WO2013157048A1 - Dispositif de diagnostic d'anomalies de catalyseur - Google Patents

Dispositif de diagnostic d'anomalies de catalyseur Download PDF

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Publication number
WO2013157048A1
WO2013157048A1 PCT/JP2012/002754 JP2012002754W WO2013157048A1 WO 2013157048 A1 WO2013157048 A1 WO 2013157048A1 JP 2012002754 W JP2012002754 W JP 2012002754W WO 2013157048 A1 WO2013157048 A1 WO 2013157048A1
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Prior art keywords
catalyst
fuel ratio
air
rich
determination value
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PCT/JP2012/002754
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English (en)
Japanese (ja)
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北浦　浩一
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トヨタ自動車株式会社
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Priority to PCT/JP2012/002754 priority Critical patent/WO2013157048A1/fr
Publication of WO2013157048A1 publication Critical patent/WO2013157048A1/fr

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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
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D41/1408—Dithering techniques
    • 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
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
    • F02D41/1441—Plural sensors
    • 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
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • 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
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/02—Catalytic activity 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
    • F02D41/22—Safety or indicating devices for abnormal conditions

Definitions

  • the present invention relates to an abnormality diagnosis of a catalyst, and more particularly to an apparatus for diagnosing an abnormality of a catalyst disposed in an exhaust passage of an internal combustion engine.
  • a catalyst for purifying exhaust gas is installed in the exhaust system.
  • Some of these catalysts have an oxygen storage capacity (O 2 storage capacity).
  • O 2 storage capacity oxygen storage capacity
  • the air-fuel ratio of the exhaust gas flowing into the catalyst becomes larger than the stoichiometric air-fuel ratio (stoichiometric), that is, when the engine becomes lean
  • the catalyst having oxygen storage capacity occludes excess oxygen present in the exhaust gas.
  • the fuel ratio becomes smaller than stoichiometric, that is, when it becomes rich, the stored oxygen is released.
  • air-fuel ratio control is performed so that the exhaust gas flowing into the catalyst is in the vicinity of the stoichiometric.
  • a post-catalyst sensor for detecting the exhaust air / fuel ratio downstream of the catalyst is provided, and at the same time as the output of the post-catalyst sensor is reversed, the lean control and the rich control are switched, and the measurement of the oxygen amount is finished. I am doing so.
  • one object of the present invention is to provide a catalyst abnormality diagnosis device that can reduce measurement errors, improve diagnosis accuracy, and suppress erroneous diagnosis. is there.
  • An apparatus for diagnosing abnormality of a catalyst disposed in an exhaust passage of an internal combustion engine This is a post-catalyst sensor that detects the exhaust air / fuel ratio downstream of the catalyst, and the output changes suddenly at the stoichiometric boundary, and when the exhaust air / fuel ratio changes from the rich side to the lean side with respect to the stoichiometry, and changes from the lean side to the rich side
  • a post-catalyst sensor having a hysteresis characteristic in which the output characteristic near the stoichiometry differs depending on Active air-fuel ratio control for executing active air-fuel ratio control for switching the air-fuel ratio upstream of the catalyst from one of the lean air-fuel ratio and the rich air-fuel ratio in synchronization with the output of the post-catalyst sensor reaching a predetermined determination value
  • the determination value includes a lean determination value that defines the switching timing from the lean air-fuel ratio to the rich air-fuel ratio, and a rich determination value that defines the switching timing from the rich air-fuel ratio to the lean air-fuel ratio,
  • the measuring means is configured so that the output of the post-catalyst sensor reaches the lean side from the predetermined stoichiometric determination value before reaching the lean determination value.
  • the integrated measurement of the oxygen amount is terminated.
  • the stoichiometric determination value is a value corresponding to stoichiometry on a hysteresis characteristic line when the post-catalyst sensor output changes from the rich side to the lean side.
  • the stoichiometric determination value may be a richer value than the rich determination value.
  • the stoichiometric determination value may be a value equal to the rich determination value.
  • the stoichiometric determination value may be a value leaner than the rich determination value, and may be a richer value than a stoichiometric equivalent value on a single characteristic line of the post-catalyst sensor output.
  • the determination value includes a lean determination value that defines the switching timing from the lean air-fuel ratio to the rich air-fuel ratio, and a rich determination value that defines the switching timing from the rich air-fuel ratio to the lean air-fuel ratio,
  • the measurement means is configured to output the post-catalyst sensor before reaching the rich determination value and from the predetermined stoichiometric determination value toward the rich side.
  • the integrated measurement of the oxygen amount is terminated.
  • the stoichiometric rich determination value is a value corresponding to the stoichiometric value on the hysteresis characteristic line when the post-catalyst sensor output changes from the lean side to the rich side.
  • the stoichiometric determination value may be a leaner value than the lean determination value.
  • the stoichiometric determination value may be a value equal to the lean determination value.
  • the stoichiometric determination value may be a value on the rich side with respect to the lean determination value, and may be a value on the lean side with respect to a stoichiometric equivalent value on a single characteristic line of the post-catalyst sensor output.
  • the active air-fuel ratio control means changes the determination value according to the intake air amount.
  • the active air-fuel ratio control means switches the air-fuel ratio after a predetermined delay time has elapsed since the output of the post-catalyst sensor reaches the determination value, and changes the delay time according to the intake air amount.
  • the figure which added the example which changed the sulfur concentration of a fuel and the oxygen storage capacity measuring method to the example of FIG. 9 is shown.
  • It is a figure for demonstrating a delay process It is a figure which shows the relationship between FIG. 15A and FIG. 15B.
  • the map for calculating delay time is shown.
  • FIG. 1 is a schematic diagram showing the configuration of the present embodiment.
  • an engine 1 that is an internal combustion engine burns a mixture of fuel and air in a combustion chamber 3 formed in a cylinder block 2 and reciprocates a piston 4 in the combustion chamber 3 to drive power. Is generated.
  • the engine 1 of the present embodiment is a multi-cylinder engine for automobiles (only one cylinder is shown), and is a spark ignition type internal combustion engine, more specifically, a gasoline engine.
  • the cylinder head of the engine 1 is provided with an intake valve Vi for opening and closing the intake port and an exhaust valve Ve for opening and closing the exhaust port for each cylinder.
  • Each intake valve Vi and each exhaust valve Ve are opened and closed by a camshaft (not shown).
