JP2000291486A - Misfire determining device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a misfire determining device for an engine, capable of quickly performing misfire determination having high reliability. SOLUTION: This misfire determining device for an engine is provided with an exhaust gas temperature detecting means M1 for detecting the exhaust gas temperature of exhaust gas discharged from a combustion chamber of the engine, an exhaust gas temperature comparing determining means M2 for determining whether the detected exhaust gas temperature is higher than an exhaust gas temperature misfire determining value preset for misfire determination, an intake pressure detecting means M3 provided on an intake pipe through which intake air to be sucked to a combustion chamber flows and for detecting intake pressure of intake air, an intake pressure comparing determining means M4 for judging whether the detected intake pressure is higher than an intake pressure misfire determining value to be set for misfire determination, and a misfire determining means M5 for determining that a misfire is generated on the engine, when the exhaust gas temperature is not less than the exhaust gas temperature misfire determining value and also the intake pressure is not less than the intake pressure misfire determining value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire judging device for judging whether an engine misfire has occurred.

[0002]

2. Description of the Related Art When a misfire occurs in an engine, unburned gas flows from a misfired cylinder into an exhaust passage, and there is a possibility that an exhaust gas purifying catalytic converter provided in the exhaust passage is deteriorated. Therefore, various types of engine misfire judging devices for judging whether or not a misfire has occurred in an engine have conventionally been proposed.

For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-109061, a method of detecting a suction negative pressure in an intake pipe of an engine and detecting a misfire based on a decrease in the suction negative pressure that occurs when a misfire occurs. Also, as disclosed in Japanese Patent Application Laid-Open No. 2-112646, a method has been proposed in which the angular velocity of a crankshaft is calculated and a misfire is detected based on a change in angular velocity that occurs when a misfire occurs.

However, in the case of misfire determination using the suction negative pressure in the intake pipe, there is a risk that a misfire may be erroneously recognized despite a normal combustion state due to pulsation occurring in a predetermined operation region. Further, in the case of misfire determination based on a change in the angular velocity of the crankshaft, there is a possibility that a misfire is erroneously recognized due to a disturbance such as a reverse input from a road surface or a drive system during deceleration.

[0005] For this reason, the present applicant has previously disclosed in
In Japanese Patent Application Laid-Open No. 77899, a misfire determination based on both a change in the angular speed of the crankshaft and a change in the intake pipe pressure prevents misfires caused by disturbances and the like, and improves the misfire determination accuracy and reliability. A judgment device is proposed.

[0006]

However, since the change in the angular speed of the crankshaft needs to be obtained by averaging the detection values during a predetermined period, it is not sufficient to cope with a case where a quick misfire determination is required. The problem of further performance improvement still remains.

In particular, in recent years, in a vehicle engine equipped with a turbo, a catalytic converter is provided at an upstream position of a turbo installation point 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. Even a quick misfire determination 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 performing a highly reliable misfire determination more quickly.

[0009]

According to a first aspect of the present invention, there is provided an engine misfire judging apparatus according to the first aspect of the present invention, which is discharged from a combustion chamber of an engine as shown in FIG. Temperature detection means M1 for detecting an exhaust gas temperature of the exhaust gas to be detected, and determining whether or not the detected exhaust gas temperature is higher than a preset exhaust gas temperature misfire determination value for misfire determination based on the exhaust gas temperature. Exhaust temperature comparison and determination means M2, intake pressure detection means M3 provided in an intake pipe through which intake air to be taken into the combustion chamber passes, and intake pressure detection means M3 for detecting the intake pressure of the intake air; Intake pressure comparison / judgment means M for judging whether or not it is larger than an intake pressure misfire determination value set for misfire determination
And a misfire determining means M5 for determining that a misfire has occurred in the engine when the exhaust temperature is equal to or greater than the exhaust temperature misfire determination value and the intake pressure is equal to or greater than the intake pressure misfire determination value. I do.

According to this, the misfire determination as to whether or not the engine is misfired is performed based on both the exhaust gas temperature and the intake pressure which are directly changed when the misfire occurs. A misfire can be quickly determined while maintaining a high level of accuracy and reliability.

