JP3377336B2 - Air-fuel ratio control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to an exhaust system for an internal combustion engine.
Is supplied to the engine based on the output of the
Feedback control of the air-fuel ratio of the mixture to the target air-fuel ratio.
Air-fuel ratio control device, especially deterioration of wide-range air-fuel ratio sensor
The present invention relates to an air-fuel ratio control device having a detection function. [0002] 2. Description of the Related Art A wide-range air-fuel ratio sensor is provided in an exhaust system of an internal combustion engine.
And supply it to the engine based on the output of the air-fuel ratio sensor.
The air-fuel ratio to the air-fuel mixture using the proportional and integral terms
The back control method has been widely known. [0003] SUMMARY OF THE INVENTION
In the conventional air-fuel ratio control system, the
The response of the wide area air-fuel ratio sensor deteriorates due to clogging, etc.
However, the driver can grasp it quickly and accurately.
Responsiveness of the wide area air-fuel ratio sensor has deteriorated
Feedback control of the supply air-fuel ratio
Emission characteristics and the driver's
There is a problem that drivability may be deteriorated. The present invention solves the above-mentioned problems of the prior art.
The purpose is to easily and accurately
Air-fuel that can detect deterioration of responsiveness of the air-fuel ratio sensor
It is to provide a ratio control device. [0005] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The air-fuel ratio control device according to claim 1 of the present invention is a
The value is proportional to the oxygen concentration in the exhaust gas.
An air-fuel ratio detecting means,Responsive
Response deterioration detection permitting means for permitting detection of deterioration;
Deterioration detection permission means permits detection of responsiveness deterioration.
The output of the air-fuel ratio detection means and the hysteresis
Inversion judgment reference value providedAnd provide the
The air-fuel ratio of the air-fuel mixture to be supplied is determined by the proportional and integral terms.
Air-fuel ratio feedback control means for feedback control;
During the air-fuel ratio control by the air-fuel ratio feedback control means,
PutOf the output of the air-fuel ratio detecting meansCriteria for judging inversion
Against the valueAn inversion cycle calculating means for calculating an inversion cycle;
Based on the inversion period calculated by the inversion period calculation means
The air-fuel ratio detecting meansDegradation detection to detect responsiveness degradation
With meansIt is characterized by the following. [0006] [0007] According to the air-fuel ratio control device of the first aspect of the present invention,
When the detection of deterioration of responsiveness is permitted,
Inversion judgment reference value with stage output and hysteresis
The air-fuel ratio of the mixture supplied to the engine is proportional to
And feedback control by the integral termThe air-fuel ratio system
In youOf the output of the air-fuel ratio detecting meansThe reversal judgment
For standard valueAn inversion cycle is calculated, and the calculated
Of the air-fuel ratio detecting means based on the rotation cycle.Responsiveness degradation
Is detected. [0008] [0009] Embodiments of the present invention will be described below with reference to the drawings.
You. FIG. 1 shows an internal combustion engine according to one embodiment of the present invention.
(Hereinafter referred to as "engine") and its control device
FIG. In the figure, 1 is an intake valve and an exhaust valve for each cylinder.
(Not shown) of a DOHC in-line four-cylinder
Engine. An intake pipe 2 of the engine 1 has a branch portion (intake manifold).
(Hold) 11 to the combustion chamber of each cylinder of the engine 1
Pass. A throttle valve 3 is arranged in the middle of the intake pipe 2.
I have. Throttle valve opening (θTH) for throttle valve 3
The sensor 4 is connected to the throttle valve opening θTH.
Electronic control unit that outputs electric signals according to
(Hereinafter referred to as “ECU”) 5. In the intake pipe 2
Has an auxiliary air passage 6 that bypasses the throttle valve 3.
In the middle of the passage 6, an auxiliary air amount control valve 7 is provided.
Is arranged. The auxiliary air amount control valve 7 is connected to the ECU 5.
The valve opening amount is controlled by the ECU 5.
You. The intake pipe 2 has a suction port upstream of the throttle valve 3.
The temperature (TA) sensor 8 is mounted, and the detection signal
Is supplied to the ECU 5. With the throttle valve 3 of the intake pipe 2
A chamber 9 is provided between the intake manifolds 11.
The chamber 9 has an intake pipe absolute pressure (PBA) sensor
10 is attached. Detection signal of PBA sensor 10
The signal is supplied to the ECU 5. The main body of the engine 1 has an engine water temperature (T
W) The sensor 13 is mounted, and the detection signal is EC
It is supplied to U5. The ECU 5 includes a crank of the engine 1.