  • a spark plug 7 for igniting the air-fuel mixture in the combustion chamber 3 is attached to the top of the cylinder head for each cylinder.
  • the intake port of each cylinder is connected to a surge tank 8 which is an intake manifold through an intake manifold.
  • An intake pipe 13 that forms an intake manifold passage is connected to the upstream side of the surge tank 8, and an air cleaner 9 is provided at the upstream end of the intake pipe 13.
  • the intake pipe 13 includes an air flow meter 5 for detecting an air amount per unit time flowing into the engine, that is, an intake air amount Ga (g / s), and an electronically controlled throttle valve 10 in order from the upstream side. Is provided.
  • An intake passage is formed by the intake port, the intake manifold, the surge tank 8 and the intake pipe 13.
  • An injector for injecting fuel into the intake passage, particularly the intake port, that is, a fuel injection valve 12 is provided for each cylinder.
  • the fuel injected from the injector 12 is mixed with intake air to form an air-fuel mixture.
  • the air-fuel mixture is sucked into the combustion chamber 3 when the intake valve Vi is opened, compressed by the piston 4, and ignited and burned by the spark plug 7. It is done.
  • the exhaust port of each cylinder is connected to an exhaust pipe 6 forming an exhaust collecting passage through an exhaust manifold.
  • An exhaust passage is formed by the exhaust port, the exhaust manifold, and the exhaust pipe 6.
  • the exhaust pipe 6 is provided with a catalyst composed of a three-way catalyst having oxygen storage capacity, that is, an upstream catalyst 11 and a downstream catalyst 19 in series on the upstream side and the downstream side.
  • the upstream catalyst 11 is disposed immediately after the exhaust manifold, and the downstream catalyst 19 is disposed under the floor of the vehicle.
  • the pre-catalyst sensor 17 is composed of a wide-range air-fuel ratio sensor, can continuously detect the air-fuel ratio over a relatively wide range, and outputs a signal having a value proportional to the air-fuel ratio.
  • the post-catalyst sensor 18 is composed of an oxygen sensor (O 2 sensor) and has a characteristic (Z characteristic) in which the output value changes suddenly with the theoretical air-fuel ratio as a boundary.
  • the above-described spark plug 7, throttle valve 10, injector 12 and the like are electrically connected to an electronic control unit (hereinafter referred to as ECU) 20 as control means.
  • the ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown.
  • the ECU 20 includes a crank angle sensor 14 that detects the crank angle of the engine 1, and an accelerator opening that detects the accelerator opening, as shown in the figure.
  • the degree sensor 15 and other various sensors are electrically connected via an A / D converter or the like (not shown).
  • the ECU 20 controls the ignition plug 7, the injector 12, the throttle valve 10, etc. so as to obtain a desired output based on the detection values of various sensors, etc., and the ignition timing, fuel injection amount, fuel injection timing, throttle opening. Control the degree etc.
  • the downstream catalyst 19 is configured in the same manner as the upstream catalyst 11.
  • a coating material 31 is coated on the surface of a carrier base material (not shown), and a large number of particulate catalyst components 32 are supported on the coating material 31 in a dispersed manner.
  • the catalyst 11 is exposed inside.
  • the catalyst component 32 is mainly composed of a noble metal such as Pt or Pd, and serves as an active point when reacting exhaust gas components such as NOx, HC and CO.
  • the coating material 31 plays a role of a promoter that promotes a reaction at the interface between the exhaust gas and the catalyst component 32 and includes an oxygen storage component capable of absorbing and releasing oxygen according to the air-fuel ratio of the atmospheric gas.
  • the oxygen storage component is made of, for example, cerium dioxide CeO 2 or zirconia. Note that “absorption” or “adsorption” may be used in the same meaning as “occlusion”.
  • the oxygen storage component present around the catalyst component 32 absorbs oxygen from the atmospheric gas, and as a result, NOx is reduced and purified.
  • the atmospheric gas in the catalyst is richer than the stoichiometric air-fuel ratio, oxygen stored in the oxygen storage component is released, and the released oxygen oxidizes and purifies HC and CO.
  • This oxygen absorption / release action can absorb this variation even if the actual air-fuel ratio varies somewhat with respect to stoichiometry during normal stoichiometric air-fuel ratio control.
  • the new catalyst 11 As described above, a large number of catalyst components 32 are evenly distributed, and the contact probability between the exhaust gas and the catalyst component 32 is kept high. However, when the catalyst 11 deteriorates, some of the catalyst components 32 are lost, and some of the catalyst components 32 are baked and solidified by exhaust heat (see broken lines in the figure). If it becomes like this, the contact probability of exhaust gas and the catalyst component 32 will fall, and it will become the cause of reducing a purification rate. In addition to this, the amount of the coating material 31 existing around the catalyst component 32, that is, the amount of the oxygen storage component decreases, and the oxygen storage capacity itself decreases.
  • the deterioration degree of the upstream catalyst 11 is detected by detecting the oxygen storage capacity of the upstream catalyst 11 that has a particularly large influence on the emission, and the abnormality of the upstream catalyst 11 is diagnosed.
  • the oxygen storage capacity of the catalyst 11 is represented by the amount of oxygen storage capacity (OSC; O 2 Storage Capacity, unit is g), which is the amount of oxygen that the current catalyst 11 can store or release.
  • the abnormality diagnosis of this embodiment is based on the following method based on the Cmax method described above.
  • the active air-fuel ratio control is executed by the ECU 20. That is, the ECU 20 controls the air-fuel ratio on the upstream side of the catalyst, specifically, the air-fuel ratio of the air-fuel mixture in the combustion chamber 3 alternately and richly and lean, with the stoichiometric A / Fs being the central air-fuel ratio as a boundary.
  • the air-fuel ratio of the exhaust gas supplied to the catalyst 11 is also controlled to be rich and lean alternately.
  • active air-fuel ratio control and diagnosis are executed only when predetermined preconditions are satisfied. This precondition will be described later.
  • the broken line indicates the target air-fuel ratio A / Ft
  • the solid line indicates the output of the pre-catalyst sensor 17 (however, the converted value to the pre-catalyst air-fuel ratio A / Ff).
  • the solid line indicates the output of the post-catalyst sensor 18 (however, the output voltage Vr).
