JP2000291485A - Misfire detecting device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a misfire determing device for an engine, capable of quickly and accurately detecting the generating of a misfire of the engine. SOLUTION: This misfire determining device for an engine is provided with an air-fuel ratio sensor M1 for detecting the residual oxygen amount in exhaust gas to be discharged from the combustion chamber of the engine as an air-fuel ratio sensor output value, an exhaust gas temperature sensor M2 for detecting the exhaust gas temperature of exhaust gas as an exhaust gas temperature sensor output value, an air-fuel ratio sensor output misfire determining means M3 for judging the presence or absence of a misfire of the engine on the basis of the air-fuel ratio sensor output value from the air-fuel ratio sensor M1, an exhaust gas temperature sensor output misfire determining means M4 for judging the presence or absence of a misfire of the engine on the basis of the exhaust gas temperature sensor output value from the exhaust temperature sensor M2, and a misfire determing means M5 for determining that a misfire is generated on the engine, only in a case where the air-fuel ratio sensor output misfire determining means M3 and the exhaust gas temperature sensor output misfire determining means M4 determine the presence of a misfire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detecting device for detecting a misfire of an engine.

[0002]

2. Description of the Related Art When a misfire occurs in an engine, a large amount of unburned gas flows into an exhaust passage from a misfired cylinder, and there is a possibility that an exhaust gas purifying catalytic converter provided in the exhaust passage is deteriorated.

[0003] This is because the unburned gas flowing into the exhaust passage adheres to the catalytic converter and is burned by the heat of the catalytic converter, that is, the exhaust gas and the catalytic converter are brought to a temperature higher than usual by post-burning.

Therefore, in the event of a misfire in the engine, measures must be taken to protect the catalyst. For this reason, conventionally, various engine misfire detection devices for detecting engine misfire have been proposed.

For example, as disclosed in Japanese Patent Application Laid-Open No. 3-168350, a method of detecting an oxygen concentration in exhaust gas by an O ₂ sensor provided in an exhaust passage of an engine and detecting a misfire based on a change amount thereof. Has been proposed. This is based on the principle that when a large amount of unburned gas flows into the exhaust passage due to misfire, the oxygen concentration in the exhaust gas increases.

Further, as disclosed in Japanese Patent Application Laid-Open No. 2-112646, the crankshaft angular velocity of the engine is calculated,
There has been proposed a method of detecting misfire based on a change in crankshaft angular velocity that occurs when misfire occurs.

[0007]

However, in the former case, since the determination is made based only on the oxygen concentration in the exhaust gas, the deviation of the air-fuel ratio caused by a cause other than the misfire such as during transient operation is misfired. There is a risk of misunderstanding.
Further, in the case of the O ₂ sensor, only the ON / OFF output is performed when the air-fuel ratio passes the slice level. Therefore, it takes a certain detection period to obtain the change amount of the oxygen concentration based on the ON / OFF output. . Therefore, it has been difficult to quickly detect a misfire.

In the latter case, the change in the crankshaft angular velocity may cause erroneous determination of misfire due to a disturbance such as a reverse input from the axle. In addition, the detected value during a predetermined period is averaged to eliminate the disturbance. Need to ask. For this reason,
In the same way as the former, when quick and accurate misfire detection is required, the response is not sufficient, and the problem of further performance improvement remains.

In particular, in recent years, in a vehicle engine equipped with a turbo, a catalytic converter is provided at a position upstream of a turbo installation position in an exhaust passage, and is activated early at the time of a cold start to suppress emission of unburned gas. There is something. In this case, since the distance between the combustion chamber and the catalytic converter is short, if a misfire occurs, the catalytic converter is likely to be deteriorated. However, quick misfire detection is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine misfire determination device capable of detecting a misfire of an engine more quickly and accurately.

