CN115075927B - Mixed motor vehicle type engine catalyst degradation diagnosis method - Google Patents

Mixed motor vehicle type engine catalyst degradation diagnosis method Download PDF

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CN115075927B
CN115075927B CN202210715281.3A CN202210715281A CN115075927B CN 115075927 B CN115075927 B CN 115075927B CN 202210715281 A CN202210715281 A CN 202210715281A CN 115075927 B CN115075927 B CN 115075927B
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catalyst
engine
supplementary
fuel ratio
diagnosis method
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CN115075927A (en
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张春娇
王冬
彭红涛
岳永召
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Dongfeng Motor Corp
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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
    • 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
    • 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
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/021—Engine temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/04—Engine intake system parameters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
    • F02D2200/101—Engine speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/70—Input parameters for engine control said parameters being related to the vehicle exterior
    • F02D2200/703—Atmospheric pressure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
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  • Exhaust Gas After Treatment (AREA)
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Abstract

The invention discloses a method for diagnosing degradation of a catalyst of a hybrid vehicle type engine, which comprises the following steps of S1, judging whether the engine is currently under a steady-state working condition, if the engine is under the steady-state working condition, continuing the diagnosing step, otherwise, stopping diagnosing; s2, periodically enriching and reducing the target air-fuel ratio, and repeating for a plurality of periods; judging whether the catalyst has a degradation fault or not according to the air-fuel ratio signal of the oxygen sensor at the upstream of the catalyst and the voltage signal of the oxygen sensor at the downstream of the catalyst, if the catalyst has the degradation fault, stopping diagnosis, otherwise, performing subsequent supplementary diagnosis; s3, presetting a plurality of different supplementary diagnosis methods for supplementary diagnosis, respectively judging whether each supplementary diagnosis method meets corresponding starting conditions according to a certain rule, and selecting one of the diagnosis methods meeting the starting conditions for supplementary diagnosis.

Description

Mixed motor vehicle type engine catalyst degradation diagnosis method
Technical Field
The invention relates to the field of catalyst diagnosis, in particular to a method for diagnosing degradation of a catalyst of a hybrid vehicle type engine.
Background
The three-way catalyst is an indispensable purification device installed in an automobile exhaust system, wherein the three-way catalyst contains a catalyst, and the catalyst has the function of converting harmful gases such as CO, HC and NOx discharged from automobile exhaust into carbon dioxide, water and nitrogen which can be discharged into the atmosphere through oxidation and reduction.
The existing EMS system is provided with two oxygen sensors in front of and behind the catalyst, the front oxygen is used for realizing closed-loop control on the mixed gas, and the rear oxygen can be used for realizing aging diagnosis on the catalyst by comparing the difference between the front oxygen sensor and the rear oxygen sensor. This approach requires purging the catalyst of oxygen and storing oxygen in the full catalyst to read its oxygen storage capacity, which is too long for a fresh catalyst to diagnose; and the purifying capacity of the catalyst for HC, CO and NOX and the Oxygen Storage Capacity (OSC) thereof have a certain nonlinear relation, and if the purifying capacity of the catalyst is simply relied on, misjudgment on the purifying capacity of the catalyst can be caused.
Disclosure of Invention
The invention aims to provide a method for diagnosing degradation of a catalyst of a hybrid vehicle type engine so as to improve the accuracy of a catalyst diagnosis result.
In order to solve the technical problems, the invention provides a technical scheme that: a method for diagnosing deterioration of a catalyst of an engine of a hybrid vehicle comprises the steps of,
s1, judging whether the engine is currently under a steady-state working condition, if so, continuing the diagnosis step, otherwise, stopping the diagnosis;
s2, periodically enriching and reducing the target air-fuel ratio, and repeating for a plurality of periods; judging whether the catalyst has a degradation fault or not according to the air-fuel ratio signal of the oxygen sensor at the upstream of the catalyst and the voltage signal of the oxygen sensor at the downstream of the catalyst, if the catalyst has the degradation fault, stopping diagnosis, otherwise, performing subsequent supplementary diagnosis;
s3, presetting a plurality of different supplementary diagnosis methods for supplementary diagnosis, respectively judging whether each supplementary diagnosis method meets corresponding starting conditions according to a certain rule, and selecting one of the diagnosis methods meeting the starting conditions for supplementary diagnosis.