  • the target air-fuel ratio A / Ft is set to a predetermined lean air-fuel ratio A / Fl (for example, 15.1), and the catalyst 11 is supplied with a lean gas having an air-fuel ratio equal to the target air-fuel ratio A / Ft.
  • the catalyst 11 continues to occlude oxygen. However, when the oxygen is occluded until it is saturated, that is, full, it can no longer occlude oxygen. As a result, the lean gas passes through the catalyst 11 and flows out downstream of the catalyst 11.
  • the output of the post-catalyst sensor 18 changes to the lean side, and the target air-fuel ratio A / Ft becomes the predetermined rich air-fuel ratio at the time t1 when the output voltage Vr reaches a predetermined lean determination value VL (for example, 0.2 V). It is switched to A / Fr (for example, 14.1). As a result, the air-fuel ratio control is switched from lean control to rich control, and rich gas having an air-fuel ratio equal to the target air-fuel ratio A / Ft is supplied.
  • VL for example, 0.2 V
  • the catalyst 11 When the rich gas is supplied, the catalyst 11 continues to release the stored oxygen. When the stored oxygen is eventually released from the catalyst 11, the catalyst 11 cannot release oxygen at that time, and the rich gas passes through the catalyst 11 and flows out downstream of the catalyst 11. When this happens, the output of the post-catalyst sensor 18 changes to the rich side, and at the time t2 when the output voltage Vr reaches a predetermined rich determination value VR (for example, 0.6 V), the target air-fuel ratio A / Ft becomes the lean air-fuel ratio A / It is switched to Fl. As a result, the air-fuel ratio control is switched from rich control to lean control, and a lean gas having an air-fuel ratio equal to the target air-fuel ratio A / Ft is supplied.
  • a predetermined rich determination value VR for example, 0.6 V
  • a set of adjacent lean control and rich control is defined as one cycle of active air-fuel ratio control.
  • Active air-fuel ratio control is executed in a predetermined N cycle (N is an integer of 2 or more).
  • the lean determination value VL defines the switching timing from lean control to rich control. As shown in FIG. 5, the lean determination value VL is set to a value smaller (lean side) than the stoichiometric equivalent value Vst of the post-catalyst sensor output.
  • the rich determination value VR defines the switching timing from rich control to lean control. As shown in FIG. 5, the rich determination value VR is set in advance to a value that is larger (rich side) than the stoichiometric equivalent value Vst of the post-catalyst sensor output.
  • the oxygen storage capacity OSC of the catalyst 11 is measured by the following method.
  • the oxygen storage capacity OSC is measured as follows. As shown in FIG. 4, immediately after the target air-fuel ratio A / Ft is switched to the rich air-fuel ratio A / Fr at time t1, the pre-catalyst air-fuel ratio A / Ff as an actual value is slightly delayed with the rich air-fuel ratio A / Ff. Switch to Fr. From the time t11 when the pre-catalyst air-fuel ratio A / Ff reaches the stoichiometric A / Fs to the time t2 when the post-catalyst sensor output Vr is next reversed, the oxygen storage capacity for each predetermined calculation cycle is obtained by the following equation (1).
  • the oxygen storage capacity OSC as the final integrated value during the rich control, that is, the amount of released oxygen indicated by OSCb in FIG. 4 is measured.
  • the oxygen storage capacity that is, the stored oxygen amount indicated by OSCa in FIG. 4 is measured.
  • the released oxygen amount and the stored oxygen amount are alternately measured.
  • the normality / abnormality determination of the catalyst is performed by the following method.
  • the ECU 20 calculates an average value OSCav of the measured values of the released oxygen amount and the stored oxygen amount.
  • the average value OSCav is compared with a predetermined abnormality determination value ⁇ .
  • the ECU 20 determines that the catalyst 11 is normal when the average value OSCav is greater than the abnormality determination value ⁇ , and determines that the catalyst 11 is abnormal when the average value OSCav is less than or equal to the abnormality determination value ⁇ .
  • a warning device not shown
  • a check lamp such as a check lamp
  • Oxygen storage capacity OSC and “oxygen amount” are terms that encompass “amount of stored oxygen OSCa” and “amount of released oxygen OSCb”.
  • FIG. 6 shows the case of a normal catalyst
  • FIG. 7 shows the case of an abnormal catalyst. Both figures show the test results when switching from lean control to rich control. However, even when the post-catalyst sensor output Vr is reversed (that is, even when the rich determination value VR is reached), switching to lean control is not performed.
  • (A) shows the target air-fuel ratio A / Ft, the pre-catalyst air-fuel ratio A / Ff (line a) detected by the pre-catalyst sensor 17, and the post-catalyst air-fuel ratio A / Fr (line b).
  • an air-fuel ratio sensor similar to the pre-catalyst sensor 17 is installed for testing on the downstream side of the catalyst, and the air-fuel ratio detected by the test air-fuel ratio sensor is set as the post-catalyst air-fuel ratio A / Fr.
  • (B) shows the post-catalyst sensor output Vr
  • (C) shows the integrated value of the released oxygen amount OSCb.
  • the post-catalyst sensor output Vr can vary within the range of 0 to 1 (V).
  • the rich determination value VR of the post-catalyst sensor output Vr is 0.6 (V).
  • the post-catalyst air-fuel ratio A / Fr is slightly richer than stoichiometric during this period t1 to t3.
  • the area of the region d sandwiched between the stoichiometry and the post-catalyst air-fuel ratio A / Fr is the portion of the rich gas that could not be actually processed by the catalyst, in other words, the amount of oxygen that could not be released from the catalyst (OSCe for convenience) Represents.
  • the area of the region d corresponds to an error in the total released oxygen amount OSCb at time t3.
  • the value obtained by subtracting the area (OSCe) of the region d from the area (OSCb) of the region c represents the amount of oxygen actually released from the catalyst.
  • the measured released oxygen amount OSCb includes the actually released oxygen amount OSCe.
  • the post-catalyst air-fuel ratio A / Fr starts to decrease to the rich side at time t2 between time t1 and time t3, and the post-catalyst sensor output
  • the rate of increase or change rate of Vr to the rich side has begun to increase. This is considered to mean that the release of oxygen from the catalyst is substantially completed at time t2, and thereafter oxygen remaining in the catalyst is released relatively slowly. Alternatively, it is considered that the main oxygen release of the catalyst is completed at the time t2, and then the secondary residual oxygen is released.
