CN107740717B - Secondary air valve on-line monitoring system - Google Patents

Secondary air valve on-line monitoring system Download PDF

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CN107740717B
CN107740717B CN201710855472.9A CN201710855472A CN107740717B CN 107740717 B CN107740717 B CN 107740717B CN 201710855472 A CN201710855472 A CN 201710855472A CN 107740717 B CN107740717 B CN 107740717B
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secondary air
air flow
flow
theoretical
valve
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CN107740717A (en
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颜松
宋同好
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FAW Group Corp
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10Exhaust 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
    • F01N3/24Exhaust 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 constructional aspects of converting apparatus
    • F01N3/30Arrangements for supply of additional air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10Exhaust 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
    • F01N3/18Exhaust 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
    • F01N3/22Control of additional air supply only, e.g. using by-passes or variable air pump drives
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/40Engine 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 provides a secondary air valve on-line monitoring system, comprising: the device comprises an engine, a secondary air control valve, a secondary air pump, an exhaust pipe, a linear oxygen sensor, a control module and a secondary air device online monitoring module, wherein the secondary air device online monitoring module determines the actual secondary air flow based on data collected by the linear oxygen sensor and the control module under the condition of meeting a preset condition, determines the predicted theoretical secondary air flow based on a preset method, and realizes the tightness monitoring of the secondary air valve by comparing the difference between the actual secondary air flow and the predicted theoretical secondary air flow. The secondary air valve on-line monitoring system can obtain a stable and reliable diagnosis result, thereby meeting the requirements of regulations.

Description

Secondary air valve on-line monitoring system
Technical Field
The invention relates to an online monitoring system for a secondary air valve, in particular to an online monitoring system for a secondary air valve of a gasoline vehicle, which is suitable for gasoline engine vehicles provided with secondary air devices and is particularly applied to the technical field of electronic emission control of automobiles.
Background
The secondary air supply system is one of the evolved devices outside the machine for reducing the exhaust emission, and increases the oxygen content of the exhaust by blowing additional air into the exhaust. After mixing with high-temperature exhaust gas discharged from the engine at idle, the mixture is re-oxidized in the exhaust pipe, and carbon monoxide (CO) and Hydrocarbons (HC) are re-combusted in a high-temperature environment. The secondary air supply system operates during a cold start of the vehicle, and the device has the functions of reducing harmful emissions during the cold start and heating the three-way catalyst to quickly reach a normal operating temperature, thereby meeting the emission requirements of regulations.
The most vulnerable component of a secondary air device to failure is the secondary air valve due to the harsh operating environment. The secondary air valve belongs to a mechanical valve, carbon deposition, rusting and other phenomena are easy to occur, the secondary air valve core and the base can not be kept sealed, the control precision of the secondary air is influenced, and therefore emission can not be effectively reduced. It is therefore important to be able to accurately monitor the leakage of the valve in time to meet regulatory requirements.
Patent CN201210566877.8 (publication No. CN103573360A, publication date: 2014.02.12) discloses a vehicle having a system and method for diagnosing a secondary air injection device. The secondary air injection device is monitored by an oxygen sensor signal and a pressure sensor signal, the intake air flow rate is monitored by a pressure sensor, and whether a malfunction exists is determined by comparing the in-cylinder air-fuel ratio with the air-fuel ratio measured by the oxygen sensor. However, if a two-point oxygen sensor is employed, the obtained air-fuel ratio signal shows only a rich-lean state, which is an inaccurate signal due to a non-quantized value; even if a linear oxygen sensor is adopted, stable results cannot be guaranteed due to large instantaneous fluctuation of an air-fuel ratio signal.
Therefore, a diagnosis scheme with anti-interference effect and capable of obtaining stable and reliable diagnosis results is urgently needed.
Disclosure of Invention
The technical problem to be solved by the embodiment of the invention is to provide a secondary air valve on-line monitoring system which can obtain stable and reliable diagnosis results so as to meet the requirements of regulations.
The technical scheme adopted by the invention is as follows:
the embodiment of the invention provides an online monitoring system for a secondary air valve, which comprises: an engine, a secondary air control valve, a secondary air pump, an exhaust pipe, a linear oxygen sensor, a control module, a secondary air device online monitoring module, wherein the exhaust pipe is connected with the engine, the secondary air valve is connected with the secondary air pump and communicated with the exhaust pipe, the secondary air control valve is connected with the secondary air valve, the linear oxygen sensor is arranged on the exhaust pipe, the secondary air device online monitoring module controls the operation of the secondary air control valve and the secondary air pump, and the control module is in communication connection with the secondary air device online monitoring module, wherein the secondary air device online monitoring module determines the actual secondary air flow based on the data collected by the linear oxygen sensor and the control module and determines the predicted theoretical secondary air flow based on a preset method when a preset condition is met, monitoring the tightness of the secondary air valve is accomplished by comparing the difference between the actual secondary air flow and the predicted theoretical secondary air flow.