According to the scheme, S1 is specifically as follows, and the engine is judged to be under a steady-state working condition only when all the following conditions are met;
1) The fluctuation of the engine speed is maintained in a preset fluctuation range, and the duration exceeds T1;
2) The fluctuation of the density of fresh air charge of the engine is maintained in a preset range, and the duration exceeds T2;
3) The fluctuation of the water temperature of the engine is maintained in a preset range, and the duration exceeds T3;
4) The atmospheric pressure continues unchanged and the duration exceeds T4;
5) The actual ignition efficiency fluctuation of the engine is maintained in a preset range and the duration exceeds T5
6) The target air-fuel ratio is the current stoichiometric air-fuel ratio;
7) The air-fuel ratio control is continuously in a closed-loop activation state, and the duration exceeds T6;
8) The temperature of the catalyst is within a preset range;
9) The difference between the engine requested road torque and the actual road torque is maintained within a preset range and the duration exceeds T7.
According to the scheme, t1=t2=t3=t5=t6=t7, the value range is 19-21 s, and the value range of T4 is 55-65 s; the preset range of the fluctuation of the engine speed is +/-20 rpm, the preset range of the fluctuation of the fresh air intake density of the engine is +/-5 mgpl, the preset range of the fluctuation of the engine water temperature is +/-2 ℃, the preset range of the fluctuation of the actual ignition efficiency of the engine is +/-0.08, the preset range of the temperature of the catalyst is 400-950 ℃, and the preset range of the difference value between the engine request road torque and the actual road torque is +/-3 Nm.
According to the above scheme, the basic diagnosis method of S2 is specifically as follows,
let the air-fuel ratio control time be T base The method comprises the steps of carrying out a first treatment on the surface of the First at T base Enriching the target air-fuel ratio to the original r in time Rich Multiple times, then at T base Reducing the target air-fuel ratio to the original r in time Lean Doubling and circulating N 0 A cycle; wherein r is Rich 、r Lean Respectively an enrichment coefficient and a thinning coefficient; then, a judgment is made that,
1) The air-fuel ratio signal of the oxygen sensor upstream of the catalyst exhibits the following characteristics,
first, r is the initial air-fuel ratio signal when the control is not being enriched or lean Rich X (1+Δr) times, and for T base Time of +Δt, followed by r of the initial air-fuel ratio signal at the time of non-rich or lean control Lean X (1+Δr) times, and for T base +Δt, and cycle N above signal characteristics 0 A cycle; wherein Deltar is coefficient judgment allowance, deltat is time judgment allowance;
2) The difference between the maximum value and the minimum value of the voltage signal of the oxygen sensor at the downstream of the catalyst does not exceed a set voltage threshold;
if condition 1) is not satisfied, or condition 1) is satisfied but condition 2) is not satisfied, judging that the catalyst has a degradation fault, and stopping diagnosis, otherwise, continuing subsequent supplementary diagnosis.
According to the scheme, T base The value range is 0.04 to 0.06s, r Rich The value range is 0.94-0.96, r Lean The value range is 1.04-1.06, deltar= + -0.01, deltat 0.005-0.015 s, N 0 The value range is 8-12, and the voltage threshold value in the condition 2) is 15-25 mV.
According to the above-described aspects, the supplementary diagnosis methods described in S3 include three kinds in total, including a first supplementary diagnosis method, a second supplementary diagnosis method, and a third supplementary diagnosis method;
the selection rule of the supplementary diagnosis method is that if the first supplementary diagnosis method is adopted in the last driving cycle, the second supplementary diagnosis method is preferentially judged in the driving cycle, if the starting condition of the second supplementary diagnosis method is met, only the second supplementary diagnosis method is executed in the driving cycle, if the starting condition of the second supplementary diagnosis method is not met, but the starting condition of the third supplementary diagnosis method is met, only the third supplementary diagnosis method is executed in the driving cycle, and if the starting conditions of the second and third supplementary diagnosis methods are not met, only the first supplementary diagnosis method is executed in the driving cycle.
According to the above-described scheme, the first supplementary diagnosis method is as follows,
let the air-fuel ratio control time be T base +T Delta First at T base +T Delta Concentrating to original r in time Rich Multiple times, then at T base +T Delta Reducing the target air-fuel ratio to the original r in time Lean The voltage fluctuation of the oxygen sensor which is multiplied and circulated to the downstream of the catalyst is stabilized within a certain amplitude range; recording the voltage signal of the oxygen sensor downstream of the catalyst before the cycle, the stabilized voltage signal V 0 Time T required for voltage rise 0 The method comprises the steps of carrying out a first treatment on the surface of the If T 0 ≥T 0Limi The supplementary diagnosis result is that the catalyst has a degradation fault, otherwise, the catalyst has no degradation fault;
wherein T0Limit The time limit value required for the voltage rise is calculated specifically as follows,
Figure BDA0003708575220000041
/>
wherein ,TC For the base time, which is the engine speed n, the fresh air intake density rho and the catalyst temperature T of the catalyst in the deterioration critical limit state Catalyst The time required for the voltage of the oxygen sensor at the downstream of the catalyst under the working condition to rise; f (n, rho) is a correction factor based on the current engine speed n, fresh air intake density rho,
Figure BDA0003708575220000042
based on the base temperature T of the catalyst CatalystBase and TCatalyst Is (are) correction factors>
Figure BDA0003708575220000043
The average value of the catalyst temperature obtained through the calibration of the engine bench from the time of target air-fuel ratio adjustment to the time of stabilizing the voltage fluctuation of the oxygen sensor at the downstream of the catalyst within a certain range; />
Figure BDA0003708575220000044
For the actual mileage Sigma L of the vehicle and the set basic mileage L of the engine Base The correction factor obtained;
when the diagnosis result of the first supplementary diagnosis method is that the catalyst has no degradation fault, T is measured in the process of the first supplementary diagnosis method 0 、V 0 According to the corresponding engine speed n, fresh air intake density rho
Figure BDA0003708575220000045
And storing.