[0011]

According to a first aspect of the present invention, there is provided an engine misfire judging device according to the first aspect of the present invention, which is discharged from a combustion chamber of an engine as shown in FIG. Air-fuel ratio sensor M1 that detects the amount of residual oxygen in the exhaust gas as an air-fuel ratio sensor output value, an exhaust temperature sensor M2 that detects the exhaust gas temperature as an exhaust temperature sensor output value, and the air-fuel ratio sensor M1. Air-fuel ratio sensor output misfire determining means M3 for determining the presence or absence of misfire of the engine based on the output value of the fuel ratio sensor;
Exhaust temperature sensor output misfire determining means M for determining the presence or absence of a misfire of the engine based on the output value of the exhaust temperature sensor from the engine 2
And a misfire determining means M5 which determines that a misfire has occurred in the engine only when both the air-fuel ratio sensor output misfire determining means M3 and the exhaust temperature sensor output misfire determining means M4 determine that there is a misfire. It is characterized by having.

According to this, the determination of misfire of the engine is
The determination is made based on both the output value of the air-fuel ratio sensor and the output value of the exhaust temperature sensor, and it is determined that a misfire has occurred in the engine only when the results determined based on these two determination factors indicate that there is a misfire. You.

Therefore, it is possible to eliminate the influence of the disturbance which individually occurs on these two judgment factors, and it is possible to more accurately determine the misfire. For example, when a disturbance such as a deviation of the air-fuel ratio occurs in the transition period, the judgment based on the output value of the air-fuel ratio sensor may be influenced by the disturbance and may be erroneously determined to be a misfire. Since it is not affected by the judgment based on the value, it is not mistakenly judged that there is a misfire. Accordingly, since it is not determined that there is a misfire, it is determined that no misfire has occurred in the engine.
Therefore, the accuracy of misfire determination is further improved.

The output value of the air-fuel ratio sensor directly detects the amount of residual oxygen in the exhaust gas, and the output value of the exhaust gas temperature sensor directly detects the exhaust gas temperature of the exhaust gas.
Then, the residual oxygen amount in the exhaust gas and the exhaust gas temperature of the exhaust gas change immediately when a misfire occurs in the engine. Therefore, by performing the misfire determination based on both the output value of the air-fuel ratio sensor and the output value of the exhaust gas temperature sensor, it is possible to more quickly detect the misfire of the engine. Therefore, misfire of the engine can be detected quickly and accurately.

In the engine misfire detecting device according to the second aspect of the present invention, the air-fuel ratio sensor output misfire judging means M3 comprises:
Whether the air-fuel ratio sensor output value is an air-fuel ratio sensor output value indicating a residual oxygen amount equal to or less than a preset air-fuel ratio misfire determination value, or the air-fuel ratio sensor output value is a preset residual oxygen amount It is determined whether or not the above change is repeated at a predetermined cycle.

When the output value of the air-fuel ratio sensor is an air-fuel ratio sensor output value indicating a residual oxygen amount larger than the air-fuel ratio misfire determination value, or the air-fuel ratio sensor output value is equal to or greater than a preset residual oxygen amount. Is determined to be misfired when the fluctuations of are repeated at a predetermined cycle.

According to this, the misfire determination based on the air-fuel ratio sensor output value is performed based on both the detected air-fuel ratio sensor output value and its fluctuation pattern. Is done.

Therefore, for example, even when the detected air-fuel ratio sensor output value is smaller than the preset air-fuel ratio sensor output value misfire determination value (lean value), the variation pattern due to misfire Indicates that there is a misfire, it can be determined that there is a misfire. Therefore, a misfire determination can be made more quickly and accurately.

According to a third aspect of the present invention, there is provided an engine misfire detecting device, wherein the exhaust temperature sensor output misfire determining means indicates an exhaust temperature whose exhaust temperature sensor output value is higher than a preset exhaust temperature misfire determination value. Whether the output value is an exhaust temperature sensor output value, or whether an exhaust temperature sensor output increase rate indicating an increase amount of the exhaust temperature sensor output value during a predetermined time is larger than a preset exhaust temperature sensor increase rate misfire determination value Determine whether or not.

If the output value of the exhaust gas temperature sensor is an exhaust gas temperature sensor output value indicating an exhaust gas temperature higher than the exhaust gas temperature misfire judgment value, or the exhaust gas sensor output rise rate is smaller than the exhaust gas temperature sensor rise rate misfire decision value. It is characterized by determining that there is a misfire when the value is also large.

According to this, the misfire determination based on the output value of the exhaust gas temperature sensor is made based on the detected output value of the exhaust gas temperature sensor and its rate of increase.

