JPH06249050A - Misfire detecting device of engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of the combustibility while reducing NOx as much as possible by controlling an NOx reducing means by a suppressing means in the direction to suppress reduction of NOx when the misfire of an engine is detected. CONSTITUTION:A control unit 15 makes a judgement that an engine has misfire when the output difference between a first and second O2 sensors 18,19 exceeds the specified set value. When a misfire is judged, a judgement is made whether the engine is in the lean-burn or not, and when the lean-burn is judged, a judgement is made whether or not the NOx amount generated when the air-fuel ratio A/F is made rich by the specified value exceeds the specified value. When the NOx amount does not exceed the specified value even when the air-fuel ratio A/F is made rich by the specified value, the air-fuel ratio A/F is corrected to the rich side by the specified value. Thus, deterioration of the combustibility can be prevented by correcting the air-fuel ratio to the rich side while reducing the NOx amount as much as possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire detection device, and more particularly to detecting engine misfire using O ₂ sensors provided upstream and downstream of a catalyst provided in an exhaust system. The present invention relates to an engine misfire detection device.

[0002]

2. Description of the Related Art Conventionally, in order to improve fuel efficiency, it has been performed to reduce pump loss and engine cooling loss by performing lean burn with a lean air-fuel ratio or increasing EGR amount. However, the lean air-fuel ratio and the increase in the EGR amount are accompanied by the deterioration of combustion such as the deterioration of the ignitability of the air-fuel mixture, which causes problems such as vibration due to torque fluctuations and an increase in HC emission.

Therefore, recently, there has been proposed a technique for solving such a problem by directly detecting the fluctuation of combustion which causes the torque fluctuation by an in-cylinder pressure sensor directly attached to the cylinder.

[0004]

However, in the case of using the in-cylinder pressure sensor, it is necessary to newly attach the in-cylinder pressure sensor itself to the cylinder, and the sensor mounting portion causes the shape of the combustion chamber to be distorted and knocking occurs. There is a possibility that the air-fuel mixture in the gap between the in-cylinder pressure sensor and the wall of the combustion chamber is less likely to burn, resulting in an increase in HC, and other problems.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and NO _x as much as possible.
It is an object of the present invention to provide an engine misfire detection device capable of preventing the deterioration of combustibility while reducing the fuel consumption.

[0006]

In order to achieve the above object, the present invention provides an O ₂ sensor provided on each of an upstream side and a downstream side of a catalyst provided in an exhaust system, and an NO _{2 for} reducing NO _{x. x} reduction means and determination means for determining that the engine has misfired when the difference between the output values of the O ₂ sensors respectively provided on the upstream side and the downstream side is a predetermined value or more. There is.

In the present invention thus constructed,
The determining means determines that the engine is misfiring when the difference between the output values of the O ₂ sensors provided on the upstream side and the downstream side of the catalyst is equal to or more than a predetermined value. Further, the present invention is characterized in that it further comprises a suppressing means for controlling the NO _x reducing means in a direction of suppressing the NO _x reduction when the determining means determines the engine misfire.

In the present invention thus constructed,
When determining a misfire of the engine by determining means, NO _x reducing means by suppressing means (means or the like to increase the means or EGR amount to the air-fuel ratio A / F to a lean) NO _x
It is controlled to suppress the reduction. As a result, it is possible to prevent deterioration of combustibility while reducing NO _x as much as possible.

Further, in the present invention, the engine may be a lean burn engine for setting the target air-fuel ratio to 17 or more, and the suppressing means may have a correcting means for correcting the air-fuel ratio in the rich direction. Further, in the present invention, the NO _x reduction means may be an EGR supply means that reduces NO _x by increasing EGR.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram showing an embodiment of an engine misfire detection device of the present invention. In FIG. 1, reference numeral 1 denotes an engine body, and an independent intake passage 2a is provided for each cylinder on the intake side of the engine body 1. These independent intake passages 2a are connected to an upstream intake passage 2c via a surge tank 2b. It is connected. An air cleaner 3 is connected to the upstream side intake passage 2c at its tip, an air flow meter 4 is provided at an upstream position near the connection with the air cleaner 3, and a downstream position is provided near the inlet of the surge tank 2b. A throttle valve 5 is arranged. An exhaust passage 6 is connected to the exhaust side of the engine body 1, and a catalyst 7 is arranged in the exhaust passage 6.