According to the above scheme, the starting condition of the second supplementary diagnosis method is that if the current high-voltage battery SOC is greater than a threshold value SOC Min And meeting the steady-state working condition, and meeting the starting condition of the second supplementary diagnosis method;
the second supplementary diagnostic method is specifically as follows,
after the second supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the second supplementary diagnosis method, and otherwise, stopping the second supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M To make the engine request the air path torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching a target air-fuel ratio for a time period, at T base Reducing the target air-fuel ratio in time, and periodically adjusting the target air-fuel ratio until the voltage signal of the oxygen sensor downstream of the catalyst is stabilized within a preset range, and recording the voltage signal of the oxygen sensor downstream of the catalyst at the initial stage of the target air-fuel ratio adjustment and the voltage signal V of the oxygen sensor downstream of the catalyst at the time of stabilization 1 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 1 ；
The V is set up above 1 、T 1 According to the corresponding engine speed n, fresh air intake density rho
Figure BDA0003708575220000051
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure BDA0003708575220000052
V under the working condition of (2) 0 、T 0 ；
If |V 1 -V 0 |＞ΔE V Judging that the catalyst degradation diagnosis result is not reliable, and ending the diagnosis; wherein ΔE V Is a preset voltage value;
if |V 1 -V 0 |≤ΔE V And T is 1 -T 0 ≥ΔT High1 Judging that the catalyst has a degradation fault;
if |V 1 -V 0 |≤ΔE V And DeltaT Low1 ＜T 1 -T 0 ＜ΔT High1 Judging that the catalyst has no degradation fault;
wherein ,
Figure BDA0003708575220000053
in the formula f1 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 1 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Engine requested gas circuit torque M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure BDA0003708575220000054
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta A correction factor obtained from the ratio of (2);
ΔT High1 each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure BDA0003708575220000055
ΔT Low1 the correction factors are obtained by calibrating the catalyst in the idle state.
According to the above scheme, the starting condition of the third supplementary diagnosis method is that if the current high-voltage battery SOC is smaller than a threshold value SOC Max And meeting the steady-state working condition, and meeting the starting condition of the second supplementary diagnosis method;
the third supplementary diagnostic method is specifically as follows,
after the third supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the third supplementary diagnosis method, and otherwise, stopping the third supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M To make the engine request the air path torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching a target air-fuel ratio for a time period, at T base Reducing the target air-fuel ratio in time, and periodically adjusting the target air-fuel ratio until the voltage signal of the oxygen sensor downstream of the catalyst is stabilized within a preset range, and recording the voltage signal of the oxygen sensor downstream of the catalyst at the initial stage of the target air-fuel ratio adjustment and the voltage signal V of the oxygen sensor downstream of the catalyst at the time of stabilization 2 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 2 ；
The V is set up above 2 、T 2 According to the corresponding engine speed n, fresh air intake density rho
Figure BDA0003708575220000061
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure BDA0003708575220000062
V under the working condition of (2) 0 、T 0 ；
If |V 2 -V 0 |＞ΔE V Judging that the catalyst degradation diagnosis result is not reliable, and ending the diagnosis; wherein ΔE V Is a preset voltage value;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≥ΔT High2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≤ΔT Low2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V ，ΔT Low2 ＜T 0 -T 2 ＜ΔT High Judging that the catalyst has no degradation fault;
wherein ,
Figure BDA0003708575220000063
in the formula f3 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 3 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Engine requested gas circuit torque M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure BDA0003708575220000071
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta A correction factor obtained from the ratio of (2);
ΔT High2 each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure BDA0003708575220000072
ΔT Low1 the correction factors are obtained by calibrating the catalyst in the idle state.
According to the scheme, delta E V The value range is 11-13 mV.
The beneficial effects of the invention are as follows: the influence on emission in the catalyst diagnosis process is reduced by periodically adjusting the air-fuel ratio to be enriched and attenuated; meanwhile, active diagnosis is carried out on the premise of not influencing the power of the vehicle, and different diagnosis modes are selected according to the working condition of the vehicle, so that the diagnosis precision is improved.