Therefore, for example, even if the detected exhaust temperature sensor output value is smaller than the preset exhaust temperature sensor output value misfire determination value (low temperature), the rate of increase of the exhaust temperature sensor output value due to misfire is determined. Is large (the exhaust gas temperature rising speed is fast), it can be determined that there is a misfire. Therefore, a misfire determination can be made more quickly and reliably.

[0023]

Next, an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram conceptually showing an engine device provided with the misfire detection device of the present invention. The engine body 2 used in the engine device 1 is a horizontally opposed four-cylinder engine, and includes cylinder heads in both left and right banks of a cylinder block 3 (not shown). An intake port 5 and an exhaust port 6 are formed in the cylinder head, and an intake passage 10 is connected to the intake port 5.

The intake passage 10 is provided with an air cleaner box 11 and a compressor housing 1 of a turbo 12 from the upstream side.
2a, an intercooler 13, a throttle valve 14, and an intake pipe 15. The intake pipe 15 is provided with an injector 16 that performs fuel injection independently for each cylinder at a position immediately upstream of the intake port 5.

On the other hand, an exhaust passage 20 is connected to the exhaust port 6 and includes a pre-catalyst 21, a turbine housing 12b of the turbo 12, a waste gate valve 22, a front catalyst 23, and a rear catalyst 24 from the upstream side.

The engine body 2, the intake passage 10 and the exhaust passage 20 are provided with various sensors for detecting the operating state of the engine. Specifically, the engine body 2 is provided with a crank angle sensor 31 for detecting a rotation angle position of a crankshaft supported at a center position of the cylinder block 3 and a cam angle sensor 32 for detecting a rotation angle of a camshaft. ing.

The intake passage 10 is provided with an air flow meter 34 for measuring the amount of intake air at a position upstream of the compressor housing 12a, and a throttle opening sensor 35 for detecting a throttle opening near the throttle valve 14.
Is provided. An intake air temperature sensor 36 for detecting the temperature of the intake air is provided downstream of the throttle valve 14, and an intake pressure sensor 37 for detecting the intake pressure in the intake pipe 15 is provided for the intake pipe 15.

In the exhaust passage 20, an air-fuel ratio sensor 41 for detecting the amount of oxygen remaining in the exhaust gas at a position upstream of the pre-catalyst 21, and an exhaust gas for detecting the exhaust gas temperature at a position downstream of the pre-catalyst 21. A rear O ₂ sensor 43 for air-fuel ratio feedback control is provided downstream of the temperature sensor 42 and the front catalyst 22.

The control of the engine device 1 having the above configuration is performed by an electronic control unit (hereinafter simply referred to as “ECU”) 50.
It is performed by FIG. 3 is a schematic diagram illustrating the configuration of the ECU 50. The ECU 50 is mainly composed of a microcomputer, and a ROM 51, a RAM 52, a backup RAM 52a, a CPU 53, an input port 54, and an output port 55 are connected to each other via a bus line 56.

An A / D converter 57 which converts an analog signal received from various sensors into a digital signal and delivers it to the input port 54, and converts a control signal received from the output port 55 into a drive signal to convert various signals into various actuators And a drive circuit 58 for outputting the data to the internal circuit.

The input port 54 has a crank angle sensor 3
1. The cam angle sensor 32 is connected, and the air flow meter 34 and the air-fuel ratio sensor 4 are connected via the A / D converter 57.
1. A rear O ₂ sensor 43, an exhaust temperature sensor 42, and an intake air temperature sensor 36 are connected. The igniter 11 is connected to the output port 55, and the injector 16 and a warning lamp 26 provided on an instrument meter panel (not shown) are connected via a drive circuit 58.

The ROM 51 stores a control program and fixed data set in advance. The RAM 52 stores detection signals from various sensors and the like, and a backup RAM 52a.
Stores a learning value and the like. The CPU 53 uses the fixed data set in advance, detection signals from various sensors, and the like to perform R
The arithmetic processing is performed according to the control program stored in the OM 51 to perform fuel injection control, ignition timing control, and the like.
Judgment of misfire has been made.

