CN100520033C - Catalyst deterioration detecting apparatus - Google Patents

Abstract

The invention provides a catalyst deterioration detection device, which almost cannot cause the depravation of discharge characteristics and can detect the deterioration degree of the catalyst with high precision. The oxygen amount (OS) flowing into a ternary catalyst (14a) can be calculated according to the detected intake air flow (GAIR) and the output of an oxygen concentration transducer (17) at an upstream side of the ternary catalyst (14a). The dense/thin switchover control (disturbance) of the air-fuel ration can be done as per the comparative result of the oxygen amount (OS) and a target value (OSOBJR and OSOBJL). If the air-fuel ratio of the output (SVO2) of an O2 transducer (18) at a downstream side changes in large range in the disturbance, the ternary catalyst (14a) is determined to be deteriorated. If the ternary catalyst (14a) is normal, the output of the O2 transducer is hardly changed through the setting of the target value (OSOBJR and OSOBJL) properly.

Description

Catalyst deterioration detecting apparatus

Technical field

The present invention relates to detect the catalyst deterioration detecting apparatus of the degradation of the exhaust gas purification catalyst in the vent systems that is arranged on internal-combustion engine.

Background technique

The known in the past technology that has judgement to be arranged on exhaust gas purification catalyst (being designated hereinafter simply as " the catalyzer ") deterioration in the internal combustion engine exhaust system.A kind of the 1st time of measurement CB and/or the 2nd time CA are for example disclosed in patent documentation 1, and judge the device of the deterioration of catalyzer according to the 1st time CB and/or the 2nd time CA, wherein, the 1st time was from the air fuel ratio that offers the mixed gas of internal-combustion engine is switched to the moment of dense side from rare side of comparing with chemically correct fuel, be changed to time of the value of the dense air fuel ratio of expression to the output of the air-fuel ratio sensor (oxygen concentration sensor) in the downstream side that is arranged on catalyzer, the 2nd time was from air fuel ratio is switched to the moment of rare side from the dense side of comparing with chemically correct fuel, be changed to the time of the value of the rare air fuel ratio of expression to the output of the air-fuel ratio sensor in the downstream side that is arranged on catalyzer.

2-No. 207159 communiques of [patent documentation 1] Japanese kokai publication hei

In above-mentioned existing apparatus, by the output that makes the air-fuel ratio sensor that is arranged on the catalyzer downstream side change specified value with on detect the degradation of catalyzer, even thereby under the situation that normal (not deterioration) catalyzer is judged, the output that also must make air fuel ratio change to the downstream side air-fuel ratio sensor changes the above degree of specified value.Therefore, there is following problem, that is: owing to carrying out the time lengthening that degradation worsens discharge characteristic.

Summary of the invention

The present invention is conceived to this point and makes, and the object of the present invention is to provide a kind of catalyst deterioration detecting apparatus that makes discharge characteristic worsen, can detect accurately the degradation of catalyzer hardly.

In order to achieve the above object, one of the present invention's catalyst deterioration detecting apparatus, its detection is arranged on the degradation of the exhaust gas purification catalyst (14a) in the vent systems (13) of internal-combustion engine (1), it is characterized in that, this catalyst deterioration detecting apparatus has: intake air flow detection unit (7), and it detects the intake air flow (GAIR) of above-mentioned internal-combustion engine; The 1st oxygen concentration sensor (17), it is arranged on the upstream side of above-mentioned catalyzer; The 2nd oxygen concentration sensor (18), it is arranged on the downstream side of above-mentioned catalyzer; Flow into the amount of oxygen computing unit, it is according to calculate the amount of oxygen (OS) that flows into above-mentioned catalyzer (14a) by the detected oxygen concentration (O2N) of above-mentioned the 1st oxygen concentration sensor (17) with by the detected intake air flow (GAIR) of above-mentioned intake air flow detection unit; The air fuel ratio switch control unit, it is according to flowing into the desired value (OSOBJR of amount of oxygen by above-mentioned inflow amount of oxygen (OS) and this, OSOBJL) comparative result between alternately is controlled at the air fuel ratio of the mixed gas that offers above-mentioned internal-combustion engine rare side and the dense side of comparing with chemically correct fuel; And deterioration detection unit, it detects the degradation (RESULT) of above-mentioned catalyzer according to the output (SVO2) of above-mentioned the 2nd oxygen concentration sensor in the action of above-mentioned air fuel ratio switch control unit.

The present invention's two catalyst deterioration detecting apparatus is characterised in that, in one of the present invention's catalyst deterioration detecting apparatus, (SVO2LEAN, SVO2RICH) comparative result between carries out the switching controls of above-mentioned air fuel ratio to above-mentioned air fuel ratio switch control unit with specified value according to the output (SVO2) of above-mentioned the 2nd oxygen concentration sensor.

The present invention's three catalyst deterioration detecting apparatus is characterised in that, one of the present invention or two catalyst deterioration detecting apparatus in, above-mentioned air fuel ratio switch control unit according to above-mentioned intake air flow (GAIR) calculate above-mentioned desired value (OSOBJR, OSOBJL).

The present invention's four catalyst deterioration detecting apparatus is characterised in that, in the described catalyst deterioration detecting apparatus of one of the present invention, this catalyst deterioration detecting apparatus also has the catalyst temperature detection unit (19) of the temperature (TCAT) that detects above-mentioned catalyzer, above-mentioned air fuel ratio switch control unit according to above-mentioned catalyst temperature (TCAT) calculate above-mentioned desired value (OSOBJR, OSOBJL).

The present invention's five catalyst deterioration detecting apparatus is characterised in that, in the described catalyst deterioration detecting apparatus of one of the present invention, this catalyst deterioration detecting apparatus also has: forbid the unit, it forbids that according to above-mentioned inflow amount of oxygen (OS) degradation of above-mentioned deterioration detection unit detects.

The present invention's six catalyst deterioration detecting apparatus is characterised in that, in the described catalyst deterioration detecting apparatus of one of the present invention, in above-mentioned vent systems, also be provided with exhaust gas purification catalyst (14b) in the downstream side of above-mentioned the 2nd oxygen concentration sensor (18).

The present invention's seven catalyst deterioration detecting apparatus is characterised in that, in the described catalyst deterioration detecting apparatus of one of the present invention, above-mentioned air fuel ratio switch control unit is according to the intake air flow (GAIR) and the above-mentioned desired value (OSOBJR of above-mentioned internal-combustion engine, the renewal speed (Δ KCMDR, Δ KCMDL) of the above-mentioned air fuel ratio when OSOBJL) being set in the switching of above-mentioned air fuel ratio.

The present invention's eight catalyst deterioration detecting apparatus is characterised in that, in the described catalyst deterioration detecting apparatus of one of the present invention, this catalyst deterioration detecting apparatus also has: characteristic variations detection unit, the characteristic variations parameter (VLAFFC) that its output characteristics that detects above-mentioned the 1st oxygen concentration sensor of expression changes; And correcting unit, it proofreaies and correct the output (VLAF) of above-mentioned the 1st oxygen concentration sensor according to above-mentioned characteristic variations parameter (VLAFFC); Above-mentioned inflow amount of oxygen computing unit uses by the sensor output (VLAF) after the above-mentioned correcting unit correction and calculates above-mentioned amount of oxygen (OS).

One of according to the present invention, calculate amount of oxygen in the inflow catalyst according to the oxygen concentration that is detected by the 1st oxygen concentration sensor with by the intake air flow that the intake air flow detection unit is detected, and, carry out the air fuel ratio switching controls (disturbance (perturbation) control) that the air fuel ratio that offers the mixed gas of internal-combustion engine is switched to dense side or switches on the contrary from rare side of comparing with chemically correct fuel according to the comparative result between the desired value of this inflow amount of oxygen and this inflow amount of oxygen.Then, in the air fuel ratio switching controls is carried out, detect the degradation of catalyzer according to the output of the 2nd oxygen concentration sensor.By the desired value that flows into amount of oxygen is set for, when catalyzer the 2nd oxygen concentration sensor output just often changes hardly, and the output of the 2nd oxygen concentration sensor significantly changes when catalyst degradation, thereby discharge characteristic is worsened, the moment that begins deterioration at catalyzer makes discharge characteristic worsen hardly, can promptly detect degradation.

