CN114991921A - Method for troubleshooting fault reasons caused by low SCR efficiency - Google Patents
Method for troubleshooting fault reasons caused by low SCR efficiency Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 238000013024 troubleshooting Methods 0.000 title claims abstract description 28
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 128
- 239000004202 carbamide Substances 0.000 claims abstract description 128
- 238000001514 detection method Methods 0.000 claims abstract description 50
- 239000012535 impurity Substances 0.000 claims abstract description 23
- 239000000243 solution Substances 0.000 claims description 46
- 239000007788 liquid Substances 0.000 claims description 15
- 238000012360 testing method Methods 0.000 claims description 11
- 238000002347 injection Methods 0.000 claims description 10
- 239000007924 injection Substances 0.000 claims description 10
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 6
- 238000011065 in-situ storage Methods 0.000 claims description 5
- 230000000694 effects Effects 0.000 abstract description 6
- 238000011835 investigation Methods 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 230000002950 deficient Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
- F01N2900/1806—Properties of reducing agent or dosing system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
- F01N2900/1806—Properties of reducing agent or dosing system
- F01N2900/1818—Concentration of the reducing agent
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
The invention relates to the technical field of exhaust aftertreatment systems, in particular to a method for troubleshooting a fault reason with low SCR efficiency. The technical scheme comprises the following steps: whether the urea solution meets the requirements or not is checked through a urea mass concentration detection module and a urea impurity detection module; whether the NOX sensor works normally is checked through the NOX sensor detection module; checking whether urea can be normally injected; and (4) checking the detection faults and carrying out corresponding treatment, and if the detection results are normal, replacing the SCR. The invention accurately judges the reason of low SCR efficiency by item-by-item feedback type investigation, and combines the detection methods, thereby achieving the effect of improving the investigation effect and further facilitating the user to recover the SCR efficiency by adopting a targeted method.
Description
Technical Field
The invention relates to the technical field of exhaust aftertreatment systems, in particular to a method for troubleshooting a fault cause of low SCR (selective catalytic reduction) efficiency.
Background
At present, trucks running on roads are basically vehicles in the fifth and sixth countries of China, the emission regulation of the sixth country is also implemented at 7-1 month in 2020, the requirements of the emission regulation of the sixth country are clear, and if the emission of the whole vehicle exceeds the requirements of the regulation, the vehicles need to be subjected to a series of operations such as lighting, torque limitation and the like.
In order to reduce NOx and particulate emissions in engine exhaust, the national six diesel engines are matched with an aftertreatment system of a catalytic oxidizer (DOC) + a particulate filter (DPF) + a selective oxidation-reduction device (SCR). No matter the four, five or six national regulations require that the alarm is given when the emission of the NOx in the tail gas exceeds the regulation limit value, and the torque limit and the speed limit are carried out when the emission of the NOx is too high, so that the driving of a driver are influenced.
Through a large number of searches, the following results are found: chinese utility model patent fence: an application number CN202111104525.6, publication number CN113779494A, discloses a method and a device for diagnosing SCR failure, wherein it is described that conversion efficiency calculation parameters of an SCR to be detected are input into an SCR conversion efficiency calculation function, and conversion efficiency values of the SCR to be detected corresponding to N information acquisition time windows are obtained; inputting the conversion efficiency value of the SCR to be detected into a probability density function of the conversion efficiency of the SCR to obtain the probability value of the SCR to be detected as a deterioration part corresponding to each information acquisition window; inputting N probability values of SCR to be detected as a degraded piece corresponding to N information acquisition time windows into a probability factor calculation function of the SCR as the degraded piece to obtain a probability factor of the SCR as the degraded piece; and when the probability factor that the SCR is a degraded piece is larger than a preset probability factor, determining that the SCR is in fault. However, the troubleshooting method is complex, needs to be operated by professionals, is high in cost of the troubleshooting device, is low in practicability, and needs to be based on the situation, so that the troubleshooting method which is simple in operation, high in practicability and low in cost is urgently needed to troubleshoot the reasons of low SCR efficiency, guide the relevant operation after sale to recover the SCR efficiency, further avoid alarming, torque limiting and speed limiting, and further improve the user experience.
Disclosure of Invention
The invention provides a method for troubleshooting fault reasons of low SCR efficiency, which solves the technical problems.
The scheme for solving the technical problems is as follows:
the utility model provides a SCR inefficiency fault cause investigation system, includes urea mass concentration detection module that is used for urea concentration detection, urea impurity detection module that is used for urea impurity detection and NOx sensor detection module that is used for gaseous detection, examines through the combination feedback formula of urea mass concentration detection module, urea impurity detection module and NOx sensor detection module to the accurate reason that judges SCR inefficiency, thereby adopts the method of pertinence to resume SCR efficiency.