Crank angle position that detects the rotation angle of the shaft (not shown)
Position sensor 14 is connected and the rotation angle of the crankshaft
Is supplied to the ECU 5. Crank angle position
The position sensor 14 detects a predetermined cylinder of a specific cylinder of the engine 1.
Signal pulse (hereinafter referred to as “CYL signal pulse”)
Cylinder sensor that outputs a signal, the intake stroke of each cylinder is opened
A predetermined crank angle before the top dead center (TDC)
At the rank angle position (for a 4-cylinder engine, the crank angle is 18
TDC sensor that outputs TDC signal pulse (every 0 degrees) and
And a constant crank angle cycle shorter than the TDC signal pulse (for example,
1 pulse per 30 degrees cycle (hereinafter "CRK signal pulse")
) Which generates a CYL signal
Pulse, TDC signal pulse and CRK signal pulse are EC
It is supplied to U5. These signal pulses are used during fuel injection.
Timing, ignition timing, etc. and engine rotation
Used to detect several NEs. A little upstream of the intake valve of the intake manifold 11
Is provided with a fuel injection valve 12 for each cylinder.
The injection valve is connected to a fuel pump (not shown).
Is electrically connected to the ECU 5 and a signal from the ECU 5
Controls the fuel injection timing and fuel injection time (valve opening time)
Is controlled. Engine 1 spark plug (not shown) is also EC
It is electrically connected to U5, and when ignition is performed by ECU5.
The period θIG is controlled. The exhaust pipe 16 has a branch portion (exhaust manifold) 1
5 is connected to the combustion chamber of the engine 1. exhaust
In the pipe 16, immediately downstream of the part where the branch part 15 gathers,
Wide area air-fuel ratio sensor (hereinafter referred to as "LAF sensor") 17
Is provided. Further downstream of the LAF sensor 17
Is provided with a three-way catalyst 19 immediately below and a three-way catalyst 20 below the floor.
Oxygen concentration between these three-way catalysts 19 and 20
A degree sensor (hereinafter referred to as “O2 sensor”) 18 is attached.
ing. The three-way catalysts 19 and 20 are used to remove HC, C in exhaust gas.
Purifies O, NOx, etc. The LAF sensor 17 includes a low-pass filter 2
2 is connected to the ECU 5 through the
Outputs an electrical signal approximately proportional to the elemental concentration (air-fuel ratio)
An electric signal is supplied to the ECU 5. The O2 sensor 18 is
Characteristics of the output of the engine suddenly change before and after the stoichiometric air-fuel ratio
The output is high level on the rich side from the stoichiometric air-fuel ratio
And the level is low on the lean side. O2 sensor 18
Is connected to the ECU 5 via the low-pass filter 23.
The detection signal is supplied to the ECU 5. Exhaust return
The flow mechanism 30 connects the chamber 9 of the intake pipe 2 and the exhaust pipe 16 to each other.
An exhaust gas recirculation path 31 to be connected
Exhaust gas recirculation valve (EGR valve) that controls the amount of exhaust gas recirculation
32 and the valve opening of the EGR valve 32, and the detection signal
And a lift sensor 33 that supplies the ECU 5 to the ECU 5. E
The GR valve 32 is an electromagnetic valve having a solenoid.
The solenoid is connected to the ECU 5 and its valve opening is
It can be changed linearly by these control signals
It is configured as follows. In the fuel vapor processing apparatus 40, the fuel tank 4
1 communicates with the canister 45 through the passage 42,
The star 45 is connected to the chamber of the intake pipe 2 through the purge passage 43.
9 in communication. The canister 45 includes the fuel tank 41
Built-in adsorbent that adsorbs fuel vapor generated inside
Has an intake. In the middle of the passage 42, a positive pressure valve and
A two-way valve 46 composed of a negative pressure valve is provided,
In the middle of the storage passage 43, a duty control type solenoid valve is provided.
A purge control valve 44 is provided. Purge control valve 4
Numeral 4 is connected to the ECU 5 and a signal from the ECU 5
It is controlled according to. Further, the ECU 5 has a large pressure detecting device for detecting atmospheric pressure.
An atmospheric pressure (PA) sensor 21 is connected, and the detection signal
The signal is supplied to the ECU 5. The ECU 5 receives input from the various sensors described above.
Correct the voltage level to a specified level by shaping the force signal waveform
To convert analog signal values to digital signal values.