That is, depending on the ECU 50 and the sensors and actuators connected to the ECU 50, each function of the air-fuel ratio sensor output misfire judging means, the exhaust gas temperature sensor output misfiring judging means, the misfire judging means, and others according to the present invention. Control function is realized.

Next, the processing relating to misfire determination executed by the ECU 40 will be described with reference to the flowchart of FIG. FIG. 4 is a flowchart showing a misfire determination routine. First, in step S1, the air-fuel ratio sensor output value ABF from the air-fuel ratio sensor (M1) 41 is read, and in step S2, the exhaust gas temperature sensor (M3)
The output value T of the exhaust gas temperature sensor from 42 is read.

In step S3, a misfire determination is made based on the air-fuel ratio sensor output value ABF. here,
If it is determined that there is a misfire, the process proceeds to step S4 to make a misfire determination based on other factors. If it is determined that there is no misfire, the process exits this routine (return). This part corresponds to the air-fuel ratio sensor output misfire determination means M2.

In step S4, the exhaust temperature sensor output value T
Is determined based on the misfire. Here, if it is determined that a misfire has occurred (YES), the process proceeds to step S5, and if it is determined that no misfire has occurred (NO),
Exit this routine (return). This portion corresponds to the exhaust temperature sensor output misfire determination means M4. The method of determining misfire in steps S3 and S4 will be described later.

In step S5, it is determined that a misfire has occurred in the engine. Misfire transmission processing such as turning on the warning lamp 26 and storing the fact of the misfire as trouble data in the backup RAM 52a of the ECU 50 is performed. Thereafter, the process exits the routine (return).

FIG. 5 is an explanatory diagram showing changes in the air-fuel ratio sensor output value ABF and the exhaust gas temperature sensor output value T before and after the occurrence of a misfire. The air-fuel ratio sensor output value ABF is shown in FIG.
As shown in (1), it changes abruptly to the lean side simultaneously with the occurrence of misfire, and further fluctuates periodically. This is because the oxygen in the unburned gas flowing into the exhaust passage 20 due to the misfire is detected by the air-fuel ratio sensor 4.
1 is for detection. Further, the reason for the periodic fluctuation is that a large amount of unburned gas is discharged only from the misfiring cylinder at that time, and the combustion stroke is sequentially performed for each cylinder.

As described above, the amount of residual oxygen in the exhaust gas is
Since a change occurs immediately upon occurrence of a misfire, misfire can be determined more quickly by using the air-fuel ratio sensor output value ABF of the air-fuel ratio sensor 41.

The output value T of the exhaust gas temperature sensor starts increasing at a predetermined speed at the same time as the occurrence of misfire, and becomes constant after the elapse of a predetermined time, as shown in FIG. . This is because unburned gas generated by the misfire flows into the exhaust passage, adheres to the precatalyst 21, and is burned by the heat of the precatalyst 21, so-called afterburning.

As described above, since the exhaust gas temperature changes immediately due to the occurrence of a misfire, the misfire can be determined more quickly by using the exhaust gas temperature sensor output value T of the exhaust gas temperature sensor 42. Therefore, it is possible to further reduce the misfire determination time for determining that a misfire has occurred in the engine. It should be noted that the fluctuations in the air-fuel ratio sensor output value ABF and the exhaust gas temperature sensor output value T in the figure are merely examples, and one example is conceptually shown.

Next, the misfire determination based on the change in the air-fuel ratio performed in step S3 will be described in detail. FIG. 6 is a flowchart showing a misfire determination processing routine based on the output value of the air-fuel ratio sensor.

First, in step S11, an average value (hereinafter referred to as an air-fuel ratio sensor output average value) ABFave of the air-fuel ratio sensor output value ABF in a predetermined period is calculated. In step S12, the air-fuel ratio sensor output value ABF in the predetermined period is calculated. Maximum value (hereinafter referred to as air-fuel ratio sensor output maximum value)
ABFdel between ABFMAX and a minimum value (hereinafter referred to as air-fuel ratio sensor output minimum value) ABFMIN (hereinafter referred to simply as air-fuel ratio sensor value fluctuation difference) ABFdel and air-fuel ratio sensor output maximum value A
An operation for obtaining the occurrence interval LT of BFMAX is performed.