According to the present invention two, because the switching controls of carrying out air fuel ratio according to the output value and the comparative result between the specified value of the 2nd oxygen concentration sensor, thereby catalyst degradation and flow into amount of oxygen reach desired value before under the output value of the 2nd oxygen concentration sensor situation about having changed, can prevent to make discharge characteristic to worsen.

According to the present invention three, calculate to flow into the desired value of amount of oxygen according to intake air flow.Owing to the amount of oxygen that can be accumulated in the catalyzer depends on that extraction flow is that intake air flow changes, thereby pass through according to intake air flow target setting value, the switching of air fuel ratio becomes suitable period, the degradation of catalyzer can be detected exactly, and the deterioration of discharge characteristic can be prevented reliably.

According to the present invention four, calculate to flow into the desired value of amount of oxygen according to catalyst temperature.Owing to the amount of oxygen that can be accumulated in the catalyzer depends on that catalyst temperature changes, thereby by calculating desired value according to catalyst temperature, the switching of air fuel ratio becomes suitably period, can detect the degradation of catalyzer exactly, and can prevent the deterioration of discharge characteristic reliably.

According to the present invention five, forbid that according to flowing into amount of oxygen degradation detects.When the inflow amount of oxygen that calculates increases unusually, can not carry out degradation detection accurately, thereby by forbidding that degradation detects, and can prevent the decline of testing precision.

According to the present invention six, use the catalyzer in the downstream side be arranged on the 2nd oxygen concentration sensor to carry out exhaust gas purification, thereby when the catalyzer after the deterioration being carried out degradation detect processing, can prevent the discharge of HC and NOx, can keep good discharge characteristic.

According to the present invention seven, the renewal speed of the air fuel ratio when setting the switching of air fuel ratio according to the intake air flow of internal-combustion engine and the desired value that flows into amount of oxygen.Thus, can make the air fuel ratio switching cycle is constant, and irrelevant with the variation of internal combustion engine operation state.For example when the big high loaded process of intake air flow, by reducing the renewal speed of air fuel ratio, the influence that can alleviate the response characteristic deterioration of the 2nd oxygen concentration sensor can be carried out accurately catalyst degradation and judge.On the other hand, when the little low load operation of intake air flow,, can shorten catalyst degradation and judge the needed time by improving the renewal speed of air fuel ratio.

According to the present invention eight, detect the characteristic variations parameter that the output characteristics of expression the 1st oxygen concentration sensor changes, according to the output of this characteristic variations parameter correction the 1st oxygen concentration sensor, use sensor after proofreading and correct to export to calculate catalyzer to flow into amount of oxygen.Therefore, be not subjected to the 1st oxygen concentration sensor output characteristics through the time influence that changes, can calculate amount of oxygen accurately, can carry out accurately catalyst degradation and judge.

Description of drawings

Fig. 1 is the figure that the structure of the internal-combustion engine of the catalyst deterioration detecting apparatus that comprises one embodiment of the present invention and control gear thereof is shown.

Fig. 2 is used for figure that the catalyst degradation detection method is described.

Fig. 3 is the flow chart that carries out the main flow of catalyst degradation detection.

Fig. 4 is that the disturbing signal of carrying out in the processing of Fig. 3 generates the flow chart of handling.

Fig. 5 is that the disturbing signal of carrying out in the processing of Fig. 3 generates the flow chart of handling.

Fig. 6 is the figure that is illustrated in the table of reference in the processing of Fig. 4 or Fig. 5.

Fig. 7 is the flow chart of the KCMD computing carried out in the processing of Fig. 3.

Fig. 8 is used for the sequential chart that the processing to Fig. 7 describes.

Fig. 9 is the flow chart that the deterioration judging carried out in the processing of Fig. 3 is handled.

Figure 10 is the flow chart that the deterioration judging carried out in the processing of Fig. 3 is handled.

Figure 11 is the flow chart according to the main flow of the deterioration judging processing of second embodiment of the invention.

Figure 12 be used for Comparative Examples type oxygen concentration sensor output characteristics through the time change the figure describe.

Figure 13 is the flow chart of the processing of output that carry out in the processing of Figure 11, correction proportional-type oxygen concentration sensor.

Figure 14 is used for the sequential chart that the computational methods of the parameter (VLAFFC) that the output characteristics to expression proportional-type oxygen concentration sensor changes describe.

Figure 15 is the figure that is illustrated in the table of reference in the processing of Figure 13.

Figure 16 is the flow chart of the FMCND computing carried out in the processing of Figure 11.

Figure 17 is the flow chart of the KCMD computing carried out in the processing of Figure 11.

Figure 18 is the figure that is illustrated in the table of reference in the processing of Figure 17.

Embodiment

Below, with reference to accompanying drawing embodiments of the present invention are described.

[first mode of execution]

Fig. 1 is the internal-combustion engine (hereinafter referred to as " motor ") that comprises the catalyst deterioration detecting apparatus of one embodiment of the present invention and the overall structure figure of control gear thereof, disposes closure 3 midway in the suction tude 2 of the motor 1 of for example 4 cylinders.Throttle opening (TH) sensor 4 is connected with closure 3, and the output electrical signal corresponding with the aperture of this closure 3 offers electronic control unit (hereinafter referred to as " ECU ") 5.

Fuelinjection nozzle 6 be arranged between motor 1 and the closure 3 at each cylinder and suction tude 2 do not do illustrated intake valve slightly by upstream side, each injection valve with do not make illustrated petrolift and be connected, and be electrically connected with ECU 5, according to opening time from the SC sigmal control Fuelinjection nozzle 6 of this ECU 5.

Upstream side at closure 3 is provided with the intake air flow sensor 7 that detects intake air flow GAIR.And, be provided with air inlet pressure sensor 8 that detects suction pressure PBA and the intake air temperature sensor 9 that detects intake temperature TA in the downstream side of closure 3.The testing signal of these sensors is provided for ECU 5.

Engine water temperature (TW) sensor 10 that is installed on the main body of motor 1 is made of thermistor etc., and detection of engine water temperature (coolant water temperature) TW exports corresponding temperature signal and offers ECU 5.

The crank angle position sensor 11 of the angle of swing of the bent axle of detection of engine 1 (not illustrating) is connected with ECU 5, provides the signal corresponding with the angle of swing of bent axle to ECU 5.Crank angle position sensor 11 is made up of following sensor, that is: cylinder discrimination sensor, and it is in regulation crank angle position place of the specific cylinder of motor 1 output pulse (hereinafter referred to as " CYL pulse "); The TDC sensor, the top dead center (TDC) when its suction stroke at each cylinder begins, the crank angle position (per 180 crank angle in 4 Cylinder engines) before the regulation crankshaft angles locates to export the TDC pulse; And the CRK sensor, it produces 1 pulse (hereinafter referred to as " CRK pulse ") with certain crank shaft angle cycle (for example 30 spend the cycle) shorter than TDC pulse, and CYL pulse, TDC pulse and CRK pulse are provided for ECU 5.These pulses are used for the various timing controlled of fuel injection timing, ignition timing etc., the detection of engine speed NE.

In outlet pipe 13, be provided with three-way catalyst 14a and 14b are housed in 1 catalyst elements 15 in the container.

Three-way catalyst 14a and 14b have the oxygen accumulating capability, and has a following function, that is: be set under the rare state of the higher exhaust of rare side of comparing with chemically correct fuel, oxygen concentration in the exhaust in the air fuel ratio of the mixed gas that offers motor 1, accumulate the oxygen in the exhaust, otherwise under the state that be set in the air fuel ratio of the mixed gas that offers motor 1 that the dense side compared with chemically correct fuel, oxygen concentration in the exhaust are low, HC, exhaust that the CO composition is many is dense, use the oxygen of being accumulated to come HC, CO in the oxidation exhaust.