An input circuit having a function, a central processing circuit (CPU),
Various arithmetic programs executed by the CPU and various
From ROM and RAM for storing maps and calculation results
Storage circuit and various solenoid valves such as the fuel injection valve 12 and ignition
And an output circuit for outputting a drive signal to the plug. The ECU 5 controls the various engine operation parameters described above.
Based on the meter signal, LAF sensor 17 and O2 sensor
The feedback control operation range and
Discriminates various engine operation states such as open control operation area
And, depending on the engine operating state,
The fuel injection time TOUT of the fuel injection valve 12 is calculated from
A signal for driving the fuel injection valve 12 based on the calculation result
Is output. [0021] TOUT (N) = TIMF × KTOTAL × K
CMDM × KLAF Here, N represents a cylinder number, and a parameter to which the number is attached
Is calculated for each cylinder. In this embodiment, the engine
Is calculated as the fuel injection time.
Corresponds to the amount of fuel to be injected.
It is also called the amount of radiation or fuel. KTOTAL is the engine coolant temperature TW.
Water temperature correction coefficient KTW, exhaust gas set according to
EGR correction set according to exhaust gas recirculation amount during recirculation execution
Execution of purge by coefficient KEGR, evaporative fuel processor 40
Correction coefficient K set according to the amount of purge fuel
Multiply all feedforward correction factors such as PUG
KCMDM is a correction coefficient calculated by
Is the final target air-fuel ratio coefficient, and KLAF is the LAF sensor 17
This is a PID correction coefficient calculated according to the output. In this embodiment, the fuel injection time TO
Functions such as calculation of UT (N) are performed by the CPU of the ECU 5.
Since it is realized by arithmetic processing, the flow chart of this processing
The details of the processing will be described in detail with reference to the flowchart. FIG. 2 shows a graph corresponding to the output of the LAF sensor 17.
Flowchart of processing for calculating PID correction coefficient KLAF
It is. This process is executed every time a TDC signal pulse is generated.
It is. In step S1, whether or not the engine is in the start mode is determined.
That is, it is determined whether cranking is in progress or not, and
Then, the process proceeds to the process of the start mode (step S11).
If not in start mode, target air-fuel ratio coefficient (target equivalent ratio)
Calculation of KCMD and final target air-fuel ratio coefficient KCMDM
Step S2) and perform the LAF sensor output selection process (step S2).
Calculate the detected equivalent ratio KACT together with step S3)
(Step S4). The detection equivalent ratio KACT is the LAF sensor.
The output of the sensor 17 is converted into an equivalent ratio. Next, activation of the LAF sensor 17 is completed.
It is determined whether or not the activity has occurred (step S5). this is,
For example, the output voltage of the LAF sensor 17 and its center voltage
The difference is compared with a predetermined value (for example, 0.4 V), and the difference is determined as a predetermined value.
If it is smaller, it is determined that activation has been completed.
You. Next, the engine operating state is determined by the LAF sensor 17.
Operating area to execute feedback control based on the output of
(Hereinafter referred to as “LAF feedback area”)
It is determined whether or not it is (step S6). This is, for example, L
Activation of AF sensor 17 is completed and fuel cut
LAF feed when not running or when throttle is not fully open
This is to determine the back area. As a result of this determination, L
Reset flag F when not in AF feedback area
Set KLAFRESET to “1” and set the LAF feed
When it is in the back area, it is set to “0”. In the following step S7, a reset flag F
It is determined whether or not KLAFRESET is “1”, and
If FRESET = 1, the flow advances to step S8 to set PI
While setting the D correction coefficient KLAF to “1.0”,
The integral term KLAFI of the PID control is set to “0” and
The process ends. When FKLAFRESET = 0
Calculates the PID correction coefficient KLAF (step
S10), this process ends. Next, the PI in step S10 in FIG.
The D correction coefficient KLAF calculation process is described in the flowcharts of FIGS.
This will be described with reference to FIG. The processing in FIGS.
It is executed every time a pulse is generated. In step S701, the target equivalent ratio KCM
D and the detected equivalent ratio KACT, the deviation DKAF (k) (= K
CMD (k) -KACT (k)) and calculate the LAF
The monitor permission condition for executing the response degradation determination of the
A flag FLFMCHK indicating that the condition has been established at "1"
It is determined whether or not "1" is set (step S7).