  • (C) schematically shows the amount of oxygen OSCe corresponding to the error.
  • the proportion of the oxygen amount OSCe corresponding to the error is relatively small.
  • the ratio of the error is very large in the released oxygen amount OSCb measured in the period t2 to t3.
  • the error amount in the period t2 to t3 accounts for a large proportion of the total released oxygen amount. it is conceivable that.
  • (C) schematically shows the amount of oxygen OSCe corresponding to the error.
  • the proportion of the oxygen amount OSCe corresponding to the error is large.
  • the error rate immediately before reversing the sensor output after the catalyst increases compared to the case of a normal catalyst, and the increase rate of the measured value relative to the true value also increases.
  • an abnormal catalyst is actually misdiagnosed as normal.
  • the difference in the measured oxygen amount between the normal catalyst and the abnormal catalyst cannot be enlarged, and there is a possibility that sufficient diagnostic accuracy cannot be ensured particularly in the case of a catalyst where these differences are originally small.
  • the post-catalyst sensor 18 has a cup-shaped detection element 31 disposed in the exhaust pipe 6, and the detection element 31 is covered with a cover 32 with a hole.
  • An inner surface or inner electrode (not shown) of the detection element 31 is exposed to the atmosphere (air), and an outer surface or outer electrode of the detection element 31 is exposed in the cover 32.
  • Exhaust gas outside the cover 32 enters the cover 32 through the hole 33 of the cover 32.
  • the difference in oxygen partial pressure between the inner and outer surfaces of the detection element 31 in other words, the oxygen partial pressure between the atmospheric gas that is the atmospheric gas on the inner surface of the detection element 31 and the exhaust gas that is the atmospheric gas on the outer surface of the detection element 31.
  • An electromotive force is generated according to the difference. Based on this electromotive force, the air-fuel ratio of the exhaust gas is detected. The smaller the oxygen concentration of the exhaust gas, that is, the richer the air-fuel ratio of the exhaust gas, the larger the electromotive force.
  • the post-catalyst sensor 18 generates an electromotive force according to the air-fuel ratio of the ambient gas outside the detection element 31, and rather, passively generates an output corresponding to the air-fuel ratio of the ambient gas. . Therefore, even if the ambient gas outside the cover 32 changes to rich gas, the rich gas enters the cover 32 and is exchanged with the existing gas in the cover 32, and the post-catalyst sensor 18 generates an electromotive force corresponding to the rich gas in the cover. There is a time delay before it occurs.
  • This delay is a response delay, and this response delay is much larger than the response delay of the pre-catalyst sensor 17 composed of the wide-range air-fuel ratio sensor and the test air-fuel ratio sensor installed on the downstream side of the catalyst. This is because the pre-catalyst sensor 17 and the test air-fuel ratio sensor are applied with a predetermined voltage and rather can actively generate an output corresponding to the air-fuel ratio of the atmospheric gas.
  • one of the causes of the above problem is that the post-catalyst sensor 18 has a hysteresis characteristic.
  • the post-catalyst sensor 18 has a single characteristic as indicated by a solid line qualitatively or statically, but has a hysteresis characteristic as indicated by a one-dot chain line in practice or dynamically.
  • the exhaust air-fuel ratio changes from the rich side to the lean side with respect to the stoichiometry (line a)
  • the exhaust air-fuel ratio changes from the lean side to the rich side (line b)
  • the output characteristics or transient characteristics near the stoichiometry are different.
  • This hysteresis characteristic also causes a response delay of the post-catalyst sensor output Vr, resulting in a measurement error.
  • the post-catalyst sensor output Vr diagram does not match the post-catalyst air-fuel ratio A / Fr diagram (line b) in the examples of FIGS.
  • FIGS. 6 and 7 are the case of rich control, but the same problem occurs in the case of lean control.
  • the oxygen amount measurement method is changed as follows.
  • the output of the post-catalyst sensor 18 indicates that the exhaust air-fuel ratio on the downstream side of the catalyst moves from the stoichiometric direction toward the one.
  • the integrated measurement of the oxygen amount is terminated.
  • the air-fuel ratio switching timing of the active air-fuel ratio control is not changed, the oxygen amount measurement end timing is changed, and the integrated measurement of the oxygen amount is ended at a timing earlier than the air-fuel ratio switching timing.
  • the integration of the oxygen amount can be completed at the moment when the one gas starts to leak from the catalyst, and only the substantial oxygen amount occluded or released can be measured.
  • the subsequent measurement of the error during the response delay time of the post-catalyst sensor 18 can be eliminated, and the measurement error due to the response delay of the post-catalyst sensor 18 can be greatly reduced.
  • the measurement error can be reduced to improve the diagnostic accuracy, and misdiagnosis can be suppressed.
  • the difference of the measured value between right and wrong catalysts is expanded substantially, and even if the difference of both originally is delicate, it becomes possible to distinguish the difference correctly.
  • (A) shows the pre-catalyst air-fuel ratio A / Ff and target air-fuel ratio A / Ft detected by the pre-catalyst sensor 17, and (B) shows the post-catalyst sensor output Vr.
  • (C) shows the post-catalyst air-fuel ratio A / Fr detected by the test air-fuel ratio sensor for convenience, and (D) shows the integrated value of the stored oxygen amount OSCa.
  • test air-fuel ratio sensor is much more responsive than the post-catalyst sensor 18. Therefore, the post-catalyst air-fuel ratio A / Fr shown in (C) can be considered to accurately indicate the exhaust air-fuel ratio downstream of the catalyst.
  • the target air-fuel ratio A / Ft is switched to the rich air-fuel ratio at the time t5 when the post-catalyst sensor output Vr further changes to the lean side and reaches the lean determination value VL, and rich control is started.
  • VL 0.2 (V).
  • the air-fuel ratio switching timing is the same as in the basic method, and the integration end timing is earlier than the air-fuel ratio switching timing.
  • the post-catalyst air-fuel ratio A / Fr approaches the stoichiometry during the period from t2 to t3, and is maintained substantially stoichiometric during the period from t3 to t4. It has a waveform with a certain shelf in the middle, which approaches the lean air-fuel ratio in the period of t5.
  • the post-catalyst sensor output Vr in (B) also has a waveform similar to this.
