CN114961953A - Device for preventing SCR exhaust temperature sensor from cheating and OBD diagnosis method - Google Patents
Device for preventing SCR exhaust temperature sensor from cheating and OBD diagnosis method Download PDFInfo
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- CN114961953A CN114961953A CN202210671457.XA CN202210671457A CN114961953A CN 114961953 A CN114961953 A CN 114961953A CN 202210671457 A CN202210671457 A CN 202210671457A CN 114961953 A CN114961953 A CN 114961953A
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- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000003745 diagnosis Methods 0.000 title claims abstract description 9
- 238000002347 injection Methods 0.000 claims abstract description 113
- 239000007924 injection Substances 0.000 claims abstract description 113
- 239000000523 sample Substances 0.000 claims abstract description 10
- 238000005192 partition Methods 0.000 claims abstract description 8
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 8
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 74
- 239000004202 carbamide Substances 0.000 claims description 74
- 238000012360 testing method Methods 0.000 claims description 67
- 230000002159 abnormal effect Effects 0.000 claims description 12
- 238000002405 diagnostic procedure Methods 0.000 claims description 8
- 230000001154 acute effect Effects 0.000 claims description 3
- 230000002146 bilateral effect Effects 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 13
- 239000000243 solution Substances 0.000 description 8
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 238000009529 body temperature measurement Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- DOTMOQHOJINYBL-UHFFFAOYSA-N molecular nitrogen;molecular oxygen Chemical compound N#N.O=O DOTMOQHOJINYBL-UHFFFAOYSA-N 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Classifications
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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
- F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
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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
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/22—Safety or indicating devices for abnormal conditions
- F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
-
- 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
- F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
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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
-
- 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
Abstract
The invention provides a device for preventing cheating of an SCR exhaust temperature sensor, which comprises: the device comprises an injection pipe, an exhaust temperature sensor, a main cavity and a clamping cavity, wherein the main cavity and the clamping cavity are arranged in an exhaust pipe; a partition plate is arranged between the main cavity and the clamping cavity; the jet orifice of the jet pipe is communicated with the main cavity of the exhaust pipe; the clamping cavity is positioned at the top in the exhaust pipe, and an inlet of the clamping cavity is positioned at the upstream of a jet orifice of the jet pipe; a probe of the exhaust temperature sensor penetrates through the pipe wall of the exhaust pipe and an assembling hole in a partition plate between the clamping cavity and the main cavity and enters the main cavity from the clamping cavity; the probe of the exhaust temperature sensor is located downstream of the injection port of the injection pipe and upstream of an SCR mixer provided in the exhaust pipe. The invention also provides an OBD diagnosis method for preventing cheating of the SCR exhaust temperature sensor. The invention can effectively detect the cheating condition of the exhaust gas temperature sensor.
Description
Technical Field
The invention relates to the technical field of engine tail gas aftertreatment, in particular to a device for preventing cheating of an SCR (selective catalytic reduction) exhaust temperature sensor and an OBD (on-board diagnostics) diagnosis method.
Background
The SCR technology is widely applied to the diesel vehicle market, and the basic principle is that urea solution enters high-temperature tail gas, is hydrolyzed into ammonia gas, and performs catalytic reduction reaction with nitrogen oxides in the tail gas, so that environment-friendly emission is realized. However, the urea solution hydrolysis needs higher temperature, at least the urea solution begins to be slowly decomposed at the temperature of above 160 ℃, the reaction rate of ammonia and nitrogen oxides is related to the characteristics of the catalyst, generally, the efficiency gradually rises in the temperature range of 160-250 ℃, the efficiency keeps stable at the maximum efficiency of 250-500 ℃, the ammonia above 500 ℃ is directly oxidized, and the efficiency gradually falls again. Therefore, the relationship between the urea injection quantity and the temperature is large, and when the urea injection quantity is lower than the urea start-up temperature, the urea cannot be injected; when the temperature is low, the urea injection amount is reduced, because the nitrogen-oxygen conversion efficiency is low, the excessive urea injection cannot reach high catalytic efficiency, and the urea solution is hydrolyzed slowly, so that solid urea crystals block the exhaust pipe.