02), when set to “1”, stoichiometric deterioration
Flag FLFSTE indicating that the determination has been completed by "1"
It is determined whether or not ND is set to “1” (step
Step S703). As a result, in step S702, FLF
When MCHK = 0, and F in step S703
If LFSTEND = 0, step S
P term (proportional term), I term (integral term) and D
Calculation process of PID correction coefficient KLAF by term (differential term)
I do. On the other hand, in step S703, FLFSTEND =
If it is 1, the P term and I
Calculation processing of the PID correction coefficient KLAF using only the term
U. First, the PI performed in step S704 and subsequent steps
The D correction coefficient KLAF calculation processing will be described. Step S7
04, the count value NITDC of the predetermined thinning number NI
Determines whether or not has become 0, and if it has not yet become 0
This time the count value NITDC minus 1
(Step S705), the current deviation
Let DKAF (k) be the previous deviation DLKF (k-1)
(Step S706), this processing ends. On the other hand, in step S704, the count value NI
When TDC = 0, the proportional control gain KP and the integral
The control gain KI and the differential control gain KD are set to engine rotation.
From the map according to the number NE and the absolute pressure PBA in the intake pipe
Search and determine the number of thinnings NI (step S
707). Next, the calculated deviation DKAF (k) and
And the control gains KP, KI, and KD are applied to the following equations,
The proportional term KLAFP (k), the integral term KLAFI (k) and
And the derivative term KLAFD (k) are calculated (step S70).
8). KLAFP (k) = DKAF (k) × KP KLAFI (k) = DKAF (k) × KI + KLAF
(K-1) KLAFD (k) = (DKAF (k) −DKAF (k−
1)) × KD In the following steps S709 to S715, the above calculated product
A limit process is performed on the term KLAFI (k). Sand
The upper limit value KLAFIL of the limit value KLAFILMT
MTH and the lower limit KLAFILMTL are calculated (step
S709), the KLAFI (k) value is equal to the predetermined upper / lower limit value KL
AFILMTH, KLAFILMTL
It is determined whether or not it is not (steps S710 and S711), and the KLA
When FI (k)> KLAFILMTH, KLA
FI (k) = KLAFMTH (step
S713), KLAF (k) = KLAFILMTH
(Step S715). On the other hand, KLAFI (k) <K
If LAFILMTL, KLAFI (k) = K
LAFILMTL (step S712),
KLAF (k) = KLAFILML (step S
714). In the following step S716, the following equation is used.
The PID correction coefficient KLAF (k) is calculated. KLAF (k) = KLAFP (k) + KL
AFI (k) + KLAFD (k) Next, in steps S717 to S721, the limit value K
Limit check of KLAF (k) value by LAFLMT
Do That is, in step S717, the limit value
KLAFLMT (KLAFLMT, KLAFLMT
L), and then the KLAF (k) value is increased to a predetermined upper limit value.
It is determined whether or not it is larger than KLAFLMTH (step
S718), KLAF (k)> KLAFLMTH
At this time, KLAF (k) = KLAFLMTH (
Step S721). In step S718, KLAF
When (k) ≦ KLAFLMTH, KLAF
(K) Whether the value is smaller than a predetermined lower limit value KLAFLMTL
Is determined (step S719), and KLAF (k) ≧ K
If LALMTLL, the process proceeds to step S722,
When KLAF (k) <KLAFLMTL, KL
AF (k) = KLAFLMTL (step S72)
0). Steps S714, S715, S72
0 or when the process of S721 ends,
Proceeding to step S722, the thinning number is added to the count value NITDC.
NI and set the current deviation DKAF (k) to the previous deviation
Learning is performed as DKAF (k-1) (step S723).
A value KREF is calculated (step S724), and this processing ends.
Complete. The following steps are performed after step S725.
Calculation of PID correction coefficient KLAF using only P term and I term
The output processing will be described. Here, the detected equivalent ratio KAC will be described with reference to FIG.
T, inversion determination reference value KCMRP, correction coefficient KLAF, etc.
A timing chart showing the relationship between the two will be described.
The figure shows execution of the response deterioration detection processing of the LAF sensor 17.
Time (response indicating "1" indicating that response degradation determination is being executed
When the deterioration determination execution flag FLFRPM is set to “1”
Is shown). Response degradation detection
At the time of execution, ordinary PI using P, I, and D terms
D feedback control is stopped, only P and I terms
Air-fuel ratio control is performed by PI feedback control using
Will be As shown in FIG. 7, the detection equivalent ratio KACT
Hysteresis is set for the inversion determination reference value KCMRP.