An injector 8 for fuel injection is arranged in the independent intake passage 2a of each cylinder. Furthermore, the downstream side of the throttle valve 5 in the upstream side intake passage 2c and the exhaust passage 6 are communicated with each other by an EGR passage 10.
An EGR valve 11 is provided in the passage 10. The EGR valve 11 is electromagnetic and adjusts the EGR amount according to the lift position of the valve body.

Reference numeral 15 denotes a control unit composed of a microcomputer or the like. The control unit 15 receives the intake air amount from the air flow meter 4, the crank angle signal from the crank angle sensor 16, and the engine water temperature signal from the water temperature sensor 17. Each is entered. Further, in the exhaust passage 6, a first O ₂ sensor 18 is arranged on the upstream side of the catalyst 7 and a second O ₂ sensor 19 is arranged on the downstream side thereof, and these first and second O ₂ sensors 18 are arranged. , 19
Is input to the control unit 15.

As will be described later, the control unit 15 determines the engine misfire as will be described later and, at the same time, reduces the NO _x as much as possible while preventing the deterioration of the combustibility, thereby changing the air-fuel ratio. A signal for making rich or reducing the EGR amount is output to the injector 8 or the EGR valve 11. Further, the control unit 15 outputs a deterioration determination signal for the O ₂ sensors 18 and 19.

Next, the misfire determination by the control unit 15 will be described. FIG. 2 is a diagram showing the relationship between the outputs of the O ₂ sensors 18 and 19 provided on the upstream and downstream sides and HC under the same air-fuel ratio (A / F). As shown in FIG. 2, when the engine misfires, the output value of the first O ₂ sensor 18 provided on the upstream side increases,
The output value of the second O ₂ sensor 19 provided on the downstream side does not increase and is substantially constant. Using this output characteristic, the control unit 15 determines that the engine has misfired when the output difference between the first and second O ₂ sensors 18 and 19 is equal to or greater than a predetermined set value.

In the embodiment of the present invention, when the misfire of the engine is detected, the air-fuel ratio is made rich or the EGR amount is increased to prevent the deterioration of the fuel property. ing. The details of this control will be described below. FIG. 3 is a diagram showing a relationship between the load and the EGR amount (or the air-fuel ratio A / F lean amount) used when performing such control. In FIG. 3, the first baseline is a line showing the relationship between the load and the EGR amount, and the second baseline is a line used when the O ₂ sensors 18 and 19 are deteriorated. It is set to a value smaller than the EGR amount set by the line by a predetermined amount. Further, the post-learning line, as described later, when the misfire is detected, the first and second O ₂ sensors 18, 1
The EGR amount is reduced until the output difference of 9 becomes equal to or less than a predetermined set value, and the learning amount at that time is shown. Further, this learning is carried out only in the medium load region near the road load and in the steady operation region of the engine, and in other regions apart from the road load, the learning value is reflected and set.

FIG. 4 is a flow chart showing the control contents executed by the control unit 15. In this flowchart, S indicates each step. First, in S1, it is determined whether the O ₂ sensor is deteriorated. If the O ₂ sensor has deteriorated, the routine proceeds to S2, where the target values of the EGR amount and the air-fuel ratio A / F lean amount are changed to the second baseline shown in FIG.

If the O ₂ sensor is not deteriorated, the routine proceeds to S3, where it is judged if the engine water temperature is 80 ° C., that is, if the engine is warmed up, and if the engine is warmed up. , S4, it is determined whether or not it is near the road. Furthermore, if it is near the road, S5
In step S6, it is determined whether or not the vehicle is in the steady operation. The operating state determined in S3 to S5 is the region where the engine is considered to be operating most stably. In S6, it is determined whether or not the output difference between the first and second O ₂ sensors 18 and 19 is greater than or equal to a predetermined set value in this operating region. Where the first
The case where the output difference between the second O ₂ sensors 18 and 19 is equal to or larger than the predetermined set value is a case where the engine is considered to have misfired, as shown in FIG.

