CN114961953B - 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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- CN114961953B CN114961953B CN202210671457.XA CN202210671457A CN114961953B CN 114961953 B CN114961953 B CN 114961953B CN 202210671457 A CN202210671457 A CN 202210671457A CN 114961953 B CN114961953 B CN 114961953B
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- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000003745 diagnosis Methods 0.000 title claims abstract description 10
- 238000002347 injection Methods 0.000 claims abstract description 98
- 239000007924 injection Substances 0.000 claims abstract description 98
- 239000000523 sample Substances 0.000 claims abstract description 12
- 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 73
- 239000004202 carbamide Substances 0.000 claims description 73
- 238000012360 testing method Methods 0.000 claims description 68
- 230000002159 abnormal effect Effects 0.000 claims description 12
- 238000012544 monitoring process Methods 0.000 claims description 4
- 230000001154 acute effect Effects 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 13
- 239000000243 solution Substances 0.000 description 7
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 230000008859 change Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification 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
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 241000209202 Bromus secalinus Species 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
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002405 diagnostic procedure Methods 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
- 239000003595 mist Substances 0.000 description 1
- DOTMOQHOJINYBL-UHFFFAOYSA-N molecular nitrogen;molecular oxygen Chemical compound N#N.O=O DOTMOQHOJINYBL-UHFFFAOYSA-N 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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
-
- 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
-
- 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 the 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 board 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 the inlet of the clamping cavity is positioned at the upstream of the jet orifice of the jet pipe; the probe of the exhaust temperature sensor passes through the pipe wall of the exhaust pipe, and the probe enters the main cavity from the clamping cavity through the assembly holes on the partition plate between the clamping cavity and the main cavity; the probe of the exhaust gas temperature sensor is located downstream of the injection port of the injection pipe and upstream of the SCR mixer provided in the exhaust pipe. The invention also provides an OBD diagnosis method for preventing the SCR exhaust temperature sensor from cheating. The invention can effectively detect the cheating situation of the exhaust temperature sensor.
Description
Technical Field
The invention relates to the technical field of engine exhaust aftertreatment, in particular to a device for preventing an SCR exhaust temperature sensor from cheating and an OBD 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 and is hydrolyzed into ammonia gas, and the ammonia gas and nitrogen oxides in the tail gas undergo catalytic reduction reaction, so that environment-friendly emission is realized. However, the hydrolysis of urea solution requires a relatively high temperature, at least the reaction rate of ammonia and nitrogen oxides begins to decompose slowly above 160 ℃, and the catalyst characteristics are related, generally, the efficiency gradually increases within the temperature range of 160-250 ℃, the efficiency keeps stable maximum efficiency within the temperature range of 250-500 ℃, ammonia above 500 ℃ is directly oxidized, and the efficiency gradually decreases again. Therefore, the relation between the urea injection quantity and the temperature is large, and when the urea injection quantity is lower than the urea injection starting temperature, urea cannot be injected; in the low temperature area, the urea injection amount can be reduced, because the nitrogen-oxygen conversion efficiency is low at this time, the excessive urea injection can not reach higher catalytic efficiency, and the urea solution is slowly hydrolyzed, so that solid urea crystals block the exhaust pipe.
Thus, some cheating methods for exhaust gas temperature sensors are emerging on the market, such as: the device for heightening the exhaust temperature sensor enables the measured temperature to be lower than the actual temperature in the exhaust pipe, and achieves the purpose of not spraying urea or less spraying urea. Slight heightening has little influence on temperature measurement, the urea saving amount is limited, and a higher heightening base enables a probe to measure the temperature close to the pipe wall of the exhaust pipe, so that the temperature measurement value is low and serious, and the urea consumption is greatly reduced. In practical application, the vehicle-mounted OBD detection function does not recognize the tail gas exceeding fault when the temperature is lower than the starting temperature of urea or the urea is not sprayed, and a gray space is reserved for monitoring malicious escape tail gas. Similarly, the temperature sensor harness plug is modified, the resistance is increased, the ECU is deceived to obtain lower temperature by utilizing the temperature-resistance related characteristic of the temperature sensor, and the temperature sensor harness plug is also illegally modified which cannot be identified temporarily, so that the temperature sensor harness plug is more concealed.
