JP3438536B2 - Air-fuel ratio control device for internal combustion engine and its abnormality diagnosis device - 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 system for an internal combustion engine and an abnormality diagnosis system therefor, and in particular, it is possible to correct variations due to production of O ₂ sensors and variations due to use over time, so that the air-fuel ratio has a target value. to become so-obtained properly controlled and obtained by preventing deterioration of the exhaust harmful component values, also the abnormality of the O ₂ sensor obtained properly detected, obtained and appropriately notify the abnormality of the O ₂ sensor to the user Thus, the present invention relates to an air-fuel ratio control device for an internal combustion engine and an abnormality diagnosis device for the same, which can appropriately repair and replace the O ₂ sensor and prevent deterioration of the exhaust gas harmful component value.

[0002]

2. Description of the Related Art Some internal combustion engines mounted on vehicles or the like are provided with an air-fuel ratio control device for controlling the air-fuel ratio to a target value. The air-fuel ratio control device is provided with an O ₂ sensor in the exhaust passage, and the feedback control amount calculated from the output signal of the O ₂ sensor is corrected by the feedback correction amount to control the fuel so that the air-fuel ratio becomes the target value. There is something.

As a result, the air-fuel ratio controller optimizes the air-fuel ratio of the internal combustion engine to improve combustibility, improve exhaust gas purification efficiency by the catalyst body, and reduce the exhaust gas harmful component value. .

As such an air-fuel ratio control device for an internal combustion engine, Japanese Patent Application Laid-Open Nos. 7-139400 and 8-21 are available.
283 and Japanese Patent Application Laid-Open No. 8-93531.

The one disclosed in Japanese Patent Application Laid-Open No. 7-139400 is provided with an air-fuel ratio control device having upstream and downstream air-fuel ratio sensors in the exhaust passages on the upstream side and the downstream side of the catalyst, respectively. And a catalyst deterioration determination device for determining catalyst deterioration by comparing the ratio of the inversion cycle of the output of the air-fuel ratio sensor on the downstream side with a comparison reference value. The runout degree is calculated, the reference value of the air-fuel ratio runout degree is set according to the engine operating state, the air-fuel ratio runout degree is compared with the reference value to obtain the ratio, and the comparison reference value is increased according to the ratio. It changes in the direction.

Japanese Patent Laid-Open No. 8-21283 discloses an output reversal of an air-fuel ratio sensor by comparing an output value of a second air-fuel ratio sensor downstream of a catalyst with a reference value to determine rich lean. Immediately after that, when it is on the rich side and on the lean side of the reference level range determined by another routine, the proportional component is given to perform proportional-integral control. Otherwise, the proportional component is not given and only the integral component is given. The second air-fuel ratio correction amount is set by performing integral control.

The device disclosed in Japanese Unexamined Patent Publication No. 8-93531 measures the rich duration and the lean duration respectively during air-fuel ratio feedback control, and performs an empty operation based on the ratio of the rich duration and the lean duration. While detecting the deviation of the fuel ratio control point, the extension of the control period is detected from the ratio of the control period in the initial state and the control period obtained by adding the rich continuation time and the lean continuation time, and the ratio of the continuation time and the control The presence or absence of deterioration of the oxygen sensor is determined from the combination with the cycle ratio.

[0008]

In the air-fuel ratio control device, the air-fuel ratio is controlled by the output signal of the O ₂ sensor provided in the exhaust passage. The O ₂ sensor has a characteristic that the output signal changes according to the oxygen concentration in the exhaust gas flowing through the exhaust passage.

However, the output characteristics of the O ₂ sensor have variations due to production, exposure to high temperatures due to use, combustion of oil, etc., resulting in poisoning and the like. Therefore, the air-fuel ratio control device cannot control the air-fuel ratio optimally due to the variation of the output characteristics due to the variation of the O ₂ sensor, and there is a disadvantage that the harmful exhaust gas component value is deteriorated.

Further, the O ₂ sensor may deteriorate and become abnormal due to an unforeseen cause such as supplying leaded gasoline to an unleaded gasoline internal combustion engine. The air-fuel ratio control device
_{2 If the} sensor becomes abnormal, the air-fuel ratio cannot be optimally controlled.

Therefore, if the abnormality of the O ₂ sensor cannot be properly detected, the user cannot be notified of the abnormality of the O ₂ sensor, and as a result, necessary repair and replacement cannot be performed and the sheet is discharged. There is an inconvenience that the value of exhaust harmful components increases.

Meanwhile, even in fault diagnostic apparatus for detecting an abnormality of the O ₂ sensor, if not properly detect an abnormality of the O ₂ sensor can not notice the abnormality of the O ₂ sensor to the user, as a result, Necessary repair and replacement will not be performed, and there is an inconvenience that the value of the exhaust harmful components emitted increases.

Further, recently, the regulation of the exhaust gas harmful component value discharged from the internal combustion engine has become strict, and from this point of view also, the air-fuel ratio control device of the internal combustion engine capable of optimally controlling the air-fuel ratio. And realization of the abnormality diagnostic device is desired.