Optionally, the preset condition specifically includes: related components except the secondary air pump, the secondary air valve and the secondary air control valve have no fault; the difference between the temperature when the engine is stopped last time and the temperature when the engine is started this time exceeds 10 ℃; the temperature range of the inlet air of the engine is within 5-50 ℃; the temperature of the engine is within 30-110 ℃; the temperature of a secondary air pump coil is lower than 100 ℃; the vehicle speed is 0; the ratio of the current ambient pressure to the standard pressure is greater than 0.75; the mean value of the lambda control factor deviates within + -0.1 from the theoretical value range.
Optionally, the online secondary air device monitoring module determines an actual secondary air flow based on data collected by the linear oxygen sensor and the control module and a predicted theoretical secondary air flow based on a preset method when a preset condition is met, and the monitoring of the tightness of the secondary air valve by comparing a difference between the actual secondary air flow and the predicted theoretical secondary air flow specifically includes: the secondary air device on-line monitoring module closes the secondary air valve and simultaneously opens the secondary air pump; the secondary air device on-line monitoring module acquires an engine intake air flow, an excess air coefficient acquisition value, an engine in-cylinder excess air coefficient and a lambda closed-loop control factor mean value from the control module to determine the actual secondary air flow; the excess air coefficient acquisition value is a value acquired by the linear oxygen sensor and is sent to the control module, and the average value of the excess air coefficient and the lambda closed-loop control factor in the engine cylinder is calculated through the engine state information acquired by the control module; determining a deviation of the intake air flow based on the actual secondary air flow and the lambda closed-loop control factor mean deviation; determining a primary theoretical flow according to a characteristic curve of the secondary air theoretical flow and the electric quantity of a storage battery providing a power supply for a secondary air pump, and correcting the determined primary theoretical flow to obtain the predicted theoretical secondary air flow; determining a secondary air relative flow based on the actual secondary air flow, the deviation in the intake air flow, and the theoretical secondary air flow; comparing the determined relative flow of secondary air with a preset relative flow threshold of secondary air, and determining the tightness of the secondary air valve based on the comparison result.
Alternatively, the actual secondary air flow rate is determined by the following equation (1):
wherein M isSAIFor actual secondary air flow, MINKIs the engine intake air flow, lambdaO2Excess air factor acquisition value, lambda, for linear oxygen sensor acquisitionCYLFor calculated air excess coefficient in engine cylinder, fλIs the calculated mean value of the lambda closed-loop control factor.
Alternatively, the deviation of the intake air flow rate is determined by the following formula (2):
ΔMINK=MINK×Δfλ(2)
wherein, Δ MINKAs deviation of intake air flow, Δ fλIs the mean deviation of the lambda closed-loop control factor.
Optionally, the mean deviation of the λ closed-loop control factor is determined by:
calculating the deviation between the mean value of the lambda closed-loop control factor and the theoretical value, and comparing the calculated deviation delta fλAnd carrying out low-pass filtering to obtain the mean deviation of the lambda closed-loop control factor.
Optionally, the relative flow of secondary air is determined by the following equation (3):
Figure BDA0001413873880000032
wherein R isSAIFor relative flow of secondary air, MSAIFor actual secondary air flow, MSAITFor the predicted theoretical secondary air flow, Δ MINKIs the deviation of the intake air flow rate.
Optionally, the modifying the determined preliminary theoretical flow rate to obtain the predicted theoretical secondary air flow rate specifically includes: multiplying the determined preliminary theoretical flow by a correction factor to obtain the predicted theoretical secondary air flow; the correction factor is the quotient of the current ambient pressure and the standard atmospheric pressure.
Optionally, comparing the determined relative flow of secondary air with a preset relative flow threshold of secondary air, the determining the tightness of the secondary air valve based on the comparison result comprising:
and if the determined relative flow of the secondary air exceeds the preset relative flow threshold of the secondary air, indicating that the secondary air valve is not tight in sealing.