When it is determined in S6 that the output difference between the first and second O ₂ sensors 18 and 19 is equal to or greater than a predetermined set value, that is, the engine has misfired, in S7, the engine is lean burn ( It is determined whether or not (lean combustion). If lean burn is not in progress, the process proceeds to S8 and the EGR amount is decreased by a predetermined value. After this, further S1 to S6
Each step of the first and second O ₂ sensors 1
If the output difference between 8 and 19 is still equal to or larger than the predetermined set value, the EGR amount is decreased again by the predetermined value in S8.
In this way, the first and second O ₂ sensors 18, 19
The EGR amount continues to be reduced until the output difference is less than a predetermined set value, that is, engine misfire can be prevented. In this way, when the decrease value of the EGR amount that can prevent engine misfire is finally set, the final decrease value of the EGR amount is learned, and after the learning of the EGR amount of FIG. The line is set.

Next, in S7, when it is determined that the engine is in lean burn (lean combustion), S9
Then, it is determined whether the NO _x amount generated when the air-fuel ratio A / F is made rich by a predetermined value exceeds a predetermined value (regulation value). If the NO _x amount exceeds the predetermined value by making rich, the process proceeds to S10 and the lean burn is stopped.
If the NO _x amount does not exceed the predetermined value even if the air-fuel ratio A / F is made rich by the predetermined value, the routine proceeds to S11, where the air-fuel ratio A / F
Is corrected to a rich side by a predetermined value. In this way, the combustion quality is prevented from deteriorating by correcting the air-fuel ratio A / F to the rich side by a predetermined value while reducing the NO _x amount as much as possible. Furthermore, in this case as well,
Similar to the decrease of the R amount, the correction value is learned by making the air-fuel ratio A / F rich by a predetermined value, and the post-learning line of the air-fuel ratio A / F lean amount of FIG. 3 is set.

Next, another embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a configuration diagram showing an engine and an exhaust system to which another embodiment of the present invention is applied, and FIG. 6 is a flowchart showing control contents according to another embodiment of the present invention. As shown in FIG. 5, reference numeral 20 denotes a V6 engine body, and this V6 engine body 20 has a first bank 21 having cylinders # 1 to 3 and a second bank 21 having cylinders # 4 to 6.
And a bank 22 of. Engine body 2
An exhaust passage 23 is connected to the exhaust side of 0. The exhaust passage 23 includes a branch exhaust passage 23 a connected to the first bank 21 and a branch exhaust passage 23 b connected to the second bank 22. These branch exhaust passages 23
Catalysts 24 and 25 are attached to a and 23b, respectively. Further, a first O ₂ sensor 26 is provided on the upstream side of the catalyst 24 in the branch exhaust passage 23 a connected to the first bank 21, and to the catalyst 25 in the branch exhaust passage 23 b connected to the second bank 22. On the upstream side, the second O ₂ sensor 2
In the exhaust passage 23 downstream of the catalysts 24 and 25, a third O ₂ sensor 28 is provided.

Also in this embodiment, the first and second control units (not shown) are provided in the same manner as in the above embodiment.
And the detection signals from the third O ₂ sensors 26, 27, 28 are input. The control unit determines a misfire of the engine on the basis of these input information, and at the same time, injects a signal for making the air-fuel ratio rich in order to prevent deterioration of combustibility while reducing NO _x as much as possible. Output).

Next, the control content of this embodiment will be described with reference to the flowchart of FIG. First, in S21, it is determined whether the output difference between the first O ₂ sensor and the third O ₂ sensor is a predetermined value or more. If the value is equal to or more than a predetermined value, the
Since it is considered that the cylinder of the bank No. has misfired, in order to prevent deterioration of the combustibility, the routine proceeds to S22, where the air-fuel ratio A / F of the first bank is made rich by a predetermined value. If it is less than the predetermined value, the process proceeds to S23, and similarly, it is determined whether the output difference between the second O ₂ sensor and the third O ₂ sensor is the predetermined value or more. If it is equal to or more than the predetermined value, it is considered that the cylinder of the second bank has misfired. Therefore, in order to prevent deterioration of combustibility, the process proceeds to S24, and the air-fuel ratio A / F of the second bank is set to the predetermined value Make it rich.