  • the stoichiometric determination value VA is set in accordance with the timing when the leakage starts. That is, the timing at which the post-catalyst sensor output Vr first falls below the stoichiometric determination value VA means the timing at which substantial oxygen occlusion has ended in the catalyst and oxygen begins to leak.
  • the rich determination value VR and the lean determination value VL, and the stoichiometric determination value VA and the stoichiometric rich determination value VB are all adapted values set in advance in consideration of the test results, sensor characteristics, and the like. is there.
  • the lean determination value VL is a value indicating that the post-catalyst air-fuel ratio A / Fr is completely leaner than the stoichiometric value
  • the stoichiometric determination value VA is equal to the post-catalyst air-fuel ratio A / Fr. This value indicates that the stoichi has started to become lean.
  • the rich determination value VR is a value indicating that the post-catalyst air-fuel ratio A / Fr is completely richer than the stoichiometric ratio
  • the stoichiometric rich determination value VB is the post-catalyst air-fuel ratio A / Fr. Is a value indicating that has started to become rich from stoichiometric.
  • the stoichiometric determination value VA is a value close to the rich determination value VR.
  • the stoichiometric determination value VB is a value close to the lean determination value VL.
  • stoichiometric determination value VA is most preferably value VA 1 corresponding to stoichiometry on hysteresis characteristic line a when changing from the rich side to the lean side.
  • the value VA 1 is a value on the rich side with respect to the rich determination value VR.
  • the output characteristics and hysteresis characteristics of the post-catalyst sensor 18 differ depending on the sensor, and may not be as shown in the example of illustration. Further, the above value may not necessarily be a value indicating that the post-catalyst air-fuel ratio A / Fr starts to change from stoichiometric to lean.
  • the stoichiometric determination value VA may alternatively be a value VA 2 equal to the rich determination value VR, or stoichiometrically on the single characteristic line (solid line) on the lean side with respect to the rich determination value VR.
  • the value VA 3 on the richer side than the equivalent value Vst may be used.
  • VA 0.6 (V).
  • VR ⁇ VA in terms of control. This is because if VR ⁇ VA, the post-catalyst sensor output Vr that has increased to the rich side and exceeded the rich determination value VR may decrease before reaching VA.
  • the same measurement method is adopted when the air-fuel ratio is controlled to the opposite side, that is, the rich air-fuel ratio. That is, as shown in FIG. 9, during the rich control before time t2, while the after-catalyst sensor output Vr is changing to the rich side, the after-catalyst sensor output Vr first reaches the predetermined stoichiometric determination value VB. At the time t1 when the value exceeds, the integrated measurement of the released oxygen amount OSCb is completed.
  • the target air-fuel ratio A / Ft is switched to the lean air-fuel ratio, and lean control is started.
  • the post-catalyst air-fuel ratio A / Fr is almost stoichiometric before time t1, but starts to change toward the rich air-fuel ratio at time t1. It is considered that at this time t1, the processing of the rich gas by the oxygen released from the catalyst is not in time, and part of the rich gas has started to leak from the catalyst.
  • the stoichiometric determination value VB is set in accordance with the timing when the leakage starts. That is, the timing at which the post-catalyst sensor output Vr first exceeds the stoichiometric rich determination value VB means the timing at which the substantial oxygen release has ended in the catalyst and the rich gas has started to leak.
  • stoichiometric rich determination value VB is most preferably value VB 1 corresponding to stoichiometry on hysteresis characteristic line b when changing from the lean side to the rich side.
  • this value VB 1 is a value on the lean side of the lean determination value VL.
  • the output characteristics and hysteresis characteristics of the post-catalyst sensor 18 differ depending on the sensor, and may not be as shown in the example of illustration. Further, the above value may not necessarily be a value indicating the time point when the post-catalyst air-fuel ratio A / Fr starts to change from stoichiometric to rich.
  • the stoichiometric determination value VB may alternatively be a value VB 2 equal to the lean determination value VL, or stoichiometric on the rich characteristic side of the lean determination value VL and on a single characteristic line (solid line).
  • the value VB 3 on the lean side of the equivalent value Vst may be used.
  • VL ⁇ VB it may be preferable to satisfy VL ⁇ VB. This is because, if VL> VB, the post-catalyst sensor output Vr that has decreased to the lean side and exceeded the lean determination value VL may increase before reaching VB.
  • FIG. 10 shows a diagram in which an example in which the method for measuring the sulfur (S) concentration of fuel and the amount of oxygen is changed is added to the example of FIG.
  • the example of FIG. 9 is an example in the case of using a standard fuel having a low sulfur concentration and a predetermined value or less (hereinafter referred to as low S fuel). For this reason, the same diagram as FIG. 9 in FIG. 10 is displayed as “low S”, and the additional diagram is also displayed as “low S” when the low S fuel is used.
  • “high S” is displayed for a diagram in the case where a fuel having a high sulfur concentration and exceeding a predetermined value (hereinafter referred to as high S fuel) is used.
  • A1 is the stored oxygen amount measurement value when the integration is terminated at time t4 when the post-catalyst sensor output Vr first falls below the stoichiometric determination value VA according to the present embodiment when low S fuel is used.
  • A2 is the stored oxygen amount measurement value when the integration is terminated at time t5 when the post-catalyst sensor output Vr reaches the lean determination value VL according to the basic method when using low S fuel. Since the integration is completed at a later timing than in the present embodiment when low S fuel is used, the measured value increases (A1 ⁇ A2).
  • B1 is a measured value of the stored oxygen amount when the integration ends at time t6 when the post-catalyst sensor output Vr first falls below the stoichiometric determination value VA according to the present embodiment when high S fuel is used. Since the integration is completed at an earlier timing than in the present embodiment when using low S fuel, the measured value decreases (B1 ⁇ A1).
  • B2 is the measured value of the stored oxygen amount when the integration ends at time t7 when the post-catalyst sensor output Vr reaches the lean determination value VL according to the basic method when using high S fuel. Compared with the basic method when using low S fuel, the integration is completed at an earlier timing, so the measured value decreases (B2 ⁇ A2).
  • the difference between A1 and B1 in this embodiment is smaller than the difference between A2 and B2 in the basic method. Therefore, it can be said that the change or variation of the measured value with respect to the change or variation in the S concentration of the fuel is less in the present embodiment than in the basic method. Therefore, the present embodiment has an advantage that a relatively stable measurement value can be obtained without being easily influenced by the S concentration of the fuel.
