JP3403801B2 - Exhaust system temperature estimation device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the temperature of an exhaust system of an internal combustion engine.
The present invention relates to an exhaust system temperature estimating device for estimating the temperature. [0002] 2. Description of the Related Art Conventionally, this type of exhaust system temperature estimating apparatus is known.
As disclosed in JP-A-63-97848,
Method for estimating the temperature of a catalyst disposed in an exhaust system of a fuel engine
It has been known. In this method for estimating the catalyst temperature, the catalyst temperature
Degree is the basic fuel amount VAUP, engine speed NE and start
Determined from the cooling water temperature TW during operation, and change in catalyst temperature
The speed ΔCTMP is calculated based on the basic fuel amount VAUP and the engine speed.
NE and the total is estimated from the map with the NE.
When the catalyst temperature reaches the maximum catalyst temperature (constant value),
It is shown that the guard is kept at a large value. Further, Japanese Patent Application Laid-Open No. 1-219340 discloses
Is an oxygen concentration sensor, etc., arranged in the exhaust system of an internal combustion engine.
When estimating the temperature of the exhaust system parts,
Is calculated over time, and the integrated value is
It is shown that the correction is made by the air temperature. Further, Japanese Patent Application Laid-Open No. Sho 62-203965 has been disclosed.
To estimate the temperature of the exhaust gas
Temperature time constant set based on the
To correct the steady temperature. [0005] [Problems to be solved by the invention]
Further improvement of estimation accuracy of exhaust system temperature for the following reasons
Is desired. That is, JP-A-63-97848
The catalyst temperature estimation method shown in
Keeps constant value when the catalyst temperature exceeds the maximum catalyst temperature
It is just guarding, and the catalyst is
No consideration is given to cooling. [0006] Japanese Patent Application Laid-Open No. 1-219340 discloses that
Setting the temperature of exhaust system components to a steady temperature is disclosed.
Not. Correction for steady-state temperature using intake air temperature
The value is corrected, but the running wind that changes according to the vehicle speed is considered.
Not considered. Further, Japanese Patent Application Laid-Open No. 62-203965 is disclosed.
In order to predict the temperature of the exhaust gas purification device,
Correcting the degree with the intake air amount Qa and the air-fuel ratio A / F
Is disclosed, but the catalyst is cooled by the running wind
That is not taken into account. [0008] Accordingly, the present invention provides a method for controlling a set steady temperature.
Of the exhaust system temperature by considering the traveling wind
Temperature estimation of the internal combustion engine that can further improve the temperature
It is intended to provide a fixing device. [0009] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The exhaust system temperature estimation of the internal combustion engine according to claim 1 of the present invention
The device is based on operating conditions of the internal combustion engine, including at least the load.
Calculating the steady-state temperature of the exhaust system of the internal combustion engine.
Temperature calculation means, at least a load of the internal combustion engine
Based on the operating state, the exhaust system temperature is
Following speed calculating means for calculating the following speed;
The exhaust system temperature based on the temperature and the following speed
In an exhaust system temperature estimation device for an internal combustion engine,The steady temperature
The correction coefficient for correcting the air-fuel ratio of the internal combustion engine is rich.
Setting means for setting a smaller value asThe internal combustion engine
Intake temperature detection means for detecting the intake air temperature of the Seki, and vehicle speed detection
Vehicle speed detecting means, and the detected intake air temperature and the detected
The steady-state temperature based on the vehicle speed and/ OrFollowing speed
Correction means for performing correction. [0010] [0011] The exhaust system temperature estimating apparatus according to claim 1 of the present invention.
Is based on at least the operating state of the internal combustion engine, including the load.
The steady-state temperature of the exhaust system of the internal combustion engine by the steady-state temperature calculating means.
Operating the internal combustion engine including at least a load
Before the exhaust system temperature by the following speed calculation means based on the state
The following speed for the steady temperature is calculated, and the steady temperature and the
And estimating the exhaust system temperature based on the following speed and
ToCorrecting the steady-state temperature with the air-fuel ratio of the internal combustion engine,Sucking
The air temperature of the internal combustion engine is detected by an air temperature detecting means,
Speed detection means for detecting a vehicle speed, and detecting the detected intake air
Correction means based on the temperature and the vehicle speed.
Degree and/ OrCorrect the following speed. [0012] [0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust system temperature estimating apparatus for an internal combustion engine according to the present invention will be described below.
Embodiments will be described with reference to the drawings. FIG. 1 shows an exhaust system temperature estimating apparatus according to this embodiment.
An internal combustion engine equipped with an air-fuel ratio control device
Is referred to as an “engine”).
In the middle of the intake pipe 2 of the engine 1 of the cylinder, a throttle valve 3 is provided.
Is provided. Throttle valve open for throttle valve 3
Degree (θTH) sensor 4 is connected to the slot
Electronic signal according to the opening of the
To a control unit (hereinafter referred to as “ECU”) 5. The fuel injection valve 6 includes the engine 1 and a throttle valve.
3 and slightly upstream of an intake valve (not shown) of the intake pipe 2.
Are provided for each cylinder, and each injection valve is
Connected to the charge pump and electrically connected to the ECU 5.
Subsequently, the fuel injection time is determined by a signal from the ECU 5.
(Valve opening time) is controlled. On the other hand, immediately downstream of the throttle valve 3, the intake air
An absolute pipe pressure (PBA) sensor 7 is provided.
The absolute pressure signal converted into an electric signal by the counter pressure sensor 7 is
It is supplied to the ECU 5. Also, downstream of the intake air temperature
(TA) Sensor 8 is attached to detect intake air temperature TA.
And outputs a corresponding electric signal to supply to the ECU 5
You. The engine water mounted on the main body of the engine 1
The temperature (Tw) sensor 9 is composed of a thermistor, etc.
Detects the water temperature (cooling water temperature) Tw and outputs the corresponding temperature signal
Power is supplied to ECU5. Engine speed (NE)
The sensor 10 and the cylinder identification (CYL) sensor 11
Attached around the camshaft or crankshaft (not shown)
Have been. The engine speed sensor 10
Predetermined crank angle position every 180 degree rotation of crankshaft
Output pulse (hereinafter referred to as "TDC signal pulse")
The cylinder discriminating sensor 11 detects a predetermined crank of a specific cylinder.
It outputs a signal pulse at an angular position.
Each signal pulse is supplied to the ECU 5. The catalytic converter (three-way catalyst) 14 is an engine.
H in the exhaust gas.
Purification of components such as C, CO and NOx is performed. Exhaust pipe 13
On the upstream side and downstream side of the catalytic converter 14, respectively.
Oxygen concentration sensors 15 and 16 (hereinafter referred to as air-fuel ratio sensors)
"Upstream O2 sensor 15" and "Downstream O2 sensor
16 ”), and these O2 sensors
The sensors 15 and 16 detect the oxygen concentration in the exhaust gas, and
An electric signal corresponding to the output value is output and supplied to the ECU 5. Sa
Further, the temperature TCAT of the catalytic converter 14 is detected.
The catalyst temperature sensor 17 is mounted, and the detection signal is
It is supplied to the ECU 5. The ECU 5 further detects the atmospheric pressure PA.
Vehicle of a vehicle equipped with the atmospheric pressure sensor 31 and the engine 1
A vehicle speed sensor 32 for detecting the speed VH is connected.
The detection signals of these sensors are supplied to the ECU 5. The ECU 5 receives input signal waveforms from various sensors.
To correct the voltage level to a predetermined level,
An input that has the function of converting signal values to digital signal values, etc.
The power circuit 5a and a central processing unit (hereinafter referred to as “CPU”)
U) 5b, various arithmetic programs executed by the CPU 5b
Storage means 5c for storing calculation results and the like, the fuel injection
An output circuit 5d for supplying a drive signal to the valve 6, and the like.
You. The CPU 5b is used to control the above-mentioned various engine parameters.
Air-fuel based on the oxygen concentration in the exhaust gas
Feedback control to control the ratio
To determine various engine operating conditions such as
And the TDC signal according to the engine operating state.
Fuel injection injected by the fuel injection valve 6 in synchronization with the pulse
The radiation amount Tout is calculated. The CPU 5b outputs a drive signal for the fuel injection valve 6.
Output through the power circuit 5d and a catalytic converter
The deterioration determination of No. 14 is performed. [Overall Control Processing of First Embodiment] FIG.
Outline of overall control processing in the air-fuel ratio control device of the embodiment
FIG. The air-fuel ratio controller determines the catalyst temperature
The process of estimating TCAT (process 1) and the process of
Processing for estimating deterioration (processing 2) and catalytic converter 14
For estimating the maximum oxygen storage amount O2MAX of the water (process 3)
And processing to correct the maximum oxygen storage amount O2MAX (Process 4)
And the air-fuel ratio A / F on the upstream side of the catalytic converter 14 is estimated.
Processing (processing 5), and stored in the catalytic converter 14.
Process for estimating the stored oxygen storage amount O2STR (Process 6)
And the oxygen utilization rate O2USER of the catalytic converter 14 is calculated.
Processing (processing 7) and the air-fuel mixture supplied to the engine 1
Air-fuel ratio A / F is forcibly vibrated (perturbation)
To control the air-fuel ratio A / F by performing
And change rate of perturbation frequency and amplitude
(Process 9) and calculate the air-fuel ratio correction coefficient KO2
(Process 10) and calculate the injected fuel amount Tout
Processing (processing 11).
1 and the state of the catalytic converter 14 (temperature,
Oxygen consumption of the catalytic converter 14 according to the degree of deterioration and capacity).
Force the air-fuel ratio A / F to maximize the usage rate O2USER
The purification rate of the catalytic converter 14
The feature is to maximize it. The maximum oxygen storage amount O2 of the catalytic converter 14
In the process for estimating MAX (process 3), the catalyst temperature TCAT,
The catalyst conversion depends on the deterioration of the medium and the capacity (volume) of the catalyst.
The maximum oxygen storage amount O2MAX of the data 14 is calculated. Catalyst temperature
Degree TCAT, catalyst degradation and catalyst temperature out of catalyst capacity
TCAT may be detected directly by the catalyst temperature sensor 17.
In the process of estimating the catalyst temperature TCAT as described later,
Alternatively, it may be calculated. In addition, the deterioration of the catalyst will be described later.
It may be calculated by a process of estimating deterioration. In addition,
The capacity of the medium is a fixed value determined by the size of the catalyst.
