JPH11326137A - Engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the effectiveness of the air/fuel ratio feedback control and the diagnosis on the subsystem of an exhaust system of an engine controller by diagnosing an air/fuel ratio sensor itself. SOLUTION: An engine controller is provided with a fuel injection pulse width changing means 106 which changes the target air/fuel ratio of an engine so that the air/fuel ratio state of the engine may become opposite to a rich- or lean-side air-fuel ratio state when an air/fuel ratio sensor 518 detects the rich- or lean-side air-fuel ratio state for a prescribed period of time or longer or a throttle opening changing means 17 which changes the opening of a throttle so that the air/fuel ratio state may become the opposite to the detected state and an air/fuel ratio sensor diagnosing means 108 which discriminates that the sensor 518 is abnormal when the sensor 518 does not detect the opposite air-fuel ratio sensor within a prescribed period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing feedback control of an air-fuel ratio by an air-fuel ratio sensor for measuring an oxygen concentration in exhaust gas and detecting an air-fuel ratio, and for diagnosing a catalyst, EGR, and the like. In particular, the present invention relates to an electronic engine control device that diagnoses the air-fuel ratio sensor itself and reports failure information of the air-fuel ratio sensor.

[0002]

2. Description of the Related Art Conventionally, there has been known an apparatus for measuring the oxygen concentration in exhaust gas with an air-fuel ratio sensor and performing feedback control of the air-fuel ratio.

The air-fuel ratio sensor is used for various subsystems related to an exhaust system, for example, a catalyst diagnostic device, an EGR device, an exhaust system, in addition to the application of the air-fuel ratio feedback control, by using the air-fuel ratio sensor alone or in combination with other sensor signals. It is also used effectively for leak diagnostics and secondary air supply diagnostics.

[0004] For example, Japanese Patent Application Laid-Open No. 7-77145 describes an engine control device for diagnosing the degree of deterioration of a catalyst using output values of air-fuel ratio sensors disposed upstream and downstream of the catalyst.

Japanese Patent Application Laid-Open No. 7-294385 discloses a device for diagnosing an EGR device based on an output value of an air-fuel ratio sensor provided in an exhaust passage, a detected value of an intake air amount, and the like.

Japanese Patent Application Laid-Open No. 8-177605 discloses an apparatus for detecting the oxygen concentration in exhaust gas using an air-fuel ratio sensor and diagnosing a leak in an exhaust system using the detected value.

Further, Japanese Patent Application Laid-Open No. 7-109920 describes a device for diagnosing a secondary air supply device based on a fuel supply amount and an output value of an air-fuel ratio sensor.

[0008]

Although the above-mentioned prior art describes a diagnosis for detecting a malfunction of the exhaust system subsystem, it does not consider a diagnosis of the air-fuel ratio sensor itself which is a key sensor as an input. If the air-fuel ratio sensor itself fails, the air-fuel ratio feedback control cannot be completed, and diagnosis of these exhaust subsystems using the output value of the air-fuel ratio sensor impairs its reliability.

In view of the above, it is an object of the present invention to ensure the effectiveness of air-fuel ratio feedback control and exhaust system subsystem diagnosis by diagnosing the air-fuel ratio sensor itself.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio sensor which is disposed in an exhaust pipe of an engine and detects an air-fuel ratio of a combustion gas from a component of the exhaust gas, and an air-fuel ratio sensor for realizing a target air-fuel ratio. And an air-fuel ratio feedback control means for controlling a fuel injection amount in accordance with the air-fuel ratio detected in the step (a), wherein the air-fuel ratio sensor changes the air-fuel ratio state on either the rich side or the lean side for a predetermined time. When continuously detected, target air-fuel ratio changing means for changing the target air-fuel ratio so that the air-fuel ratio state is opposite to the detected air-fuel ratio state, and after the target air-fuel ratio is changed, the reverse air-fuel ratio is changed within a predetermined time. When the air-fuel ratio sensor does not detect the air-fuel ratio state, the air-fuel ratio sensor is determined to be abnormal.

