JP3186186B2 - Air-fuel ratio control 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 an air-fuel ratio control device for an internal combustion engine, and more particularly, to a first feedback control value provided by a first exhaust sensor provided upstream of a catalyst body in accordance with a state of deterioration of the catalyst body. Further, the present invention relates to an air-fuel ratio control device for an internal combustion engine which can stably respond to first feedback control by a first exhaust sensor without excessively responding to second feedback control by a second exhaust sensor provided downstream of the catalytic converter.

[0002]

2. Description of the Related Art Some internal combustion engines mounted on vehicles are provided with an air-fuel ratio control device. The air-fuel ratio control device is provided with an oxygen sensor as an exhaust sensor for detecting, for example, an oxygen concentration as an exhaust component value in an exhaust passage, and the air-fuel ratio becomes a target value by a feedback control value calculated from a detection signal output from the oxygen sensor. By performing such feedback control, the exhaust gas purifying efficiency by the catalyst body is improved, and the exhausted exhaust harmful component value is reduced.

An example of such an air-fuel ratio control device for an internal combustion engine is disclosed in Japanese Patent Application Laid-Open No. 61-234241. The air-fuel ratio control device disclosed in this publication provides a first oxygen sensor in an exhaust passage on an upstream side of a catalyst body provided in an exhaust passage of an internal combustion engine and a second oxygen sensor in an exhaust passage on a downstream side of the catalyst body. And correcting the skip amount of the first feedback control value calculated from the first detection signal output from the first oxygen sensor by the second detection signal output from the second oxygen sensor, and responding to the deterioration of the first oxygen sensor. It is intended to prevent the deterioration of the performance.

[0004]

As described above, a first oxygen sensor as a first exhaust sensor is provided in an exhaust passage upstream of a catalyst provided in an exhaust passage of an internal combustion engine, and a first oxygen sensor is provided downstream of the catalyst. In an air-fuel ratio control device provided with a second oxygen sensor as a second exhaust sensor in an exhaust passage,
As shown in FIG. 12, the first feedback control value (OXF) calculated from the first detection signal output from the first oxygen sensor
According to B), the first feedback control is performed so that the air-fuel ratio becomes the target value. Further, as shown in FIG. 13, when the second detection signal output from the second oxygen sensor is inverted between the rich signal and the lean signal, the second feedback control skip values (S _RL , S _LR ) (hereinafter, skip values) respectively. ) by to skip, each of the duration of the rich signal and the lean signal of the second detection signal (T _{R, T L)} of the integral value determination time tk
The second feedback control value (SOXFB) is adjusted by adding or subtracting a predetermined second feedback control integrated value (I _RL ) (hereinafter referred to as an integral value) at each integral value determination time tk.
Is calculated.

[0005] The air-fuel ratio control apparatus uses the second feedback control value (SOXFB) calculated as described above to obtain the value shown in FIG.
As shown in FIG. 4, the first feedback control value (OXF) when the first detection signal is inverted between the rich signal and the lean signal.
In some cases, the second feedback control is performed to correct the air-fuel ratio inversion delay time (D _LR , D _RL ) in B), and the first feedback control by the first oxygen sensor is prevented from deviating from the control center. The air-fuel ratio reversal delay time (D
_LR , D _RL ) is a time for performing a process in which the change is regarded as being delayed by a certain time when the first detection signal changes from a rich signal to a lean signal or when the signal changes from a lean signal to a rich signal.

However, in such an air-fuel ratio control device, as shown in FIGS. 9 to 11, the period (T _FR ) or frequency (hereinafter, referred to as “period”) of the first detection signal of the first oxygen sensor, With respect to “cycle”, the cycle (T _RE ) of the second detection signal of the second oxygen sensor changes depending on the deterioration state of the catalyst. That is, when the catalyst is deteriorated with respect to the period (T _RE) of the second detection signal at the time of non-degraded as shown in FIG. 10, the period of the second detection signal when deterioration as shown in FIG. 11 (T _RE) is It becomes shorter and approaches the period (T _FR ) of the first detection signal of the first oxygen sensor.

[0007] As a result, in both when deterioration non-degraded during the catalyst body catalyst is a new article is used for a long period of time, a second respective duration of the rich signal and the lean signal detection signal (T _R, T _L ) will change.

