CN100554656C - Exhaust gas purification system for internal combustion engine diagnostic device, emission control system and diagnostic method - Google Patents

Abstract

The present invention relates to a kind of exhaust gas purification system for internal combustion engine diagnostic device, emission control system and diagnostic method.The equipment that is used for vent systems comprises: main exhaust passageway, be arranged on the main catalytic converter in the main exhaust passageway, and bypass exhaust passage is arranged on the bypass catalytic converter in the bypass exhaust passage, is used for opening or closing the valve of main exhaust passageway part.Bypass exhaust passage point of branching that bypass exhaust passage is told from main exhaust passageway and the main catalytic converter upstream side, bypass channel integrates with between the junction of main exhaust passageway the main exhaust passageway bypass.First sensor is represented first air fuel ratio of the exhaust in the bypass exhaust passage, and second sensor represents to flow into second air fuel ratio of the exhaust of main catalytic converter.Controller judges based on the air fuel ratio of first and second exhausts whether be in the valve of closing setting leaks exhaust.

Description

Exhaust gas purification system for internal combustion engine diagnostic device, emission control system and diagnostic method

Technical field

The present invention relates to purify technical field from the exhaust of internal-combustion engine (hereinafter being also referred to as " motor ") discharging.As used herein, term " purification " refers to reduce the toxicity of the exhaust of being discharged by internal-combustion engine.Especially, the present invention relates to whether the flow channel switching valve in the emission control system is existed the diagnosis of leakage.

Exhaust is introduced the bypass exhaust passage that comprises the bypass catalytic converter.Preferably, bypass exhaust passage is oppositely arranged on the upstream of the main catalytic converter of conventional exhaust systems, after the cold starting of motor began, flow channel switching valve turned to exhaust to pass through bypass exhaust passage.

Background technique

Usually, in the cold starting of internal-combustion engine and the activation fully of catalytic converter, between promptly the temperature of catalytic converter rose to when enough high, exhaust can't be purified fully.When main catalytic converter is arranged on the certain distance (for example, below automobile) in the downstream of motor, especially produce this situation.Yet if main catalytic converter is provided with nearerly from motor, because thermal degradation when, the serviceability of catalyzer or life-span may be lost significantly.

Relevant vent systems comprises and parallel bypass exhaust passage and the bypass catalytic converter that is provided with of the upstream portion of the main exhaust passageway that leads to main catalytic converter.Flow channel switching valve is used to be right after after the cold starting of motor begins exhaust is incorporated into bypass exhaust passage.Like this because the bypass catalytic converter is arranged on the upstream of vent systems with respect to main catalytic converter, so its can be activated more quickly, thereby the purification of exhaust is more early begun.

In relevant vent systems, when flow channel switching valve does not switch stream up hill and dale (for example, when the supposition flow channel switching valve stops exhaust gas leakage to main exhaust passageway, exhaust gas leakage is to main exhaust passageway), the exhaust of Jing Huaing may not be discharged in the air, is activated fully up to main catalytic converter.

Relevant vent systems comprises the method that is used to detect the minimizing of the use flow that flow channel switching valve caused; Yet relevant vent systems does not comprise the relevant mechanism of leakage of the exhaust that does not purify with any diagnosis.Therefore, need a kind of equipment that can correctly diagnose the leakage of flow channel switching valve.

Summary of the invention

The present invention relates to a kind of equipment of emission control system of disgnosizing internal combustion engine.This emission control system comprises main exhaust passageway that is connected to internal-combustion engine and the main catalytic converter that is arranged on the downstream along main exhaust passageway.The bypass exhaust passage that will be used for the bypass main exhaust passageway is arranged on the part place of main exhaust passageway of the upstream of main catalytic converter.In addition, along bypass exhaust passage the bypass catalytic converter is set.In addition, partly be provided with the valve that is used to close main exhaust passageway by the main exhaust passageway of bypass exhaust passage bypass.Bypass exhaust passage has the first sensor of the air fuel ratio that is used to detect the exhaust of flowing through bypass exhaust passage.In addition, main exhaust passageway has second sensor of the air fuel ratio that is used to detect the exhaust of introducing main catalytic converter.First and second sensors are connected to controller.

When valve is in closed condition, the leakage of diagnosis valve.Aspect according to an embodiment of the invention, based on the first sensor of the air fuel ratio that is used to detect the exhaust by bypass exhaust passage and second sensor that is used to detect the air fuel ratio of the exhaust by main exhaust passageway diagnose this leakage.Owing to use the air-fuel ratio sensor in the control that can be used for internal-combustion engine traditionally to diagnose the leakage of valve, so the sensor that can not need to add is carried out diagnosis.

An aspect according to inventive embodiment provides a kind of equipment that is used for the emission control system of disgnosizing internal combustion engine.This equipment comprises: main exhaust passageway; Main catalytic converter, it is set in the main exhaust passageway; Bypass exhaust passage, itself and main exhaust passageway intercommunication fluid, thus make main exhaust passageway point of branching that bypass exhaust passage is told from main exhaust passageway and the main catalytic converter upstream side, bypass exhaust passage converges the part bypass between the junction point of main exhaust passageway; The bypass catalytic converter, it is set in the bypass exhaust passage; Be arranged in the described part of main exhaust passageway, be used for opening or closing the valve of the described part of main exhaust passageway; First sensor, it is arranged on first signal that is illustrated in first air fuel ratio of the exhaust of flowing in the bypass exhaust passage in the bypass exhaust passage with output; Second sensor, it is arranged in the main exhaust passageway secondary signal of second air fuel ratio that flows into the exhaust of main catalytic converter with the output expression; And controller, it receives first and second signals, and controller judges based on first and second signals whether be in the valve of closing setting makes exhaust gas leakage arrive the described part of main exhaust passageway.

Another aspect according to an embodiment of the invention provides a kind of method of emission control system of disgnosizing internal combustion engine, and this method comprises: first air fuel ratio of the exhaust of the main exhaust passageway that detecting flows through comprises main catalytic converter; Flow through second air fuel ratio of exhaust of bypass exhaust passage of detection, bypass exhaust passage and main exhaust passageway intercommunication fluid, thereby make main exhaust passageway point of branching that bypass exhaust passage is told from main exhaust passageway and the main catalytic converter upstream side, bypass exhaust passage converges the part bypass between the junction point of main exhaust passageway, bypass exhaust passage comprises the bypass catalytic converter; Prevent that with valve exhaust is mobile along main exhaust passageway; And, judge whether exhaust leaks by valve based on first and second air fuel ratios.

Description of drawings

The accompanying drawing that is included in here and constitutes this specification part shows the preferred embodiments of the present invention, is used from explanation feature of the present invention with general remark that provides above and detailed description given below.

Fig. 1 is the schematic representation that internal combustion engine exhaust system constructed according to the invention is shown.

Fig. 2 is the plotted curve that illustrates according to the leak diagnostics of the first embodiment of the present invention.

Fig. 3 is the plotted curve that leak diagnostics according to a second embodiment of the present invention is shown.

Fig. 4 is the flow chart of processing that the leak diagnostics of a third embodiment in accordance with the invention is shown.

Fig. 5 is the sequential chart that illustrates according to embodiment's shown in Figure 4 leak diagnostics.

Fig. 6 is the sequential chart that the processing of diagnosis catalyst degradation degree is shown.

Fig. 7 is the plotted curve that the relation between time difference Δ T and the catalyst degradation degree is shown.

Fig. 8 is the plotted curve that the relation between catalyst degradation degree and the threshold value L is shown.

Fig. 9 is the sequential chart that the leak diagnostics of a fourth embodiment in accordance with the invention is shown.

Embodiment

Below, describe various preferred embodiment of the present invention with reference to the accompanying drawings in detail.Although the emission control system to the four-cylinder internal-combustion engine describes, be not limited to this certainly.In other words, also predicted internal-combustion engine with different configurations, cylinder number and mode of execution.

Fig. 1 illustrates the exhaust passage and the illustrative arrangement of the controller that uses in the vent systems of the internal-combustion engine that is used for powered vehicle.