Furthermore, the urea mass concentration detection module is a refractometer, the urea impurity detection module is oil test paper, and the NOX sensor detection module is a nitrogen oxide detector.
Further, the urea solution is dripped on a refractometer prism, and the refractivity of the urea solution is read by the refractometer to measure the urea concentration, so that SCR fault factors caused by the urea mass concentration are checked; judging whether the urea solution contains oil according to whether the test paper changes color, and checking SCR fault factors caused by impurities in the urea solution; whether the NOx value of the NOx sensor in the data flow is in a normal range in an idling state is detected through a gas sensor in the NOx detector, and the NOx sensor is used for checking SCR fault factors caused by the NOx sensor.
A method for checking failure reasons of SCR low efficiency comprises the following steps:
whether the urea solution meets the requirements or not is checked through a urea mass concentration detection module and a urea impurity detection module; whether the NOX sensor works normally is checked through the NOX sensor detection module; checking whether urea can be normally injected; and (4) checking the detection faults and carrying out corresponding treatment, and if the detection results are normal, replacing the SCR.
The invention has the beneficial effects that: whether the mass concentration of the urea is normal, whether the urea solution contains impurities, whether an NOX sensor is normal, whether the pressure build-up of a urea pump is normal, whether SCR is defective or not and the like are sequentially checked, the reason that the SCR efficiency is low is accurately judged by item-by-item feedback type checking, and the detection methods are combined with one another, so that the effect of improving the checking effect is achieved, and a user can conveniently recover the SCR efficiency by adopting a targeted method. Therefore, compared with the comparison file, the method disclosed by the invention has the advantages that the reason of low SCR efficiency is accurately judged by a method which is simple to operate and high in practicability, and meanwhile, the detection cost is low.
On the basis of the technical scheme, the invention can be improved as follows.
Further, the working process for checking whether the urea solution meets the requirements is as follows:
1) checking the liquid level of the urea tank to ensure that the liquid level of the urea tank is moderate and excessive urea solution or insufficient urea solution is eliminated;
2) taking a small amount of urea from a urea box by using a proper tool, dripping the urea on a refractometer prism, and reading the refractive index of the urea solution by using the refractometer to measure the concentration of the urea;
3) and (5) detecting whether the urea solution contains oil or not by using oil test paper.
Further, if the concentration of the urea solution is not within the range of 30.5% -34.5%, the standard urea solution is replaced.
And if the test paper changes color, the urea solution contains oil, the clean urea solution is replaced, and the SCR hydraulic system is cleaned.
Further, the method of checking whether the NOX sensor can operate normally is: whether the NOx value in the data flow is in a reasonable range through a universal diagnostic instrument in an idling state; and if the NOx value is not in the range, replacing the NOx sensor.
Further, the specifically checking whether urea can be normally injected includes: detaching the nozzle from the EGP, stepping on an accelerator in situ, and observing whether the urea injection system can normally build pressure for injection; and if the urea cannot be injected normally, the pressure build failure fault of the system is checked.
Further, the troubleshooting process of the system voltage reduction failure is as follows:
connecting a diagnostic instrument to ensure that the engine has no electrical appliance fault code; a transparent urea liquid inlet pipe is used, one end of the transparent liquid return pipe is connected with a urea pump, and the other end of the transparent liquid return pipe is connected with a urea barrel; igniting the engine, stepping on an accelerator in situ to enable the exhaust temperature to reach more than 180 ℃ so as to meet the pressure building condition; the diagnostic instrument detects whether the voltage is built up normally.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to make the technical solutions of the present invention practical in accordance with the contents of the specification, the following detailed description is given of preferred embodiments of the present invention with reference to the accompanying drawings. The detailed description of the present invention is given in detail by the following examples and the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention.
In the drawings:
FIG. 1 is a schematic view of a SCR inefficiency troubleshooting process of the present invention;
fig. 2 is a schematic diagram of a system step-down failure troubleshooting process according to the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention. The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for purposes of illustration only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The present invention will be described in further detail with reference to specific embodiments.
Example one
The SCR low-efficiency fault cause troubleshooting system comprises a urea mass concentration detection module for detecting urea concentration, a urea impurity detection module for detecting urea impurities and an NOx sensor detection module for detecting gas, and the SCR low-efficiency cause is accurately judged through combined feedback type troubleshooting of the urea mass concentration detection module, the urea impurity detection module and the NOx sensor detection module, so that the SCR efficiency is recovered by adopting a targeted method.