The detected air-fuel ratio is reversed from lean to rich
The reference value KCMRPH applied at the time and the detected air-fuel ratio
Reference value KC applied when switching from the switch side to the lean side
The presence or absence of inversion of the detection equivalent ratio KACT is determined by MRPL.
Is determined. Also, as shown in FIG.
FRPM is the detection equivalent ratio KACT is the inversion determination reference value KC
When the value exceeds the MRPH, it is set to “1” and the inversion determination reference value K is set.
Set to “0” when the value falls below CMRPL. PI
Feedback control is based on the product when FAFRPM = 1.
Subtract IRPM from PID correction coefficient KLAF value
While gradually decreasing the KLAF value, FAFRPM = 0
, The integral term IRPM is set to the PID correction coefficient KLAF value.
Integral control for gradually increasing the KLAF value by adding
When the flag FAFRPM is inverted, the proportional term PR
Addition and subtraction of RPM and PLRPM to PID correction coefficient KLAF value
Proportional control. Response of LAF sensor 17
Details of the deterioration method will be described later. Returning to the flowchart of FIG.
At 725, the detected equivalent ratio KACT is equal to the inversion determination reference value KC.
Invert for MRP (KCMRPH, KCMRPL)
And if not reversed, the count value
It is determined whether or not NITDC has become 0 (step S7).
32), if NITDC is not 0, count value NIT
Subtract 1 from DC to obtain the current count value NITDC
(Step S737) The process proceeds to step S735. one
On the other hand, when NITDC = 0 in step S732
Is set to the inversion flag FAFRPM “1”?
It is determined whether or not it is (step S733). Where FAFR
When PM = 0, the detected air-fuel ratio is on the lean side.
Then, the integral term IRPM is added to the PID correction coefficient KLAF (k).
On the other hand (step S)
734) When FAFRPM = 1, the detected air-fuel ratio is
Because it is on the rich side, the PID correction coefficient KLAF (k)
The integral term IRPM is subtracted from the result to obtain the current KLAF (k).
(Step S735), proceeding to step S736,
Set the predetermined value NIRPM of the thinning number to the
And the process proceeds to step S738. In step S725, the detected equivalence ratio KA
CT is inverted with respect to the inversion determination reference value KCMRP
The detected equivalent ratio KACT is equal to the inversion determination reference value KCMR.
It is determined whether it is larger than P (step S726).
When KACT> KCMRP holds as a result of the determination
Is the detection equivalent ratio KACT is the inversion determination reference value KCMRP
That the state was changed from smaller than H to larger
Set the inversion flag FAFRPMC indicated by “1” to “1”
(Step S729), and sets the flag FAFRPM to “1”.
(Step S730), and the PID correction coefficient KL
By subtracting the subtraction proportional term PLRPM from AF (k),
KLAF (k) (step S731) and step S73
After the processing in 736, the process advances to step S738. On the other hand, in step S726, KACT ≦
If it is KCMRP, the flag FAFRPM is set to “0”.
(Step S727), and the PID correction coefficient KLA
F (k) is added with the addition proportional term PRRPM, and this KL
AF (k) (Step S728), Step S73
After the processing of No. 6, the flow advances to step S738. Next, in step S738, KLAF
(K) Whether the value is greater than a predetermined upper limit value KLAFMTH
KLAF (k)> KLAFLMTH
At this time, KLAF (k) = KLAFLMTH (
(Step S741), this processing ends. In step S738, KLAF (k) ≦ K
When LALMTH, the KLAF (k) value is a predetermined value.
It is determined whether or not it is smaller than the lower limit value KLAFMTL (
Step S739), KLAF (k) ≧ KLAFLMTL
If this is the case, the process immediately ends, while KLAF (k)
<KLAFLMTL, KLAF (k) = K
As LAFMTL (step S740), this processing
finish. According to the processing shown in FIGS.
Actual supply air-fuel ratio control by normal PID feedback control
During the line, detection of response deterioration of the LAF sensor 17 is permitted.
When the feedback control is performed, the PID feed
Switch from back control to PI feedback control,
Temporary tracking of target equivalent ratio KCMD to target value
The cycle of the detection equivalent ratio KACT can be slowed down.
Is more clear and accurate, and the LAF
The response deterioration determination of the sensor 17 is easy and accurate. Further, the detection equivalence ratio KACT is lean / return.
Hysteresis is provided for the switch inversion judgment reference value KCMRP.
Therefore, the cycle of the detection equivalent ratio KACT becomes even clearer.
Can be obtained accurately, and
Easy and accurate. PI feedback control and hysteresis
As a result, as shown in FIG.