The cylinder head 1a of internal-combustion engine 1 have can be configured in inner from first relief opening of opening laterally to four-cylinder (only illustrating Fig. 1) 2.In the relief opening 2 (only illustrating among Fig. 1) each is connected to the upstream portion of each main exhaust passageway 3.Preferably converge with first the upstream portion (only illustrating among Fig. 1), thereby form the single main exhaust circulation road that leads to downstream part main catalytic converter 4, that be positioned at main exhaust passageway 3 in the part that is provided with flow channel switching valve 5 to corresponding four main exhaust passageway 3 of four-cylinder.The main catalytic converter 4 that is preferably located in under-vehicle can have big capacity and can contain three-way catalyst and hydrogen carbon (HC) capture (trap) catalyzer.From the blast air of relief opening 2 discharging cross main exhaust passageway 3 upstream portion, placed the part of flow channel switching valve 5, the downstream part of main exhaust circulation road 3, up to the main catalytic converter 4 that is used to purify the exhaust of during normal engine operation, discharging.Flow channel switching valve 5 can be provided with shut-off block, and this shut-off block changes stream by allowing or stoping blast air to cross exhaust passage 3.Be provided with may be fly valve, flapper valve or arbitrarily the flow channel switching valve 5 (only illustrating among Fig. 1) of equivalents open or close main exhaust passageway 3.Can single flow channel switching valve 5 be set for example being connected to first the back to the concourse of the upstream portion of a plurality of main exhaust passageway 3 of four main exhaust passageway 3 upstream portion of four-cylinder.Preferably the break 5a by for example electric motor that is used to reconfigure flow channel switching valve 5, solenoid, vacuum switch or any equivalents drives flow channel switching valve 5.

The upstream portion of four bypass exhaust passage 7 (only illustrating among Fig. 1) is from the upstream portion branch of corresponding four main exhaust passageway 3.Bypass exhaust passage 7 has the cross-section area littler than the cross-section area of main exhaust passageway 3.Point of branching 6 (that is upstream extremity of the upstream portion of each bypass exhaust passage 7; Only illustrate one among Fig. 1) preferably be arranged on corresponding main exhaust passageway 3 upstream portion the upstream as far as possible at a distance, promptly as much as possible near cylinder head 1a.The upstream portion of four bypass exhaust passage 7 is preferably converged to form the single bypass blast air passage downstream part, that lead to bypass catalytic converter 8 as bypass exhaust passage 7.Preferably, the adjacent bypass catalytic converter 8 that can use three-way catalyst that after the upstream portion concourse of four bypass exhaust passage 7, is provided with.Preferably, bypass catalytic converter 8 has the capacity littler than the capacity of main catalytic converter 4, and be equipped with can be at the best catalyzer that activates of low temperature.The single blast air passage that extends from the outlet of bypass catalytic converter 8 preferably is connected the junction point 9 (be the upstream of the inlet of main catalytic converter 4, and the downstream of flow channel switching valve 5) of main exhaust passageway 3.That is, bypass exhaust passage 7 is set and comes the part of bypass at the main exhaust passageway 3 of the upstream of main catalytic converter 4.Flow channel switching valve 5 can be installed in this part of main exhaust passageway 3.

Respectively the Your Majesty is swum air-fuel ratio sensor 10 and main downstream air-fuel ratio sensor 11 and be arranged on the entrance and exit place of main catalytic converter 4.In addition, bypass upstream air-fuel ratio sensor 12 and bypass downstream air-fuel ratio sensor 13 are separately positioned on the entrance and exit place of bypass catalytic converter 8.After activating main catalytic converter 4, the Your Majesty swims the feedback control that air-fuel ratio sensor 10 and main downstream air-fuel ratio sensor 11 can be carried out traditional air fuel ratio.Can respond the output signal of swimming air-fuel ratio sensor 10 from the Your Majesty, for example be ejected into first and control the air fuel ratio of motor to the fuel quantity of four-cylinder by control.Can use any deviation of the output signal compensation control characteristic of autonomous downstream air-fuel ratio sensor 11.Similarly, when using bypass catalytic converter 8, bypass upstream air-fuel ratio sensor 12 and bypass downstream air-fuel ratio sensor 13 can be carried out the feedback control of traditional air fuel ratio.In other words, when using bypass catalytic converter 8, can respond output signal, the air fuel ratio of control motor from bypass upstream air-fuel ratio sensor 12.Can use any deviation that compensates control characteristic from the output signal of bypass downstream air-fuel ratio sensor 13.Air- fuel ratio sensor 10,11,12 and 13 can comprise: the broadband air-fuel ratio sensor that has the output characteristics of substantially linear with respect to the air fuel ratio of exhaust, or (for example have two kinds of output characteristics, represent rich air fuel ratio, or represent poor air fuel ratio) lambda sensor.Usually because the control characteristic of above-mentioned air fuel ratio control preferably uses the broadband air-fuel ratio sensor as upstream air- fuel ratio sensor 10 and 12, preferably use lambda sensor as downstream air- fuel ratio sensor 11 and 13 to be provided as the advantage of this aspect.Bypass upstream air-fuel ratio sensor 12 can be set to be used for detect first sensing element of the air fuel ratio of bypass blast air passage, and the Your Majesty swims second sensing element that air-fuel ratio sensor 10 can be set to be used for the air fuel ratio of the exhaust that detects the main exhaust circulation road, flow into main catalytic converter 4.

In addition, first of internal-combustion engine 1 in the four-cylinder each comprises: spark plug 21 (only illustrating among Fig. 1), gas-entered passageway 22 (only illustrating among Fig. 1) and can be arranged on Fuelinjection nozzle 23 (only illustrating among Fig. 1) in the gas-entered passageway 22.Preferably, the electronic control throttle valve 24 that can use actuators such as motor to open or close is arranged on the upstream of gas-entered passageway 22.Solar term chamber (plenum) can be set between gas-entered passageway 22 and throttle valve 24.In addition, can be used to detect the Air flow meter 25 that sucks air quantity and be arranged on the upstream of throttle valve 24, the downstream of air cleaner 26 motor 1 is employed.

The various parameters of control unit of engine 27 controlling combustion engines 1 (for example, set the fuel quantity that each Fuelinjection nozzle 23 sprays, set the spark timing of each spark plug 21, set the opening degree of throttle valve 24, drive break 5a with the opening/closing situation of setting flow channel switching valve 5 etc.).Except receiving the output signal of air- fuel ratio sensor 10,11,12 and 13, from coolant temperature sensor for example 28 be used to detect (promptly by the position of the accelerator pedal of driver operation, the amount of entering into) other signal of sensor of sensor 29 also can be imported into control unit of engine 27.Preferably, control unit of engine 27 can also diagnose flow channel switching valve 5 whether to have leakage.

Preferably, in response to the low temperature that cold starting begins rear engine 1 or exhaust, flow channel switching valve 5 is closed exhaust passage 3.Therefore, from corresponding point of branching 6,, flow to bypass catalytic converter 8 from whole exhausts that each cylinder discharged by corresponding bypass exhaust passage 7.Because for example bypass catalytic converter 8 is arranged on very the position near relief opening 2, and its size is less relatively, so bypass catalytic converter 8 can be by quick active.This makes exhaust to be cleaned in the stage morning after cold starting begins.

Along with the temperature of motor during the The pre-heat treatment 1 or exhaust raises, because the catalyzer of main catalytic converter 4 activated fully by this heat, so flow channel switching valve 5 is opened.Similarly, the most of exhaust from the cylinder discharging arrives main catalytic converter 4 by main exhaust passageway 3.Although bypass exhaust passage 7 is not closed, bypass exhaust passage 7 is not flow through in most of exhaust.On the contrary, blast air is crossed main exhaust passageway 3.This be because the cross-section area of bypass exhaust passage 7 less than the cross-section area of exhaust passage 3, and the bypass catalytic converter 8 that is provided with in bypass blast air passage has caused bigger flow resistance.Owing to the difference of gas-flow resistance, can also avoid the thermal degradation when of bypass catalytic converter 8.

Next, illustrate according to the first embodiment of the present invention to whether there being diagnosis by any leakage of flow channel switching valve 5.In the following embodiments, two upstream air- fuel ratio sensors 10 and 12 are preferably the broadband air-fuel ratio sensor, and two downstream air- fuel ratio sensors 11 and 13 are preferably lambda sensor.When diagnosis is leaked according to the first embodiment of the present invention, only adopt two upstream air- fuel ratio sensors 10 and 12.

Fig. 2 illustrates that flow channel switching valve 5 is in closed condition after cold starting begins, and the feedback control that bypass upstream air-fuel ratio sensor 12 provides air fuel ratio (promptly, activate after the bypass catalytic converter 8) time, be used to diagnose a series of plotted curves of first embodiment of leakage.As mentioned above, because bypass catalytic converter 8 can be by quick active, so feedback control almost begins after cold starting immediately.By closing flow channel switching valve 5 provisionally, after activating, main catalytic converter 4 also can carry out diagnosis.