Compared with the prior art, the secondary air valve online monitoring system provided by the embodiment of the invention is a method for calculating the actual secondary air flow and the theoretical secondary air flow predicted by a model based on the original oxygen sensor of the system, realizing the tightness monitoring of the secondary air valve by comparing the difference between the actual secondary air flow and the theoretical secondary air flow, calculating the secondary air flow by the mean value of the lambda closed-loop control factor, and monitoring the leakage of the secondary air valve by the secondary air flow, has an anti-interference effect, can obtain a stable and reliable diagnosis result, and can meet the requirements of regulations.
Drawings
FIG. 1 is a schematic structural diagram of an online monitoring system for a secondary air valve provided in an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a monitoring method of the online monitoring system for the secondary air valve provided by the embodiment of the invention;
FIG. 3 is a graph of maximum secondary air versus flow threshold and excess air ratio.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic structural diagram of an online monitoring system for a secondary air valve provided in an embodiment of the present invention; FIG. 2 is a schematic flow chart of a monitoring method of the online monitoring system for the secondary air valve provided by the embodiment of the invention; FIG. 3 is a graph of maximum secondary air relative flow threshold versus air-fuel ratio.
As shown in fig. 1, an embodiment of the present invention provides an online monitoring system for a secondary air valve, including: the secondary air control system comprises an engine 1, a secondary air control valve 2, a secondary air valve 3, a secondary air pump 4, an exhaust pipe 5, a linear oxygen sensor 6, a control module 9 and a secondary air device online monitoring module 10, wherein the exhaust pipe 5 is connected with the engine 1, the secondary air valve 3 is connected with the secondary air pump 4 and communicated with the exhaust pipe 5, the secondary air control valve 2 is connected with the secondary air valve 3, the linear oxygen sensor 6 is arranged on the exhaust pipe 5, the secondary air device online monitoring module 10 controls the secondary air control valve 2 and the secondary air pump 4, the control module 9 is in communication connection with the secondary air device online monitoring module 10, and the control module 9 mainly controls ignition, oil injection, air intake and torque of the engine so as to enable the engine to normally run. Under the condition that a preset condition is met, the secondary air device online monitoring module 10 determines an actual secondary air flow based on data collected by the linear oxygen sensor 6 and the control module 9 and determines a predicted theoretical secondary air flow based on a preset method, realizes the tightness monitoring of the secondary air valve by comparing the difference between the actual secondary air flow and the predicted theoretical secondary air flow, specifically can monitor the tightness of the secondary air valve 3 by using the data collection channel 7 and the control module communication channel 11, specifically can acquire state information and the like about the engine 1 from the control module 9 through the data collection channel 7 or the control module communication channel 11, and judges whether the secondary air valve can be monitored by operating a monitoring algorithm of related software. As shown in fig. 1, the secondary air device online monitoring module 10 is connected to the secondary air control valve 2 and the secondary air pump 4 via wiring harnesses, respectively, and controls the opening and closing operations of the secondary air control valve 2 and the secondary air pump 4 for a set time. In the present invention, the related components of the online monitoring system for the secondary air valve are all in the prior art, and therefore, the detailed description thereof is omitted in order to avoid redundancy.
Specifically, the preset conditions in the present invention may include the following conditions:
(1) no failure of relevant parts except the secondary air device;
(2) the difference between the temperature when the engine is stopped last time and the temperature when the engine is started this time exceeds 10 ℃;
(3) the temperature range of the inlet air is within 5-50 ℃;
(4) the temperature of the engine is within 30-110 ℃;
(5) the secondary air pump coil temperature should be below 100 ℃;
(6) the vehicle speed is 0;
(7) the ratio of the current ambient pressure to the standard pressure should be greater than 0.75;
(8) the mean value of the lambda control factor deviates within + -0.1 from the theoretical value range, typical values of the general theoretical value being 1.
The preset conditions can be acquired through the data acquisition channel 7 or acquired from the control module 9 through the control module communication channel 11, and after the conditions are simultaneously met, the online secondary air device monitoring module 10 starts to monitor the tightness of the secondary air valve 3 after delaying the preset time, wherein the preset time is about 1 second generally.
Specifically, as shown in fig. 2, the secondary air device online monitoring module determines an actual secondary air flow based on the data collected by the linear oxygen sensor 6 and the control module 9 and a predicted theoretical secondary air flow based on a preset method under the condition that the preset conditions are simultaneously met, and the monitoring of the tightness of the secondary air valve by comparing the difference between the actual secondary air flow and the predicted theoretical secondary air flow may specifically include the following steps:
s101, the secondary air valve is closed by the secondary air device on-line monitoring module, and the secondary air pump is started at the same time.