  • This difference is due to the fact that the integration end timing of this embodiment is earlier than the integration end timing of the basic method. That is, as shown in (B), in the integration end timing of this embodiment, the difference in the integration end timing due to the difference in S concentration is a relatively short time between t6 and t4. On the other hand, at the integration end timing of the basic method, the difference in the integration end timing due to the difference in S concentration becomes a relatively long time between t7 and t5. The reason for this is that the rate of change of the post-catalyst sensor output Vr after the integration end timing of the present embodiment varies depending on the S concentration, and the later the difference in the post-catalyst sensor output Vr increases. Therefore, there is a large difference between the two timings at the integration end timing of the basic method, and a large difference also occurs in the measured values obtained as a result.
  • FIG. 11 is a diagram for illustrating the influence of the response variation of the post-catalyst sensor 18 on the measured value.
  • (A) shows the pre-catalyst air-fuel ratio A / Ff and post-catalyst air-fuel ratio A / Fr
  • (B) shows the integrated value of the stored oxygen amount OSCa
  • (C) shows the post-catalyst sensor output. Vr is shown.
  • the area of the portion I sandwiched between the pre-catalyst air-fuel ratio A / Ff and the post-catalyst air-fuel ratio A / Fr represents the true stored oxygen amount OSCa of the catalyst.
  • the area of the portion sandwiched between the pre-catalyst air-fuel ratio A / Ff and the stoichiometry represents the actually stored stored oxygen amount OSCa
  • a indicates the case of a post-catalyst sensor (hereinafter referred to as a reference sensor) whose response is an intermediate reference.
  • b shows the case of a post-catalyst sensor (hereinafter referred to as a high response sensor) whose response is faster than the reference sensor due to secular change
  • c is a catalyst whose response is slower than the reference sensor due to secular change.
  • the case of a rear sensor hereinafter referred to as a low response sensor
  • the integration end timing is over a relatively long period from t3 to t4 due to the response variation of the post-catalyst sensor. It varies. This is because, as described above, the difference in the post-catalyst sensor output Vr becomes larger due to the difference in the change rate of the post-catalyst sensor. Therefore, as shown in (B), the variation of the final integrated value increases as shown by d.
  • the variation in the integration end timing is reduced to a relatively short period from t1 to t2. This is because the integration ends before the difference in the post-catalyst sensor output Vr increases. Therefore, as shown in (B), the variation of the final integrated value can also be reduced as shown by e. In addition, the proportion of error included in these final integrated values is very small, and a highly accurate final integrated value can be obtained.
  • FIG. 12 shows the relationship between the post-catalyst sensor output Vr value (horizontal axis), which is the integration end timing, and the final integrated value (vertical axis) of the stored oxygen amount OSCa. As shown in the figure, the final integrated value tends to be larger as the post-catalyst sensor output Vr is decreased toward the lean side.
  • line a is reference data when a normal catalyst, a reference sensor, and low S fuel are used.
  • the line b is lower limit data when the normal catalyst, the high response sensor, and the high S fuel are used, that is, data when the sensor response and the fuel S concentration vary so that the final integrated value becomes the smallest. It is.
  • a fuel having an S concentration of 30 ppm is used as the low S fuel, and a fuel having an S concentration of 200 ppm is used as the high S fuel.
  • line c is reference data when an abnormal catalyst, a reference sensor, and low S fuel are used.
  • line d is upper limit data when the abnormal catalyst, the low response sensor, and the low S fuel are used, that is, when the sensor response and the fuel S concentration vary so that the final integrated value becomes the largest. It is data.
  • the difference between the lower limit data b of the normal catalyst and the upper limit data d of the abnormal catalyst when the integration end timing is set to the lean determination value VL as in the basic method is indicated by e.
  • the difference between the lower limit data b of the normal catalyst and the upper limit data d of the abnormal catalyst when the integration end timing is set to the stoichiometric determination value VA as in this embodiment is indicated by f.
  • the magnitude of the difference f itself is not much different from the difference e of the basic method, but since the original final integrated value is small, the ratio or ratio of the difference f with respect to the final integrated value is large. . Therefore, when taking into account variations in sensor responsiveness and fuel S concentration, the difference between the final integrated values between the normal and abnormal catalysts can be substantially enlarged, and both can be easily identified and the resolution can be improved.
  • the lean determination value VL and the rich determination value VR are changed according to the intake air amount Ga detected by the air flow meter 5.
  • the hysteresis width c which is the width between the hysteresis characteristic line a when changing to the lean side and the hysteresis characteristic line b when changing to the rich side, is supplied to the post-catalyst sensor 18. It changes in accordance with the flow rate of the gas, and consequently the intake air amount Ga that is the substitute value, and tends to increase as the intake air amount Ga increases. Then, according to the intake air amount Ga, the air-fuel ratio corresponding to the lean determination value VL and the rich determination value VR changes, and the value of the air-fuel ratio for switching the air-fuel ratio in the active air-fuel ratio control changes.
  • the lean determination value VL and the rich determination value VR are changed according to the intake air amount Ga in order to compensate for the change in the air-fuel ratio.
  • the intake air amount Ga is a predetermined reference value
  • the hysteresis characteristic line when changing to the lean side is a 1 and the lean determination value is VL 1 .
  • the lean determination value is changed to a larger (rich side) VL 2 so that switching is performed at the same air-fuel ratio at this time as well.
  • Such a change is performed using a map or the like stored in advance in the ECU 20.
  • the lean judgment value is changed to a smaller value (on the lean side).
  • the lean determination value is changed or corrected so that the value of the air-fuel ratio at which the air-fuel ratio is switched is always the value when the intake air amount Ga is the reference value.
  • the rich determination value VR When the intake air amount Ga increases from the reference value, the rich determination value is changed to a smaller value, and the intake air amount Ga decreases from the reference value. Sometimes the lean determination value is changed to a larger value, and the rich determination value is changed or corrected so that the value of the air-fuel ratio at which the air-fuel ratio is switched is always the value when the intake air amount Ga is the reference value.
  • a delay process for switching the air-fuel ratio is performed later than the timing when the post-catalyst sensor output Vr reaches the lean determination value VL or the rich determination value VR. That is, the air-fuel ratio is switched after a predetermined delay time has elapsed since the post-catalyst sensor output Vr reaches the lean determination value VL or the rich determination value VR.