The air-fuel ratio sensor value variation difference A obtained here
The BFdel and the generation interval LT are the air-fuel ratio sensor output values ABF
Is a factor for determining whether or not is periodically fluctuating indicating the occurrence of a misfire. Then, first, the air-fuel ratio sensor output average value AB
Step S1 to determine whether misfire has occurred by Fave
Proceed to 3.

In step S13, a comparison is made between a misfire determination value ABFmis (hereinafter referred to as an air-fuel ratio misfire determination value) for misfire determination based on the air-fuel ratio sensor output value ABF and an air-fuel ratio sensor output average value ABFave. By using the air-fuel ratio sensor output average value ABFave instead of the air-fuel ratio sensor output value ABF as the judgment factor, for example, the suddenly changed air-fuel ratio ABF is excluded, and more accurate judgment can be performed. The air-fuel ratio misfire determination value ABFmis
Is a value obtained by an experiment or the like, and R
It is set in advance in the OM 51.

Here, the air-fuel ratio sensor output average value ABFav
If e is greater than the air-fuel ratio misfire determination value ABFmis (lean value) (YES), the process proceeds to step S15. If the air-fuel ratio sensor output average value ABFave is a value (rich value) smaller than the air-fuel ratio misfire determination value ABFmis (NO), the process proceeds to step S14.

In step S14, it is determined whether or not the air-fuel ratio sensor output value ABF has a periodic variation indicating misfire (hereinafter referred to as misfire cycle variation). As a result, the air-fuel ratio sensor output average value ABFave becomes the misfire determination value A.
A misfire determination can be made even when BFmis is not exceeded, and a more accurate determination can be made.

Whether or not the air-fuel ratio sensor output value ABF has a misfire cycle fluctuation is determined by the air-fuel ratio sensor value fluctuation difference ABFde.
l and the occurrence interval LT, the air-fuel ratio sensor value variation difference ABFdel is equal to or greater than a preset air-fuel ratio variation difference misfire determination value ABFdelmis, and the occurrence interval LT is determined in advance. It is determined that it has occurred when it is shorter than the value LTmis. If there is a misfire cycle variation (YES), the process proceeds to step S15.

Then, at step S15, "there is a misfire"
Is determined, and the process exits from this routine (return).
If no misfire cycle variation has occurred in step S14 (NO), that is, if at least one of the air-fuel ratio variation difference ABFdel or the occurrence interval LT does not satisfy the condition, a misfire determination based on the air-fuel ratio sensor output value ABF is made. Then, it is determined that a misfire has not been detected, and the routine exits (return).

As described above, in the misfire determination based on the air-fuel ratio sensor output value ABF, the air-fuel ratio sensor output average value AB
Using Fave and the misfire cycle fluctuation, if either one of the above conditions is met, it is determined that a misfire has occurred. Therefore, they complement each other. For example, the air-fuel ratio sensor output average value ABFave is smaller than the air-fuel ratio misfire determination value ABFmis. Even if the value is a value on the rich side, if a misfire cycle variation of the air-fuel ratio sensor output value ABF is detected, it can be determined that a misfire has occurred. Therefore, a quicker and more reliable misfire determination can be made.

The determination based on the air-fuel ratio misfire determination value in step S13 mainly detects misfires that cause misfires every time, and the determination based on fluctuations in the misfire cycle in step S14 mainly determines random (intermittent) misfires. To detect.

Next, the misfire determination based on the exhaust gas temperature sensor output value T performed in step S4 shown in FIG. 4 will be described. FIG. 7 is a flowchart showing a misfire determination processing routine based on the exhaust temperature sensor output value T.

First, in step S21, the rate of increase (hereinafter, referred to as the rate of increase of the output value T of the exhaust gas temperature sensor per unit time)
An operation for obtaining ΔT (referred to as an exhaust gas sensor output increase rate) is performed. In step S22, the intake air amount Qa and the engine speed Ne are read as parameters for determining the current engine operation region.

In step S23, a misfire determination value ΔTmis (hereinafter referred to as a temperature increase rate misfire determination value) for determining misfire based on the exhaust gas temperature sensor output increase rate ΔT is set. The temperature rise rate misfire determination value ΔTmis is set according to the engine operation range. In the present embodiment, the temperature rise rate misfire determination values ΔTmisa, ΔTmisb, and ΔTmisc are set in each of the three engine operation areas. (ΔT
misa <ΔTmisb <ΔTmisc). FIG. 8 is a graph showing the relationship between the engine operating region and the temperature rise rate misfire determination value ΔTmis.