S102, the secondary air device on-line monitoring module acquires an engine intake air flow, an excess air coefficient acquisition value, an excess air coefficient in an engine cylinder and a lambda closed-loop control factor mean value from the control module to determine the actual secondary air flow;
in this step, the actual secondary air flow rate is determined mainly based on the linear oxygen sensor 6. The excess air coefficient acquisition value is a value acquired by the linear oxygen sensor and is sent to the control module, and the excess air coefficient in the engine cylinder and the lambda closed-loop control factor mean value are calculated through engine state information acquired by the control module and can be specifically obtained through calculation by related software of the control module 9. Specifically, the secondary air device online monitoring module 10 obtains a λ signal, an intake air flow signal and a λ closed-loop control factor mean value signal from the control module 9 through the data acquisition channel 7, i.e. the one-chip microcomputer hardware a/D channel and the data acquisition control channel 8, i.e. the one-chip microcomputer hardware drive and a/D channel, wherein the actual secondary air flow can be determined by the following formula (1):
wherein M isSAIFor actual secondary air flow, MINKIs the engine intake air flow, lambdaO2Excess air factor acquisition value, lambda, for linear oxygen sensor acquisitionCYLFor calculated air excess coefficient in engine cylinder, fλThe calculated lambda closed-loop control factor average value is used for correcting the rich and lean state of the engine air mixture.
S103, determining the deviation of the air inlet flow based on the actual secondary air flow and the mean deviation of the lambda closed-loop control factor.
In this step, the deviation of the intake air flow rate is determined by the following formula (2):
ΔMINK=MINK×Δfλ(2)
wherein, Δ MINKAs deviation of intake air flow, Δ fλIs the mean deviation of the lambda closed-loop control factor.
Wherein the mean deviation of the lambda closed-loop control factor can be determined by:
calculating the deviation between the mean value of the lambda closed-loop control factor and the theoretical value, and comparing the calculated deviation delta fλLow-pass filtering (typical value of the filter time constant: 100 ms) is performed to obtain the mean deviation of the lambda closed-loop control factor.
And S104, determining a primary theoretical flow according to the characteristic curve of the electric quantity of the storage battery for providing power supply for the secondary air pump and the theoretical flow of the secondary air, and correcting the determined primary theoretical flow to obtain the predicted theoretical secondary air flow.
In this step, the characteristic curve of the theoretical flow rate of secondary air is provided by the supplier, and the corresponding secondary primary theoretical flow rate can be found according to the electric quantity of the storage battery for the fixed corresponding relation between the electric quantity of the storage battery and the primary theoretical flow rate of secondary air. Considering the influence of the exhaust back pressure and the air density, the determined primary theoretical flow rate needs to be corrected so as to obtain the predicted theoretical secondary air flow rate, and the method specifically comprises the following steps: multiplying the determined preliminary theoretical flow by a correction factor to obtain the predicted theoretical secondary air flow; the correction factor is the quotient of the current ambient pressure and the standard atmospheric pressure.
And S105, determining the relative flow of the secondary air based on the actual secondary air flow, the deviation of the air inlet flow and the theoretical secondary air flow.
In this step, the relative flow rate of the secondary air can be determined by the following formula (3):
wherein R isSAIFor relative flow of secondary air, MSAIFor actual secondary air flow, MSAITFor the predicted theoretical secondary air flow, Δ MINKIs the deviation of the intake air flow rate.
And S106, comparing the determined relative flow of the secondary air with a preset relative flow threshold of the secondary air, and determining the tightness of the secondary air valve based on the comparison result.
In this step, if the determined relative flow rate of the secondary air exceeds the preset relative flow rate threshold of the secondary air, which is related to the excess air factor, as shown in fig. 3, the specific relationship may be provided by the supplier, it indicates that the secondary air valve is not tight in sealing and air leakage occurs.
In conclusion, the method does not need to increase any cost, calculates the actual secondary air flow based on the original oxygen sensor of the system and the theoretical secondary air flow predicted by the model, realizes the tightness monitoring of the secondary air valve by comparing the difference between the actual secondary air flow and the theoretical secondary air flow, calculates the secondary air flow by the mean value of the closed-loop control factor, monitors the leakage of the secondary air valve by the secondary air flow, has an anti-interference effect, can obtain a stable and reliable diagnosis result, and can meet the requirements of regulations.