Fig. 2 (a) is illustrated in during the normal condition, promptly when not existing leakage not have the thermal degradation when of bypass catalytic converter 8, by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB (hereinafter being also referred to as air fuel ratio AFB) with swim the plotted curve of the comparison between the air-fuel ratio sensor 10 detected air fuel ratio AFM (hereinafter being also referred to as air fuel ratio AFM) by the Your Majesty.Shown in Fig. 2 (a), according to traditional air-fuel ratio feedback control, the air fuel ratio that makes exhaust changes near theoretical air fuel ratio (being the chemically correct fuel state) thereby fuel injection amount periodically fluctuates.Therefore the periodically rich state of 1 burning and each the poor state of air fuel ratio from the chemically correct fuel change of state to motor.Yet,, therefore can determine the corresponding output signal of fluctuation with the air fuel ratio of motor because bypass upstream air-fuel ratio sensor 12 directly influences by the exhaust from motor 1.That is,, maybe can be considered to the air fuel ratio of motor itself by the air fuel ratio of air-fuel ratio sensor 12 detected air fuel ratio AFB in bypass upstream corresponding to motor.With compare by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB, swimming richness/poor state that the plotted curve of air-fuel ratio sensor 10 detected air fuel ratio AFM shows above chemically correct fuel by the Your Majesty can reach in shorter amount of time.It also shows and changes regularly, i.e. the point that changes between theoretical air fuel ratio, rich poor state is compared with the point that is changed by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB and to be postponed.This is because the oxygen capacity of the catalyzer of bypass catalytic converter 8 causes.When the air fuel ratio of exhaust becomes poor state, absorb oxygen, when the air fuel ratio of exhaust becomes rich state, discharge oxygen.Therefore,, do not change in the downstream side of bypass catalytic converter 8 although the air fuel ratio of exhaust periodically fluctuates between rich state and poor state, saturated up to the oxygen capacity of bypass catalytic converter 8.

Fig. 2 (b) illustrates the correlation properties when exhaust gas leakage takes place the flow channel switching valve 5 that is in closed condition.Because this leakage does not influence by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB, therefore do not change from the normal state shown in Fig. 2 (a).Yet the Your Majesty swims air-fuel ratio sensor 10 and detects the exhaust of leaking by flow channel switching valve 5, i.e. the not exhaust by bypass catalytic converter 8.Therefore, when bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB, detected air fuel ratio AFM fluctuateed between rich and poor state.In addition, the value of richness/poor state (that is periodically variable amplitude) is lower than the value that is detected richness/poor state of air fuel ratio AFB by bypass upstream air-fuel ratio sensor 12.This is owing to cause with the dilution that is caused that mixes of exhaust by bypass catalytic converter 8.

For example, can be in swim air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty rich change of state to time (vice versa) of poor state and by the corresponding time among the bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB (promptly, when rich change of state was poor state, vice versa) between determine time lag Δ t.If time lag Δ t less than threshold value, then is judged as and leaks.

Refer again to Fig. 2 (a), can with by the interval t1 of rich state among the bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB or poor state with swim air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty in the interval t2 of corresponding rich state or poor state compare.If t1 is equal substantially with t2 at interval, then is judged as and leaks.

Judge whether that the method that substitutes of leaking can provide additional reliability.For example, judge to leak to comprise the repeatedly change calculations mean value of air fuel ratio of basis, or assessment is substantially equal to the time lag Δ t of poor (t1-t2) between interval t1 and the t2.The method of these features is used in explanation now.

Fig. 2 (c) illustrates the variation of air fuel ratio AFM when some deterioration of catalyzer of catalytic converter 8.When the deterioration owing to catalyzer caused oxygen capacity to reduce, the basic variation of being swum air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty was constant.Yet rich/poor state fluctuation is faster.That is, shorten about time lag Δ t by the variation of bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB.Yet the time lag t 2 of richness/poor state is elongated.If catalyzer has corrupted to 1 oxygen capacity point, then time lag Δ t or time lag t1 and t2 possibly can't distinguish from the situation shown in Fig. 2 (b).Yet because the deterioration of catalyzer is carried out in fact lentamente, therefore when the catalyst member deterioration, time lag Δ t or time lag t1 and t2 get the intermediate value between the characteristic shown in Fig. 2 (a) and 2 (b).Therefore, in this stage, can be judged as catalyzer deterioration.Therefore, the deterioration of catalyzer can exist the leakage of flow channel switching valve 5 to distinguish mutually with being judged as.

For example, if less than first threshold, then can being judged as, time lag Δ t leaks.Yet, if time lag Δ t greater than second threshold value, can not be judged as and leaks.In addition, if time lag Δ t falls in the predetermined scope, for example itself then can be judged as the catalyzer deterioration in the bypass catalytic converter 8 just between third and fourth threshold value between first and second threshold values.Third and fourth threshold value can equal first and second threshold values respectively.

Detect the interval t1 of rich state among the air fuel ratio AFB or poor state and swim corresponding rich state among the air-fuel ratio sensor 10 detected air fuel ratio AFM or the interval t2 of poor state judges by bypass upstream air-fuel ratio sensor 12 by the Your Majesty.Equate mutually if t1 and t2 are basic at interval, then be judged as leakage has taken place.In addition, if t2 then can not be judged as and leaks fully less than interval t1 at interval.If at interval t2 is slightly less than t1 at interval, then can be judged as the catalyzer deterioration in bypass catalytic converter 8.

According to above embodiment, even when the feedback control of traditional air fuel ratio continues, also can diagnose the leakage of flow channel switching valve 5.In addition, when carrying out this diagnosis, the toxicity of exhaust can not worsen.In addition, can carry out and comprise and judge the whether accurate leak diagnostics of deterioration of catalyzer.

Fig. 3 illustrates to be used for a series of plotted curves according to a second embodiment of the present invention that diagnosis was leaked after bypass catalytic converter 8 activates when flow channel switching valve 5 was in closed condition after cold starting begins.Between this diagnostic period, by with the constant cycle and the feedforward control of amplitude, force to change the air fuel ratio (promptly from richness to poor, vice versa) of motor.

Be similar to Fig. 2 (a)～2 (c), Fig. 3 (a) illustrates normal state (do not have leak, catalyst-free deterioration), and Fig. 3 (b) illustrates and leaks, and Fig. 3 (c) illustrates catalyst degradation.Should be noted in the discussion above that diagnostic method is identical with diagnostic method among first embodiment.

According to first embodiment shown in Figure 2, the cycle of the richness of the air fuel ratio of motor/poor state and the variation of amplitude, the driving situation with respect to motor 1 is not required to be constant.Yet according to second embodiment, the air fuel ratio of motor changed regularly with constant cycle and amplitude.This can improve, and diagnosis is leaked and the precision of catalyst degradation.In addition, even when the air fuel ratio of motor forces to change in feedforward control, richness/poor state periodically changes with respect to chemically correct fuel, thereby average air-fuel ratio can be remained near the chemically correct fuel.Therefore, the toxicity of exhaust can not worsen.Preferably, the cycle that can be not the air fuel ratio of motor not be changed is set at long attending the meeting and reduces the oxygen capacity of catalyzer significantly.

According to embodiments of the invention, provide a kind of equipment that is used for the emission control system of disgnosizing internal combustion engine.This equipment comprises the bypass exhaust passage that is arranged on the main catalytic converter upstream.Along bypass exhaust passage the bypass catalytic converter is set, and is provided for making exhaust to turn to flow channel switching valve by bypass exhaust passage.This equipment also comprises: first air-fuel ratio sensor is used to detect the air fuel ratio of the exhaust of bypass catalytic converter upstream; And second air-fuel ratio sensor, be used to detect the air fuel ratio of the exhaust of main catalytic converter upstream.When flow channel switching valve is in closed condition,, can diagnose the leakage of flow channel switching valve by using signal from the detection of first and second sensors.

When the air fuel ratio of motor periodically changes, can diagnose the leakage of flow channel switching valves according to two following steps: (i) determine by the variation between detected rich state of second air-fuel ratio sensor and the poor state with respect to time lag by the similar variation between the detected state of first air-fuel ratio sensor between rich state and poor state; And, judge whether to exist and leak (ii) based on this time lag.

As selection, when the air fuel ratio of motor periodically changes, can diagnose the leakage of flow channel switching valves according to two following steps: (i) determine by the time lag in the variation between detected rich state of second air-fuel ratio sensor and the poor state with by the similar time lag between the detected state of first air-fuel ratio sensor between rich state and poor state; And, judge whether to exist and leak (ii) by comparing the time lag.

In order periodically between rich state and poor state, to change, the cyclically-varying of the air fuel ratio of the motor that can adopt and use first air-fuel ratio sensor, passes through feedback control.

As selection, between diagnostic period, the air fuel ratio of motor can periodically change with the predetermined cycle.In addition, because average air-fuel ratio remains essentially in chemically correct fuel, even be forced under the situation of variation in sexual cycle in the air fuel ratio of motor, the toxicity of exhaust can not worsen yet.