  • the delay time is changed according to the intake air amount Ga.
  • Fig. 14 shows an example of delay processing.
  • the post-catalyst sensor output Vr reaches the rich determination value VR at time t1
  • the target air-fuel ratio A / Ft changes from the rich air-fuel ratio A / Fr (for example, 14.1) to the lean air-fuel ratio A / Fl ( For example, the control is switched to 15.1) and the lean control is started.
  • the post-catalyst sensor output Vr reaches the lean determination value VL at time t2, the target air-fuel ratio A / Ft is switched from the lean air-fuel ratio A / Fl to the rich air-fuel ratio A / Fr, and rich control is started.
  • the lean gas starts to leak from the catalyst around time t11, and the value of the post-catalyst air-fuel ratio A / Fr starts to increase from the stoichiometric value toward the lean air-fuel ratio A / Fl.
  • the post-catalyst sensor output Vr reaches the lean determination value VL
  • the post-catalyst air-fuel ratio A / Fr has sufficiently reached the vicinity of the lean air-fuel ratio A / Fl, and it can be considered that the catalyst has completely occluded oxygen. .
  • the post-catalyst sensor output Vr reaches the lean determination value VL at an earlier timing, and the air-fuel ratio becomes the rich air-fuel ratio A / Fr. Can be switched. Then, even though the post-catalyst air-fuel ratio A / Fr has not yet reached the vicinity of the lean air-fuel ratio A / F1, that is, oxygen is not completely occluded in the catalyst, the air-fuel ratio switching occurs.
  • the rich control is started before the desired initial state for the rich control is achieved. Therefore, during rich control, an oxygen amount with a smaller value than the original value may be measured.
  • the air-fuel ratio is switched after a predetermined delay time has elapsed since the post-catalyst sensor output Vr reaches the lean determination value VL or the rich determination value VR.
  • the delay time is increased as the intake air amount Ga is smaller. This is because the smaller the intake air amount Ga, the lower the gas flow rate with respect to the catalyst, the lowering the oxygen storage rate or release rate, and it takes time to create a complete storage state or complete release state.
  • the change of the delay time is performed using a map or the like stored in advance in the ECU 20.
  • the delay process can be omitted, and in this case, the air-fuel ratio is switched at the same time when the post-catalyst sensor output Vr reaches the lean determination value VL or the rich determination value VR. In any case, the air-fuel ratio is performed in synchronization with the post-catalyst sensor output Vr reaching the lean determination value VL or the rich determination value VR.
  • step S101 it is determined whether or not the diagnosis permission flag is on.
  • the diagnosis permission flag is a flag that is turned on when a precondition for diagnosis execution is satisfied.
  • the precondition is satisfied when the following conditions are satisfied. (1)
  • the upstream catalyst 11 is activated.
  • the pre-catalyst sensor 17 and the post-catalyst sensor 18 are activated.
  • the engine is in steady operation.
  • the diagnosis is incomplete during the current trip.
  • Condition (1) is established when the catalyst temperature Tc of the upstream catalyst 11 is within a predetermined activation temperature range.
  • the catalyst temperature Tc is estimated by the ECU 20 based on the engine operating state, but may be detected directly by a temperature sensor.
  • Condition (2) is satisfied when the temperatures of the detection elements of the pre-catalyst sensor 17 and the post-catalyst sensor 18 estimated by the ECU 20 are within a predetermined activation temperature range.
  • Condition (3) is when the engine speed calculated based on the output of the crank angle sensor 14 and the fluctuation range of the intake air amount Ga detected by the air flow meter 5 within a predetermined time are within a predetermined value. Is established.
  • the trip means the period from one start to stop of the engine.
  • the diagnosis is executed once per trip, and (4) is established when the diagnosis has not been completed once during the current trip.
  • diagnosis permission flag is not on (if it is off), it enters a standby state. On the other hand, when the diagnosis permission flag is on, the first target air-fuel ratio (A / Ft) of the active air-fuel ratio control is set in steps S102 to S104.
  • step S103 the initial target air-fuel ratio A / Ft is set to the lean air-fuel ratio. The As a result, lean control is executed.
  • step S104 the initial target air-fuel ratio A / Ft is set to the rich air-fuel ratio. Is done. Thus, rich control is executed.
  • the active air-fuel ratio control is started from the air-fuel ratio opposite to the air-fuel ratio of the current post-catalyst gas.
  • the first lean control or rich control is a so-called deserted mountain where no oxygen amount measurement is performed.
  • step S105 a lean determination value VL and a rich determination value VR are calculated based on the detected intake air amount Ga. This calculation is performed according to a predetermined map as described above. As the intake air amount Ga increases, a larger lean determination value VL is calculated, and a smaller rich determination value VR is calculated.
  • step S106 the delay time D is calculated based on the detected intake air amount Ga. This calculation is performed according to a predetermined map as shown in FIG. 16, and the larger the delay time D is, the smaller the intake air amount Ga is.
  • step S107 it is determined whether the current target air-fuel ratio A / Ft is a rich air-fuel ratio, that is, whether rich control is being executed. If the target air-fuel ratio A / Ft is a rich air-fuel ratio, the process proceeds to step S121. If the target air-fuel ratio A / Ft is not a rich air-fuel ratio (in the case of a lean air-fuel ratio), the process proceeds to step S108.
  • step S108 it is determined whether or not the post-catalyst sensor output Vr is equal to or less than the lean determination value VL, that is, whether or not the post-catalyst sensor output Vr is reversed to the lean side. If the after-catalyst sensor output Vr is not less than or equal to the lean determination value VL, the standby state is entered.
  • step S109 the time from when the post-catalyst sensor output Vr first becomes equal to or less than the lean determination value VL is counted, and whether or not this time is equal to or greater than the delay time D is determined. If no, the process enters a standby state. If yes, the process proceeds to step S110.
  • step S110 the target air-fuel ratio A / Ft is set to the rich air-fuel ratio, and rich control is started.
  • step S111 it is determined in step S111 whether or not the pre-catalyst air-fuel ratio A / Ff detected by the pre-catalyst sensor 17 is less than the stoichiometric value. If not, the process returns to step S110 to enter a standby state, and if so, the process proceeds to step S112, and the oxygen storage capacity OSC, here, the released oxygen amount OSCb is integrated and measured.