T means that during degradation monitoring,
Compared to when the amplitude increases, the period becomes longer,
It can be seen that the characteristics are clarified. The following describes the determination of the deterioration of the LAF sensor 17.
Will be described. FIG. 6 is a process for determining the deterioration of the LAF sensor 17.
4 is a flowchart showing the overall configuration of the present embodiment.
It is executed every time (for example, 10 msec). First, in step S501, the start mode is set.
No, that is, whether cranking is in progress or not, start mode
In the case of, this process is immediately terminated. Must be in start mode
For example, the stoichiometric deterioration determination process (step S502)
Deterioration determination processing (step S503) and lean deterioration determination
The processing (step S504) is sequentially executed. And
Stoichiometric deterioration indicating "1" indicating that the toiki deterioration has been detected.
It is determined whether or not the flag FLFSTNG is “1” (step
In step S505), when FLFSTNG = 0, the response is deteriorated.
Response degradation flag FLFR indicating that "1" has been detected
It is determined whether or not PNG is "1" (step S506),
When FLFRPNG = 0, it indicates that lean deterioration has been detected.
And the lean deterioration flag FLFLNNG indicating “1”
It is determined whether it is "1" (step S507). As a result, in steps S505 to S507,
Either answer is affirmative (YES) and some degradation
Is detected, the LAF sensor 17 has deteriorated.
The OK flag FOK61 that indicates that there is no “1” is set to “0”.
(Step S511), and set the counter C61M to
Increment by "1" (step S512),
This processing ends. On the other hand, the answer of steps S505 to S507 is
If all are negative (NO), the stoichiometric deterioration determination process
A stoichiometric deterioration determination end flag FLF indicating the end by “1”
It is determined whether or not STEND is "1" (step S50).
8) If FLFSTEND = 1, response degradation determination processing
Response degradation determination end flag FLF indicating the end of the process by "1"
It is determined whether RPEND is “1” (step S50)
9). As a result, the answer in step S508 or S509 is
If the determination is negative (NO), the process is immediately terminated, while
Affirmatively based on the answers of steps S508 and S509 (YE
In the case of S), the OK flag FOK61 is set to "1".
(Step S510), and proceeds to Step S512.
No. FIG. 8 shows the processing executed in step S503 of FIG.
It is a flowchart of a response deterioration determination process performed. First, in step S551, response deterioration determination
It is determined whether or not the end flag FLFRPEND is “1”,
When FLAFRPEND = 0, the monitor permission condition flag
It is determined whether or not FLFMCHK is “1” (step S
552), FLFMCHK = 1 and monitor condition satisfied
The time is set in the processing of FIG.
Response degradation judgment indicating that the start condition is satisfied by "1"
It is determined whether or not the start flag FLFRPMS is “1”.
(Step S553). As a result, the response deterioration judgment is completed.
(FLFRPEND = 1), monitor permission condition
When the condition is not satisfied (FLFMCHK = 0) or response deterioration
When the judgment start condition is not satisfied (FLFRPMS = 0),
Response degradation indicating "1" indicating that response degradation determination is being executed
Determination execution flag FLFRPM and inversion flag FAFR
PMC is set to “0” (step S554), and
End the process. On the other hand, if the answer in step S553 is affirmative (YE
In the case of S), the inversion flag FAFRPMC is set to “1”.
It is determined whether or not F is set (step S555).
When AFRPMC = 0, this process is immediately terminated,
On the other hand, when FAFRPMC = 1, the inversion flag FAF
The RPMC is set to "0" (step S556). Next
The response deterioration determination execution flag FLFRPM is set to "1".
(Step S557), and the previous flag FLFR
It is determined whether or not PM is "1" (step S55).
8). And when FLFRPM was 0 last time
Is a counter NWAVE and an up-count timer tm
WAVE is set to "0" (steps S559 and S5).
60), end this processing. In step S558, FLFRPM was also used last time.
If = 1, set the counter NWAVE to "1"
Increment (step S561), timer tm
Determines whether the value of WAVE exceeds a predetermined time TMWAVE.
It is determined (step S562). tmWAVE <TMW
If it is AVET, this process is immediately terminated and tmW
When AVE> TMWAVET, the frequency
The period tmCYCL is calculated (step S563). TmCYCL = tmWAVE / NWAVE In a succeeding step S564, the cycle tmCYCL is set to a predetermined cycle.
It is determined whether or not the period is shorter than tmCYCLOK.