It can be stored in advance in the storage means 5c. Calculation
The calculated maximum oxygen storage amount O2MAX is calculated as the oxygen storage amount O2STR.
In addition to acting as a limit when exiting, maximum oxygen accumulation
When the amount exceeds O2MAX, exhaust gas cannot be purified.
It is also used to subtract the value of oxygen utilization O2USER. In the process for estimating the air-fuel ratio A / F (process 5)
Is the air-fuel ratio A / F is the air-fuel ratio directly from the linear air-fuel ratio sensor
Although the A / F may be detected, in the process 5, the linear air-fuel ratio
Using the output of the upstream O2 sensor 15 without using the sensor
To calculate the air-fuel ratio correction coefficient KO2,
The air-fuel ratio A / F is calculated based on the deviation of the positive coefficient KO2 from the center value.
Is calculated. In addition, air-fuel by the O2 sensor 15 on the upstream side
Air-fuel ratio correction coefficient KO2 used for ratio feedback control
Is corrected by the output of the O2 sensor 16 on the downstream side.
The deviation of the air-fuel ratio correction coefficient KO2 from the center value is
You can comb. The oxygen storage amount O2STR of the catalytic converter 14
In the process (process 6) for estimating, the air-fuel ratio A / F becomes lean.
Side, the catalytic converter 14 adsorbs oxygen molecules O2
On the rich side, oxygen molecules O2 are released, so the air-fuel ratio
Depending on the A / F and the displacement, the catalytic converter 14
Calculate the degree to which the child O2 is adsorbed and released, and calculate the oxygen accumulation amount
Calculate O2STR. The calculated oxygen storage amount O2STR is mainly
The maximum oxygen accumulation determined by the capacity of the catalytic converter 14
Limit processing is performed by the amount O2MAX. Also, oxygen storage
When the product O2STR becomes a negative value,
Mitt processing. Processing for calculating the oxygen utilization rate O2USER (processing
In 7), the oxygen utilization rate O, which is a physical quantity corresponding to the purification rate,
2USER is calculated. Oxygen utilization rate O2USER is large
The higher the purification rate of the catalytic converter 14, the higher the oxygen storage amount
When O2STR exceeds the maximum oxygen storage amount O2MAX or
If the value is less than "0", the exhaust gas will not be purified.
In this range, the oxygen utilization rate O2USER is subtracted. The air-fuel ratio A / F perturbation processing (processing
In theory 8), the oxygen stored in the catalytic converter 14
Lower the accumulated amount O2STR from the lower limit O2STRL close to the value "0" to the maximum acid.
It can be done in the range of the upper limit O2STRH close to the elementary storage amount O2MAX
Vibration with a very large amplitude and shorten the cycle of the vibration
To maximize the oxygen storage capacity of the catalyst
The air-fuel ratio so as to increase the purification rate of the catalytic converter 14.
A / F is controlled. Frequency / amplitude change speed setting process (process 9)
Then, the operating state of the engine 1 (space velocity SV),
According to the maximum oxygen storage amount of the inverter 14 (for example, the catalyst temperature).
Change the frequency and amplitude of perturbation
I do. Hereinafter, the contents of each of the processes 1 to 11 will be described in detail.
I do. [Estimation of Catalyst Temperature TCAT (Process 1)] FIG.
Is a flowchart showing a routine for estimating the catalyst temperature TCAT.
It is. In this routine, first, it is determined whether
It is determined (step S210), and if it is at the time of starting, the TA sensor
The intake air temperature TA detected by the fuel cell 8 is used as the initial value of the catalyst temperature TCAT.
This routine is set as the period value (step S220).
finish. When not starting, target estimated catalyst temperature TCA
Calculate the difference ΔTCAT between TOBJ and catalyst temperature TCAT (step
S215) Whether the difference ΔTCAT is larger than the value “0”
Is determined (step S230). FIG. 4 shows the integral T
7 is a graph showing values of coefficients α1 and α2 with respect to OUTSUM.
You. Normally, the catalyst temperature TCAT after startup increases.
△ TCAT is positive, that is, the catalyst temperature TCAT is the target
Fig. 4 when the estimated catalyst temperature TCATOBJ becomes lower than
Search the TOUTSUM / α1 table shown in
Search for coefficient α1 to increase catalyst temperature based on UM
(Step S240). On the other hand, △ TCAT is negative,
The catalyst temperature TCAT is higher than the target estimated catalyst temperature TCATOBJ
If not, search the TOUTSUM / α2 table and
Search coefficient α2 to lower catalyst temperature based on OUTSUM
(Step S250). Where TOUTSUM is unit time
The integrated value of the fuel injection time TOUT per interval
The combustion energy increases as TOUTSUM increases,
The catalyst temperature TCAT also increases. Therefore, the coefficient α
1, α2 is calculated from the average value of injection quantity per unit time.
Indicates the delay time constant of the target catalyst temperature TCATOBJ
1 is a value that decreases as the integrated value TOUTSUM increases.
The number α2 is a value that increases as the integrated value TOUTSUM increases.
You. Subsequently, the correction coefficient Kα of the coefficients α1 and α2
Is determined based on the vehicle speed V and the intake air temperature TA (step
S255). FIG. 6 shows the relationship between the vehicle speed V and the intake air temperature TA.
A graph showing a table for determining the value of the correction coefficient Kα
It is. The correction coefficient Kα increases as the intake air temperature TA increases.
The lower the vehicle speed V is, the larger the value is set. Step S
When the correction coefficient Kα is searched in a table at 255,
Is calculated according to the following equation. [0033] Α = α1 × Kα α = α2 × Kα Next, the basic value TCATOBJ of the target estimated catalyst temperature TCATOBJ
0 as the absolute pressure PBA in the intake pipe and the engine speed NE
A determination is made using a map (not shown) (step S2
60). Furthermore, the air / fuel ratio dependent correction coefficient KA / F
(Step S)
265). This correction factor KA / F is
That is, the smaller the air-fuel ratio of the exhaust system, the easier the catalyst is cooled
So a coefficient to compensate for the cooling effect of such fuel
Depending on the air-fuel ratio of the mixture (corresponding to the air-fuel ratio of the exhaust system)
Is determined. FIG. 7 shows a correction coefficient K according to the air-fuel ratio A / F.
5 is a graph showing a KA / F table for determining A / F.
You. According to the table of FIG. 7, the correction coefficient KA / F is the air-fuel ratio
The value is set to a smaller value as the A / F becomes richer. Next
Then, the correction coefficient KTATCAT is retrieved by searching the KTATCAT table.
Determined based on the temperature TA and the vehicle speed V (step S27)
0). FIG. 5 shows a correction coefficient according to the intake air temperature TA and the vehicle speed V.
7 is a graph showing a table for determining KTATCAT.
You. According to the KTATCAT table of FIG. 5, the intake air temperature TA is low.
The catalytic converter 14 is cooled by outside air
The value of the positive coefficient KTATCAT is also set smaller. Also a car
The higher the speed V, the higher the traveling air volume and the higher the speed from the catalytic converter.
Since the amount of heat release increases, a catalytic converter using outside air
Since the degree of cooling of 14 varies depending on the vehicle speed V,
The value of the correction coefficient KTATCAT is changed according to the speed V. Next, the basic value TCATOBJ0 is calculated according to equation (2).
Multiplied by the retrieved correction coefficients KA / F and KTATCAT
Temperature correction of the catalytic converter 14 cooled by air
To set the target estimated catalyst temperature TCATOBJ (step
S280). [0035] (Equation 2) TCATOBJ = KTATCAT × KA / F × TCATOBJ0 Using the target estimated catalyst temperature TCATOBJ, the catalyst temperature TCA
T (n) is calculated by Expression 3 (Step S29)
0). [0036] TCAT (n) = α × TCAT (n-1) + (1
−α) × TCATOBJ Here, α is the value of α1 in step S240, or
Alternatively, the value of α2 in step 250 is substituted. Ma
TCAT (n-1) is the value of the last execution of this routine.
Is calculated. When the catalyst temperature TCAT is calculated
This routine ends. As described above, the fuel concentration in the air-fuel mixture
Considering the cooling effect based on the air temperature and the vehicle speed, the catalyst temperature
Accurate estimation of the degree TCAT can be performed. In this embodiment, the following speed of the catalyst temperature (α
1, α2) of the fuel injection amount obtained from the engine load
Calculated from the integrated value (TOUTSUM).
It may be directly obtained from the intake pipe internal pressure or the like. [Estimation of Catalyst Degradation (Process 2)]
The performance deterioration of the medium converter 14 is estimated. This catalyst degradation
The judgment method is disclosed in Japanese Patent Application No. 4-359 dated December 26, 1992.
No. 538 has been filed and will be briefly described here.
I do. This catalyst deterioration determination is based on the output of the downstream O2 sensor 16.
For calculating the correction coefficient KO2 based only on the force RVO2.
During the feedback control, the KO2 value is
After the P-term gain PLSP for
Time TL until the flow side O2 sensor output RVO2 is inverted
Term for skipping the KO2 and KO2 values in the increasing direction
The downstream O2 sensor output RVO2 after the occurrence of the in PR
Is measured until the time is inverted, and these times T
This is performed by measuring the average value T of L and TR. This
This is because when the purification rate of the catalyst decreases, the time TL, TR
Utilizing the decrease in the average value T of the
Decrease means a decrease in oxygen storage capacity.
The deterioration of the catalyst can be accurately determined. [Maximum oxygen storage amount O of catalytic converter 14]
Estimation of 2MAX (Process 3)] Maximum oxygen of catalytic converter 14
The accumulated amount O2MAX corresponds to the capacity (volume) of the catalyst as described above.
Then, the catalyst temperature T estimated in the above-described processing 1 and processing 2
It is determined by CAT and the degree of catalyst deterioration. FIG.
Indicates the maximum oxygen storage amount O2MAX with respect to the catalyst temperature TCAT.
It is a graph. Maximum as catalyst temperature TCAT rises
It can be seen that oxygen storage O2MAX increases almost directly in proportion
You. Therefore, the maximum oxygen storage amount of the catalytic converter 14
O2MAX is the maximum per unit volume according to the catalyst temperature TCAT.
The volume of the catalyst and the degree of catalyst deterioration depend on the large oxygen storage amount O2MAX
Is calculated by multiplying Calculated maximum
O2MAX is the feedback control of air-fuel ratio A / F
The maximum oxygen storage amount O2M
The value of AX is modified. Furthermore, the maximum oxygen storage amount O2MAX is
Do not use the entire range by limit processing described later
It has been like that. [Modification of maximum oxygen storage amount O2MAX (processing
4)] FIG. 9 shows a routine for correcting the maximum oxygen storage amount O2MAX.