The prior art comprises the following steps: currently, no effective diagnosis mode exists for the cheating method, and a common diagnosis method is a built-in temperature model method. The stable temperature of each working point is filled into ECU data through the universal working condition of the running engine, a heat dissipation model constructed according to the exhaust flow, the ambient temperature, the vehicle speed and the wind speed is estimated, the model precision is particularly rough, the error reporting margin is particularly large, only the fault of the whole-course sensor in the air can be identified, and the cheating method of the heightening of the exhaust temperature sensor cannot be identified. There are the following problems: 1. different engines have large differences, and the stable temperature values of the same working condition have differences; 2. specific heat values used in the temperature model are estimated values, and 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 an SCR exhaust temperature sensor from cheating and an OBD diagnosis method. In order to achieve the technical purpose, the technical scheme adopted by the embodiment of the invention is as follows:
In a first aspect, 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, 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 board 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 the inlet of the clamping cavity is positioned at the upstream of the jet orifice of the jet pipe;
The probe of the exhaust temperature sensor passes through the pipe wall of the exhaust pipe, and the probe enters the main cavity from the clamping cavity through the assembly holes on the partition plate between the clamping cavity and the main cavity; the probe of the exhaust gas temperature sensor is located downstream of the injection port of the injection pipe and upstream of the 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 parallel and are symmetrically arranged left and right, the rear parts of the left air inlet section and the right air inlet section are communicated with a converging cavity, and the rear end of the converging cavity is arranged towards the SCR mixer; the jet orifice of the jet pipe is positioned in the middle of the left air inlet section and the right air inlet section.
Further, the jet pipe is obliquely arranged, and an included angle between the jet direction of the jet 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 diagnosis method for preventing cheating of an SCR exhaust gas temperature sensor, which is applicable to the device for preventing cheating of an SCR exhaust gas temperature sensor as described above, including the following steps:
Step S1, when the engine is electrified, judging whether the absolute value of the difference between the water temperature and the ambient temperature is smaller than a set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state at the moment, when the engine is not started yet, whether the absolute value of the difference between the exhaust temperature and the ambient temperature is smaller than the set temperature difference is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be faulty;
Step S2, after the engine is started, monitoring rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to a first injection test temperature; the first injection test temperature is higher than 100 ℃ but lower than the urea start-injection temperature;
Judging the temperature drop of the exhaust before and after the small-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
Step S3, triggering a large-dose urea injection test at intervals when the engine is in a medium-high load operation condition and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature; the second injection test temperature is higher than the urea start-injection temperature, and the third injection test temperature is lower than 500 ℃;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the temperature drop threshold value 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 exhaust temperature is higher than the second injection test temperature after the engine is converted from the medium-high load operation condition to the idle operation condition, triggering a large-dose urea injection test;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, triggering a large-dose urea injection test when the engine is flameout and the exhaust temperature is higher than the first injection test temperature;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal.
Further, in step S1, the set temperature difference is 10 ℃.
Further, the calibrated temperature drop threshold is set to 5 ℃.
Further, the first spray test temperature is set to between 110 ℃ and 130 ℃.
Further, the urea injection quantity of the small-dose urea injection test is 0.5 ml/s-1 ml/s;
Further, the second injection test temperature and the third injection test temperature were respectively configured to be 250 ℃ and 400 ℃.
Further, the urea injection quantity of the large-dose urea injection test is 1.2 ml/s-1.5 ml/s.
The technical scheme provided by the embodiment of the application has the beneficial effects that: according to the application, the layered structure is arranged in the exhaust pipe, 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 the exhaust temperature sensor cheats or not is detected by utilizing exhaust temperature change; the application has reasonable structure and high detection accuracy, and effectively prevents cheating.
Drawings
Fig. 1 is a half-sectional view of a tamper-evident device in accordance with an embodiment of the present invention.
Fig. 2 is a side view of a tamper evident device in an embodiment of the present invention.