When the flow channel switching valve 5 that is used for opening/closing main exhaust passageway 3 is in the closed position, be introduced into bypass exhaust passage from whole exhausts of internal-combustion engine 1, and by the bypass catalytic converter.Yet when flow channel switching valve 5 was shown in an open position, major part was walked around bypass catalytic converter 8 from the exhaust of internal-combustion engine 1, then by main catalytic converter 4.This is because the different flow resistances in main exhaust passageway 3 and the bypass exhaust passage 7 causes.

Preferably, when flow channel switching valve 5 is in the closed position, carries out and be used to judge whether to exist the diagnosis of any leakage by flow channel switching valve 5.For example, can be in response to the feedback control of air fuel ratio, diagnosis is carried out in the cyclically-varying of the air fuel ratio by using motor.When the air fuel ratio of motor periodically changes, also periodically change together with the air fuel ratio of motor by first air-fuel ratio sensor, 12 detected signals.This is because first air-fuel ratio sensor 12 is arranged on the upstream of bypass catalytic converter 8.Yet because the oxygen capacity of catalyzer, the air fuel ratio of the exhaust in bypass catalytic converter 8 downstreams changes in relatively little scope with a time lag with respect to the air fuel ratio of motor.

If flow channel switching valve 5 does not leak, second air-fuel ratio sensor 10 that then is arranged on main catalytic converter 4 upstreams only receives the exhaust by bypass catalytic converter 8.As a result, as mentioned above, change in relatively little scope with a time lag by of the cyclically-varying of second air-fuel ratio sensor, 10 detected air fuel ratios with respect to exhaust air-fuel ratio.Yet,, changing with roughly the same time of exhaust air-fuel ratio by second air-fuel ratio sensor, 10 detected air fuel ratios if flow channel switching valve 5 leaks.Therefore by second air-fuel ratio sensor, 10 detected air fuel ratios also with respect to changing by first air-fuel ratio sensor, 12 detected air fuel ratios.This is because at least some directly pass through second air-fuel ratio sensor 10 from the exhaust of motor 1, promptly not by bypass catalytic converter 8.For example, if ignore from the distance relief opening 2 to first air-fuel ratio sensors 12 and from the difference the effect of the distance of relief opening 2 to second air-fuel ratio sensors 10, then richness/poor the state by first air-fuel ratio sensor 12 and second air-fuel ratio sensor, 10 detected air fuel ratios will change when flow channel switching valve 5 leaks.

Therefore can leak by the time lag diagnosis of time lag or richness/poor change of state and whether take place or the leakage of which kind of degree.

As mentioned above, oxygen capacity can be influenced by the deterioration of catalyzer.Yet,, regularly not quite identical mutually by the variation between first air-fuel ratio sensor 12 and second air-fuel ratio sensor, the 10 detected richnesses/poor state if deterioration has taken place.In addition, according to degradation, time lag shortens.Therefore, even there is catalyst degradation, also can judge whether to leak.

According to above embodiment, can be correctly and easily diagnose any leakage of flow channel switching valve 5, thus the exhaust of having avoided not purifying during the early stage of engine start is discharged in the air.

Between diagnostic period, if richness/poor state about the chemically correct fuel cyclically-varying, average air-fuel ratio may equal or approach chemically correct fuel at least.Therefore, the toxicity of exhaust release can not worsen.

Next, the diagnosis for flow channel switching valve 5 leaks illustrates a third embodiment in accordance with the invention.In the 3rd embodiment, vent systems is identical with vent systems among first embodiment, and the configuration of exhaust and control system is identical with configuration shown in Figure 1.In the 3rd embodiment, bypass upstream air-fuel ratio sensor 12 can be set to the first air fuel ratio detection part, and the Your Majesty swims air-fuel ratio sensor 10 can be set to the second air fuel ratio detection part.The Your Majesty swims air-fuel ratio sensor 10 and is installed on the part of the main exhaust circulation road between junction point 9 and the main catalytic converter 4.This sensor 10 is used to detect the air fuel ratio of exhaust in downstream that bypass blast air passage is connected to the junction point 9 of main exhaust circulation road.Preferably, two upstream air- fuel ratio sensors 10 and 12 comprise the broadband air-fuel ratio sensor, and two downstream air- fuel ratio sensors 11 and 13 comprise lambda sensor.In addition, in the 3rd embodiment, although the air fuel ratio of motor can be from richness to poor instantaneous change, vice versa, and the variation from poor to richness only is described.

Fig. 4 illustrates the flow chart according to the 3rd embodiment's diagnostic process.At first, read the opening degree TVO (step S1) of the angular velocity NE rotation of per minute (for example according to) of motor, the load TP of motor (for example according to the fuel quantity that sprays) and throttle valve 24.Carry out then about carrying out the judgement of diagnosing (step S2) based on operational condition NE, TP and TVO.When bypass catalytic converter 8 activates, main catalytic converter 4 is not in the high temperature air and flow channel switching valve 5 is carried out diagnosis when in the closed position.Can carry out diagnosis if be judged as, then the target air-fuel ratio with internal-combustion engine is made as poor state (step S3).Then, produce waiting mode, be shown as poor state (step S4) up to signal from 13 outputs of bypass downstream air-fuel ratio sensor.That is, the air fuel ratio of motor remains on poor state, and is saturated up to the oxygen capacity of bypass catalytic converter 8.After this, the target air-fuel ratio transient change is to rich state (step S5).In this case, when monitoring that bypass upstream air-fuel ratio sensor 12 and Your Majesty swim the output signal variation of air-fuel ratio sensor 10, calculate Diagnostic parameters (described in hereinafter) (step S6).If finished the diagnosis (step S7) for predetermined period of time after target air-fuel ratio is set to rich state, then target air-fuel ratio being replied is chemically correct fuel (step S8).Then, Diagnostic parameters is compared with the threshold value L that is used to judge leakage (step S9).From changing to rich state (step S5) institute elapsed time, can judge whether diagnosis is finished based on for example.As selection, when the output signal of bypass downstream air-fuel ratio sensor 13 is shown as rich state, can finish diagnosis.At step S9, if be judged as Diagnostic parameters greater than threshold value L, then be judged as flow channel switching valve 5 leakage has taken place, and can produce alarm, for example start the warning light (not shown) and notify the operator of vehicle or vehicle service personnel to have fault state (step S10).

Fig. 5 as the sequential chart that judge to leak illustrates: the output signal of the variation of the target engine air fuel ratio of internal-combustion engine 1, bypass downstream air-fuel ratio sensor 13, swim air-fuel ratio sensor 10 detected air fuel ratio AFM and by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB by the Your Majesty.As mentioned above,, the target engine air fuel ratio is become poor state forcibly from chemically correct fuel, instantaneously then change into rich state in order to diagnose.Then, because flow channel switching valve 5 closes, so blast air crosses bypass exhaust passage 7, and oxygen is stored in the catalyzer of bypass catalytic converter 8 during poor state.So far, the output signal of bypass downstream air-fuel ratio sensor 13 that is arranged on the downstream of bypass catalytic converter 8 becomes after a time lag and shows poor state.In addition, bypass upstream air-fuel ratio sensor 12 and Your Majesty swim air-fuel ratio sensor 10 and show that the air fuel ratio of exhaust is in poor state.In addition, in the 3rd embodiment, after the signal from bypass downstream air-fuel ratio sensor 13 showed poor state, target air-fuel ratio was changed to rich state with a time lag.

When the air fuel ratio of motor is changed to rich state, be rich state by the bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB transient change of the upstream that is arranged on bypass catalytic converter 8.Yet, owing to be stored in oxygen evolution in the bypass catalytic converter 8 to the downstream of bypass catalytic converter 8, therefore swim air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty and do not change immediately, promptly it is changed to rich state after a time lag shown in solid line.That is, shown in solid line, when not existing when leaking, by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB with swum air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty obviously different.

Yet if for example because the seal defect of valve body etc., flow channel switching valve 5 leaks, and the exhaust of part amount arrives that the Your Majesty swims air-fuel ratio sensor 10 and not by bypass catalytic converter 8.Therefore, shown in dotted line, swim air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty and show richer state relatively.In other words, when leaking generation,, swim air-fuel ratio sensor 10 detected air fuel ratio AFM by the Your Majesty and relatively more approach by bypass upstream air-fuel ratio sensor 12 detected air fuel ratio AFB according to the degree of leaking.Similarly, between two air fuel ratios, there is little difference at least.In addition, during whole oxygen evolution in being stored in catalyzer, the output signal of bypass downstream air-fuel ratio sensor 13 shows the poor state with predeterminated level, and the target engine air fuel ratio changes back to chemically correct fuel in this stage.

As mentioned above, the output signal based on swim air-fuel ratio sensor 10 and bypass upstream air-fuel ratio sensor 12 from the Your Majesty can judge whether to exist any leakage.With respect to the chemically correct fuel between poor state or rich state, after between poor state or rich state, changing, can carry out this judgement in the air fuel ratio of motor.More specifically, can use the variation timing of detected air fuel ratio or the difference of detected air fuel ratio (hereinafter explanation) to diagnose.