Furthermore, the urea mass concentration detection module is a refractometer, the urea impurity detection module is oil test paper, and the NOX sensor detection module is a nitrogen oxide detector.
Further, urea solution is dripped on a refractometer prism, the refractivity of the urea solution is read through the refractometer to measure the concentration of the urea, and the urea solution is used for checking SCR fault factors caused by the mass concentration of the urea; judging whether the urea solution contains oil according to whether the test paper changes color, and checking SCR fault factors caused by impurities in the urea solution; and detecting whether the NOX value of the NOX sensor in the data flow is in a normal range in an idling state through a gas sensor in the NOX detector, and checking SCR fault factors caused by the NOX sensor.
An SCR inefficiency fault cause troubleshooting method, which is combined with fig. 1, and includes:
A. checking whether the urea mass concentration is normal
The urea mass concentration analysis method comprises the steps of reading the refractive index of a urea solution through a refractometer, reading the refractive index, measuring the urea mass concentration according to the refractive index, and if the urea mass concentration is not within a reasonable range, judging that the reason of low SCR efficiency is poor urea mass, wherein the reasonable value range is 30.5% -34.5%;
B. checking the urea solution for impurities
After the urea mass concentration is determined to be normal, oil paper is required to be used for detecting whether the urea solution contains oil or not, if the test paper changes color, the urea solution contains oil, the clean urea solution needs to be replaced, and an SCR hydraulic system needs to be cleaned;
C. checking whether NOx sensor is working normally
After determining that the urea solution is free of impurities, checking whether the NOx sensor can work normally is needed, wherein the checking method comprises the following steps: under the idle working condition, a diagnostic instrument is used for checking whether an NOx sensor in a data stream is in a reasonable range, the range of a reasonable value is different along with engines with different displacement, such as a 2.5L engine and an engine with the rated power of 125KW, and under the idle working condition, the reasonable range of the NOx value is 150 plus 220 PPM;
D. checking urea injection system to establish normal pressure
After the NOX sensor works normally, the method for checking whether the urea injection system can build pressure normally comprises the following steps: the nozzle was removed from the EGP to observe that stepping on the throttle in place entered conditions where injection was possible: the exhaust temperature is higher than the temperature limit, whether normal pressure build-up injection can be carried out or not is observed, the temperature limit value is basically about 190-220 ℃ along with different engine displacements, and if the normal injection cannot be carried out, the fault check of the pressure build-up failure of the urea pump needs to be checked;
E. replacing SCR
If the urea injection system can build pressure and inject urea normally, the SCR efficiency is caused by SCR crystallization, SCR poisoning and the like, and the SCR needs to be replaced.
When the SCR efficiency is low and the fault occurs, the post-treatment system is checked, and the checking sequence comprises the mass concentration of urea, whether the urea solution contains impurities, an NOX sensor, the pressure build-up of a urea pump and SCR. Whether the mass concentration of the urea is normal, whether the urea solution contains impurities, whether an NOX sensor is normal, whether the pressure build-up of a urea pump is normal, whether an SCR is defective or not and the like are sequentially checked, the reason that the SCR efficiency is low is accurately judged by item-by-item feedback type checking, and the detection methods are combined with one another, so that the effect of improving the checking effect is achieved, and a user can conveniently recover the SCR efficiency by adopting a targeted method. Therefore, compared with the comparison file, the method provided by the invention has the advantages that the reason of low SCR efficiency is accurately judged by a method which is simple to operate and high in practicability, and meanwhile, the detection cost is low.
Example two
Compared with the first embodiment, the method for troubleshooting the fault reason of the low efficiency of the SCR provided by the invention further includes: the system step-down failure troubleshooting method introduces the system step-down failure troubleshooting flow in detail by combining with fig. 2:
connecting a diagnostic instrument to ensure that no electric appliance fault code exists in an engine;
secondly, a transparent urea liquid inlet pipe is used, and one end of a transparent liquid return pipe is connected with a urea pump and the other end is connected with a urea barrel;
igniting the engine, stepping on the accelerator in situ to enable the exhaust temperature to reach over 180 ℃ and meet the pressure building condition;
step four, the diagnostic instrument detects whether the pressure is normally built, in the pressure building process, if the pressure does not reach the required value in unit time, the post-processing state is changed from the pressure building stage to the reverse pumping (considering the influence of air in the pipeline), the pressure is built again after the reverse pumping is carried out for a period of time, and if the reverse pumping is still unsuccessful for 2 times, the system reports the pressure building failure fault;
if yes, detecting whether the pipeline and the urea box filter screen are blocked or not, and cleaning or replacing related parts;
if not, checking whether a filter screen of a liquid inlet of the pump is blocked;
if the filter screen of the liquid inlet is blocked, the filter screen needs to be cleaned or replaced;
if the filter screen of the liquid inlet is not blocked, the urea pump needs to be replaced.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner; the present invention may be readily implemented by those of ordinary skill in the art as illustrated in the accompanying drawings and described above; however, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the scope of the invention as defined by the appended claims; meanwhile, any equivalent changes, modifications and evolutions made to the above embodiments according to the substantial technology of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (10)
1. The system for troubleshooting the fault reasons of the low SCR efficiency is characterized by comprising a urea mass concentration detection module for detecting the urea concentration, a urea impurity detection module for detecting urea impurities and an NOx sensor detection module for detecting gas, and is used for accurately judging the reasons of the low SCR efficiency by combined feedback type troubleshooting of the urea mass concentration detection module, the urea impurity detection module and the NOx sensor detection module, so that the SCR efficiency is recovered by adopting a targeted method.