In step S24, a misfire determination value (hereinafter referred to as an exhaust gas temperature misfire determination value) Tmis for misfire determination based on the exhaust temperature sensor output value T is set. The exhaust temperature misfire determination value Tmis is set in accordance with the engine operation range. In the present embodiment, similarly to the temperature rise rate misfire determination value ΔTmis, the exhaust temperature misfire determination value Tmisa is assigned to each of the three engine operation regions. , Tmisb, and Tmisc are set (Tmisa <Tmisb <Tmisc). FIG. 9 is a graph showing the relationship between the engine operating region and the exhaust temperature misfire determination value Tmis.

First, the exhaust gas temperature sensor output increase rate ΔT
Then, the process proceeds to step S25 in order to make a misfire determination according to. In step S25, a comparison is made between the exhaust gas temperature sensor output increase rate ΔT obtained in step S21 and the temperature increase rate misfire determination value ΔTmis set in step S23.
Thus, a misfire determination is made based on the temperature rise rate ΔT.

When a misfire occurs in the engine, the output value T of the exhaust gas temperature sensor increases at a higher speed than that in the normal operation state, so that the output increase rate ΔT of the exhaust gas temperature sensor becomes large.
Therefore, when the exhaust gas temperature sensor output increase rate ΔT becomes larger than the temperature increase rate misfire determination value ΔTmis, it can be determined that misfire has occurred.

Since the exhaust gas temperature rise rate ΔT can be obtained instantaneously, the misfire determination can be detected more quickly. In addition, since the temperature rise rate misfire determination value ΔTmis is set in step S23 according to the engine operation region, it is possible to make a determination according to the occurrence state of misfire,
Accurate misfire determination can be made.

Here, if the exhaust gas temperature sensor output rise rate ΔT is smaller than the temperature rise rate misfire determination value ΔTmis (the exhaust gas rise rate is slow) (NO), the process proceeds to step S26.

In step S26, a comparison is made between the exhaust temperature sensor output value T and the exhaust temperature misfire determination value Tmis. Thus, a misfire determination is made based on the current exhaust gas temperature. Since the output value T of the exhaust gas temperature changes immediately due to the occurrence of a misfire, the use of this value enables quick and accurate misfire determination.

If the exhaust gas temperature sensor output rise rate ΔT is larger than the temperature rise rate misfire determination value ΔTmis (the exhaust gas rise rate is fast) in step S25 (YES), or in step S26, the exhaust temperature sensor output value T Is larger than the exhaust gas temperature misfire determination value Tmis (YES), the process proceeds to step S27.

In step S27, it is determined that there is a misfire, and the process exits from this routine (return). Also,
If the exhaust temperature sensor output value T is smaller than the exhaust temperature misfire determination value Tmis at step S26 (NO), the misfire determination based on the exhaust temperature sensor output value T indicates that a misfire could not be detected, and the process exits this routine ( return).

As described above, in the misfire determination based on the change in the exhaust gas temperature, the misfire is determined if any of the above conditions is satisfied, using the exhaust gas temperature sensor output increase rate ΔT and the exhaust gas temperature sensor output value T. Therefore, if the exhaust gas temperature sensor output increase rate ΔT indicating a sharp increase in the exhaust gas temperature is detected even when the exhaust gas temperature sensor output value T is low, misfire occurs in the engine. Can be determined to be.

On the contrary, the exhaust gas temperature sensor output increase rate ΔT
Is small, that is, even if the exhaust gas temperature sensor output value rises slowly, the engine is determined to have misfired if the exhaust gas temperature sensor output value T is larger than the exhaust gas temperature misfire determination value Tmis. be able to. Therefore, a quicker and more reliable misfire determination can be performed.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes can be made within the gist of the present invention. For example, in the above-described embodiment, the temperature rise rate misfire determination value ΔTmis and the exhaust gas temperature misfire determination value Tmis are set in accordance with the engine operation range. However, the present invention is not limited to this. You may set according to it.