  • step S113 whether or not the post-catalyst sensor output Vr that is changing to the rich side exceeds the stoichiometric determination value VB, that is, whether or not the post-catalyst air-fuel ratio starts to change from stoichiometric to the rich air-fuel ratio. To be judged. If not, the process returns to step S110. If it exceeds, the process proceeds to step S114, and the integration of the released oxygen amount OSCb is terminated.
  • step S115 it is determined whether or not both the stored oxygen amount OSCa and the released oxygen amount OSCb have been measured. If not measured, the process proceeds to step S121, and if measured, the process proceeds to step S116.
  • steps S121 to S128 processing in which rich and lean are reversed from steps S108 to S115 is performed.
  • step S121 it is determined whether or not the post-catalyst sensor output Vr is greater than or equal to the rich determination value VR, that is, whether or not the post-catalyst sensor output Vr is reversed to the rich side. If not, the process enters a standby state. If the post-catalyst sensor output Vr is equal to or greater than the rich determination value VR, the process proceeds to step S122.
  • step S122 the time from when the post-catalyst sensor output Vr first becomes equal to or greater than the rich determination value VR is counted, and it is determined whether or not this time is equal to or greater than the delay time D. If no, the process enters a standby state. If yes, the process proceeds to step S123.
  • step S123 the target air-fuel ratio A / Ft is set to a lean air-fuel ratio, and lean control is started.
  • step S124 it is determined whether or not the pre-catalyst air-fuel ratio A / Ff detected by the pre-catalyst sensor 17 is larger than the stoichiometric value. If not, the process returns to step S123 to enter a standby state, and if so, the process proceeds to step S125, and the oxygen storage capacity OSC, here the stored oxygen amount OSCa, is integrated and measured.
  • the oxygen storage capacity OSC here the stored oxygen amount OSCa
  • step S126 it is determined whether or not the post-catalyst sensor output Vr that is changing to the lean side is lower than the stoichiometric determination value VA, that is, whether or not the post-catalyst air-fuel ratio starts to change from stoichiometric to the lean air-fuel ratio. To be judged. If not, the process returns to step S123. If it is less, the process proceeds to step S127, and the accumulation of the stored oxygen amount OSCa is terminated.
  • step S127 it is determined whether or not both the stored oxygen amount OSCa and the released oxygen amount OSCb have been measured. If not measured, the process proceeds to step S108, and if measured, the process proceeds to step S116.
  • step S117 the calculated value of the oxygen storage capacity OSC is compared with a predetermined abnormality determination value ⁇ . If OSC> ⁇ , the upstream catalyst 11 is determined to be normal in step S119, and the process proceeds to step S120. If OSC ⁇ ⁇ , the upstream catalyst 11 is determined to be abnormal in step S118, and the process proceeds to step S120.
  • step S120 the diagnosis permission flag is turned off, thereby ending the diagnosis process.
  • the diagnosis was performed by measuring the stored oxygen amount OSCa and the released oxygen amount OSCb once for simplification.
  • the lean control and the rich control are alternately executed repeatedly, the stored oxygen amount OSCa and the released oxygen amount OSCb are measured a plurality of times, and the average value is calculated. Based on the average value, A diagnosis may be made. Further, the diagnosis may be performed based on only one measurement value of the stored oxygen amount OSCa and the released oxygen amount OSCb.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

La présente invention se rapporte à un dispositif destiné à diagnostiquer des anomalies dans le catalyseur placé dans le passage des gaz d'échappement d'un moteur à combustion interne. Un capteur post-catalyseur destiné à détecter le rapport air-combustible des gaz d'échappement en aval du catalyseur est prévu, ledit capteur ayant des caractéristiques d'hystérésis proches de la stœchiométrie. En même temps que la sortie de capteur post-catalyseur atteignant une valeur de détermination prescrite, une commande de rapport air-combustible active est réalisée pour faire passer le rapport air-combustible en amont du catalyseur d'un rapport air-combustible pauvre à un rapport air-combustible riche, ou vice versa, et pendant ladite commande, la quantité d'oxygène absorbé et relâché par le catalyseur est mesurée de façon cumulée. Pendant la commande lors de laquelle le rapport air-combustible est réglé sur le rapport air-combustible pauvre ou sur le rapport air-combustible riche, la mesure d'oxygène cumulé prend fin lorsque la sortie du capteur post-catalyseur prend une valeur indiquant que le rapport air-combustible des gaz d'échappement en aval du catalyseur a commencé à changer, passant de la stœchiométrie vers ledit rapport air-combustible pauvre ou le rapport air-combustible riche.
PCT/JP2012/002754 2012-04-20 2012-04-20 Dispositif de diagnostic d'anomalies de catalyseur WO2013157048A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015222046A (ja) * 2014-05-23 2015-12-10 トヨタ自動車株式会社 内燃機関の制御装置
US10066534B2 (en) 2015-08-31 2018-09-04 Toyota Jidosha Kabushiki Kaisha Internal combustion engine

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Publication number Priority date Publication date Assignee Title
JP2004225684A (ja) * 2002-11-27 2004-08-12 Toyota Motor Corp 酸素センサの異常検出装置
JP2005220901A (ja) * 2004-01-06 2005-08-18 Toyota Motor Corp 内燃機関の触媒劣化状態評価装置
JP2005299587A (ja) * 2004-04-15 2005-10-27 Toyota Motor Corp 内燃機関の空燃比制御装置
JP2010185371A (ja) * 2009-02-12 2010-08-26 Toyota Motor Corp 触媒劣化診断装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004225684A (ja) * 2002-11-27 2004-08-12 Toyota Motor Corp 酸素センサの異常検出装置
JP2005220901A (ja) * 2004-01-06 2005-08-18 Toyota Motor Corp 内燃機関の触媒劣化状態評価装置
JP2005299587A (ja) * 2004-04-15 2005-10-27 Toyota Motor Corp 内燃機関の空燃比制御装置
JP2010185371A (ja) * 2009-02-12 2010-08-26 Toyota Motor Corp 触媒劣化診断装置

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015222046A (ja) * 2014-05-23 2015-12-10 トヨタ自動車株式会社 内燃機関の制御装置
US10066534B2 (en) 2015-08-31 2018-09-04 Toyota Jidosha Kabushiki Kaisha Internal combustion engine

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