear oxygen sensor is faulty based on the relationship between the exhaust flow rate and the oxygen storage capacity; wherein, the exhaust flow rate is the flow rate of the exhaust gas discharged from the vehicle engine; when the rear oxygen sensor responds normally, the oxygen storage capacity of the catalyst decreases as the exhaust flow rate increases; when the rear oxygen sensor responds slowly, the oxygen storage capacity of the catalyst increases as the exhaust flow rate increases.

9. The diagnostic device for vehicle rear oxygen sensor response failure according to claim 8, characterized in that, The determining module includes: The coordinate point determination unit is used to determine the coordinate point in the coordinate system of exhaust flow rate and oxygen storage capacity according to the different exhaust flow rates and their corresponding oxygen storage capacity. The fitting unit is used to fit the linear relationship between the exhaust flow rate and the oxygen storage capacity based on the coordinate points of the exhaust flow rate and the oxygen storage capacity.

10. A vehicle, characterized in that, The diagnostic device for vehicle rear oxygen sensor response failure as described in claim 8 or 9.

Images