FIG. This routine is executed for a predetermined time (for example,
For example, this is a timer process executed every 1 second). Book roux
, The oxygen storage amount O of the catalytic converter 14 described later
Tie of reversal of downstream air-fuel ratio A / F estimated from 2STR
Of the inversion detected by the O2 sensor 16 on the downstream side
Maximum oxygen accumulation when the timing is shifted from each other
Judging that the calculated value of O2MAX is different, the maximum oxygen storage
Modify O2MAX. In other words,
Set to value "1" by reversing the specified air-fuel ratio A / F
Flag FSIM and the output of the downstream O2 sensor 16
The flag FREAL, which is set to "1" by force reversal,
Have it ready. Is the output of the downstream O2 sensor 16 inverted?
A certain time before the flag FSIM is set to the value "1".
When the air-fuel ratio on the downstream side is not
When the rotation is slow, the calculated maximum oxygen storage amount O2MAX is large.
Judging that it is too much, the value is reduced by ΔO2MAX.
Also, constant after the flag FSIM is set to the value "1".
If there is no output reversal of the downstream O2 sensor within the time,
It is judged that the value of the calculated maximum oxygen storage amount O2MAX is too small.
That is, the value is increased by O2MAX. This routine is shown in the flowchart of FIG.
To explain, first, the flags FCATO20 and FCATO20
Determine if any of 2MAX is value "1"
(Step S111). Oxygen accumulation shown in FIG. 14 described later
In the amount O2STR calculation routine, the flag FCATO20 is
The lower limit O2S where the oxygen storage amount O2STR of the inverter 14 is close to zero.
Set to “1” when the value is below TRL, or
Is the flag FCATO2MAX is the oxygen storage amount O2STR is the maximum oxygen storage
Value when exceeding the upper limit O2STRH close to the amount O2MAX
Set to "1". Which flag FCATO2MAX, F
When CATO20 is not the value "1", the flag FSIM is set to the value "0".
(Step S112), and the flag FCATO2MAX
When any of the flag and the flag FCATO20 are “1”
Sets the flag FSIM to the value "1" (step S1).
13). Next, the output of the downstream O2 sensor 16 is inverted.
It is determined whether or not it has been performed (step S114). Invert
If not, reset the flag FREAL to the value "0".
(Step S115) If the flag FREAL is inverted,
The value is set to "1" (step S116). Continued
The values of these lags FSIM and FREAL
(Step S117). Flag FSIM
Initial value FSIM (1) of FREAL and present value FREAL of FREAL
It is determined whether each value of (N) is “1” and both values are
When both are "0", the value of the maximum oxygen storage amount O2MAX
This routine is terminated without correcting (Step S
118, step S119). Step S118
The current value of the flag FREAL is "1" and the flag FREAL
When any value of SIM (1 to N) is "1",
This routine without modifying the value of O2MAX
Is completed (step S120). Further, step S
The initial value of the flag FSIM in 119 is “1” and
One of the values of the lag FREE (1 to N-1) is "1".
Without changing the value of the maximum oxygen storage amount O2MAX
This routine ends (step S121). Steps
Any value of the flag FSIM (1 to N) in S120
Is also "0" for the same catalyst temperature TCAT in FIG.
The maximum oxygen storage amount O2MAX by △ O2MAX
Step S122) The value of the maximum oxygen storage amount O2MAX is the lower limit
If the value is lower than the value O2GL (step S123), the maximum oxygen
Limit the value of the accumulated amount O2MAX to the lower limit value O2GL
(Step S124) This routine ends. Steps
Any of the flags FREAL (1 to N-1) in S121
Is also "0" for the same catalyst temperature TCA.
Increase the maximum oxygen storage amount O2MAX by ΔO2MAX
Step S125) The maximum oxygen storage amount O2MAX is the upper limit
If it exceeds O2GH (step S126), the maximum oxygen storage
Limit the value of O2MAX to the upper limit O2GH (
Step S127) This routine ends. [Estimation of Air-fuel Ratio A / F (Process 5)] FIG.
Is a flowchart showing an air-fuel ratio estimation routine. Book
In the routine, a routine for directly outputting the value of the air-fuel ratio A / F is provided.
A) O2 sensor 1 on the upstream side instead of using the air-fuel ratio sensor
5 using the air-fuel ratio correction coefficient KO2 corresponding to the output of
Estimation of air-fuel ratio A / F of exhaust gas flowing into inverter 14
Perform First, the output of the upstream O2 sensor 15 is used.
Whether feedback control of the air-fuel ratio A / F is in progress
Is determined (step S310). Air-fuel ratio feedback
During the lock control, the O2 sensor 15
Therefore, the detected air-fuel ratio (oxygen concentration) is the control center.
Target air-fuel ratio for controlling to match target air-fuel ratio
The weighted average value KO2RMD of the correction coefficient KO2 of
Is calculated (step S320). [0044] KO2RMD = α3 × KO2 + (1
-Α3) × KO2RMD Here, α3 is the first smoother for finding the control center.
Is a number. Further, the upstream side air space immediately before the catalytic converter 14 is used.
The weighted average value KO2REF of the correction coefficient KO2 indicating the fuel ratio is
Considering the delay from the exhaust valve to the catalytic converter 14,
It is calculated by Expression 5 (Step S330). [0046] KO2REF = α4 × KO2 + (1
−α4) × KO2REF Here, α4 is the delay from the exhaust valve to the catalytic converter 14.
This is the second smoothing coefficient taking into account the
It is set to a value larger than the number α3. Second annealing coefficient α
4 is a value determined according to the operating state of the engine.
From the engine speed NE and the intake pipe absolute pressure PBA
Determined by a map (not shown). Further, the weighted average value KO2REF and the downstream
Weight added with deviation width SDλ of control by O2 sensor 16
Fuel-air ratio by calculating the ratio with the average value KO2RMD
Calculate F / A (step S340) and end this routine
Complete. This shift width SDλ is the downstream O2 sensor described later.
Air-fuel ratio feedback control routine using 16 outputs
Is determined according to the output of the O2 sensor 16,
To correct KO2RMD / KO2REFD6 with the width SDλ
The estimated air-fuel ratio does not deviate,
Air-fuel ratio estimation accuracy during transient operation of
You. In step S310, open loop control is performed.
Is determined, the fuel / air ratio F / A is set to a value “1.0”,
Set KO2RMD and KO2REF to predetermined values respectively
(Step S350) This routine ends. [Estimation of the oxygen storage amount O2STR of the catalytic converter]
(Processing 6)] Next, the accumulated data is stored in the catalytic converter 14.
The oxygen storage amount O2STR of the oxygen stored is calculated. In this embodiment
Estimates oxygen storage O2STR from only two components, CO and O2
Build a physical model of the catalytic converter. FIG.
FIG. 3 is a schematic diagram showing a catalytic action of a catalytic converter 14. Touch
In the medium converter 14, the input air-fuel ratio A / F
When it is on the side, CO + O → CO2
When the air-fuel ratio A / F is lean,
An adsorption reaction of O2 → 2O occurs. Therefore, the number
According to Equation 6, when the air-fuel ratio A / F is on the rich side, the release of O2 is performed.
The exit speed is the C of the exhaust gas at the inlet of the catalytic converter 14.
When the air-fuel ratio A / F is on the lean side from the O concentration
O2 adsorption speed at the inlet of the catalytic converter 14
Each is calculated from the O2 concentration of the gas. [0049] ## EQU6 ## -d / dt (O) = k1. [COF] .O2STR d / dt (O) = k2. [O2F]. (O2MAX-O2ST
R) here, Q: Intake air volume O: oxygen storage [COF]: Inlet CO concentration (ppm) [COR]: outlet CO concentration (ppm) [O2F]: Inlet O2 concentration (ppm) [O2R]: Outlet O2 concentration (ppm) d / dt (O): change rate of oxygen storage amount k1, k2: reaction coefficient Coefficients k1 and k2 represent the degree of deterioration (R) and the catalyst temperature TCAT.
Calculated according to equation (7). [0050] [Equation 7] k1 = k1R × k1CAT k2 = k2R x k2CAT Here, k1R, k2R: deterioration coefficient k1CAT, k2CAT: Temperature coefficient As shown in Equation 7, the reaction coefficients k1 and k2 are deteriorated, respectively.
Expressed as the product of coefficients k1R and k2R and temperature coefficients k1CAT and k2CAT
Is done. FIG. 12 shows a deterioration coefficient for determining the reaction coefficients k1 and k2.
A graph showing the values of k1R and k2R and the temperature coefficients k1CAT and k2CAT.
It is rough. From the above equations 6 and 7, the current oxygen storage
The product amount O2STR is obtained. The oxygen storage amount O2STR of the catalytic converter 14
If the value is in the range from the value "0" to the maximum oxygen storage amount O2MAX
The air-fuel ratio at the outlet of the catalytic converter 14 is 14.7
But the oxygen storage amount O2STR is equal to or less than the value "0".
Or when the maximum oxygen storage amount exceeds O2MAX
The air-fuel ratio A / F at the inlet of the
And FIG. 13 shows exhaust gas input to the catalytic converter.
Relationship between air-fuel ratio A / F of gas, CO concentration and O2 concentration
FIG. The air-fuel ratio A / F of the exhaust gas is the air-fuel ratio
If it is more than 14.7, catalytic converter using O2 concentration
A change ΔO2 in the oxygen storage amount O2STR in the fuel cell 14 is calculated and exhausted.
If the air-fuel ratio A / F of the gas is less than 14.7, C
Using the O concentration, the oxygen storage amount O2S in the catalytic converter 14
A change ΔO2 in TR is calculated. Changes in oxygen storage O2STR
The minute △ O2 is the release adsorption rate per unit time. FIG. 14 shows the oxygen accumulation in the catalytic converter 14.
It is a flowchart which shows the calculation routine of quantity O2STR.
In the aforementioned routine for estimating the air-fuel ratio A / F (fuel-air ratio F / A),
Air-fuel ratio A /
F (AFIN) is the stoichiometric air-fuel ratio AFstoich value “1”
It is determined whether or not the value is smaller than 4.7 ”on the rich side (S
Step S410). When the air-fuel ratio A / F is on the rich side
Based on the characteristics shown in FIG.