It is another object of the present invention to provide an air-fuel ratio sensor which is disposed in an exhaust pipe of an engine and detects an air-fuel ratio of a combustion gas from a component of the exhaust gas, and an air-fuel ratio sensor detected by the air-fuel ratio sensor to realize a target air-fuel ratio. An air-fuel ratio feedback control means for operating a throttle opening in accordance with a fuel ratio, wherein the air-fuel ratio sensor continuously detects an air-fuel ratio state on either the rich side or the lean side for a predetermined time or more. At this time, throttle opening changing means for changing the throttle opening so that the air-fuel ratio state is opposite to the detected air-fuel ratio state, and after changing the target air-fuel ratio, the reverse air-fuel ratio state is changed within a predetermined time. This is achieved by including an air-fuel ratio sensor abnormality determination unit that determines that the air-fuel ratio sensor is abnormal when the air-fuel ratio sensor does not detect.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an engine system according to an embodiment of the present invention. In the figure, air taken in by an engine is taken in from an inlet portion 502a of an air cleaner 502, passes through an air flow meter 503, passes through a throttle body in which a throttle valve 505 for controlling the intake flow rate is accommodated, and enters a collector 506.

[0014] Here, the intake air is distributed to each intake pipe connected to each cylinder of the engine 507 and guided into the cylinder.

On the other hand, a fuel such as gasoline is first pressurized by a fuel pump 510 from a fuel tank 514, and is secondarily pressurized by a fuel pump 511, and is injected into an injector.
509 is supplied to the plumbed fuel system. The primary pressurized fuel is supplied to the fuel pressure regulator 512 at a constant pressure.
(For example, 3 kg / cm ² ), and the fuel that has been secondarily pressurized to a higher pressure is regulated to a constant pressure (for example, 60 kg / m ² ) by a fuel pressure regulator 513 and provided to each cylinder. The injector 509 is injected into the cylinder. The injected fuel is the ignition coil 52
The ignition signal is fired by the ignition coil 508 in response to the ignition signal whose voltage has been increased in step 2.

A signal representing the flow rate of the intake air is output from the air flow meter 503 and input to the control unit 515.

Further, a throttle sensor 504 for detecting the opening of the throttle valve 505a is attached to the throttle body.
To be entered.

Reference numeral 516 denotes a crank angle sensor attached to the camshaft shaft, which outputs a reference angle signal REF indicating the rotational position of the crankshaft and an angle signal POS for detecting a rotation signal (rotation speed). Is also input to the control unit 515.

The air-fuel ratio sensor 518 is provided before the catalyst 520 in the exhaust pipe 519, and an output signal is input to the control unit 515. In order to diagnose the catalyst, the air-fuel ratio sensor 524 is also provided after the catalyst 520.

Although FIG. 2 has described the in-cylinder injection engine system for directly injecting fuel into the cylinder, the present invention is also effective for a port injection engine system. As shown in FIG. 3, the main part of the control unit 515 is composed of an I / O LSI including an MPU 603, a ROM 602, a RAM 604, and an A / D converter, and receives signals from various sensors for detecting the operating state of the engine. Is input as input, performs a predetermined calculation process, outputs various control signals calculated as a result of the calculation, supplies predetermined control signals to the injector 509 and the ignition coil 522, and controls the fuel supply amount. And ignition timing control.

FIG. 1 is a block diagram showing the diagnosis of the air-fuel ratio sensor executed by the control unit 515 in the engine control system as described above.

The air-fuel ratio sensor 518 detects the air-fuel ratio from the oxygen concentration in the exhaust gas of the engine, and inputs the detected air-fuel ratio to the long-term rich judgment means 101, the long-term lean judgment means 103 and the air-fuel ratio sensor diagnosis means 108.

The long-term rich judging means 101 judges whether the signal of the air-fuel ratio sensor is rich for a long time. If the signal continues to be rich for a long time, the target air-fuel ratio is changed by the target air-fuel ratio changing means 102 and the actual air-fuel ratio changing means 105 The actual air-fuel ratio is set to lean, and a diagnosis is made as to whether the sensor characteristics on the lean side are correct.

On the other hand, the long-term lean determining means 103 determines whether the signal of the air-fuel ratio sensor is lean for a long time, and if the lean operation continues for a long time, the target air-fuel ratio changing means 104 changes the target air-fuel ratio. At 105, the actual air-fuel ratio is set to rich, and a diagnosis is made as to whether the sensor characteristics on the rich side are correct.

When there is a command to change the air-fuel ratio from the actual air-fuel ratio changing means 105, the air-fuel ratio can be changed by the following two means.

One is a fuel injection pulse width changing means 106, which reduces the pulse width when the fuel is lean and increases the pulse width when the fuel is rich. The other is a throttle opening changing means 107. The opening is small when the air conditioner is rich, and is large when the air condition is lean.

