A method for vehicle catalytic converter failure diagnosis and failure cause analysis

Abstract

The present invention discloses a method for diagnosing and analyzing the cause of failure of an automotive catalyst, belonging to the technical field of automotive exhaust catalysts. The method comprises the following steps: fault confirmation and judgment; assembly airtightness testing; carrier oxygen storage capacity testing under vehicle-wide operating conditions; carrier oxygen storage capacity testing under engine bench operating conditions; and carrier failure analysis testing, including carrier bonding strength testing, carrier specific surface area testing, and carrier element analysis. The method refines catalyst fault diagnosis and analysis from the aspects of fault diagnosis, oxygen storage testing, and carrier analysis. It determines catalyst failure based on fault codes and oxygen storage test results, and accurately determines the cause of failure through multiple experimental tests and analyses of the carrier. This method achieves precise filtering of false alarms, saves the cost of replacing parts, and significantly shortens the time it takes to find the cause of failure. Furthermore, the responsibilities of the vehicle manufacturer, parts manufacturer, and user can be clarified based on the cause of failure.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile exhaust catalytic converters, and in particular relates to a method for diagnosing vehicle failure and analyzing failure causes of automobile catalytic converters. Background Art

[0002] The automotive three-way catalytic converter is the most important off-board purification device installed in the vehicle's exhaust system. It can convert harmful gases such as CO, HC and NOx emitted from the vehicle's exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction. However, the working environment of the catalyst is harsh, and it continuously experiences high-temperature chemical reactions. Coupled with the poor quality of oil, the catalyst often fails, causing the vehicle's fault light to alarm, which in turn affects emissions and driving performance. At the same time, the cost of catalyst parts is high. If it is impossible to determine whether the catalyst has failed and the reason for the failure, replacing the catalyst will cause huge losses to the car manufacturer and the user. Therefore, how to quickly and accurately determine whether the catalyst has failed and the reason for the failure has become an important and difficult task in the automotive industry.

[0003] The prior art discloses a method for diagnosing vehicle failure and analyzing the cause of failure of an automobile catalyst, including: fault code reading; assembly air tightness test; vehicle operating oxygen storage capacity test; bench operating oxygen storage capacity test; and carrier failure analysis test.

[0004] Currently, most catalytic converter failures are due to false alarms caused by sensors or ECUs. Existing technical troubleshooting requires destructive analysis of the parts, making them unusable. Summary of the Invention

[0005] In response to the problem in the prior art that destructive analysis of parts is required, resulting in the inability to continue using parts that have given false alarms, the present invention provides a method for vehicle-wide failure diagnosis and failure cause analysis of automotive catalysts. The method refines catalyst fault diagnosis and analysis from aspects such as fault diagnosis, oxygen storage detection, and carrier analysis. It determines whether the catalyst has failed based on fault codes and oxygen storage test results, and accurately determines the cause of failure through multiple experimental detection and analysis of the carrier, thereby achieving accurate filtering of false alarm problems, saving the cost of replacing parts, and significantly shortening the time required to find the cause of failure. The responsibilities of vehicle manufacturers, parts manufacturers, and users can be further clarified through the cause of failure.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for diagnosing vehicle failure and analyzing the cause of failure of an automobile catalyst comprises the following steps:

[0008] S1: Fault confirmation:

[0009] Read the fault code of the ECU of the faulty vehicle to determine whether it is a catalyst failure fault code;

[0010] S2: Assembly air tightness test:

[0011] Place the faulty catalyst in a parts airtightness tester and measure its airtightness. If the leakage exceeds the standard, find the leak point and weld it until the leakage meets the requirement. Then, confirm the fault in the vehicle. If the fault code is not eliminated, proceed to the next step.

[0012] S3: Carrier oxygen storage capacity test under vehicle working conditions:

[0013] INCA software is used to read the carrier oxygen storage capacity at different vehicle speeds and compare it with the calibrated aged carrier oxygen storage capacity of the vehicle. If the measured oxygen storage capacity is less than 1.2 times the aged carrier oxygen storage capacity, the next step of bench test is carried out. If it is greater than 1.2 times the aged carrier oxygen storage capacity, the catalyst is considered to be fault-free and the alarm is false.