If CL <tmCYLOK, end flag FLFRP
With END set to “1” (step S566)
And the deterioration determination execution flag FLFRPM is set to “0”.
Then (step S567), the present process ends. On the other hand, in step S564, tmCYCL
If ≧ tmCYCLOCK, it is determined that the response has deteriorated.
The response deterioration determination flag FLFRPNG to "1"
(Step S565), and then proceed to step S566.
No. According to the processing of FIG. 8, the predetermined time T
In MWAVE, the differential complement of the PID correction coefficient KLAF
Hysteresis of reference value KCMRP for positive / inhibited and reverse judgment
The cycle of the detection equivalent ratio KACT clarified by the
The response of the LAF sensor 17 is calculated based on this cycle.
Deterioration is easily and accurately determined. FIG. 9 shows the response deterioration of the above-mentioned LAF sensor.
Flowchart of a process for determining a monitor permission condition for determination
This processing does not execute high-priority processing.
Runs in the background. First, in step S572, the O2 sensor 1
8 is in an active state, an activation flag nO indicating "1"
Determine whether 2R is “1” or not, and when nO2R = 1
Is the driving condition of the engine 1 and the vehicle equipped with the engine 1.
It is determined whether the state is in a predetermined area (step S5).
73). That is, when the engine coolant temperature TW is equal to the predetermined upper / lower limit value T,
Whether it is within the range of WLAFMH, TWLAFML,
When the intake air temperature TA is a predetermined upper / lower limit value TALAFMH, TALAF
Whether the engine speed NE is within the range of ML or not is predetermined.
Within the range of the upper and lower limit values NELAFMH and NELAFML.
Whether the intake pipe absolute pressure PBA is equal to the predetermined upper / lower limit value PBL
Whether it is within the range of AFMH, PBLAFML and vehicle
Speed V is in the range of predetermined upper and lower limit values VLAFMH, VLAFML
Is determined, the answer to all the determinations is affirmative (Y
ES), it is determined that the operating state is in a predetermined area.
You. In that case, the vehicle is further
"1" indicates that the vehicle is in a cruise state where the speed change rate is small
It is determined whether or not the flag FCRS indicated is “1” (step
S574) If FCRS = 1, the reset flag F
It is determined whether or not KLAFRESET is “0” (step
S575). As a result of the above determination, steps S572 to S572
If any of 575 is negative (NO), monitor
When it is determined that the condition is not satisfied, the process proceeds to step S580, and the purge is performed.
Purge cut flag FL indicating "1" to be cut
AFPG is set to “0”, then the down count timer t
Set TLFMCHK to mLFMCHK for a predetermined time.
The process is started (step S581), and the monitor permission condition
The lag FLFMCHK is set to "0" (step S58).
3), when the countdown timer tmLFRPMS has been set
Between TLFRPMS and start (step
S586), and sets the response deterioration determination start flag FLFRPMS
It is set to “0” (step S588), and this processing ends.
I do. Also, at step S575, FKLAFRE
SET = 0 and the air-fuel ratio feedback control region
When there is, the monitor permission condition flag FLFMCHK
It is determined whether or not “1” (step S576), and FLFM
If CHK = 1, the process immediately proceeds to step S578.
On the other hand, when FLFMCHK = 0, the target equivalent ratio
KCMD is a predetermined value KCMDZML (for example, the stoichiometric air-fuel ratio
Corresponding value, ie set to 1.0) or not
Is determined (step S577). And KCMD <
If KCMDZML, the monitor permission condition is not satisfied.
The determination proceeds to step S580, where KCMD ≧ KC
If it is MDZML, the process proceeds to step S578. In step S578, the response deterioration determination ends.
It is determined whether or not the flag FLFRPEND is “1”, and FL is determined.
When FRPEND = 1 and the judgment is completed,
Proceed to step S580. FLFRPEND = 0
, The purge cut flag FLAFPG is set to
Purge cut is set to "1" (step S57).
9), the timer tm started in step S581
It is determined whether the value of LFMCHK is “0” (step
S582). At first, tmLFMCHK> 0
Proceeding to step S583, tmlFMCHK = 0 is set.
Is reached, it is determined that the monitor permission condition for the response deterioration determination is satisfied.
The flag FLFMCHK is set to “1” (step S
584), the stoichiometric deterioration determination end flag FLFSTEN
It is determined whether D is "1" (step S585). As a result, if FLFSTEND = 0,
If the stoichiometric deterioration determination has not been completed,
Proceeding to step S586, the stoichiometric deterioration determination ends and the FLF
When STEND = 1, the process proceeds to step S587 and the process proceeds to step S587.