In other words, represent leakiness in order to use digital value, preferably in the predetermined period of time T after the variation of target engine air fuel ratio, definite mean value (AVAFM) of being swum the air fuel ratio AFM of air-fuel ratio sensor 10 detections by the Your Majesty is also determined the mean value (AVAFB) by the air fuel ratio AFB of bypass upstream air-fuel ratio sensor 12 detections.Therefore, above-mentioned Diagnostic parameters can be defined as poor between the mean value, i.e. AVAFM-AVAFB.Then Diagnostic parameters is compared with predetermined threshold value L.Can pre-determine threshold value L according to the leakiness that will detect.Be used to detect diagnosis if desired, should threshold value be set to bigger value (yet it is wrong to adopt bigger threshold value that more detection may take place) than the leakage of low degree.In addition, period of time T can be set, for example comprise the whole time cycle during the target engine air fuel ratio is in poor state, or only comprise the part of whole time cycle.

Use the diagnosis of Diagnostic parameters that following effect is provided based on detected air fuel ratio.The broadband air-fuel ratio sensor even very little air fuel ratio is changed also can very sensitive scope in, its output signal even can be in response to change (, seeing Fig. 5) immediately without any very little variation that leak, exhaust air-fuel ratio even in the downstream of catalyzer.Therefore, may be difficult to only regularly carry out diagnosis based on variation of output signals.Yet whether when according to flow channel switching valve 5 during the difference of Leak testtion between air fuel ratio, the mean value of detected air fuel ratio is particularly useful as Diagnostic parameters in predetermined interval.Therefore, and only use and compare with one group of time difference of putting according to changing timing method, the precision of diagnosis can be enhanced.

As mentioned above, with respect to the 3rd embodiment,, can easily diagnose any leakage of flow channel switching valve 5 by using traditional air- fuel ratio sensor 10,11,12 and 13 of setting in addition for traditional air-fuel ratio feedback control institute.Therefore, the sensor that need not add also can be avoided because the discharging of caused unnecessary poisonous exhaust such as the seal defect of flow channel switching valve 5.

In addition, oxygen can be stored in fully in the catalyzer up to the state of reaching capacity, maybe catalyzer can be remained on anaerobic state is rich state with respect to chemically correct fuel from poor change of state up to air fuel ratio, and vice versa.Owing to can maximize the difference between the detected air fuel ratio like this, therefore can improve the precision of diagnosis.In the 3rd embodiment, after the output signal from bypass downstream air-fuel ratio sensor 13 shows poor state, provide the reasonable time delay, the air fuel ratio of motor has been initially set to poor state, thereby increased the amount of the oxygen in the catalyzer that is stored in bypass catalytic converter 8.Similarly, catalyzer can be in complete saturation state.In addition, do not discharge the HC that does not purify, up to oxygen saturation.

Yet when the air fuel ratio of motor was initially set to rich state, the amount that is stored in the oxygen in the catalyzer reduced.In addition, after engine air-fuel ratio was set to poor state, the oxygen of introducing catalyzer still kept being stored in the catalyzer.Therefore, if there is no leak, then the Your Majesty swims air-fuel ratio sensor 10 show the poor state that is changed to after a time lag.If the Your Majesty swims air-fuel ratio sensor 10 and is changed to poor state apace, then exist and leak.

Because the oxygen capacity of the catalyzer in the bypass catalytic converter 8 is depended in above diagnosis, if because the deterioration of catalyzer reduces oxygen capacity, then this diagnosis may be affected.Therefore, although threshold value L can be constant value, it is helpful adjusting threshold value according to the degradation of catalyzer, thereby has improved the precision of diagnosis.

Fig. 6 is the sequential chart that the method for optimizing of the catalyst degradation degree that is used to diagnose bypass catalytic converter 8 is shown.Under the situation of opening of flow channel switching valve 5, carry out this diagnostic method.Can open flow channel switching valve 5 forcibly for the deterioration of diagnosing catalyzer.In addition, under the situation of opening of flow channel switching valve 5, the target air-fuel ratio of internal-combustion engine 1 is instantaneous to be rich state from poor change of state.Measurement time difference Δ T then.Time difference Δ T refers to swim the variation of air-fuel ratio sensor 10 detected air fuel ratio AFM states and by the difference between the time of the variation of bypass downstream air-fuel ratio sensor 13 detected air fuel ratio AFB states by the Your Majesty.If the air fuel ratio of motor is set to rich state, then swims air-fuel ratio sensor 10 detected air fuel ratio AFM and show rich state immediately by the Your Majesty.This is because flow channel switching valve 5 is in open mode, and shows rich state because the oxygen capacity of catalyzer causes being changed to after a time lag by bypass downstream air-fuel ratio sensor 13 detected air fuel ratio AFB (being also referred to as the 3rd parts of the exhaust air-fuel ratio in the downstream that is used to detect bypass catalytic converter 8).Therefore, do not have deterioration if bypass catalytic converter 8 is relatively new, then Δ T is very big the time difference.Along with the increase of degradation, the time difference, Δ T diminished.Therefore, as shown in Figure 7, can determine the degradation of catalyzer according to time difference Δ T.In addition, for example, by using the variation of the air fuel ratio during so-called " fuel cut-off and recovery " handled, can measure the degradation of catalyzer, wherein, fuel shutoff between deceleration period recovers after fuel shutoff.

With reference to figure 8, for example can determine threshold value L in addition by the degradation that uses catalyzer.Consequently, can adjust the degradation that threshold value L reflects catalyzer.Therefore, can accurately carry out leak diagnostics.As long as be in the diagnosis of carrying out the catalyst degradation degree under the situation of opening at flow channel switching valve 5, can judge accurately whether flow channel switching valve 5 leakage has taken place.This is because the state opened of valve can make the degradation of catalyzer can be measured and be not subjected to the influence of any leakage.In addition, can judge to leak whether take place based on the degradation of the catalyzer that measures.Although in Fig. 7 and Fig. 8, schematically show linear performance, also can predict nonlinear characteristics.In addition, also can use the degradation of other method diagnosis catalyzer.

In the third embodiment of the present invention, emission control system comprises the bypass exhaust passage 7 that is arranged on the main exhaust circulation road upstream of leading to main catalytic converter 4.Bypass exhaust passage 7 is led to bypass catalytic converter 8.Be used to stop the flow channel switching valve 5 of blast air to be arranged on the upstream of main exhaust circulation road.In addition, cleaning system comprises: the first air fuel ratio detection part is used to detect the air fuel ratio of exhaust of the upstream of bypass catalytic converter 8; The second air fuel ratio detection part is used to detect the air fuel ratio of the exhaust of main catalytic converter 4 upstreams; The air fuel ratio controlling component is used for being in when closing situation when flow channel switching valve 5, changes the air fuel ratio of motor between with respect to the poor state of chemically correct fuel and rich state instantaneously; And deagnostic package, be used for after the transient change of the air fuel ratio of motor, based on by the detected air fuel ratio of the first and second air fuel ratio detection parts, whether diagnosis flow channel switching valve 5 exists any leakage.

When having kept making the required grace time of oxygen saturation in the bypass catalytic converter 8, the transient change of the air fuel ratio of motor is preferably from poor state to rich state.

In emission control system,, preferably will all introduce bypass exhaust passage 7 also by bypass catalytic converter 8 from the exhaust of motor 1 when flow channel switching valve 5 is in when closing situation according to the 3rd embodiment.Yet, when flow channel switching valve 5 is in when opening situation, because poor, most ofly preferably avoid bypass exhaust passage 7 from the exhaust of motor 1 with respect to the big flow resistance of exhaust passage 3.

When flow channel switching valve 5 is set to be in when closing situation, can be by changing the air fuel ratio of motor, for example from poor state to rich state, carry out the diagnosis of whether leaking about flow channel switching valve 5.In this case, according to the oxygen capacity of bypass catalytic converter 8, the excessive oxygen during the poor state of engine air-fuel ratio is stored in the catalyzer.Yet, when the air fuel ratio of motor is set to rich state, discharging oxygen.Therefore, although the air fuel ratio of motor is set to rich state, as long as flow channel switching valve 5 does not leak, because the influence of discharging oxygen does not show rich state immediately by the detected air fuel ratio of the second air fuel ratio detection part.In other words, poorer relatively by the air fuel ratio of the detected exhaust of the second air fuel ratio detection part than the air fuel ratio that is right after the motor after the air fuel ratio of motor changes.Yet, when flow channel switching valve 5 leaks, because the state of the relative rich of the exhaust of leaking, by the air fuel ratio of the detected exhaust of the second air fuel ratio detection part even can be poorer.Therefore, by using these factors, can judge the degree of leakage and this leakage of flow channel switching valve.When the air fuel ratio of motor is made as when poor from richness, the oxygen capacity of bypass catalytic converter 8 also may influence the diagnosis to leaking.