[0014]

SUMMARY OF THE INVENTION Therefore, according to the present invention, in order to eliminate the above-mentioned inconvenience, the exhaust passage of the internal combustion engine is O
₂ sensor provided in the air-fuel ratio control apparatus for an internal combustion engine that controls so that the air-fuel ratio by correcting the feedback control amount calculated from the output signal of the O ₂ sensor by the feedback correction amount becomes a target value, of the internal combustion engine the O ₂ cycle lean time-period richer time or periodic lean area and periodic rich side area of the output signal of the sensor is measured during operation, the period of the output signal of the O ₂ sensor for each engine load of the internal combustion engine The lean side time target value / cycle rich side time target value or the cycle lean side area target value / cycle rich side area target value is set, and each target value set for each engine load of the internal combustion engine is cooled by the internal combustion engine. Each target value after correction is set by correcting with the water temperature correction coefficient, and each target value after correction with this cooling water temperature correction coefficient and each measured value during operation of the internal combustion engine are set. A value obtained from the difference is stored as a constant speed correction coefficient in the engine load and cooling water temperature maps of the internal combustion engine, and each target value set for each engine load of the internal combustion engine is stored. After correction by the engine load change correction coefficient, each corrected target value is set, and each target value after correction by this engine load change correction coefficient is corrected by the cooling water temperature correction coefficient of the internal combustion engine and corrected. The target values are set, and a value obtained from the difference between the target values after correction by the cooling water temperature correction coefficient and the respective measured values during operation of the internal combustion engine is used as the correction coefficient for acceleration / deceleration for the internal combustion engine. Of the engine load change amount and cooling water temperature are stored in the acceleration / deceleration map, and the feedback correction amount is corrected by the constant speed correction coefficient stored in the constant speed map when the internal combustion engine is at a constant speed. And this constant speed The feedback control amount is corrected by the feedback correction amount after being corrected by the correction coefficient for controlling the air-fuel ratio to the target value, and the acceleration / deceleration stored in the acceleration / deceleration map during acceleration / deceleration of the internal combustion engine. A control means is provided for correcting the feedback correction amount by the time correction coefficient, and correcting the feedback control amount by the feedback correction amount after correction by the acceleration / deceleration correction coefficient to control the air-fuel ratio to the target value. Is characterized by.

[0015] wherein, each target output signal of said O ₂ sensor the measurement value of the output signal of the O ₂ sensor which is measured during operation of the engine is set for each engine load of the internal combustion engine When it becomes larger than the value, it is controlled to add the proportional correction amount of the feedback correction amount.

While the internal combustion engine is at a constant speed, the control means controls so as to correct and add the proportional correction amount of the feedback correction amount by the constant speed correction coefficient stored in the constant speed map. During acceleration / deceleration of the internal combustion engine, control is performed so that the proportional correction amount of the feedback correction amount is corrected and added by the acceleration / deceleration correction coefficient stored in the acceleration / deceleration time map.

The control means controls to add the integral correction component after the proportional correction component of the feedback correction amount is added.

The control means controls the feedback control amount so as not to be corrected within a set time after the proportional correction amount of the feedback correction amount is added.

In the air-fuel ratio control system for an internal combustion engine according to claim 1, at least the area ratio of the cycle lean side area and the cycle rich side area of the output signal of the O ₂ sensor measured when the internal combustion engine is operating. If either one of the condition that the value is out of the judgment range and the condition that the constant speed correction coefficient stored in the constant speed map is the abnormality judgment value or more is satisfied, the O ₂ sensor is judged to be abnormal. It is characterized in that control means for diagnosing is provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the air-fuel ratio control system for an internal combustion engine of the present invention, the control means corrects the feedback correction amount by the constant speed correction coefficient stored in the constant speed map when the internal combustion engine is at a constant speed. Then, the feedback control amount is corrected by the feedback correction amount after being corrected by the constant speed correction coefficient to control the air-fuel ratio to the target value, and is stored in the acceleration / deceleration map during acceleration / deceleration of the internal combustion engine. The feedback correction amount is corrected by the acceleration / deceleration correction coefficient, and the feedback control amount is corrected by the feedback correction amount corrected by the acceleration / deceleration correction coefficient to control the air-fuel ratio to the target value. without being affected by the variation in the output characteristics due to variation in the _second sensor, so that the air-fuel ratio becomes a target value in accordance with the operating state of the internal combustion engine It is possible to sincerely control.

Further, in the air-fuel ratio control system for an internal combustion engine according to the present invention, the control means sets each measured value of the output signal of the O ₂ sensor measured during the operation of the internal combustion engine for each engine load of the internal combustion engine. When the output signal of the O ₂ sensor becomes larger than each target value, control is performed so as to add a proportional correction amount of the feedback correction amount. At this time, when the internal combustion engine is at a constant speed, control is performed to correct and add the proportional correction amount of the feedback correction amount using the constant speed correction coefficient stored in the constant speed map, and at the time of acceleration / deceleration of the internal combustion engine, By controlling so that the proportional correction amount of the feedback correction amount is corrected and added by the acceleration / deceleration correction coefficient stored in the deceleration map, the feedback control amount is set to the target value more depending on the operating state of the internal combustion engine. You can get closer.