Drawings
Fig. 1 is a method for diagnosing deterioration of a catalyst of a hybrid vehicle type engine according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments, which can be made by one of ordinary skill in the art without the need for inventive faculty, are within the scope of the present disclosure, based on the described embodiments of the present disclosure.
Referring to fig. 1, a hybrid vehicle type engine catalyst degradation diagnosis method includes the steps of,
s1, judging whether the engine is currently under a steady-state working condition, if so, continuing the diagnosis step, otherwise, stopping the diagnosis;
s2, periodically enriching and reducing the target air-fuel ratio, and repeating for a plurality of periods; judging whether the catalyst has a degradation fault or not according to the air-fuel ratio signal of the oxygen sensor at the upstream of the catalyst and the voltage signal of the oxygen sensor at the downstream of the catalyst, if the catalyst has the degradation fault, stopping diagnosis, otherwise, performing subsequent supplementary diagnosis;
s3, presetting a plurality of different supplementary diagnosis methods for supplementary diagnosis, respectively judging whether each supplementary diagnosis method meets corresponding starting conditions according to a certain rule, and selecting one of the diagnosis methods meeting the starting conditions for supplementary diagnosis.
Further, S1 is specifically as follows, and the engine is judged to be under a steady-state working condition only when all the following conditions are met;
1) The fluctuation of the engine speed is maintained in a preset fluctuation range, and the duration exceeds T1;
2) The fluctuation of the density of fresh air charge of the engine is maintained in a preset range, and the duration exceeds T2;
3) The fluctuation of the water temperature of the engine is maintained in a preset range, and the duration exceeds T3;
4) The atmospheric pressure continues unchanged and the duration exceeds T4;
5) The actual ignition efficiency fluctuation of the engine is maintained in a preset range and the duration exceeds T5
6) The target air-fuel ratio is the current stoichiometric air-fuel ratio;
7) The air-fuel ratio control is continuously in a closed-loop activation state, and the duration exceeds T6;
8) The temperature of the catalyst is within a preset range;
9) The difference between the engine requested road torque and the actual road torque is maintained within a preset range and the duration exceeds T7.
Further, t1=t2=t3=t5=t6=t7=20s, t4=60 s; the preset range of the fluctuation of the engine speed is +/-20 rpm, the preset range of the fluctuation of the fresh air intake density of the engine is +/-5 mgpl, the preset range of the fluctuation of the engine water temperature is +/-2 ℃, the preset range of the fluctuation of the actual ignition efficiency of the engine is +/-0.08, the preset range of the temperature of the catalyst is 400-950 ℃, and the preset range of the difference value between the engine request road torque and the actual road torque is +/-3 Nm.
Further, the basic diagnosis method of S2 is specifically as follows,
let the air-fuel ratio control time be T base (the value is 0.05s in the embodiment); first at T base Enriching the target air-fuel ratio to the original r in time Ric (value of 0.95 in this example), followed by T base Reducing the target air-fuel ratio to the original r in time Lean (1.05 in this example) and circulates N 0 (the value in the embodiment is 10) cycles; wherein r is Rich 、r Lean Respectively an enrichment coefficient and a thinning coefficient; then, a judgment is made that,
1) The air-fuel ratio signal of the oxygen sensor upstream of the catalyst exhibits the following characteristics,
first, r is the initial air-fuel ratio signal when the control is not being enriched or lean Rich X (1+Δr) (Δr in this example is.+ -. 0.01) and is continued for T base Time of +Δt (Δt takes a value of ±0.01s in this embodiment), followed by r of the initial air-fuel ratio signal at the time of non-rich or lean control Lean X (1+Δr) times, and for T base +Δt, and cycle N above signal characteristics 0 A cycle; wherein Deltar is coefficient judgment allowance, deltat is time judgment allowance;
2) The difference between the maximum value and the minimum value of the voltage signal of the oxygen sensor downstream of the catalyst does not exceed a set voltage threshold (20 mV in this embodiment);
if condition 1) is not satisfied, or condition 1) is satisfied but condition 2) is not satisfied, judging that the catalyst has a degradation fault, and stopping diagnosis, otherwise, continuing subsequent supplementary diagnosis.
Further, the supplementary diagnosis methods described in S3 are three in total, including a first supplementary diagnosis method, a second supplementary diagnosis method, and a third supplementary diagnosis method;
the selection rule of the supplementary diagnosis method is that if the first supplementary diagnosis method is adopted in the last driving cycle, the second supplementary diagnosis method is preferentially judged in the driving cycle, if the starting condition of the second supplementary diagnosis method is met, only the second supplementary diagnosis method is executed in the driving cycle, if the starting condition of the second supplementary diagnosis method is not met, but the starting condition of the third supplementary diagnosis method is met, only the third supplementary diagnosis method is executed in the driving cycle, and if the starting conditions of the second and third supplementary diagnosis methods are not met, only the first supplementary diagnosis method is executed in the driving cycle.
