Fault diagnosis method, device, vehicle and storage medium for low SCR conversion efficiency

Abstract

The present invention discloses a method, device, vehicle and storage medium for diagnosing the fault of low SCR conversion efficiency. The method for diagnosing the fault of low SCR conversion efficiency includes: after the active diagnosis of SCR conversion efficiency meets the active diagnosis release condition, controlling the urea injection system to enter the reduced injection stage, over-injection stage, and stop injection stage; obtaining the fourth set ammonia storage at the end of the stop injection stage of the urea injection system, and obtaining the integrated mass flow of NOx upstream of the first SCR and the integrated mass flow of NOx downstream of the first SCR during the process of increasing the ammonia storage from the second set ammonia storage to the third set ammonia storage in the over-injection stage, as well as the integrated mass flow of NOx upstream of the second SCR and the integrated mass flow of NOx downstream of the second SCR during the process of reducing the ammonia storage from the third set ammonia storage to the fourth set ammonia storage in the stop injection stage, and determining whether there is a fault of low SCR conversion efficiency in the current SCR box. The present invention realizes the improvement of the diagnosis accuracy of SCR conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of SCR post-treatment systems, and particularly to a method and device for diagnosing low SCR conversion efficiency faults, a vehicle, and a storage medium. Background Art

[0002] Selective Catalytic Reduction (SCR) technology is a treatment process for NOx in diesel vehicle exhaust emissions. That is, under the action of a catalyst, a reducing agent such as ammonia or urea is injected to reduce NOx in the exhaust gas to N2 and H2O.

[0003] Due to the extremely harsh working environment of the SCR catalytic converter itself and the influence of its chemical conversion and reduction characteristics, various different faults will also occur during use, which will lead to low NOx conversion efficiency of the SCR system. Currently, the method for diagnosing NOx conversion efficiency of traditional SCR systems is to passively collect NOx data upstream and downstream of the SCR and calculate the average NOx conversion efficiency. This method is affected by environmental, operating conditions, and control factors, has poor robustness, and a high risk of false alarms. Especially for some engines with high-altitude emissions, it is necessary to improve the robustness of SCR conversion efficiency diagnosis. Summary of the Invention

[0004] The present invention provides a method and device for diagnosing low SCR conversion efficiency faults, a vehicle, and a storage medium to solve the problems that the current SCR conversion efficiency diagnosis method has poor robustness and a high risk of false alarms due to being affected by environmental, operating conditions, and control factors.

[0005] According to one aspect of the present invention, a method for diagnosing low SCR conversion efficiency faults is provided. The method for diagnosing low SCR conversion efficiency faults includes:

[0006] When the engine is running normally, the SCR passive diagnosis conversion efficiency is obtained through passive diagnosis of the SCR conversion efficiency, and the active diagnosis of the SCR conversion efficiency is triggered according to the SCR passive diagnosis conversion efficiency;

[0007] After the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the urea injection system is controlled to enter the reduced injection stage, the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage are obtained, and the urea injection system is controlled to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage;

[0008] The second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage are recorded, and the urea injection system is controlled to enter the stop injection stage according to the second set ammonia storage and the third set ammonia storage;

[0009] Obtain the fourth set ammonia storage at the end of the injection stop stage of the urea injection system, and obtain the integral of the NOx mass flow rate upstream of the first SCR and the integral of the NOx mass flow rate downstream of the first SCR during the process of the over-injection stage increasing from the second set ammonia storage to the third set ammonia storage, as well as the integral of the NOx mass flow rate upstream of the second SCR and the integral of the NOx mass flow rate downstream of the second SCR during the process of the injection stop stage decreasing from the third set ammonia storage to the fourth set ammonia storage;

[0010] Determine whether there is a low SCR conversion efficiency fault in the current SCR box according to the integral of the NOx mass flow rate upstream of the first SCR, the integral of the NOx mass flow rate downstream of the first SCR, the integral of the NOx mass flow rate upstream of the second SCR, and the integral of the NOx mass flow rate downstream of the second SCR.

[0011] Optionally, the SCR passive diagnosis conversion efficiency is obtained through SCR conversion efficiency passive diagnosis, and the SCR conversion efficiency active diagnosis is triggered according to the SCR passive diagnosis conversion efficiency, including:

[0012] After the SCR conversion efficiency passive diagnosis meets the passive diagnosis release condition, calculate the SCR passive diagnosis conversion efficiency;

[0013] When the SCR passive diagnosis conversion efficiency is lower than the passive diagnosis conversion efficiency limit value and the SCR conversion efficiency active diagnosis meets the active diagnosis release condition, trigger the SCR conversion efficiency active diagnosis.

[0014] Optionally, before triggering the SCR conversion efficiency active diagnosis, it further includes:

[0015] Control the SCR conversion efficiency active diagnosis to be in the initial waiting stage.

[0016] Optionally, the control of the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage includes:

[0017] When the initial ammonia storage decreases to the first set ammonia storage and the real-time SCR conversion efficiency is lower than the set SCR conversion efficiency threshold, control the urea injection system to enter the over-injection stage.

[0018] Optionally, the control of the urea injection system to enter the injection stop stage according to the second set ammonia storage and the third set ammonia storage includes:

[0019] When the second set ammonia storage increases to the third set ammonia storage, control the urea injection system to enter the injection stop stage.