In the air-fuel ratio sensor diagnostic means 108, the fuel injection pulse width changing means 106 or the throttle opening degree changing means 1
If it is confirmed by the output of the air-fuel ratio sensor 518 that the actual air-fuel ratio has changed to lean or rich over stoichiometry by 07, it is diagnosed that the sensor is normal. The air-fuel ratio sensor 5
If the output of 18 does not change, it is diagnosed that the sensor is abnormal.

Here, examples of the characteristics of the air-fuel ratio sensor are shown in FIGS.
As shown in FIG. FIG. 5 shows an air-fuel ratio sensor indicating whether the air-fuel ratio is richer or leaner than a predetermined air-fuel ratio, which is also called an O ₂ sensor. FIG. 6 shows an air-fuel ratio sensor having a linear relationship between the air-fuel ratio and the output voltage, which is suitable for air-fuel ratio control during lean operation, but has a higher cost than the type shown in FIG.

In the following embodiments, an example in which an air-fuel ratio sensor of the type shown in FIG. 5 is mainly used will be described.

FIG. 4 shows an example of the set air-fuel ratio of the engine, which is divided into a lean region, a stoichiometric region, and a rich region according to the engine speed and the torque. In the stoichiometric region, the air-fuel ratio feedback control that repeats rich and lean over the air-fuel ratio 14.7 is performed as shown on the left side of FIG. It is possible to make a diagnosis.

However, if the rich region or the lean region continues for a long time, the air-fuel ratio sensor signal sticks to the rich side or the lean side, so that diagnosis of the air-fuel ratio sensor cannot be performed. As a result, the reliability of the diagnosis result of the exhaust system using the output of the air-fuel ratio sensor becomes low, and the air-fuel ratio sensor cannot be used effectively.

Therefore, it is effective to perform the diagnosis of the air-fuel ratio sensor by changing the air-fuel ratio to lean when the air-fuel ratio is rich and to change the air-fuel ratio to rich when the air-fuel ratio is lean as in the present application.

The specific logic is described below with reference to FIGS.
Will be described.

FIG. 7 shows a flowchart of the processing of the long-term rich judgment means 101 and the long-term lean judgment means 103.
The following processing is performed by a periodic interruption (for example, every 10 ms).

First, at block 701, the air-fuel ratio sensor 51
8 is read. At block 702, a lean / rich determination is made, that is, a predetermined air-fuel ratio, for example, A / F = 14.
7 Judge whether it is rich or lean. If it is determined that the flag is rich in the determination 703, the flag Frich is determined in a block 704.
(K) = 1. If it is not determined to be rich, Frich (k) is set to 0 in block 705, and a lean is recognized in the following processing.

Subsequently, in determinations 706 and 707, it is determined whether the operation is rich continuous or lean continuous, and in the case of continuous operation, the duration is counted up. It is determined whether or not Frich (k) = 1 in a determination 706, and when it is 1, that is, in the case of rich, it is further determined in a determination 707 whether or not Frich (k−1), that is, Frich one calculation cycle before is 1, and when it is 1, In step 709, the rich duration Trich is incremented by ΔT. Judgment 707
If Frich (k-1) = 0, the rich continuation time Trich (k) = 0 is cleared because rich continuous is not performed.
Passing through block 709 or block 710 is at least not a lean continuation, so block 71
At 3, the lean duration time Tlean (k) is cleared to 0.

On the other hand, in the determination of the continuation of the lean state, it is determined to be the lean state in the determination step 706, and if it is determined to be the lean state in the determination step 708, the lean continuation time Tlean (k) is determined in a block 711.
Is incremented by ΔT. If it is determined in block 708 that the air condition is rich, it is not lean continuation, and in block 712, Tlean (k) = 0 and the lean continuation time are cleared. Since the passage of the block 711 or 712 is not at least the rich continuation, the rich continuation time Trich (k) = 0 is cleared in block 714.

Next, in decision 715, the rich continuation time Tr
ich (k) is compared with a predetermined time T1, and if it has continued for T1 or more, a lean test flag Ltest =
1, the rich test flag Rtest = 0, and a lean test request is issued.

Also, in the determination 717, the lean continuation time Tle
An (k) is compared with a predetermined time T2, and if it continues for T2 or more, the rich test flag Rtest is determined in block 718.
= 1, lean test flag Ltest = 0, and issues a rich test request. If neither the determinations 715 nor 717 are satisfied, Rtest = 0 and Ltest = 0 are set in block 719, and no active test request is issued.