[0014] S4: Engine bench operating condition carrier oxygen storage test:

[0015] Install the assembly on the engine bench and measure the carrier oxygen storage capacity multiple times by controlling the air-fuel ratio. Then take the average value, which is the engine bench oxygen storage capacity of the carrier. If it is higher than 1.2 times the oxygen storage capacity of the aged carrier, it is considered that the catalyst is not faulty and the alarm is false.

[0016] S5: Carrier failure analysis test, including carrier bonding strength test, carrier specific surface area test, and carrier element analysis.

[0017] Furthermore, in step S2, an air leakage test is performed at a pressure of 30 kPa.

[0018] Furthermore, in step S2, the standard is that the leakage volume should not be greater than 0.5 L / min.

[0019] Furthermore, in step S3, the different vehicle speeds include 50 km / h, 70 km / h, 90 km / h, and 110 km / h, and the vehicle travels at a constant speed for 30 seconds.

[0020] Furthermore, step S4 specifically includes the following contents:

[0021] Install the assembly on the engine test bench and stabilize the engine operating conditions at an exhaust mass flow rate of 40kg / h and an exhaust temperature of 450℃. First, reduce the air-fuel ratio to 0.95. After waiting for the rear oxygen sensor voltage to stabilize for 40s, increase the air-fuel ratio to 1.05. After the rear oxygen voltage signal drops to a low voltage, read the oxygen storage value. After measuring the oxygen storage value multiple times, take the average value.

[0022] Furthermore, in step S5, the carrier bonding strength test specifically includes the following contents:

[0023] The carrier with abnormal oxygen storage test results, which is 1.2 times lower than the oxygen storage capacity of the aged carrier, is removed from the assembly. The catalyst carrier is first weighed, and then an air gun is used to blow back and forth for 30 seconds in an area 10 mm away with an air gun pressure of 4.0 bar. The carrier is weighed again. The weight difference before and after the test is compared, and the weight loss rate is calculated. If the bonding strength is greater than 2%, it is determined that the cause of the carrier failure is coating shedding.

[0024] Furthermore, in step S5, the carrier specific surface area test specifically includes the following contents:

[0025] The carrier with abnormal oxygen storage test results is cut along the middle axis, and a sample with a size of 1cm×1cm×1cm is taken from the center of the carrier and ground into powder. The specific surface area is determined by the amount of gas adsorbed under a given pressure. If the specific surface area is ≤ 70% of the specific surface area of ​​the fresh sample, it is judged that the coating has failed due to abnormally high temperature.

[0026] Furthermore, in step S5, the carrier element analysis specifically includes the following contents:

[0027] The faulty carrier is ground into powder, and the element types are measured by a spectrometer to determine whether there is chemical element poisoning.

[0028] Furthermore, the chemical elements include sulfur, phosphorus, calcium, manganese or lead.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] The present invention provides a method for diagnosing vehicle failure and analyzing the cause of failure of an automobile catalyst. The method directly tests the assembly, and can continue to use the parts after filtering out false alarms, thereby reducing losses. The method mainly refines the catalyst fault diagnosis and analysis from aspects such as fault diagnosis, oxygen storage detection, and carrier analysis. Whether the catalyst has failed is determined based on the fault code and oxygen storage test results, and the cause of failure is accurately determined through multiple experimental detection and analysis of the carrier, thereby achieving accurate filtering of false alarm problems, saving the cost of replacing parts, and significantly shortening the time for searching for the cause of failure. The responsibilities of the automobile company, parts manufacturer, and user can be further clarified through the cause of failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0032] Figure 1A schematic flow chart of a method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to the present invention;

[0033] Figure 2 This is a schematic diagram summarizing the reasons for the failure of the three-way catalytic converter;

[0034] Figure 3 A flowchart for troubleshooting carrier failure causes;

[0035] Figure 4 Schematic diagram of the oxygen storage principle of the catalyst carrier. DETAILED DESCRIPTION