The O concentration [COF] is searched (step S420). Inspection
Using the searched CO concentration [COF],
-D / dt (O) calculation term on the right side of the equation (k1 · [CO
F] · O2STR) by the space velocity SV
The change amount of the elementary storage amount O2STR △ O2 (−d / dt (O))
It is determined (step S425). Here, the space velocity SV is
It corresponds to the amount of exhaust gas per unit time. Also, the air-fuel ratio
When the A / F is on the lean side, according to the AF / [O2] map
The O2 concentration [O2F] is searched (step S43).
0). Using the retrieved O2 concentration [O2F],
The term (k2 · [O2
F] · CO2MAX-O2STR) by the space velocity SV
と O2 (d / dt)
(O)) is calculated (step S435). Calculated
The change △ O2 is calculated as the oxygen storage amount O calculated up to the previous time.
O2STR (n) in addition to 2STR (n-1)
Is calculated (step S440). Calculated oxygen accumulation
The amount O2STR (n) is lower than the predetermined lower limit O2STRL.
It is determined whether or not it is (step S450). Below
When it is determined that the flag FCATO20 is
Set to “1” and set the flag FCATO2MAX to the value “0”
Reset is performed (step S460). Next, oxygen accumulation
The value “0” is set to the amount O2STR (n) (step S47)
0), end this routine. Oxygen in step S450
When the accumulated amount O2STR (n) falls below a predetermined lower limit O2STRL
If it is determined that there is no oxygen storage amount O2STR
Whether (n) exceeds the predetermined upper limit O2STRH
Is determined (step S480). Determined to exceed
Resets the flag FCATO20 to the value "0"
Then, the flag FCATO2MAX is set to the value “1” (S
Step S490). Next, the oxygen storage amount O2STR (n)
The value of the maximum oxygen storage amount O2MAX is set (step S50).
0), end this routine. In step S480, the acid
Elementary storage amount O2STR (n) exceeds the predetermined upper limit O2STRH
If it is determined that there is no flag F in step S510
Reset both CATO20 and flag FCATO2MAX to value “0”.
To end this routine. The above flag FCATO20
And the flag FCATO2MAX are used in the oxygen utilization calculation routine described later.
Also used in Here, the upper limit value O2STR of the oxygen storage amount O2STR
H and the lower limit O2STRL are changed according to the catalyst temperature TCAT.
It is. FIG. 15 shows the upper limit O2STRH and the catalyst temperature TCAT.
4 is a graph showing values of a lower limit value O2STRL. Anti-catalyst
The response speed changes according to the catalyst temperature TCAT. Ie catalyst
If the temperature is different, the degree of activity of the catalyst changes, and
The components of the active catalyst are different depending on the
Speed varies with temperature. On the other hand, the maximum oxygen storage amount O
2MAX originally depends on the reaction speed of the catalyst, upstream air-fuel ratio, etc.
It is estimated by considering the estimation error.
It cannot be used up to the limit. Also, the estimated maximum oxygen
The accumulation amount is a static value, and the air-fuel ratio varies over time.
Available oxygen storage that can store and release oxygen in engine exhaust gas
The volume, ie the dynamic maximum oxygen storage, is lower. Further
In addition, this dynamic maximum oxygen accumulation varies with the catalyst temperature.
In this embodiment, since it depends on the reaction speed,
The width between the upper and lower limits O2STRH and O2STRL is
Higher at the higher end of the catalyst temperature
You have set. The catalyst temperature TCAT is equal to the engine cooling water.
Since there is a correlation with the temperature Tw, the touch
Upper limit value O2STRH and lower limit value O2STR similarly to the medium temperature TCAT
L may be set. Furthermore, the degree of catalyst deterioration
Therefore, the activation rate of the catalyst also changes, so the reaction rate
It also changes depending on the match. Therefore, only the catalyst temperature TCAT
Not the upper limit O2STRH according to the progress of the degree of catalyst deterioration.
May be changed to narrow the width between the lower limit O2STRL and
No. FIG. 16 shows that a predetermined perturbation is executed.
Wave showing the temporal change of oxygen storage amount O2STR
FIG. The oxygen storage amount O2STR is the air-fuel ratio A / F
O vibrates according to the lean inversion cycle, and the oxygen storage amount O2STR
Is below the lower limit O2STRL or the upper limit O2STRH
When exceeding, each flag FCATO20, FCATO2M
It is shown that AX is set to the value "1". FIG.
In O6USE, O2USE and O2USER will be described later, respectively.
The amount of oxygen used in the catalytic converter 14 and the oxygen
You. [Calculation of oxygen utilization rate O2USER (Process 7)]
The oxygen usage amount O2USE in the catalytic converter 14 is based on the oxygen accumulation.
Equivalent to the time axis along the trajectory of the quantity O2STR
By adding the lengths of the line segments, as shown in Expression 8
Is calculated as follows, but the oxygen storage amount O2STR exceeds the upper limit O2STRH.
If it exceeds or falls below the lower limit O2STRL,
It is subtracted by the positive coefficient Kpenalty. [0058] (Equation 8) The oxygen storage amount O2STR in Equation 8 is almost proportional to Σ | △ O2 |
Therefore, the oxygen usage O2USE is simply calculated as shown in Equation 9.
| △ O2 | is an expression based on the integration. [0059] (Equation 9) Here, ΔT indicates that the oxygen storage amount O2STR is lower than the lower limit O2STRL.
Alternatively, it indicates the cumulative time during which it has exceeded the upper limit O2STRH.
You. The correction coefficient Kpenalty is determined by the flag FCATO2MAX and the flag FCATO2MAX.
And when FCATO20 is set to the value "1"
This is a correction value for lowering the dose value, and
Is determined in consideration of the correlation with the conversion rate. The purification rate of the catalytic converter 14 described above
The oxygen utilization rate O2USER for
You. [0061] (Equation 10) Here, the time T corresponds to the number N of calculations for calculating O2USE.
It is time to do. O2USE is the oxygen accumulation per predetermined time (T)
This is an amount that indicates the amount of change in the amount O2STR, and is related to the purification rate of the catalyst.
Related physical quantities. FIG. 17 is a calculation routine of the oxygen utilization rate O2USER.
FIG. This routine is a timer
This routine is executed a predetermined number of times N
Calculate oxygen utilization O2USER only once every time
It is being done. First, the processing number n does not exceed N times.
It is determined whether or not it is (Step S510). Beyond
When there is no flag FCATO2MAX or flag F
Whether any of CATO20 is set to the value "1"
Is determined (step S520). Both flags
If the value is not set to “1”, the oxygen
Add the amount of change | 利用 O2 |
The oxygen use amount O2USE is set (step S530). Next
In addition, the elapsed time T is increased by ΔT, and the number of times of processing n is set to the value “1”.
Increment (step S540) and end this routine.
Complete. In step S520, the flag FCATO2MAX or
If any of the flags FCATO20 is set to the value "1"
When the correction coefficient Kpenalty is
Subtract from O2USE (step S550), and
In step S540, the elapsed time T is increased by ΔT, and the number of processing times n is set to a value.
This routine is terminated after incrementing "1". Ma
In addition, in step S510, the processing number n reaches the predetermined number N.
The oxygen usage O2USE divided by the elapsed time T
Calculate elemental use rate O2USER and oxygen use amount O2USE
Is reset to the value "0" (step S560). Further
, The elapsed time T and the number of processes n are reset to the value “0”
Then (step S570), this routine ends. The calculation of the oxygen utilization rate O2USER described above is executed.
Then, for example, as shown in FIG.
The oxygen storage amount O2STR in the converter 14 is the maximum oxygen storage amount
O2MAX lower limit O2STRL and maximum oxygen storage O2MAX upper limit
The value O2STRH is repeated, but the maximum oxygen storage amount O2
MAX lower limit O2STRL and maximum oxygen storage O2MAX upper limit O
Correction coefficient Kpenalty because there is an area reaching 2STRH
Is applied and the oxygen usage O2USE goes down,
The usage rate O2USER has a small value. In the range of B,
The oxygen storage amount O2STR in the catalytic converter 14 is equal to the maximum oxygen storage amount.
The lower limit value O2STRL of the accumulation amount O2MAX and the maximum oxygen accumulation amount O2MAX
Oxygen usage O2 because the range between upper limit O2STRH is repeated
USE is increasing and oxygen utilization O2USER is large. C range
In order to increase oxygen utilization O2USER
Although the lean / rich cycle of the
The oxygen storage amount O2STR in the converter 14 is fully utilized.
O2USE is lower than the value in the range of B
You. [Air-fuel ratio control (process 8)]
-Fuel ratio A using oxygen utilization rate O2USER calculated by calculation
Explanation of forced vibration (perturbation) processing of / F
I do. Figure 18 shows the forced oscillation of the air-fuel ratio (perturbation)
6 is a flowchart showing the processing of FIG. FIG.
5 is a timing chart showing a perturbation waveform.
You. First, the air-fuel ratio is switched from rich to lean
Whether the value of the down timer tPR for reading is "0"
(Step S810), the value becomes “0”.
If not, this routine ends. Value "0"
When switching from lean to rich
Whether the value of the down timer tPL has become "0"
It is determined (step S820), and the value must be “0”.
If this is the case, this routine ends. Value must be "0"
If the flag Fpert has the value "0"
(Step S830). The flag Fpert has the value “0”
Sometimes the period tpertR is set in the down timer tPR.
(Step S840) The value “1 + Kper” is added to the coefficient Kp.
"t" is set and vibrated toward the rich side (step S85)
0). This routine sets the flag Fpert to the value "1"
Is ended (step S860). In step S830
When the flag Fpert has the value “1”, the period tpert
L is set in the down counter tPL (step S87)
0), set the value “1-Kpert” to the coefficient Kp and set the coefficient
(Step S880). Flag Fpert value
Reset to "0" and end this routine (step
S890). Therefore, by executing this routine, the coefficient
Kp is an amplitude Kpert and a period tpertR centered on the value “1.0”.
The waveform oscillates at + tpertL. Also, the oxygen storage of the catalyst
The change amount (dO2) of the product amount is when the air-fuel ratio is on the rich side.
Is bigger than when it's lean, so rich
The change in the amount of oxygen stored during
Therefore, tpertR <tpertL is set. In addition,
The amplitude and cycle of the turbation are the oxygen utilization rates described later.
(O2USER). FIG. 22 shows a state in which the space velocity SV is constant.