Therefore, some cheating methods for the exhaust gas temperature sensor appear in the market, such as: the device of the exhaust temperature sensor is heightened, so that the measured temperature is lower than the actual temperature in the exhaust pipe, and the aim of not spraying urea or spraying less urea is fulfilled. The slight heightening has little influence on the temperature measurement, the urea saving amount is limited, the higher heightening base enables the probe to measure the temperature close to the pipe wall of the exhaust pipe, the temperature measurement value is lower seriously, and the urea consumption amount is greatly reduced. In practical application, when the temperature is lower than the urea spraying starting temperature or urea is not sprayed, the vehicle-mounted OBD detection function does not identify the tail gas standard exceeding fault, and a gray space is reserved for maliciously escaping tail gas supervision. Similarly, the ECU is deceived to obtain lower temperature by modifying the temperature sensor wiring harness plug and adding resistance and utilizing the temperature-resistance related characteristic of the temperature sensor, so that the ECU is also an illegal modification which cannot be identified temporarily, and the method is more concealed.
The prior art is as follows: currently, no effective diagnosis method exists for the cheating method, and a commonly used diagnosis method is a built-in temperature model method. The method is a cheating method that the ECU data are filled in the temperature after all working conditions of the engine are stable through running, a heat dissipation model is constructed according to the exhaust flow, the environment temperature and the vehicle speed and wind speed for estimation, the model is extremely rough in precision and large in error reporting margin, only the fault that a sensor is placed in the air in the whole process can be identified, and the padding height of the exhaust temperature sensor cannot be identified. There are the following problems: 1. the difference of different engines is large, and the stable temperature values under the same working condition are different; 2. the specific heat value used in the temperature model is an estimated value, and the specific heat of different catalysts is different; 3. the model is unreasonable to construct, the heat exchange is a complex model, and the temperature is difficult to simulate.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a device for preventing cheating of an SCR exhaust temperature sensor and an OBD diagnosis method. In order to achieve the technical purpose, the embodiment of the invention adopts the technical scheme that:
in a first aspect, an embodiment of the present invention provides an apparatus for preventing cheating of an SCR exhaust temperature sensor, including: the device comprises an injection pipe, an exhaust temperature sensor, a main cavity and a clamping cavity, wherein the main cavity and the clamping cavity are arranged in an exhaust pipe;
a partition plate is arranged between the main cavity and the clamping cavity;
the jet orifice of the jet pipe is communicated with the main cavity of the exhaust pipe; the clamping cavity is positioned at the top in the exhaust pipe, and an inlet of the clamping cavity is positioned at the upstream of a jet orifice of the jet pipe;
a probe of the exhaust temperature sensor penetrates through the pipe wall of the exhaust pipe and an assembling hole in a partition plate between the clamping cavity and the main cavity and enters the main cavity from the clamping cavity; the probe of the exhaust temperature sensor is located downstream of the injection port of the injection pipe and upstream of an SCR mixer provided in the exhaust pipe.
Further, the clamping cavity comprises a left air inlet section, a right air inlet section and a converging cavity; the left air inlet section and the right air inlet section are arranged in parallel and are arranged in bilateral symmetry, the rear parts of the left air inlet section and the right air inlet section are both communicated with the converging cavity, and the rear end of the converging cavity is arranged towards the SCR mixer; and the jet orifice of the jet pipe is positioned between the left air inlet section and the right air inlet section.
Further, the injection pipe is obliquely arranged, and an included angle between the injection direction of the injection pipe and the air flow direction in the exhaust pipe is an acute angle.