Further, in the air-fuel ratio control apparatus for an internal combustion engine according to the present invention, the control means controls the addition of the proportional correction amount of the feedback correction amount and then the integral correction amount to add the proportional correction amount. The hunting of the output signal of the O ₂ sensor can be prevented, and the feedback correction amount is controlled so as not to be inverted within the set time after the proportional correction amount of the feedback correction amount is added. Fluctuation can be prevented.

Further, in this abnormality diagnosing apparatus for an internal combustion engine, at least the cycle lean side area and cycle rich side area of the output signal of the O ₂ sensor measured by the control means at the time of operation of the internal combustion engine by the air-fuel ratio control apparatus. If either one of the condition that the area ratio is outside the judgment range and the condition that the constant speed correction coefficient stored in the constant speed map is equal to or greater than the abnormal judgment value is satisfied, the O ₂ sensor the by diagnoses it as abnormal, O ₂ without being affected by variation in output characteristics due to variation of the sensor, the function of the O ₂ sensor can be properly diagnosed.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 17 show an embodiment of the present invention. In FIG. 17, 2 is an internal combustion engine mounted on a vehicle (not shown), 4 is a cylinder block, 6 is a cylinder head, 8 is an oil pan, and 10 is a crankshaft.

The internal combustion engine 2 is provided with an air cleaner 12, an intake pipe 14, a throttle body 16, a surge tank 18 and an intake manifold 20 as an intake system, and an intake passage 22.
Is provided. The throttle body 16 is provided with a throttle valve 24. Further, the internal combustion engine 2 includes an exhaust manifold 26 and a front catalytic converter 28 as an exhaust system.
Exhaust pipe 30, rear catalytic converter 32, rear exhaust pipe 3
4 and an exhaust passage 36 are provided.

The internal combustion engine 2 is provided with a fuel injection valve 38 as a fuel system. The fuel injection valve 38 injects and supplies the fuel supplied from the fuel tank 40. The fuel tank 40 is provided with a level gauge 42.

The internal combustion engine 2 is provided with an ignition device 44, a water temperature sensor 46 for detecting the cooling water temperature, a crank angle sensor 48 for detecting the rotation angle of the crankshaft 10, and an intake air temperature sensor for detecting the intake air temperature. An air temperature sensor 50 is provided, a throttle opening sensor 52 for detecting the opening of the throttle valve 24 is provided, and an intake pressure sensor 54 for detecting intake pressure is provided.

The internal combustion engine 2 includes an evaporated fuel control device 5
6 is provided. The evaporated fuel control device 56 is provided with a canister 58 that adsorbs and holds the evaporated fuel in the fuel tank 40 and that releases and discharges the adsorbed and held evaporated fuel.
The canister 58 is connected to the fuel tank 4 by the evaporation passage 60.
The purge passage 62 communicates with the surge tank 18, and the atmosphere passage 64 communicates with the atmosphere.

A fuel tank 40 is installed in the evaporation passage 60.
A tank internal pressure sensor 66, a separator 68, and a pressure control valve 70 are sequentially provided from the side. The pressure control valve 70 communicates with the surge tank 18 via a pressure passage 72. A negative pressure control valve 74 is provided in the pressure passage 72. A purge control valve 76 is provided in the purge passage 62. An atmosphere control valve 78 is provided in the atmosphere passage 64.

The internal combustion engine 2 is provided with an exhaust gas recirculation control device 80 for recirculating a part of exhaust gas to the intake system. The exhaust gas recirculation control device 80 includes an EGR valve 82.
The EGR valve 82 is provided in an EGR passage (not shown) that connects the exhaust system and the intake system.

Further, the exhaust gas recirculation control device 80 comprises a back pressure control valve 84, an EGR control valve 86 and an EGR judgment valve 88. The EGR valve 82 is controlled in the pressure applied by these valves 84, 86, 88 and its operation is controlled to adjust the EGR amount.

The internal combustion engine 2 includes an air-fuel ratio controller 90.
Is provided. The air-fuel ratio control device 90 is provided with an O2 sensor as an exhaust sensor in the exhaust passage 36. In this embodiment, the exhaust manifold 26 is provided with a front O ₂ sensor 92 and the rear exhaust pipe 34 is provided with a rear O ₂ sensor 94. The front O ₂ sensor 92 and the rear O ₂ sensor 94 are connected to the control means 96 of the air-fuel ratio control device 90.

The control means 96 includes the fuel injection valve 3
8, a level gauge 42, an ignition device 44, a water temperature sensor 46, a crank angle sensor 48, and an intake air temperature sensor 50.
A throttle opening sensor 52 and an intake pressure sensor 54
The tank internal pressure sensor 66, the negative pressure control valve 74, the purge control valve 76, the atmosphere control valve 78, the EGR control valve 86, and the EGR determination valve 88 are connected to each other.