Gives the maximum purification rate of the catalyst when the catalyst temperature TCAT is changed
Amplitude (ΔA / F) and frequency of perturbation
(Hz). FIG. 23 shows the catalyst temperature TCAT.
When the space velocity SV is changed while keeping the constant
The amplitude of the perturbation that gives the maximum purification rate (ΔA /
F) and the locus of frequency (Hz). FIG. 22 and
In FIG. 23, each area surrounded by “○” indicates the catalyst temperature.
Point of maximum purification rate according to degree TCAT and space velocity SV
The area of the object is shown. Maximum purification in both Fig.22 and Fig.23
The trajectory of the perturbation amplitude and frequency that gives the
Amplitude for a change in medium temperature TCAT or space velocity SV,
It can be seen that it changes substantially in a hyperbolic manner on the frequency plane. Ma
The amplitude and frequency points that give the maximum purification rate
Being on a straight line passing through the origin on the width and frequency planes
Understand. The amplitude and frequency points giving the maximum purification rate
Exists on a straight line passing through the origin on the amplitude and frequency planes.
This can be explained below. As described with reference to FIG.
The applicable oxygen utilization rate O2USER means that O2STR is the maximum oxygen storage
When the time fluctuates shortly between O2MAX and the minimum value (zero)
Maximum when Therefore, as shown in FIG.
In order to maximize, on the rich side of perturbation
Reduction of oxygen storage O2STR and leakage of perturbation
The amount of increase in the oxygen storage amount O2STR on the
It must have a large oxygen reserve, and by doing so,
O2STR from the maximum value to zero
It is released, and the oxygen storage amount O2STR is zero on the lean side.
It accumulates from b to the maximum value. By the way, on the rich side of perturbation,
The amount of decrease in oxygen storage amount O2STR is the CO concentration on the rich side
Is the amplitude of the perturbation and the space is the amount of exhaust gas
The amount of released O2 molecules per unit time, which is the product of the speed, and
Of the perturbation, which is the duration of the rich state of
Is determined by the product of Similarly, on the lean side of perturbation
The amount of increase in the oxygen storage amount O2STR depends on the O2 concentration on the lean side.
Space velocity which is the amplitude of a certain perturbation and the amount of exhaust gas
O2 molecule accumulation per unit time, which is the product of degrees,
The period of the perturbation, which is the duration of the lean state
Determined by the product. Therefore, it is possible to satisfy the maximum purification rate
The slope of the amplitude and frequency points is the maximum oxygen of the catalyst.
The amplitude and frequency are determined by the accumulated amount and space velocity.
Exists on a straight line passing through points,
The slope of the line becomes smaller and the maximum oxygen accumulation (catalyst temperature
The greater the degree, the greater the slope. The above description needs to give the maximum purification rate of the catalyst.
One of the conditions
The maximum purification rate is obtained at a constant amplitude and period. FIG. 21 shows the frequency and amplitude of the perturbation.
Explains the change in catalyst purification rate when the value of catalyst is changed linearly
FIG. FIG. 21A shows the maximum purification rate point.
This is a perturbation waveform having an amplitude and a frequency. FIG. 21B shows the space velocity and the par.
The area of the turbation (amplitude x period) is shown in FIG.
When the amplitude is doubled and the period is halved in the same condition
It is. In this case, the catalyst can be treated per unit time.
Exhaust gas that exceeds the O2 molecular weight
Purification rate is reduced beyond the limit of deposition and release. FIG. 21 (c) shows the space velocity and the
Area (amplitude × period) is the same as that in FIG.
When the amplitude is halved and the period is doubled,
It is. In this case, the catalyst is rich in exhaust gas or
Exhaust gas flows for a longer time than in FIG.
Self-poisoning where HC and other components adhere to the catalyst
As a result, the purification rate also decreases. [Frequency / amplitude change speed setting process (process
9)] First, the amplitude Kpert and the frequencies fpertR, fper
An outline of how to change tL linearly is explained.
You. FIG. 20 shows the amplitude Kpert, the frequency fpertR, fp
FIG. 9 is a flowchart showing a routine for changing ertL;
The amplitude and frequency of the turbation are plotted on the amplitude and frequency planes.
The maximum purification rate while changing it on a straight line passing through the origin.
A method for converging to a point is shown (corresponding to process 8).
First, the absolute pressure PBA in the intake pipe, the engine speed NE, and the vehicle speed
Operation area where V and others stabilize and execute perturbation
Is determined (step S910). The luck
When it is not in the switching region, the amplitude Kpert and the frequency f at that time are
Set and store pertR and fpertL as learning values (step
Step S1030), this routine ends. Pertabesi
When the engine is in the operation area where the
Air-fuel ratio feedback control (SO2F /
It is determined whether or not B) is being executed (step S9).
20). Air-fuel ratio feedback control must be performed
In this case, the above-described step S1030 is executed to execute this routine.
End The air-fuel ratio feedback control is
The same operating state without changing the operating state.
It is determined whether or not it is maintained (step S926).
When the rotation state is changed, the amplitude Kpert and the frequency fpert
It is determined whether or not R and fpertL have already been learned (S
Step S927). If already learned, the learning value is amplitude
Kpert, frequency fpertR, and fpertL are set (step
(Step S1030) This routine ends. Step S9
If it is determined in step 27 that it has not been learned yet,
No space velocity SV / catalyst temperature TCAT map to SV, TC
Amplitude Kpert and frequency fpertR, fpertL according to AT value
Search for the initial value of the amplitude and the amplitude according to the space velocity SV.
変 化 Kp, frequency change △ fPR, △ fPL
Then (step S928), this routine ends. FIG.
4 (A) shows the relationship between the catalyst temperature TCAT and the space velocity SV.
(B) shows a change amount ΔKp of the amplitude Kpert.
Frequency fpertR for temperature TCAT and space velocity SV,
It is a figure which shows variation | change_quantity (DELTA) fPR, (DELTA) fPL of fpertL. The amount of change ΔKp and the amount of change ΔfPR, ΔfPL
Are respectively the tendency of FIG.
Each three-dimensional map or table having the tendency of (B)
Searched and asked. Here, this routine is executed again, and
The engine operating state has not been changed in step S926.
If not, the process moves to step S930. Subsequently, the variation Δ of the oxygen utilization rate O 2 USER
If the value of O2USER is greater than "0",
Usage rate O2USER is increasing or decreasing
It is determined whether or not it is (Step S930). In step S930, the oxygen utilization rate O2USER
When the values are in the increasing direction, the frequencies fpertR and fpertL
Increases by the amounts of change ΔfPR and ΔfPL, respectively (step S
940, step S950), and change the amplitude Kpert by the amount of change ΔK
It increases by p (step S960). Also step
In S930, the value of the oxygen utilization rate O2USER decreases.
In some cases, the frequencies fpertR and fpertL are
Decrease by ΔfPR and ΔfPL (step S970, step
Step S980), the amplitude Kpert is reduced by the amount of change ΔKp.
(Step S990). Next, the increased and decreased amplitude Kpert and frequency
Whether the numbers fpertR and fpertL have exceeded their respective limit values
Judge whether the limit is exceeded.
(Step S1010). Next, the space velocity (not shown)
SV / catalyst temperature Amplitude from SV / TCAT map to SV / TCAT value
Calculate the learning value of Kpert and the frequency fpertR, fpertL
(Step S1020) and terminates this routine.
You. The change amount (ΔKp) of the amplitude (ΔA / F) and
And the frequency change amount (ΔfPR, ΔfPL)
To include the amplitude and frequency points that give a large purification rate,
The space velocity SV and the maximum oxygen storage amount of the catalyst (here, the catalyst temperature
Given by the map shown in FIG.
You. (Corresponding to process 9) Also, the amplitude and frequency change speed setting means in the process 9 is a spatial
The change speed (ΔKp) and the amplitude of the amplitude according to the speed and the catalyst temperature
Changing either of the wave number change speeds (ΔfPR, ΔfPL)
Or change both of them
Where the maximum purification rate point exists in both methods
It is possible to give the inclination of a desired straight line. Operation given by space velocity and catalyst temperature
When the area changes, the initial value will not be calculated until the learning value is calculated.
Calculated from the space velocity and catalyst temperature (not shown)
Amplitude and frequency. This initial value is shown in FIG.
Somewhat higher than the point of maximum purification rate given by 23
And the value of the region where the frequency is small,
Do not use the limit area for catalyst adsorption and release as in (b)
And prevent deterioration of emissions. In the control based on this linear trajectory, the space velocity and
Once the maximum oxygen storage is determined, always give the maximum purification point.
Can be controlled on a linear trajectory where the amplitude and frequency
There is a feature called. Next, the amplitude Kpert, the frequency fpertR, fp
Processing for changing ertL in a hyperbolic manner will be described. FIG.
5 is a hyperbolic curve representing the amplitude Kpert, the frequencies fpertR and fpertL.
FIG. 9 is a flowchart showing a routine to be changed.
The amplitude and frequency of the
Converge to the maximum purification rate point while changing approximately in a hyperbolic manner
The following describes the method of causing this. In FIG. 20, the frequency of perturbation
Give a linear trajectory by changing the number by a predetermined amount
However, in FIG. 25, the perturbation period (reverse frequency)
Number) by a predetermined amount, and change the direction of amplitude and period change.
By giving a direction opposite to that of FIG.
It gives a trace. (Corresponding to process 8). In the flowchart of FIG. 25, first,
Absolute pressure PBA in the intake pipe, engine speed NE, vehicle speed V, etc.
Is stable and in the operating area to perform perturbation
It is determined whether or not it is (step S91). In the operation area
If not, the amplitude Kpert at that time, the period tpertR, t
pertL is set as a learning value and stored (step S103).
This routine ends. Luck performing perturbation
Air-fuel by the downstream O2 sensor 16
The ratio feedback control (SO2F / B) is being executed.
It is determined whether it is (Step S92). Air-fuel ratio fee
When the feedback control is not executed,
By executing S103, the present routine ends. Air-fuel ratio
When performing feedback control, the oxygen utilization
O2USER change ΔO2USER value is greater than “0”
That is, whether the oxygen utilization rate O2USER is increasing
Or not in the decreasing direction (step S9).