[0036] In order to clearly and completely describe the technical solution and specific working process of the present invention, the specific implementation methods of the present invention are as follows in conjunction with the accompanying drawings:

[0037] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0038] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0039] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0040] Example 1

[0041] like Figure 1 FIG2 is a flow chart of a method for diagnosing vehicle failure and analyzing the cause of failure of an automobile catalyst according to an embodiment of the present invention. The method specifically includes the following steps:

[0042] S1: Fault confirmation:

[0043] Use INCA software to read the fault code of the faulty vehicle ECU to determine whether it is a catalyst failure fault code;

[0044] S2: Assembly air tightness test:

[0045] Place the faulty catalyst in a parts airtightness tester and measure the assembly's airtightness at 30kPa. The standard is a leakage rate of no more than 0.5L / min. If the leakage rate exceeds the standard, find the leak point and weld it until the leakage rate meets the standard. Then, confirm the fault in the vehicle. If the fault code is not cleared, proceed to the next step.

[0046] S3: Carrier oxygen storage capacity test under vehicle working conditions:

[0047] The vehicle was driven at a constant speed of 50 km / h, 70 km / h, 90 km / h, and 110 km / h for 30 seconds. The carrier oxygen storage capacity at different speeds was read using INCA software and compared with the calibrated oxygen storage capacity of the aged carrier. If the measured oxygen storage capacity was close to or lower than the aged carrier oxygen storage capacity (less than 1.2 times the aged carrier oxygen storage capacity), the test proceeded to the next bench test for catalyst failure and carrier section analysis. If the measured oxygen storage capacity was higher than 1.2 times the aged carrier oxygen storage capacity, the catalyst was deemed to be fault-free and the alarm was a false alarm.

[0048] S4: Engine bench operating condition carrier oxygen storage test:

[0049] Install the assembly on the engine bench and stabilize the engine operating conditions at an exhaust mass flow rate of 40kg / h and an exhaust temperature of 450°C. First, reduce the air-fuel ratio to 0.95. After waiting for the rear oxygen sensor voltage to stabilize for 40 seconds, increase the air-fuel ratio to 1.05. After the rear oxygen voltage signal drops to a low voltage, read the OSC (oxygen storage capacity) value. After multiple measurements, take the average value, which is the carrier's engine bench oxygen storage capacity value. If it is higher than 1.2 times the aged carrier oxygen storage capacity, it is considered that the catalyst is not faulty and the alarm is false.

[0050] S5: If Figure 3 As shown, carrier failure analysis test, including carrier bonding strength test, carrier specific surface area test, and carrier element analysis;

[0051] The carrier bonding strength test specifically includes the following contents:

[0052] The carrier with abnormal oxygen storage test results, which is 1.2 times lower than the oxygen storage capacity of the aged carrier, is removed from the assembly. The catalyst carrier is first weighed, and then an air gun is used to blow back and forth for 30 seconds in an area 10 mm away with an air gun pressure of 4.0 bar. The carrier is weighed again. The weight difference before and after the test is compared, and the weight loss rate is calculated. If the bonding strength is greater than 2%, it is determined that the cause of the carrier failure is coating shedding.

[0053] The carrier specific surface area test specifically includes the following contents:

[0054] The carrier with abnormal oxygen storage test results is cut along the middle axis, and a sample with a size of 1cm×1cm×1cm is taken from the center of the carrier and ground into powder. The specific surface area is determined by the amount of gas adsorbed under a given pressure. If the specific surface area is ≤ 70% of the specific surface area of ​​the fresh sample, it is judged that the coating has failed due to abnormally high temperature.

[0055] The carrier element analysis specifically includes the following contents:

[0056] The faulty carrier is ground into powder and the types of elements are measured by a spectrometer to determine whether there is poisoning by elements such as manganese, lead, and phosphorus.