Timer tmLFRPMS started in step S586
It is determined whether or not the value is “0” (step S587).
Initially, tmFRPMS> 0, so
Proceed to step S588, and when tmFRPMS = 0,
The answer deterioration judgment start flag FLFRPMS is set to "1".
(Step S589), start of response deterioration determination is permitted
You. As described above, according to the present embodiment,
Controlling supply air-fuel ratio by PID feedback control
Proportional control in the air-fuel ratio control device by prohibiting differential control
And by performing only integral control
Easy and accurate based on the detected equivalent ratio KACT cycle
In addition, it is possible to determine the response deterioration of the LAF sensor 17. The result
As a result, the emission characteristics and
The problem that drivability deteriorates can be avoided.
You. [0070] The air-fuel ratio control device according to claim 1 of the present invention.
According to the above, the acid contained in the exhaust gas provided in the exhaust system of the internal combustion engine
Air-fuel ratio detecting means for outputting a value proportional to the elemental concentration;
Of the fuel ratio detection meansResponse degradation that allows detection of response degradation
Responsiveness by the detection permission means and the response deterioration detection permission means
The air-fuel ratio detecting means when the detection of deterioration of the air-fuel ratio is permitted.
Output and reference value for reversal judgment with hysteresisWhen
By comparing the air-fuel ratio of the air-fuel mixture supplied to the engine with a proportional term
Air-fuel ratio feedback control
Feedback control means;The air-fuel ratio feedback control means
During the air-fuel ratio controlThe output of the air-fuel ratio detecting means
of powerFor the inversion determination reference valueCalculate inversion cycle
Reversal period calculating means, and
Of the air-fuel ratio detecting means based on the determined reversal cycle.Responsive
And a deterioration detecting means for detecting deterioration.So easy and
Accurate detection of air-fuel ratio sensor responsiveness degradation
You. [0071]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to one embodiment of the present invention. FIG. 2 is a flowchart of a process for calculating an air-fuel ratio correction coefficient based on an LAF sensor output. FIG. 3 is a flowchart of a PID correction coefficient (KLAF) calculation process. FIG. 4 is a flowchart of a PID correction coefficient (KLAF) calculation process. FIG. 5 is a flowchart of a PID correction coefficient (KLAF) calculation process. FIG. 6 is a flowchart illustrating an overall configuration of a LAF sensor deterioration determination process. FIG. 7 is a detection equivalent ratio KACT, a reference value KCM for inversion determination.
FIG. 9 is a diagram showing a timing chart between RP, a correction coefficient KLAF, and the like. FIG. 8 is a flowchart of a response deterioration determination process of the LAF sensor. FIG. 9 is a flowchart of a process for determining a monitor permission condition for determining a response deterioration of the LAF sensor. [Description of Signs] 1 Internal combustion engine (main body) 2 Intake pipe 5 Electronic control unit (ECU) 12 Fuel injection valve 16 Exhaust pipe 17 Wide area air-fuel ratio sensor

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Katsushi Watanabe               1-4-1 Chuo, Wako-shi, Saitama               Inside Honda Technical Research Institute (72) Inventor Yukio Noda               1-4-1 Chuo, Wako-shi, Saitama               Inside Honda Technical Research Institute                (56) References JP-A-6-50200 (JP, A)                 JP-A-4-365950 (JP, A)                 JP-A-4-204047 (JP, A)                 JP-A-4-10951 (JP, A)                 JP-A-7-23181 (JP, A)

Claims (1)

(57) Claims: 1. An air-fuel ratio detecting means provided in an exhaust system of an internal combustion engine and outputting a value proportional to the oxygen concentration in exhaust gas;
A response permitting detection of deterioration of responsiveness of the air-fuel ratio detecting means.
The response detection means and the response deterioration detection permission means.
Air-fuel ratio detection when the detection of response deterioration is permitted
Reversal judgment reference provided with means output and hysteresis
And air-fuel ratio feedback control means for feedback controlling the proportional term and the integral term of the air-fuel ratio of a mixture supplied to said engine by comparing the value, the air-fuel ratio feedback system
A reversal cycle calculating means for calculating a reversal cycle of the output of the air-fuel ratio detecting means with respect to the reversal determination reference value during the air-fuel ratio control by the control means; and Response of fuel ratio detection means
An air-fuel ratio control device comprising: a deterioration detecting unit that detects deterioration of performance .