As described above, the second state depends on the deterioration state of the catalyst body.
Each of the duration of the rich signal and the lean signal detection signal _{(T R,} T _L) When the integrated value determination time tk is constant with respect to changes, the second in a time of degradation and time of non-deterioration of the catalyst There is a problem that the second feedback control value (SOXFB) by the oxygen sensor greatly changes and the air-fuel ratio inversion delay time (D _LR , D _RL ) of the first feedback control value (OXFB) by the first oxygen sensor is shifted. is there.

For this reason, the first feedback control by the first oxygen sensor deviates from the control center, and the first oxygen sensor accurately controls the first air-fuel ratio so that the air-fuel ratio becomes the target value.
There is a disadvantage that the feedback control cannot be performed, the exhaust gas purification efficiency is deteriorated, and the exhaust harmful component value cannot be reduced.

Further, as described above, the first detection signal is changed between the rich signal and the lean signal by the second feedback control value (SOXFB) calculated from the second detection signal output from the second oxygen sensor, as shown in FIG. The first when turned over
When the second feedback control is performed to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) of the feedback control value (OXFB), the first feedback control by the first oxygen sensor is different from the second feedback control by the second oxygen sensor. Have the problem of responding too sensitively.

For this reason, the second feedback control value (S
Since the first feedback control by the first oxygen sensor responds excessively to a large change in OXFB), the first feedback control by the first exhaust sensor cannot be made to respond stably. The first feedback control by the oxygen sensor deviates from the control center, and the first feedback control cannot be accurately performed by the first oxygen sensor so that the air-fuel ratio becomes the target value. There is a disadvantage that cannot be reduced.

More specifically, the second state depends on the state of deterioration of the catalyst body.
Rich signal and the lean signal of each of duration _{(T R,} T _L) of the detection signal when is the integral value determination time tk is constant with respect to changes, as shown in FIG. 15, the catalyst is deteriorated For example, when the duration ta of the rich signal of the second detection signal becomes shorter and the integral value determination time tk becomes longer than the duration ta of the second detection signal (tk ≧ ta), the integration value determination time tk is not changed. Since the second detection signal is not inverted, the integration value (I _RL ) is not adjusted.

As described above, when the integral value determination time tk is longer than the duration time ta (tk ≧ ta), as shown in FIG. 16, the second feedback control value (SOXFB) by the second oxygen sensor becomes , Cannot be changed to either side because no integral value is generated, and the current value is skipped only by the skip value (S _RL , S _LR ) near the current value.

For this reason, as shown in FIG. 17, the air-fuel ratio reversal delay time (D _LR ) of the first feedback control value (OXFB) is changed by the second feedback control value (SOXFB).
D _{when R L)} is the second feedback control to correct the air-fuel ratio inversion delay time of the first feedback control value by the first oxygen sensor _{(OXFB) (D LR,}
D _RL ), the air-fuel ratio by the first feedback control deviates from λ = 1, which is the control center, and the first oxygen sensor performs the first feedback control with high accuracy so that the air-fuel ratio becomes the target value. Therefore, there is a disadvantage that the exhaust gas purification efficiency is deteriorated and the exhaust harmful component value cannot be reduced.

Also, as shown in FIGS. 18 and 19, when the catalyst body is new and not deteriorated, the integration value (I _RL ) frequently occurs due to the long period of the second detection signal, and the integration is performed. And the second feedback control value (SO
XFB) will change greatly. Also, the second feedback control value (SOXF
B) to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) of the first feedback control value (OXFB) according to B).
In order to perform the feedback control, the air-fuel ratio inversion delay time (D _LR ) of the first feedback control value (OXFB)
D _RL ) becomes longer or shorter, and the first feedback control by the first oxygen sensor responds excessively to the second feedback control, and the first feedback control cannot be made to respond stably. Thus, the air-fuel ratio by the first feedback control is λ = 1, which is the control center.
Therefore, the first oxygen sensor cannot accurately perform the first feedback control so that the air-fuel ratio becomes the target value, and the exhaust gas purification efficiency deteriorates, and the exhaust harmful component value cannot be reduced.