Upstream side in catalyst elements 15 is equipped with proportional-type oxygen concentration sensor 17 (hereinafter referred to as " LAF sensor 17 "), the electrical signal that 17 outputs of this LAF sensor and oxygen concentration (air fuel ratio) in the exhaust roughly are directly proportional, and offer ECU 5.

Two-value type oxygen concentration sensor (hereinafter referred to as " O2 sensor ") 18 is installed between three-way catalyst 14a and 14b, and its testing signal is provided for ECU 5.This O2 sensor 18 has its output in the front and back of theoretical air fuel ratio characteristic jumpy, and its output is high level in the dense side of comparing with chemically correct fuel, is low level in rare side of comparing with chemically correct fuel.And, in three-way catalyst 14a, being provided with the catalyst-temperature pickup 19 that detects its temperature (hereinafter referred to as " catalyst temperature ") TCAT, its testing signal is provided for ECU 5.

ECU 5 constitutes by having the output circuit that offers above-mentioned Fuelinjection nozzle 6 to the memory circuit of various operation programs that to carry out shaping, voltage level is proofreaied and correct be specified level, the input circlult, central processing unit (hereinafter referred to as " CPU "), storage that analog signal values are converted to the function of digital signal value etc. are carried out by this CPU of the waveform input signal from various sensors and operation result etc., drive signal etc.

The CPU of ECU 5 differentiates various engine operating status according to above-mentioned various engine parameter signals, and, use following formula (1) computing and above-mentioned TDC signal pulse to carry out the fuel injection time TOUT of the Fuelinjection nozzle 6 of breakdown action synchronously according to this engine operating status that determines.

TOUT＝TIM×KCMD×KAF×K1+K2 (1)

Wherein, TIM is basic fuel quantity, and specifically the basic fuel injection time of Fuelinjection nozzle 6 is that the TIM table that retrieval sets according to intake air flow GAIR decides.The TIM table is configured to make the air fuel ratio of the mixed gas that offers motor to be roughly chemically correct fuel.

KCMD is the target air-fuel ratio coefficient, and the output SVO2 according to O2 sensor 18 in controlling usually sets.The inverse of target air-fuel ratio COEFFICIENT K CMD and air fuel ratio A/F, promptly fuel air ratio F/A is directly proportional, and value 1.0 when theoretical air fuel ratio, thereby are also referred to as the target equivalent proportion.When carrying out catalyst degradation described later when judging, target air-fuel ratio COEFFICIENT K CMD is set to air fuel ratio alternately is controlled at dense side and the rare side of comparing with chemically correct fuel.

KAF is when the feedback control executive condition is set up, by PID (proportion integration differentiation) control or use the self adaptive control of adaptive controller (Self Tuning Regulator) to be calculated to be to make the air fuel ratio correction coefficient consistent with target equivalent proportion KCMD according to the detection equivalent proportion KACT that checkout value calculated of LAF sensor 17.

K1 and K2 are respectively other correction factor and the correcting variable that go out according to various engine parameter signal operations, and are decided to be the optimized specified value of all characteristics such as realizing the fuel efficiency characteristics corresponding with engine operating status, motor accelerating performance.

The CPU of ECU 5 offers Fuelinjection nozzle 6 to the drive signal of opening Fuelinjection nozzle 6 via output circuit according to by the above-mentioned fuel injection time TOUT that obtains.And the CPU of ECU 5 carries out the deterioration judging of three-way catalyst 14a as described below.In addition, when being judged to be three-way catalyst 14a deterioration, be estimated as the also roughly same deterioration of three-way catalyst 14b, carry out for example bright lamp of emergency warning lamp.

The deterioration judging of three-way catalyst be according to the chemically correct fuel be the center when making the air fuel ratio change of the mixed gas that offers motor 1 the O2 sensor output SVO2 of (when hocketing rare running and dense running) carry out.So alternately carry out being controlled at of rare running and dense running hereinafter referred to as " disturbance control ".Specifically, carry out rare running, the oxygen of the amount of the degree that the three-way catalyst of deterioration can not be accumulated offers three-way catalyst so that can accumulate normal three-way catalyst, switches to dense running afterwards and carries out dense running, so that with roughly all dischargings of oxygen of being accumulated.When this disturbance of execution is controlled, need only not deterioration of three-way catalyst, then shown in Fig. 2 (a), O2 sensor output SVO2 is with regard to variation hardly, and when the three-way catalyst deterioration, sensor is exported significantly variation shown in this figure (b).Therefore, in the present embodiment,, carry out the deterioration judging of three-way catalyst by detecting this difference.

Fig. 3 is the flow chart of the main flow handled of the deterioration judging of three-way catalyst.This CPU that handles by ECU 5 carried out every the stipulated time (for example 10 milliseconds).

In step S1, execution graph 4 and processing shown in Figure 5 generate the disturbing signal that is used to make the air fuel ratio variation.Specifically, the generation of disturbing signal is equivalent to air fuel ratio handoff parameter KOSFB is set at " 1 " or "-1 ".In step S2, carry out processing shown in Figure 7, KOSFB carries out the setting of target air-fuel ratio COEFFICIENT K CMD according to the air fuel ratio handoff parameter.Target air-fuel ratio COEFFICIENT K CMD output SVO2 according to O2 sensor 18 in controlling usually sets, and when carrying out the deterioration judging of three-way catalyst, sets according to the air fuel ratio handoff parameter KOSFB that sets in step S1.Thus, carry out the disturbance control of air fuel ratio.

In step S3, execution graph 9 and processing shown in Figure 10 according to the O2 sensor output SVO2 in the disturbance control, are calculated the critical parameter RESULT of the degradation of expression three-way catalyst, and when critical parameter RESULT surpassed decision threshold RSTTH, it was unusual to be judged to be three-way catalyst.

Fig. 4 and Fig. 5 are that the disturbing signal of carrying out in the step S1 of Fig. 3 generates the flow chart of handling.

In step S11, according to according to the O2N table shown in the detection equivalent proportion KACT that output calculated of LAF sensor 17 retrieval Fig. 6 (a), calculate the oxygen concentration parameter O2N that is directly proportional with oxygen concentration in the exhaust.The O2N table is configured to, oxygen concentration parameter O2N is " 0 " when the oxygen concentration O2ST (KACT=1.0) suitable with chemically correct fuel, when being higher than oxygen concentration O2ST by LAF sensor 17 detected oxygen concentrations (when air fuel ratio with rare side that chemically correct fuel is compared the time) get on the occasion of, when being lower than oxygen concentration O2ST (when air fuel ratio with dense side that chemically correct fuel is compared the time) get negative value.

In step S12, the OSC table according to shown in intake air flow GAIR retrieval Fig. 6 (b) calculates the benchmark oxygen amount OSC[g as deterioration catalyzer benchmark].The OSC table is configured to, and intake air flow GAIR increases more, and benchmark oxygen amount OSC just reduces more.Intake air flow GAIR is high more, exhaust is just short more by the time of three-way catalyst, on the other hand, as long as catalyst temperature and flow into oxygen concentration (b) in the exhaust in oxygen concentration (a) and the three-way catalyst in the exhaust in the three-way catalyst poor (b-a) constant, the reaction velocity in the three-way catalyst (speed of accumulating of oxygen) is with regard to constant.Therefore, intake air flow GAIR is high more, and the amount of oxygen that can be accumulated in the three-way catalyst is just few more.Therefore, the OSC table is set shown in Fig. 6 (b).

In step S13, the KTCATR table according to shown in catalyst temperature TCAT retrieval Fig. 6 (c) calculates the 1st temperature correction facotor KTCATR.The KTCATR table is configured to, and the 1st temperature correction facotor KTCATR gets negative value, and catalyst temperature TCAT is high more, and the 1st temperature correction facotor KTCATR is with regard to little (absolute value is big more).