The air-fuel ratio control device 90 controls the front O ₂ sensor 92 and the rear O ₂ sensor 94 by the control means 96.
The feedback control amount calculated from the output signal is corrected by the feedback correction amount to control the fuel injection valve 38 so that the air-fuel ratio becomes the target value.

The air-fuel ratio control device 90 for the internal combustion engine 2 is
The control means 96 measures the period lean side time TFBL, the period rich side time TFBR, the period lean side area SFL, and the period rich side area SFR of the output signal of the O ₂ sensor 92 when the internal combustion engine 2 is operating. Engine load Qa
Setting the cycle lean time target value TFBLO · cycle richer time target value TFBRO · periodic lean area target value SFLO · periodic rich side area target value SFRO of the output signal of the O ₂ sensor 92 for each.

The control means 96 controls the target values TFBLO and TFBRO set for each engine load Qa of the internal combustion engine 2.
-SFLO-SFRO is corrected by the cooling water temperature correction coefficient C of the internal combustion engine 2 and each target value TFBLO-TF after correction is corrected.
BRO / SFLO / SFRO are set, and the target values TFBLO / TFB after correction by the cooling water temperature correction coefficient C are set.
The engine load Qa and the cooling water temperature of the internal combustion engine 2 are defined as the correction coefficient A for constant speed, which is a value obtained from the difference between RO / SFLO / SFRO and the measured values TFBL / TFBR / SFL / SFR during operation of the internal combustion engine 2. It is stored in the map for constant speed of Wa.

The control means 96 controls the target values TFBLO, TFBRO, SFLO set for each engine load Qa.
-SFRO is corrected by the engine load change amount correction coefficient B of the internal combustion engine 2 and each corrected target value TFBLO-TFBRO
・ SFLO ・ SFRO is set, and each target value TFBLO ・ TFBR after correction by this engine load change amount correction coefficient B
O · SFLO · SFRO is corrected by the cooling water temperature correction coefficient C of the internal combustion engine 2 and each corrected target value TFBLO · T
FBRO / SFLO / SFRO is set, and each target value TFBLO / TF after correction by the cooling water temperature correction coefficient C is performed.
A value obtained from the difference between BRO / SFLO / SFRO and each measured value TFBL / TFBR / SFL / SFR during operation of the internal combustion engine 2 is used as the acceleration / deceleration correction coefficient D.
The engine load change amount ΔQa and the cooling water temperature Wa are stored in the acceleration / deceleration time map.

The control means 96 controls the constant speed correction coefficient A stored in the constant speed map when the internal combustion engine 2 is at a constant speed.
To correct the feedback control amount by the feedback correction amount corrected by the constant correction coefficient A for constant speed to control the air-fuel ratio to the target value. The feedback correction amount is corrected by the acceleration / deceleration correction coefficient D stored in the acceleration / deceleration map, and the acceleration / deceleration correction coefficient D is corrected.
The feedback control amount is corrected by the feedback correction amount after the correction by the control so that the air-fuel ratio becomes the target value.

Next, the operation of the air-fuel ratio control device 90 will be described.

The air-fuel ratio controller 90, as shown in FIG.
When the internal combustion engine 2 is started and the control is started (step 100), the proportional correction amount P and the integral correction amount I of the feedback correction amount are divided into a constant speed (Fig. 9) and an acceleration / deceleration (Fig. 12). It is corrected (step 102). This correction is performed as follows.

First, it is determined whether the internal combustion engine 2 is at a constant speed (step 104). This judgment (Step 10
4) is YES, that is, when the internal combustion engine 2 is at a constant speed, as shown in FIGS. 3 and 4, the cycle lean side time TFBL / cycle rich side time TFB of the output signal of the O ₂ sensor 92.
R / cycle lean side area SFL / cycle rich side area SFR
Are measured at regular time intervals (step 106).

The cycle lean side time TFBL is the time during which the output signal of the O ₂ sensor 92 continues on the lean side of the cycle. The period rich side time TFBR is the O ₂ sensor 92.
Is the time when the output signal of (1) continues on the rich side of the cycle. The cycle lean side area SFL is an area surrounded by the output signal of the O ₂ sensor 92 on the lean side of the cycle. The cycle rich side area SFR is an area surrounded by the output signal of the O ₂ sensor 92 on the cycle rich side.

Next, these measured values TFBL and TFBR
As shown in FIGS. 5 and 6, the SFL and SFR are set to the cycle lean side time target value TFBLO, the cycle rich side time target value TFBRO, and the cycle lean side area target value SFLO, which are set for each engine load Qa of the internal combustion engine 2. The period rich side area target value SFRO is compared at regular time intervals (step 108).

The above target values TFBLO and TFBR
As shown in FIG. 8, O · SFLO · SFRO is corrected by multiplying the cooling water temperature correction coefficient C of the internal combustion engine 2, and the corrected target values TFBLO · TFBRO · SFL are corrected.
Set to O ・ SFRO.