[0016]

SUMMARY OF THE INVENTION Accordingly, in order to eliminate the above-mentioned disadvantages, the present invention provides a first exhaust sensor in the exhaust passage upstream of a catalyst provided in an exhaust passage of an internal combustion engine. The second exhaust passage on the downstream side of the medium
An exhaust sensor, and a first output from the first exhaust sensor.
The first feedback control is performed based on the first feedback control value calculated from the detection signal so that the air-fuel ratio becomes the target value, and the duration of the second detection signal output from the second exhaust sensor is determined for each integral value determination time. The first feedback control value calculated by adding or subtracting the integral
In an air-fuel ratio control device for an internal combustion engine that performs a second feedback control to correct an air-fuel ratio inversion delay time of a feedback control value, the second detection signal is set such that the integral value determination time is shorter than the duration of the second detection signal. In accordance with the cycle, control means is provided for controlling the correction so that the integral value determination time becomes shorter as the cycle becomes shorter.

[0017]

According to the structure of the present invention, the control means
In accordance with a cycle of the second detection signal such that the integration value determination time is always shorter than the duration of the second detection signal, control is performed to correct the integration value determination time so as to become shorter as the cycle becomes shorter. The second condition is caused by the deterioration state of the catalyst body.
To changes in each of the duration of the rich signal and the lean signal detection signal _{(T R,} T _L), the deterioration of the catalytic body without the second feedback control value integrated value determination time tk of (SOXFB) to constant The second feedback control value (SOXFB) can be prevented from greatly changing, depending on the state, and the air-fuel ratio inversion delay time (D _LR ) of the first feedback control value (OXFB) by the first exhaust sensor can be prevented.
D _RL ) can be prevented. Therefore, it cannot be changed to either side due to no occurrence of the integral value, and the skip value (S
_RL , _SLR ) can be prevented from skipping. Further, the first feedback control by the first exhaust sensor can be prevented from deviating from the state of λ = 1 which is the control center, and the first feedback control is accurately performed by the first exhaust sensor so that the air-fuel ratio becomes the target value. As a result, the exhaust gas purification efficiency can be improved and the exhaust harmful component value can be reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 8 show an embodiment of an air-fuel ratio control apparatus according to the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an intake passage, and 6 is an exhaust passage. An intake passage 4 of the internal combustion engine 2 includes an air cleaner 8, an air flow meter 10, and a throttle body 1, which are sequentially connected from the upstream side.
2 and the intake manifold 14. An intake throttle valve 16 is provided in the intake passage 4 in the throttle body 12.
It has. The intake passage 4 is provided with a combustion chamber 18 of the internal combustion engine 2.
Is communicated to.

The exhaust passage 6 communicated with the combustion chamber 18 of the internal combustion engine 2 includes an exhaust manifold 20, an upstream exhaust pipe 22, a catalytic converter 24, and a downstream exhaust pipe 26 which are sequentially connected from the upstream side. It is formed. A catalyst body 28 is provided in the exhaust passage 6 in the catalytic converter 24.

The internal combustion engine 2 is provided with a fuel injection valve 30 directed toward the combustion chamber 18. The fuel injection valve 30
The fuel supply passage 34 communicates with the fuel tank 36 via the fuel distribution passage 32. In the fuel tank 36,
A fuel pump 38 is provided. The fuel pumped by the fuel pump 38 is dust-removed by the fuel filter 40, supplied to the fuel distribution passage 32 by the fuel supply passage 34, and distributed to the fuel injection valve 30.

The fuel distribution passage 32 is provided with a fuel pressure adjusting section 42 for adjusting the fuel pressure. The fuel pressure adjusting unit 42 adjusts the fuel pressure to a constant value by the intake pressure introduced from the pressure guiding passage 44 communicating with the intake passage 4,
Excess fuel is returned to the fuel tank 36 through the fuel return passage 46.

The fuel tank 36 is provided in communication with the intake passage 4 of the throttle body 12 through an evaporative fuel passage 48.
A two-way valve 50 and a canister 52 are sequentially provided from the side. A bypass passage 54 that bypasses the intake throttle valve 16 of the throttle body 12 and communicates with the intake passage 4 is provided.
And an idle air amount control valve 56 is provided in the bypass passage 54 to increase or decrease the amount of bypass air to stabilize the idle speed. Reference numeral 58 denotes an air regulator, reference numeral 60 denotes a power steering switch, reference numeral 62 denotes an air amount control valve for power steering, reference numeral 64 denotes a blow-by gas passage, and reference numeral 66 denotes a PCV valve.