[0057] Example 2

[0058] This embodiment provides a method for diagnosing vehicle failure and analyzing the cause of failure of an automotive catalyst, including: reading fault codes; testing assembly air tightness; testing the oxygen storage capacity of the carrier under vehicle operating conditions; testing the oxygen storage capacity of the carrier under engine bench operating conditions; and performing a carrier failure analysis test. The specific steps are as follows:

[0059] Step 1: Read the fault code;

[0060] The fault code for catalyst aging in the faulty vehicle is P042000. The alarm principle is that the ECU detects that the oxygen storage capacity of the pre-stage catalyst is too low (low to the OBD alarm threshold). The OBD alarm threshold is 20mg. The possible reasons are:

[0061] ① Catalyst assembly failure signal, open welding, cracking causing leakage, resulting in inaccurate oxygen sensor detection;

[0062] ②Three-way catalyst carrier failure

[0063] Step 2: Assembly air tightness test;

[0064] 100% of the 10 faulty assembly parts were inspected for air tightness and all met the requirements.

[0065] Step 3: Carrier oxygen storage capacity test under vehicle and engine operating conditions;

[0066] 4 pieces are higher than the aged pieces, and 6 pieces are lower than the aged pieces; the oxygen storage capacity of the aged pieces is 400 mg, and the specific values ​​are shown in Table 1;

[0067] Table 1 is the oxygen storage table

[0068] 1# 2# 3# 4# 5# 6# 7# 8# 9# 10# Oxygen storage capacity / mg 526 420 68 610 23 55 44 138 499 148

[0069] Step 4: Carrier failure analysis test;

[0070] Six front-stage catalyst carriers with oxygen storage capacity below that of the aged catalyst were taken out, and the results of the appearance inspection are shown in Table 2:

[0071] Table 2 is the appearance table

[0072] serial number 3# 5# 6# 7# 8# 10# Appearance normal normal normal normal normal Burning

[0073] The bonding strength of 6 carriers was tested, and except for 10#, the bonding strength of all carriers was less than 2%.

[0074] The specific surface areas of these six carriers were measured after sectioning, and fresh carriers were randomly sampled and measured for comparison. The specific surface areas of the six carriers were significantly lower than those of the fresh carriers. The specific results are shown in Table 3:

[0075] Table 3 is the specific surface area table

[0076]

[0077] Step 5: Carrier failure analysis test;

[0078] Catalysts 1#, 2#, 4#, and 9# were qualified; catalyst 10# experienced abnormally high-temperature melting; the oxygen storage capacity and specific surface area of ​​the carriers of catalysts 3#, 5#, 6#, 7#, and 8# were too low, indicating that the performance of the carriers themselves (anti-aging ability) had failed.

[0079] The diagnostic and analysis method of this embodiment refines the diagnosis and analysis of catalyst faults from the aspects of fault diagnosis, oxygen storage detection, and carrier analysis. It determines whether the catalyst has failed based on the fault code and oxygen storage test results, and accurately determines the cause of failure through multiple experimental detection and analysis of the carrier, thereby achieving accurate filtering of false alarm problems, saving the cost of replacing parts, and greatly shortening the time for searching for the cause of failure. The responsibilities of the car company, parts manufacturer, and user can be further clarified through the cause of failure.

[0080] The working principle of the vehicle failure diagnosis and failure cause analysis method of the present embodiment is as follows:

[0081] Catalyst failure diagnosis;

[0082] The vehicle's onboard diagnostic system (OBD) is a system that provides diagnostic alarms for emissions. Its principle is to determine whether the catalyst has failed by monitoring the oxygen storage capacity of the three-way catalytic converter in real time. The main reasons for OBD alarms include: 1. Catalyst damage and leakage, resulting in abnormal diagnostic oxygen storage capacity; 2. Catalyst carrier oxygen storage capacity decreases due to high temperature or poisoning; 3. Faults in the wiring harness, sensor, etc., leading to false alarms;

[0083] Catalyst carrier oxygen storage principle;

[0084] like Figure 4 As shown, cerium oxide is added as an oxygen storage material in the coating design of the catalyst carrier. Ce (cerium) in the coating will chemically react with the emitted gas pollutants by storing and releasing oxygen, thereby purifying the exhaust gas. The specific reaction equation is as follows:

[0085] Oxygen storage: 2Ce2O3+O2→4CeO2

[0086] 2Ce2O3+2NO→4CeO2+N2

[0087] Ce2O3+H2O→2CeO2+H2

[0088] Oxygen release: 2CeO2+H2→Ce2O3+H2O

[0089] 2CeO2+CO→Ce2O3+CO2.