In the third embodiment of the present invention, after the transient change of the air fuel ratio of motor, leak according to judging whether by the difference between the detected average air-fuel ratio of the first and second air fuel ratio detection parts to exist.

The catalyst degradation degree may influence oxygen capacity.Therefore, preferably be provided for measuring the catalyst degradation detection parts of the degradation of catalyzer.This makes and can proofread and correct or adjust leak diagnostics according to the degradation of catalyzer.

For example, when carrying out this diagnosis, can revise threshold value according to the degradation of catalyzer by the difference between comparison average air-fuel ratio and the threshold value.Do like this, can improve the precision of diagnosis.

According to the 3rd embodiment, judge in early days whether flow channel switching valve 5 leaks to help avoid with being discharged in the air of not purifying.

In addition, adjust diagnosis and can improve the precision of diagnosis with the degradation that reflects catalyzer.

Next, the method for whether leaking about fourth embodiment of the present invention explanation diagnosis flow channel switching valve 5.The 4th embodiment's vent systems is identical with first embodiment's vent systems, and the exhaust passage of vent systems is identical with the configuration shown in Fig. 1 with the configuration of control system.In the 4th embodiment, bypass downstream air-fuel ratio sensor 13 is set to the first air fuel ratio detection part, and the Your Majesty swims air-fuel ratio sensor 10 and is set to the second air fuel ratio detection part.The Your Majesty swims air-fuel ratio sensor 10 and is installed on the part of the main exhaust circulation road between junction point 9 and the main catalytic converter 4.Sensor 10 is used to detect the air fuel ratio of exhaust that bypass blast air passage is connected to junction point 9 downstreams of main exhaust circulation road.Preferably, bypass upstream air-fuel ratio sensor 12 comprises the broadband air-fuel ratio sensor, and three air- fuel ratio sensors 10,11 and 13 comprise lambda sensor.In addition, in the 4th embodiment, although the air fuel ratio of motor can be between rich state and poor state transient change, the variation from poor state to rich state only is described.

In the 4th embodiment, diagnostic process is identical with diagnostic process among second embodiment.In addition, it is identical with flow chart shown in Figure 4 the relevant flow chart of diagnostic process of present embodiment to be shown.

Fig. 9 as the sequential chart of the diagnosis that the 4th embodiment is shown illustrates: the output signal O2M that the output signal O2B of the variation of the target air-fuel ratio of internal-combustion engine, bypass downstream air-fuel ratio sensor 13 and Your Majesty swim air-fuel ratio sensor 10 and by bypass upstream air-fuel ratio sensor 12 detected air fuel ratios.Situation when in addition, Fig. 9 shows flow channel switching valve 5 and leaks (hereinafter explanation).As mentioned above, in order to diagnose leakage, the target engine air fuel ratio is changed to poor state forcibly from chemically correct fuel, transient change is rich state then.Then, because flow channel switching valve 5 is closed, therefore, blast air is crossed bypass exhaust passage 7, and during poor state, oxygen is stored in the catalyzer of bypass catalytic converter 8.So far, the output signal O2B of bypass downstream air-fuel ratio sensor 13 that is arranged on the downstream of bypass catalytic converter 8 becomes after a time lag and shows poor state.In addition, bypass upstream air-fuel ratio sensor 12 begins to show the poor state of exhaust air-fuel ratio immediately with respect to the air fuel ratio of motor.In addition, in the 4th embodiment, after the signal O2B of bypass downstream air-fuel ratio sensor 13 showed poor state, the target engine air fuel ratio was changed to rich state with a time lag.

When the target engine air fuel ratio when poor change of state is rich state, begin immediately to be changed to by the bypass upstream air-fuel ratio sensor 12 detected air fuel ratios of the upstream that is arranged on bypass catalytic converter 8 and show rich state.Because be stored in the downstream that oxygen in the bypass catalytic converter 8 is discharged into bypass catalytic converter 8, so flip displays is rich state after the time lag of the output signal O2B of bypass downstream air-fuel ratio sensor 10 after the air fuel ratio of motor becomes rich state.In addition, unless flow channel switching valve 5 leaks exhausts, the output signal O2M that the Your Majesty swims air-fuel ratio sensor 10 almost simultaneously flip displays be rich state.For example, if ignore distance from the relief opening 2 of motor 1 to bypass downstream air-fuel ratio sensor 13 and swim to the Your Majesty from the relief opening 2 of motor 1 air-fuel ratio sensor 10 distance difference, if then do not leak, output signal O2B and O2M the two simultaneously from showing that rich state turnover is for showing poor state.

Yet if for example because the seal defect of valve body etc., exhaust is leaked by flow channel switching valve 5, and a part of exhaust arrives that the Your Majesty swims air-fuel ratio sensor 10 and not by bypass catalytic converter 8.Consequently, as shown in Figure 9, the Your Majesty swims the rich state of output signal O2M flip displays of air-fuel ratio sensor 10.That is, when leaking when taking place really, the difference that the output signal O2B that the Your Majesty swims the output signal O2M of air-fuel ratio sensor 10 and bypass downstream air-fuel ratio sensor 13 is changed between the timing of rich state increases.In addition, when the output signal O2B of bypass downstream air-fuel ratio sensor 13 reached predeterminated level (corresponding to poor state) and be stored in whole oxygen discharging in the catalyzer, target air-fuel ratio turned back to chemically correct fuel.

As mentioned above, the output signal based on the Your Majesty swims air-fuel ratio sensor 10 and bypass upstream air-fuel ratio sensor 12 can judge whether to occur leaking.Can be in engine air-fuel ratio with respect to after the transient change of the chemically correct fuel between poor state and the rich state between poor state and rich state, carrying out this judgement.More specifically, can use the time difference between the variation of exporting difference and output to carry out diagnosis (hereinafter explanation).

In the 4th embodiment, the judgement of the reference potential V0 time point (shown in Figure 9) when poor state turnover is rich state uses numerical value to represent leakiness in the middle of can crossing over respectively based on the output signal O2B of output signal O2M that the Your Majesty is swum air-fuel ratio sensor 10 and bypass downstream air-fuel ratio sensor 13.Time difference Δ T (that is, the variation of output signal O2B is with respect to the time lag of the variation of output signal O2M) between two time points is set to Diagnostic parameters.Then, with Diagnostic parameters be used to judge that the predetermined threshold value L of leakage compares.Pre-determine threshold value L according to the leakiness that will detect.If want to detect the diagnosis that slight extent is leaked, threshold value can be made as lower (yet when threshold value is low, the more mistake that detects may take place).Therefore, when the time difference, Δ T was big, is judged as leakage has taken place.

Diagnosis based on time difference Δ T has following effect.Because the output according to concrete situation (that is, poor state or rich state) lambda sensor changes apace, so when the leakage of reality takes place, also may easily detect big output difference.This is because the variation of the output that the relative position of the sensor in the vent systems (that is, relative upstream or downstream) is caused is regularly mutually internally inconsistent.Yet as mentioned above, whether time difference Δ T provides the Diagnostic parameters that more clearly illustrates for leaking.Therefore, compare with using output difference, diagnostic accuracy can further improve.

In the 4th embodiment, whether the traditional air- fuel ratio sensor 10,11,12 and 13 that is used for the feedback control of air fuel ratio by use can easily diagnose flow channel switching valve 5 to leak.Therefore, do not have additional sensor, can avoid yet because the discharging of caused unnecessary poisonous exhaust such as the seal defect of flow channel switching valve 5.

In addition, oxygen can fully be stored in the catalyzer up to the state of reaching capacity, or catalyzer can be maintained at anaerobic state be rich state with respect to the chemically correct fuel between poor state and rich state from poor change of state up to air fuel ratio, vice versa.Owing to can maximize the difference between the detected air fuel ratio like this, therefore can improve the precision of diagnosis.In the 4th embodiment, after the output signal of bypass downstream air-fuel ratio sensor 13 shows poor state, provide the reasonable time delay, the air fuel ratio of motor has been initially set to poor state, thereby increased the amount of the oxygen in the catalyzer that is stored in bypass catalytic converter 8.Similarly, catalyzer can be in complete saturation state.In addition, do not discharge the HC that does not purify, up to oxygen saturation.

Yet when engine air-fuel ratio was initially set to rich state, the amount that is stored in the oxygen in the catalyzer reduced.In addition, after the air fuel ratio of motor was set to poor state, the oxygen of introducing catalyzer still kept being stored in the catalyzer.Therefore, if there is no leak, then the Your Majesty swims air-fuel ratio sensor 10 show the poor state that is changed to after a time lag.If the Your Majesty swims air-fuel ratio sensor 10 and is changed to poor state apace, then exist and leak.