In step S14, the KTCATL table according to shown in catalyst temperature TCAT retrieval Fig. 6 (d) calculates the 2nd temperature correction facotor KTCATL.KTCATL table is configured to, the 2nd temperature correction facotor KTCATL get on the occasion of, and catalyst temperature TCAT is high more, the 2nd temperature correction facotor KTCATL is just big more.

In step S15,, calculate dense side pole limit value OSOBJR and rare side pole limit value OSOBJL benchmark oxygen amount OSC, temperature correction facotor KTCATR and KTCATL substitution following formula (2), (3).

OSOBJR＝OSC×KTCATR (2)

OSOBJL＝OSC×KTCATL (3)

The dense side pole limit value OSOBJR that calculates like this and rare side pole limit value OSOBJL are the desired values of the inflow amount of oxygen OS that calculates in step S16, as the threshold value that is used to determine switch the moment of air fuel ratio, use in step S31 described later or S32.Rare side pole limit value OSOBJL is equivalent to that normal three-way catalyst can be accumulated and the three-way catalyst of deterioration can not be accumulated the inflow amount of oxygen of degree, and dense side pole limit value OSOBJR is set to and rare side pole limit value OSOBJL absolute value negative value about equally.In other words, dense side pole limit value OSOBJR and rare side pole limit value OSOBJL are configured to, when three-way catalyst just often, O2 sensor output SVO2 changes hardly, when the three-way catalyst deterioration, O2 sensor output SVO2 significantly changes.

In step S16, oxygen concentration parameter O2N substitution following formula (4) is calculated inflow oxygen flow O2, calculate inflow amount of oxygen OS flowing into oxygen flow O2 substitution following formula (5), and the previous value KOSFBZ of air fuel ratio handoff parameter is set at as previous value KOSFB.

O2＝O2N×GAIRAVE (4)

OS＝OS+O2 (5)

Here, GAIRAVE is for example moving average of the data about 6 of intake air flow GAIR, and the OS on the right of formula (5) is a calculated value last time.In addition, the computing of moving average GAIRAVE (not illustrating) is carried out synchronously with the generation of CRK pulse.

In step S17, differentiate whether air fuel ratio handoff parameter KOSFB is "-1 ", when this answer is that ("Yes") promptly is in rare running the time certainly, differentiate whether reseting mark FRESETOS is " 1 " (step S24).When (with reference to step S38, S40), reseting mark FRESETOS is set to " 1 " when having changed the value of air fuel ratio handoff parameter KOSFB.When air fuel ratio handoff parameter KOSFB just changed to "-1 ", the answer of step S24 was certainly ("Yes"), thereby enters step S27, differentiate flow into oxygen flow O2 whether be on the occasion of.When rare running had just begun, the answer of step S27 directly entered step S32 (Fig. 5) for negating ("No").When the oxygen concentration when carrying out rare running in the exhaust increased, the answer of step S27 entered step S28 for affirming ("Yes"), was set at " 0 " flowing into amount of oxygen OS, and made reseting mark FRESETOS return " 0 ".Enter step S32 afterwards.

When reseting mark FRESETOS returned " 0 ", the answer of step S24 entered step S25 for negating ("No"), differentiated to flow into whether amount of oxygen OS is negative value.Because this is answered and is negative ("No") usually, thereby directly enters step S32.When inflow amount of oxygen OS is negative value, be reset to " 0 " (step S26), enter step S32.

In step S32, whether differentiate inflow amount of oxygen OS greater than rare side pole limit value OSOBJL.Because this is answered to negating ("No") when rare running has just begun, thereby enter step S33, whether differentiate O2 sensor output SVO2 less than be " 1 " (step S33) than the air fuel ratio of the rare slightly side of chemically correct fuel suitable rare side mark definite value SVO2LEAN and downstream side oxygen concentration parameter K OSLEAN.Downstream side oxygen concentration parameter K OSLEAN is the parameter (with reference to step S39) that is set to " 0 " when O2 sensor output SVO2 is the value of the rare air fuel ratio of expression.Because this is answered to negating ("No") usually, thereby enter step S35, whether differentiate O2 sensor output SVO2 greater than with than suitable dense side mark definite value the SVO2RICH (〉 SVO2LEAN of the air fuel ratio of the dense slightly side of chemically correct fuel) and downstream side oxygen concentration parameter K OSLEAN be " 0 ".Because should answer usually also is to negate ("No"), thereby directly enters step S41.

When continuing rare running, flowing into amount of oxygen OS increases gradually afterwards.Then, when flowing into amount of oxygen OS surpass rare side pole limit value OSOBJL in step S32, enter step S40, KOSFB is set at " 1 " the air fuel ratio handoff parameter, and reseting mark FRESETOS is set at " 1 ".Thus, begin dense running.

When air fuel ratio handoff parameter KOSFB when "-1 " changes to " 1 ", enter step S19 from step S17, differentiate whether reseting mark FRESETOS is " 1 ".Because initial, the answer of step S19 is to affirm ("Yes"), thereby enters step S22, differentiation flows into whether oxygen flow O2 is negative value.When dense running had just begun, the answer of step S22 directly entered step S31 (Fig. 5) for negating ("No").When the oxygen concentration when beginning dense running in the exhaust descended, the answer of step S22 entered step S23 for affirming ("Yes"), was set at " 0 " flowing into amount of oxygen OS, and made reseting mark FRESETOS return " 0 ".Enter step S31 afterwards.Flow in the amount of oxygen OS dense running afterwards and get negative value.This means that (HC CO) is provided for three-way catalyst 14a to reducing agent, and the oxygen of being accumulated is used for the oxidation of reducing agent and reduces (outflow).

When reseting mark FRESETOS returned " 0 ", the answer of step S19 entered step S20 for negating ("No"), differentiate flow into amount of oxygen OS whether be on the occasion of.Because this is answered and is negative ("No") usually, thereby directly enters step S31.When flow into amount of oxygen OS be on the occasion of the time, be reset to " 0 " (step S21), enter step S31.

In step S31, whether differentiate inflow amount of oxygen OS less than dense side pole limit value OSOBJR.Because this is answered and is negative ("No") when dense running has just begun, thereby enters above-mentioned steps S33.Usually, the answer of step S33 and S35 is all for negating ("No").

When continuing dense running, flow into amount of oxygen OS and reduce (absolute value of negative value increases) gradually afterwards.Then, when flowing into amount of oxygen OS be lower than dense side pole limit value OSOBJR in step S31, enter step S38, KOSFB is set at "-1 " the air fuel ratio handoff parameter, and reseting mark FRESETOS is set at " 1 ".Thus, begin rare running.

When the deterioration of three-way catalyst 14a was constantly carried out, the answer of step S33 was to affirm ("Yes") in rare running sometimes.At this moment, enter step S39 from step S33, oxygen concentration parameter K OSLEAN is set at " 0 " the downstream side.Enter step S40 afterwards, transfer to dense running.That is, in this case,, carry out switching to dense running flowing into amount of oxygen OS above before rare side pole limit value OSOBJL.And, also sometimes in dense running the answer of step S35 be certainly ("Yes").At this moment, enter step S37 from step S35, oxygen concentration parameter K OSLEAN is set at " 1 " the downstream side.Enter step S38 afterwards, transfer to rare running.That is, in this case, before inflow amount of oxygen OS is lower than dense side pole limit value OSOBJR, carry out switching to rare running.

Except O2 sensor output SVO2, also use downstream side oxygen concentration parameter K OSLEAN to judge, this is in order to prevent the control fluctuation by hysteresis.

By step S33, S35, S37 and S39,, and under the situation that O2 sensor output SVO2 changes before the inflow amount of oxygen OS value of overstepping the extreme limit OSOBJL or the OSLBJR, also can prevent to make discharge characteristic to worsen even in three-way catalyst 14a deterioration.