Fig. 3 is a flowchart of an OBD diagnostic method in an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In a first aspect, as shown in fig. 1 and 2, an embodiment of the present invention proposes an apparatus for preventing cheating of an SCR exhaust gas temperature sensor, including: a jet pipe 1, an exhaust temperature sensor 2, a main chamber 301 provided in an exhaust pipe 3, and a clamp chamber 302;
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 the 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;
The probe of the exhaust temperature sensor 2 passes through the pipe wall of the exhaust pipe 3 and the assembly holes on the 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 arrow in fig. 1 is the engine exhaust flow direction; under the normal condition of the exhaust temperature sensor 2, through a plurality of specially-set urea injection tests, urea fog enters the main cavity 301 of the exhaust pipe 1 from the 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 lifted once, the probe of the exhaust temperature sensor 2 is retracted 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 does not change obviously during urea injection test, so that whether the exhaust temperature sensor 2 is lifted or not can be judged; the temperature measured by the exhaust temperature sensor is simply referred to as exhaust temperature;
As an optimization of the present embodiment, the clamping chamber 302 includes a left air intake section 302a, a right air intake section 302b, and a converging chamber 302c; the left air inlet section 302a and the right air inlet section 302b are parallel and are symmetrically arranged left and right, the rear parts of the left air inlet section 302a and the right air inlet section 302b are communicated with a converging cavity 302c, and the rear end of the converging cavity 302c is arranged towards the SCR mixer 4; the jet orifice of the jet 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 jet orifice of the jet pipe 1 can be aligned to the middle in the exhaust pipe 3 as much as possible, urea fog is fully mixed with tail gas in the exhaust pipe, and on the other hand, balanced air flow is obtained in the clamping cavity 302, so that air flow disturbance to the downstream SCR mixer 4 is prevented;
As an 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 mist 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 proposes an OBD diagnosis method for preventing cheating of an SCR exhaust temperature sensor, comprising the steps of:
Step S1, when the engine is electrified, judging whether the absolute value of the difference between the water temperature and the ambient temperature is smaller than a set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state at the moment, when the engine is not started yet, 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 is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be faulty;
In this example, the temperature difference is set to 10 ℃;
In general, the deviation of 10 ℃ has no influence on emission and urea consumption, the illegal resistance modification can cause great temperature change, for example, PT200 is tampered with 70 omega resistance to cause a temperature deception value of about 100 ℃, so that the aim of saving urea is fulfilled; the cheating situation of refitting or increasing the resistance on the exhaust temperature sensor can be detected through the step S1;
Step S2, after the engine is started, monitoring rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to a 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 typically set to 180 ℃, and the first injection test temperature may be set to between 110 ℃ and 130 ℃, for example 120 ℃, and the urea pump will not continue to operate because the first injection test temperature is lower than the urea start-up temperature; the heat in the exhaust pipe is low, 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 quantity of the small-dose urea injection test is 0.5 ml/s-1 ml/s;
Judging the temperature drop of the exhaust before and after the small-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to a calibrated temperature drop threshold value, for example, 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
Step S3, triggering a large-dose urea injection test at intervals when the engine is in a medium-high load operation condition and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature; the second injection test temperature is higher than the urea start-injection temperature, and the third injection test 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 less than 250 ℃ and less than 400 ℃, large-dose urea injection test is required; the test interval time may be set to half an hour or one hour; the urea injection quantity of the large-dose urea injection test is 1.2 ml/s-1.5 ml/s;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the temperature drop threshold value 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, the temperature drop threshold value table of the working condition of a certain model is shown in table 1;
TABLE 1
Step S4, when the exhaust temperature is higher than the second injection test temperature after the engine is converted from the medium-high load operation condition to the idle operation condition, triggering a large-dose urea injection test;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to a calibrated temperature drop threshold value, for example, 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, triggering a large-dose urea injection test when the engine is flameout and the exhaust temperature is higher than the first injection test temperature;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to a calibrated temperature drop threshold value, for example, 5 ℃, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
Finally, the urea pump will perform the back-pumping and emptying actions.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same, 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 and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and equivalents are intended to be encompassed in the scope of the claims of the present invention.
Claims (8)
1. An apparatus for preventing cheating of an SCR exhaust gas temperature sensor, comprising: a jet 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 board is arranged between the main cavity (301) and the clamping cavity (302);
The jet orifice of the jet pipe (1) is communicated with the main cavity (301) of the exhaust pipe (3); the clamping cavity (302) is positioned at the top in the exhaust pipe (3), and an inlet of the clamping cavity (302) is positioned at the upstream of the jet orifice of the jet pipe (1);
The probe of the exhaust temperature sensor (2) passes through the pipe wall of the exhaust pipe (3) and the assembly holes on the 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 temperature sensor (2) is positioned at the downstream of the jet orifice of the jet pipe (1) and at the upstream of the SCR mixer (4) arranged in the exhaust pipe (3);
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;
the clamping cavity (302) comprises a left air inlet section (302 a), a right air inlet section (302 b) and a converging cavity (302 c); the left air inlet section (302 a) and the right air inlet section (302 b) are parallel and are symmetrically arranged left and right, the rear parts of the left air inlet section (302 a) and the right air inlet section (302 b) are communicated with a converging cavity (302 c), and the rear end of the converging cavity (302 c) is arranged towards the SCR mixer (4); the jet orifice of the jet pipe (1) is positioned in the middle of the left air inlet section (302 a) and the right air inlet section (302 b).