In the above (step 108), the measured values TFBL, TFBR, SFL, SFR, and the corrected target values TFBLO, TFBRO, SFLO, SF.
Compare with RO.

Each target value TFBLO · TFB after the correction
RO / SFLO / SFRO are the above-mentioned measured values TFBL / T
It is determined whether or not FBR / SFL / SFR or more (step 110).

When this determination (step 110) is NO, the control is ended by stopping the internal combustion engine 2 (step 118). On the other hand, this judgment (step 110) is Y
In the case of ES, the proportional correction amount P is added by multiplying the constant speed correction coefficient A stored in the constant speed map of the engine load Qa and the cooling water temperature Wa of the internal combustion engine 2 shown in FIG. 9 (step 112).

After the addition of the proportional correction amount P, FIG.
Be sure to add the integral correction amount I as shown in case 3 of
₂ Hunting of the output signal of the sensor 92 is prevented. Even if the output signal of the O ₂ sensor 92 is not inverted after the addition of the proportional correction amount P, the proportional correction amount P is followed by the integral correction amount I without further addition. Also,
The feedback correction amount is controlled not to be inverted within the set time TI after adding the proportional correction amount P.

Thereafter, as shown in FIGS. 3 and 4, the final values of the cycle lean side time TFBL, the cycle rich side time TFBR, the cycle lean side area SFL, and the cycle rich side area SFR of the output signal of the O ₂ sensor 92 are respectively set. Measured, and as shown in FIG. 7, target values TFBLO, TFBRO, SFLO, SF
A constant speed correction coefficient A is obtained from the difference between RO and each of the measured values TFBL / TFBR / SFL / SFR (step 11).
4).

The correction coefficient A for constant speed obtained is stored in the map for constant speed (FIG. 9) of the engine load Qa and the cooling water temperature Wa of the internal combustion engine 2 (step 116), and the internal combustion engine 2 is stopped. End the control by (step 11
8).

There are various methods of storing the correction coefficient A for constant speed, such as a method of directly storing it and a method of performing weighted averaging on the previous value and storing it. Also,
The stored constant speed correction coefficient A is backed up and retained even after the internal combustion engine 2 is stopped.

On the other hand, if the determination as to whether or not the internal combustion engine 2 is at a constant speed (step 104) is NO, control is performed as shown in FIG.

That is, when accelerating and decelerating the internal combustion engine 2, as shown in FIG.
As shown in FIG. 4, the cycle lean side time TFBL, the cycle rich side time TFBR, the cycle lean side area SFL, and the cycle rich side area SFR of the output signal of the O ₂ sensor 92 are measured at regular time intervals (step 120).

Next, as shown in FIGS. 5 and 6, the internal combustion engine 2
As shown in FIG. 8, for the cycle lean side time target value TFBLO, the cycle rich side time target value TFBRO, the cycle lean side area target value SFLO, and the cycle rich side area target value SFRO set for each engine load Qa of It is corrected by multiplying the cooling water temperature correction coefficient C of the internal combustion engine 2, and
As shown in FIG. 11, the correction is performed by multiplying the engine load change amount correction coefficient B of the internal combustion engine 2, and each corrected target value T
FBLO / TFBRO / SFLO / SFRO are set (step 122).

Target values TFBLO · TFB after the correction
RO / SFLO / SFRO are the above-mentioned measured values TFBL / T
It is determined whether or not it is equal to or more than FBR / SFL / SFR (step 124).

When this judgment (step 124) is NO, the control is ended by stopping the internal combustion engine 2 (step 132). On the other hand, this determination (step 124) is Y
In the case of ES, a proportional correction amount P obtained by multiplying the engine load change amount ΔQa of the internal combustion engine 2 and the acceleration / deceleration correction coefficient D stored in the acceleration / deceleration time map of the cooling water temperature Wa shown in FIG. 12 is added. (Step 126).

After adding the proportional correction amount P, the integral correction amount I is added to prevent hunting of the output signal of the O ₂ sensor 92. Even if the output signal of the O ₂ sensor 92 is not inverted after the addition of the proportional correction amount P, the proportional correction amount P is followed by the integral correction amount I without further addition. In addition, the set time T after adding the proportional correction amount P
In I, control is performed so that the feedback correction amount is not inverted.

Thereafter, as shown in FIGS. 3 and 4, the final values of the cycle lean side time TFBL, the cycle rich side time TFBR, the cycle lean side area SFL, and the cycle rich side area SFR of the output signal of the O ₂ sensor 92 are respectively set. Measured, and as shown in FIG. 7, target values TFBLO, TFBRO, SFLO, SF
The correction coefficient A for constant speed is obtained from the difference between RO and each measured value TFBL / TFBR / SFL / SFR (step 12).
8).

The constant correction coefficient A for constant speed thus obtained is used as a correction coefficient D for acceleration / deceleration, and a map for acceleration / deceleration of the engine load change amount ΔQa of the internal combustion engine 2 and the cooling water temperature Wa (see FIG. 1).
It is stored in 2) (step 130) and the control is ended by stopping the internal combustion engine 2 (step 132).