The above is the processing of the long-term rich judging means 101 and the long-term lean judging means 103. If there is a rich test request or a lean test request, the target air-fuel ratio changing means 102, 104 performs the target air-fuel ratio changing as post-processing. Set the fuel ratio to the test air-fuel ratio. Specifically, this is represented by the flowchart in FIG. 8, and first, in a determination 801, the lean test flag Ltest is determined. If there is a lean test request, the target air-fuel ratio KMRL = 14.7 + in block 803
Set to a side leaner than αL and stoichiometry. Judgment 8
02, the rich test flag Rtest is determined, and if there is a rich test request, the target air-fuel ratio K is determined at block 804.
MEL = 14.7-αR, which is set richer than stoichiometric. If neither the rich test request nor the lean test request is made, the normal control is performed.
The MRL is used as a map search value, and a map value that realizes the air-fuel ratio shown in FIG. 4 is used.

It is the actual air-fuel ratio changing means 105 that changes the actual air-fuel ratio from the above requirements.

When there is a command to change the air-fuel ratio from the actual air-fuel ratio changing means 105, the air-fuel ratio is changed by the following two means. 1
One is a fuel injection pulse width changing means 106, which reduces the pulse width when making it lean, and makes the pulse width larger when making it rich. The other is a throttle opening changing means 107. The opening is small when the air conditioner is rich, and is large when the air condition is lean.

FIG. 9 is a flowchart showing the processing of the fuel injection pulse width changing means 106.

First, at block 901, the target air-fuel ratio KMR
Read L. Next, at block 902, a TP is read. Here, TP is represented by TP = K × Qa / Ne (Equation 1), where Qa is an intake air amount measured by an air flow sensor, Ne is an engine speed, and K is a coefficient. TP represents the basic fuel injection amount injected per cylinder to make the air-fuel ratio stoichiometric. Next, in block 903, the fuel injection pulse width Ti is obtained by (Equation 2).

Ti = (14.7 / KMRL) × TP + Ts (Equation 2) Here, Ts is an invalid pulse width, and represents a delay time from energizing the injector to actually opening the valve. By obtaining Ti by adding Ts, the required injection amount can be injected without lack. In (Equation 2), the fuel injection pulse width Ti increases when the KMRL is small, that is, when the KMRL is set rich, and the fuel injection pulse width Ti decreases when the KMRL is large.

FIG. 10 is a flowchart showing the processing of the throttle opening changing means 107. First, at block 1001, the target air-fuel ratio KMRL is read. In block 1002, a reference TP is obtained from the map. here,
The reference TP has the same dimension as the TP described in the block 902, and is a TP for implementing stoichiometry at each operating point determined by the engine speed and the accelerator opening. That is, if the fuel injection pulse width Ti is calculated from the reference TP, and the intake air amount Qa is controlled by the throttle opening so that the TP becomes the target TP, the air-fuel ratio becomes stoichiometric.

After the reference TP is searched and found, block 1 is used.
In 003, a target TP is obtained by (Equation 3).

Target TP = (KMRL / 14.7) × Reference TP (Equation 3) The throttle opening is controlled so as to achieve the above-described target TP. At this time, the fuel injection pulse width is determined in block 1004 (Equation 4). ).

Ti = reference TP + Ts (Equation 4) The logic for changing the air-fuel ratio to the opposite air-fuel ratio across the stoichiometric ratio if the air-fuel ratio is continuously lean or rich has been described with reference to FIGS. The logic of the air-fuel ratio sensor diagnosis after the air-fuel ratio change will be described with reference to a flowchart in FIG.

First, a lean test flag Ltest = 1 is determined in block 1101. If a lean test is requested, the actual air-fuel ratio is supposed to be lean, so a determination 1103 checks whether the air-fuel ratio is rich or lean. Frich (k) = 0
If it is determined to be lean, block 1107 indicates “Lean NG”.
= 0, and the lean diagnosis is determined to be normal.

If it is determined in step 1103 that the air conditioner is rich, Td
If it is waiting for the time to become lean, but does not become lean even after Td, then at step 1108, LeanNG
= 1 and the lean diagnosis is determined to be abnormal.

At block 1102, the rich test flag R
It is determined that test = 1, and if a rich test is requested, the actual air-fuel ratio should be rich, so it is checked in determination 1104 whether the air-fuel ratio is rich or lean. If Frich (k) = 1 is determined to be rich, RichNG = 0 in block 1109,
The rich side diagnosis is determined to be normal.