In step S41, the KTCATD table according to shown in catalyst temperature TCAT retrieval Fig. 6 (e) calculates the 3rd temperature correction facotor KTCATD.KTCATD table and the same being configured to of KTCATL table, catalyst temperature TCAT is high more, and the 3rd temperature correction facotor KTCATD is just big more, and under same catalyst temperature TCAT, becomes the value greater than the 2nd temperature correction facotor KTCATL.

In step S42,, calculate and forbid decision threshold OSDISABLE the 3rd temperature correction facotor and the benchmark oxygen amount OSC substitution following formula (6) that in step S12, calculates.

OSDISABLE＝OSC×KTCATD (6)

In step S43, whether the absolute value of differentiating inflow amount of oxygen OS is greater than forbidding decision threshold OSDISABLE, when this answer is when affirming ("Yes"), Prohibiting Sign FDISABLEOS to be set at " 1 " (step S45).When | OS| ≦ OSDISABLE, Prohibiting Sign FDISABLEOS is set at " 0 " (step S44).When Prohibiting Sign FDISABLEOS is set to " 1 ", end the deterioration judging (with reference to Fig. 9, step S71) of catalyzer.

For example, air fuel ratio control can not be followed rapidly under the situation of the variation that sucks air quantity when the throttle opening rapid change, has the unusual possibility that increases of the absolute value that flows into amount of oxygen OS.In this case, deterioration judging accurately can not be carried out, thereby, the decline of precision can be prevented to judge by forbidding deterioration judging.

Fig. 7 is the flow chart of the KCMD computing carried out in the step S2 of Fig. 3.

In step S51, differentiate the disturbance of whether carrying out air fuel ratio, when this answer is when affirming ("Yes"), differentiate the air fuel ratio handoff parameter KOSFB that in the processing of Fig. 4 and Fig. 5, sets and whether equal its previous value KOSFBZ (step S52).

When the answer of step S51 or S52 is negative ("No"), when promptly not carrying out disturbance, perhaps when the value of air fuel ratio handoff parameter KOSFB changes, target air-fuel ratio COEFFICIENT K CMD is set at " 1.0 " (step S53), enter step S54.When KOSFB=KOSFBZ, directly enter step S54.

In step S54, differentiate whether air fuel ratio handoff parameter KOSFB is " 1 ".When this answer is when affirming ("Yes"), use following formula (7) to upgrade target air-fuel ratio COEFFICIENT K CMD (step S55).

KCMD＝KCMD+ΔKCMD (7)

Here, Δ KCMD is the scheduled update value, for example is set to 0.0002.

When air fuel ratio handoff parameter KOSFB was " 1 ", by repeated execution of steps S55, target air-fuel ratio COEFFICIENT K CMD increased gradually from " 1.0 " beginning.That is, air fuel ratio changes to dense direction gradually.

When KOSFB=-1 in step S54, use following formula (8) to upgrade target air-fuel ratio COEFFICIENT K CMD (step S56).

KCMD＝KCMD—ΔKCMD (8)

Therefore, when air fuel ratio handoff parameter KOSFB was "-1 ", by repeated execution of steps S56, target air-fuel ratio COEFFICIENT K CMD reduced gradually from " 1.0 " beginning.That is, air fuel ratio changes to rare direction gradually.

In step S57～S60, the limit value of the target air-fuel ratio COEFFICIENT K CMD that calculates is handled.Promptly, as target air-fuel ratio COEFFICIENT K CMD during greater than CLV ceiling limit value KCMDH (for example 1.03), target air-fuel ratio COEFFICIENT K CMD is set at CLV ceiling limit value KCMDH (step S57, S58), as target air-fuel ratio COEFFICIENT K CMD during less than lower limit KCMDL (for example 0.97), target air-fuel ratio COEFFICIENT K CMD be set at lower limit KCMDL (step S59, S60).

By the processing of Fig. 7, target air-fuel ratio COEFFICIENT K CMD according to the value (this figure (a)) of air fuel ratio handoff parameter KOSFB, presses variation shown in this figure (b) as shown in Figure 8.

Fig. 9 and Figure 10 are the flow charts that the deterioration judging carried out in the step S3 of Fig. 3 is handled.

In step S71, differentiate whether Prohibiting Sign FDISABLEOS is " 1 ".Whether when this answer is negative ("No"), differentiating is (step S72) during the disturbance of air fuel ratio is carried out.When the answer of step S71 is that the answer of ("Yes") or step S72 certainly is when being negative ("No"), the maximum value SVO2MAX of O2 sensor output SVO2 is set at " 0 ", and minimum value SVO2MIN is set at " 1500 " (step S73), directly finish this processing.

When the answer of step S72 is ("Yes") certainly, when promptly carrying out the disturbance of air fuel ratio, differentiate air fuel ratio handoff parameter KOSFB and whether equal previous value KOSFBZ (step S74).When KOSFB=KOSFBZ, use following formula (9) and (10) to upgrade maximum value SVO2MAX and minimum value SVO2MIN.The maximum value SVO2MAX that calculated before the right of formula (9) is selected at last time and ought O2 sensor output SVO2 last time in a bigger side's computing, the minimum value SVO2MIN that the right of formula (10) calculated before being selected at last time and ought O2 sensor output SVO2 last time in a less side's computing.After having carried out step S75, enter step S89.

SVO2MAX＝max(SVO2MAX，SVO2) (9)

SVO2MIN＝min(SVO2MIN，SVO2) (10)

When the answer of step S74 is negative ("No"), promptly just changed after the air fuel ratio handoff parameter KOSFB, the 2nd storing value SVO2LP2 of maximum value SVO2MAX or minimum value SVO2MIN is set at the 1st storing value SVO2LP1 (step S76).After just carrying out last time air fuel ratio switching, the 1st storing value SVO2LP1 is set to maximum value SVO2MAX or minimum value SVO2MIN in step S78 or S80.

In step S77, differentiate whether air fuel ratio handoff parameter KOSFB is " 1 ".When this answer is when affirming ("Yes"), the 1st storing value SVO2LP1 to be set at maximum value SVO2MAX at this moment, and to make maximum value SVO2MAX be reset to " 0 " (step S78).When air fuel ratio handoff parameter KOSFB was "-1 ", the answer of step S77 was negative ("No"), thereby directly enters step S79.

In step S79, differentiate whether air fuel ratio handoff parameter KOSFB is "-1 ".When air fuel ratio handoff parameter KOSFB is "-1 ", enter step S80, the 1st storing value SVO2LP1 is set at minimum value SVO2MIN at this moment, and makes minimum value SVO2MIN be reset to " 1500 " (step S78).When air fuel ratio handoff parameter KOSFB was " 1 ", the answer of step S79 was negative ("No"), thereby directly enters step S81.

In step S81, the 3rd differential parameter SVO2D3 of the difference of expression maximum value SVO2MAX and minimum value SVO2MIN is set at the 2nd differential parameter SVO2D2, and the 2nd differential parameter SVO2D2 is set at the 1st differential parameter SVO2D1.Then, carry out the renewal of the 1st differential parameter SVO2D1 by step S82～S87.

In step S82, whether differentiate the 2nd storing value SVO2LP2 greater than the specified value SVO2OBJ suitable and the 1st storing value SVO2LP1 with chemically correct fuel less than specified value SVO2OBJ.When this answer is negative ("No"), whether further differentiate the 2nd storing value SVO2LP2 less than specified value SVO2OBJ and the 1st storing value SVO2LP1 greater than specified value SVO2OBJ (step S84).When the answer of step S82 and S84 is negative ("No"), promptly, when the 1st and the 2nd storing value SVO2LP1, SVO2LP2 all less than specified value SVO2OBJ, when perhaps the 1st and the 2nd storing value SVO2LP1, SVO2LP2 were all greater than specified value SVO2OBJ, expression O2 sensor output SVO2 changed hardly.Therefore, the 1st differential parameter SVO2D1 is set at " 0 " (step S87), enters step S88.