In a second aspect, an embodiment of the present invention provides an OBD diagnostic method for preventing cheating of an SCR exhaust gas temperature sensor, which is suitable for the device for preventing cheating of an SCR exhaust gas temperature sensor, and includes the following steps:
step S1, when the engine is powered on, judging whether the absolute value of the difference between the water temperature and the environment temperature is smaller than the set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state, when the engine is not started, whether the absolute value of the difference between the exhaust temperature and the ambient temperature is smaller than the set temperature difference or not is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be in fault;
step S2, after the engine is started, monitoring the rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to the first injection test temperature; the first injection test temperature is higher than 100 ℃ but lower than the urea start-injection temperature;
judging the exhaust temperature drop before and after the small-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibration temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S3, when the engine is in the middle and high load operation condition, and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature, triggering a large-dose urea injection test at intervals; the second injection testing temperature is higher than the urea start-injection temperature, and the third injection testing temperature is lower than 500 ℃;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop delta T is larger than or equal to the temperature drop threshold corresponding to the current working condition, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S4, after the engine is changed from the middle and high load operation condition to the idling operation condition, when the exhaust temperature is higher than the second injection test temperature, triggering a large-dose urea injection test;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibration temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, when the engine is shut down and the exhaust temperature is higher than the first injection test temperature, triggering a large-dose urea injection test;
and judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibrated temperature drop threshold, judging that the exhaust temperature sensor is normal, and otherwise, judging that the exhaust temperature sensor is abnormal.
Further, in step S1, the set temperature difference is 10 ℃.
Further, the nominal temperature drop threshold is set to 5 ℃.
Further, the first spray test temperature is set to be between 110 ℃ and 130 ℃.
Further, the urea injection amount of the small-dose urea injection test is 0.5-1 ml/s;
further, the second and third injection test temperatures were configured to be 250 ℃ and 400 ℃, respectively.
Further, the urea injection amount of the large-dose urea injection test is 1.2ml/s to 1.5 ml/s.
The technical scheme provided by the embodiment of the invention has the following beneficial effects: the exhaust pipe is provided with the layered structure, so that exhaust in the clamping cavity is not influenced by urea injection, exhaust in the main cavity is influenced by urea injection, and whether cheating of the exhaust temperature sensor exists or not is detected by utilizing exhaust temperature change; the anti-cheating device is reasonable in structure, high in detection accuracy rate and capable of effectively preventing cheating.
Drawings
Fig. 1 is a half sectional view of a cheating prevention device in an embodiment of the present invention.
Fig. 2 is a side view of a cheat-preventing device in an embodiment of the present invention.
Fig. 3 is a flowchart of an OBD diagnosis method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In a first aspect, as shown in fig. 1 and 2, an embodiment of the present invention provides an apparatus for preventing cheating of an SCR exhaust gas temperature sensor, including: the device comprises an injection pipe 1, an exhaust temperature sensor 2, a main cavity 301 and a clamping cavity 302 which are arranged in an exhaust pipe 3;
a partition plate is arranged between the main cavity 301 and the clamping cavity 302;
the injection port of the injection pipe 1 is communicated with a main cavity 301 of the exhaust pipe 3; the clamping cavity 302 is positioned at the top in the exhaust pipe 3, and the inlet of the clamping cavity 302 is positioned at the upstream of the injection port of the injection pipe 1;
the probe of the exhaust temperature sensor 2 passes through the pipe wall of the exhaust pipe 3 and an assembling hole on a partition plate between the clamping cavity 302 and the main cavity 301 and enters the main cavity 301 from the clamping cavity 302; the probe of the exhaust gas temperature sensor 2 is located downstream of the injection port of the injection pipe 1 and upstream of the SCR mixer 4 provided in the exhaust pipe 3;
the large arrows in FIG. 1 indicate the direction of engine exhaust flow; under the normal condition of the exhaust temperature sensor 2, through some specially set urea injection tests, urea fog liquid enters a main cavity 301 of the exhaust pipe 1 from an injection port of the injection pipe 1, so that the exhaust temperature sensor 2 has obvious temperature drop; if the exhaust temperature sensor 2 is raised once, the probe of the exhaust temperature sensor 2 can retract into the clamping cavity 302, the injection port of the injection pipe 1 is not directly communicated with the clamping cavity 302, and the temperature measured by the exhaust temperature sensor 2 cannot be obviously changed during urea injection test, so that whether the exhaust temperature sensor 2 is raised or not can be judged; the temperature measured by the exhaust temperature sensor is referred to as exhaust temperature for short in the application;