3). When the value of oxygen utilization O2USER is increasing
Indicates the periods pertPR, 周期
increase by tPL (step S94, step S95),
The amplitude Kpert is increased by the amount of change ΔKp (step S9)
6). In step S93, the oxygen utilization rate O2USE
When the value of R is decreasing, the periods tpertR, tpert
L is increased by the amount of change ΔtPR and ΔtPL, respectively (step
Step S97, Step S98), change the amplitude Kpert by the amount of change 変 化
It is decreased by Kp (step S99). Amplitude Kpert
Change amount {change amount of Kp and periods tpertR, tpertL}
tPR and ΔtPL depend on the space velocity SV and the catalyst temperature TCAT.
The same value is used. Then, the increased and decreased amplitudes Kpert and
Period tpertR, tpertL exceeds each limit value
Is determined, and if it exceeds, limit processing
Is performed (step S101). Next, space not shown
From the SV / catalyst temperature TCAT map to the SV value and TCAT value
The amplitude Kpert and the periods tpertR and tpertL are learned accordingly.
(Step S102) and ends this routine.
You. Here, the change amount (ΔK) of the amplitude (ΔA / F)
p) and the amount of change in the period (ΔtPR, ΔtPL)
The trace contains the amplitude and frequency points that give the maximum purification rate.
The space velocity SV and the maximum oxygen storage amount of the catalyst (here,
(Medium temperature) determined by the map shown in FIG.
Can be (Corresponding to process 9) Further, the amplitude and frequency changing speed setting means of the processing 9 is a space speed.
Change rate (ΔKp) and cycle of amplitude according to degree and catalyst temperature
Changes one of the change speeds (ΔtPR, ΔtPL)
Or both may be changed,
Either method can give the desired hyperbolic trajectory
You. In the control based on this hyperbolic locus, FIG.
Or the maximum purification point is approximately hyperbolic as shown in FIG.
Due to the linear distribution, changes in the catalyst state, especially
Space velocity (catalyst inflow exhaust gas)
Excellent transient response to changes in volume)
There are features. [Calculation Processing of Fuel Injection Amount Tout (Process 1)
1)] The basic fuel amount Ti of the fuel injection amount Tout is the engine
It is determined from the rotational speed NE and the intake pipe absolute pressure PBA.
The fuel injection amount Tout is corrected to the determined basic fuel amount Ti
Multiply by the coefficient KTOTAL and the coefficient Kp and calculate in the next process 10.
Multiplied by the air-fuel ratio correction coefficient KO2
It is calculated as follows. The correction coefficient KTOTAL is
Temperature Tw correction coefficient, high load enrichment correction coefficient, deceleration
Engine parameters such as fuel economy and acceleration characteristics, including
This is the sum of correction coefficients for improving characteristics. [0095] ## EQU11 ## Tout = Ti × Kp × KTOTAL × KO2 [Calculation processing of air-fuel ratio correction coefficient KO2 (processing 10)] FIG.
7 and FIG. 28 show the output voltage FV of the upstream O2 sensor 16.
The air-fuel ratio for calculating the air-fuel ratio correction coefficient KO2 according to O2
It is a flowchart of a correction coefficient KO2 calculation routine. In step S1610, the first and second
Initializes the lean rich flags FAF1 and FAF2.
U. The first lean rich flag FAF1 is set as shown in FIG.
As shown in (a) and (b), the output voltage of the upstream O2 sensor
FVO2 is higher than reference voltage FVREF (for example, 0.45V).
This flag is set to the value 1 when the rich state is higher.
30. The second lean rich flag FAF2 is
As shown in (d), the first lean rich flag FAF1
From the point at which is inverted (changed from 0 → 1 or 1 → 0)
A flag that is set to the same value as the flag FAF1 with a delay of a fixed time.
It is a lag. Initialization of these flags FAF1 and FAF2
The conversion is specifically executed by the program shown in FIG.
You. First, whether the feedback control has just started or not, that is,
Execute open loop control until last time,
It is determined whether or not the feedback control is to be started (step S
1910) If it is not the start time, there is no need to initialize
Therefore, immediately terminate this program. At the start, the output of the upstream O2 sensor
It is determined whether the voltage FVO2 is lower than the reference voltage FVREF.
Separate (step S1920). FVO2 <FVREF
Holds, the first and second lean rich flags
While setting FAF1 and FAF2 to the value 0 (step S
1930), when FVO2 ≧ FVREF holds
Both are set to the value 1 (step S1940). Returning to FIG. 27, up to step S1620
Initialize the KO2 value. That is, open loop control
Immediately after shifting to feedback control from
When the throttle valve is suddenly opened during the feedback control
Sets the learning value KREF as the initial value of the KO2 value.
You. In other cases, nothing is performed. In the following step S1630, this time KO2
Determines if the value has been initialized and returns
Immediately proceeds to step S1790, while not being initialized.
If not, the process proceeds to step S1640. At the start of feedback control, step S
Since the answer to 1630 is affirmative (YES), step S
In 1790-S1840, the lean rich flag FA
P-term generation delay counter according to the values of F1 and FAF2
Initial setting of CDLY1 and integration control of KO2 value (I term
Control). The counter CDLY1 is shown in FIG.
(C) As shown in (d), the first lean rich flag
The second lean rich flag FA from the inversion point of FAF1
Delay time before inverting F2, ie, O2 sensor output
Executes proportional control (P-term control) from the point of inversion of FVO2
It measures the time it takes to complete. In step S1790, the second lean lid
Judge whether the flag FAF2 is 0 or not.
In step S1800 (FIG. 28), the first
Is determined whether or not the lean rich flag FAF1 is 0
On the other hand, when FAF2 = 1, step S1830 (FIG.
28), the first lean rich flag FAF1 is set to the value
It is determined whether it is 1 or not. At the start of feedback control, F
If VO2 <FVREF, FAF1 = FAF2 = 0
Since there is (see FIG. 29), steps S1790, S18
00 to step S1810, where the counter CDL
A predetermined negative value TDR is set in Y1. Also, FVO2 ≧
If FVREF, FAF1 = FAF2 = 1
Then, after steps S1790 and S1830, step S
1840, and the counter CDLY1 has a positive predetermined value TD.
L is set. Flags FAF1 and FAF2 are both
If the value is 0 or both are other than 1, the counter CDLY1
Is not set, and if FAF2 = 0, the KO2 value
(Step S1820), while adding a predetermined value I to
If AF2 = 1, the predetermined value I is subtracted from the KO2 value (the
Step S1850), and the process proceeds to Step S1860. Ma
Although TDR and TDL are fixed values in the first embodiment,
In a second embodiment to be described later, the oxygen storage amount O2STR
Be changed. The answer in step S1630 in FIG. 27 is negative.
(NO), that is, when the KO2 value has not been initialized this time
Goes to step S1640, where the upstream O2 sensor output
It is determined whether the voltage FVO2 is lower than the reference voltage FVREF.
Separate. As a result, if FVO2 <FVREF holds,
In step S1650, the first lean
Set the zero flag FAF1 to the value 0 and generate the P term
Decrement the delay counter CDLY1 by 1
(See FIG. 30 (c), T4, T10). Then cow
The count value of the counter CDLY1 is smaller than a predetermined negative value TDR.
It is determined whether or not the CDLY is present (step S1660).
When 1 <TDR holds, CDLY1 = TDR is set.
(Step S1670), CDLY1 ≧ TDR
When the condition is satisfied, the process immediately proceeds to step S1710. If the answer to step S1640 is negative (NO),
That is, when FVO2 ≧ FVREF holds, the first
Set the lean rich flag FAF1 to the value 1
, The counter CDLY1 is incremented by one.
(See FIG. 30 (c), T2, T6, T8). Then cow
The count value of the counter CDLY1 is larger than a predetermined positive value TDL.
It is determined whether or not it is acceptable (step S1690), and CDLY
When 1> TDL holds, CDLY1 = TDL is set.
(Step S1700), CDLY1 ≦ TDL
When the condition is satisfied, the process immediately proceeds to step S1710. Here, steps S1630, S1670,
S1690 and S1700 are the counters of the counter CDLY1.
Event value is smaller than negative predetermined value TDR or positive predetermined value
It is provided so that it is not larger than TDL
You. In step S1710, the counter CDL
It is determined whether or not the sign (positive or negative) of the count value of Y1 has been inverted.
Separately, when the reversal is not performed, the above steps S1790 to S1790 to S
When the I-term control of 1850 is executed, while it is reversed
Executes P term control in steps S1720 to S1780
I do. In step S1720, the first lean
It is determined whether or not the switch flag FAF1 has a value of 0.
When F1 = 0, the process proceeds to step S1730 in FIG.
If the value of the second lean rich flag FAF2 is 0,
In both cases, the count value of the counter CDLY1 is set to a negative predetermined value.
TDR (step S1740), and further air-fuel ratio correction
The coefficient KO2 is calculated by Expression 12 (Step S17)
50) (see FIG. 30, time t4, t10). [0108] KO2 = KO2 + (PR1 + PR2) Here, PR1 is the downstream side obtained in FIG.
First rich correction proportional term (P term) according to O2 sensor
It is. Further, PR2 is obtained in FIG. 36 described later.
A second rich correction proportional term (P term) corresponding to O2STR
However, in the first embodiment, PR2 = 0. If the answer to step S1720 is negative (NO),
That is, when FAF1 = 1, the second lean rich
The value of the flag FAF2 is set to 1 and the counter CDLY is set.
The count value of 1 is set to a positive predetermined value TDL (step S1).
760, S1770).
3 (step S1780) (FIG. 30, time
See times t2 and t8). [0110] KO2 = KO2- (PL1 + PL2) Here, PL1 is obtained in FIG.
This is the first lean correction proportional term (P term). Ma
PL2 is obtained in the same manner as PR2 in FIG.
The second lean correction proportional term (P term) is
In the embodiment, PL2 = 0. Subsequent step S1860
Now, check the limit of KO2 value, then KO2
Calculation of the learning value KREF of the value (step S1870);
KREF value limit check (step S1880)
To end this program. According to the program shown in FIGS. 27 and 28,
For example, as shown in FIG. 30, the upstream O2 sensor output voltage F
From the inversion point of VO2 (time t1, t3, t7, t9)
After a predetermined time (T2, T4, T8, T10), the P term
Control is executed (time t2, t4, t8, t10), and the
KO2 during the period of the lean rich flag FAF2 = 0
The I-term control in the increasing direction of the value is executed (T1, T2, T5
~ T8), KO2 value decreasing direction during FAF2 = 1
(T3, T4, T9, T1)
0). In addition, the sensor output FVO2 is between time t5 and t7.
Although it fluctuates in a short cycle, it corresponds to a predetermined negative value TDR.