Further, the first supplementary diagnosis method is as follows,
let the air-fuel ratio control time be T base +T Delta (T in the first supplementary diagnosis method of the present embodiment) base Take the value of 0.08 s), at first at T base +T Delta Concentrating to original r in time Rich (r in the first supplementary diagnosis method of the present embodiment) Rich Take a value of 0.95) times, then at T base +T Delta Reducing the target air-fuel ratio to the original r in time Lean (r in the first supplementary diagnosis method of the present embodiment) Lean Take 1.05) times and the voltage fluctuation of the oxygen sensor circulating downstream of the catalyst stabilizes within a certain amplitude range (the amplitude range limit value is ±12mV in this embodiment); recording the voltage of an oxygen sensor downstream of the catalyst prior to the above cycleSignal, stabilized voltage signal V 0 Time T required for voltage rise 0 The method comprises the steps of carrying out a first treatment on the surface of the If T 0 ≥T 0Limit The supplementary diagnosis result is that the catalyst has a degradation fault, otherwise, the catalyst has no degradation fault;
wherein T0Limit The time limit value required for the voltage rise is calculated specifically as follows,
Figure BDA0003708575220000101
wherein ,TC For the base time, the catalyst in the deterioration critical limit state had an engine speed n of 3000rpm, a fresh air intake density rho of 800mgpl, and a catalyst temperature T Catalyst Time required for voltage rise of oxygen sensor at 850 ℃ downstream of the catalyst; f (n, rho) is a correction factor based on the current engine speed n, fresh air intake density rho,
Figure BDA0003708575220000102
based on the base temperature T of the catalyst CatalystBase and TCatalyst Is (are) correction factors>
Figure BDA0003708575220000103
The average value of the catalyst temperature obtained through the calibration of the engine bench from the time of target air-fuel ratio adjustment to the time of stabilizing the voltage fluctuation of the oxygen sensor at the downstream of the catalyst within a certain range; />
Figure BDA0003708575220000104
For the actual mileage Sigma L of the vehicle and the set basic mileage L of the engine Base The correction factor obtained (value is 200000km in the present embodiment);
wherein
Figure BDA0003708575220000105
And->
Figure BDA0003708575220000106
The calibration procedure of (2) is as follows, (-)>
Figure BDA0003708575220000107
When the diagnosis result of the first supplementary diagnosis method is that the catalyst has no degradation fault, T is measured in the process of the first supplementary diagnosis method 0 、V 0 According to the corresponding engine speed n, fresh air intake density rho
Figure BDA0003708575220000108
And storing.
Further, the second supplementary diagnostic method is started under the condition that if the current high-voltage battery SOC is greater than a threshold SOC Min (the value in the embodiment is 45%), and the steady-state working condition is satisfied, and then the starting condition of the second supplementary diagnosis method is satisfied;
the second supplementary diagnostic method is specifically as follows,
after the second supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the second supplementary diagnosis method, and otherwise, stopping the second supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M (value of the second supplementary diagnosis method of the present embodiment is-3%) to make the engine request the gas circuit torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching a target air-fuel ratio for a time period, at T base The target air-fuel ratio is thinned in time, and the target air-fuel ratio is periodically adjusted in this way until the voltage signal of the oxygen sensor downstream of the catalyst stabilizes within a preset range (the preset range is + -12 mV in the second supplementary diagnosis method of the present embodiment), and the voltage signal of the oxygen sensor downstream of the catalyst at the initial stage of the target air-fuel ratio adjustment, and the oxygen sensor downstream of the catalyst at the time of stabilization are recordedVoltage signal V of the device 1 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 1 ；
The V is set up above 1 、T 1 According to the corresponding engine speed n, fresh air intake density rho
Figure BDA0003708575220000111
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure BDA0003708575220000112
V under the working condition of (2) 0 、T 0 ；
If |V 1 -V 0 |＞ΔE V (ΔE in this embodiment) V The value is 12 mV), the result of the degradation diagnosis of the catalyst is not credible, and the diagnosis is finished; wherein ΔE V Is a preset voltage value;
if |V 1 -V 0 |≤ΔE V And T is 1 -T 0 ≥ΔT High1 Judging that the catalyst has a degradation fault;
if |V 1 -V 0 |≤ΔE V And DeltaT Low1 ＜T 1 -T 0 ＜ΔT High1 Judging that the catalyst has no degradation fault;
wherein ,
Figure BDA0003708575220000113
in the formula f1 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 1 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Engine requested gas circuit torque M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure BDA0003708575220000121
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta Ratio of (2)The correction factor obtained;
ΔT High1 each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure BDA0003708575220000122
ΔT Low1 the correction factors are obtained by calibrating the catalyst in the idle state.