[0020] Optionally, obtaining the fourth set ammonia storage at the end of the injection stop stage of the urea injection system includes:

[0021] When the urea injection system is in the injection stop stage, reduce the third set ammonia storage until the end of the injection stop stage to obtain the fourth set ammonia storage.

[0022] Optionally, determining whether there is a low SCR conversion efficiency fault in the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral includes:

[0023] Determine the target SCR conversion efficiency of the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral;

[0024] If the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value, it is determined that there is a low SCR conversion efficiency fault in the current SCR box;

[0025] If the target SCR conversion efficiency is not lower than the active diagnosis conversion efficiency limit value, it is determined that the SCR conversion efficiency of the current SCR box is normal.

[0026] According to another aspect of the present invention, a device for diagnosing low SCR conversion efficiency faults is provided. The device for diagnosing low SCR conversion efficiency faults includes:

[0027] An active diagnosis trigger module, configured to, when the engine is running normally, obtain the SCR passive diagnosis conversion efficiency through passive diagnosis of the SCR conversion efficiency, and trigger the active diagnosis of the SCR conversion efficiency according to the SCR passive diagnosis conversion efficiency;

[0028] An overspray stage entry module, configured to, after the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, control the urea injection system to enter the reduced injection stage, obtain the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage, and control the urea injection system to enter the overspray stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage;

[0029] An injection stop stage entry module, configured to record the second set ammonia storage and the third set ammonia storage when the urea injection system is in the overspray stage, and control the urea injection system to enter the injection stop stage according to the second set ammonia storage and the third set ammonia storage;

[0030] The NOx mass flow integral acquisition module is configured to obtain the fourth set ammonia storage at the end of the injection stop phase of the urea injection system, and obtain the NOx mass flow integral upstream of the first SCR and the NOx mass flow integral downstream of the first SCR during the process of the over-injection phase increasing from the second set ammonia storage to the third set ammonia storage, and the NOx mass flow integral upstream of the second SCR and the NOx mass flow integral downstream of the second SCR during the process of the injection stop phase decreasing from the third set ammonia storage to the fourth set ammonia storage;

[0031] The fault judgment module is configured to determine whether there is a low SCR conversion efficiency fault in the current SCR box according to the NOx mass flow integral upstream of the first SCR, the NOx mass flow integral downstream of the first SCR, the NOx mass flow integral upstream of the second SCR, and the NOx mass flow integral downstream of the second SCR.

[0032] According to another aspect of the present invention, there is provided a vehicle, the vehicle comprising:

[0033] At least one processor; and

[0034] A memory communicatively connected to the at least one processor; wherein,

[0035] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the low SCR conversion efficiency fault diagnosis method according to any embodiment of the present invention.

[0036] According to another aspect of the present invention, there is provided a computer-readable storage medium storing computer instructions for causing a processor to implement the low SCR conversion efficiency fault diagnosis method according to any embodiment of the present invention when executed.

[0037] In the technical solution of the embodiment of the present invention, when the engine is running normally, the SCR passive diagnosis conversion efficiency is obtained through the passive diagnosis of the SCR conversion efficiency, and the active diagnosis of the SCR conversion efficiency is triggered according to the SCR passive diagnosis conversion efficiency; after the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the urea injection system is controlled to enter the reduced injection stage, the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage are obtained, and the urea injection system is controlled to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage; the second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage are recorded, and the urea injection system is controlled to enter the stop injection stage according to the second set ammonia storage and the third set ammonia storage; the fourth set ammonia storage at the end of the stop injection stage of the urea injection system is obtained, and the first SCR upstream NOx mass flow integral and the first SCR downstream NOx mass flow integral during the process of increasing from the second set ammonia storage to the third set ammonia storage in the over-injection stage, and the second SCR upstream NOx mass flow integral and the second SCR downstream NOx mass flow integral during the process of decreasing from the third set ammonia storage to the fourth set ammonia storage in the stop injection stage are obtained; according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral, it is determined whether there is a low SCR conversion efficiency fault in the current SCR box. The present invention solves the problems that at present, affected by environmental, working condition, and control factors, the SCR conversion efficiency diagnosis method has poor robustness and a high risk of false alarms, and realizes more accurate SCR conversion efficiency and improves the diagnosis accuracy of the SCR conversion efficiency.

[0038] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Brief Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0040] Figure 1 It is a flowchart of a method for diagnosing a low SCR conversion efficiency fault provided in Embodiment 1 of the present invention;

[0041] Figure 2It is a flowchart of a method for diagnosing the low SCR conversion efficiency fault according to Embodiment 2 of the present invention;

[0042] Figure 3 It is a schematic structural diagram of a device for diagnosing the low SCR conversion efficiency fault according to Embodiment 3 of the present invention;

[0043] Figure 4 It is a schematic structural diagram of a vehicle for implementing the method for diagnosing the low SCR conversion efficiency fault of the embodiments of the present invention. Detailed implementation manners

[0044] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0046] Embodiment 1

[0047] Figure 1 A flowchart of a method for diagnosing the low SCR conversion efficiency fault is provided for Embodiment 1 of the present invention. This embodiment is applicable to the situation of diagnosing the low SCR conversion efficiency fault of the SCR box. The method for diagnosing the low SCR conversion efficiency fault can be executed by a device for diagnosing the low SCR conversion efficiency fault. The device for diagnosing the low SCR conversion efficiency fault can be implemented in the form of hardware and / or software, and the device for diagnosing the low SCR conversion efficiency fault can be configured in the electronic control unit ECU of a vehicle with an SCR after-treatment system. As Figure 1 shown, the method for diagnosing the low SCR conversion efficiency fault includes:

[0048] S110. When the engine is running normally, the SCR passive diagnosis conversion efficiency is obtained through the passive diagnosis of the SCR conversion efficiency, and the active diagnosis of the SCR conversion efficiency is triggered according to the SCR passive diagnosis conversion efficiency.