Because the oxygen capacity (being similar to second embodiment) of the catalyzer in the bypass catalytic converter 8 is depended in above diagnosis, if because the deterioration of catalyzer reduces oxygen capacity, then this diagnosis may be affected.Therefore, although threshold value L can be constant value, be useful according to the horizontal adjustemt threshold value of the degradation of catalyzer, improved the precision of diagnosis thus.

Can use with reference to second embodiment's of figure 6 method diagnostic method as the catalyst degradation degree of bypass catalytic converter 8.

For example, can determine threshold value L based on the degradation of catalyzer.Consequently, threshold value L can reflect the degradation of catalyzer.Therefore, can accurately carry out the diagnosis of leakage.As long as be in the diagnosis of carrying out the catalyst degradation degree under the state of opening, just can judge accurately whether flow channel switching valve 5 leaks at flow channel switching valve 5.This is because the open mode of valve can make the influence that the measurement of catalyst degradation degree is not leaked.In addition, can judge to leak whether take place based on the catalyst degradation degree that records.In addition, can use other method to diagnose the degradation of catalyzer.

In the fourth embodiment of the present invention, emission control system comprises the bypass exhaust passage 7 that is arranged on the main exhaust circulation road upstream of leading to main catalytic converter 4.Bypass exhaust passage 7 is led to bypass catalytic converter 8.Be used to stop the flow channel switching valve 5 of blast air to be arranged on the upstream of main exhaust circulation road.In addition, cleaning system comprises: the first air fuel ratio detection part is used to detect the exhaust air-fuel ratio in bypass catalytic converter 8 downstreams; The second air fuel ratio detection part is used to detect the exhaust air-fuel ratio of main catalytic converter 4 upstreams; The air fuel ratio controlling component is used for being in when closing situation when flow channel switching valve 5, changes engine air-fuel ratio with respect to chemically correct fuel between poor state and rich state instantaneously; And deagnostic package, be used for after the transient change of the air fuel ratio of motor, based on by the detected air fuel ratio of the first and second air fuel ratio detection parts, whether diagnosis flow channel switching valve 5 exists any leakage.

When having kept making the saturated required time enough of oxygen in the bypass catalytic converter 8, the transient change of the air fuel ratio of motor preferably from poor state to rich state.

In emission control system,, preferably will all introduce bypass exhaust passage 7 also by bypass catalytic converter 8 from the exhaust of motor 1 when flow channel switching valve 5 is in when closing situation according to the 4th embodiment.Yet, when flow channel switching valve 5 is in when opening situation, because poor, most ofly preferably avoid bypass exhaust passage 7 from the exhaust of motor 1 with respect to the bigger flow resistance of exhaust passage 3.

When flow channel switching valve 5 is set to be in when closing situation, can carry out the diagnosis of whether leaking by for example air fuel ratio from poor state to rich change of state motor about flow channel switching valve 5.In this case, according to the oxygen capacity of bypass catalytic converter 8, the excessive oxygen during engine air-fuel ratio is in poor state is stored in the catalyzer.Yet when the air fuel ratio of motor is set to rich state, discharging oxygen.Therefore, although the air fuel ratio of motor is set to rich state, as long as flow channel switching valve 5 does not leak, because the influence of discharging oxygen does not show rich state immediately by the detected air fuel ratio of the first and second air fuel ratio detection parts.In other words, poorer relatively by the air fuel ratio of the detected exhaust of the second air fuel ratio detection part than the engine air-fuel ratio that is right after after engine air-fuel ratio changes.Yet, when flow channel switching valve 5 leaks, because the exhaust of leaking is in the state of relative rich, therefore by the detected exhaust air-fuel ratio of the second air fuel ratio detection part even may be poorer.Therefore, by using these factors, can judge the degree of leakage and this leakage of flow channel switching valve.When engine air-fuel ratio is made as when poor from richness, the oxygen capacity of bypass catalytic converter 8 also may influence the diagnosis to leaking.

Preferably, when flow channel switching valve 5 is set to be in closed condition, can be by changing the air fuel ratio of motor, for example from poor state to rich state, carry out the diagnosis of flow channel switching valve 5.In this case, because the oxygen capacity of bypass catalytic converter 8, the excessive oxygen during engine air-fuel ratio is in poor state is stored in the catalyzer.Yet when the air fuel ratio of motor becomes rich state, discharging oxygen.Therefore, although the air fuel ratio of motor becomes rich state, do not become rich state immediately by the detected air fuel ratio of the first and second air fuel ratio detection parts.As long as flow channel switching valve 5 does not leak, Here it is because the oxygen discharging is caused.If the whole oxygen that are stored in the catalyzer are consumed, be rich state in about identical time showing then by the detected air fuel ratio of the first and second air fuel ratio detection parts.Yet, when flow channel switching valve 5 leaks,, therefore show poor state immediately by the detected exhaust air-fuel ratio of the second air fuel ratio detection part because the exhaust of leaking is in rich state.Therefore, based on these factors, can judge whether flow channel switching valve 5 leaks and the degree of this leakage.When the air fuel ratio of motor becomes when poor from richness, the influence of leakage may since oxygen capacity cause.

In the 4th embodiment, after instantaneous change engine air-fuel ratio,, carry out the judgement of whether leaking based on by the difference between the variation regularly of the detected air fuel ratio of the first and second air fuel ratio detection parts.

The catalyst degradation degree may influence oxygen capacity.Therefore, preferably be provided for measuring the catalyst degradation detection parts of the degradation of catalyzer.This makes and can proofread and correct or adjust leak diagnostics according to the degradation of catalyzer.

For example, after the air fuel ratio transient change of motor, when by compare threshold and by the variation of the detected air fuel ratio of the first air fuel ratio detection part regularly when carrying out leak diagnostics by the variation time lag regularly of the detected air fuel ratio of the second air fuel ratio detection part, can revise threshold value according to the degradation of catalyzer.Similarly, can improve the precision of diagnosis.

According to the 4th embodiment, judge in early days whether flow channel switching valve 5 leaks to avoid with being discharged in the air of not purifying.

In addition, adjust the degradation of diagnosis, can improve the precision of diagnosis with the reflection catalyzer.

Though by disclosing the present invention with reference to certain preferred embodiment, be possible to described embodiment's various deformation, change and variation, and do not break away from by claims and defined the field of the invention of equivalency range and scope.Therefore, mean invention and be not limited to described embodiment, and have by the defined four corner of the language of claims.

According to the 119th of united states patent law, the application requires the preference of Japanese patent application that the Japanese patent application submitted on March 15th, 2006 2006-070232 number and two submit on March 16th, 2006 2006-072001 number and 2006-072004 number.Here, the full content of these three Japanese patent applications is incorporated this paper by reference into.

Claims (35)

1. equipment that is used for the emission control system of disgnosizing internal combustion engine, described equipment comprises:

Main exhaust passageway;

Main catalytic converter, it is set in the described main exhaust passageway;

Bypass exhaust passage, itself and described main exhaust passageway intercommunication fluid, thus make described main exhaust passageway at point of branching that described bypass exhaust passage is told from described main exhaust passageway with converge part bypass between the junction point of described main exhaust passageway in bypass exhaust passage described main catalytic converter upstream side, described;

The bypass catalytic converter, it is set in the described bypass exhaust passage;

Be arranged in the described part of described main exhaust passageway, be used for opening or closing the valve of the described part of described main exhaust passageway;

First sensor, it is arranged on first signal that is illustrated in first air fuel ratio of the exhaust of flowing in the described bypass exhaust passage in the described bypass exhaust passage with output;

Second sensor, it is arranged in the described main exhaust passageway secondary signal of second air fuel ratio that flows into the exhaust of described main catalytic converter with the output expression; And

Controller, it receives described first and second signals, and described controller judges based on described first and second signals whether be in the described valve of closing setting makes exhaust gas leakage arrive the described part of described main exhaust passageway.

2. equipment according to claim 1 is characterized in that, described first sensor detects described first air fuel ratio of exhaust of the upstream of described bypass catalytic converter.

3. equipment according to claim 2 is characterized in that, described second air fuel ratio of the exhaust in the downstream of the described valve of described second sensor.

4. equipment according to claim 2, it is characterized in that, described first signal indication is by the rich state of described first air fuel ratio of the exhaust of described bypass exhaust passage and the variation between the poor state, and described secondary signal is represented by the rich state of described second air fuel ratio of the exhaust of described main exhaust passageway and the variation between the poor state.

5. equipment according to claim 4, it is characterized in that, judge be in described described valve of closing setting whether leak described first signal that comprises the rich state of determining described first air fuel ratio of expression and the variation between the poor state and represent the rich state of described second air fuel ratio and the described secondary signal of the variation between the poor state between time lag, described time lag is corresponding with the cyclically-varying of the engine air-fuel ratio that offers internal-combustion engine.