An engine misfire judging device according to a second aspect of the present invention is characterized in that the intake pressure misfire judging value is set in accordance with the engine operating range. Thus, the intake pressure misfire determination value is set in accordance with the intake pressure that changes according to the engine operation range, so that the misfire determination based on the intake pressure can be performed with higher accuracy.

[0012]

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 has cylinder heads in both left and right banks of a cylinder block 3. An intake port 5 and an exhaust port 6 are formed in the cylinder head.
Is connected.

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 an 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.

In the intake passage 10, an air flow meter 34 for measuring the amount of intake air is provided 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 A / F 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 temperature of the exhaust gas 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 exhaust 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 configured by a microcomputer, and includes a ROM 51, a RAM 52, a CPU 53,
The input port 54 and the 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 A / F 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 panel (not shown) are connected via a drive circuit 58.

The ROM 51 stores control programs and preset fixed data, and the RAM 52 stores detection signals from various sensors, learning values, and the like. The CPU 53
Using fixed data set in advance, detection signals from various sensors, and the like, arithmetic processing is performed in accordance with a control program stored in the ROM 51, fuel injection control, ignition timing control, and the like are performed, and the presence or absence of misfire is determined.

That is, the ECU 50 and the sensors and actuators connected to the ECU 50 are used to determine the exhaust temperature detecting means, the exhaust temperature comparing and judging means, the intake pressure detecting means, the intake pressure comparing and judging means and the misfire judging means according to the present invention. Functions and other control functions are realized.

Next, a process related to misfire detection executed by the ECU 40 will be described with reference to a flowchart of FIG. FIG. 4 is a flowchart showing a misfire determination routine. First, in step S1, the exhaust gas temperature T is measured by the exhaust gas temperature sensor 42 as the exhaust gas temperature detecting means. In step S2, the intake pressure is detected by an intake pressure sensor serving as intake pressure detecting means, and the average value of the intake pressure for a predetermined time (hereinafter, referred to as "intake pressure average value").
Pmave is calculated. Through these steps S1 and S2, a misfire determination parameter for determining whether or not the engine has misfired is obtained.

In step S3, it is determined whether or not the exhaust gas temperature T detected in step S1 is higher than the exhaust gas temperature misfire determination value Tc. Thus, a misfire determination based on the exhaust gas temperature is performed. Exhaust gas temperature misfire judgment value Tc
Is an exhaust temperature preset in the ROM 51 of the ECU 50 for misfire determination, and is a threshold value for classifying the normal exhaust temperature and the exhaust temperature at the time of misfire occurrence. In this embodiment, the temperature is set to 950 ° C. This part corresponds to the exhaust gas temperature comparison and determination means.

In step S4, the intake pressure average value Pmave calculated in step S2 is used as the intake pressure misfire determination value Pc.
It is determined whether or not the value is larger than. Thus, misfire determination based on the intake pressure is performed. The intake pressure determination value Pc is a threshold that separates a normal intake pressure average value from an average intake pressure value at the time of misfire occurrence.
It is determined and set by referring to the data grid set in M51 using the engine speed and the engine load (Tp) (see FIG. 6). The intake pressure determination value Pc is set to a larger value as the engine speed and the engine load are lower, and is set to a lower value as the engine speed and the engine load are higher. The intake pressure is set to a high value when the engine load is low, and is set to a low value when the engine load is high.

FIG. 5 is a time chart showing changes in the exhaust gas temperature and the intake pressure before and after the occurrence of a misfire. In the figure, the intake pressure in the intake pipe 15 before the misfire occurs is set to the normal intake pressure P _A , and the intake pressure after the misfire is set to the misfire intake pressure P _B.
And then, also, misfire exhaust gas before the exhaust gas temperature of normal temperature T _A, and the exhaust temperature after misfire misfire temperature T _B.

When a misfire occurs, the intake pressure in the intake pipe 15 increases as shown in FIG.
Suddenly it increases from the normal state intake pressure average value P _A to misfire when the intake pressure P _B is higher than the intake pressure misfire determination value P _c, causing pulsation at elevated state.

The intake pressure is generated when air is sucked in within a certain unit time. If a misfire occurs, the engine speed decreases and the opening time of the intake valve becomes relatively long. The time for inhaling air inside is prolonged. Further, since the ventilation efficiency between the intake and exhaust in the cylinder is reduced, the amount of intake air of the corresponding cylinder which is drawn into the cylinder per unit time is reduced. For this reason, the intake pressure increases (approaches the atmospheric pressure).