[0049] Among them, the engine can be but is not limited to a conventional original emission engine or a high-altitude emission engine, and this embodiment does not impose any restrictions on this.

[0050] The passive diagnosis of the SCR conversion efficiency is to diagnose the SCR conversion efficiency without actively controlling the engine and the after-treatment status, and only passively collect the NOx signals upstream and downstream of the SCR for diagnosis.

[0051] Specifically, after the passive diagnosis of the SCR conversion efficiency meets the passive diagnosis release condition, the NOx mass flow rates upstream and downstream of the SCR are integrated, and the SCR passive diagnosis conversion efficiency is obtained after the integration window is satisfied; it can be understood that if the passive diagnosis of the SCR conversion efficiency does not meet the passive diagnosis release condition, the passive diagnosis of the SCR conversion efficiency continues to be detected until the passive diagnosis of the SCR conversion efficiency meets the passive diagnosis release condition and then subsequent operations are performed.

[0052] The passive diagnosis release condition is determined according to parameters such as the SCR box inlet temperature and the upstream NOx mass flow rate. In this embodiment, if parameters such as the SCR box inlet temperature and the upstream NOx mass flow rate are within the set threshold range, the passive diagnosis of the SCR conversion efficiency meets the passive diagnosis release condition.

[0053] Further, on this basis, when the SCR passive diagnosis conversion efficiency is lower than the passive diagnosis conversion efficiency limit value and the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the active diagnosis of the SCR conversion efficiency is triggered. That is, when the SCR passive diagnosis conversion efficiency is low, the active diagnosis of the SCR conversion efficiency is triggered at this time to further confirm the actual SCR conversion efficiency of the SCR box.

[0054] Among them, the passive diagnosis conversion efficiency limit value can be selected and set by those skilled in the art according to the actual situation, and this embodiment does not impose any restrictions on this. The passive diagnosis conversion efficiency limit value is used as a condition for triggering the active diagnosis of the SCR conversion efficiency.

[0055] The active diagnosis of the SCR conversion efficiency is to actively control the engine and the after-treatment status to diagnose the SCR conversion efficiency, that is, actively adjust the urea injection instead of performing it with a fixed urea injection.

[0056] The active diagnosis release condition is also determined according to parameters such as the SCR box inlet temperature and the upstream NOx mass flow rate. In this embodiment, if parameters such as the SCR box inlet temperature and the upstream NOx mass flow rate are within the set threshold range, the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition.

[0057] It can be understood that the set threshold ranges of the parameters involved in the passive diagnosis release condition and the active diagnosis release condition are different, and the specific situation can be set according to actual engine conditions or performance and other parameters. This embodiment does not impose any restrictions on this.

[0058] Based on the above embodiment, before triggering the active diagnosis of SCR conversion efficiency, control the active diagnosis of SCR conversion efficiency to be in the initial waiting stage, that is, the active diagnosis of SCR conversion efficiency is always in the waiting trigger stage. When the passive diagnosis of SCR conversion efficiency is triggered, the active diagnosis of SCR conversion efficiency waits to be triggered at any time. The initial waiting stage is the stage where the active diagnosis of SCR conversion efficiency waits to be triggered.

[0059] S120. After the active diagnosis of SCR conversion efficiency meets the active diagnosis release condition, control the urea injection system to enter the reduced injection stage, obtain the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage, and control the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage.

[0060] Specifically, after the active diagnosis of SCR conversion efficiency meets the active diagnosis release condition, at this time, it is in the active diagnosis of SCR conversion efficiency, that is, by using the ammonia storage difference and ammonia leakage difference characteristics between the normal SCR box and the SCR box with low SCR conversion efficiency, the SCR conversion efficiency is actively diagnosed. Specifically, control the urea injection system to enter the reduced injection stage. This reduced injection stage is to reduce the urea injection by a fixed percentage on the basis of the original controlled injection amount, so as to reduce the influence of ammonia leakage on the SCR conversion efficiency and prepare for the over-injection stage.

[0061] Among them, the real-time SCR conversion efficiency refers to the SCR conversion efficiency of the SCR box obtained in real time after the urea injection system enters the reduced injection stage during the active diagnosis stage of SCR conversion efficiency.

[0062] On the above basis, the initial ammonia storage is the ammonia storage when the urea injection system enters the reduced injection stage, and the first set ammonia storage is the critical ammonia storage when the urea injection system switches from the reduced injection stage to the over-injection stage. The first set ammonia storage can be set by those skilled in the art according to actual SCR temperature, engine conditions or performance and other parameters. This embodiment does not impose any restrictions on this.