When the answer of step S82 or S84 is sure ("Yes"), be that maximum value SVO2MAX in the continuous air fuel ratio switching instant is greater than specified value SVO2OBJ and minimum value SVO2MIN during less than specified value SVO2OBJ, the 1st storing value SVO2LP1 and the 2nd storing value SVO2LP2 substitution following formula (11), calculate the 1st differential parameter SVO2D1 (step S86).Afterwards, enter step S88.

SVO2D1＝|SVO2LP1—SVO2LP2| (11)

In step S88, use following formula (12) to calculate the minimum value of the 1st～the 3rd differential parameter SVO2D1, SVO2D2, SVO2D3, be lowest difference score value SVO2D, use following formula (13) accumulative total lowest difference score value SVO2D to come computational discrimination parameters R ESULT then, and make counter CRESULT add " 1 ".Critical parameter RESULT represents the degradation of three-way catalyst 14a.

SVO2D＝min(SVO2D1，SVO2D2，SVO2D3) (12)

RESULT＝RESULT+SVO2D (13)

Get bigger value more than 3 times so long as not differential parameter SVO2D1 is continuous, lowest difference score value SVO2D is less value just.Therefore, be lowest difference score value SVO2D by differential parameter SVO2D1, the SVO2D2 that uses continuous 3 sampling instants, the minimum value of SVO2D3, can get rid of the influence of the temporary transient change of O2 sensor output SVO2, can obtain critical parameter RESULT accurately.

In step S89, whether the value of differentiating counter CRESULT greater than stipulated number CRST0 (for example 6), when this answer is negative ("No"), directly finishes this processing.When the value of counter CRESULT in step S89 surpasses stipulated number CRST0, enter step S90, whether differentiate critical parameter RESULT greater than deterioration judging threshold value RSTTH.When this answer is negative ("No"), be judged to be three-way catalyst 14a normal (step S92).When critical parameter RESULT surpasses deterioration judging threshold value RSTTH, be judged to be three-way catalyst 14a unusual (step S91).When being judged to be when unusual, for example make the bright lamp of emergency warning lamp.

When O2 sensor output SVO2 changes shown in Fig. 2 (a), just often promptly at three-way catalyst 14a, critical parameter RESULT is roughly zero, on the other hand, when O2 sensor output SVO2 changes shown in Fig. 2 (b), promptly when three-way catalyst 14a deterioration, critical parameter RESULT is bigger value, thereby can detect the degradation of three-way catalyst 14a according to critical parameter RESULT exactly.

As described in detail above, in the present embodiment, according to calculate the amount of oxygen OS that flows in the three-way catalyst 14a according to the oxygen concentration parameter O2N that output calculated of LAF sensor 17 and by intake air flow sensor 7 detected intake air flow GAIR, and flow into comparative result between amount of oxygen OS and dense side pole limit value OSOBJR or the rare side pole limit value OSOBJL according to this, carry out air fuel ratio alternately is controlled at rare side of comparing with chemically correct fuel and the disturbance of dense side is controlled.Then, control the critical parameter RESULT that executory O2 sensor output SVO2 calculates the degradation of expression three-way catalyst 14a according to disturbance.Dense side pole limit value OSOBJR and rare side pole limit value OSOBJL as the desired value that flows into amount of oxygen OS are configured to, SVO2 changes hardly when three-way catalyst O2 sensor output just often, and O2 sensor output SVO2 significantly changes when the three-way catalyst deterioration, thereby discharge characteristic is worsened fully, the moment that begins deterioration at three-way catalyst can make discharge characteristic worsen hardly, can detect degradation rapidly.

And, owing to the amount of oxygen that can be accumulated in the three-way catalyst 14a depends on that intake air flow GAIR changes (intake air flow GAIR is high more, and then amount of oxygen is few more), thereby it is high more then more little by dense side pole limit value OSOBJR and rare side pole limit value OSOBJL are set for intake air flow GAIR, can carry out suitable desired value and set, can suppress the deterioration of discharge characteristic.

And, owing to the amount of oxygen that can be accumulated in the three-way catalyst 14a depends on that catalyst temperature TCAT changes, thereby by carrying out the correction of serviceability temperature correction factor KTCATR and KTCATL, the switching of air fuel ratio becomes suitable period, the degradation of catalyzer can be detected exactly, and the deterioration of discharge characteristic can be prevented reliably.

And, owing to also be provided with three-way catalyst 14b, thereby can prevent that HC and NOx are discharged from when three-way catalyst 14a deterioration in the downstream side of O2 sensor 18, can keep good discharge characteristic.

In the present embodiment, intake air flow sensor 7, LAF sensor 17 and O2 sensor 18 are equivalent to intake air flow detection unit, the 1st oxygen concentration sensor and the 2nd oxygen concentration sensor respectively.And ECU 5 constitutes inflow amount of oxygen computing unit, air fuel ratio switch control unit, deterioration detection unit and forbids the unit.Specifically, the step S11 of Fig. 4 and S16 are equivalent to flow into the amount of oxygen computing unit, the processing of the step S31 of the step S12 of Fig. 4～S15, S17～S28, Fig. 5～S40 and Fig. 7 is equivalent to the air fuel ratio switch control unit, the step S82 of the step S72 of Fig. 9～S81 and Figure 10～S92 is equivalent to deterioration detection unit, and the step S71 of the step S41 of Fig. 5～S45 and Fig. 9 is equivalent to forbid the unit.

[second mode of execution]

Present embodiment has been done further improvement to the catalyst degradation determination processing shown in first mode of execution.In addition, except the aspect of following explanation, other is identical with first mode of execution.

1) cutting off in the fuel cut-off running of the fuel supply of motor 1, detection is as the fuel cut-off output VLAFFC of the characteristic variations parameter of the output characteristics variation of expression LAF sensor 17, and based on fuel cut-out output VLAFFC carries out the correction of LAF sensor output VLAF.

2) the regulation updating value Δ KCMD of replacement target equivalent proportion KCMD, and use dense side updating value Δ KCMDR and rare side updating value Δ KCMDL, set dense side updating value Δ KCMDR according to intake air flow GAIR and dense side pole limit value OSOBJR, and set rare side updating value Δ KCMDL according to intake air flow GAIR and rare side pole limit value OSOBJL.

Figure 11 is the flow chart of the main flow handled of the three-way catalyst deterioration judging of present embodiment.This CPU that handles by ECU5 carried out every the stipulated time (for example 10 milliseconds).

In step S101, carry out LAF sensor output calibration shown in Figure 13 and handle, carry out changing the correction of corresponding sensor output VLAF with the output characteristics of LAF sensor 17.In step S102, carry out FMCND computing shown in Figure 16, when the deterioration judging executive condition is set up, judging that permission flag FMCND is set at " 1 ".

In step S103, differentiate and judge whether permission flag FMCND is " 1 ", when this answer is negative ("No"), directly finishes this processing.When FMCND=1, carry out disturbing signal successively and generate processing (step S104), KCMD computing (S105) and deterioration judging processing (S106).

The disturbing signal of step S104 generate handle identical with the processing of Fig. 4, Fig. 5 of the deterioration judging processing of step S106 and first mode of execution and Fig. 9, Figure 10.In step S105, carry out KCMD computing shown in Figure 17.

Figure 12 is the output characteristics that is used for LAF sensor 17, i.e. the relation of air fuel ratio A/F and LAF sensor output between the VLAF through the time change the figure that describes.The solid line of this figure is represented the average characteristics under the original state, and dotted line L2 represents the example that slope changes to the direction that increases, and dotted line L3 represents the example that slope changes to the direction that reduces.By correction calculation described later, LAF sensor output VLAF is corrected into the characteristic that dotted line L2 or L3 are represented becomes the characteristic that solid line L1 represents.

Figure 13 is the flow chart that the LAF sensor output calibration carried out in the step S101 of Figure 11 is handled.