Since the fluctuation period is shorter than the delay time of the P-term control, the second
The lean rich flag FAF2 is not inverted, and the P-term control is not
Not done. Next, according to the output of the downstream O2 sensor 16,
The air-fuel ratio feedback control will be described. FIG.
Is the air-fuel ratio feedback based on the output of the downstream O2 sensor 16.
6 is a flowchart illustrating a lock control routine. First,
Air-fuel ratio feedback based on the output of the downstream O2 sensor 16
To determine whether the condition of the
Step S1310). Also, when this routine was executed last time,
Air-fuel ratio feed by the output of the downstream O2 sensor 16
Determines whether the conditions for back control have been satisfied
(Step S1320). Step S1310 and the
Air-fuel ratio fee in any of Step S1320
When the feedback control condition is satisfied, the control shown in FIG.
The output table of the downstream O2 sensor 16 is searched by searching the
Deviation from lean stoichiometric state according to VO2
The quantity SDλ0 is determined (step S1330). So search
Based on the deviation amount SDλ0 obtained by
Example: Calculate SDλ by performing integral operation (step S13)
40). [0113] [Equation 14] SDλSUM = SDλSUM + KI × SDλ0 SDλ = SDλSUM + Kp × SDλ0 Check if the calculated SDλ exceeds the limit
Discriminate, and if exceeded, limit
Check processing (step S1350), learning
The value SDλREF is calculated by Expression 15 (Step S
1360). [0114] ## EQU15 ## SDλREF = α5 × SDλ + (1−α5)
× SDλREF Here, α5 is an averaging coefficient. Subsequently, the table shown in FIG.
And the first P-term gain PR1, PL1 corresponding to SDλ
Is obtained (step S1370). Step S1
In both 310 and S1320, the air-fuel ratio
When the feedback control condition is not satisfied, the learning value S
DλREF is set to SDλ (step S1380)
Then, the table is searched to find the first P term PR1, PL1
Ask for. The first P terms PR1 and PL1 are the aforementioned air-fuel ratio supplements.
Air-fuel ratio correction in the processing of the routine for calculating the positive coefficient KO2
Used for calculating the coefficient KO2. By this, it is calculated
Air-fuel ratio correction coefficient KO2 is reflected in fuel injection time Tout
Is done. Thus, the oxygen utilization rate O2USER is used.
Linear or hyperbolic in A / F control
Engine performance by performing perturbation control
Maximum purification rate is ensured according to the running state and catalyst activation state
And significantly improve exhaust emission characteristics.
Responsive to changes in the operating state of the engine
Conversion rate can be increased. [Modification of the First Embodiment]
In the air-fuel ratio controller, the frequency of perturbation fpert
R, fpertL and amplitude Kpert are positive for oxygen utilization O2USER.
Give maximum purification rate by changing according to negative control
The space velocity SV and the catalyst
Frequency fpert corresponding to maximum purification rate according to temperature TCAT
R, fpertL and amplitude Kpert are obtained by experiments, etc.
May be determined directly based on the map. FIG. 34 shows the frequency determined using the map.
Forced vibration processing by fpertR, fpertL and amplitude Kpert
It is a flowchart which shows a routine. This routine is before
It corresponds to the forced vibration processing routine of the first embodiment.
(FIG. 18), Step S835 and Step S865
At the f (TCAT, SV) map directly
The space velocity SV indicating the operating state of the
Frequency fpertR, fpertL and amplitude according to TCAT shown
Search for and determine Kpert. As described above, in the modification of the first embodiment,
According to the air-fuel ratio control device, the space velocity SV and the catalyst temperature
The maximum purification rate according to the degree of TCAT is immediately obtained, further responsiveness
High control can be performed. [Overall Control Processing of the Second Embodiment]
An air-fuel ratio control device according to a second embodiment will be described. FIG.
Is an outline of the overall control processing in the air-fuel ratio device of this embodiment
FIG. Internal combustion engine and air-fuel ratio control device
The overall configuration of the device is the same as in the first embodiment. Also,
The fuel control device has the same catalyst temperature TCAT as in the first embodiment.
(Process 1) and a process for estimating catalyst deterioration.
(Process 2) and the maximum oxygen storage amount of the catalytic converter 14
The process of estimating O2MAX (process 3) and the maximum oxygen storage amount O
Processing for correcting 2MAX (processing 4) and catalytic converter 14
Estimating the air-fuel ratio A / F on the upstream side of the process (process 5);
Oxygen storage amount O2STR stored in catalytic converter 14
(Processing 6) and the acid of the catalytic converter 14
Processing for calculating the elemental utilization rate O2USER (processing 7)
F / B parameter of air-fuel ratio correction coefficient KO2 according to dose O2USE
Adjusting meters (PR, PL, TDR, TDL)
The air-fuel ratio A / F so as to improve the catalyst purification rate by
Control processing (processing 8) and FB parameters (PR, P
L, TDR, TDL) according to the operating state
(Process 9) and a process of calculating the air-fuel ratio correction coefficient KO2
(Process 10) and the injection fuel amount Tou based on Expression 16
The processing for calculating t (processing 11) is performed. [0121] (Equation 16) Tout = Ti × KTOTAL × KO2 In the first embodiment, the period and amplitude of the perturbation are changed.
Air-fuel to maximize oxygen utilization O2USER
The ratio A / F control was performed (process 8 in FIG. 2).
In the embodiment, the downstream O2 cell which is the air-fuel ratio feedback constant is used.
From the time when the sensor output is inverted, the air-fuel ratio correction coefficient KO2
Delay time TDR, TDL before executing proportional control
And skip to skip the air-fuel ratio correction coefficient KO2
By changing the amount (P term gain PR, PL)
Empty pseudo perturbation to maximize utilization O2USER
Perform fuel ratio control. Next, the air-fuel ratio control routine is described.
Will be described. FIG. 36 shows the oxygen utilization rate O2USER of the second embodiment.
Showing an air-fuel ratio control routine (process 8) using
It is a chart. Is this routine repeated by timer processing?
It is executed. First, the absolute pressure PBA in the intake pipe, the engine
The rotational speed NE, vehicle speed V, throttle valve opening θTH, etc.
Sky where the PBA value and θTH value are stable within the fixed range
Determines whether the fuel ratio feedback control is in the execution area.
Separate (step S1110). Downstream O2 sensor 16
Whether the air-fuel ratio feedback control is
Separately (step S1120), the air-fuel ratio feedback system
The engine operating state is not changed
It is determined whether the vehicle is in the same operation state (step S1).
123), when the operating state is changed, the P-term gain P
R2, PL2 and rich lean inversion delay time TD
It is determined whether or not R and TDL have already been learned.
Step S1124). If already learned, set the learning value to P
R2, PL2, TDR, and TDL (Step S
1210) This routine ends. Step S1124
If it is determined that learning has not yet been performed,
The SV / TCAT map makes it possible to use SV / TCAT
Switch-side and lean-side second P-term gains PR2, PL
2 and rich lean inversion delay time TDL, TDR
And the change DP of the P-term gain
Changes in R, DPL and rich lean inversion delay time
DTDR and DTDL also have a space velocity SV and a catalyst temperature T
Set according to CAT (step S1125)
End Change in rich lean inversion delay time
DTDR and DTDL are used for pseudo-perturbation described later.
The frequency changes on the linear locus shown in FIG. 22 of the first embodiment.
Is set to a value that This routine is executed again to execute step S11.
When it is determined at 23 that the driving state has not been changed,
Oxygen utilization rate O2USER is increasing or decreasing
It is determined whether it is in the right direction (step S1130). How to increase
The second P-term region on the rich side and the lean side.
The values of PR2 and PL2 are set to the previous values and the predetermined values DPR and DPL are
In addition, it is increased (step S1140), and the rich /
The inversion delay time TDR, TDL from the previous value to the specified value
DTDR and DTDL are subtracted and reduced (step S
1150). Rich / lean second P-term gain P
R2, PL2 increase and rich / lean inversion delay
The decrease in the time TDR and TDL is determined by the
Increase the amplitude Kpert in the processing
This is equivalent to shortening pertR and fpertL. On the other hand, acid
When the element utilization rate O is decreasing, the rich side and the
The P-term gains PR2 and PL2 on the input side are set to DPR,
DPL is subtracted and reduced (step S1160).
Switch / lean inversion delay time TDR, TDL to previous value
DTDR and DTDL are added to and increased (step S
1170). Such P-term gains PR2, PL2 and
Switch / lean inversion delay time TDR, TDL change
Thus, the area (△ A / F × T) is reduced in the same manner as in the first embodiment.
It is possible to perform pseudo-perturbation control with a constant
Wear. Subsequently, the second P-term gain PR2, PL
2 and delay time TDR, TDL exceed limit value
The limit, and if so,
Performed limit check processing to set the
After step S1180), the second P-term gains PR2, PL2 and
SV / T not shown and delay time TDR, TDL
Learning is performed using the CAT map (step S1190). Further, Step S1110 and Step
Execution of air-fuel ratio feedback control in S1120
In the area or by the downstream O2 sensor 16
When the air-fuel ratio feedback control is not being executed, the second
P-term gain PR2, PL2 and delay time TDR,
Set TDL to the learning value calculated up to the previous time
(Step S1210). The second P terms PR2, PL2 and the delay
Based on the times TDR and TDL, the air-fuel ratio correction
The number KO2 is calculated. The air-fuel ratio correction calculated in this way
The value of the coefficient KO2 is based on the processing 11 according to the equation (16).
The fuel is multiplied by the fuel amount Ti and the correction coefficient KTOTAL.
The injection amount Tout is obtained. Calculation of air-fuel ratio correction coefficient KO2
Is the same as in the first embodiment. Further, pseudo perturbation is performed linearly.
Instead, the curve is pseudo-hyperbolically similar to the first embodiment.
Perturbation can be performed. Figure 37 is a hyperbolic
Air-fuel ratio control when performing pseudo perturbation linearly
It is a flowchart which shows a routine. Step S11
23 and step S1125 are deleted, and step S1
Direct except for changing 150 and step S1170
This is the same as the case where perturbation control is performed. You
That is, when air-fuel ratio feedback control is being performed,
Elemental usage rate O2USER is increasing or decreasing
Is determined (step S1130). Direction of increase
The second P-term gay on the rich and lean sides
Add the specified values DPR and DPL to the previous values of PR2 and PL2.
(Step S1140), the rich / lean counter
The rotation delay time TDR, TDL is set to the previous value by a predetermined value DTD.