[0063] Further, control the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage. Specifically: when the initial ammonia storage gradually decreases to the first set ammonia storage and the real-time SCR conversion efficiency is lower than the set SCR conversion efficiency threshold, control the urea injection system to enter the over-injection stage.

[0064] It is understandable that the SCR conversion efficiency threshold can be set by those skilled in the art according to actual engine operating conditions or performance parameters, etc., and this embodiment does not impose any restrictions on this.

[0065] S130. Record the second set ammonia storage and the third set ammonia storage when the urea injection system is in the overspray stage, and control the urea injection system to enter the stop-spray stage according to the second set ammonia storage and the third set ammonia storage.

[0066] Specifically, after triggering the urea injection system to enter the overspray stage, the urea in this overspray stage is additionally sprayed at a fixed percentage on the basis of the original controlled injection amount to quickly supplement the ammonia storage, that is, it gradually increases from the first set ammonia storage.

[0067] The second set ammonia storage refers to the SCR conversion efficiency calculation critical value when the urea injection system is in the overspray stage, that is, after gradually increasing the second set ammonia storage from the first set ammonia storage when the urea injection system is in the overspray stage, obtain the SCR upstream and downstream NOx mass flow integrals that satisfy the active diagnosis release conditions for the SCR conversion efficiency active diagnosis. The second set ammonia storage can be set by those skilled in the art according to actual SCR temperature, engine operating conditions or performance parameters, etc., and this embodiment does not impose any restrictions on this.

[0068] On the above basis, when the urea injection system is in the overspray stage, gradually increase the third set ammonia storage from the first set ammonia storage, and the urea injection system is converted from the overspray stage to the stop-spray stage. Specifically, controlling the urea injection system to enter the stop-spray stage according to the second set ammonia storage and the third set ammonia storage is specifically: when the second set ammonia storage gradually increases to the third set ammonia storage, control the urea injection system to enter the stop-spray stage.

[0069] It is understandable that the third set ammonia storage is the critical ammonia storage for the urea injection system to be converted from the overspray stage to the stop-spray stage. At the same time, the third set ammonia storage is the maximum ammonia storage of a normal SCR box. When the ammonia storage in the SCR box is greater than the third set ammonia storage, it may cause an ammonia leakage fault in the SCR box. The third set ammonia storage can be set by those skilled in the art according to actual SCR temperature, engine operating conditions or performance parameters, etc., and this embodiment does not impose any restrictions on this.

[0070] In addition, it should be noted that when the urea injection system is in the underspray stage, the overspray stage or the stop-spray stage, the diagnosis of the SCR conversion efficiency is in the SCR conversion efficiency active diagnosis.

[0071] S140. Obtain the fourth set ammonia storage at the end of the urea injection system's injection stop stage, and obtain the integral of the NOx mass flow rate upstream of the first SCR and the integral of the NOx mass flow rate downstream of the first SCR during the process of the over-injection stage increasing from the second set ammonia storage to the third set ammonia storage, as well as the integral of the NOx mass flow rate upstream of the second SCR and the integral of the NOx mass flow rate downstream of the second SCR during the process of the injection stop stage decreasing from the third set ammonia storage to the fourth set ammonia storage.

[0072] It is known that obtaining the fourth set ammonia storage at the end of the urea injection system's injection stop stage specifically means: when the urea injection system is in the injection stop stage, reducing the third set ammonia storage until the end of the injection stop stage to obtain the fourth set ammonia storage.

[0073] The fourth set ammonia storage refers to the critical value at the end of the urea injection system's injection stop stage. The fourth set ammonia storage can be set by those skilled in the art according to parameters such as the actual SCR temperature, engine working conditions, or performance. This embodiment does not impose any restrictions on this.

[0074] Specifically, after triggering the urea injection system to enter the injection stop stage, obtain the integral of the NOx mass flow rate upstream and downstream of the SCR during the process of the over-injection stage of the urea injection system increasing from the second set ammonia storage to the third set ammonia storage, which are respectively the integral of the NOx mass flow rate upstream of the first SCR, m ov_us and the integral of the NOx mass flow rate downstream of the first SCR, m ov_ds ; when the urea injection system is in the injection stop stage, control the stop of urea injection. As the third set ammonia storage gradually consumes and decreases to the fourth set ammonia storage, the injection stop stage of the urea injection system ends. Then, for the integral of the NOx mass flow rate upstream and downstream of the SCR during the process of the urea injection system in the injection stop stage decreasing from the third set ammonia storage to the fourth set ammonia storage, they are respectively the integral of the NOx mass flow rate upstream of the second SCR, m st_us and the integral of the NOx mass flow rate downstream of the second SCR, m st_ds .

[0075] The integral of the NOx mass flow rate upstream of the first SCR, m ov_us and the integral of the NOx mass flow rate downstream of the first SCR, m ov_ds , as well as the integral of the NOx mass flow rate upstream of the second SCR, m st_us and the integral of the NOx mass flow rate downstream of the second SCR, m st_ds are all obtained by respectively collecting the upstream and downstream NOx concentrations using existing upstream and downstream NOx sensors and then obtaining the upstream and downstream NOx mass flow rates according to existing calculation methods and further integrating them.