The above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (3)

1. An online secondary air valve monitoring system, comprising: the system comprises an engine, a secondary air control valve, a secondary air pump, an exhaust pipe, a linear oxygen sensor, a control module and a secondary air device online monitoring module, wherein the exhaust pipe is connected with the engine, the secondary air valve is connected with the secondary air pump and communicated with the exhaust pipe, the secondary air control valve is connected with the secondary air valve, the linear oxygen sensor is arranged on the exhaust pipe, the secondary air device online monitoring module controls the operation of the secondary air control valve and the operation of the secondary air pump, and the control module is in communication connection with the secondary air device online monitoring module,
the online secondary air device monitoring module determines an actual secondary air flow based on data collected by the linear oxygen sensor and the control module and a predicted theoretical secondary air flow based on a preset method under the condition that a preset condition is met, and realizes the tightness monitoring of the secondary air valve by comparing the difference between the actual secondary air flow and the predicted theoretical secondary air flow, and the online secondary air device monitoring method specifically comprises the following steps:
the secondary air device on-line monitoring module closes the secondary air valve and simultaneously opens the secondary air pump;
the secondary air device on-line monitoring module acquires an engine intake air flow, an excess air coefficient acquisition value, an engine in-cylinder excess air coefficient and a lambda closed-loop control factor mean value from the control module to determine the actual secondary air flow; the excess air coefficient acquisition value is a value acquired by the linear oxygen sensor and is sent to the control module, and the average value of the excess air coefficient and the lambda closed-loop control factor in the engine cylinder is calculated through the engine state information acquired by the control module;
determining a deviation of the intake air flow based on the actual secondary air flow and the lambda closed-loop control factor mean deviation;
determining a primary theoretical flow according to a characteristic curve of the secondary air theoretical flow and the electric quantity of a storage battery providing a power supply for a secondary air pump, and correcting the determined primary theoretical flow to obtain the predicted theoretical secondary air flow;
determining a secondary air relative flow based on the actual secondary air flow, the deviation in the intake air flow, and the theoretical secondary air flow;
comparing the determined relative flow of secondary air with a preset relative flow threshold of secondary air, and determining the tightness of the secondary air valve based on the comparison result;
the actual secondary air flow rate is determined by the following equation (1):
Figure FDA0002234551700000021
wherein M isSAIFor actual secondary air flow, MINKIs the engine intake air flow, lambdaO2Excess air factor acquisition value, lambda, for linear oxygen sensor acquisitionCYLFor calculated air excess coefficient in engine cylinder, fλCalculating the mean value of the lambda closed-loop control factor;
wherein the deviation of the intake air flow rate is determined by the following formula (2):
ΔMINK=MINK×Δfλ(2)
wherein, Δ MINKAs deviation of intake air flow, Δ fλMean deviation of lambda closed-loop control factor;
the mean deviation of the lambda closed-loop control factor is determined by:
calculating the deviation between the mean value of the lambda closed-loop control factor and the theoretical value, and comparing the calculated deviation delta fλPerforming low-pass filtering to obtain the mean deviation of the lambda closed-loop control factor;
the secondary air relative flow rate is determined by the following formula (3):
Figure FDA0002234551700000022
wherein R isSAIFor relative flow of secondary air, MSAIFor actual secondary air flow, MSAITFor the predicted theoretical secondary air flow, Δ MINKDeviation of intake air flow rate;
the correcting the determined preliminary theoretical flow rate to obtain the predicted theoretical secondary air flow rate specifically includes: multiplying the determined preliminary theoretical flow by a correction factor to obtain the predicted theoretical secondary air flow; the correction factor is the quotient of the current ambient pressure and the standard atmospheric pressure.
2. The online monitoring system of a secondary air valve according to claim 1, characterized in that the preset conditions specifically include:
related components except the secondary air pump, the secondary air valve and the secondary air control valve have no fault; the difference between the temperature when the engine is stopped last time and the temperature when the engine is started this time exceeds 10 ℃; the temperature range of the inlet air of the engine is within 5-50 ℃; the temperature of the engine is within 30-110 ℃; the temperature of a secondary air pump coil is lower than 100 ℃; the vehicle speed is 0; the ratio of the current ambient pressure to the standard pressure is greater than 0.75; the mean value of the lambda control factor deviates within + -0.1 from the theoretical value range.
3. The online secondary air valve monitoring system of claim 1, wherein the determined relative secondary air flow is compared to a preset relative secondary air flow threshold, and determining the tightness of the secondary air valve based on the comparison comprises:
and if the determined relative flow of the secondary air exceeds the preset relative flow threshold of the secondary air, indicating that the secondary air valve is not tight in sealing.
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