Further, the third supplementary diagnostic method is started under the condition that if the current high-voltage battery SOC is less than a threshold SOC Max (the value in the embodiment is 85%), and the steady-state working condition is satisfied, and then the starting condition of the second supplementary diagnosis method is satisfied;
the third supplementary diagnostic method is specifically as follows,
after the third supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the third supplementary diagnosis method, and otherwise, stopping the third supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M (the value in the third supplementary diagnosis method of the present embodiment is 3%), so that the engine requests the gas circuit torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching a target air-fuel ratio for a time period, at T base The target air-fuel ratio is thinned in time, and the target air-fuel ratio is periodically regulated in this way until the voltage signal of the oxygen sensor downstream of the catalyst is stabilized within a preset range (the value of the third supplementary diagnosis method of the present embodiment is + -12 mV), and the voltage signal of the oxygen sensor downstream of the catalyst at the initial stage of the target air-fuel ratio regulation and the voltage signal V of the oxygen sensor downstream of the catalyst at the time of the stabilization are recorded 2 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 2 ；
The V is set up above 2 、T 2 According to their corresponding hairEngine speed n, fresh air intake density rho
Figure BDA0003708575220000123
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure BDA0003708575220000124
V under the working condition of (2) 0 、T 0 ；
If |V 2 -V 0 |＞ΔE V Judging that the catalyst degradation diagnosis result is not reliable, and ending the diagnosis; wherein ΔE V Is a preset voltage value;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≥ΔT High2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≤ΔT Low2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V ，ΔT Lo ＜T 0 -T 2 ＜ΔT High2 Judging that the catalyst has no degradation fault;
wherein ,
Figure BDA0003708575220000131
in the formula f3 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 3 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Engine requested gas circuit torque M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure BDA0003708575220000132
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta A correction factor obtained from the ratio of (2);
ΔT Hig each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure BDA0003708575220000133
ΔT Low1 the correction factors are obtained by calibrating the catalyst in the idle state.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present invention.

Claims (10)

1. A method for diagnosing degradation of a catalyst of an engine of a hybrid vehicle is characterized by comprising the following steps: comprises the steps of,
s1, judging whether the engine is currently under a steady-state working condition, if so, continuing the diagnosis step, otherwise, stopping the diagnosis;
s2, periodically enriching and reducing the target air-fuel ratio, and repeating for a plurality of periods; judging whether the catalyst has a degradation fault or not according to the air-fuel ratio signal of the oxygen sensor at the upstream of the catalyst and the voltage signal of the oxygen sensor at the downstream of the catalyst, if the catalyst has the degradation fault, stopping diagnosis, otherwise, performing subsequent supplementary diagnosis;
s3, presetting a plurality of different supplementary diagnosis methods for supplementary diagnosis, respectively judging whether each supplementary diagnosis method meets corresponding starting conditions according to a certain rule, and selecting one of the diagnosis methods meeting the starting conditions for supplementary diagnosis.
2. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 1, characterized in that: s1, judging that an engine is under a steady-state working condition only when all the following conditions are met;
1) The fluctuation of the engine speed is maintained in a preset fluctuation range, and the duration exceeds T1;
2) The fluctuation of the density of fresh air charge of the engine is maintained in a preset range, and the duration exceeds T2;
3) The fluctuation of the water temperature of the engine is maintained in a preset range, and the duration exceeds T3;
4) The atmospheric pressure continues unchanged and the duration exceeds T4;
5) The actual ignition efficiency fluctuation of the engine is maintained in a preset range and the duration exceeds T5
6) The target air-fuel ratio is the current stoichiometric air-fuel ratio;
7) The air-fuel ratio control is continuously in a closed-loop activation state, and the duration exceeds T6;
8) The temperature of the catalyst is within a preset range;
9) The difference between the engine requested road torque and the actual road torque is maintained within a preset range and the duration exceeds T7.
3. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 2, characterized in that: t1=t2=t3=t5=t6=t7, and the value range is 19 to 21s, and the value range of T4 is 55 to 65s; the preset range of the fluctuation of the engine speed is +/-20 rpm, the preset range of the fluctuation of the fresh air intake density of the engine is +/-5 mgpl, the preset range of the fluctuation of the engine water temperature is +/-2 ℃, the preset range of the fluctuation of the actual ignition efficiency of the engine is +/-0.08, the preset range of the temperature of the catalyst is 400-950 ℃, and the preset range of the difference value between the engine request road torque and the actual road torque is +/-3 Nm.
4. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 1, characterized in that: the basic diagnostic method of S2 is specifically as follows,
let the air-fuel ratio control time be T base The method comprises the steps of carrying out a first treatment on the surface of the First at T base Enriching the target air-fuel ratio to the original r in time Ric Multiple times, then at T vase Reducing the target air-fuel ratio to the original r in time Lean Doubling and circulating N 0 A cycle; wherein r is Ric 、r Lean Respectively isAn enrichment coefficient and a thinning coefficient; then, a judgment is made that,
1) The air-fuel ratio signal of the oxygen sensor upstream of the catalyst exhibits the following characteristics,
first, r is the initial air-fuel ratio signal when the control is not being enriched or lean Ric X (1+Δr) times, and for T base Time of +Δt, followed by r of the initial air-fuel ratio signal at the time of non-rich or lean control Lean X (1+Δr) times, and for T base +Δt, and cycle N above signal characteristics 0 A cycle; wherein Deltar is coefficient judgment allowance, deltat is time judgment allowance;
2) The difference between the maximum value and the minimum value of the voltage signal of the oxygen sensor at the downstream of the catalyst does not exceed a set voltage threshold;
if condition 1) is not satisfied, or condition 1) is satisfied but condition 2) is not satisfied, judging that the catalyst has a degradation fault, and stopping diagnosis, otherwise, continuing subsequent supplementary diagnosis.
5. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 4, characterized in that: t (T) base The value range is 0.04 to 0.06s, r Rich The value range is 0.94-0.96, r Lean The value range is 1.04-1.06, deltar= + -0.01, deltat value range is 0.005-0.015 s, N 0 The value range is 8-12, and the voltage threshold value in the condition 2) is 15-25 mV.
6. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 2, characterized in that: the supplementary diagnosis methods described in S3 are three in total, and include a first supplementary diagnosis method, a second supplementary diagnosis method, and a third supplementary diagnosis method;
the selection rule of the supplementary diagnosis method is that if the first supplementary diagnosis method is adopted in the last driving cycle, the second supplementary diagnosis method is preferentially judged in the driving cycle, if the starting condition of the second supplementary diagnosis method is met, only the second supplementary diagnosis method is executed in the driving cycle, if the starting condition of the second supplementary diagnosis method is not met, but the starting condition of the third supplementary diagnosis method is met, only the third supplementary diagnosis method is executed in the driving cycle, and if the starting conditions of the second and third supplementary diagnosis methods are not met, only the first supplementary diagnosis method is executed in the driving cycle.
7. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 6, characterized in that: the first supplementary diagnostic method is as follows,
let the air-fuel ratio control time be T base +T Delta First at T base +T Delta Concentrating to original r in time Rich Multiple times, then at T base +T Delta Reducing the target air-fuel ratio to the original r in time Lean The voltage fluctuation of the oxygen sensor which is multiplied and circulated to the downstream of the catalyst is stabilized within a certain amplitude range; recording the voltage signal of the oxygen sensor downstream of the catalyst before the cycle, the stabilized voltage signal V 0 Time T required for voltage rise 0 The method comprises the steps of carrying out a first treatment on the surface of the If T 0 ≥T 0Limit The supplementary diagnosis result is that the catalyst has a degradation fault, otherwise, the catalyst has no degradation fault;
wherein T0Limi The time limit value required for the voltage rise is calculated specifically as follows,
Figure FDA0003708575210000031
wherein ,TC For the base time, which is the engine speed n, the fresh air intake density rho and the catalyst temperature T of the catalyst in the deterioration critical limit state Catalyst The time required for the voltage of the oxygen sensor at the downstream of the catalyst under the working condition to rise; f (n, rho) is a correction factor based on the current engine speed n, fresh air intake density rho,
Figure FDA0003708575210000032
based on the base temperature T of the catalyst CatalystBase and TCatalyst Is (are) correction factors>
Figure FDA0003708575210000033
The average value of the catalyst temperature obtained through the calibration of the engine bench from the time of target air-fuel ratio adjustment to the time of stabilizing the voltage fluctuation of the oxygen sensor at the downstream of the catalyst within a certain range; />
Figure FDA0003708575210000034
For the actual mileage Sigma L of the vehicle and the set basic mileage L of the engine Base The correction factor obtained;
when the diagnosis result of the first supplementary diagnosis method is that the catalyst has no degradation fault, T is measured in the process of the first supplementary diagnosis method 0 、V 0 According to the corresponding engine speed n, fresh air intake density rho
Figure FDA0003708575210000041
And storing.
8. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 7, characterized in that: the second supplementary diagnosis method is started under the condition that if the current high-voltage battery SOC is greater than a threshold value SOC Min And meeting the steady-state working condition, and meeting the starting condition of the second supplementary diagnosis method;
the second supplementary diagnostic method is specifically as follows,
after the second supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the second supplementary diagnosis method, and otherwise, stopping the second supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M To make the engine request the air path torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching in timeTarget air-fuel ratio, at T base Reducing the target air-fuel ratio in time, and periodically adjusting the target air-fuel ratio until the voltage signal of the oxygen sensor downstream of the catalyst is stabilized within a preset range, and recording the voltage signal of the oxygen sensor downstream of the catalyst at the initial stage of the target air-fuel ratio adjustment and the voltage signal V of the oxygen sensor downstream of the catalyst at the time of stabilization 1 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 1 ；
The V is set up above 1 、T 1 According to the corresponding engine speed n, fresh air intake density rho
Figure FDA0003708575210000042
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure FDA0003708575210000043
V under the working condition of (2) 0 、T 0 ；
If |V 1 -V 0 |>ΔE V Judging that the catalyst degradation diagnosis result is not reliable, and ending the diagnosis; wherein ΔE V Is a preset voltage value;
if |V 1 -V 0 |≤ΔE V And T is 1 -T 0 ≥ΔT High1 Judging that the catalyst has a degradation fault;
if |V 1 -V 0 |≤ΔE V And DeltaT Low1 <T 1 -T 0 <ΔT High1 Judging that the catalyst has no degradation fault;
wherein ,
Figure FDA0003708575210000051
in the formula f1 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 1 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Air circuit torsion of engine requestMoment M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure FDA0003708575210000052
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta A correction factor obtained from the ratio of (2);
ΔT High1 each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure FDA0003708575210000053
ΔT Lo the correction factors are obtained by calibrating the catalyst in the idle state.
9. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 7, characterized in that: the third supplementary diagnosis method is started under the condition that if the current high-voltage battery SOC is smaller than a threshold value SOC Max And meeting the steady-state working condition, and meeting the starting condition of the second supplementary diagnosis method;
the third supplementary diagnostic method is specifically as follows,
after the third supplementary diagnosis method is started, if the steady-state working condition judgment conditions except the fresh air intake density condition of the engine are met, continuing the third supplementary diagnosis method, and otherwise, stopping the third supplementary diagnosis method;
first, the fresh air intake density rho of the engine is obtained, and then the coefficient Deltar is reduced according to the output torque of the engine M To make the engine request the air path torque M EngineAirAct Reducing Deltar M ×M EngineAirAct The method comprises the steps of carrying out a first treatment on the surface of the Then at T base +T Delta Enriching a target air-fuel ratio for a time period, at T base Reducing the target air-fuel ratio in time, and periodically adjusting the target air-fuel ratio in such a way that the voltage signal of the oxygen sensor downstream of the catalyst is stabilized within a preset range, and recording the downstream of the catalyst at the initial stage of the target air-fuel ratio adjustmentVoltage signal of oxygen sensor, voltage signal V of oxygen sensor downstream of catalyst when stabilized 2 And the time T required for the voltage signal of the oxygen sensor downstream of the catalyst to rise 2 ；
The V is set up above 2 、T 2 According to the corresponding engine speed n, fresh air intake density rho
Figure FDA0003708575210000061
Stores and reads the same engine speed n, fresh air intake density rho +.>
Figure FDA0003708575210000062
V under the working condition of (2) 0 、T 0 ；
If |V 2 -V 0 |>ΔE V Judging that the catalyst degradation diagnosis result is not reliable, and ending the diagnosis; wherein ΔE V Is a preset voltage value;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≥ΔT High2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V And T is 0 -T 2 ≤ΔT Low2 Judging that the catalyst has a degradation fault;
if |V 2 -V 0 |≤ΔE V ，ΔT Low2 <T 0 -T 2 <ΔT High2 Judging that the catalyst has no degradation fault;
wherein ,
Figure FDA0003708575210000063
in the formula f3 (n, rho) is a correction factor, k, obtained from the engine speed n and the fresh air intake density rho 3 (Δr M ×M EngineAirAct N) is a coefficient Δr according to the engine output torque M Engine requested gas circuit torque M EngineAirAct And the correction factor derived from the engine speed n, < +.>
Figure FDA0003708575210000064
To control the base time T according to the air-fuel ratio base And air-fuel ratio control deviation time T Delta A correction factor obtained from the ratio of (2);
ΔT High2 each correction factor is obtained by calibrating a catalyst in a degradation critical limit state;
wherein ,
Figure FDA0003708575210000065
ΔT Low1 the correction factors are obtained by calibrating the catalyst in the idle state.
10. The hybrid vehicle type engine catalyst degradation diagnosis method according to claim 8 or 9, characterized in that: ΔE V The value range is 11-13 mV.
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