as an optimization of the present embodiment, the clamping cavity 302 includes a left air inlet section 302a, a right air inlet section 302b and a converging cavity 302 c; the left air inlet section 302a and the right air inlet section 302b are arranged in parallel and in bilateral symmetry, the rear parts of the left air inlet section 302a and the right air inlet section 302b are both communicated with a converging cavity 302c, and the rear end of the converging cavity 302c is arranged towards the SCR mixer 4; the injection port of the injection pipe 1 is positioned in the middle of the left air inlet section 302a and the right air inlet section 302 b; on one hand, the injection orifice of the injection pipe 1 can be aligned to the right middle in the exhaust pipe 3 as much as possible, the urea fog liquid is fully mixed with the tail gas in the exhaust pipe, on the other hand, the clamping cavity 302 can obtain left and right balanced airflow, and airflow disturbance on the downstream SCR mixer 4 is prevented;
as the optimization of the embodiment, the injection pipe 1 is obliquely arranged, and an included angle between the injection direction of the injection pipe 1 and the air flow direction in the exhaust pipe 3 is an acute angle; so that the sprayed urea fog and the tail gas travel together in the same direction;
in a second aspect, as shown in fig. 3, an embodiment of the present invention provides an OBD diagnostic method for preventing cheating of an SCR exhaust temperature sensor, including the steps of:
step S1, when the engine is powered on, judging whether the absolute value of the difference between the water temperature and the environment temperature is smaller than the set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state, when the engine is not started, the exhaust temperature is close to the ambient temperature, whether the absolute value of the difference between the exhaust temperature and the ambient temperature is smaller than the set temperature difference or not is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be in fault;
in this example, the temperature difference was set to 10 ℃;
generally, 10 ℃ deviation has no influence on emission and urea consumption, and illegal resistor modification can cause very large temperature change, for example, PT200 tampering with a 70 ohm resistor can cause a temperature deception value of about 100 ℃, so that the aim of saving urea is fulfilled; the cheating situation that the exhaust gas temperature sensor is modified or the resistance is increased can be detected through the step S1;
step S2, after the engine is started, monitoring the rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to the first injection test temperature; the first injection test temperature is higher than 100 ℃ but lower than the urea start-injection temperature;
the urea start-up temperature is usually set to 180 ℃, the first injection test temperature can be set to be between 110 ℃ and 130 ℃, for example, 120 ℃, and the urea pump does not work continuously because the first injection test temperature is lower than the urea start-up temperature; the heat in the exhaust pipe is low at the moment, and the exhaust temperature measured by the exhaust temperature sensor can be influenced by triggering a small-dose urea injection test once;
the urea injection amount of the small-dose urea injection test is 0.5 ml/s-1 ml/s;
judging the exhaust temperature drop before and after the small-dose urea injection test, if the exhaust temperature drop delta T is greater than or equal to a calibrated temperature drop threshold value, such as 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S3, when the engine is in the middle and high load operation condition, and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature, triggering a large-dose urea injection test at intervals; the second injection testing temperature is higher than the urea start-injection temperature, and the third injection testing temperature is lower than 500 ℃;
in the embodiment, the second injection test temperature and the third injection test temperature are respectively configured to be 250 ℃ and 400 ℃, namely when the exhaust temperature is higher than 250 ℃ and lower than 400 ℃, a large-dose urea injection test is required; the test interval time may be set to half an hour or one hour; the urea injection amount of the large-dose urea injection test is 1.2 ml/s-1.5 ml/s;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop delta T is larger than or equal to the temperature drop threshold corresponding to the current working condition, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
the temperature drop threshold corresponding to the current working condition can be obtained by checking a working condition temperature drop threshold table; for example, a working condition temperature drop threshold table of a certain model is shown in table 1;
TABLE 1
Step S4, after the engine is changed from the middle and high load operation condition to the idling operation condition, when the exhaust temperature is higher than the second injection test temperature, triggering a large-dose urea injection test;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop delta T is greater than or equal to a calibrated temperature drop threshold value, such as 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, when the engine is shut down and the exhaust temperature is higher than the first injection test temperature, triggering a large-dose urea injection test;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop delta T is greater than or equal to a calibrated temperature drop threshold value, such as 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
finally, the urea pump will perform a back-pumping evacuation action.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (10)
1. An apparatus for preventing cheating by an SCR exhaust temperature sensor, comprising: the device comprises an injection pipe (1), an exhaust temperature sensor (2), a main cavity (301) and a clamping cavity (302) which are arranged in an exhaust pipe (3);
a partition plate is arranged between the main cavity (301) and the clamping cavity (302);
the jet orifice of the jet pipe (1) is communicated with a main cavity (301) of the exhaust pipe (3); the clamping cavity (302) is positioned at the top in the exhaust pipe (3), and the inlet of the clamping cavity (302) is positioned at the upstream of the jet orifice of the jet pipe (1);
a probe of the exhaust temperature sensor (2) penetrates through the pipe wall of the exhaust pipe (3) and an assembling hole in a partition plate between the clamping cavity (302) and the main cavity (301) and enters the main cavity (301) from the clamping cavity (302); the probe of the exhaust gas temperature sensor (2) is located downstream of the injection port of the injection pipe (1) and upstream of an SCR mixer (4) provided in the exhaust pipe (3).