The air flow meter 10 and the fuel injection valve 3
The idle air amount control valve 56 and the power steering air amount control valve 62 are connected to a control unit 68 as control means. The control unit 68 includes a crank angle sensor 70,
The distributor 72, the opening degree sensor 74 of the intake throttle valve 16, the knock sensor 76, the water temperature sensor 78, and the vehicle speed sensor 80 are connected to each other. The distributor 72 is connected to the control unit 68 via an ignition coil 82 and an ignition power unit 84.

Further, the internal combustion engine 2 is provided with a first oxygen sensor 86 as a first exhaust sensor for detecting an oxygen concentration as an exhaust component value in the exhaust passage 6 on the upstream side of the catalyst body 28, and a downstream side of the catalyst body 28. A second oxygen sensor 88, which is a second exhaust sensor for detecting an oxygen concentration as an exhaust component value, is provided in the exhaust passage 6 on the side. The first oxygen sensor 86 and the second oxygen sensor 86
The oxygen sensor 88 is provided so as to be connected to the control unit 68.

The control unit 68 controls the first feedback control value (OXFB) calculated from the first detection signal output from the first oxygen sensor 86 so that the air-fuel ratio reaches the target value.
In addition to performing feedback control, the second oxygen sensor 88
Second detection signal duration of the output of _(T R, T _L) predetermined integral value is determined for each integral value determination time tk _{(I RL)}
Feedback control value (SOX
FB), the first feedback control value (OXF)
The second feedback control is performed to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) in B). The air-fuel ratio control apparatus for such an internal combustion engine 2, the control unit 68, the integration value determination time tk duration of the second detection signal _{(T R,} T _L) than shorter so as second detection signal according to the period (T _RE), the integral value determination time tk is controlled to correct so small according to the periodic (T _RE) is shortened.

Further, in such an air-fuel ratio control device for the internal combustion engine 2, the control unit 68 calculates the arithmetic average of the immediately preceding value and the immediately preceding value each time the second feedback control value (SOXFB) is skipped. (SOX
FBAV) and the arithmetic mean number (χ) is calculated from the period (T _FR ) of the first detection signal and the period (T _RE ) of the second detection signal in accordance with the state of deterioration of the catalyst body 28. Calculating the second feedback control learning value (SOXFLAV) of the second oxygen sensor 88 from the arithmetic mean (SOXFBAV) and the arithmetic mean number (χ), and calculating the second feedback control learning value (SOXFLAV).
To correct the air-fuel ratio inversion delay time (D _LR , D _RL ) of the first feedback control value (OXFB) by the second
This is for feedback control.

In FIG. 1, reference numeral 90 denotes a dashpot, reference numeral 92 denotes a thermofuse, reference numeral 94 denotes an alarm relay, reference numeral 96 denotes a warning light, reference numeral 98 denotes a diagnosis switch, reference numeral 100 denotes a TS switch, and reference numeral 102 denotes a diagnosis lamp. , 104 are main switches, reference numeral 10
6 is a battery.

Next, control by the air-fuel ratio control device will be described with reference to FIG.

When the internal combustion engine 2 is started (step 200), the second feedback control execution condition of the second oxygen sensor 88 is determined (step 202). This determination (step 202) is, as shown in FIG. 3, that the first oxygen sensor 86 is under the first feedback control, that the internal combustion engine 2 is not idling, and that the internal combustion engine 2 has finished warming up. That the first oxygen sensor 86 has not failed;
The determination is made based on whether or not all the conditions that the second oxygen sensor 88 has not failed are satisfied.

In the determination (step 202), if any one of the conditions shown in FIG. 3 is not satisfied, the second feedback control of the second oxygen sensor 88 is not performed. In the determination (step 202), if all the conditions shown in FIG. 3 are satisfied, the second feedback control of the second oxygen sensor 88 is performed.