2. The SCR inefficiency cause troubleshooting system of claim 1 wherein: the urea mass concentration detection module is a refractometer, the urea impurity detection module is oil test paper, and the NOX sensor detection module is a nitrogen oxide detector.
3. The SCR inefficiency cause troubleshooting system of claim 2 wherein: the urea solution is dripped on a refractometer prism, and the refractivity of the urea solution is read by the refractometer to measure the urea concentration, so that SCR fault factors caused by the urea mass concentration are checked; judging whether the urea solution contains oil according to whether the test paper changes color, and checking SCR fault factors caused by impurities in the urea solution; and detecting whether the NOX value of the NOX sensor in the data flow is in a normal range in an idling state through a gas sensor in the NOX detector, and checking SCR fault factors caused by the NOX sensor.
4. A method for checking failure reasons of SCR low efficiency is characterized by comprising the following steps:
whether the urea solution meets the requirements or not is checked through a urea mass concentration detection module and a urea impurity detection module; whether the NOX sensor works normally is checked through the NOX sensor detection module; checking whether urea can be normally injected; and (4) checking the detection faults and carrying out corresponding treatment, and if the detection results are normal, replacing the SCR.
5. The method for troubleshooting the cause of the SCR inefficiency according to claim 4, wherein: the working process for checking whether the urea solution meets the requirements is as follows:
1) checking the liquid level of the urea box to ensure that the liquid level of the urea box is moderate, and removing excessive urea solution or too little urea solution;
2) taking a small amount of urea from a urea box by using a proper tool, dripping the urea on a refractometer prism, and reading the refractive index of the urea solution by using the refractometer to measure the concentration of the urea;
3) and (5) detecting whether the urea solution contains oil or not by using oil test paper.
6. The method for troubleshooting reasons for the SCR inefficiency according to claim 5, wherein: if the concentration of the urea solution is not within the range of 30.5-34.5%, the standard urea solution is replaced.
7. The method for troubleshooting reasons for the SCR inefficiency according to claim 5, wherein: if the test paper changes color, the urea solution contains oil, the clean urea solution is replaced, and the SCR hydraulic system is cleaned.
8. The method for troubleshooting reasons for the SCR inefficiency according to claim 4, wherein: the method for checking whether the NOx sensor can work normally comprises the following steps: whether the NOx value in the data flow is in a reasonable range through a universal diagnostic instrument in an idling state; and if the NOx value is not in the range, replacing the NOx sensor.
9. The method for troubleshooting reasons for the SCR inefficiency according to claim 4, wherein: the specific steps for checking whether urea can be injected normally include: detaching the nozzle from the EGP, stepping on an accelerator in situ, and observing whether the urea injection system can normally build pressure for injection; and if the urea cannot be injected normally, the pressure build failure fault of the system is checked.
10. The method for troubleshooting a cause of failure of SCR according to claim 9, characterized in that: the troubleshooting process of the system voltage reduction failure comprises the following steps:
connecting a diagnostic instrument to ensure that the engine has no electrical appliance fault code; a transparent urea liquid inlet pipe is used, one end of the transparent liquid return pipe is connected with a urea pump, and the other end of the transparent liquid return pipe is connected with a urea barrel; igniting the engine, stepping on an accelerator in situ to enable the exhaust temperature to reach more than 180 ℃ so as to meet the pressure building condition; the diagnostic instrument detects whether the voltage is built up normally.
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| CN202210583690.2A CN114991921B (en) | 2022-05-25 | 2022-05-25 | SCR (selective catalytic reduction) low-efficiency fault cause investigation method |
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