There are various methods of storing the acceleration / deceleration correction coefficient D, such as a method of directly storing the value and a method of performing weighted averaging on the previous value and storing the value. Also,
The stored acceleration / deceleration correction coefficient D is backed up and stored even after the internal combustion engine 2 is stopped.

In this way, the air-fuel ratio control device 90 corrects the feedback correction amount by the control means 96 by the constant speed correction coefficient A stored in the constant speed map when the internal combustion engine 2 is at a constant speed, This constant speed correction coefficient A
The feedback control amount is corrected by the corrected feedback correction amount to control the air-fuel ratio to the target value, and the acceleration / deceleration correction coefficient D stored in the acceleration / deceleration map during acceleration / deceleration of the internal combustion engine 2 is controlled. correcting the feedback correction amount, by controlling so that the air-fuel ratio becomes the target value by correcting the feedback control amount by the feedback correction amount after correction by the deceleration correction coefficient, the output characteristics due to variation in the O ₂ sensor 92 Can be appropriately controlled so that the air-fuel ratio becomes the target value according to the operating state of the internal combustion engine 2 without being affected by the fluctuation of

Further, the air-fuel ratio control device 90 has the O ₂ measured by the control means 96 when the internal combustion engine 2 is operating.
Each measured value TFBL / TFBR / of the output signal of the sensor 92
SFL / SFR is a target value TFBLO / TF of the output signal of the O ₂ sensor set for each engine load Qa of the internal combustion engine 2.
When it becomes larger than BRO / SFLO / SFRO, control is performed to add the proportional correction amount P of the feedback correction amount.

At this time, when the internal combustion engine 2 is at a constant speed, control is performed to correct and add the proportional correction amount P of the feedback correction amount by the constant speed correction coefficient A stored in the constant speed map. During acceleration / deceleration of the engine 2, the proportional correction amount P of the feedback correction amount is corrected by the correction coefficient D for acceleration / deceleration stored in the acceleration / deceleration map, and control is performed to add the feedback correction amount to the operating state of the internal combustion engine 2. Accordingly, the feedback control amount can be brought closer to the target value.

Further, the air-fuel ratio control device 90 controls the addition of the proportional correction amount P by adding the proportional correction amount P of the feedback correction amount after the addition by the control means 96 by the control means 96. O ₂ sensor 92
Of the output signal can be prevented, and the feedback correction amount is controlled so as not to be inverted within the set time TI after the proportional correction amount P of the feedback correction amount is added. Can be prevented.

As described above, the air-fuel ratio control device 90 of the internal combustion engine 2 is not affected by the variation of the output characteristic due to the variation of the O ₂ sensor 92, and the air-fuel ratio is set to the target value according to the operating state of the internal combustion engine 2. It can be properly controlled to reach the value.

Therefore, the air-fuel ratio control device 90 of the internal combustion engine 2 can correct the variation of the output characteristic due to the variation of the O ₂ sensor 92 due to the production and the variation due to the use over time, and the air-fuel ratio becomes the target value. Therefore, it is possible to appropriately control so as to prevent the harmful value of exhaust gas from deteriorating.

The internal combustion engine 2 is also provided with an abnormality diagnosis device 98. The abnormality diagnosis device 98 is shown in FIGS.
As shown in FIG. 6, the cycle lean side area S of the output signal of the O ₂ sensor 92 measured by the control means 96 at least during the operation of the internal combustion engine 2 by the air-fuel ratio control device 90.
Area ratio SFR / SFL of FL / cycle rich side area SFR
Is a value outside the judgment range {SFMIN ≧ (SFR / SFL) or (SFR / SFL) ≧ SFMAX}, and
The O ₂ sensor 92 is determined to be abnormal if either one of the condition that the constant speed correction coefficient A stored in the constant speed map is equal to or greater than the abnormality determination value MFA (A ≧ MFA) is satisfied. To diagnose.

Next, the operation of the abnormality diagnosis device 98 will be described.

The abnormality diagnosing device 98, as shown in FIG.
When the diagnosis is started (step 200), as shown in FIG. 14, the time ratio TFBR / TFBL of the period lean side time TFBL and the period rich side time TFBR of the output signal of the O ₂ sensor 92 to be measured is the out-of-judgment value {TFBMIN. ≧
(TFBR / TFBL) or (TFBR / TFB
L) ≧ TFBMAX} is determined (step 202).

In this determination (step 202), the time ratio TFBR / TFBL is less than or equal to the time ratio determination minimum value {TFB.
MIN ≧ (TFBR / TFBL)} or greater than or equal to the time ratio determination maximum value {(TFBR / TFBL) ≧ TFBM
If AX} is YES, the O ₂ sensor 92 is diagnosed as abnormal and the user is notified by lighting a lamp (not shown) or the like (step 212), and the diagnosis is finished (step 214).