If it is determined in step 1106 that the engine is lean, Td
If it is waiting for time to become rich, but does not become rich even after Td, RichNG is executed in block 1110.
= 1 and the rich side diagnosis is determined to be abnormal.

After performing the above-described rich-side diagnosis or lean-side diagnosis, the decision of 1111 and the decision of 1112 indicate that the lean N
If G = 1 or RichNG = 1 and either of the abnormality flags is on, block 1114 sets the air-fuel ratio sensor abnormality flag SensNG (k) = 1 and diagnoses that the sensor is abnormal. Determination 11 when both LeanNG and RichNG are 0
At 13, past SensNG (K−1) is determined, and if there is no abnormality determination, an air-fuel ratio sensor abnormality flag SensNG (k) = 0 is set at block 1115 to determine that the sensor is normal.

The movement of each parameter from the diagnosis of the air-fuel ratio sensor to the diagnosis of the air-fuel ratio sensor abnormality based on the logic of the flowcharts shown in FIGS.
15 to FIG.

FIG. 12 shows an example in which the lean side diagnosis is performed. At this time, the actual air-fuel ratio changing means 105 changes the air-fuel ratio by the fuel injection pulse width changing means 106.

In FIG. 12, the horizontal axis represents time, up to (a), a mode in which stoichiometric air-fuel ratio feedback is performed, rich operation up to (b), lean operation from (b) to (c). Where the air-fuel ratio is lean due to the test requirements of (C) to (d) show the rich operation, (d) to (e) show the lean test, and (e) show the stoichiometric.

More specifically, up to (a), the air-fuel ratio feedback control is performed by stoichiometric operation.
The sensor signal voltage repeatedly rises and falls over a predetermined value. Since (a) and (b) show the rich operation, A / F becomes rich to increase Ti ', and the sensor signal becomes H
i, and a rich signal is continuously output.

At time (b), since the rich continuous time has reached T1, a lean test request is issued, and the fuel injection pulse width T
Decrease i 'and make A / F lean. Then, since the air-fuel ratio sensor signal indicates lean, the diagnosis is determined to be normal, and T
The target air-fuel ratio is returned to rich by increasing i '. After this, if the sensor is normal, (a) to (c) are repeated.

The operation performed when the sensor is abnormal will be described with reference to FIG. Trich is 0 because the diagnosis was normal in (c).
Starts incrementing, and when (d) is reached, Tri
Since ch becomes T1, Ti 'is decreased to change the air-fuel ratio lean. At this time, the air-fuel ratio sensor is abnormal, so the sensor signal does not become Lo even if the time Td elapses after the engine is made lean (e) and the air-fuel ratio sensor abnormality flag Sens
The abnormality is determined as NG = 1.

FIG. 13 shows an example in which the rich-side diagnosis is performed. At this time, the actual air-fuel ratio changing means 105 changes the air-fuel ratio by the fuel injection pulse width changing means 106.

More specifically, up to (a), the air-fuel ratio feedback control is performed by stoichiometric operation.
The sensor signal voltage repeatedly rises and falls over a predetermined value. Since (a) and (b) are lean operations, the A / F is lean to reduce Ti ', and the sensor signal is L
It becomes o and the lean signal is continuously output.

At time (b), since the lean continuous time has reached T2, a lean test request is issued and the fuel injection pulse width T
Increase i / to make A / F rich. Then, the air-fuel ratio sensor signal indicates rich, so that the diagnosis is determined to be normal, and T
The target air-fuel ratio is returned to lean by reducing i ′. After this, if the sensor is normal, (a) to (c) are repeated.

The operation when the sensor is abnormal will be described from (c) onward. Tlean is 0 because the diagnosis was normal in (c).
Starts incrementing, and when (d) is reached, Tle again
Since an becomes T2, Ti 'is decreased to change the air-fuel ratio richly. At this point, the air-fuel ratio sensor is abnormal, so the sensor signal does not become Hi even after the elapse of the Td time since the air-fuel ratio sensor becomes rich (e) and the air-fuel ratio sensor abnormality flag Sens
The abnormality is determined as NG = 1.

FIG. 14 shows an example in which the lean side diagnosis is performed. At this time, the actual air-fuel ratio changing means 105 changes the air-fuel ratio by the throttle opening degree changing means 107.

More specifically, up to (a), the air-fuel ratio feedback control is performed by stoichiometric operation.
The sensor signal voltage repeatedly rises and falls over a predetermined value. Since (a) and (b) show the rich operation, A / F becomes rich to increase Ti ', and the sensor signal becomes H
i, and a rich signal is continuously output.