When all the conditions shown in FIG. 3 are satisfied and the second feedback control of the second oxygen sensor 88 is performed,
As shown in FIGS. 9 and 10, the period (T _FR ) of the first detection signal of the first oxygen sensor 86 and the period (T _RE ) of the second detection signal of the second oxygen sensor 88 are measured, and these periods (T _RE ) are measured. T
_FR , _TRE ) to determine the deterioration state of the catalyst body 28 (step 204).

Next, as shown in FIG. 13, the second feedback control value (SOXFB) of the second feedback control is changed every time the second detection signal output from the second oxygen sensor 88 is inverted between the rich signal and the lean signal. The skip values (S _RL , S _LR ) are respectively adjusted (step 206), and skip control is executed. The second feedback control value (SOXFB), respectively of the duration of the rich signal and the lean signal of the second detection signal output from the second oxygen sensor 88 _(T R, T _L) for each integral value determination time tk by The integral value (I _RL ) is adjusted, and integral control is performed.

The second feedback control value (SOXFB) of the second feedback control is as shown in FIG.
The cycle (T _FR , T _FR ) in the determination (step 204)
With changing the integrated value determination time tk by the deteriorated state of the catalytic body 28 by _RE) (the ratio T _RE / _{T FR} cycle shown in FIG. 4), as shown in FIG. 5, the determination (catalyst 28 in step 204) The integrated value (I _RL ) is also changed (step 208) in accordance with the deterioration state (period ratio T _RE / T _FR ) shown in FIG. Since the deterioration state of the catalyst body 28 is related to the cycle of the second detection signal as described later with reference to FIG. 7, the cycle ratio T in FIGS.
The integral value judgment time tk and the integral value by _RE / _{T FR} (I
_RL ).

As shown in FIG. 6, every time the second feedback control value (SOXFB) is skipped, the arithmetic mean (SOXFBAV) of the immediately preceding skip value (A) and the immediately preceding skip value (B) is calculated as SOXFBAV = (A + B /
It is calculated by 2) (step 210).

[0036] From the obtained arithmetic mean (SOXFBAV), air-fuel-ratio reversal delay time of the first feedback control value _{(OXFB) (D LR, D} RL) to correct the second
A feedback control learning value (SOXFLAV) is calculated (step 212). That is, as shown in FIG.
The period of the detection signal (T _FR ) and the period of the second detection signal (T _FR )
_RE ), the arithmetic mean number (χ) is calculated according to the deterioration state of the catalyst body 28 (period ratio T _RE / T _FR shown in FIG. 7). The arithmetic mean number (χ) is changed depending on the deterioration state of the catalyst body 28. From the arithmetic mean (SOXFBAV) and arithmetic mean number (数), a second feedback control learning value (SOXFLAV) is calculated according to Equation 1.

[0037]

(Equation 1)

The second feedback control learning value (SOXF
LAV) calculates the value of the arithmetic mean number (χ) according to FIG.
The value of the arithmetic mean number (χ) obtained is introduced into Equation 1 to obtain the value. In this case, as apparent from FIG. 7, the arithmetic mean number (触媒) becomes smaller as the catalyst body 28 is new and is not deteriorated. This is because when the catalyst body 28 is new, the period (T) of the second detection signal output from the second oxygen sensor 88
_This is because the sampling time becomes too long unless the captured value for calculating the average is reduced because the _RE ) is long.

As shown in FIGS. 8 and 12, the air-fuel ratio inversion delay time (D _LR , D _RL ) of the first feedback control value (OXFB) is corrected by the calculated second feedback control learning value (SOXFLAV). The second feedback control (step 214) is performed as needed.

The above (Step 202) to (Step 2)
14) is repeated (step 216) to control.

As described above, the control unit 68 controls the second feedback control value (SOX) by the second oxygen sensor 88.
For each skip of FB), the arithmetic mean (SOXFBAV) of the immediately preceding skip value (A) and the immediately preceding skip value (B)
The arithmetic mean number (χ) is calculated from the period (T _FR ) of the first detection signal of the first oxygen sensor 86 and the period (T _RE ) of the second detection signal according to the deterioration state of the catalyst body 28. calculate. The second feedback control learning value (SOXFLAV) of the second exhaust sensor 88 is calculated from the arithmetic mean (SOXFBAV) and the arithmetic mean number (χ), and the first feedback control learning value (SOXFLAV) is used to calculate the first feedback control learning value. The second feedback control is performed to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) of the feedback control value (OXFB).