In this judgment (step 202), the time ratio TFBR / TFBL is within the judgment range {TFBMIN <
(TFBR / TFBL) <TFBMAX} and NO
In the case of, the measured O ₂ sensor 9 as shown in FIG.
The area ratio SFR / SFL of the cycle lean side area SFL and the cycle rich side area SFR of the output signal of No. 2 is outside the judgment range {S
FMIN ≧ (SFR / SFL) or (SFR / SF
L) ≧ SFMAX} is determined (step 204).

In this determination (step 204), the area ratio SFR / SFL is less than or equal to the area ratio determination minimum value {SFMIN.
≧ (SFR / SFL)} or more than the area ratio judgment maximum value {(SFR / SFL) ≧ SFMAX} and Y
In the case of ES, the O ₂ sensor 92 is diagnosed as abnormal and the user is notified by lighting a lamp or the like (step 212), and the diagnosis is finished (step 214).

In this judgment (204), the area ratio SF
R / SFL is within the judgment range value {SFMIN <(SFR / SF
L) <SFMAX} and NO, as shown in FIG. 16, it is determined whether or not the constant speed correction coefficient A stored in the constant speed map is equal to or larger than the abnormality determination value MFA (A ≧ MFA). It is determined (step 206).

In this judgment (step 206), the correction coefficient A for constant speed is equal to or larger than the abnormality judgment value MFA (A ≧ MF
If YES in step A), the O ₂ sensor 92 is diagnosed as abnormal, and the user is notified by lighting a lamp or the like (step 212), and the diagnosis is finished (step 214).

In this determination (step 206), the constant speed correction coefficient A is less than the regular determination value MFA (A <MF
In the case of A) and NO, the O ₂ sensor 92 is diagnosed as normal (step 208) and the diagnosis is finished (step 2).
14).

As described above, in the abnormality diagnosing device 98, the area ratio S of at least the cycle lean side area SFL and the cycle rich side area SFR of the O ₂ sensor 92 is controlled by the control means 96.
FR / SFL is out of judgment range value {SFMIN ≧ (SFR / S
FL) or (SFR / SFL) ≧ SFMAX} and the constant speed correction coefficient A is the abnormal determination value MFA.
If any one of the above conditions (A ≧ MFA) is satisfied, the O ₂ sensor 92 is diagnosed as abnormal so that it is not affected by the variation of the output characteristic due to the variation of the O ₂ sensor 92. , O ₂ sensor 92 can be properly diagnosed.

[0077] Therefore, the failure detect device 98 the engine 2, the abnormality of the O ₂ sensor 92 obtained properly detect an abnormality of the O ₂ sensor 92 can be properly notified to the user by the detection . The user is notified of O ₂ by this notification.
The sensor 92 can be appropriately repaired and replaced, and deterioration of the exhaust gas harmful component value can be prevented.

[0078]

As described above, the air-fuel ratio control system for an internal combustion engine according to the present invention sets the target air-fuel ratio in accordance with the operating state of the internal combustion engine without being affected by the variation of the output characteristic due to the variation of the O ₂ sensor. It can be properly controlled to reach the value. Therefore, air-fuel ratio control apparatus for an internal combustion engine, O ₂
Variations in the output characteristics of the sensor due to production and variations due to use over time can be corrected, the air-fuel ratio can be appropriately controlled to reach the target value, and deterioration of the exhaust gas harmful component value can be prevented.

[0079] Further, the abnormality diagnosis apparatus for an internal combustion engine of the present invention, O ₂ is possible without being affected on variations in the output characteristics due to variations of the sensor, the function of the O ₂ sensor can be properly diagnosed. Therefore, the abnormality diagnosis apparatus for an internal combustion engine is an abnormality of the O ₂ sensor obtained properly detected, obtained and appropriately notify the abnormality of the O ₂ sensor by the detection to the user,
The O ₂ sensor can be appropriately repaired and replaced, and the deterioration of the exhaust gas harmful component value can be prevented.

[Brief description of drawings]

FIG. 1 is a flowchart of control by an air-fuel ratio control device showing an embodiment of the present invention.

FIG. 2 is a flowchart of control continued from FIG.

FIG. 3 is a timing chart of control at a constant speed.

FIG. 4 is another timing chart of control at a constant speed.

FIG. 5 is a diagram showing setting of a cycle lean side time target value and a cycle rich side time target value.

FIG. 6 is a diagram showing setting of a cycle lean side area target value and a cycle rich side area target value.

FIG. 7 is a diagram showing setting of a correction coefficient for constant speed.

FIG. 8 is a diagram showing setting of a cooling water temperature correction coefficient.

FIG. 9 is a diagram showing a map for constant speed according to engine load and cooling water temperature.

FIG. 10 is a timing chart of control during acceleration / deceleration.

FIG. 11 is a diagram showing setting of an engine load change amount correction coefficient.

FIG. 12 is a diagram showing an acceleration / deceleration map according to the engine load change amount and the cooling water temperature.

FIG. 13 is a flow chart of O ₂ sensor diagnosis by the abnormality diagnosis device.