At time (b), since the rich continuous time reaches T1, a lean test request is issued and the throttle opening TV
A / F is made lean by increasing O '. Then, since the air-fuel ratio sensor signal indicates lean, it is determined to be normal by diagnosis,
Reduce the throttle opening to return the target air-fuel ratio to rich. After this, if the sensor is normal, (a) to (c) are repeated.

The operation when the sensor is abnormal will be described from (c) onward. Trich is 0 because the diagnosis was normal in (c).
Starts incrementing, and when (d) is reached, Tri
Since ch becomes T1, the throttle opening TVO 'is increased to change the air-fuel ratio lean. At this point, the air-fuel ratio sensor is abnormal, so even if the time Td elapses after the engine is made lean, the sensor signal does not become Lo and the air-fuel ratio sensor abnormality flag SensNG = 1 is determined at (e), and the abnormality is determined.

FIG. 15 shows an example in which the rich-side diagnosis is performed. At this time, the actual air-fuel ratio changing means 105 changes the air-fuel ratio by the throttle opening degree changing means 107.

More specifically, up to (a), the air-fuel ratio feedback control is performed by stoichiometric operation.
The sensor signal voltage repeatedly rises and falls over a predetermined value. Since (a) and (b) show the lean operation, the A / F becomes lean to increase the throttle opening, so that the sensor signal becomes Lo and the lean signal is continuously output.

At time (b), since the lean continuous time has reached T2, a rich test request is issued and the throttle opening TV
A / F is made rich by decreasing O '. Then, since the air-fuel ratio sensor signal becomes Hi and indicates rich, the diagnosis is determined to be normal, and the throttle opening is increased to return the target air-fuel ratio to lean. After this, if the sensor is normal, (a) to (c) are repeated.

The operation when the sensor is abnormal will be described from (c) onward. Tlean is 0 because the diagnosis was normal in (c).
Starts incrementing, and when (d) is reached, Tle again
Since an becomes T2, the throttle opening TVO 'is reduced to change the air-fuel ratio richly. At this time, the air-fuel ratio sensor is abnormal, so that the sensor signal does not become Hi even after the elapse of the Td time since the air-fuel ratio sensor becomes rich and the air-fuel ratio sensor abnormality flag SensNG = 1 is determined at (e), and the abnormality is determined.

As a countermeasure when the abnormality of the air-fuel ratio sensor is determined, the air-fuel ratio feedback control by the air-fuel ratio sensor is stopped, and the diagnosis of other subsystems using the output of the air-fuel ratio sensor is prohibited. It is effective.

The diagnosis using the air-fuel ratio sensor, such as the catalyst deterioration diagnosis, the secondary air supply system failure diagnosis, the EGR failure diagnosis or deterioration diagnosis, and the exhaust pipe leak diagnosis, are all applicable to the subsystem diagnosis. It is.

For example, as the catalyst deterioration diagnosis, the correlation between the pre-catalyst air-fuel ratio sensor and the post-catalyst air-fuel ratio sensor is obtained.
A method of diagnosing the degree of deterioration of the catalyst based on the correlation may be used.

As a fault diagnosis of the secondary air supply system,
Means for supplying a predetermined amount of secondary air at the time of diagnosis, means for clamping the engine air-fuel ratio to a target value, means for operating the engine fuel supply amount to slightly change the engine air-fuel ratio, and output of the air-fuel ratio sensor in the engine exhaust path And a means for calculating a secondary air supply amount from a fuel supply amount to diagnose a failure of the secondary air supply device.

The failure diagnosis or deterioration diagnosis of the EGR device includes a means for detecting an intake air amount, a means for detecting a recirculated exhaust gas temperature, a means for detecting an engine air-fuel ratio by an air-fuel ratio sensor provided in an exhaust path, A means for calculating an air-fuel ratio correction coefficient based on the information obtained by the detecting means and a means for detecting the intake air temperature diagnoses a failure or deterioration of the EGR.

Further, the leak diagnosis of the exhaust pipe includes operating state detecting means for detecting that the speed is relatively low and the load is low,
An air-fuel ratio feedback unit and a unit that determines whether or not a feedback correction coefficient α corresponding to oxygen absorbed by a leak is larger than a predetermined value perform a leak diagnosis of an exhaust pipe.