[0076] S150. Determine whether there is a fault of low SCR conversion efficiency in the current SCR box according to the NOx mass flow integral upstream of the first SCR, the NOx mass flow integral downstream of the first SCR, the NOx mass flow integral upstream of the second SCR, and the NOx mass flow integral downstream of the second SCR.

[0077] Specifically, determining whether there is a fault of low SCR conversion efficiency in the current SCR box according to the NOx mass flow integral upstream of the first SCR, the NOx mass flow integral downstream of the first SCR, the NOx mass flow integral upstream of the second SCR, and the NOx mass flow integral downstream of the second SCR is specifically as follows: Determine the target SCR conversion efficiency of the current SCR box according to the NOx mass flow integral upstream of the first SCR, the NOx mass flow integral downstream of the first SCR, the NOx mass flow integral upstream of the second SCR, and the NOx mass flow integral downstream of the second SCR; if the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value, it is determined that there is a fault of low SCR conversion efficiency in the current SCR box; if the target SCR conversion efficiency is not lower than the active diagnosis conversion efficiency limit value, it is determined that the SCR conversion efficiency of the current SCR box is normal.

[0078] Among them, the target SCR conversion efficiency is used to judge whether the SCR conversion efficiency of the current SCR box is normal, and the target SCR conversion efficiency is obtained when the diagnosis of the SCR conversion efficiency is in the active diagnosis of the SCR conversion efficiency.

[0079] In this embodiment, based on the above, the specific calculation method of the target SCR conversion efficiency of the current SCR box is as follows:

[0080]

[0081] The active diagnosis conversion efficiency limit value can be selected and set by those skilled in the art according to the actual situation, and this embodiment does not make any restrictions on this. The active diagnosis conversion efficiency limit value is used as a condition for diagnosing whether there is a fault of low SCR conversion efficiency in the SCR box.

[0082] In the technical solution of the embodiment of the present invention, when the engine is running normally, the SCR passive diagnosis conversion efficiency is obtained through the passive diagnosis of the SCR conversion efficiency, and the active diagnosis of the SCR conversion efficiency is triggered according to the SCR passive diagnosis conversion efficiency; after the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the urea injection system is controlled to enter the reduced injection stage, the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage are obtained, and the urea injection system is controlled to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage; the second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage are recorded, and the urea injection system is controlled to enter the stop injection stage according to the second set ammonia storage and the third set ammonia storage; the fourth set ammonia storage at the end of the stop injection stage of the urea injection system is obtained, and the first SCR upstream NOx mass flow integral and the first SCR downstream NOx mass flow integral during the process of increasing the ammonia storage from the second set ammonia storage to the third set ammonia storage in the over-injection stage, and the second SCR upstream NOx mass flow integral and the second SCR downstream NOx mass flow integral during the process of reducing the ammonia storage from the third set ammonia storage to the fourth set ammonia storage in the stop injection stage are obtained; according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral, it is determined whether there is a low SCR conversion efficiency fault in the current SCR box. The present invention solves the problems that currently, affected by environmental, working condition, and control factors, the SCR conversion efficiency diagnosis method has poor robustness and a high risk of false alarms, and realizes a more accurate SCR conversion efficiency and improves the diagnosis accuracy of the SCR conversion efficiency.

[0083] Embodiment 2

[0084] Figure 2 The flowchart of a method for diagnosing a low SCR conversion efficiency fault provided by Embodiment 2 of the present invention. On the basis of the above embodiment, a feasible implementation manner is provided. As Figure 2 shown, the method for diagnosing a low SCR conversion efficiency fault includes:

[0085] S210. The engine is running normally.

[0086] S211. Determine whether the passive diagnosis of the SCR conversion efficiency meets the passive diagnosis release condition. If so, execute step S212; if not, execute step S211.

[0087] S212. Obtain the SCR passive diagnosis conversion efficiency through the passive diagnosis of the SCR conversion efficiency, and execute step S213.

[0088] S213. Determine whether the SCR passive diagnosis conversion efficiency is lower than the passive diagnosis conversion efficiency limit value. If so, execute step S214; if not, execute step S211.

[0089] S214. Control the SCR conversion efficiency active diagnosis to be in the initial waiting stage, and execute step S215.

[0090] S215. Determine whether the SCR conversion efficiency active diagnosis meets the active diagnosis release condition. If so, execute step S216; if not, execute step S214.

[0091] S216. Control the urea injection system to enter the reduced injection stage, and obtain the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage.

[0092] S217. Determine whether the initial ammonia storage is reduced to the first set ammonia storage and the real-time SCR conversion efficiency is lower than the set SCR conversion efficiency threshold. If so, execute step S218; if not, execute step S216.

[0093] S218. Control the urea injection system to enter the over-injection stage.

[0094] S219. Record the second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage.

[0095] S220. Determine whether the second set ammonia storage increases to the third set ammonia storage. If so, execute step S221; if not, execute step S218.

[0096] S221. Control the urea injection system to enter the stop injection stage.

[0097] S222. Determine whether the third set ammonia storage is reduced to the fourth set ammonia storage. If so, execute step S223; if not, execute step S221.

[0098] S223. Determine the target SCR conversion efficiency of the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral.

[0099] S224. Determine whether the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value. If so, execute step S225; if not, execute step S226.