2. An OBD diagnosis method for preventing cheating of an SCR exhaust gas temperature sensor, adapted to the apparatus for preventing cheating of an SCR exhaust gas temperature sensor as set forth in claim 1, comprising the steps of:
Step S1, when the engine is electrified, judging whether the absolute value of the difference between the water temperature and the ambient temperature is smaller than a set temperature difference, if not, waiting for starting the engine; if so, the engine is in a cold start state at the moment, when the engine is not started yet, whether the absolute value of the difference between the exhaust temperature and the ambient temperature is smaller than the set temperature difference is continuously judged, if so, the engine is started, and if not, the exhaust temperature sensor is judged to be faulty;
Step S2, after the engine is started, monitoring rising exhaust temperature, and triggering a small-dose urea injection test when the exhaust temperature is equal to a first injection test temperature; the first injection test temperature is higher than 100 ℃ but lower than the urea start-injection temperature;
Judging the temperature drop of the exhaust before and after the small-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
Step S3, triggering a large-dose urea injection test at intervals when the engine is in a medium-high load operation condition and the second injection test temperature is less than the exhaust temperature and less than the third injection test temperature; the second injection test temperature is higher than the urea start-injection temperature, and the third injection test temperature is lower than 500 ℃;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the temperature drop threshold value 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 exhaust temperature is higher than the second injection test temperature after the engine is converted from the medium-high load operation condition to the idle operation condition, triggering a large-dose urea injection test;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal;
step S5, triggering a large-dose urea injection test when the engine is flameout and the exhaust temperature is higher than the first injection test temperature;
Judging the temperature drop of the exhaust before and after the large-dose urea injection test, if the delta T of the exhaust Wen Wenjiang is larger than or equal to the calibrated temperature drop threshold value, judging that the exhaust temperature sensor is normal, otherwise, judging that the exhaust temperature sensor is abnormal.
3. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
In step S1, the set temperature difference is 10 ℃.
4. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
The first spray test temperature is set between 110 ℃ and 130 ℃.
5. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
The calibrated temperature drop threshold is set to 5 ℃.
6. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
The urea injection quantity of the small-dose urea injection test is 0.5 ml/s-1 ml/s.
7. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
The second and third spray test temperatures were respectively configured to 250 ℃ and 400 ℃.
8. The method for diagnosing an OBD against cheating an SCR exhaust temperature sensor according to claim 2,
The urea injection quantity of the large-dose urea injection test is 1.2 ml/s-1.5 ml/s.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210671457.XA CN114961953B (en) | 2022-06-14 | 2022-06-14 | Device for preventing SCR exhaust temperature sensor from cheating and OBD diagnosis method |
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| CN103551034A (en) * | 2013-11-05 | 2014-02-05 | 国家电网公司 | Urea-pyrolysis ammonia preparation device |
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| CN209413969U (en) * | 2019-01-28 | 2019-09-20 | 凯龙高科技股份有限公司 | A kind of urea liquid bimetallic tube mixer for SCR system |
| CN110985173A (en) * | 2019-12-13 | 2020-04-10 | 华东交通大学 | Exhaust temperature sensor diagnosis method based on exhaust temperature characteristics under different fuel injection quantities |
| CN212838031U (en) * | 2020-05-27 | 2021-03-30 | 郑州精益达环保科技有限公司 | Linear type exhaust purification post-treatment device for national six-diesel engine |
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| CN103551034A (en) * | 2013-11-05 | 2014-02-05 | 国家电网公司 | Urea-pyrolysis ammonia preparation device |
| CN105402007A (en) * | 2015-12-17 | 2016-03-16 | 无锡威孚力达催化净化器有限责任公司 | Box type post processing assembly for diesel vehicle |
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