[0079]

In the engine control device, when the air-fuel ratio sensor detects either the rich side or the lean side air-fuel ratio state continuously for a predetermined time or more, the air-fuel ratio state opposite to the detected air-fuel ratio state is detected. Target air-fuel ratio changing means for changing the target air-fuel ratio so that the air-fuel ratio state is opposite to the detected air-fuel ratio state, and the target air-fuel ratio is changed. After that, when the air-fuel ratio sensor does not detect the opposite air-fuel ratio state within a predetermined time, the air-fuel ratio sensor includes an air-fuel ratio sensor abnormality determination unit that determines that the air-fuel ratio sensor is abnormal. The failure of itself can be diagnosed, and the effectiveness of air-fuel ratio feedback control and exhaust system subsystem diagnosis can be ensured.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing an embodiment of the present invention.

FIG. 2 shows an engine system according to an embodiment of the present invention.

FIG. 3 shows a configuration diagram of a control unit of FIG. 2;

FIG. 4 shows a setting example of an air-fuel ratio.

FIG. 5 shows an example of characteristics of an air-fuel ratio sensor.

FIG. 6 shows an example of characteristics of an air-fuel ratio sensor.

FIG. 7 shows a flowchart of software constituting one embodiment of the present invention.

FIG. 8 shows a flowchart of software constituting one embodiment of the present invention.

FIG. 9 shows a flowchart of software constituting one embodiment of the present invention.

FIG. 10 shows a flowchart of software constituting one embodiment of the present invention.

FIG. 11 shows a flowchart of software constituting one embodiment of the present invention.

FIG. 12 shows a time chart of a control example of the present invention.

FIG. 13 shows a time chart of a control example of the present invention.

FIG. 14 shows a time chart of a control example of the present invention.

FIG. 15 shows a time chart of a control example of the present invention.

[Explanation of symbols]

101 long-term rich judgment means, 102, 104 target air-fuel ratio changing means, 103 long-term lean judgment means, 105
Actual air-fuel ratio changing means, 106: fuel injection pulse width changing means, 107: throttle opening degree changing means, 108: air-fuel ratio sensor diagnosis means, 509: injector, 518 ... air-fuel ratio sensor.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/22 310 F02D 41/22 310K 45/00 368 45/00 368H F02M 25/07 550 F02M 25/07 550L

Claims (16)