2. The apparatus to prevent cheating of an SCR exhaust temperature sensor according to claim 1,
the plenum (302) comprises a left air intake section (302a), a right air intake section (302b), and a converging cavity (302 c); the left air inlet section (302a) and the right air inlet section (302b) are arranged in parallel and in bilateral symmetry, the rear parts of the left air inlet section (302a) and the right air inlet section (302b) are both communicated with a converging cavity (302c), and the rear end of the converging cavity (302c) faces the SCR mixer (4); the injection port of the injection pipe (1) is positioned in the middle of the left air inlet section (302a) and the right air inlet section (302 b).
3. The apparatus to prevent cheating by an SCR exhaust temperature sensor according to claim 1 or 2,
the jet pipe (1) is obliquely arranged, and an included angle between the jet direction of the jet pipe (1) and the air flow direction in the exhaust pipe (3) is an acute angle.
4. An OBD (on-Board diagnostics) diagnosis method for preventing cheating of an SCR exhaust gas temperature sensor, which is suitable for the device for preventing cheating of the SCR exhaust gas temperature sensor according to any one of claims 1 to 3, and is characterized by comprising the following steps of:
step S1, when the engine is powered on, judging whether the absolute value of the difference between the water temperature and the environment temperature is smaller than the set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state, when the engine is not started, whether the absolute value of the difference between the exhaust temperature and the ambient temperature is smaller than the set temperature difference or not is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be in fault;
step S2, after the engine is started, monitoring the rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to the first injection test temperature; the first injection test temperature is higher than 100 ℃ but lower than the urea start-injection temperature;
judging the exhaust temperature drop before and after the small-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibration temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S3, when the engine is in the middle and high load operation condition, and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature, triggering a large-dose urea injection test at intervals; the second injection testing temperature is higher than the urea starting temperature, and the third injection testing temperature is lower than 500 ℃;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop delta T is larger than or equal to the temperature drop threshold corresponding to the current working condition, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S4, when the engine is changed from the middle and high load operation condition to the idling operation condition, when the exhaust temperature is higher than the second injection test temperature, triggering a large-dose urea injection test;
judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibration temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, when the engine is shut down and the exhaust temperature is higher than the first injection test temperature, triggering a large-dose urea injection test;
and judging the exhaust temperature drop before and after the large-dose urea injection test, if the exhaust temperature drop Delta T is greater than or equal to a calibrated temperature drop threshold, judging that the exhaust temperature sensor is normal, and otherwise, judging that the exhaust temperature sensor is abnormal.
5. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
in step S1, the set temperature difference is 10 ℃.
6. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
the first spray test temperature is set to be between 110 ℃ and 130 ℃.
7. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
the nominal temperature drop threshold was set at 5 ℃.
8. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
the urea injection amount of the small-dose urea injection test is 0.5 ml/s-1 ml/s.
9. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
the second and third injection test temperatures were set to 250 ℃ and 400 ℃, respectively.
10. The OBD diagnostic method to prevent cheating by an SCR exhaust temperature sensor of claim 4,
the urea injection amount of the large-dose urea injection test is 1.2 ml/s-1.5 ml/s.
Priority Applications (1)
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