[0090] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0091] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0092] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst, characterized in that: The specific steps include: S1: Fault confirmation: Read the fault code of the ECU of the faulty vehicle to determine whether it is a catalyst failure fault code; S2: Assembly air tightness test: Place the faulty catalyst in a parts airtightness tester and measure its airtightness. If the leakage exceeds the standard, find the leak point and weld it until the leakage meets the requirement. Then, confirm the fault in the vehicle. If the fault code is not eliminated, proceed to the next step. S3: Carrier oxygen storage capacity test under vehicle working conditions: INCA software is used to read the carrier oxygen storage capacity at different vehicle speeds and compare it with the calibrated aged carrier oxygen storage capacity of the vehicle. If the measured oxygen storage capacity is less than 1.2 times the aged carrier oxygen storage capacity, the next step of bench test is carried out. If it is greater than 1.2 times the aged carrier oxygen storage capacity, the catalyst is considered to be fault-free and the alarm is false. S4: Engine bench operating condition carrier oxygen storage test: Install the assembly on the engine bench and measure the carrier oxygen storage capacity multiple times by controlling the air-fuel ratio. Then take the average value, which is the engine bench oxygen storage capacity of the carrier. If it is higher than 1.2 times the oxygen storage capacity of the aged carrier, it is considered that the catalyst is not faulty and the alarm is false. S5: Carrier failure analysis test, including carrier bonding strength test, carrier specific surface area test, and carrier element analysis.

2. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, characterized in that: In step S2, an air leakage test is performed at a pressure of 30 kPa.

3. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: In step S2, the standard is that the leakage volume should not be greater than 0.5 L / min.

4. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: In step S3, the different vehicle speeds include 50 km / h, 70 km / h, 90 km / h, and 110 km / h, and the vehicle travels at a constant speed for 30 seconds.

5. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: Step S4 specifically includes the following contents: Install the assembly on the engine test bench and stabilize the engine operating conditions at an exhaust mass flow rate of 40kg / h and an exhaust temperature of 450℃. First, reduce the air-fuel ratio to 0.

95. After waiting for the rear oxygen sensor voltage to stabilize for 40s, increase the air-fuel ratio to 1.

05. After the rear oxygen voltage signal drops to a low voltage, read the oxygen storage value. After measuring the oxygen storage value multiple times, take the average value.

6. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: In step S5, the carrier bonding strength test specifically includes the following contents: The carrier with abnormal oxygen storage test results, which is 1.2 times lower than the oxygen storage capacity of the aged carrier, is removed from the assembly. The catalyst carrier is first weighed, and then an air gun is used to blow back and forth for 30 seconds in an area 10 mm away with an air gun pressure of 4.0 bar. The carrier is weighed again. The weight difference before and after the test is compared, and the weight loss rate is calculated. If the bonding strength is greater than 2%, it is determined that the cause of the carrier failure is coating shedding.

7. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: In step S5, the carrier specific surface area test specifically includes the following contents: The carrier with abnormal oxygen storage test results is cut along the middle axis, and a sample with a size of 1cm×1cm×1cm is taken from the center of the carrier and ground into powder. The specific surface area is determined by the amount of gas adsorbed under a given pressure. If the specific surface area is ≤ 70% of the specific surface area of ​​the fresh sample, it is judged that the coating has failed due to abnormally high temperature.

8. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 1, wherein: In step S5, the carrier element analysis specifically includes the following contents: The faulty carrier is ground into powder, and the element types are measured by a spectrometer to determine whether there is chemical element poisoning.

9. The method for diagnosing vehicle failure and analyzing failure causes of an automobile catalyst according to claim 8, wherein: The chemical elements include sulfur, phosphorus, calcium, manganese or lead.

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