6. equipment according to claim 5 is characterized in that, judges whether be in described described valve of closing setting leaks and comprise:

When described time lag is not more than threshold value, is judged as to exist and leaks; And

When described time lag during, be judged as and do not have leakage greater than described threshold value.

7. equipment according to claim 5 is characterized in that, judges whether be in described described valve of closing setting leaks and comprise:

When described time lag during, be judged as to exist and leak less than first threshold;

When described time lag during, be judged as and do not have leakage greater than second threshold value; And

When described time lag is in prespecified range between described first threshold and described second threshold value, be judged as described bypass catalytic converter deteriorate.

8. equipment according to claim 4, it is characterized in that, judge whether be in described described valve of closing setting leaks and comprise: more described first signal be in one of the described rich state of described first air fuel ratio and poor state first at interval and described secondary signal be in second interval of one of the described rich state of described second air fuel ratio and poor state, the described rich state and the variation between the poor state of described first and second air fuel ratios are corresponding with the cyclically-varying of the engine air-fuel ratio that offers internal-combustion engine.

9. equipment according to claim 8 is characterized in that, judges whether be in described described valve of closing setting leaks and comprise:

Be substantially equal at interval described second at interval the time when described first, be judged as to exist and leak; And

When described first at interval less than described second at interval the time, be judged as and do not have leakage.

10. equipment according to claim 8 is characterized in that, judges whether be in described described valve of closing setting leaks and comprise:

Be substantially equal at interval described second at interval the time when described first, be judged as to exist and leak;

When described first and second the differences between at interval during, be judged as and do not have leakage greater than threshold value; And

When the difference between described first and second intervals is not more than described threshold value, be judged as described bypass catalytic converter deteriorate.

11. equipment according to claim 4, it is characterized in that, judge whether be in described described valve of closing setting leaks and comprise and periodically change the engine air-fuel ratio that offers internal-combustion engine that described engine air-fuel ratio changes between poor state and rich state with respect to the chemically correct fuel engine air-fuel ratio.

12. equipment according to claim 11 is characterized in that, reponse system comprises described first sensor and described controller, and described reponse system makes the engine air fuel ratio periodic variation between richness, poor state that offers described internal-combustion engine.

13. equipment according to claim 12 is characterized in that, described reponse system is set the chemically correct fuel level of the described engine air fuel ratio that offers described internal-combustion engine.

14. equipment according to claim 11 is characterized in that, feedforward system makes the engine air fuel ratio periodic variation between richness, poor state that offers described internal-combustion engine.

15. equipment according to claim 2, it is characterized in that, described controller is carried out transient change between the rich or poor state, the engine air fuel ratio, and described first signal and described secondary signal are represented described first air fuel ratio and described second air fuel ratio after the described transient change respectively.

16. equipment according to claim 15, it is characterized in that, described first signal indication is by the mean state of detected described first air fuel ratio of described first sensor, described secondary signal represent by described second sensor to the mean state of described second air fuel ratio, and the scheduled period after changing described engine air-fuel ratio determine the mean state of described first and second air fuel ratios.

17. equipment according to claim 15 is characterized in that, described second air fuel ratio of the exhaust in the downstream of the described bypass exhaust passage of described second sensor.

18. equipment according to claim 15 is characterized in that, the described engine air fuel ratio of described transient change is to described rich state from described poor state.

19. equipment according to claim 18 is characterized in that, the transient change of described engine air-fuel ratio occurs in and is used for making the approaching oxygen-saturated long enough of described bypass catalytic converter after the time.

20. equipment according to claim 15, it is characterized in that, described controller is determined the catalyst degradation degree of described bypass catalytic converter, and described controller based on the described catalyst degradation degree adjustment of described bypass catalytic converter to being in the judgement whether described described valve of cutting out setting leaks.

21. equipment according to claim 20 is characterized in that, also comprises:

Be arranged on the 3rd sensor in the described bypass exhaust passage, the 3rd air fuel ratio of the exhaust in the downstream of the described bypass catalytic converter of described the 3rd sensor, the 3rd signal of described the 3rd air fuel ratio of described the 3rd sensor output expression, described controller receives described the 3rd signal, and, determine described catalyst degradation degree with the variation of described engine air-fuel ratio that is changing corresponding described first and the 3rd air fuel ratio based on be in described opening when being provided with when described valve.

22. equipment according to claim 20, it is characterized in that, described first signal indication is by the mean state of detected described first air fuel ratio of described first sensor, described secondary signal represent by described second sensor to the mean state of described second air fuel ratio, determine the mean state of described first and second air fuel ratios in the scheduled period that described engine air-fuel ratio changes, judge that whether be in described described valve of closing setting leaks and comprise threshold value and difference between described first and second signals of representing average air-fuel ratio are compared, and revises described threshold value based on the catalyst degradation degree of described bypass catalytic converter.

23. equipment according to claim 1, it is characterized in that, described first sensor detects described first air fuel ratio of exhaust in the downstream of described bypass catalytic converter, described second air fuel ratio of the exhaust in the downstream of the described bypass exhaust passage of described second sensor.

24. equipment according to claim 23, it is characterized in that, described controller is carried out the transient change of engine air fuel ratio between rich or poor state, described first signal and described secondary signal are represented first air fuel ratio and second air fuel ratio after the described transient change respectively.

25. equipment according to claim 24, it is characterized in that, judge whether leak comprise judgement at described first signal list illustrate the rich state of described first air fuel ratio and variation poor state between and described secondary signal express the rich state of described second air fuel ratio and variation poor state between between whether time of origin poor, the described time difference is corresponding with the described engine air-fuel ratio that is changing if being in described described valve of closing setting.

26. equipment according to claim 24 is characterized in that, the described engine air fuel ratio of described transient change is to described rich state from described poor state.

27. equipment according to claim 26 is characterized in that, the transient change of described engine air-fuel ratio occurs in and is used for making the approaching oxygen-saturated long enough of described bypass catalytic converter after the time.

28. equipment according to claim 24, it is characterized in that, described controller is determined the catalyst degradation degree of described bypass catalytic converter, and described controller based on the described catalyst degradation degree adjustment of described bypass catalytic converter to being in the judgement whether described described valve of cutting out setting leaks.

29. equipment according to claim 28 is characterized in that, also comprises:

Be arranged on the 3rd sensor in the described bypass exhaust passage, the 3rd air fuel ratio of the exhaust of the upstream of the described bypass catalytic converter of described the 3rd sensor, the 3rd signal of described the 3rd air fuel ratio of described the 3rd sensor output expression, described controller receives described the 3rd signal, and, determine described catalyst degradation degree with the variation of described engine air-fuel ratio that is changing corresponding described first and the 3rd air fuel ratio based on be in described opening when being provided with when described valve.

30. equipment according to claim 28 is characterized in that, judges whether be in described described valve of closing setting leaks and comprise:

Judgement illustrates the rich state of described first air fuel ratio and the variation between the poor state and described secondary signal at described first signal list and expresses whether time of origin is poor between the rich state of described second air fuel ratio and the variation between the poor state, and the described time difference is corresponding with the described engine air-fuel ratio that is changing;

Compare threshold and described time difference; And

Described catalyst degradation degree based on described bypass catalytic converter is revised described threshold value.

31. a method that is used for the emission control system of disgnosizing internal combustion engine, described method comprises:

Flow through first air fuel ratio of exhaust of the main exhaust passageway that comprises main catalytic converter of detection;

Flow through second air fuel ratio of exhaust of bypass exhaust passage of detection, described bypass exhaust passage and described main exhaust passageway intercommunication fluid, thereby make described main exhaust passageway at point of branching that described bypass exhaust passage is told from described main exhaust passageway with converge part bypass between the junction point of described main exhaust passageway in bypass exhaust passage described main catalytic converter upstream side, described, described bypass exhaust passage comprises the bypass catalytic converter;

Prevent that with valve exhaust is mobile along described main exhaust passageway; And

Based on described first and second air fuel ratios, judge whether exhaust leaks by described valve.

32. method according to claim 31, it is characterized in that, described first air fuel ratio that detects exhaust comprises the air fuel ratio that detects the exhaust that enters described bypass catalytic converter, and described second air fuel ratio that detects exhaust comprises the air fuel ratio that detects the exhaust that enters described main catalytic converter.

33. method according to claim 31 is characterized in that, also comprises:

Determine the deterioration of described bypass catalytic converter.

34. method according to claim 33 is characterized in that, also comprises: use valve to allow exhaust to flow along described main exhaust passageway.

35. method according to claim 33 is characterized in that, also comprises: the 3rd air fuel ratio that detects the exhaust of leaving described bypass catalytic converter.

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