Accordingly, the first feedback control value (OXFB) by the first oxygen sensor 86 can be corrected according to the state of deterioration of the catalyst body 28, and the first feedback control by the first oxygen sensor 86 can be performed by the second feedback control. It is possible to stably respond to the second feedback control by the oxygen sensor 88 without excessively responding.

[0043] That is, with respect to the period of the first detection signal of the first oxygen sensor 86 _{(T FR),} the period of the second detection signal of the second oxygen sensor 88 as shown in FIG. 11 _{(T RE)} is catalyst 2
8, the duration of the rich signal and the lean signal of the second detection signal is different between the non-degraded state where the catalyst body 28 is new and the deteriorated state where the catalyst body 28 has been used for a long period of time. _(T R, _{T L)} so that the changes.

[0044] Thus, each of the duration of the rich signal and the lean signal of the second detection signal by the deteriorated state of the catalytic body 28 _{(T R,} T _L) relative to the changes, the second feedback control value ( SOXFB) integral value determination time tk
Of the second feedback control value (SOXF
B) can be prevented from greatly changing, and the inconvenience of causing a deviation in the air-fuel ratio inversion delay time (D _LR , D _RL ) of the first feedback control value (OXFB) by the first oxygen sensor 86 can be prevented. it can.

For this reason, since the integral value (I _RL ) does not occur, it cannot be changed to either side, and it is possible to prevent the skipping only by the skip value (S _RL , S _LR ) around the current value. Further, the first oxygen sensor 86
Λ = 1 where the first feedback control by
Can be prevented from deviating from the state, the first feedback control can be accurately performed by the first oxygen sensor 86 so that the air-fuel ratio becomes the target value, the exhaust gas purification efficiency can be improved, and the exhaust harmful component value can be reduced. be able to.

Further, as in the prior art, the second oxygen sensor 88
Of the first feedback control value (SOXFB)
In order to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) of the first feedback control value (OXFB) of the detection signal, the second
Without feedback control, the arithmetic mean (SOXFBAV) calculated for each skip of the second feedback control value (SOXFB), the period of the first detection signal (T _FR ), and the period of the second detection signal (T _RE ) The arithmetic mean number (χ) corresponding to the state of deterioration of the catalyst body 28 calculated from
From the second feedback control learning value (S
OXFLAV), the first feedback control value (OX
The second feedback control is performed to correct the air-fuel ratio reversal delay time (D _LR , D _RL ) of FB).

Therefore, the second feedback control value (S
OXFB) does not greatly change, and the first feedback control by the first oxygen sensor 86 can be stably responded to the second feedback control by the second oxygen sensor 88 without being excessively responsive. The first oxygen sensor 86 can prevent the first feedback control from deviating from the control center, and the first oxygen sensor 86 can accurately perform the first feedback control so that the air-fuel ratio becomes a target value, thereby improving the exhaust gas purification efficiency. As a result, the emission harmful component value can be reduced.

In this embodiment, the second feedback control is performed to correct the air-fuel ratio inversion delay time (D _LR , D _RL ) of the first feedback control value (OXFB) by the second feedback control learning value (SOXFLAV). However, the second feedback control learning value (SOXFL
AV) to control the integrated value and the skip value of the first feedback control value (OXFB).

[0049]

As described above, according to the present invention, since the integrated value (I _RL ) does not occur in accordance with the state of deterioration of the catalyst body, it cannot be changed on either side, and the skip value near the current value is not obtained. (S _RL , S _LR ) can be prevented from skipping, the first feedback control value by the first exhaust sensor can be corrected, and the first feedback control by the first exhaust sensor can be corrected by the second exhaust sensor. (2) A stable response can be achieved without excessively responding to the feedback control.

For this reason, the first feedback control can be accurately performed by the first exhaust sensor so that the air-fuel ratio becomes the target value, the exhaust purification efficiency can be improved, and the exhaust harmful component value can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an air-fuel ratio control device for an internal combustion engine showing an embodiment of the present invention.