[0066]

According to the invention described above, the determination of the occurrence of engine misfire is made based on both the output value of the air-fuel ratio sensor and the output value of the exhaust gas temperature sensor, and is determined based on these two determination factors. Only when the result indicates that there is a misfire, it is determined that a misfire has occurred in the engine.
It is possible to eliminate the influence of a disturbance which individually occurs in the three judgment elements, and it is possible to more accurately determine the occurrence of misfire.

The output value of the air-fuel ratio sensor directly detects the amount of residual oxygen in the exhaust gas, and the output value of the exhaust gas temperature sensor directly detects the exhaust gas temperature of the exhaust gas.
Since the amount of residual oxygen in the exhaust gas and the exhaust gas temperature of the exhaust gas change immediately when a misfire occurs in the engine, the occurrence of the misfire can be detected more quickly by making a determination using these.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is an overall configuration diagram conceptually showing an engine device provided with the misfire detection device of the present invention.

FIG. 3 is a schematic diagram illustrating the configuration of an ECU.

FIG. 4 is a flowchart showing a misfire determination routine.

FIG. 5 is a time chart showing changes in exhaust gas temperature and intake pressure before and after a misfire occurs.

FIG. 6 is a flowchart illustrating a misfire determination processing routine based on an air-fuel ratio sensor output value.

FIG. 7 is a flowchart showing a misfire determination processing routine based on an exhaust temperature sensor output value.

FIG. 8 is a graph showing a relationship between an engine operation region and a temperature rise rate misfire determination value.

FIG. 9 is a graph showing a relationship between an engine operation region and an exhaust gas temperature misfire determination value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine device 2 Engine main body 21 Precatalyst 31 Crank angle sensor 37 Intake pressure sensor 41 Air-fuel ratio sensor 42 Exhaust temperature sensor

Claims (3)

[Claims] 1. An air-fuel ratio sensor for detecting an amount of residual oxygen in exhaust gas discharged from a combustion chamber of an engine as an output value of an air-fuel ratio sensor, and an exhaust gas detecting an exhaust temperature of the exhaust gas as an output value of an exhaust temperature sensor. A temperature sensor, an air-fuel ratio sensor output misfire judging unit that judges the presence or absence of misfire of the engine based on an air-fuel ratio sensor output value from the air-fuel ratio sensor, and an exhaust gas temperature sensor output value from the exhaust gas temperature sensor. An exhaust temperature sensor output misfire judging means for judging the presence or absence of a misfire of the engine; and the engine is misfired only when both the air-fuel ratio sensor output misfire judging means and the exhaust temperature sensor output misfire judging means judges that there is a misfire. And a misfire determining means for determining that a misfire has occurred. 2. The air-fuel ratio sensor output misfire determination means, comprising: determining whether the air-fuel ratio sensor output value is an air-fuel ratio sensor output value indicating a residual oxygen amount equal to or less than a preset air-fuel ratio misfire determination value; Alternatively, it is determined whether or not the output value of the air-fuel ratio sensor is repeatedly changed at a predetermined cycle or more than the preset residual oxygen amount, and the output value of the air-fuel ratio sensor is larger than the air-fuel ratio misfire determination value. If the air-fuel ratio sensor output value indicating the oxygen amount,
2. The engine misfire detection device according to claim 1, wherein a misfire is determined if the output value of the air-fuel ratio sensor is repeatedly changed at a predetermined cycle or more than a preset residual oxygen amount. 3. The exhaust temperature sensor output misfire determination means, comprising: determining whether the exhaust temperature sensor output value is an exhaust temperature sensor output value indicating an exhaust temperature higher than a preset exhaust temperature misfire determination value; Alternatively, it is determined whether or not an exhaust temperature sensor output increase rate indicating an increase amount of the exhaust temperature sensor output value during a predetermined time is greater than a preset exhaust temperature sensor increase rate misfire determination value. When the output value is an exhaust temperature sensor output value indicating an exhaust temperature higher than the exhaust temperature misfire determination value,
3. The engine misfire detection device according to claim 1, wherein a misfire is determined when the exhaust gas temperature sensor output increase rate is greater than the exhaust gas temperature sensor increase rate misfire determination value. 4.