FIG. 14 is a diagram showing a judgment range of a time ratio based on a cycle lean side time and a cycle rich side time.

FIG. 15 is a diagram showing a judgment area of an area ratio based on a cycle lean side area and a cycle rich side area.

FIG. 16 is a diagram showing an abnormality determination value of a constant speed correction coefficient depending on engine load and cooling water temperature.

FIG. 17 is a system configuration diagram of an air-fuel ratio control device and an abnormality diagnosis device.

[Explanation of symbols]

2 Internal combustion engine 22 Intake passage 36 Exhaust passage 38 Fuel injection valve 48 Crank angle sensor 52 Throttle opening sensor 54 Intake pressure sensor 82 EGR valve 90 Air-fuel ratio control device 92 Front O ₂ sensor 94 Rear O ₂ sensor 96 Control means 98 Abnormality diagnosis apparatus

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02D 45/00 368 F02D 45/00 368G (56) References JP-A-8-4573 (JP, A) JP-A-63-189637 (JP, A) JP-A-1-277637 (JP, A) JP-A-2-196150 (JP, A) JP-A-6-264797 (JP, A) JP-A-9-96235 (JP, A) Kaihei 8-43335 (JP, A) Actual development Sho 62-171638 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 41/14-41/22 F02D 45/00

Claims (6)

(57) [Claims] 1. An internal combustion engine in which an O ₂ sensor is provided in an exhaust passage of an internal combustion engine, and a feedback control amount calculated from an output signal of the O ₂ sensor is corrected by a feedback correction amount to control an air-fuel ratio to a target value. In an air-fuel ratio control device for an engine, the period lean side time / period rich side time or the period lean side area / period rich side area of the output signal of the O ₂ sensor is measured during operation of the internal combustion engine to obtain the engine of the internal combustion engine. A cycle lean side time target value / cycle rich side time target value or a cycle lean side area target value / cycle rich side area target value of the output signal of the O ₂ sensor is set for each load, and for each engine load of this internal combustion engine Each set target value is corrected by the cooling water temperature correction coefficient of the internal combustion engine to set each corrected target value, and each corrected target value by this cooling water temperature correction coefficient A value obtained from the difference between each measured value during operation of the internal combustion engine is stored as a constant speed correction coefficient in the engine load of the internal combustion engine and the constant temperature map of the cooling water temperature for each engine load. Is corrected by the engine load change correction coefficient of the internal combustion engine to set the corrected target values, and the target values after correction by the engine load change correction coefficient are set to the internal combustion engine. It is calculated from the difference between each target value after correction by the cooling water temperature correction coefficient and each corrected target value is set, and each measured value when the internal combustion engine is operating. The value is stored in the acceleration / deceleration map of the engine load change amount and the cooling water temperature of the internal combustion engine as the acceleration / deceleration correction coefficient,
At a constant speed of the internal combustion engine, the feedback correction amount is corrected by the constant speed correction coefficient stored in the constant speed map, and the feedback control is performed by the feedback correction amount after correction by the constant speed correction coefficient. The amount is corrected to control the air-fuel ratio to a target value, and at the time of acceleration / deceleration of the internal combustion engine, the feedback correction amount is corrected by the acceleration / deceleration time correction coefficient stored in the acceleration / deceleration time map. An air-fuel ratio control device for an internal combustion engine, comprising: a control unit that corrects the feedback control amount by a feedback correction amount that has been corrected by an acceleration / deceleration correction coefficient and controls the air-fuel ratio to a target value. Wherein said control means, the measurement value of the output signal of the O ₂ sensor which is measured during operation of the internal combustion engine is an output signal of the O ₂ sensor that is set for each engine load of the internal combustion engine The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein control is performed so as to add a proportional correction amount of the feedback correction amount when the value becomes larger than each target value. 3. The control means controls to correct and add a proportional correction amount of the feedback correction amount by a constant speed correction coefficient stored in the constant speed map when the internal combustion engine has a constant speed. At the same time, during acceleration / deceleration of the internal combustion engine, control is performed so that the proportional correction amount of the feedback correction amount is corrected and added by the acceleration / deceleration correction coefficient stored in the acceleration / deceleration map. Item 3. An air-fuel ratio control device for an internal combustion engine according to item 2. 4. The air-fuel ratio control apparatus for an internal combustion engine according to claim 2, wherein the control means controls to add an integral correction amount after adding a proportional correction amount of the feedback correction amount. 5. The internal combustion engine according to claim 2, wherein the control unit controls the feedback control amount not to be corrected within a set time after adding the proportional correction amount of the feedback correction amount. Air-fuel ratio control system for engines. 6. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein at least an area of a cycle lean side area / a cycle rich side area of an output signal of the O ₂ sensor measured when the internal combustion engine is operating. If either the condition that the ratio is out of the judgment range or the condition that the constant speed correction coefficient stored in the constant speed map is equal to or greater than the abnormality judgment value is satisfied, the O ₂ sensor is set to An abnormality diagnosis apparatus for an internal combustion engine, comprising a control means for diagnosing an abnormality.