In step S121, differentiate and proofread and correct whether end mark FVLEND is " 1 ".When correction is finished, proofread and correct end mark FVLEND and in step S131, be set to " 1 ".Therefore, initial, the answer of step S121 is for negating ("No"), and whether differentiate is in the fuel cut-off running of motor 1.When not being in the fuel cut-off running time, the value of the timer TMFC that makes progress is set at " 0 " (step S123), directly enter step S132.

When being in the fuel cut-off running time, whether the value of differentiating timer TMFC is more than or equal to regulation standby time TDLY (for example 3 seconds).Because initial this answer is negative ("No"), thereby enters step S125, the value of the timer TMDET that makes progress is set at " 0 ", and the value of the aggregate-value VLAFI sum counter CDET of LAF sensor output VLAF is set at " 0 ".Enter step S132 afterwards.

When the answer of step S124 is sure ("Yes"), enter step S126, whether the value of differentiating timer TMDET is more than or equal to regulation TDET detection time (for example 2.5 seconds).Because initial this answer is negative ("No"), thereby enters step S127, makes counter CDET add " 1 ", and utilize following formula (21) to calculate aggregate-value VLAFI.Enter step S132 afterwards.

VLAFI＝VLAFI+VLAF (21)

Wherein, the VLAFI on the right is a calculated value last time.

When the answer of step S126 during for ("Yes") certainly, enter step S128, use following formula (22) to calculate fuel cut-off output VLAFFC as the mean value of LAF sensor output detected in regulation TDET detection time.Promptly, fuel cut-off is exported VLAFFC as shown in figure 14, is equivalent at the mean value of exporting VLAF behind the moment t0 (sign FFC is changed to the moment of " 1 " from " 0 ") of beginning fuel cut-off running through the moment t1 behind the regulation standby time TDLY to the LAF sensor the detection period of moment t2.

VLAFFC＝VLAFI/CDET (22)

The solid line L11 of Figure 14, dotted line L12 and L13 correspond respectively to solid line L1, dotted line L2 and the L3 of Figure 12.That is, solid line L11 represents average characteristics, the example that dotted line L12 changes to the direction that increases corresponding to the slope of the straight line of expression output characteristics, the example that dotted line L13 changes to the direction that reduces corresponding to slope.

In the step S129 of Figure 13, based on fuel cuts off output VLAFFC retrieval KVLFFC table shown in Figure 15, slope calculations correction factor KVLFFC.The KVLFFC table is configured to, and VLAFFC is high more in fuel cut-off output, and slope correction COEFFICIENT K VLFFC is just more little.

In step S131, be set at " 1 " proofreading and correct end mark FVLEND, finish this processing afterwards.FVLEND is set to " 1 " afterwards in the correction end mark, and the answer of step S121 becomes ("Yes") certainly, enters step S132 via step S123.

In step S132, the LAF sensor output VLAF that in step S129, calculates and the right of slope correction COEFFICIENT K VLFFC substitution following formula (23), calculation correction LAF sensor output VLAFCR.In addition, before execution in step S129, slope correction COEFFICIENT K VLFFC is initialized to " 1.0 ".

VLAFCR＝(VLAF—VCNT)×KVLFFC+VCNT (23)

Wherein, VCNT is corresponding with chemically correct fuel AFST as shown in figure 12 LAF sensor output.

By the correction of use formula (23), the output characteristics that dotted line L2, L3 among Figure 12 represent is proofreaied and correct the characteristic of representing for solid line L1.

Therefore, in the present embodiment, generate the oxygen concentration parameter O2N that uses in handling in the disturbing signal of the step S104 of Figure 11 and use and proofread and correct LAF sensor output VLAFCR and calculate.

Figure 16 is the flow chart of the FMCND computing carried out in the step S102 of Figure 11.

In step S111, differentiate and proofread and correct whether end mark FVLEND is " 1 ".When this answer is certainly when ("Yes"), differentiate intake air flow GAIR whether greater than regulation lower limit GAIRLML (for example 8[g/sec]) and less than set upper limit value GAIRLMH (for example 16[g/sec]) (step S112).When this answer is certainly when ("Yes"), whether the variable quantity DGAIR (for example the checkout value before the currency of intake air flow GAIR and 500 milliseconds is poor) that differentiates intake air flow GAIR is less than set upper limit variable quantity DGAIRLMH (for example 3[g/sec]) (step S113).When this answer is when affirming ("Yes"), whether further to differentiate catalyst temperature TCAT more than or equal to regulation lower limit temperature TCATLML (for example 300 ℃) (step S114).

When the answer of step S114 is certainly when ("Yes"), judging that permission flag FMCND is set at " 1 ", so that the catalyst degradation judgement is carried out in permission.On the other hand, when the answer of any one party among step S111～S114 is negative ("No"),, does not carry out catalyst degradation and judge judging that permission flag FMCND is set at " 0 ".

Figure 17 is the flow chart of the KCMD computing carried out in the step S105 of Figure 11.

This treatment step S151～S153 is identical with step S51～S53 of Fig. 7, and step S155, S162～S165 are identical with step S54, the S57～S60 of Fig. 7.Below, only difference is described.

In step S154, the STEP67 table according to shown in intake air flow GAIR retrieval Figure 18 (a) calculates basic updating value STEP67.The STEP67 table is configured to, and intake air flow GAIR is big more, and basic updating value STEP67 is just more little.Flow GAIR1, the GAIR2 of Figure 18 (a) are set to for example 10[g/sec respectively], 20[g/sec], updating value STEPX1, STEPX2 for example are set to 0.001,0.002 respectively.

When air fuel ratio handoff parameter KOSFB is " 1 ", enter step S156 from step S155, the KSTEP67 table according to shown in absolute value retrieval Figure 18 (b) of dense side pole limit value OSOBJR calculates stride correction factor KSTEP67.The KSTEP67 table is configured to, and the absolute value of dense side pole limit value OSOBJR or rare side pole limit value OSOBJL are big more, and stride correction factor KSTEP67 is just big more.In Figure 18 (b), amount of oxygen OSC1 and OSC2 for example are set to 10 and 20 respectively, and coefficient value KSTEP1 and KSTEP2 are set to 1.0 and 2.0 respectively.

In step S157,, calculate dense side updating value Δ KCMDR stride correction factor KSTEP67 and basic updating value STEP67 substitution following formula (24).Then, in step S158, the dense side updating value Δ KCMDR substitution following formula (25) calculating carries out the renewal of target air-fuel ratio COEFFICIENT K CMD.

ΔKCMDR＝KSTEP67×STEP67 (24)

KCMD＝KCMD+ΔKCMDR (25)

On the other hand, when air fuel ratio handoff parameter KOSFB is "-1 ", enter step S159 from step S155, the KSTEP67 table according to shown in rare side pole limit value OSOBJL retrieval Figure 18 (b) calculates stride correction factor KSTEP67.

In step S160,, calculate rare side updating value Δ KCMDL stride correction factor KSTEP67 and basic updating value STEP67 substitution following formula (26).Then, in step S161, the rare side updating value Δ KCMDL substitution following formula (27) calculating carries out the renewal of target air-fuel ratio COEFFICIENT K CMD.

ΔKCMDL＝KSTEP67×STEP67 (26)

KCMD＝KCMD—ΔKCMDL (27)

Processing according to Figure 17, parameter updating value Δ KCMDR and Δ KCMDL that renewal speed when making target air-fuel ratio COEFFICIENT K CMD increasing or decreasing is suitable are configured to, intake air flow GAIR is big more then more little, and dense side pole limit value OSOBJR and rare side pole limit value OSOBJL are big more then big more, thereby when the bigger high loaded process of intake air flow, the renewal speed of target air-fuel ratio COEFFICIENT K CMD is lower, the influence of the response characteristic deterioration of O2 sensor 18 can be alleviated, catalyst degradation judgement accurately can be carried out.On the other hand, when the less low load operation of intake air flow, the renewal speed of target air-fuel ratio COEFFICIENT K CMD is higher, thereby can shorten catalyst degradation and judge the needed time.