[0100] S225. Determine that there is a low SCR conversion efficiency fault in the current SCR box.

[0101] S226. Determine that the SCR conversion efficiency of the current SCR box is normal.

[0102] The present invention uses a method of triggering active diagnosis of SCR conversion efficiency after the passive diagnosis efficiency of SCR conversion efficiency is low, further confirms the SCR conversion efficiency through active diagnosis, and introduces an active diagnosis method for SCR conversion efficiency by utilizing the ammonia storage difference and ammonia leakage difference characteristics between a normal SCR box and an SCR box with low efficiency. The SCR conversion efficiency is diagnosed by means such as reducing urea injection, over-injecting urea, and stopping urea injection, and the average SCR conversion efficiency in the over-injection stage and the stop-injection stage is calculated to further confirm the actual conversion efficiency of the SCR.

[0103] In particular, in the over-injection stage, when the normal SCR box reaches the maximum ammonia storage boundary of the model, the SCR conversion efficiency is high, the ammonia leakage is small, and the SCR conversion efficiency of the SCR box with low efficiency is lower, the ammonia leakage is larger, and the actual ammonia storage is lower than that of the normal SCR box at the same maximum ammonia storage boundary of the model. Moreover, the NOx sensor is cross-sensitive to NH3, and there is an obvious efficiency difference between the SCR box with low efficiency and the normal SCR box; in the stop-injection stage, due to the low actual ammonia storage of the SCR box with low efficiency, when it is reduced to the same ammonia storage boundary of the model, the actual ammonia storage of the SCR box with low efficiency drops faster and the efficiency is lower, and there is also an obvious distinction in SCR conversion efficiency.

[0104] Embodiment III

[0105] Figure 3 The following is a schematic structural diagram of a device for diagnosing low SCR conversion efficiency provided in Embodiment III of the present invention. As Figure 3 shown, the device for diagnosing low SCR conversion efficiency includes:

[0106] An active diagnosis trigger module 310, configured to execute when the engine is running normally, obtain the SCR passive diagnosis conversion efficiency through passive diagnosis of the SCR conversion efficiency, and trigger the active diagnosis of the SCR conversion efficiency according to the SCR passive diagnosis conversion efficiency;

[0107] An over-injection stage entry module 320, configured to execute after the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, control the urea injection system to enter the reduced injection stage, obtain the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage, and control the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage;

[0108] A stop-injection stage entry module 330, configured to execute record the second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage, and control the urea injection system to enter the stop-injection stage according to the second set ammonia storage and the third set ammonia storage;

[0109] The NOx mass flow integral acquisition module 340 is configured to execute the acquisition of the fourth set ammonia storage at the end of the injection stop stage of the urea injection system, and acquire the upstream NOx mass flow integral of the first SCR and the downstream NOx mass flow integral of the first SCR during the process of the over-injection stage increasing from the second set ammonia storage to the third set ammonia storage, as well as the upstream NOx mass flow integral of the second SCR and the downstream NOx mass flow integral of the second SCR during the process of the injection stop stage decreasing from the third set ammonia storage to the fourth set ammonia storage;

[0110] The fault judgment module 350 is configured to execute the determination of whether there is a low SCR conversion efficiency fault in the current SCR box according to the upstream NOx mass flow integral of the first SCR, the downstream NOx mass flow integral of the first SCR, the upstream NOx mass flow integral of the second SCR, and the downstream NOx mass flow integral of the second SCR.

[0111] Optionally, the SCR passive diagnosis conversion efficiency is obtained through SCR conversion efficiency passive diagnosis, and the SCR conversion efficiency active diagnosis is triggered according to the SCR passive diagnosis conversion efficiency, specifically for:

[0112] After the SCR conversion efficiency passive diagnosis meets the passive diagnosis release condition, the SCR passive diagnosis conversion efficiency is calculated;

[0113] When the SCR passive diagnosis conversion efficiency is lower than the passive diagnosis conversion efficiency limit value and the SCR conversion efficiency active diagnosis meets the active diagnosis release condition, the SCR conversion efficiency active diagnosis is triggered.

[0114] Optionally, the SCR conversion efficiency low fault diagnosis device further includes:

[0115] The waiting stage module is configured to execute the control of the SCR conversion efficiency active diagnosis in the initial waiting stage.

[0116] Optionally, the control of the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage is specifically for:

[0117] When the initial ammonia storage is reduced to the first set ammonia storage and the real-time SCR conversion efficiency is lower than the set SCR conversion efficiency threshold, the urea injection system is controlled to enter the over-injection stage.

[0118] Optionally, the control of the urea injection system to enter the injection stop stage according to the second set ammonia storage and the third set ammonia storage is specifically for:

[0119] When the ammonia storage in the second setting increases to the ammonia storage in the third setting, control the urea injection system to enter the stop injection stage.

[0120] Optionally, obtaining the fourth set of ammonia storage at the end of the stop injection stage of the urea injection system includes:

[0121] When the urea injection system is in the stop injection stage, reduce the ammonia storage in the third setting to the end of the stop injection stage to obtain the fourth set of ammonia storage.