FIG. 2 is a flowchart of control of the air-fuel ratio control device.

FIG. 3 is a logic circuit diagram of a second feedback control execution condition.

FIG. 4 is a diagram illustrating a relationship between a cycle (T _FR ) of a first detection signal and a cycle (T _RE ) of a second detection signal and an integral value determination time (tk).

FIG. 5 is a diagram showing a relationship between a period (T _FR ) of a first detection signal and a period (T _RE ) of a second detection signal and an integral value (I _RL ).

FIG. 6 is a diagram showing a second feedback value (SOXFB).

FIG. 7 is a diagram showing the relationship between the period (T _FR ) of the first detection signal and the period (T _RE ) of the second detection signal and the arithmetic average number (χ).

FIG. 8 shows a second feedback control learning value (SOXFLA).
FIG. 5 is a diagram showing a relationship between V) and an air-fuel ratio inversion delay time (D _LR , D _RL ) of a first feedback control value (OXFB).

FIG. 9 is a waveform diagram of a first detection signal of the first oxygen sensor.

FIG. 10 is a waveform diagram of a second detection signal of the second oxygen sensor when the catalyst is not deteriorated.

FIG. 11 is a waveform diagram of a second detection signal of the second oxygen sensor when the catalyst is deteriorated.

FIG. 12 is a waveform chart showing a relationship between a first detection signal of a first oxygen sensor and a first feedback control value (OXFB).

FIG. 13 is a waveform diagram showing a relationship between a second detection signal of a second oxygen sensor and a second feedback control value (SOXFB).

FIG. 14 shows a conventional second feedback control value (SOXF
FIG. 6B is a diagram illustrating a relationship between the air-fuel ratio reversal delay time (D _LR , D _RL ) of the first feedback control value (OXFB).

FIG. 15 is a diagram showing a relationship between a first detection signal of a first oxygen sensor and a second detection signal of a second oxygen sensor when a conventional catalyst body deteriorates.

FIG. 16 is a diagram showing a second feedback control value (SOXFB) when a conventional catalyst body deteriorates.

FIG. 17 shows the relationship between the air-fuel ratio when the conventional catalyst body is deteriorated and
FIG. 4 is a diagram illustrating a relationship between a first detection signal of an oxygen sensor and a first feedback control value (OXFB).

FIG. 18 shows a conventional second feedback control value (SOXF
It is a figure which shows B).

FIG. 19 is a diagram illustrating a conventional relationship among a first detection signal, a second detection signal, and a second feedback control value (SOXFB).

[Explanation of symbols]

 2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Air cleaner 12 Throttle body 14 Intake manifold 16 Intake throttle valve 18 Combustion chamber 20 Exhaust manifold 24 Catalyst converter 28 Catalyst 30 Fuel injection valve 68 Control unit 70 Crank angle sensor 74 Openness sensor 76 Knock Sensor 78 Water temperature sensor 80 Vehicle speed sensor 86 First oxygen sensor 88 Second oxygen sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-195350 (JP, A) JP-A-63-212743 (JP, A) JP-A-3-290035 (JP, A) JP-A-2- 204648 (JP, A) JP-A 1-2232137 (JP, A) JP-A 1-222426 (JP, A) JP-A 63-219845 (JP, A) JP-A 61-234241 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/14 310

Claims (1)

(57) [Claims] A first exhaust sensor provided in the exhaust passage upstream of the catalyst body provided in an exhaust passage of the internal combustion engine; a second exhaust sensor provided in the exhaust passage downstream of the catalyst body; The first feedback control value calculated from the first detection signal output from the exhaust sensor performs first feedback control so that the air-fuel ratio becomes a target value, and the duration of the second detection signal output from the second exhaust sensor is reduced.
The air-fuel ratio control of the internal combustion engine that performs the second feedback control to correct the air-fuel ratio inversion delay time of the first feedback control value by the second feedback control value calculated by adding and subtracting the integrated value determined at every integration value determination time. In the device,
The integration value determination time is longer than the duration of the second detection signal.
According to the cycle of the second detection signal, the cycle is shortened so as to be shorter.
So that the integral value determination time becomes shorter as
An air-fuel ratio control device for an internal combustion engine, further comprising control means for controlling the correction .