Next, when it is determined in S23 that it is less than the predetermined value, the process proceeds to S25, and the difference between the air-fuel ratio A / F of the first bank and the air-fuel ratio A / F of the second bank is determined. It is determined whether it is less than or equal to a predetermined value. If it is less than a predetermined value,
It is considered that the torque fluctuations in both banks are large. Therefore, in order to prevent a large torque fluctuation, the process proceeds to S26,
The air-fuel ratio of the bank whose air-fuel ratio A / F is lean is made rich by a predetermined value. As a result, it is possible to prevent a large torque fluctuation while preventing deterioration of combustibility.

Further, another embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 7, the exhaust passage 3
A catalyst 31 is arranged at 0, and secondary air is supplied to the catalyst 31 from an air supply port 31 formed at the center thereof. Further, in the exhaust passage 30, the first O ₂ sensor 33 on the upstream side of the catalyst 31, a second O ₂ sensor 34 is arranged on the downstream side, these first and second O ₂
Detection signals of the sensors 33 and 34 are input to a control unit (not shown).

In this way, when the secondary air is supplied to the catalyst 31, as shown in FIG. 8, the second O ₂ on the downstream side is supplied.
The output value of the sensor 34 changes to the characteristic shown in (A). Therefore, when the engine misfire is detected, the line (A) is used to perform the same control as in the above embodiment.

[0026]

As described above, according to the engine misfire detection device of the present invention, it is possible to prevent the deterioration of combustibility while reducing NO _x as much as possible.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an engine misfire detection device of the present invention.

FIG. 2 is a diagram showing the relationship between the output of an O ₂ sensor provided upstream and downstream and HC under the same air-fuel ratio (A / F).

FIG. 3 is a diagram showing a relationship between an EGR amount (or an air-fuel ratio A / F lean amount) and a load used when performing control according to an embodiment of the present invention.

FIG. 4 is a flowchart showing the control contents executed by an embodiment of the present invention.

FIG. 5 is a configuration diagram showing an engine and an exhaust system to which another embodiment of the present invention is applied.

FIG. 6 is a flowchart showing control contents according to another embodiment of the present invention.

FIG. 7 is a configuration diagram showing an exhaust system to which another embodiment of the present invention is applied.

FIG. 8 is a flowchart showing control contents according to another embodiment of the present invention.

[Explanation of symbols]

1 Engine Main Body 6 Exhaust Passage 7 Catalyst 8 Injector 10 EGR Passage 11 EGR Valve 15 Control Unit 18 First O ₂ Sensor 19 Second O ₂ Sensor 20 V6 Engine Main Body 21 First Bank 22 Second Bank 23 Exhaust Passage 24 catalyst 25 catalyst 26 first O ₂ sensor 27 second O ₂ sensor 28 third O ₂ sensor 30 exhaust passage 31 catalyst 32 air supply port 33 first O ₂ sensor 34 second O ₂ sensor

Claims (4)

[Claims] And 1. A O ₂ sensors provided respectively upstream and downstream of the catalyst provided in the exhaust system, the NO _x reduction means for performing NO _x reduction, respectively provided on the upstream and downstream A misfire detecting device for an engine, comprising: a determining unit that determines that the engine has misfired when the difference between the output values of the O ₂ sensors is a predetermined value or more. 2. The engine according to claim 1, further comprising suppression means for controlling the NO _x reduction means to suppress NO _x reduction when the determination means determines engine misfire. Misfire detection device. 3. The engine misfire detection according to claim 2, wherein the engine is a lean burn engine for setting a target air-fuel ratio to 17 or more, and the suppressing means has a correcting means for correcting the air-fuel ratio in the rich direction. apparatus. 4. The NO_xThe reduction means increases the EGR
NO by doing _xEGR supply means for reducing
The engine misfire detection device according to claim 2.