R and DTDL are added and increased (step S115)
0). Rich / lean second P-term gain PR2,
PL2 increase and rich / lean inversion delay time T
The increase in DR and TDL is based on the
Increase the amplitude Kpert in the processing
This is equivalent to lengthening R and fpertL. Meanwhile, oxygen utilization
When the rate O2USER is decreasing, rich and
The P-term gains PR2 and PL2 on the input side are set to DPR,
DPL is subtracted and reduced (step S1160).
Switch / lean inversion delay time TDR, TDL to previous value
DTDR and DTDL are subtracted from the values to reduce
Step S1170). Variation of rich lean inversion delay time
DTDR and DTDL are the frequencies of pseudo perturbation.
The number is an integer on the hyperbolic locus shown in FIG. 23 of the first embodiment.
It is set to a value that changes with the value. Then, the second
P-term gain PR2, PL2 and delay time TDR,
Determine whether TDL exceeds the limit value,
The limit check to set the limit value.
After performing the lock processing (step S1180), the second P term
Gain PR2, PL2 and delay time TDR, TD
L is learned from an SV / TCAT map (not shown)
(Step S1190). Such P term gains PR2, P
L2 and rich / lean inversion delay time TDR, T
By changing the DL, a hyperbolic pattern similar to that of the first embodiment is obtained.
It is possible to perform the activation control. As described above, the air-fuel ratio control of the second embodiment
According to the control device, the exhaust emission is similar to that of the first embodiment.
The performance characteristics can be significantly improved. And usually
Pseudo perturbation in the air-fuel ratio control process
Therefore, the forced vibration processing routine of the first embodiment is separately set.
You don't have to. [Modification of the Second Embodiment] The modification of the first embodiment
As in the modification, the space velocity SV and the
Term gain PR of the maximum purification rate according to the catalyst temperature TCAT
2, PL2 and rich / lean inversion delay time TD
When R and TDL are determined in advance by experiments, etc.
Maps these values and calculates the space velocity SV and
P-term gain PR2, PL directly according to catalyst temperature TCAT
2 and rich / lean inversion delay time TDR, TD
L may be determined. FIGS. 38 and 39 are determined using maps.
P-term gain PR2, PL2 and rich / lean
Air-fuel ratio correction coefficient by inversion delay time TDR, TDL
It is a flowchart which shows the calculation routine of KO2. Figure
This routine shown in FIG. 38 and FIG.
This corresponds to FIGS. 27 and 28. Step S1665 and step S16
At 95, the rich / lean inversion delay time TD
Determine R and TDL directly from f (TCAT, SV) map
Steps S1745 and S1775
And P-term gains PR and PL are mapped to f (TCAT, SV) map
Changes in the operating state of the engine
Control of the maximum purification rate with better responsiveness
You. [0132] The exhaust of the internal combustion engine according to claim 1 of the present invention.
According to the system temperature estimation device, the internal combustion engine including at least the load
Exhaust system by steady-state temperature calculation means based on the operating state of
Of the internal combustion engine including at least the load
Exhaust system temperature by following speed calculation means based on operating condition
The following speed for the steady temperature is calculated, and the steady temperature is calculated.
The exhaust system temperature based on the temperature and the following speed
In an exhaust system temperature estimation device for an internal combustion engine,The steady temperature
Is corrected by the air-fuel ratio of the internal combustion engine,By intake air temperature detection means
The internal temperature of the internal combustion engine is detected by the
And based on the detected intake air temperature and the detected vehicle speed.
Then, the steady-state temperature and/ OrFollow
Since the speed is corrected, the exhaust system temperature is estimated in consideration of the running wind.
Improved accuracyThe fuel supplied to the internal combustion engine
By taking into account the so-called fuel cooling effect
The accuracy of exhaust system temperature estimationit can. [0133]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of an internal combustion engine equipped with an air-fuel ratio control device according to one embodiment of the present invention. FIG. 2 is a block diagram schematically showing an overall control process in the air-fuel ratio control device according to the first embodiment. FIG. 3 is a flowchart illustrating a routine for estimating a catalyst temperature TCAT. FIG. 4 is a graph showing a table for determining values of coefficients α1 and α2 according to an integral value TOUTSUM. FIG. 5 shows a correction coefficient KTA according to an intake air temperature TA and a vehicle speed V.
9 is a graph showing a table for determining TCAT. FIG. 6 shows a correction coefficient Kα according to a vehicle speed V and an intake air temperature TA.
6 is a graph showing a table for determining the value of. FIG. 7 is a graph showing a table for determining a correction coefficient KA / F according to an air-fuel ratio A / F. FIG. 8 shows the maximum oxygen storage amount O2MAX according to the catalyst temperature TCAT.
6 is a graph showing a table for determining a value. FIG. 9 is a flowchart showing a routine for correcting the maximum oxygen storage amount O2MAX. FIG. 10 is a flowchart illustrating an air-fuel ratio estimation routine. FIG. 11 is a schematic diagram showing a catalytic action of the catalytic converter 14. FIG. 12 is a graph showing values of deterioration coefficients k1R and k2R and temperature coefficients k1CAT and k2CAT relating to a reaction coefficient. FIG. 13 is a characteristic diagram showing a relationship between an air-fuel ratio A / F of exhaust gas input to a catalytic converter and a CO concentration and an O2 concentration. FIG. 14 is a flowchart showing a routine for calculating the oxygen storage amount O2STR in the catalytic converter 14. FIG. 15 is a graph showing values of an upper limit O2STRH and a lower limit O2STRL with respect to a catalyst temperature TCAT. FIG. 16 is a waveform diagram showing a temporal change of the oxygen storage amount O2STR. FIG. 17 is a flowchart showing a calculation routine of an oxygen utilization rate O2USER. FIG. 18 is a flowchart showing a process of forced vibration (perturbation) of the air-fuel ratio. FIG. 19 is a timing chart showing the waveform of the perturbation of FIG. 18; FIG. 20 is a flowchart showing a routine for changing an amplitude Kpert, frequencies fpertR, and fpertL. FIG. 21 is an explanatory diagram showing changes in the catalyst purification rate when the values of the frequency and amplitude of the perturbation are changed linearly. FIG. 22 is a trajectory of a perturbation amplitude (ΔA / F) and a frequency (Hz) that give a maximum catalyst purification rate when the catalyst temperature TCAT is changed with the space velocity SV kept constant. FIG. 23 is a trajectory of a perturbation amplitude (ΔA / F) and a frequency (Hz) that give a maximum catalyst purification rate when the space velocity SV is changed with the catalyst temperature TCAT kept constant. FIG. 24 is an explanatory diagram showing a table for determining a variation ΔKp of amplitude Kpert and variations ΔfPR and ΔfPL of frequencies fpertR and fpertL according to space velocity SV and catalyst temperature TCAT. FIG. 25 is a flowchart showing a routine for changing the amplitude Kpert, the periods tpertR, and tpertL. FIG. 26 is a graph showing amplitude variation ΔKp and period variation ΔtPR, tPL with respect to space velocity SV and catalyst temperature TCAT. FIG. 27 is a flowchart of an air-fuel ratio correction coefficient KO2 calculation routine for calculating an air-fuel ratio correction coefficient KO2 in accordance with the output voltage FVO2 of the upstream O2 sensor 16. FIG. 28 is a flowchart of the air-fuel ratio correction coefficient KO2 calculation routine for calculating the air-fuel ratio correction coefficient KO2 according to the output voltage FVO2 of the upstream O2 sensor 16, following FIG. 27; FIG. 29 is a flowchart showing an initialization routine for FAF1 and FAF2. FIG. 30 is a timing chart showing changes in the air-fuel ratio correction coefficient KO2. FIG. 31 is a flowchart showing an air-fuel ratio feedback control routine by the downstream O2 sensor 16; FIG. 32 shows the displacement amount SDλ and the output SV of the downstream O2 sensor.
It is a table which shows the relationship with O2. FIG. 33 is a table showing a relationship between a deviation amount Dλ and a P-term gain (PR, PL). FIG. 34 shows a frequency fpertR determined using a map,
It is a flowchart which shows the forced vibration processing routine by fpertL and amplitude Kpert. FIG. 35 is a block diagram schematically showing an overall control process in the air-fuel ratio device of the second embodiment. FIG. 36 is a flowchart showing an air-fuel ratio control routine in the case where pseudo perturbation is performed linearly using the oxygen utilization rate O2USER of the second embodiment. FIG. 37 is a flowchart showing an air-fuel ratio control routine in the case where pseudo perturbation is performed in a hyperbolic manner. FIG. 38 shows a P-term gain PR determined using a map.
2, PL2 and rich / lean inversion delay time TD
9 is a flowchart illustrating a routine for calculating an air-fuel ratio correction coefficient KO2 using R and TDL. 39 is an air-fuel ratio correction coefficient KO2 based on P-term gains PR2 and PL2 and rich / lean inversion delay times TDR and TDL determined using a map, following FIG. 38;
6 is a flowchart showing a calculation routine of the first embodiment. [Description of Signs] 1 ... internal combustion engine 5 ... ECU 8 ... intake air temperature sensor 9 ... cooling water temperature sensor 14 ... catalytic converter 15 ... upstream oxygen concentration sensor 16 ... downstream oxygen concentration sensor 32 ... vehicle speed sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-224640 (JP, A) JP-A-4-171231 (JP, A) JP-A-62-203965 (JP, A) JP-A-1- 219340 (JP, A) JP-A-63-97848 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 45/00

Claims (1)

(57) Claims: 1. A steady-state temperature calculating means for calculating a steady-state temperature of an exhaust system of an internal combustion engine based on an operating state of the internal combustion engine including at least a load; A following speed calculating means for calculating a following speed of the exhaust system temperature with respect to the steady temperature based on an operation state of the internal combustion engine; an exhaust system temperature of the internal combustion engine estimating the exhaust system temperature based on the steady temperature and the following speed In the estimating device, a correction coefficient for correcting the steady-state temperature is calculated based on an air-fuel ratio of the internal combustion engine.
Setting means for setting a smaller value as the fuel ratio becomes richer
When, for correcting the intake air temperature detecting means for detecting a vehicle speed detecting means for detecting a vehicle speed, the steady state temperature and / or follow-up rate based on the intake air temperature and the vehicle speed issued該検the intake air temperature of the internal combustion engine An exhaust system temperature estimating device for an internal combustion engine, comprising: a correcting unit.