In addition, in the present embodiment, since proofread and correct LAF sensor 18 output characteristics (slope of the straight line that concerns between expression air fuel ratio A/F and the sensor output VLAF) through the time variation processing (Figure 13), thereby be not subjected to LAF sensor 18 output characteristics through the time influence that changes, the calculation accuracy that flows into the amount of oxygen in the three-way catalyst 14a can be kept, catalyst degradation judgement accurately can be carried out.

In the present embodiment, the processing of Figure 17 is equivalent to the part of air fuel ratio switch control unit, and the step S122 of Figure 13～S128 is equivalent to the characteristic variations detection unit, and step S129, the S130 of this figure are equivalent to correcting unit.

In addition, the invention is not restricted to above-mentioned mode of execution, can carry out various distortion.For example, in the above-described embodiment, three-way catalyst 14a and 14b are stored in the container, but also can constitute separately.In addition,, also can use the present invention even be not provided with under the situation of three-way catalyst in the downstream side of O2 sensor 18, compared with prior art, the deterioration of the discharge characteristic in the time of can further alleviating the deterioration judging execution.

In addition, can judge the deterioration of the response characteristic of LAF sensor 18, when degradation increases, carry out computing, and use this compensated sensor to export and carry out the catalyst degradation judgement sensor output VLAF compensation response deterioration.In this case, in the FMCND of Figure 16 computing, the response deterioration is compensated completed situation be appended in the deterioration judging executive condition, judge the setting of permission flag FMCND.

In addition, the present invention also can be applied to be installed in bent axle as the deterioration judging with the exhaust gas purification catalyst in the vent systems of motor etc. such as the boat-propelling machine of machine outside of Vertical direction etc.

Claims (16)

1. catalyst deterioration detecting apparatus, its detection are arranged on the degradation of the exhaust gas purification catalyst in the vent systems of internal-combustion engine, it is characterized in that this catalyst deterioration detecting apparatus has:

The intake air flow detection unit, it detects the intake air flow of above-mentioned internal-combustion engine;

The 1st oxygen concentration sensor, it is arranged on the upstream side of above-mentioned catalyzer;

The 2nd oxygen concentration sensor, it is arranged on the downstream side of above-mentioned catalyzer;

Flow into the amount of oxygen computing unit, it is according to calculate the amount of oxygen that flows in the above-mentioned catalyzer by the detected oxygen concentration of above-mentioned the 1st oxygen concentration sensor with by the intake air flow that above-mentioned intake air flow detection unit is detected;

The air fuel ratio switch control unit, it alternately is controlled to be the air fuel ratio of the mixed gas that offers above-mentioned internal-combustion engine rare side and the dense side of comparing with chemically correct fuel according to the comparative result between the desired value of the inflow amount of oxygen that is calculated by above-mentioned inflow amount of oxygen computing unit and this inflow amount of oxygen; And

Deterioration detection unit, it detects the degradation of above-mentioned catalyzer according to the output of above-mentioned the 2nd oxygen concentration sensor in the action of above-mentioned air fuel ratio switch control unit.

2. catalyst deterioration detecting apparatus according to claim 1 is characterized in that, the switching controls that above-mentioned air fuel ratio switch control unit carries out above-mentioned air fuel ratio according to the output and the comparative result between the predetermined value of above-mentioned the 2nd oxygen concentration sensor.

3. catalyst deterioration detecting apparatus according to claim 1 and 2 is characterized in that, above-mentioned air fuel ratio switch control unit calculates above-mentioned desired value according to above-mentioned intake air flow.

4. catalyst deterioration detecting apparatus according to claim 1, it is characterized in that, this catalyst deterioration detecting apparatus also has the catalyst temperature detection unit of the temperature that detects above-mentioned catalyzer, and above-mentioned air fuel ratio switch control unit calculates above-mentioned desired value according to above-mentioned catalyst temperature.

5. catalyst deterioration detecting apparatus according to claim 1 is characterized in that, this catalyst deterioration detecting apparatus also has: forbid the unit, it forbids that according to above-mentioned inflow amount of oxygen the degradation of above-mentioned deterioration detection unit detects.

6. catalyst deterioration detecting apparatus according to claim 1 is characterized in that, in above-mentioned vent systems, also is provided with exhaust gas purification catalyst in the downstream side of above-mentioned the 2nd oxygen concentration sensor.

7. catalyst deterioration detecting apparatus according to claim 1 is characterized in that, the renewal speed of the above-mentioned air fuel ratio during switching that above-mentioned air fuel ratio switch control unit is set above-mentioned air fuel ratio according to the intake air flow and the above-mentioned desired value of above-mentioned internal-combustion engine.

8. catalyst deterioration detecting apparatus according to claim 1 is characterized in that, this catalyst deterioration detecting apparatus also has:

The characteristic variations detection unit, the characteristic variations parameter that its output characteristics that detects above-mentioned the 1st oxygen concentration sensor of expression changes; And

Correcting unit, it is according to the output of above-mentioned the 1st oxygen concentration sensor of above-mentioned characteristic variations parameter correction,

Sensor after above-mentioned inflow amount of oxygen computing unit use is proofreaied and correct by above-mentioned correcting unit is exported and is calculated above-mentioned inflow amount of oxygen.

9. catalyst degradation detection method, its detection is arranged on the degradation of the exhaust gas purification catalyst in the vent systems of internal-combustion engine, above-mentioned vent systems has the 1st oxygen concentration sensor of the upstream side that is arranged on above-mentioned catalyzer and is arranged on the 2nd oxygen concentration sensor in the downstream side of above-mentioned catalyzer, and above-mentioned degradation detection is made of following steps:

A) intake air flow of the above-mentioned internal-combustion engine of detection;

B) according to calculating the amount of oxygen that flows in the above-mentioned catalyzer by above-mentioned the 1st oxygen concentration sensor detected oxygen concentration and detected intake air flow;

C) according to the comparative result between the desired value of the inflow amount of oxygen that calculates and this inflow amount of oxygen, the air fuel ratio of the mixed gas that offers above-mentioned internal-combustion engine is alternately controlled to rare side and the dense side of comparing with chemically correct fuel; And

D) carrying out above-mentioned steps c) in the process of air fuel ratio switching controls in, detect the degradation of above-mentioned catalyzer according to the output of above-mentioned the 2nd oxygen concentration sensor.

10. catalyst degradation detection method according to claim 9 is characterized in that, above-mentioned air fuel ratio switching controls is carried out according to the output of above-mentioned the 2nd oxygen concentration sensor and the comparative result between the regulation predetermined value.

11. catalyst degradation detection method according to claim 9 is characterized in that, calculates above-mentioned desired value according to above-mentioned intake air flow.

12. catalyst degradation detection method according to claim 9 is characterized in that, this method also has the step of the temperature that detects above-mentioned catalyzer, calculates above-mentioned desired value according to detected catalyst temperature.

13. catalyst degradation detection method according to claim 9 is characterized in that, this method also has according to above-mentioned inflow amount of oxygen forbids the step that above-mentioned degradation detects.

14. catalyst degradation detection method according to claim 9 is characterized in that, in above-mentioned vent systems, yet is provided with exhaust gas purification catalyst in the downstream side of above-mentioned the 2nd oxygen concentration sensor.

15. catalyst degradation detection method according to claim 9 is characterized in that, the renewal speed of the above-mentioned air fuel ratio when setting above-mentioned air fuel ratio and switch according to the intake air flow of above-mentioned internal-combustion engine and above-mentioned desired value.

16. catalyst degradation detection method according to claim 9 is characterized in that, this method also has following steps:

I) the characteristic variations parameter of the output characteristics variation of above-mentioned the 1st oxygen concentration sensor of detection expression; And

Ii) according to the output of above-mentioned the 1st oxygen concentration sensor of above-mentioned characteristic variations parameter correction;

Above-mentioned degradation detection uses the sensor after the above-mentioned correction to export and calculates above-mentioned inflow amount of oxygen.

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