[0122] Optionally, the fault judgment module 350 is specifically configured to:

[0123] Determine the target SCR conversion efficiency of the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral;

[0124] If the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value, it is determined that the current SCR box has a low SCR conversion efficiency fault;

[0125] If the target SCR conversion efficiency is not lower than the active diagnosis conversion efficiency limit value, it is determined that the SCR conversion efficiency of the current SCR box is normal.

[0126] The SCR conversion efficiency low fault diagnosis device provided by the embodiments of the present invention can execute the SCR conversion efficiency low fault diagnosis method provided by any embodiment of the present invention, and has the corresponding functional modules and beneficial effects for executing the SCR conversion efficiency low fault diagnosis method.

[0127] Embodiment 4

[0128] Figure 4 FIG. shows a schematic structural diagram of a vehicle 410 that can be used to implement the embodiments of the present invention. The vehicle is intended to include various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The vehicle may also include various forms of mobile devices, such as personal digital processors, cellular phones, smart phones, wearable devices (such as helmets, glasses, watches, etc.) and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0129] As Figure 4As shown, vehicle 410 includes at least one processor 411 and a memory communicatively connected to the at least one processor 411, such as read-only memory (ROM) 412, random access memory (RAM) 413, etc. The memory stores a computer program executable by the at least one processor. The processor 411 can perform various appropriate actions and processes according to the computer program stored in the read-only memory (ROM) 412 or the computer program loaded from the storage unit 418 into the random access memory (RAM) 413. In the RAM 413, various programs and data required for the operation of the vehicle 410 can also be stored. The processor 411, ROM 412, and RAM 413 are connected to each other via a bus 414. An input / output (I / O) interface 415 is also connected to the bus 414.

[0130] Multiple components in the vehicle 410 are connected to the I / O interface 415, including: an input unit 416, such as a keyboard, mouse, etc.; an output unit 417, such as various types of displays, speakers, etc.; a storage unit 418, such as a disk, optical disc, etc.; and a communication unit 419, such as a network card, modem, wireless communication transceiver, etc. The communication unit 419 allows the vehicle 410 to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks.

[0131] The processor 411 can be various general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the processor 411 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 411 executes the various methods and processes described above, such as the SCR conversion efficiency low fault diagnosis method.

[0132] In some embodiments, the SCR conversion efficiency low fault diagnosis method can be implemented as a computer program tangibly embodied in a computer-readable storage medium, such as the storage unit 418. In some embodiments, part or all of the computer program can be loaded and / or installed onto the vehicle 410 via the ROM 412 and / or the communication unit 419. When the computer program is loaded into the RAM 413 and executed by the processor 411, one or more steps of the SCR conversion efficiency low fault diagnosis method described above can be performed. Alternatively, in other embodiments, the processor 411 can be configured to execute the SCR conversion efficiency low fault diagnosis method by any other appropriate means (e.g., by means of firmware).

[0133] The various embodiments of the systems and techniques described above in this document can be implemented in digital electronic circuitry, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on a chip (SOCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments can include: being implemented in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be a special-purpose or general-purpose programmable processor that receives data and instructions from a storage system, at least one input device, and at least one output device, and transmits the data and instructions to the storage system, the at least one input device, and the at least one output device.

[0134] The computer programs for implementing the methods of the present invention can be written in any combination of one or more programming languages. These computer programs can be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus, such that the computer programs, when executed by the processor, cause the functions / operations specified in the flowchart and / or block diagram to be implemented. The computer programs can be executed entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine, or entirely on the remote machine or server.

[0135] In the context of the present invention, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, the computer-readable storage medium can be a machine-readable signal medium. More specific examples of the machine-readable storage medium would include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0136] To provide interaction with a user, the systems and techniques described herein can be implemented on a vehicle having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the vehicle. Other kinds of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0137] The systems and techniques described herein can be implemented in a computing system including backend components (e.g., as a data server), or a computing system including middleware components (e.g., an application server), or a computing system including frontend components (e.g., a user computer having a graphical user interface or a web browser through which the user can interact with an implementation of the systems and techniques described herein), or a computing system including any combination of such backend components, middleware components, or frontend components. The components of the system can be interconnected by digital data communication in any form or medium (e.g., a communication network). Examples of communication networks include: local area network (LAN), wide area network (WAN), blockchain network, and the Internet.

[0138] A computing system can include a client and a server. The client and the server are generally remote from each other and typically interact through a communication network. The relationship between the client and the server is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or a cloud host, which is a host product in the cloud computing service system and solves the defects of difficult management and weak business scalability existing in traditional physical hosts and VPS services.

[0139] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps recited in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is imposed herein.

[0140] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fault diagnosis method for low SCR conversion efficiency, characterized in that Including: When the engine is operating normally, the SCR passive diagnosis conversion efficiency is obtained through the passive diagnosis of the SCR conversion efficiency, and the active diagnosis of the SCR conversion efficiency is triggered according to the SCR passive diagnosis conversion efficiency; After the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the urea injection system is controlled to enter the reduced injection stage, the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage are obtained, and the urea injection system is controlled to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage; The second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage are recorded, and the urea injection system is controlled to enter the stop injection stage according to the second set ammonia storage and the third set ammonia storage; The fourth set ammonia storage at the end of the stop injection stage of the urea injection system is obtained, and the first SCR upstream NOx mass flow integral and the first SCR downstream NOx mass flow integral during the process of the over-injection stage increasing from the second set ammonia storage to the third set ammonia storage, and the second SCR upstream NOx mass flow integral and the second SCR downstream NOx mass flow integral during the process of the stop injection stage decreasing from the third set ammonia storage to the fourth set ammonia storage are obtained; According to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral, it is determined whether there is a low SCR conversion efficiency fault in the current SCR box; Among them, determining whether there is a low SCR conversion efficiency fault in the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral includes: determining the target SCR conversion efficiency of the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral; if the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value, it is determined that there is a low SCR conversion efficiency fault in the current SCR box; if the target SCR conversion efficiency is not lower than the active diagnosis conversion efficiency limit value, it is determined that the SCR conversion efficiency of the current SCR box is normal.