[Claims] An air-fuel ratio sensor disposed in an exhaust pipe of an engine for detecting an air-fuel ratio of a combustion gas from a component of the exhaust gas, and according to an air-fuel ratio detected by the air-fuel ratio sensor to achieve a target air-fuel ratio. An air-fuel ratio feedback control means for operating the fuel injection amount by using an air-fuel ratio sensor, wherein when the air-fuel ratio sensor continuously detects one of the rich and lean air-fuel ratio states for a predetermined time or more, Target air-fuel ratio changing means for changing a target air-fuel ratio so as to be in an air-fuel ratio state opposite to the detected air-fuel ratio state; and after changing the target air-fuel ratio, changing the air-fuel ratio state to the air state within a predetermined time. An engine control device comprising: an air-fuel ratio sensor abnormality determination unit that determines that the air-fuel ratio sensor is abnormal when the fuel ratio sensor does not detect the abnormality. 2. An air-fuel ratio sensor disposed in an exhaust pipe of an engine for detecting an air-fuel ratio of combustion gas from a component of the exhaust gas, and according to an air-fuel ratio detected by the air-fuel ratio sensor to achieve a target air-fuel ratio. An air-fuel ratio feedback control means for operating the throttle opening by adjusting the air-fuel ratio sensor, when the air-fuel ratio sensor continuously detects one of the rich and lean air-fuel ratio states for a predetermined time or more, Throttle opening changing means for changing the throttle opening so that the air-fuel ratio state is opposite to the detected air-fuel ratio state; and changing the reverse air-fuel ratio state within a predetermined time after changing the target air-fuel ratio. An engine control device comprising: an air-fuel ratio sensor abnormality determination unit that determines that the air-fuel ratio sensor is abnormal when the fuel ratio sensor does not detect the abnormality. An air-fuel ratio sensor disposed in an exhaust pipe of the engine for detecting an air-fuel ratio of the combustion gas from a component of the exhaust gas; an input circuit for processing a detection signal of the air-fuel ratio sensor as an input signal; An engine control device comprising an injector for injecting fuel while the fuel injection is in progress and a pulse width calculating means for calculating an energization time to the injector to achieve a target air-fuel ratio, wherein an input value from the air-fuel ratio sensor is richer than a predetermined value A A long-term rich judging means for judging whether or not the state on the side has passed a predetermined time or more; and when the judging means judges that the rich state has passed a predetermined time or more, the air-fuel ratio becomes leaner than a predetermined value A. Target air-fuel ratio changing means for changing the target air-fuel ratio, real air-fuel ratio changing means for changing the actual air-fuel ratio to lean, Means for diagnosing an air-fuel ratio sensor abnormality if the output is not determined to be leaner than the predetermined value A. An air-fuel ratio sensor disposed in an exhaust pipe of the engine for detecting an air-fuel ratio of combustion gas from a component of the exhaust gas; an input circuit for processing a detection signal of the air-fuel ratio sensor as an input signal; An engine control device comprising an injector for injecting fuel while the engine is in operation, and a pulse width calculating means for calculating an energization time to the injector in order to achieve a target air-fuel ratio, wherein an input value from the air-fuel ratio sensor is leaner than a predetermined value A. A long-term lean determining means for determining whether the state on the side has passed for a predetermined time or more; and when the determining means determines that the lean state has passed for a predetermined time or more, the air-fuel ratio becomes richer than a predetermined value A. Target air-fuel ratio changing means for changing the target air-fuel ratio, real air-fuel ratio changing means for changing the actual air-fuel ratio richly, Means for diagnosing an air-fuel ratio sensor abnormality when the output is not determined to be richer than the predetermined value A. 5. An actual air-fuel ratio changing means according to claim 3, wherein the actual air-fuel ratio changing means increases the injection pulse width of the injector for injecting fuel when the fuel is rich, and conversely, for the injector for injecting fuel when the fuel is lean. An engine control device for reducing an injection pulse width. 6. The actual air-fuel ratio changing means according to claim 3, wherein the actual air-fuel ratio changing means controls the throttle valve to the closed side when the air-fuel ratio is rich, and controls the throttle valve to the open side when the air-fuel ratio is lean. An engine control device, characterized in that: 7. The engine control device according to claim 3, wherein when the air-fuel ratio sensor is determined to be abnormal, the air-fuel ratio feedback control by the air-fuel ratio sensor is stopped. 8. The engine control according to claim 3, wherein when an abnormality of the air-fuel ratio sensor is determined, diagnosis of another subsystem using an output of the air-fuel ratio sensor is prohibited. apparatus. 9. The engine control device according to claim 8, wherein the diagnosis of the subsystem is a catalyst deterioration diagnosis. 10. The catalyst deterioration diagnosis according to claim 9, wherein in the catalyst deterioration diagnosis, a correlation between an air-fuel ratio sensor before the catalyst and an air-fuel ratio sensor after the catalyst is obtained, and the degree of deterioration of the catalyst is diagnosed based on the correlation. An engine control device, characterized in that: 11. The engine control device according to claim 8, wherein the diagnosis of the subsystem is a failure diagnosis of a secondary air supply system. 12. The failure diagnosis of the secondary air supply system according to claim 11, wherein the failure diagnosis of the secondary air supply system is performed at a predetermined time when the diagnosis is performed.
Means for supplying the secondary air amount, means for clamping the engine air-fuel ratio to the target value, means for operating the engine fuel supply amount to slightly change the engine air-fuel ratio, and based on the air-fuel ratio sensor output and the fuel supply amount in the engine exhaust path An engine control device for diagnosing a failure of a secondary air supply device by means for calculating a secondary air supply amount. 13. The engine control device according to claim 8, wherein the diagnosis of the subsystem is a failure diagnosis or a deterioration diagnosis of an EGR device. 14. The failure diagnosis or deterioration diagnosis of the EGR device according to claim 13, wherein the means for detecting an intake air amount, the means for detecting a recirculated exhaust gas temperature, and an air-fuel ratio sensor disposed in an exhaust passage. A means for detecting an engine air-fuel ratio, a means for calculating an air-fuel ratio correction coefficient based on information obtained by the detecting means, and a means for detecting an intake air temperature diagnose a failure or deterioration of the EGR. An engine control device, characterized in that: 15. The engine control device according to claim 8, wherein the diagnosis of the subsystem is a leak diagnosis of an exhaust pipe. 16. The exhaust pipe leak diagnosis according to claim 15, wherein the exhaust pipe leak diagnosis includes operating state detecting means for detecting a relatively low speed and low load, air-fuel ratio feedback means, and oxygen sucked by the leak. Means for judging whether or not the feedback correction coefficient α is greater than a predetermined value corresponding to (i), to perform a leak diagnosis of the exhaust pipe.