Further, when the suction capacity of the misfiring cylinder is reduced, the intake balance with other cylinders is lost, and intake pulsation occurs. Therefore, the intake pressure average value Pm after the occurrence of a misfire
ave is a value higher than the intake pressure misfire determination value Pc.

Since the intake pressure sensor 37 directly detects such a change in intake pressure, misfire can be detected earlier from the change in intake pressure. Therefore, by monitoring the intake pressure in the intake pipe 15 with the intake pressure sensor 37, it is possible to quickly detect the occurrence of misfire.

Further, the exhaust gas temperature T, as shown in FIG. (A), gradually rises from the normal temperature T _A, from misfire occurs after a predetermined time has elapsed greater than the exhaust temperature misfire determination value T _C the misfire temperature T _B is the value. This is because unburned gas generated by misfire flows into the exhaust passage, adheres to the pre-catalyst 21, and abnormally burns due to heat of the pre-catalyst 21, so-called post-burning occurs.

Since the exhaust gas temperature sensor 42 directly detects such a change in the exhaust gas temperature, a misfire can be detected earlier from the change in the exhaust gas temperature. Therefore, by monitoring the rise of the exhaust gas temperature by the exhaust gas temperature sensor 42,
It is possible to detect the occurrence of a misfire more quickly than in the conventional misfire determination based on a change in rotation of the crankshaft angular velocity.

At step S3 shown in FIG.
Is higher than the exhaust gas temperature misfire determination value Tc (T> Tc) (YES), the process proceeds to step S4 to make a determination based on the intake pressure. In step S4, if the intake pressure average value Pmave is a value larger than the intake pressure misfire determination value Pc (Pmave> Pc) (YES), the process proceeds to step S5.

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

If the exhaust temperature T is equal to or less than the exhaust temperature misfire determination value Tc (T ≦ Tc) in step S3 (N
O) or, at step S4, the intake pressure average value Pmav
e is equal to or less than the intake pressure misfire determination value Pc (Pmave ≦ Pc)
If (NO), it is determined that no misfire has occurred, and the process exits from this routine (return).

As described above, since the misfire determination is performed based on both the exhaust gas temperature and the intake pressure, the accuracy and reliability of the misfire determination can be maintained at a higher level. In addition, since the determination is made based on the exhaust gas temperature and the intake pressure that enable earlier detection of misfire, the time for misfire determination can be further reduced.

When the ECU 50 determines that a misfire has occurred in the engine, the ECU 50 turns on a warning lamp and notifies the operator (driver) of the fact. When the operator performs an action such as stopping the engine, the pre-catalyst 21 is protected from misfire, and the turbine of the turbo 12 located downstream thereof is also protected.

[0038]

As described above, according to the engine misfire determination apparatus of the present invention, misfire is determined using both the exhaust gas temperature and the intake air pressure. Can be done quickly.

[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 map for calculating a pressure determination value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine apparatus 2 Engine main body 12 Turbo 21 Precatalyst 31 Crank angle sensor 37 Intake pressure sensor 42 Exhaust temperature sensor

Claims (2)

[Claims] An exhaust temperature detecting means for detecting an exhaust gas temperature of exhaust gas discharged from a combustion chamber of an engine, and an exhaust gas temperature misfire determination in which the detected exhaust gas temperature is preset for a misfire determination based on the exhaust gas temperature. Exhaust temperature comparison / judgment means for judging whether or not the temperature is higher than a value; and an intake pressure which is provided in an intake pipe through which intake air taken into the combustion chamber passes, and detects an intake pressure of the intake air. Detecting means; determining whether the detected intake pressure is greater than an intake pressure misfire determination value set for misfire determination based on intake pressure; and determining whether the exhaust gas temperature is equal to the exhaust gas temperature misfire. A misfire determination unit that determines that a misfire has occurred in the engine when the intake pressure is equal to or greater than a determination value and the intake pressure is equal to or greater than the intake pressure misfire determination value. Misfire identification device of. 2. The engine misfire determination device according to claim 1, wherein the intake pressure misfire determination value is set in accordance with an engine operation range.