2. The SCR conversion efficiency low fault diagnosis method according to claim 1, characterized in that The obtaining the SCR passive diagnosis conversion efficiency through the passive diagnosis of the SCR conversion efficiency and triggering the active diagnosis of the SCR conversion efficiency according to the SCR passive diagnosis conversion efficiency includes: After the passive diagnosis of the SCR conversion efficiency meets the passive diagnosis release condition, the SCR passive diagnosis conversion efficiency is calculated; When the SCR passive diagnosis conversion efficiency is lower than the passive diagnosis conversion efficiency limit value and the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, the active diagnosis of the SCR conversion efficiency is triggered.

3. The SCR conversion efficiency low fault diagnosis method according to claim 2, characterized in that, Before triggering the active diagnosis of the SCR conversion efficiency, it also includes: Controlling the active diagnosis of the SCR conversion efficiency to be in the initial waiting stage.

4. The SCR conversion efficiency low fault diagnosis method according to claim 1, characterized in that, The step of controlling the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage includes: When the initial ammonia storage is reduced to the first set ammonia storage and the real-time SCR conversion efficiency is lower than the set SCR conversion efficiency threshold, controlling the urea injection system to enter the over-injection stage.

5. The method for diagnosing the fault of low SCR conversion efficiency according to claim 1, characterized in that, The step of controlling the urea injection system to enter the stop-injection stage according to the second set ammonia storage and the third set ammonia storage includes: When the second set ammonia storage increases to the third set ammonia storage, controlling the urea injection system to enter the stop-injection stage.

6. The SCR conversion efficiency low fault diagnosis method according to claim 1, characterized in that Obtaining the fourth set ammonia storage at the end of the stop-injection stage of the urea injection system includes: When the urea injection system is in the stop-injection stage, reducing the third set ammonia storage to the end of the stop-injection stage to obtain the fourth set ammonia storage.

7. An SCR conversion efficiency low fault diagnosis device, applying the SCR conversion efficiency low fault diagnosis method according to any one of claims 1-6, characterized in that, It includes: An active diagnosis trigger module, which is used to, when the engine is running normally, obtain the SCR passive diagnosis conversion efficiency through the passive diagnosis of the SCR conversion efficiency, and trigger the active diagnosis of the SCR conversion efficiency according to the SCR passive diagnosis conversion efficiency; An over-injection stage entry module, which is used to, after the active diagnosis of the SCR conversion efficiency meets the active diagnosis release condition, control the urea injection system to enter the reduced-injection stage, obtain the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage, and control the urea injection system to enter the over-injection stage according to the real-time SCR conversion efficiency, the initial ammonia storage, and the first set ammonia storage; A stop-injection stage entry module, which is used to record the second set ammonia storage and the third set ammonia storage when the urea injection system is in the over-injection stage, and control the urea injection system to enter the stop-injection stage according to the second set ammonia storage and the third set ammonia storage; A NOx mass flow integral acquisition module, which is used to obtain the fourth set ammonia storage at the end of the stop-injection stage of the urea injection system, and obtain the first SCR upstream NOx mass flow integral and the first SCR downstream NOx mass flow integral during the process of the second set ammonia storage increasing to the third set ammonia storage in the over-injection stage, and the second SCR upstream NOx mass flow integral and the second SCR downstream NOx mass flow integral during the process of the third set ammonia storage decreasing to the fourth set ammonia storage in the stop-injection stage; A fault judgment module, which is used to determine whether there is a low SCR conversion efficiency fault in the current SCR box according to the first SCR upstream NOx mass flow integral, the first SCR downstream NOx mass flow integral, the second SCR upstream NOx mass flow integral, and the second SCR downstream NOx mass flow integral; Among them, the fault judgment module is specifically used for: determining the target SCR conversion efficiency of the current SCR box according to the NOx mass flow integral upstream of the first SCR, the NOx mass flow integral downstream of the first SCR, the NOx mass flow integral upstream of the second SCR, and the NOx mass flow integral downstream of the second SCR; if the target SCR conversion efficiency is lower than the active diagnosis conversion efficiency limit value, determining that there is a low SCR conversion efficiency fault in the current SCR box; if the target SCR conversion efficiency is not lower than the active diagnosis conversion efficiency limit value, determining that the SCR conversion efficiency of the current SCR box is normal.

8. A vehicle, characterized in that, The vehicle includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the low SCR conversion efficiency fault diagnosis method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a processor to implement the low SCR conversion efficiency fault diagnosis method according to any one of claims 1-6 when executed.

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